Future electrochemical energy storage materials: from nanoscience to device integration and real environment application

Resume : Electrolyte optimization is requested to improve next generation batteries in terms of performance, including cell cyclability, rate capability, safety, and lifespan. In this presentation we will present the strategic key points of ionic liquid based electrolytes production and R&I to achieve commercialization goals and meet the expectation of battery manufacturers: purity, process and scale-up, low production cost.

Resume : Ionic liquid (ILs) electrolytes based on imidazolium and tetra-alkyl-ammonium cations, coupled with bis(perfluroalkylsulfonyl) imide anions have been specifically tailored for lithium batteries operating up to ~5 V in the framework of the Si-Drive H2020 Project, obtaining satisfying ion transport and electrochemical properties. Here, we present the full characterization of their physical properties paying attention to the effect of temperature and lithium salt incorporation, as well as to the nature of the cation. The thermal stability is studied by means of themomogravimetry showing that the liquids with the bis(fluorosulfonyl)imide (FSI) anion decompose at temperatures lower than those based on the bis(trifluoromethylsulfonyl)imide (TFSI). Moreover, their vapor pressures are measured by isothermal heating. Infrared spectroscopy exploiting both MIR and FIR frequency range, coupled with DFT calculation, is used to obtain information about the interactions between anion and cation and the possible occurrence of conformational disorder. Indeed, all the properties of ILs are the consequence of competitive microscopic interaction forces; therefore, the knowledge of the microscopic properties and of the intermolecular forces is fundamental to allow the design of ILs with specific macroscopic properties. The reported results, besides showing that the properties of the proposed liquids are well suitable for their use as electrolytes, provide insights into the close relation between intermolecular interactions and conformational disorder. In particular the data obtained for two ILs having ethoxy containing tetra-alkyl-ammonium cations highlight the importance of the interplay between conformational disorder and acidity/polarization of the possible hydrogen bonds behind the determination of the macroscopic properties of the ILs.

Resume : Ionic liquids have been proposed to constitute electrolyte solutions that improve the performance of Li-ion batteries, due to their particular properties, especially conductivity. In this work, classical molecular dynamics simulations were used to study the structural and dynamic properties of electrolyte solutions, based on ionic liquids and with different amounts of lithium. Pyrrolidinium cations with small linear chains 1-methyl-1-ethyl pyrrolidinium (Pyr12) and 1-butyl-1-butyl pyrrolidinium (Pyr14) were combined with anions hexafluorophosphate (PF6) and tetrafluoroborate (BF4) to build the pure ionic liquid models, while a fraction of the pyrrolidinium cations were replaced (1:1 proportion) by lithium (Li) cations to form the electrolyte solutions with different fractions of lithium. OPLS-based forcefield parameters as implemented in Gromacs software were used to model the intramolecular and intermolecular interactions of all the species, and all the properties were obtained from a 20 ns production phase with NPT ensemble at 400 K temperature and 1 bar pressure. Our results show that the density of systems with PF6 anions is larger than that of the systems with BF4, for all fractions of lithium. Also, for the four ionic liquids considered, the density decreased almost linearly with the increasing amount of lithium, except for the Li-anion systems (i.e., without pyrrolidinium). We have obtained interesting trends also for the behavior of the pair correlation function (g(r)) analyzes and for the cation and anion self-diffusion. Our results show that for systems without lithium, the cations diffuse differently in each ionic liquid, although the systems with the same anion have closer values of cation self-diffusion. Anion self-diffusion depends on the anion species. Lithium diffusion is larger in Pyr12-anion systems, with a 0.25 lithium fraction, and BF4 anions. It is important to point out that the lithium diffusion in the ionic liquid is smaller than the diffusion of other ionic species, as reported in the literature. Our results are of interest for the engineering of new ionic liquid based electrolytes for the batteries of the next generation. This research was developed under the framework of the BAT4EVER project (www.bat4ever.eu) that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 957225.

Resume : Li-ion batteries have reached great importance in the last decades as power sources of portable devices such as cell phones, laptop computers and others. However, some safety problems like electrolyte leakage or fire, that constitute a bottleneck for future applications, have been reported from these types of batteries. Most of these problems come from the use of a highly flammable liquid electrolyte. An ideal solution would be to use a solid polymer electrolyte (SPE), which is solvent free and non-flammable. But SPEs exhibit low ionic conductivity and large interfacial resistance at room temperature (RT). To combine good properties of liquid and polymer electrolytes, the gel polymer electrolyte (GPE) concept has been introduced. GPEs display high ionic conductivity and good interfacial contact at RT. In addition, in-situ polymerization presents an easy assembly process compatible with the conventional Li-ion fabrication equipment In this work, we report on a GPE based on poly (ethylene glycol diacrylate) (PEGDA) as polymer matrix coupled with a liquid phase, mostly composed of a non-flammable solvent. The mechanical properties can be tuned by changing the polymer-to-liquid weight ratio. Good results in terms of ionic conductivity, electrochemical stability and safety suggest it is suitable for Li-ion batteries. As a confirmation, NMC and graphite electrode with high loading were used to prepare 100 mAh pouch cells. After studying polymer distribution in the electrode, electrochemical testing revealed a very good capacity retention (>80% after 350 cycles).

Resume : Ionic liquids (ILs) are attractive candidates as electrolytes for Li-ion batteries (LIBs) due to their high ionic conductivity, wide electrochemical potential window, and nonflammability. For further development of the LIBs using ILs, it is critical to design the interface of ILs and positive electrodes with electrochemically robust and low resistance. However, the mechanism of Li-ion transport at the interface is not well known. Therefore, in this study, we investigated the interface resistance quantitatively by utilizing a LiCoO2(001) epitaxial thin film as a positive electrode and tetraglyme-lithium bis(trifluoromethanesulfonyl)imide equimolar complex, [LiG4][TFSA], as IL electrolyte. For the characterization of battery performance, a three-electrode type battery cell was prepared, consisting of the LiCoO2(001) film and Li foils as working and reference/counter electrodes. The three electrodes were immersed into [LiG4][TFSA] ionic liquid. Cyclic voltammetry (CV) was performed to test battery operation. Electrochemical impedance spectroscopy was used to evaluate the interface resistance. In CV curves, oxidation and reduction reaction current peaks are observed at 3.93 and 3.86 V vs. Li/Li in the first CV cycle. After the first CV cycle, the interface resistance at [LiG4][TFSA] LiCoO2(001) is 268 Ωcm2. However, as CV cycles increase, the difference between the oxidative and reduction current peaks is enlarged, meaning the deteriorated battery performance. This result originates from the increase in the interface resistance, which is 82 times greater (21,780 Ωcm2) after ten CV cycles than after the first CV cycle. In contrast, we succeeded in stable battery performance by introducing a Li3PO4 film with a thickness of 20 nm at the [LiG4][TFSA]–LiCoO2(001) interface. As a result, introducing the Li3PO4 film leads to overlapping CV curves even after ten cycles. In addition, no significant increase in the interface resistance is confirmed after the CV cycling. The results highlight the importance of the interfacial modification at IL and positive electrode to improve battery performance.

Resume : The energetic transition is raising countless applications that require electrochemical energy storage solutions. Batteries and supercapacitors are the main players, being used in distinct applications since their metrics are quite different. Batteries provide high energy density, while supercapacitors are excellent to manage high power demand and short time of responses. Despite the importance of these devices there is still a gap, concerning applications that may require metrics that do not match well with the response of batteries or conventional supercapacitors. In this frame, asymmetric supercapacitors (and ultra batteries) combining a battery type electrode and a supercapacitive carbon electrode have been reported. However, they still suffer of modest energy density and important capacity fade under cycling. Thus, despite important advances there are still many open challenges to better tailor the metrics of these devices and to ensure enhanced performance in practical applications. The development of new electrode material compositions, combining pseudocapacitive (fast redox redox) materials and carbon based materials in the same electrode, appears as a very promising strategy to enhance energy density and to keep high power rate. This is particularly attractive to develop new supercapacitor devices capable of storing higher energy density at high power density. This talk overviews recent advances on the development of composite materials, combining both carbon based materials and redox metal compounds to enhance the capacitance of the electrodes in aqueous and environmentally friendly electrolytes. The main target is to create compositions that can tailor the electrodes metrics, creating fit for the purpose devices, capable of delivering higher energy density at high power. Aknowledgments: The author acknowledges Funding drom Fundação para a Ciência e Tecnologia (FCT) for the projects: CQE - UIDB/00100/2020, UIDP/00100/2020, LA/P/0056/2020 and PTDC/QUI-ELT/2075/2020

Resume : The improvement of the performances of Lithium-Ion Batteries (LIBs) is one of the hot topics for energy storage. LIBs are, currently, the state-of-art energy storage systems in terms of energy density, duration and efficiency(1). To pursue a wider market penetration of hybrid or all-electric vehicles, innovations are needed in the battery formulations regarding all the active components: positive and negative electrodes as well as electrolytes. The aim of the Si-DRIVE projectis to develop a new generation LIB using a Silicon negative electrode, an ionic liquid-based (IL) electrolyte and a Cobalt free Lithium Rich Oxide positive electrode. In this work, we analysed the morphology and the composition of the solid electrolyte interphase (SEI) layer precipitated on the carbon free self-standing amorphous Silicon (a-Si) electrodes during galvanostatic cycling in an electrochemical cell. Various experimental techniques, such as Attenuated Total Reflectance (ATR), Raman, Optical Photothermal IR Spectroscopy (OPTIR) and Scanning Electron Microscopy (SEM) were employed. We used either a lithium bis(fluorosulphonyl) imide/ethyl methyl imidazolium bis(fluorosulphonyl) imide or a lithium bis(trifluoromethyl sulphonyl) imide/ethyl methyl imidazolium bis(fluorosulphonyl) imide based electrolyte. The use of this ionic liquid as solvent discloses a unique combination of promising electrochemical performance and enhanced safety. The aim of this study is to verify the impact of this innovative electrolyte on the chemical nature and morphological properties of the SEI layer over the high-capacity silicon electrode. This Project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 814464. (1) M. Stanley Whittingham, Chem. Rev. 2014, 114 (23), 11413

Resume : Ionogels, in which an ionic liquid (IL) is confined within a silica matrix, are attractive hybrid solid electrolytes for lithium ion batteries (LIBs) because of their sufficiently high ionic conductivity, high thermal stability, and broad electrochemical stability window. However, several other properties remain to be improved. Ionic liquids are often considered to be expensive, which warrants investigation into more cost-effective alternatives. In addition, the pure silica matrix imparts a brittle nature to some ionogels, which may lead to loss of contact with the electrodes during battery cycling, and premature breakdown. Furthermore, lithium prices are currently rising very fast, due to an imbalance in supply and demand. This could eventually reverse the steady price drops which Li ion batteries have shown until now, and which are mandatory for the large scale breakthrough of electric vehicles on a large scale. In our group, we have investigated routes to tackle precisely these challenges. Research was done into deep eutectic solvents (DES) to replace ionic liquids both for LIBs and Na ion batteries (SIBs). The new class of hybrid solid electrolytes obtained with DES, are the so-called eutectogels (ETG) for LIBs. Na is much more abundant than Li and so, SIBs (sodium ion batteries) can be interesting alternatives to LIBs. It has been shown that SIB full cells with DES electrolyte have enormously enhanced the cycle life compared to cells containing conventional electrolyte. To enhance the mechanical properties of the material obtained with a pure silica matrix, two routes were developed. First of all, the silica matrix was replaced by a polymer matrix. This yielded a class of materials named polymer eutectogels (pETG). The first generation of the pETGs was found to be adequate for LIBs with LiFePO4 cathode, while a second generation was needed for NMC (Li(Ni,Mn,Co)O2) cathodes. Particularly in the last case, detailed studies of the interface between the electrolyte and electrode have shown a high stability. Alternatively, also the organic modification of the silica matrix has been investigated. Here, the focus lies on improving the mechanical properties and its effects on the battery operation stability, whilst maintaining the mostly inorganic nature of the matrix material. In conclusion, a summary of the group?s research progress regarding ionogels and eutectogels will be presented, outlining both the advantages and challenges of these interesting new materials. Partly published in: - Deep Eutectic Solvents as Nonflammable Electrolytes for Durable Sodium-Ion Batteries, D. De Sloovere et al., Adv. Energy and Sustainability Res., 2022, https://doi.org/10.1002/aesr.202100159 - Polymeric Backbone Eutectogels as a New Generation of Hybrid Solid-State Electrolytes, B. Joos et al., Chem. Mater., 32 (9) 2020 3783-3793 - Eutectogels: A New Class of Solid Composite Electrolytes for Li/Li-Ion Batteries, B. Joos et al. Chem. Mater. 30 (3) 2018 655-662

Resume : The continuous emissions of greenhouse gases is one of the major environmental issues the world faces today. Wind power and solar energy are promising alternatives to fossil fuels in our aim to decarbonise global energy generation. However, with the increase in renewable generation comes a pressing need for effective energy storage. With the drastic fall in lithium ion battery cost in recent years, they have found a market in stationary storage applications, even though they are not particularly well suited to medium-to-large-scale grid storage (10 s of MWh), due to lifetime and cost issues. The technology with perhaps the greatest potential for safe and effective medium-long term storage is the Redox Flow Battery (RFB). RFBs offer long lifespan, high reliability and independent tuneable power and energy. A typical RFB consists of two electrolyte tanks from which the electrolytes with the electroactive species dissolved are circulated by pumping through two carbon electrodes. The role of the electrode is to provide active sites for the redox reactions and facilitate mass transport and charge transfer. Because of this, the performance of the RFB is highly dependent on the porous microstructure of the electrodes. Commercial electrodes usually consist of fibre carbon mats in the form of felts or papers. Although their use is widespread, these materials suffer from poor wettability and high-pressure drop. Here we present our work on alternative carbon electrode materials derived from lignin that has been processed in the form of freestanding fibre mats using electrospinning, a versatile technique that enables the fine control of the properties of the obtained materials including the tuning of the surface chemistry, conductivity, porosity and thickness, key parameters when designing electrodes.

Resume : Solid boosters are an emerging concept for improving the performance and especially the energy storage density of the redox flow batteries but information about electron transfer (ET) reactions between the redox active solid and the redox electrolyte in the tank are missing, scarce or scattered in the literature. So far, we have formulated how these systems work from the point of view of thermodynamics. We described possible pathways for charge transfer, estimated the overpotentials required for these reactions in realistic conditions, and illustrated the range of energy storage densities achievable considering different redox electrolyte concentrations, solid volume fractions and solid charge storage densities[1]. As the next step, we study the ET reactions in solid boosted flow batteries employing scanning electrochemical microscopy (SECM). SECM, with a micrometer scale spatial and millisecond scale temporal resolution, is able to track the local ET between the redox electrolyte and the redox solid. In the SECM set-up, active solid material is drop-casted on a glass that is immersed in the redox electrolyte similar to our system for studying oxygen absorption in electrocatalyst layers [2]. When the biased tip approaches the substrate, the reduced electrolyte species generated at the tip are oxidized by the substrate and recirculate to the tip, leading to a positive feedback. The biased tip being located in different distances from the substrate will oxidize and reduce the active solid material and the obtained current-time behavior provides information about kinetics of ET reactions. Employing SECM in solid boosted flow batteries provides valuable information on the kinetics of these systems and this knowledge improves the system’s operation. References [1] M. Moghaddam, S. Sepp, C. Wiberg, A. Bertei, A. Rucci, P. Peljo, Molecules 2021, 26, 1–19. [2] M. Moghaddam, P. Peljo, ChemElectroChem 2021, DOI 10.1002/celc.202100702.

Resume : Redox flow batteries (RFBs) are considered as one of the most promising large-scale energy storage technologies, significantly for the integration with renewable energies. However, so far, none of the RFB systems has significantly deployed to the marketplace due to several limitations such as low energy density, poor electrochemical performance, high cost. Among the various alternative RFB chemistries, zinc-iodide aqueous RFB (ZIFB) hold great promise for next-generation FBs applications due to their appealing features of cost-effectiveness, high safety, and high energy density. However, the performance of ZIFB is hindered by multiple critical challenges such as poor cyclability, capacity fading as a result of irreversible zinc plating and stripping, slow kinetics of the redox reactions. The electrolyte has a major contribution in scaling up the battery performance. In this work, we proposed an improved electrolyte design by introducing a low cost salt, NaCl, as an additive to enhance the electrochemical performance and cyclability of ZIFB. The half-cell electrochemical performance shows improved reversibility and kinetics of redox reactions which, further reflects in the promising cell cycling performances of high discharge capacity and excellent capacity retention. Such improvements are mainly attributed to the multifunctional roles of this cost-effective salt in the both sides redox reactions starting from the efficient Zn dissolution by the formation of soluble ZnClx complex on the surface of the anode, and freeing up the I- ions by I2Cl- formation. This encouraging results indicate that addition of a cost-effective salt, NaCl, enlighten a great prospect for high performance yet cost-competitive ZIFB applications. The work was funded by MICINN under CERES (PID2020-116093RB-C42) project. M. Chakraborty received PhD grant from the EU Horizon 2020 research and innovation programme (DOC FAM COFUND 2016) under the Marie Skłodowska-Curie grant agreement No 754397. Keywords: Aqueous Zn-iodide flow batteries, Supporting electrolyte, Redox reversibility, Zn deposition/dissolution, Cycle life.

Resume : Redox flow batteries are among preferential systems for stationary energy storage, which is taking more and more importance with the growing share of renewable energy generation. Since 2013, research around redox flow batteries tends to diversify towards organic systems. Active molecules utilized in such aqueous organic batteries (quinones, viologens, TEMPO etc.) show potential advantages over vanadium, namely ability to be operated in neutral or basic media, low cost and no criticity, while being harmless for human and the environment. However, stability and durability issues because of chemical or electrochemical degradations still hinder their massive development. Our work focuses on understanding and modelling aqueous organic flow batteries aging mechanisms, and how they affect battery’s performances (energy fade, coulombic or energy efficiency loss). In such batteries, electrolytes degradations are usually a main concern compared to membrane issues or electrodes corrosion. Degradations are studied via a combined modelling/experimental approach, using a well described in the literature 2,6-DHAQ/Fe(CN)6 cell system as reference [1,2]. 0D multiphysics model has been developed because this modelling scale enables long-time scale simulations, while still being able to describe the physical reality of a redox flow cell. The base model considers electrochemical main reactions as well as water splitting reactions, mass transport through membrane and electrodes, liquid electrolyte transport and pressure losses, and an electric part in electrodes, electrolyte, and membrane [3]. Chemical degradations, electrochemical degradations towards inactive species, and electrochemical degradations forming new redox couples, corresponding to frequently encountered degradations, were added to the model. Calibration and validation of the model is done with the help of dedicated cycling aging experiments at different current densities, temperatures, and voltage limits, both in symmetric cells (to suppress crossover) and in full cells. Post-aging samples are characterized by cyclic voltammetry, 1H and 13C NMR and HPLC-MS, to help identify and quantify degradations. This model is used to gain insights into how aging impacts long term behaviour of flow batteries using organic electroactive species. Understanding degradations mechanisms and how operating parameters influence them is essential for improving operating conditions, thus increasing global lifetime of the system. Furthermore, since degradations described in the model are frequently encountered in aqueous organic flow batteries, this work can be easily extended to similar electroactive organic species. References [1] M.-A. Goulet, L. Tong, D.A. Pollack, D.P. Tabor, S.A. Odom, A. Aspuru-Guzik, E.E. Kwan, R.G. Gordon, M.J. Aziz, Journal of the American Chemical Society (2019). https://doi.org/10.1021/jacs.8b13295. [2] K. Lin, Q. Chen, M.R. Gerhardt, L. Tong, S.B. Kim, L. Eisenach, A.W. Valle, D. Hardee, R.G. Gordon, M.J. Aziz, M.P. Marshak, Science 349 (2015) 1529–1532. https://doi.org/10.1126/science.aab3033. [3] Q. Cacciuttolo, M. Petit, D. Pasquier, Electrochim. Acta (2021) 138961. https://doi.org/10.1016/j.electacta.2021.138961.

Resume : Redox flow battery (RFB) stands out as a promising energy storage technology owing to its independent power and energy features, long cycle life, and rapid response. Compared with the aqueous RFBs, the non-aqueous RFBs (NARFBs) have received increasing attention because of their wider electrochemical window and thus higher energy density. However, the performance of NARFBs has insufficient for commercialization, the lack of high ionic selectivity and ionic conductivity membrane is the key limiting factor. To improve the performance and efficiency, many novel membranes have been developed subsequently. In my group, we synthesized a two-dimensional (2D) metal organic framework (MOF) modified Celgard membrane via an infiltration method and achieved 82% EE at a current density of 12 mA cm-2. We also synthesized 2D vermiculite nanosheets modified porous membrane and achieved 85.8% EE at 2 mA cm-2. Furthermore, we proposed to utilize an intrinsic composite membrane to enhance the performance of the battery. For instance, we developing a novel highly selective MOF-based mixed-matrix membrane and a porous poly(vinylidene fluoride) membrane with 2D vermiculite nanosheets. Keywords: Non-aqueous redox flow battery, Membrane, Metal organic framework, Two dimensional materials

Resume : To ensure deeper market penetration, electrolytes of redox flow batteries (RFB) should be based on low-cost and abundant materials. All-organic systems based on new types of organic molecules are developed, from a study of theoretical calculations, fundamental chemistry to full-cell testing. The selection of organic active materials in relation to their physical and chemical properties (reaction kinetics, electrode potentials and solubilities) were facilitated by density functional theory (DFT) calculations. Based upon the results, we proposes new multi-electron active molecules with new reaction mechanisms that are capable of delivering multi-electron transfers and exhibiting superior electrode potentials in both aqueous and non-aqueous electrolytes. The proposed molecules were successfully demonstrated with reasonable solubilities (> 1 M) while demonstrating reversible behaviours using conventional electrochemical techniques. Following these, stable charge-discharge cycling performances of these active molecules were also performed with relatively high energy efficiencies (> 60 %) over prolonged operations, demonstrating the prospects of alternative organic molecules for future redox flow battery applications. Keywords: flow battery; organic; reaction mechanism

Resume : The rapid growth of the role of renewable energy sources dictates new requirements for electrochemical energy storage devices [1]. Among them, redox flow batteries (RFBs) are regarded as a promising technology, since their advantages of excellent scalability, low cost, easy fabrication and operation, long lifetime, and safety. Today inorganic RFBs are penetrating the market, however, low specific capacity in conjunction with low electrochemical stability window of aqueous electrolytes (≈1.5 V) and safety issues, hinders their wide-scale commercialization. [2]. Herein, we studied a group of organic materials based on aromatic amines with general formulas of NPh3RnBrm and N2Ph5RnBrm where R=-(OCH2CH2)2-OCH3. All the compounds demonstrated high solubility in MeCN, which potentially enables outstanding specific capacities approaching 134 Ah L-1 [3]. Compounds demonstrated one or two quasi-reversible electron transition processes with redox potential up to 0.6 V vs. Ag/AgNO3 reference electrode, which makes them perspective catholyte materials. For the RFB investigation butylviologen perchlorate ( 0.75V vs. Ag/AgNO3, ~1.15 V battery voltage) was chosen as the redox pair. Firstly, the selection of the most appropriate electrolyte was performed: it was shown that the usage of the TBABF4 and NaClO4 produces stable characteristics of RFB performance. Final RFB tests proved that the most promising systems are capable to exhibit 65% of maximum capacities and more than 95% Coulombic efficiency after 50 cycles [3]. In the next step, we synthesized and investigated novel phenazine derivative with oligomeric ethylene glycol ether substituents as promising anolyte material [4]. The designed compound undergoes a reversible and stable reduction at -1.72 V vs. Ag/AgNO3 and demonstrates excellent (>2.5 M) solubility in MeCN. A non-aqueous organic redox flow battery assembled using novel phenazine derivative as an anolyte and substituted triarylamine derivative as a catholyte exhibited high specific capacity (~93% from the theoretical value on the first cycles), >95% Coulombic efficiency and good cycling stability. To summarize, investigated materials establish themselves attractive for future research: obtained parameters open promising future directions for their usage as redox-active materials for non-aqueous RFBs. Romadina Elena acknowledges the support provided by Haldor Topsøe A/S Scholarship 2021. [1] Panwar N., Kaushik, S., Kothari S. Renew. Sustain. Energy Rev. 2011, 15 (3), 1513 1524. [2] Placke T., Heckmann A., Schmuch, R., Meister P., Beltrop K., Winter, M. Joule 2018, 2 (12), 2528 2550. [3] (a) Romadina E., Volodin I., Stevenson K., Troshin P. JMC-A, 2021, 9, 8303-8307; (b) Romadina E., Troshin P., Stevenson K., Patent RU2752762C1 “Highly soluble triphenylamine-based catholyte and electrochemical current source based on it” [4] Romadina E., Komarov D., Stevenson K., Troshin P. ChemComm, 2021, 57, (24), 2986-2989

Resume : In this lecture I discuss the latest progresses achieved with the computational modeling platform developed in the ARTISTIC project[1] which is able to predict the impact of manufacturing parameters on electrode and lithium ion battery (LIB) cell properties. This platform is supported on a hybrid approach encompassing a physics-based multiscale modeling workflow, machine learning models and high throughput experimental characterizations.[2] Different steps along the battery cells manufacturing process are simulated, such as the electrode slurry preparation, the coating, the drying, the calendering and the electrolyte infiltration. The multiscale physical modeling workflow couples experimentally-validated Coarse Grained Molecular Dynamics, Discrete Element Method and Lattice Boltzmann Method simulations and it allows predicting the impact of the process parameters on the final electrode mesostructure in three dimensions. The predicted electrode mesostructures are injected in a 3D-resolved continuum performance simulator capturing the influence of the pore networks and spatial location of carbon-binder within the electrodes on the solid electrolyte interphase formation (for anodes) and on the electrochemical response (of anodes vs. lithium, cathodes vs. lithium and the full cells). Machine learning models are used to accelerate the physical models’ parameterization, to mimic their working principles and to unravel manufacturing parameters interdependencies from the physical models’ predictions and experimental data, and as a guideline for reverse engineering. The predictive and optimization capabilities of this platform, coupling physical models with machine learning models, are illustrated with results for different electrode formulations and active material chemistries. Finally, I present the ARTISTIC Online Calculator, a free online service using our physics-based models, which allows you to predict the influence of manufacturing parameters on electrode architectures using your internet browser. References: [1] The ERC-funded ARTISTIC project website: https://www.erc-artistic.eu/ ; [2] List of the ARTISTIC project publications: https://www.erc-artistic.eu/scientific-production/publications

Resume : One of the major challenges towards a sustainable and greener society, is to develop efficient and secure energy storage systems. Lithium-ion batteries, being among the most prominent candidates, unfortunately still present some drawbacks. Thus far, commercial batteries still suffer from safety issues, capacity loss and cyclic degradation [1]. Consequently, the research interest is tremendous, and a plethora of new materials and composites are emerging daily. To investigate the performance degradation mechanisms, a multimodal characterization is often needed. Thus, we developed an analysis approach which allows to correlate high-resolution chemical and structural information of battery materials. The structural analysis is performed via Scanning Electron Microscope (SEM) imaging in a dual-beam Focused Ion Beam (FIB)-SEM instrument, and the chemical characterization is done with the FIB in combination with an in-house developed high-resolution high-sensitivity Secondary Ion Mass Spectrometer (SIMS) which is attached to the same FIB-SEM instrument. Both techniques can reach nm-range resolutions. Especially the implementation of a SIMS system is attractive as it is capable of detecting light elements such as H, Li, Be and B [2]. The latter are, on one hand, particularly difficult to characterize using conventional analytical techniques such as Energy Dispersive X-ray Spectroscopy and on the other hand, essential when investigating lithium-ion batteries. We are currently using the FIB-SEM-SIMS analysis methodology to study all solid-state Li batteries using LLZO garnets as solid electrolyte. The analytical method is used to inspect the characteristics of the components in the initial state (e.g. the quality of the adhesion between lithium metal anode and the LLZO) as well as in the cycled state. Furthermore, we designed an in operando FIB-SEM-SIMS sample holder, which allows charging and discharging solid state batteries or half cells. This enables the possibility to follow the structural and chemical evolution over several charge-discharge cycles and to identify the precise degradation mechanisms. The entire workflow is performed under high vacuum within the same instrument without the need to transfer the sample and risk contamination. In this presentation, we will showcase our latest experimental results to demonstrate the FIB- SEM-SIMS analytical methodology for battery materials. Ultimately, with this work we aim to reveal the complex relation between morphological appearance, chemical composition and electrochemical performance. We believe that correlative analysis approaches can give scientists valuable insights to understand and improve novel battery materials [3]. Acknowledgement: Financial support by the Luxembourg National Research Fund (FNR) through the INTERBATT project (INTER/MERA/20/13992061) is gratefully acknowledged. References [1] T. Waldmann et al., J. Electrochem. Soc. 163 (2016) A2149-A2164. [2] T. Wirtz et al., Nanotechnology 26 (2015) 434001. [3] M. Sun et al., ACS Energy Lett. 6 (2021) 451–458.

Resume : Silicon is one of the most promising anode materials replacing metallic Li due to a maximum specific capacity of 3579 mAh/g at room temperature to fabricate high-capacity anodes for lithium-ion batteries (LIB). However, the insertion of lithium in silicon is accompanied by a volume expansion of more than 300%, which hinders the use of layered Si structures due to pulverization of the electrode. The introduction of nanoscale structures such as nanowires and nanodots have been intensively investigated to reduce stress and overcome the intense volume expansion [1-2]. In layer structures, the patterning of Si anodes by photolithography and etching techniques [3] are proposed to enable the usage of Si layers in LIB. In 2012, He et al. reported the formation of Kirkendall voids in a Si-Cu layer structure, which effectively helps to compensate stress of the Si layer and resulting in an excellent cycling performance [4]. The Kirkendall effect is caused by the difference in diffusion rate of two different materials. In a non-equilibrium state of diffusion at the interface, the vacancies condense and form voids on the side of the atom with the faster diffusion rate [5]. In our work, we take advantage of the Kirkendall voids and create a thick multilayer of alternating Cu and Si layers. A patented temperature step with ultra-fast annealing helps to control the formation of Kirkendall voids shown in cross-sectional SEM. Furthermore, with low-energy tempering, the voids are formed, while for high- energy tempering, the formation of voids are suppressed and a full silicidation takes place. The void size can be controlled with the amount of copper or other metals in the layer. As prepared Si-Cu electrodes up to 5 µm thickness have been used to fabricate LIB coin cells with LiCoO2 cathode and LP30 electrolyte. No additive for SEI control is needed. The cells are cycled with a rate of C/2 in voltage rage between 3.0-4.0 V. Results show that the increase of Cu thickness and subsequent larger voids support the improved cycling performance with a specific Si capacity above 2000 mAh/g. Coulomb efficiencies above 99.5 % are achieved even after 50 cycles for a samples deposited by different thicknesses of Cu layer. References [1] Chan, Candace K., et al. NAT NANOTECHNOL 3.1 (2008): 31-35. [2] Krause, A., et al. J ELECTROCHEM SOC 166.3 (2019): A5378. [3] McSweeney, W., et al. NANO RES 8.5 (2015): 1395-1442. [4] He et al., J ELECTROCHEM SOC, 159 (12) A2076-A2081 (2012) [5] Kim et al., J MATER SCI: MATER ELECTRON, 22:703–716 (2011)

Resume : All-solid-state batteries (ASSBs) are closer than ever to wide-scale applications. They could bring improved safety, an enlarged temperature stability and extended cycle life compare to conventional Li-ion batteries using liquid electrolytes. If the compact solid electrolyte (SE) can stabilize Li metal dendrites growth, ASSBs would also level up two to three times the energy density. For the past decades, research has focused on improving the ionic conductivity of the SEs, until the discovery of the thiophosphate family, with an ionic conductivity similar or exceeding those of liquid electrolytes. However, due to their narrow electrochemical stability window, currently, the stronger focus is on the stabilization of their interfaces with both cathode and anode materials to improve the ionic transport. Understanding the degradation reaction mechanism taking place at these buried interfaces is extremely challenging. It requires the use of non-destructive surface sensitive techniques capable to provide depth profile chemical analysis combined with an excellent lateral resolution to discriminate signals originating from the surface and near surface of the different particles (active materials, solid electrolyte and conductive carbon additive) composing the working electrode. In this contribution, we present detailed surface and interface (electro-)chemical study of the working electrode (NCM622/LPSCl/C) cycled up to 4.3 V vs. Li+/Li. First, galvanostatic cycling and impedance spectroscopy demonstrate, as expected, a large irreversible charge of 32% during the 1st cycle and the gradual increase of the impedance with the number of cycles. Second, the interface chemical evolution is monitored by soft-X-ray absorption spectroscopy (XAS) at the TMs, P and S L-edges, as well as, at the C and O K-edges providing very crucial knowledge on the oxidation states and structural evolution during cycling of both NCM622 and LPSCl. The XAS acquisition is performed by combining measurements with the (i) high lateral resolution and surface sensitivity of X-ray photoemission electron microscopy (XPEEM) and (ii) depth profile total electron yield (TEY) and total fluorescence yield (TFY) at the SIM beamline of the synchrotron Swiss Light Source. Our results demonstrate that the 1st irreversible charge is mainly associated with LPSCl oxidation but the gradual impedance increase is caused also by the surface degradation on the NCM622 leading to the formation of inactive reduced TMs species. The full picture of the interface reaction will be presented by emphasizing the role of the unstable layered oxygen and the possible diffusion of TMs leading to the formation of sulfate, sulfide, phosphate and phosphide species.

Resume : Disruptive technology is necessary to improve battery energy and power densities with a significantly increased safety. Among positive electrode materials being attractive candidates for next battery generations, both Lithium ion batteries and all solid-state batteries, spinel LiNi0.5Mn1.5O4 (LNMO) appears as one of the favourite thanks to its numerous advantages: Co-free and thus more sustainable and with lower cost, high voltage (4.7 V vs Li+/Li) and thus high energy density (650 Wh/kg). Nevertheless, challenges are remaining before its integration in next generations of batteries, due to its reactivity at high voltage at the interface between the electrode and the (liquid or solid) electrolyte. Formation of protective surface layers is one of the route prospected to stabilize this interface. In this work, commonly used wet coating process will be compared to supercritical fluid chemical deposition (SFCD) in order to evaluate the advantage of this latter, that was previously shown to allow with success the formation of homogeneous and continuous coating at the surface of BaTiO3 particles 1. The main advantage of this process is its ability, as atomic layer deposition (ALD), to control precisely the thickness of the coating, but on powders and not only on electrodes as for ALD. Al2O3-type coating was chosen as abundant, cheap and simple to prepare by different synthesis processes. We will show that coated LNMO materials were prepared with optimal thickness for the Al-rich coating and that very attractive electrochemical performances were obtained, especially at high rates2. These composite materials have been characterized in-depth combining X-ray diffraction, scanning and transmission electron microscopy, as well as Infra-red, Raman, X-ray photoelectron and nuclear magnetic resonance spectroscopies. [1] Aymonier, C. et al. Supercritical Fluid Technology of Nanoparticle Coating for New Ceramic Materials. J. Nanosci. Nanotechnol. 5, 980–983 (2005). [2] Courbaron G., Delpuech N., Croguennec L., Aymonier C., & Petit E. (2021). Matériau d’électrode enrobé d’un composé particulier (FR2114404)

Resume : Over the past four decades, many researchers have studied rechargeable Li metal batteries (LMB) as a promising system due to the low electrochemical potential and high theoretical specific capacity of the lithium metal negative electrode [1]. Despite extensive research on LMB, their commercialization continues to be hampered by their poor performance, and the origin of many essential factors governing it remains elusive [2]. One of these parameters is the nucleation overpotential, which represents the energy required to form the Li nuclei during plating. Although some research has been carried out on the nucleation overpotential of Li metal [3-5], still little is known on its origin. In the literature, this phenomenon is often measured with a two-electrode setup, which fails to demonstrate the contribution of the working and counter electrodes independently. To achieve a clear view of nucleation overpotential, we used a three-electrode setup to deconvolute the potential associated with each electrode during galvanostatic Li electrodeposition. Our findings demonstrate that the main source of observed polarization is a quick drop in the potential of the counter electrode (lithium foil), which can be attributed to Li stripping from the counter-electrode. This finding may aid in clarifying the origins of the experimental polarization, preventing researchers from misinterpreting it in terms of nucleation overpotential. References: [1] Cheng, Xin-Bing, et al. "Toward safe lithium metal anode in rechargeable batteries: a review." Chemical reviews 117.15 (2017): 10403-10473. [2] Horstmann, Birger, et al. "Strategies towards enabling lithium metal in batteries: interphases and electrodes." Energy & Environmental Science 14.10 (2021): 5289-5314. [3] Yan, Kai, et al. "Selective deposition and stable encapsulation of lithium through heterogeneous seeded growth." Nature Energy 1.3 (2016): 1-8. [4] Pei, Allen, et al. "Nanoscale nucleation and growth of electrodeposited lithium metal." Nano letters 17.2 (2017): 1132-1139. [5] Biswal, Prayag, et al. "Nucleation and early-stage growth of Li electrodeposits." Nano letters 19.11 (2019): 8191-8200.

Resume : Energy storage systems will play an essential role in reducing fossil fuel consumption and greenhouse gas emissions by providing solutions to store energy produced from renewable sources and implement electrical mobility. Graphite is the conventional material used to fabricate standard rechargeable batteries and supercapacitors. Nonetheless, it has some limitations such as limited intrinsic capacity, lithium-ion insertion capacity, and specific capacitance. Additionally, graphite, together with lithium and cobalt, characteristic materials used in Li-ion batteries, are limited resources, especially since Europe depends on importation and external supply. In this sense, UNIZAR is leading the European project NOEL: Innovative Nanostructured Electrodes for Energy Storage Concepts preparing new functionalized carbons with non-toxic nanocrystals to be used as electrode materials for post-lithium batteries and supercapacitors, in collaboration with the National Institute of Chemistry (NIC) in Slovenia and the Poznan University of Technology (PUT), Poland. The presence of metal sulphide nanocrystals on the carbon surface can bring interesting features like higher surface/volume ratio, which can increase the contact area between electrode and electrolyte, more ion adsorption sites, smaller distances for ion or electron transport and better accommodation of the mechanical strain and structural distortion. Novel carbon-nanoparticle hybrids have been prepared, using new carbons synthetized at NIC as well as commercial carbons, for their use as electrodes in batteries and supercapacitors. The characterisation techniques confirm the incorporation of nanocrystals, the control on the preparation and its reproducibility.

Resume : In the field of energy storage, bulk chemical/morphological information of composite materials and electrodes and their evolution during cycling are of high interest. However, conventional analytical methods are often limited to access to the bulk properties of composites as they are buried. To tackle this challenge, samples preparation by cross-section coupled to nano-Auger analysis is developed as a suitable alternative. In the case of conversion-based electrodes for Li-ion batteries and beyond, direct evidence of the conversion reaction after long term cycling remains to be elucidated so far. Here, cross-section Auger imaging allows revealing the chemical/morphological evolution of TiSnSb conversion material at the electrode scale with a nano resolution.[1][2] Importantly, results show that the conversion mechanism still occurs even after 400 cycles, which was unexpected. In the case of pseudocapacitive composite materials for hybrid supercapacitors, their bulk organization and structure remain a challenge to investigate. Here, cross-section Auger imaging allows revealing the nanoscale assembly and porosity of Mn-Co composites prepared by exfoliation/restacking, which could not be proven so far.[3] Overall, a good correlation between the restacking method, the nanoscale organization/structure of composites and resulting electrochemical performance was obtained. Finally, the innovative cross-section Auger approach presented here is suitable to get reliable and relevant bulk chemical/morphological information in composites for energy storage and will also benefit to other research fields. References [1] L. Madec, J.-B. Ledeuil, G. Coquil, L. Monconduit, H. Martinez, Cross-Section Auger / XPS imaging of conversion type electrodes: how their morphological evolution controls the performance in Li-ion batteries, ACS Appl. Energy Mater. 2 (2019) 5300. [2] L. Madec, J.B. Ledeuil, G. Coquil, G. Gachot, L. Monconduit, H. Martinez, Cross-section Auger imaging: A suitable tool to study aging mechanism of conversion type electrodes, J. Power Sources. 441 (2019) 227213. [3] L. Madec, C. Tang, J. Ledeuil, D. Giaume, L. Guerlou-demourgues, H. Martinez, Cross-Section Auger Analysis to Study the Bulk Organization / Structure of Mn-Co Nano-Composites for Hybrid Supercapacitors, J. Electrochem. Soc. 168 (2021) 10508.

Resume : Advanced electrochemical energy storage devices (ESDs) are internationally considered as one of the disruptive technologies of the future. On the main trends that drive energy storage development in our daily life is the rise of electrical devices. Lithium-ion batteries (LIBs) have revolutionized our society, since its first commercialization in 1991 by Sony. Despite its great success, LIBs need to be improved in term of energy power density, speed charge capabilities, cost, and safety. Notably, such safety risks are unacceptable for autonomously powered medical implants, residing inside the human body. In this context, in recent years, extensive efforts have been devoted to design new anodes or cathodes, improve the electrolyte properties or designing new batteries more sustainable (e.g. Sodium-ion batteries (SIBs)) [1]. Among new materials investigated in the literature, transition metal oxides (TMO) (e.g. vanadium oxide (VOx) and zinc oxide (ZnO)) have shed new promises for future ESDs electrodes in regards to their unique physico-chemistry properties, such as layered structures, thermal stability and high theoretical capacity [2,3]. VOx exist in various compositions (e.g. V2O5, VO2, V2O3 and VO). As anode material, V2O5 and ZnO can reach, respectively, a theoretical capacity of 1472 and 978 mAh/g, which are far more than the actual anodes (e.g. graphite ~372 mAh/g). As cathode, V2O5, V2O3, and VO2(B) can attain a theoretical capacity of 294, 356 and 324 mAh/g [3] which is higher than known cathode materials such as LiCoO2 (140 mAhg-1). Recently, TMO oxides in thin-film, two (2D) or one-dimensional (1D) nanostructured architecture have attracted the attention in ESDs field since their development can provide high surface area, short pathways and high kinetics for lithium ion insertion/extraction [4]. In the present work, we aim to synthesize directly on graphene (G)-based current collector, VOx and ZnO thin films/nanostructures by physical vapor deposition (PVD) and electrochemical deposition (ED) methods. The synergy of the undoped or doped oxides with graphene have been studied. The physico-chemical properties of the thin films were multi-parametrically surveyed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDXS), X-ray diffraction measurements (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The electrochemical performance was measured by using cyclic voltammetry, impedance and galvanostatic charge-discharge methods. SEM analysis have shown the formation of VOx and ZnO structure with opened porosity. Compared with the bare electrode, (Mg-doped) ZnO/V2O3 electrodes on graphene exhibited enhanced electrochemical properties. [1] A. El Kharbachi et al. J. Alloys Compd. 817, 153261 (2020) ; [2] Zhang et al., Journal of Energy Chemistry 59, 343?363 (2021) [3] Khac Hoang Bui et al., Nanomaterials, 11, 2001 (2021) [4] Yao et al., Journal of Alloys and Compounds 521, 95? 100 (2012)

Resume : Lithium-ion batteries are regarded as one of the keystone technologies of the energy transition of our society. But the projections on the required amounts of critical resources such as lithium, copper, nickel, and cobalt are raising concerns about the capability of maintaining an economical and constant supply of raw materials for their production. [1, 2] Therefore, new chemistries are being studied to find alternatives to the lithium-ion paradigm. In the last 20 years, organic materials for batteries have found extensive fortune among researchers. An uncountable number of monomers and polymers that can undertake redox reactions with alkali metals cations or anions were synthesized and tested on a laboratory scale. [3] Nevertheless, a systematic study on the cost and performances of commercial-like batteries made with such materials and the comparison with commercial and highly promising inorganic lithium-ion chemistries is necessary to understand the practical viability of organic batteries, and which specific classes of organic materials can be competitive. Using BatPac 4.0, an analysis on several organic redox monomers for lithium-ion batteries, selected after an extensive literature review, has been performed. [4] The software allows the simulation of different configurations of battery packs, and in this study, three kinds of packs, i.e., for domestic energy storage, plug-in hybrid vehicles, and fully electric vehicles, have been modeled. The cost, the specific capacity, the voltage curve, and the density of each material was calculated, estimated, or measured, according to the availability of such data in patents and scientific articles. Combinations of organic cathodes with organic anodes or Li-metal anode have been compared with NCM811 and LFP vs. graphite and Li-metal configurations. Effects of the amount of carbon in the organic electrodes and of the raw material cost have been also taken into account. [1] Greim, P., Solomon, A. A., Breyer, C.. Assessment of lithium criticality in the global energy transition and addressing policy gaps in transportation. Nat. Commun. 11, 4570, 2020 [2] Vaalma, C., Buchholz, D., Weil, M., Passerini, S.. A cost and resource analysis of sodium-ion batteries. Nat. Rev. Mater. 3, 18013, 2018 [3] Esser, B., Dolhem, F., Becuwe, M., Poizot, P., Vlad, A., Brandell D.. A perspective on organic electrode materials and technologies for next generation batteries. J. Power Sources 482, 228814, 2021 [4] Nelson, P. A., Ahmed, S., Gallagher, K. G., and Dees, D. W.. Modeling the Performance and Cost of Lithium-Ion Batteries for Electric-Drive Vehicles, Third Edition. United States: N. p., 2019 A.I. acknowledges the EU’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement N. 860403 “POLYSTORAGE” for the funding of the position. All the authors thank the support of the Helmholtz Association for the basic funding.

Resume : Copper has been termed the ?metal of the 21st century?. In particular, the electrochemical production of integrated copper circuitry (?Damascene Process?) has revolutionized information technology. The steadily decreasing dimensions of the wires and vias of the circuitry calls for a detailed understanding of the electrochemical behaviour of copper on the nanometer, even atomic, scale. This obviously turns the gaze on the influence of atomic scale surface defects in the underlying electrochemical deposition and etching processes. In this contribution we present in situ electrochemical scanning tunneling microscopy (EC-STM) results, i.e. registered in solution, on the reconstruction of well-defined vicinal Cu(111) electrodes of progressively reduced terrace width (e.g. Cu(21 21 16) and Cu(221)) in dilute sulfuric acid solution (H2SO4). In contact with H2SO4 the flat reference Cu(111) electrode is known to reconstruct due to a strong interaction between copper and the sulfate anions, thereby forming a very stable Moiré ? superstructure. A slight distortion of this superstructure leads to the formation of three 120° rotated domains. We observe a distribution of terrace widths of the Cu(221) electrode after anodic adsorption of SO4 ? anions. All the measured three widths (1.2nm (1); 2.1 nm (2) and 3,3 nm (3)) are significantly larger than the terrace width of the bare Cu(221) surface (0.74 nm), but fully consistent with multiples of the size of a Moiré unit in different orientation. The underlying adsorbate induced transport processes may be suited to control the surface topography of surfaces, e.g. before the deposition of further species, and confined systems.

Resume : First-principles calculations for the structural, electronic, magnetic, elastic and thermodynamic properties of full-Heusler compound Co2TiPb, have been performed for using full-potential linearized augmented plane wave (FP-LAPW) scheme within the GGA approximation. Features such as the lattice constant, bulk modulus, and its pressure derivative are reported, in addition to the results of the band structure and the density of states. In all studied compounds, the stable type Cu2MnAl was energetically more favourable than type Hg2CuTi structure. The electronic structure in the ferromagnetic configuration for Co2TiPb Heusler compound shows that the spin-up electrons are metallic, but the spin-down bands are semiconductor. From electronic calculations, it is found that all the compounds studied have an indirect band gap with a half-metallic behavior. The compound Co2TiPb has a total magnetic moment of 2, well consistent with the Slater-Pauling rule. The elastic constants reveal that the Co2TiPb are mechanically stable and the Poisson’s ratio confirmed that the alloys considered are ductile. Finally, we calculated the thermodynamic properties such as heat capacity, thermal expansion and Debye temperature using the quasi-harmonic Debye model at temperatures from 0 to 1200 K.

Resume : Carbon electrode technology is rapidly accelerating throughout the last few decades and a lot of research effort has been focused on electrochemical devices and mechanisms. Redox active conducting polymers are considered promising organic materials for electrochemical devices due to their favorable properties such as conductivity, reversibility and environmental stability. They have the ability to store electric energy as pseudo-capacitors and have been explored extensively as materials in secondary energy storage devices because of their apparent advantages, such as structure and morphology control, low weigh, flexibility and relatively low cost. Polypyrrole (PPy) is one of the most promising conductive polymers for industrial application as it can be easily prepared by chemical oxidation of monomer in acidic aqueous environment. In particular, Iron (III) chloride (FeCl3) and ammonium persulfate (APS) are the most frequently used oxidants of the pyrrole. Typical granular PPy has some drawbacks regarding its specific surface area which is a major property for electrochemical electrodes. In this work we present a composite material of one-dimensional PPy nanotubes (PNTs) and porous carbon as a candidate for use in electrochemical applications such as capacitive deionization (CDI), which is a water desalination technology where electrical field is applied while the feed water flows between two electrodes. As a result, the ions in the saline feed are adsorbed on the opposite electrodes reducing the water salinity. During the process, no high pressure needs to be applied. The resultant composites were characterized by Fourier Transform Infrared (FTIR) spectroscopy and their morphology was studied by scanning electron microscopy (SEM). The electrochemical performance of the nanocomposite electrodes was evaluated in 1M sodium chloride (NaCl) aqueous solution using a three-electrode configuration. Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS) measurement techniques were used to determine the specific capacitance. The Carbon/PNTs composites obtained exhibited reversible electrochemical properties even in a neutral aqueous environment, probably due to the π-π interaction between the materials. Capacitance of 173 Fg-1 was obtained at 12mAg-1.

Resume : Lithium-Air (O2) batteries are considered as one of the next generation batteries, due to their very high specific energy. In parallel, Redox Flow Batteries (RFBs) are getting much attention in the energy transition because of their highly flexible design that enables the decoupling of energy and power. However, commercial RFBs still suffer from low energy density. One of the solutions proposed to increase the energy density is the combination of the high energy density of the Li/O2 battery with the flexible and scalable architecture of redox flow batteries in semi-solid flow Li/O2 batteries. The challenging activities on materials and components development and prototyping of semi-solid flow Li/O2 batteries are presented and discussed.

Resume : Investigation of Zinc-based Spinels & (Pyro)phosphates for Zn-ion and Zn-air Batteries Deepa Singh* (1), A Baby (1,2), & Prabeer Barpanda (1) (1) Indian Institute of Science, Bangalore, India; (2) University of Illinois at Urbana Champaign (UIUC), IL, USA. *deepasingh@iisc.ac.in Abstract Although Li-based batteries are the undeniable leaders in the portable energy storage sector, it is difficult to replicate their success in large-scale stationary energy storage due to the scarcity of Li, high cost, and the inclusion of non-aqueous electrolytes, which make them relatively perilous and inefficient. Recently, aqueous Zn-ion batteries (ZIBs) have emerged as alternate candidates featuring the inherently safe nature of metallic Zn anode and its unique properties.1 Ideal spinel structure is suggested to be incompetent for reversible intercalation of Zn2+ due to higher electrostatic repulsion arising from its dipositive nature. Hence, many synthesis routes are adopted to synthesize spinels that incorporate cation deficiency or cumbrous pathways to enhance Zn2+ (de)intercalation. Herein, we report an economical, fast, and template-free solution combustion synthesis of ZnMn2O4 (ZMO), ZnCo2O4 (ZCO), and ZnMnCoO4 (ZMCO) nanostructured spinels. For the first time, reversible Zn2+ (de)intercalation is observed for ZMCO cathode (ca. 1.5 V vs. Zn2+/Zn) using a low-cost ZnSO4 electrolyte with MnSO4 additive to suppress Mn dissolution from the cathode.2 On another note, highly efficient bifunctional activity is desirable for high energy-density zinc-air batteries. The above-mentioned spinels along with zinc substituted (pyro)phosphates ZnCo2(PO4)2 (ZCP1) and ZnCo2P2O7 (ZCP2) have been examined as bifunctional electrocatalysts in an alkaline medium (0.1 M KOH). The Oxygen reduction reaction (ORR) activity of ZMCO is found to be comparable (onset potential: 0.94 V, the diffusion-limited current density: 5.93 mA/cm3) to existing literature. For the first time, ZCP1 & ZCP2 are shown to exhibit promising stable bifunctional electrocatalytic activities, leading to their application in Zn-air batteries.3 The synthetic, structural, and electrochemical activity of these spinels and phosphates will be described synergizing various experimental and computational tools. References (1) Song, M.; Tan, H.; Chao, D.; Fan, H, J. Recent advances in Zn-Ion batteries. Advanced Functional Materials 2018, 28(14), 1802564. (2) Baby, A.; Senthilkumar, B.; Barpanda, P. Low-cost Rapid Template-free synthesis of nanoscale zinc Spinels for energy storage and electrocatalysis applications. Applied energy materials. 2019, 2(5), 3211-3219 (3) Baby, A.; Singh, D.; Murugesan, C.; Barpanda, P.(2020). The design of zinc-substituted cobalt (pyro) phosphates as efficient bifunctional electrocatalysts for zinc-air batteries. Chemical Communications, 2020, 56(60), 8400-8403.

Resume : Rechargeable zinc-ion batteries (ZIBs) are innovative and promising devices for electrochemical energy storage. Compared to traditional Li-ion technology, the use of a Zn metal anode in combination with an aqueous electrolyte is advantageous in terms of safety, sustainability, cost, ease of preparation, and availability of raw materials. However, several issues are still to be solved, including the risk of Zn corrosion and/or shape change and the instability of the water medium. In addition, a few cathodic materials are currently available, such as Mn and V oxides, V phosphates, and Prussian blue analogues, for which a clear understanding of the electrochemical mechanism is still lacking. A deeper investigation into the electrochemical mechanism is enabled by thin films, which are suitable as model systems and open the possibility of microbatteries. Zn manganites could be effectively used as cathode materials to provide Zn2+ ions thanks to low cost, abundance, environmental benignity, and relatively high redox potential. However, the available literature is scarce and the exact storage mechanism, possibly involving structural changes, phase transitions, precipitation, and proton insertion, is not fully clarified. Here, we report on the synthesis of spinel ZnMn2O4 thin films by Pulsed Laser Deposition (PLD) as candidates for aqueous ZIBs. The versatility of PLD allows the exploration of several thin film structures and morphologies at the nanoscale, which could alleviate volume changes and positively affect the kinetics of the charge transfer, reducing the diffusion path for electrons and ions, thus compensating for poor electrical conductivity without the use of any binder or conductive agent. For example, the presence of an oxygen background gas during deposition permits one to tune the film nano-porosity, and hence its density and surface area, while the post-process annealing temperature allows one to vary the degree of crystallinity of the film and the size of the crystalline grains. The effect of deposition parameters on the film morphology, stoichiometry and vibrational/optical properties is explored by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), Raman, and ultraviolet-visible (UV-VIS) spectroscopies, as well as the effect of annealing temperature, atmosphere, and duration. We then discuss preliminary measurements correlating the different film structures and morphologies to the electrochemical behaviour. The use of in situ Raman spectroscopy allows the characterization of vibrational properties during the application of electrochemical polarization. As a result, one can probe the phase evolution of the cathode material during charge/discharge in slightly-acidic aqueous electrolyte and correlate it to the electrochemical reactions occurring in spinel ZnMn2O4.

Resume : One of the most widely explored paths to reduce the cost of electrochemical storage systems is the replacement of current lithium metal with alternative metal anodes. Aluminum-ion batteries are rapidly gaining momentum for use in the next generation energy storage industry. Aluminum is the most abundant metal in the Earth’s crust, with a four and seven times larger volumetric capacity compared to lithium and sodium respectively. Additionally, the three-electron redox reaction (Al+3) and the smaller ionic radius (0.0535 nm) of aluminum offer the path to achieve higher specific energy and power. But, exploring compatible and high-performance cathode materials for rechargeable aluminum ion battery is a key challenge. In this paper, we discuss the electrochemical performance of V2O5 as a cathode material for aluminum ion battery in AlCl3 aqueous solution. The nanostructure of V2O5 was synthesized via hydrothermal synthesis protocol. The preliminary physiochemical characterization of synthesized V2O5 was performed using various techniques. The electrochemical properties were investigated by cyclic voltammetry and charge-discharge measurements in 0.5 M AlCl3 aqueous electrolyte. The V2O5 cathode delivered an initial discharge capacity of ~ 50 mAh g-1 at high current density of 1000 mA g-1 and the capacity was maintained over 200 cycles. The high energy storage mechanism of V2O5 can be attributed to the facile intercalation and deintercalation of the tri-valent Al+3 ions from the electrolyte through the electrode material during discharging and charging processes, respectively. Further, the V2O5 cathode fabricated in this work is of low cost with high safety, making it a useful material for aqueous aluminum ion batteries.

Resume : New battery technologies have received increased attention in recent years, especially those based on the use of divalent cations such as calcium and magnesium. Their high abundance (calcium and magnesium being, respectively, the 5th and 8th most abundant element in the earth crust) and the possible safe use of metal anodes could result in more sustainable devices with lower cost and higher energy density systems when compared to Li-ion. Feasibility of plating/stripping of calcium metal has been demonstrated recently [1] in very few organic electrolyte formulations. In all cases, some degree of electrolyte reduction and formation of passivation layer were reported. [2] In particular, using Ca(BF4)2 in a mixture of carbonate solvents, a fully conformal passivation layer is formed at the surface of the metal anode. Yet this layer allows for Ca plating and stripping, thus exhibiting similar behavior as a solid electrolyte interphase (SEI). However, the nature and composition of such layer remain mostly unknown. In this communication, an in-depth analysis of the SEI will be presented. The influence of the electrolyte formulation (salt, solvent and additive) on the formation of the SEI and how it affects Ca plating and stripping kinetics were investigated. Among other techniques, XPS, EELS and ToF-SIMS measurements allowed to detail the composition of the SEI. The homogeneity, the morphology and the microstructure were studied by means of TEM and synchrotron-based µFTIR microspectroscopy. [1] M.E. Arroyo-de Dompablo, A. Ponrouch, P. Johansson, M.R. Palacín, Achievements, Challenges, and Prospects of Calcium Batteries, Chem. Rev. 2020, 120 6331–6357. [2] Forero-Saboya, J. D., Tchitchekova, D. S., Johansson, P., Palacín, M. R., Ponrouch, A., Interfaces and Interphases in Ca and Mg Batteries. Adv. Mater. Interfaces 2021, 2101578.

Resume : Among positive electrode materials for K-ion batteries, KVPO4F vanadium phosphate fluoride has been proposed as a high voltage material with a theoretical capacity of 131 mAh·g-1 at an average voltage of 4.3 V. Such properties confer a theoretical energy density of 560 Wh·kg-1 at the material scale, which is the same as largely commercialized LiFePO4. However in practice only ~100 mAh·g-1 can be reversibly reached, corresponding to 0.8 K exchanged. In this work, we investigated whether the impossibility to reach full capacity originates from structural constraints or kinetic limitations. K0VPO4F synthesized by chemical deintercalation of potassium from KVPO4F was characterized by the means of X-ray diffraction and MAS-NMR and XAS spectroscopies. It was evidenced that the polyanionic framework was conserved despite contraction of the unit cell volume by 9%. Further electrochemical characterizations of K0VPO4F led us to conclude that the failure to reach theoretical capacity is due to a competition between electrochemical de-insertion on one hand and side reactions driven by the instability of the electrolyte above 4.5 V on the other hand. This work was also extended to anion substituted KVPO4F0.5O0.5 and similar conclusions are drawn. This study also highlights the interest of combining a chemical K insertion/de-insertion to the electrochemical measurements to investigate the structure and reactivity of active materials at the frontier of their stability.

Resume : Sodium, in contrast to other metals, cannot intercalate in graphite, hindering the use of this cheap, abundant element in rechargeable batteries. Here, we report1 a nanometric graphite-like anode for Na+ storage, formed by stacked graphene sheets functionalized only on one side, termed Janus graphene. The asymmetric functionalization allows reversible intercalation of Na+, as monitored by operando Raman spectroelectrochemistry and visualized by imaging ellipsometry. Our Janus graphene has uniform pore size, controllable functionalization density, and few edges; it can store Na+ differently from graphite and stacked graphene. Density functional theory calculations demonstrate that Na+ preferably rests close to -NH2 group forming synergic ionic bonds to graphene, making the interaction process energetically favorable. The estimated sodium storage up to C6.9Na is comparable to graphite for standard lithium ion batteries. Given such encouraging Na+ reversible intercalation behavior, our approach provides a way to design carbon-based materials for sodium ion batteries. 1 Science Advances 2021; 7 : eabf0812

Resume : Sodium-ion batteries (SIBs) is one of the more promising battery technologies that are starting to see commercialisation, were the low cost, abundance of necessary raw materials, higher safety and power and similar energy densities compared to lithium-ion batteries (LIBs) are often mentioned as their key advantages. SIBs, due to their great similarities with LIBs have seen rapid development. One of the key differences, however, is the carbonaceous negative electrode, where SIBs, due to Na+ not forming thermodynamically stable binary intercalation compounds with graphite, the anode of choice for LIBs, are forces to use primarily hard carbons. But, it was recently discovered by Jache et al. that Na+ can form stable ternary graphite intercalation compounds through a solvent co-intercalation mechanism, thus enabling the use of graphite in SIBs [1]. This sparked several follow-up studies exploring solvent co-intercalation [2], which have shown that the system has great rate capabilities and remarkable cycle life but is plagued by a large volume expansion and poor energy density due to the low specific capacity of the system and the high potential vs. sodium where the co-intercalation reaction happens. Even after all these investigations, the question of how many solvent molecules are intercalated along with the cation, and thus the stoichiometry of the redox reaction, was never settled. Here, we present a novel electrochemical method to directly measure the number of solvents that are brought along by the cation into the graphite host structure by investigating glyme based electrolytes. The knowledge from these measurements enabled us to rationally design new electrolytes, composed of glymes mixed with another co-solvent, that both increases the energy density of the system by lowering the voltage where co-intercalation occurs, and by establishing a new low voltage plateau showing that these electrolytes enable a new electrochemical reaction, while also reducing the cost of the electrolyte. The impact of the new electrolytes on the structure of graphite is studied using operando dilatometry and XRD – showing that the detrimental volume expansion that occurs upon co-intercalation is greatly reduced using these new electrolytes. The local electrolyte structure is investigated with ab initio molecular dynamics, showing how the structure and stability of the solvation shells changes with the ratio of salt to glyme, glyme per co-solvent, and glyme to carbon, which we connect with the observed altered electrochemical behaviour and the structural changes of graphite upon sodiation. The experimental and computational studies together giving a comprehensive view of the system. [1] B. Jache, P. Adelhelm, Angew. Chem. Int. Ed. 2014, 53, 10169-10173, DOI: 10.1002/anie.201403734 [2] J. Park, Z-L. Xu, K. Kang, Front. Chem., 2020, 8:432, DOI: 10.3389/fchem.2020.00432

Resume : Na-ion batteries (NIBs) are promising devices to replace the prevailing Li-ion based technologies (LIBs) for large-scale energy storage, thanks to cheap and easily available sodium raw materials [1]. However, the large Na+ radius hampers a reversible sodiation-desodiation of common LIB negative electrodes [2] and great research efforts are devoted to development and optimization of highly effective NIB anode materials [3]. In this context, TiO2 anatase has been proposed as a possible anode material for both NIB and LIB devices because it ensures low operation voltage, high capacity, nontoxicity, and low cost. Recent experiments highlighted that the performances of anatase nanoparticles (NPs) as NIB negative electrode depend on the exposed NP surfaces: the (100) and (001) facets being much more effective than the most stable (101) surface [6]. The behavior of these different surface terminations has been ascribed to a convenient accommodation of the large cations without large crystalline lattice distortion for the (100) surface, and to an easy insertion to the sub-surface layer for the (001) [7]. However, in operando conditions should also consider the presence of an electric field, which is neglected in common DFT simulations of anatase-Na+ interfaces. Here, we report a first-principles investigation on the Na+ adsorption and intercalation on exposed TiO2 anatase-crystal facets, the (101), (100) and (001), under the influence of an external electric field. Following computational approach pioneered for TiO2 by Selloni and coworkers [8], we applied the PBE+U level of theory [9,10] and we simulated the electric field in the direction perpendicular to the surface by adding a sawtooth-like potential [12] to the bare ionic potential. We found that the direction of the applied field can have a significant influence on the Na uptake, with the insertion more favorite at electric field opposite to z-axis. Moreover, the electric field affects the Ti4+/3+ redox couple, that is involved during Na+ intercalation reaction at the NIB electrode. Overall, our findings will improve the current understanding of electrochemical reactions at NIB electrode surface and will help the further design of new effective anodes for this promising energy storage devices. [1] Abraham, K.M.; ACS Energy Lett. 2020, 5, 11, 3544 [2] Lu, Y.; et al. Adv. Energy Mater., 2018, 1702469. [3] Li, L.; et al. Energy Environ. Sci., 2018, 11, 2310. [6] Longoni, G.; et al. Nano Lett., 2017, 17, 992. [7] Massaro, A.; et al. Nanoscale Adv., 2020, 2, 2745. [8] Selçuka, S.; Selloni, A.; J. Chem. Phys., 2014, 141, 084705. [9] Perdew, J.P.; Burke, K.; Ernzerhof, M.; Phys. Rev. Lett., 1996, 77, 3865. [10] Anisimov, V.I.; Zaanen, J.; Andersen, O.K.; Phys. Rev. B, 1991, 44, 943. [12] Kunc, K.; Resta, R.; Phys. Rev. B, 1986, 34, 7146.

Resume : The evolution of energy storage devices which are inexpensive and possess large capacity are important for our future energy needs. Battery active materials, which are economic and can be produced via a facile synthesis, are extensively explored.1 In current work, NASICON type NaFe¬2PO4(SO4)2 was examined as a battery insertion material for rechargeable batteries.2, 3 It was synthesized via a facile spray drying method for the first time with spherical morphology, for usage as cathode material in Li-ion as well as Na-ion batteries. Electron microscopy confirmed the formation of nanospherical morphology. Vibration spectroscopy analysis (FTIR, Raman and UV vis) confirmed the presence of sulphate and phosphate groups. Isothermal acid solution calorimetry technique was employed to find the dissolution enthalpy for the material considering enthalpy of formation of reactants via Hess’s Law. Theoretical and experimental studies were done to get a better understanding of the electrochemical behavior, along with the underlying redox mechanisms. Theoretical calculations like density functional theory (DFT), bader charge analysis, bond valence sum energy (BVSE) were employed to predict various fundamental properties and the redox involved. Electrochemical performance for both Li and Na ion batteries was tested by cyclic voltammetry, galvanostatic cycling and electrical impedance spectroscopy. The results indicate that NaFe¬2PO4(SO4)2, employing Fe+3/+2 redox couple, is a good intercalating cathode for both Li and Na batteries in the voltage range of 2.0 V to 4.5 V with good capacity and cycling stability. Keywords: polyanions, capacity, cathode, crystal structure, intercalation, single particle model 1. Tarascon, J.-M. Key challenges in future Li-battery research. Phil. Trans. R. Soc. A. 2010, 368 (1923), 3227-3241. 2. Yahia, H. B.; Essehli, R.; Amin, R.; Boulahya, K.; Okumura, T.; Belharouak, I. J. J. o. P. S. Sodium intercalation in the phosphosulfate cathode NaFe2 (PO4)(SO4) 2. 2018, 382, 144-151. 3. Shiva, K.; Singh, P.; Zhou, W.; Goodenough, J. B. NaFe 2 PO 4 (SO 4) 2: a potential cathode for a Na-ion battery. Energy Environ. Sci. 2016, 9 (10), 3103-3106.

Resume : Sodium metal batteries (SMBs) have recently gained attention as promising energy storage systems. SMBs are a competitive technological paradigm compared to the state-of-the-art lithium ion batteries thanks to the high specific capacity of sodium metal, i.e. 1166 mAh/g, and the Na+/Na0 low redox potential of -2.71V vs. SHE. Dendrite growth of sodium is the main drawback that hinders the development of SMBs. Herein, we propose Na-SG-II as an active material in order to obtain dendrite-free sodium metal anodes. Na-SG-II is a functionalized silica gel material with extended porosity that can act as a host for sodium plating/stripping to mitigate the dendrite growth. Na-SG-II is a dual-phase material obtained by absorption of liquid Na into nanostructured silica gel and subsequent heating up to 400°C for 15h, leading to an open structure constituted by Na4Si4 and Na2SiO3. Na-SG-II has been incorporated in composite electrodes using a conductive carbon additive and polymeric binders. Binders with different mechanical properties, PVDF and PEO, are used in order to point out their impact on the electrochemical performance in batteries. Galvanostatic tests of the Na-SG-II electrodes in half cells versus Na anodes demonstrates that the active material allows an highly reversible sodium plating/stripping with 100% of coulombic efficiency for at least 200 cycles at room temperature. The analysis of the experimental overpotentials at various applied currents by the Tafel equations allowed to estimate the exchange currents J0 and the symmetry factors β. Apparently PEO-based electrodes outperform in terms of electrokinetic activity the PVDF-based ones.

Resume : Na-ion batteries (NIBs) are rapidly emerging as promising post-Lithium technology for large-scale applications, thanks to the wide availability and low cost of raw materials [1]. Research efforts aiming at developing an effective deployment of NIB technology are mainly focused on the design and optimization of highly efficient active materials, which for the cathode side seem to rely on enhanced energy density and stability [2]. Layered transition metal oxides (NaxTMO2) have shown outstanding performances as high-energy cathode materials in NIB cells and exhibited the chance to attain larger specific capacity by enabling anionic reactions at high operating voltage [3, 4]. This represents a new paradigm in the development of positive electrodes, but the O2-/O2n-/O2 redox processes need to be finely controlled to prevent the release of molecular oxygen and thus huge capacity loss. We report a first-principles investigation of P2-type Mn-defective layered oxides with different metal doping at the TM site (e.g., Ni or Ni and Fe) by means of PBE+U-D3(BJ) calculations. Structural and electronic features are dissected for each redox-active element in NaxNi0.25Mn0.68O2 (NNMO) and NaxFe0.125Ni0.125Mn0.68O2 (NFNMO) materials as function of sodiation degree corresponding to different states of charge. We address the oxygen redox activity by considering the formation of oxygen vacancies and dioxygen metal complexes at low Na loads (i.e., high voltage range). Low-energy superoxide moieties with different coordination geometries are predicted to be formed at x Na = 0.25 in Mn-deficient sites, while the x Na = 0.125 content enables the release of molecular O2 via preferential breaking of Ni-O bonds. Mechanistic insights show that dioxygen formation is driven by the M-O covalency and unveil that O2 loss can be effectively suppressed by Fe doping. Our findings pave the route for the rational design of high-energy NaxTMO2 cathodes that feature enhanced reversible capacity and thus boost the development of efficient NIB devices. These outcomes are collected in a recent publication on ACS Energy Letters [5]. References: [1] B. Dunn, et al., Science, 334(6058), 928-935 (2011) [2] Y. Huang, et al., ACS Energy Lett., 3(7), 1604-1612 (2018) [3] Q. Wang, et al., Nat. Mater., 20(3), 353-361 (2021) [4] M. Ben Yahia, et al., Nat. Mater., 18(5), 496-502 (2019). [5] A. Massaro, et al. ACS Energy Lett., 6, 2470-2480 (2021).

Resume : Generally accepted approaches for the electric energy production on base the nuclear technology includes an electrical yield use appeared in result of heavy nuclei disintegration, by application of the thermonuclear fusion, “cold” nuclear fusion at Pd and Ti atoms presence and in result of the beta decay. The thermonuclear technology intends to get over the Coulomb barrier by use the high-temperature plasma. This approach, in principle, allows to expect an appearing of nuclear power facility in future but its perspective is misty. The “cold” nuclear fusion is oriented on conditions search for the under barrier nuclear reaction procession in result of the tunneling effect. This approach was realized on practice but is characterized by very low efficiency and high unpredictability. At the same time, there is available the alternative approach to direct nuclear interaction realization allowed to evade the Coulomb interaction. It can be achieved on base of consecutives of the radiation fluxes waveguide-resonance propagation phenomenon in combination with the corpuscle-wave dualism principle use. The phenomenon of radiation fluxes waveguide-resonance propagation can be realized when radiation fluxes have possibility to excite in the propagation space the uniform interference field of radiation standing wave. Optical, X-ray and neutron quasimonochromatic radiation fluxes form these conditions when the width of its propagation space will be smaller as half of the radiations coherence length. The phenomenon peculiarities study showed that the interaction between independent radiation fluxes is possible in result of mutual influence of uniform interference fields excited by these fluxes. At the sane time, owing to the corpuscle-wave dualism atomic and molecular beams can excite principle similar uniform interference fields. By this means, one can get similar fields for atomic and molecular quasimonochromatic fluxes of hydrogen, deuterium, tritium and other elements and search of its interaction conditions. So, in frame of our paradigm the task of nuclear fusion reaction realization will be not connected with Coulomb barrier overcoming and will be directed on search of specific conditions for interaction of atomic and molecular beams through the mutual influence of uniform interference fields excited by these fluxes. Some peculiarities of the similar interaction is discussed in the report.