Materials for electrochemical storage systems for the electric vehicles

Resume : Due to their high energy and power density, excellent efficiencies and long life time lithium ion batteries have become the dominating energy storage technology for the new generation of Plug-in hybrid electric vehicles (PHEV) and full electric vehicles (EV). However, there is still considerable improvement needed to achieve extended driving range and to reduce significantly the cost of battery packs. For these reasons, the development of new high capacity, safe and lower cost cathode materials is necessary. State of the art is the use of layered oxides like LiCoO2, Li(Ni1/3Mn1/3Co1/3)O2 (NMC) and Li(Ni1-x-yCoxAly)O2 (NCA) or use of the more safe LiFePO4 with olivine structure. In order to further improve the specific capacity and to reduce the cost of the cathode material current research activities focus on the development of various compositions of LiNi1-x-yCoxMnyO2 with higher nickel content or on the development of so called HENMC with various compositions of solid solutions of Li2MnO3 and Li(Ni1/3Mn1/3Co1/3)O2. An alternative approach for further improvement of energy density is the development of high voltage cathode materials which are able to operate above 4.5 V vs. Li/Li+. The application of these cathodes leads to a higher cell voltage, resulting in higher energy density, lower costs and a lower complexity of the complete battery system. High voltage LiMn1.5Ni0.5O4 (LMNO) with spinel structure is one of the most promising candidates, because of the high operating voltage, high rate capability and good thermal stability. Moreover, it is easy to obtain via low cost synthesis methods from abundant raw materials. However, the high voltage can also lead to side reactions with the electrolyte, which cause impedance increase and capacity fading during cycling or storage especially in full cells using graphite as anode. The long term stability can be significantly improved by adjusting the composition, the particle morphology and by surface coating. It is possible to insert additional lithium into the spinel structure on a lower voltage plateau, which leads to additional specific capacity. The synthesis of Li2-xMn1.5-yMyNi0.5O4 (0≤x≤0.5) combine both the high voltage and the high specific capacity approach, reaching reversible capacities up to 280 mAhg-1. The presentation will summarize the state of the art of various positive active materials under development and highlight ongoing research developments and discuss perspectives and limitations.

Resume : Hard carbons (hereafter called HC) are choice materials for negative electrode purposes in sodium ion batteries due to their high specific capacities. However they show a cycling life limited to 300 cycles and charge/discharge curve profiles characterized by the presence of sloping regions at relatively high potential associated to the lithium insertion in the graphene layers. Nowadays a major effort has been devoted in determining the influence of HC textural properties on its electrochemical performance, analyzing samples obtained by pyrolisis at elevated temperature of organic compounds. Such studies are justified by major adsorption of sodium ions in the last step of the discharge curve, which should be enhanced by increasing the specific surface area. At our knowledge, influence of particle size has been somewhat missed in such studies. Thus, we have prepared a HC by pyrolising cellulose at 900°C and submitted the resulting powder to ballmilling for different periods. A number of electrochemical and physicochemical techniques allowed us to confirm that reducing the particle size in the same system provokes an increase in the electrolyte reduction comsuption during the cycling, creating thick solid electrolyte interfaces. Such films block the sodium ions adsorption. However a constant voltage step at the end of the discharge is efficient to save partly this drawback. From this results we propose in the second part of this presentation an electrochemical study of a composite based on optimised submicrometric HC and Ni-Sn nanoparticles in sodium half cell.

Resume : Sodium-ion batteries (SIBs) have been intensively investigated to meet the increasing demand for large-scale energy storage systems. However, it is still challenging to construct a functional full cell due to the limited material pool for both anodes and cathodes. Utilizing the wide range of vanadium redox states, herein, we report vanadium-based ortho-diphosphate, Na7V4(P2O7)4PO4 (or Na7VODP) as both cathode and anode active phases in a full-cell. The amphoteric nature allows Na7VODP to engage two vanadium redox couples, V3+/V4+ and V2+/V3+, for cathode and anode operations, respectively, within the stable voltage window of organic electrolytes. Na7VODP exhibits an activity at 1.01 V vs. Na/Na+ with a reversible capacity of 71.7 mAh g-1 and good capacity retention (80.5 % retention after 100 cycles). Through an Ex-situ X-ray photoemission spectroscopy (XPS), X-ray absorption near-edge structure (XANES) and In-situ synchrotron X-ray diffraction (XRD), it was revealed that Na7VODP reacts with Na ions based on a single-phase reaction in the low voltage range of 0.5 ~ 2.0 V by engaging V2+/V3+, in contrast with two biphasic reaction observed in the high voltage region of 2.0 ~ 4.2 V with V3+/V4+. Upon pairing into both electrodes, a Na7VODP full-cell shows an output voltage of 2.81 V.

Resume : Na-ion batteries (SIBs) are becoming an attractive alternative to Li-ion batteries because of their low cost owing to sodium abundance, geographical distribution and ease to process. Moreover, cheaper current collectors made of aluminium instead of copper can be used in both electrodes. While for cathode materials many lithium analogues can be successfully used in SIBs, [1] the challenge is to find alternative anode materials due to the impossibility of Na+ insertion into graphite and the formation of a stable SEI layer (Solid Electrolyte Interphase). Na2Ti3O7 negative electrode is the oxide with the lowest insertion voltage at 0.3 V vs. Na+/Na and delivers high specific capacity close to 200 mAh/g, [2] becoming a very promising anode candidate both in terms of energy density and cost. However, the reported capacity reaches only 50-70% after 10 cycles [3, 4, 5] therefore, the capacity retention needs to be improved. One of the important factors to take into account is the formation of a stable SEI layer since the reversible Na+ insertion/extraction occurs at low voltage and electrolyte reduction is expected. In order to understand the reasons behind the poor capacity retention, the SEI layer and kinetic transport properties have been studied by X-ray photoelectron spectroscopy (XPS) and Electrochemical Impedance Spectroscopy (EIS). Ex-situ XPS combined with depth profiling has allowed the study of the composition and stability of the SEI layer on Na2Ti3O7 electrode. Furthermore, the analysis of the Auger parameter has been used to accurately determine the composition without any interference from surface charging effects. [6] The study of the electronic and ionic transport has been carried out by EIS experiments. An interesting change of the transport properties, and particularly of electron conductivity, during the Na+ insertion/extraction process is revealed for the first time experimentally confirming recent DFT calculations. [4]. Moreover, the instability of the SEI layer has been also observed by EIS. The results obtained will be thoroughly discussed and strategies to overcome the poor capacity retention will be proposed. References: 1. V. Palomares, M. Casas-Cabanas, E. Castillo-Martínez, M.H. Man, T. Rojo, Energy Environ. Sci., 2013, 6, 2312-2337. 2. P. Senguttuvan, G. Rousse, V. Seznec, J.M. Tarascon, M.R. Palacín, Chem. Mater., 2011, 23, 4109-4111. 3. M. Zarrabeitia, E. Castillo-Martínez, J.M. López Del Amo, A. Eguía-Barrio, M.A. Muñoz-Márquez, T. Rojo, M. Casas-Cabanas, Acta Mater., 2016, 104, 125-130. 4. H. Pan, X. Lu, X. Yu, Y.S. Hu, H. Li, X.Q. Yang, L. Chen, Adv. Energy Mater., 2013, 3, 1186-1194. 5. A. Rudola, K. Saravanan, C.W Mason, P. Balaya, J. Mater. Chem. A, 2013, 1, 2653-2662. 6. M.A. Muñoz-Márquez, M. Zarrabeitia, E. Castillo-Martínez, A. Eguía-Barrio, T. Rojo, M. Casas-Cabanas, ACS Appl. Mater. Interfaces, 2015, 7, 7801-7808.

Resume : Lithium-Sulfur batteries (LiSB) are viewed as the future of Li-ion batteries for their high theoretical capacity and low-cost. However, some problems need to be addressed before LiSB can be commercialized. One of these issues is the formation of Li2S - an insulating and insoluble species - on the cathode upon discharge. Gaining a better understanding on the effect of materials electrodeposition at the electrode during discharge/charge is crucial for the development of LiSB. To this end, we have used electron microscopy to investigate the microstructural, crystallographic and chemical evolution of carbon nanoparticles, uniformly coated with amorphous sulfur, which were discharged at different rates (from 1C to 0.05C). Scanning Electron Microscopy highlights that the morphology of the discharge products is C-rate dependent, going from an amorphous phase at 1C to a crystalline, porous, desert-rose-like deposits at 0.05C. A careful analysis of the discharge products was performed by means of High- to Atomic- Resolution TEM associated with EELS. In the case of slow cycling, the discharge product crystalized as cubic Li2S nanocrystals up to 30 nm in size. They were observed either as isolated particles or aggregate clusters. These observations suggest that changing the discharge rate allows controlling the formation of Li2S from an amorphous to a crystalline phase.

Resume : The performance demands placed on batteries for the use in electrical mobility and portable devices are enormous. Cathode materials remain a bottleneck for the further increase on energy density. A promising candidate compound featuring low cost and high natural abundance is iron trifluoride (FeF3). It has been demonstrated that FeF3 intercalates lithium with near theoretical capacity of 237 mAh/g [1], also with promising rate capability [2]. However, there remains a strong need to develop low-cost synthesis methods for this material in a nanoscale form, needed for maximizing the performance. Herein, we show a new synthesis for nanocrystalline FeF3 based on a thermal decomposition of an organic precursor. Such inexpensive FeF3 can be charged and discharged in a lithium half-cell at a reversible capacity of 155 mAh/g within 1 min (10 A/g) or even faster. After 100 cycles, a capacity retention of 88 % has been achieved. In a sodium-ion half-cell, a capacity of 160 mAh/g at a current rate of 200 mAh/g could be measured. [1] Liu, J et al. Journal of Materials Chemistry A 2013, 1, 1969 [2] Ma, D. L. et al. Energy & Environmental Science 2012, 5, 8538

Resume : Future of portables devices, electric vehicles and smart grids demands long life and high energy density batteries. Li/S batteries – a post Li ion technology – provide a sound answer to such requests, as they offer high theoretical capacity (1675 Ah kg-1) and high energy density (2500 Wh kg-1). The development of Li/S system faces several challenges such as low degree of sulfur utilization, gradual capacity fading, poor rate capability and lower Coulombic efficiency mainly due to low conductivity of S (5 × 10−30 S cm−1), solubility of intermediate polysulfides, shuttling of polysulfides and lack of morphology restoration. One of the promising strategy is to encage S in conductive matrices to reduce polysulfides solubility while increasing the cathode electronic conductivity. A sustainable solution is proposed here to produce conductive carbon matrices from bio-based materials. Microporous carbons are manufactured by carbonizing β-cyclodextrin nanosponges and/or pea maltodextrin. Sulfur is incorporated via solvent impregnation and thermal diffusion. Then, the as prepared carbon-sulfur composite is wrapped with reduced graphene oxide or conductive polymers like polyaniline.. The obatained cathode material showed an initial discharge capacity of 1130 Ah Kg-1 at C/10, maintaining its capacity to 626 Ah Kg-1 at C/5 with capacity loss of 0.016% per cycle for more than 60 cycles.

Resume : Global warming and reduction of fossil-fuel supplies demand the pursuit of renewable energy sources and sustainable storage technologies. The rechargeable Li-air battery, coupling the light Li metal with the inexhaustible source of O2 of the surrounding air, represents an exciting opportunity. However, for many practical applications such as EV, air is the only viable option to supply the battery. In this context, moisture and gases other than O2 may cause side reactions and corrosion of the Li anode. We report a facile strategy to fabricate a highly effective O2 selective membrane based on highly hydrophobic fluorinated polymer and cyclodextrins. Several other major issues are responsible for the limited actual capacity and cycle ability. In principal, the high recharge potentials needed to decompose the insulating Li2O2 and the parasitic products formed from the electrolyte decomposition during cell discharge result in important energy losses. Palladium nanoparticles, due to the strength of O2 binding on the Pd surface, have very high intrinsic ORR activities in non-aqueous electrolytes. The use of carbon nanofibers (CNFs) as a support assures high surface area and high pores volume compared to other carbon-based materials. Pd doped mesoporous CNFs produced by electrospinning were used at the cathode of the Li-air pouch cell. Galvanostatic cycling tests in a potential/time controlled mode showed an outstanding cycling life superior to 1500h with more than 150 cycles.

Resume : Electric Vehicles symbolize the future of sustainable road transport. The ELIBAMA (European Li-Ion Battery Advanced Manufacturing) project had a duration of 3 years and came to an end in October 2014. The aim of this project was enhancing and accelerating the creation of a strong European automotive battery industry structured around industrial companies already committed to mass production of Li-ion cells and batteries for EVs. It was part of the European 7th Framework Program and of the European Green Cars Initiative, counting 17 partners - among which Daimler, Fraunhofer, Renault and Saft. It exploited eco-design methods of manufacturing battery cells, in order to guarantee gains in cost reduction and environment-friendliness across the value chain of the battery production. It main focus was the development of more eco-friendly processes for anode and cathode manufacturing (e.g. dry blend powder coating and aqueous based technologies), fast and homogenous electrolyte filling processes, cell design and assembly. Furthermore, it allowed developing new technologies to improve downstream quality, test the batteries and reduce the rate of defective products at the end of the manufacturing chain. The end-of-life for the Li-ion batteries was also considered within the scope of the project, where the pyrometallurgical process is state of the art, but other technologies involving hydrometallurgical processes are under development. The improvements were monitored and validated from the environmental point of view by an integrated assessment, using LCA methodology and considering the framework for eco-design. thinkstep (former PE INTERNATIONAL) undertook an independent assessment, playing the moderator role among the consortium partners and enhancing the communication from the different parts. Furthermore, thinkstep provided the battery manufacturers in the project with a flexible eco-design tool based on the data acquired during the project, in combination with GaBi databases and software, offering to these partners, the possibility of performing own internal assessments to the desired level of detail, without having to disclosure any additional information to third parties, avoiding the potential confidentiality issues which are a major challenge in this field. The methodology and framework used for performing the environmental integrated assessment of this project, allowing the identification of hotspots through the LCA, will be explained in this paper. The tool used by the partners to make their own environmental assessments will also be addressed, as an example of an approach to allow environmental screenings avoiding the need of providing information to third parties. The results from the project will be presented and discussed. The current status of the technologies developed and perspectives on potential further developments from the partners who participated in this project will be collected, analyzed and presented as an overview for the future.

Resume : Nowadays ambient temperature batteries gain worldwide interest as vital part required for long-time performance of various devices from portable electronics to electric and hybrid vehicles. Although lithium-ion batteries seems to be at the industrial stage novel systems which can replace them due to better capacity, longer lifetime economical and environmental issues are intensively studied. To this end not only novel electrode materials but also electrolytes are needed. In the present work some examples of strategies used to design new electrolytes from computational modeling via synthesis of electrolyte component up to examples of application in post lithium-ion batteries will be presented. The presentation will start from the development of novel salts (particularly anions) which plan to be used in electrolytes of possible multiple application. In our group in co-operation with CIC and Chalmers University various salts based on heterocyclic compounds with five-membered rings, such as 4,5-dicyanoimidazole or 4,5-dicyanotriazoles derivatives were obtained. In this presentation some recent results which enable us to design new liquid and polymeric electrolytes will be highlighted. Additionally the new class of ionic liquid systems in which lithium salt is introduced into the solution as a lithium cation−glyme solvate will be presented. This modification leads to the reorganisation of solution structure, what entails release of free mobile lithium cation solvate and hence

Resume : The development of all-solid-state electrochemical energy storage systems, such as lithium-ion batteries with solid electrolytes, requires stable, electronically insulating compounds with exceptionally high ionic conductivities. Considering oxides, garnet-type Li6La3Zr2O12 and derivatives, see Zr-exchanged Li6La3ZrTaO12 (LLZTO), have attracted great attention because of its high Li+ ionic conductivity of up to 10-3 S\cm-1. Despite numerous studies focusing on conductivities of powder samples, only a few use time-domain NMR methods to probe Li ion diffusion parameters in single crystals. Here we report, for the first time, on temperature-variable 7Li NMR relaxometry measurements using both laboratory and spin-lock techniques to probe Li jump rates in single crystalline Li-bearing garnets with high ion mobility. Time-domain NMR offers the possibility to study Li ion dynamics on both the short-range and long-range length scale. The techniques applied yield a fully consistent picture of correlated Li ion jump diffusion in LLZTO; the data perfectly mirror a modified BPP-type relaxation response being based on a Lorentzian-shaped relaxation function. The rates measured could be parameterized with a single set of diffusion parameters. Dynamic information about the elementary jump processes, such as jump rates and activation energies, was extracted from complete diffusion-induced rate peaks that are obtained when the relaxation rate is plotted vs inverse temperature.

Resume : The public acceptance of electric cars is generally influenced by an affordable, competitive pricing and an operating distance comparable or at least similar in size to that of nowadays used cars. Both factors are determined by the batteries used. Although lithium-ion batteries work quiet stable today, their capacity is not totally satisfying in respect of electric vehicles. To overcome these energy limitations, electrode materials with an increased specific capacity or/and cathode materials with a higher working potential are the two possible approaches. Both ideas are investigated in the eCaiman project funded by the European Union (H2020) which we would like to present here. A new graphite, optimized to be combined with an aqueous binder system, is under development. High voltage cathode and high capacity anode composites are synthesized and electrolyte components for 5 V battery systems are currently under development. In the present work we would also like to give a closer insight into the chemical interactions of high voltage cathode materials and carbonate based electrolytes when stressed by potentials beyond 4.5 V. The currently known electrolyte systems are known to be unstable and to decompose oxidatively at high potentials and cannot fulfil the demands of a 5 V battery system. Two electrolyte additives potentially known for their good high voltage properties are used for the investigations and the electrochemistry and the decomposition of the components is studied by GC-MS / IR techniques. A commercially available cathode material is used as a reference and compared to some high voltage spinel type LNMC materials, synthesized by project partners.

Resume : In Lithium-ion batteries, polymer electrolytes are preferred in order to meet all-solid-state requirements such as flexibility, leak-proof packing, processing feasibility etc. In this study, a polymer blend of 10 mol% PAA and 90 mol% PVA was optimized based on its thermal, mechanical and structural properties. The ionic liquid electrolyte, 0.2m PYRTFSI-LiTFSI was added to the polymer blend in different molar ratios. A maximum ionic conductivity of 1 mScm–1 is observed at 90 °C for the membrane with 70 mol-% IL. Cyclic voltammetry of the polymer electrolytes shows peaks corresponding to lithium stripping ( 0.3V vs Li /Li) and deposition (-0.32V vs Li /Li) process indicating the occurrence of highly reversible redox process. Linear sweep voltammetry of the polymer electrolyte reveals that they are stable up to 4.5 V, making these electrolytes suitable for high voltage cathode materials. A lithium transference number (tLi ) of 0.4 was determined for the polymer electrolytes by using chronoamperometry and impedance measurements. Galvanostatic charge-discharge studies of the polymer electrolytes in a lithium half-cell were tested with LiCoO2 as cathode, shows a capacity of about 100 mAh/g at 60 °C. The coin-type half-cell with 70 mol-% Il doped polymer electrolyte and LiFePO4 as cathode delivers a capacity of about 180 mAh/g. 1) Bruno Scrosati, et. al. (2010) J. Power Sources, 195(9) 2419. 2) Thayumanasundaram, S.et. al. (2015), Eur. J. Inorg. Chem., 2015 (7) 1290.

Resume : The motivation and advantages for using solid polymeric membranes as electrolytes in a lithium battery are to enhance endurance when varying electrode volume during life cycling, reduce reactivity with liquid electrolyte, improve safety and reach better shape flexibility. The basic requirements of a suitable electrolyte for electric vehicle battery are high ionic conductivity, low melting and high boiling points, electrochemical stability, and safety. In the study, the influence of different components on the polymer electrolyte was evaluated. Properties of fluorinated polymer electrolyte were studied using selected lithium salts and plasticizers. To achieve this goal, different polymer membranes were synthesised and characterised. The effect of different amounts of Lithium salt and plasticizer on the ionic conductivity of polymer membranes were tested. And, additionally, thermal stability and mechanical properties were also taken into account. The thermal properties were characterised by differential scanning calorimetry (DSC) in the temperature range of -90ºC- 200ºC, and thermogravimetric analysis (TGA) in the temperature range of 25-300 ºC. Tensile testing was performed with full scale forces in the range of 150N. Ionic conductivities of the polymer membranes were measured by electrochemical impedance spectroscopy (EIS), sandwiching a given polymer membrane between two blocking electrodes. Electrochemical stability of the membranes was also evaluated by linear sweep voltammetry (LSV) in the voltage range of 0-7 V (vs Li/Li+). Promising results were obtained for a polymer membrane based on PVdF-HFP matrix, LiPF6 as lithium salt, and a surfactant as plasticizer.

Resume : We studied the effect of different electrolyte additives such as vinyl carbonate (VC), succinic anhydride (SA), and lithium bis(oxalato)borate (LiBOB) on the electrochemical performance of Si slurry based anodes. The electrochemical behavior of composite electrode was evaluated through amperometric and and rate capability tests. The effect of electrolyte additives on the surface morphology of the Si/MC anodes was also studied using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) techniques. It was found that the various electrolyte compositions affect the formation and quality of Solid Electrolyte Interphase of electrodes in a distinct way. These phenomena and their impact on the cycling performance of mesoporous silicon anode will be demonstrated.

Resume : Li metal is considered as the “Holy Grail” of energy storage systems due to its extremely high theoretical specific capacity (3860 mAh g−1) and the lowest negative redox potential (−3.040 V vs. standard hydrogen electrode). The bright prospects give rise to worldwide interests in the metallic Li for the next generation energy storage systems, including highly considered rechargeable metallic Li batteries such as Li-O2 and Li-sulfur (Li–S) batteries. However, the formation of Li dendrites induced by inhomogeneous distribution of current density on the Li metal anode and the concentration gradient of Li ions at the electrolyte/electrode interface is a crucial issue that hinders the practical demonstration of high-energy-density metallic Li batteries. To suppress Li dendrite growth on the Li metal anode, we proposed several electrode designs: (a) A novel 3D nanostructured anode with metallic Li contained in fibrous Li7B6 matrix.[1] Comparing with other microstructured anode materials, the nanostructured anode is with a large specific area, which reduces the current density to suppress Li dendrite growth. Li deposits on the nanostructured anode with metallic Li embeded in fibrous Li7B6 matrix are always with smaller size than that on the plate Li metal anode. (b) A dual-phase Li metal anode containing polysulfide-induced SEI and nanostructured graphene framework.[2] Free-standing graphene foam provides several promising features as underneath layer for Li anode, including (1) relative larger surface area than 2D substrates to lower the real specific surface current density and the possibility of dendrite growth, (2) interconnected framework to support and recycle dead Li, and (3) good flexibility to sustain the volume fluctuation during repeated incorporation/extraction of Li. The synergy between the LiNO3 and polysulfides provides the feasibility to the formation of robust SEI in an ether-based electrolyte. (c) 3D reduced graphene oxide (rGO) with a very large SSA (1666 m2 g-1), pore volume (1.65 cm3 g-1), and electrical conductivity (435 S cm-1) as Li depositing framework.[3] Such unstacked graphene with huge SSA provides the feasibility to demonstrate the proof-of-concept of the regulation of Li depositing morphology through the ultralow local areal current density in LMBs. (d) 3D glass fiber (GF) cloths with large quantities of polar functional groups (Si-O, O-H, O-B) to realize uniform distribution of Li ions on Li metal anode and thus the dendrite-free Li deposits.[4] When GFs are introduced on the anode surface, the polar functional groups on the surface of GFs can adsorb considerable Li ions to compensate the electrostatic interactions between Li ions and protuberances of anode surface, avoiding the accumulation of Li ions around protuberances. The Li ions tend to evenly redistribute within the GF frameworks. Because the GF is nonconductive, Li ions can only epitaxially grow from former Li layer. Consequently, a dendrite-free morphology of Li deposits is achieved. Reference [1] Cheng X-B, Peng H-J, Huang J-Q, Wei F, and Zhang Q. Small 2014, 10, 4257. [2] Cheng X-B, Peng H-J, Huang J-Q, Zhang R, Zhao C-Z, and Zhang Q. ACS Nano 2015, 9, 6373. [3] Zhang R, Cheng X-B, Zhao C-Z, Peng H-J, Shi J-L, Huang J-Q, Wang J, Wei F, Zhang Q. Advanced Materials 2016, 28, 1504117. [4] Cheng X-B, Hou T-Z, Zhang R, Peng H-J, Zhao C-Z, Huang J-Q, Zhang Q. Advanced Materials 2016, 28, 1506124.

Resume : Rechargeable lithium ion batteries (LIB) as state of the art devices are considered as one of the most promising technologies to meet the challenges for future energy storage. Although such batteries gained commercial success, there are still some limitations in order to realize high-power requirements, especially for electric and hybrid electric vehicles. Here, we present a new concept of high-power LIB combining nanostructured active materials with a binder-free 3D current collector based on vertically aligned carbon nanotubes (VACNT) on metal foils. The benefit of this special material combination is found in low internal resistances what is the key issue for realizing high-power devices. This is achieved by using synthesis methods which assure very effective electrical contacting of active material with VACNT as well as VACNT with metallic current collector. Therefore, an atmospheric pressure CVD process is used for the direct growth of VACNT on metal foils. Subsequently in-situ growth of anode (LTO, lithium titanium oxide) and cathode material (LMO, lithium manganese oxide) on VACNT by a scalable chemical solution deposition is used. As a result impressive rate capabilities in half cells against lithium, e.g. 110 mAh/g at 300C for LTO, as well as in full cell setup for LTO/ LMO up to 60C are achieved. Consequently, the unique nanocomposite structure with its superior electrical conductivity make decorated VACNT a promising material for High-Power LIB.

Resume : This presentation will be focused on the materials and technologies developed within the European project MARS-EV (Grant Agreement n°609201) as well as the latest developments of Centre Technique du Papier, internally and in other selected projects. This new generation of cellulose-based packaging materials for pouch cells take the best advantages of cellulose (renewable material, non toxic, good weight/strength ratio) while greatly improving its barrier properties. The technologies include water-based coating of paper with polymers, grafting of materials’ surface with fatty acids by chromatogeny, and stratification of materials using micro-fibrillated cellulose (MFC) as barrier layer.

Resume : The electrospinning process consists in extruding a polymeric solution through a fine nozzle to which has been applied of a strong applied electric field. This process is able to provide nano-fibers having macroscopic lengths (micrometers) and at the same time, diameters ranging from a few tens of nanometers up to several micrometers. The outcome of the process is a non-woven composite structure. The artifacts obtained show unique properties such as high surface development, small fiber diameters, micrometric thickness, high permeability and low density. In the present study we report on the optimization of the electrospinning process and on the definition of an operating protocol able to provide reproducibly electrospun nanostructured polymeric membranes formed by different polymers like acid D,L-lactide (PDLLA), poly (ethylene oxide) (PEO), Poly (acrylonitrile) (PAN), Poly (vinyl alcohol), Poly(methyl-methacrylate) (PMMA) and Polyvinyl-pyrrolidone (PVP) loaded with particles of silicon oxide. The mats have been characterized by scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC).

Resume : The rapid development of electronic technologies makes every day more pressing the demand for long life, high energy and environmental friendly batteries. In this framework, wide research is in progress on cathode materials, because improving energy can’t occur without the implementation of higher voltage electrodes. Among the most promising materials, the lithium nickel manganese spinel (LMNO) deserves a special attention thanks to its environmental friendliness, low cost and interesting electrochemical performance. It has the operating voltage at 4.7V vs Li, high good electronic and lithium ion conductivities, it does not suffer of critical structural deformations upon cycling (e.g. no Jahn-Teller effect) and it has good thermal stability. The main weakness attributable to LMNO is related to its interaction with the electrolyte at high voltage, which can bring to corrosion reactions and electrolyte degradation, and finally to the progressive capacity fade. In the present study, LMNO spinel has been synthesized from oxides, according to an easy and cost effective mixed mechanochemical-ceramic solid-state route, also incorporating a synergic Cr- and Fe co-doping. In particular, High Energy Ball Milling (HEBM) has been used to mix and pretreat reagents, in order to improve powders reactivity and obtain the spinel phase with a finely tuned and very mild thermal treatment. This method allows an easy and reproducible synthesis with a quantitative final yield. The final optimized material is a disordered Fd-3m LMNO spinel doped with Fe(III) centres and coated with an amorphous Cr2O3 layer. This synthetic route produces a final material with a homogeneous morphology and exceptional electrochemical performances in terms of cycle life and rate capability.

Resume : Composite Li10SnP2S12 (LSPS) – polyethylene oxide (PEO) films, containing 25 to 50% polymer were electrophoretically deposited and tested as possible barrier materials for preventing leakage of polysulfides. It was found by XRD and XPS tests that saturation of LSPS-PEO films by LiI salt, followed by prolonged annealing at 90C, diminishes the crystallinity of neat LSPS and results in the formation of the novel composite: Li10+xSnIx P2S12/P(EO)3:LiI solid electrolyte (x<1). The high room-temperature ion conductivity of amorphous Li10+xSnIx P2S12 compound (0.1-0.3mS/cm) is restricted by slow ion transport via polymer electrolyte (PE) imbedded in ceramics and grain boundaries between PE and sulfide. Increase of polymer content and temperature improve total ion transport in the LISPS-PEO system. Conformal EPD coating of sulfur and lithium-sulfide cathodes by the developed composite electrolyte increased the reversible capacity and Faradaic efficiency of the Li/S and Li/Li2S cells, and enabled their operation at 60C. The study of a mixed electron-ion-conducting polysulfide barrier, which includes the effect of type and concentration of electron-conducting additives on the performance of sulfur and lithium-sulfide cells, will be addressed in the presentation. Acknowledgments This work is funded by EU HORIZON2020, HELIS Project, and by the Israel Academy of Science.

Resume : Sodium/air batteries have recently been studied as an alternative to lithium/air batteries. In spite of lower theoretical specific energy (1980Wh/kg of sodium vs. 3600Wh/kg of lithium), the abundance of sodium provides an advantage over lithium for its use as a metal anode. Sodium/air batteries have a problem of the reversibility of electrode reactions similar to that of lithium/air batteries. Applying an appropriate material as a cathode can contribute to the generation of more reversible products on charge, increasing the cyclability and reducing ORR and OER overpotentials of the battery. In this work, we studied ORR and OER in PEGDME500-based electrolytes, in the presence of Na+ ions, applying four types of carbon: glassy carbon, Black Pearl, SB and XC72R carbon. For this purpose, the three-electrode half-cell was used, utilizing the glassy-carbon electrode as the working electrode, which was tested as a stand-alone electrode, or alternatively was coated by the carbon, with a loading of ~100µg/cm2. It was found that, except for glassy carbon, all the other types of carbon showed very close reduction and oxidation overpotentials. The highest reduction and oxidation currents were obtained with the use of Black-Pearl carbon. Acknowledgments This work was funded by ISAEF and BSF foundations

Resume : The key rationale for the promotion of battery electric vehicles (BEVs) is to address the problems of emissions and resource depletion associated with current internal combustion engine (ICE) vehicles. It is therefore imperative that BEVs fulfil these objectives throughout their lifetime, meaning that the production, use and end of life (EoL) of their components must minimise impacts. Life cycle assessment (LCA) is a prominent technique used to evaluate the environmental impacts of a product system, from initial raw material acquisition, to final recycling and/or disposal. LCA is being used within the EU PF7 research project MARS-EV (Grant Agreement #609201) with a double goal: (i) to develop a baseline reference model for current-production batteries as commonly used in BEVs today; and (ii) to perform a prospective analysis of future improved battery concepts. We hereby present our preliminary impact assessment results for goal (i), and illustrate the main battery component types and related LCA model structure for goal (ii).

Resume : Due to the high theoretical specific energy (2500 Wh kg-1), Lithium-Sulfur batteries have attracted wide attention as next generation electrochemical energy storage. Main factors limiting their commercialization are the poor cycle life and low capacity retention. Actually the anode is composed by metallic Lithium, which is showing high capacity but low safety and durability. To reduce such issues, alternative anodes are studied, e.g. Silicon with high theoretical capacity (4200 mAh/g). However, Silicon is a semiconductor and presents high volume changes during cycling (up to 300%), causing electrode fractures and capacity fading. Here different silicon/graphene based composites with using reduced graphene oxide as electron conductor are presented. Silicon/graphene composites are obtained through hydrogel and polymer cross-linking methods. The morphological characterization shows a good interface between graphene sheets and the Silicon nanoparticles, so affecting positively the overall electron conductivity. The electrochemical performance in term of capacity and cycle life are promising in view of a possible application as anode both for Li-ion and Li-S cells.

Resume : The energy storage systems based on secondary zinc electrodes are potential candidates to fulfill the need for light weight and high discharge rate applications. The zinc anode has merits such as low cost, low toxicity, high specific energy, easy availability and ease of handling, which make it suitable for wide applications in alkaline battery systems. However, the commercialization of rechargeable zinc based energy storage systems has been hindered by the short cycle life of the zinc electrode usually limited by the corrosion and zinc dissolution (shape changes and dendrite growth) in the aqueous alkaline electrolytes [1]. In the last few years, many attempts have been made to develop modified zinc electrodes with reduced solubility of zinc discharge products. The majority have included the use of additives either to the electrode or to the electrolyte [2]. In this context, K. Miyazaki et al. were the first to report recently the mitigation of the dendrite formation of zinc electrodes by anion-exchange ionomers by means of modifying the surface of zinc electrode [3]. In this work high-performance Nafion® coated zinc particles as anode material for secondary zinc based energy storage systems has been obtained. The Nafion® coated zinc particles demonstrate superior electrochemical properties than the conventional zinc particles in terms of improved long term cycle life by reducing zinc dissolution which lead to a better reaction reversibility and a better inhibiting effect on shape change of the zinc anode. [1] Xu, M., et al., J. Power Sources, 283 (2015) 358-371. [2] S. J. Banik and R. Akolkar, Electrochimica Acta (2014). [3] K. Miyazaki, et al., Electrochemistry 80 (2012) 725-727.

Resume : The development of rechargeable batteries characterized by higher energy density, longer life-time and safety compared to the commercially available ones is under constant investigation. Improvements in electrode kinetics can be reached by using nanostructures, which are now developed thanks to the continuous progresses in terms of preparation methods. ZnO is potentially a promising anode system, alternative to alkali metals, because of very high theoretical capacity, low cost, chemical stability and reduced environmental impact. However, large volume changes upon cycling result in capacity fading and reduced lifetime. Here we show that strong improvements in ZnO electrochemical performances can be obtained by developing properly optimized nanoarctitectures. Variously nano-arrays, such as nanorods (1D structures), nanosheets (2D) and a hierarchical brush-like systems (3D), were prepared through hydrothermal synthesis and characterised in terms of physico-chemical and electrochemical properties. Results indicate that, among the investigated nanoarchitectures, the 2D systems are more performing due to the presence of small nanoparticles, with average diameter of about 10 nm, maximizing the array specific surface area and favoring the formation of the LiZn alloy. The additional application on such nanoparticles of a graphite coating preserves the morphology during cycling, and enables further improvement in terms of capacity retention and high rate (dis)charge capability.

Resume : The demand for high-energy storage systems is constantly increasing, as is the interest to explore alternatives to commercially available batteries. The rechargeable Li-O2 battery represents an exciting opportunity to design batteries that may satisfy some of the requirements of our future by coupling the light Li metal with the inexhaustible source of O2 of the surrounding air, resulting in high theoretical specific energy density. Clearly, the electrolyte plays a tremendous role on the performance of Li–O2 batteries, affecting the discharge capacity, the voltage gap, the recharge ability and so on. The continuous exploration of practical electrolytes is vital for developing high-performance Li–O2 batteries. The role of different solvents, namely DMSO, TEGDME and EMITFSI, on the cell electrochemical performance when coupled with pure carbon cathodes were compared. Moreover, in order to limit the side reactions at the cathode/electrolyte interface derived from the use of a totally carbon based cathode, homemade Co3O4 cathodes as well as Ru/RuOx nanoparticles supported on conductive indium tin oxide nanocrystals, as both the electro-catalyst and discharge product host, were studied. Electrochemical tests demonstrated how a synergistic electrolyte-catalyst choice improves long-term stability and significantly reduced charge overpotential, while retaining nearly 100% coulombic efficiency.

Resume : Sodium titanates represent promising anode materials in Na-ion batteries. In the present study we report about the hydrothermal synthesis and characterization of sodium titanates with respect to morphology and surface properties. The corresponding electrochemical performance as active material was tested in Na-ion half cells. To prepare the titanates, titanium(IV)oxide nanopowder was mixed with a 10 M sodium hydroxide solution; the resulting dispersion was then autoclaved at 165 °C. Different rising procedures were tested to obtain a product with enhanced specific capacity and durability. The titanate prepared can be described with an ordered rod-like structure; it reveals reversible capacities of up to 72 mAh g-1 at cycling rates of 40 mA g-1. The corresponding Coulombic efficiencies turned out to be 99.47 %. Interestingly, the efficiency rises with increasing cycle number. Cyclic voltammetry experiments, which were performed at various scan rates, showed that two reversible phases are formed during the preparation process. These two phases, referred to as high and low capacity phase, clearly possess different capabilities to store sodium ions. While the high-capacity phase, that is, Na2Ti3O7, shows reversible peaks from 0.2 to 0.5 V at currents of -0.15 to 0.15 mA, the cyclic voltammogram of the low-capacity phase, which is, most likely, Na2Ti6O13, is characterized by peaks at 0.79 and 0.9 V. As can be shown via a systematic study, the rinsing procedure affects the amount of Na2Ti3O7 formed.

Resume : Electrochemical behaviour and corrosion layers of carbone steel electrode, in the absence and presence of a synthesized tetra-phosphonic acid (TPA), namely (methylenbis(2-hydroxy-5,1 phenylene)) phosphonic acid in 3% NaCl medium were investigated by electrochemical impedance spectroscopy and The morphology of the thin film formed on the inhibited surface of carbone steel was examined using the scanning electron microscope. The addition of phosphonic acid leads to growth in diameter and size of the capacitive semicircle , which probably reflects physical blocking of the metal surface which indicates the formation of a thicker protective film and therefore reduced corrosion. SEM image in the presence TPA shows a large area free of corrosion products and reveals the formation of an inhibitor layer. The results show that the inhibitor has the ability of reducing the corrosion rate of ordinary steel in 3% NaCl.

Resume : A lot of scientific effort has been focused in the last years to obtain more advanced lithium ion batteries that are able to cycle for longer time. Nevertheless, special care must be taken into account during the management of the batteries. As it has been documented by several scientific publications, different factors (temperature, current rate and the working state of charge (SoC) window) might reduce the life of the cells considerably. Therefore, a correct use of the batteries is very significant to maximize the life of the cells. In particular, to identify the cell working SoC and to minimize the degradation caused by this phenomenon, a correct SoC and state of health (SoH) estimations are necessary. In this sense, this work has been focused on the development and comparison of different battery SoC and SoH estimator algorithms, applied to 15 Ah LiFePO4-Graphite pouch cell. The SoC has been estimated by using extended Kalman filters. Similarly, the state of health has been estimated using iterative transferred chare method, multiscale Kalman filtering, double Kalman filtering and analysing the charging voltage curve shape. The performance of the estimation algorithms has been evaluated at beginning of life, at mid-life and at end of life. Combining this correct lithium ion battery status monitoring with the aging degradation information (by additional aging test conducted off line) a battery life extension is looked forward by implementing a correct battery management system. Acknowledgement: Project financially supported by the European Commission (FP7) under Grant Agreement No. 609201.

Resume : The Chevrel phase family gathers a variety of chemical compounds MxMo6T8 in which M is a mono-, di- or trivalent element and T is a chalcogen. Discovered in early 70’s, they were mainly investigated for their superconducting or thermoelectric properties. A renewed interest has strongly grown due to their ability of reversibly intercalating mono- or multi-valent cations, and thus as electrode materials for rechargeable battery. Mo6S8 is the positive electrode material used in the first rechargeable Mg battery prototype proposed by the group of Aurbach back in 2000. In this pioneering work, Mo6S8 showed a stable capacity during reversible Mg2+ ions intercalation (60 mAh g-1 for almost 600 cycles). Despite many attempts to find more performing cathodes materials, it is still the reference for positive electrodes in Mg-ion systems. However, this phase cannot be synthetized via a direct route, and is commonly obtained by acidic leaching of the ternary compound Cu2Mo6S8. Herein, Cu2Mo6S8 was successfully synthetized using a simple and cost-effective solid-state microwave-assisted reaction. Contrary to the conventional synthetic routes which requires several days of high temperature treatment under inert atmosphere, the microwave-assisted method allows obtaining the phase after only 400 s using a simplified setup in open air, in addition without any major impurity. The derived binary phase Mo6S8, easily obtained after an acidic treatment, was therefore conditioned and tested as a positive electrode material for Mg batteries, providing electrochemical performance in line with those of the material synthesized via the conventional route.

Resume : Nuclear magnetic resonance (NMR) can reveal the nature of ionic motion from molecular rotation, as probed by T1 measurements, to long-range self-diffusion via pulsed gradient spin echo (PGSE) methods. The dynamic range of standard T1 measurements is restricted to a few fixed spectrometer frequencies and broadband relaxometry based on Fast Field Cycling NMR (FFCNMR) methods can considerably expand this range, spanning three to four orders of magnitude in frequency in a single set of measurements. Our group also employs pressure as a thermodynamic variable, in which it is possible to gain new insight into cooperative motional processes characteristic of large flexible ions in ionic liquid (IL)- based electrolytes. Coupled with other characterization tools such as ionic conductivity, these methods provide valuable insight into charge and mass transport mechanisms. The results of several studies of novel Li battery electrolytes in collaboration with other groups will be discussed. In collaboration with the group of S. Passerini (Helmholtz Institute, Ulm) we present preliminary variable pressure and FFCNMR relaxation results for a family of pyrrolidinium-TFSI (Pyrr-TFSI) ionic liquids, in which the chain length on the Pyrr cations was varied between 3 and 9 carbons, and to which LiTFSI has been added. In collaboration with the group of N. Balsara (U.C. Berkeley), we investigate transport properties of novel fluorinated liquid Li electrolytes via standard pulsed gradient NMR and FFCNMR. Of particular interest is the extraction of meaningful cation transference numbers in the presence of strong ion association.

Resume : We have investigated the transition of electronic structures of nano-structured electrodes in all-solid-state metal-oxide thin-film batteries. Two metal oxide layers: a NiO thin layer and a TiO2-SiO2 nano-composite layer are stacked and sandwiched between current collectors. The nano-composite layer consists of a highly porous mixture of nano-scaled TiO2 and SiO2. A similar device has been reported as a “physical battery” but the mechanism of its operation was unclear. In order to clarify this, the electron energy-loss near-edge structures (ELNES) of Ni, Ti and O were evaluated by TEM-EELS analysis with high spatial resolution. The EELS spectra were, then, compared between the states before and after electrical charging. We found that the Ni-L3 edge in NiO layer seemed to be shifted to the higher energy side and slightly broadened by the charging process. This suggests that the NiO is oxidized in charging and act as a positive electrode. On the other hand, the Ti-L2,3 white-line in the nano-composite layers was shifted to the lower energy side, where both Ti-L2 and L3 lines have split into two peaks after charging. This suggests crystallization and/or partial reduction of the nano-structured TiO2, acting as a negative electrode. Our findings demonstrate that this type of thin film battery operates by the chemical redox reaction rather than the physical charge accumulation. The detailed reactions involving proton in each electrode will be discussed with the results by the first principles calculation.

Resume : A new methodology of contrast enhancement for multi modal 3D imaging, including novel advanced quantification, on a commercial Lithium Iron Phosphate (LFP) LiFePO4 cathode is presented. The aim of this work is to improve the quality of the 3D imaging of challenging battery materials by developing methods to increase contrast between otherwise previously poorly differentiated phases. In this study we present a novel method of sample preparation with a new type of epoxy impregnation, brominated (Br) epoxy, which is introduced here for the first time for this purpose and found suitable for multi modal imaging, for both focused ion beam scanning electron microscope (FIB-SEM) tomography and X-ray micro tomography. The Br epoxy improves image contrast, which enables higher FIB-SEM resolution (3D imaging), which is amongst the highest ever reported for composite LFP cathodes using FIB-SEM. In turn it means that the particles are well defined and the size distribution of each phase can be analysed accurately from the complex 3D electrode microstructure using advanced quantification algorithms.

Resume : Silicon microwires represent novel and promising candidates for high capacity anodes in Li-ion batteries (LIB). Their enormous surface to volume ratio which is essential for ion storage enables a capacity of up to 4200 mAh/g which is about ten times higher than for recent carbon anodes. Within this project structural changes and degradation of silicon microwires during (de-)lithiation are being characterized by ex situ transmission electron microscopy (TEM). Uncycled raw silicon wires showed overall high crystallinity but during charging their volume expands about a factor of four and a SEI (solid electrolyte interface) and intermediate LiSi-phases form. Sophisticated cross-sectional preparation of cycled wires has been performed for an investigation of crystallinity combined with the extension of the amorphous SEI. Aside from the anode the Li-rich Li4.1Si phase has been characterized for the first time by TEM methods showing planar defects representing barriers for the Li-ion transport and subsequently decreasing the anodes´ capacity. Challenging sample preparation is a key point to achieve electron transparent samples from the µm-sized wires. Methods include focused ion beam (FIB) technique, ultramicrotomy to access the interior part of the wires for TEM. Further preparation under inert gas atmosphere as well as transfer to TEM in argon atmosphere was optimized to handle reactive Li-containing samples.

Resume : Electrochemical systems are being thought as the solution for the vast demand for high energy density in both portable and stationary devices. Such systems hold a great promise, while pressure on researchers grows as the need for more “juice” in mobile device (from small hand held electronic to large mobile systems as EV) dramatically increase as technology is rapidly evolving. In this talk, we will address both the anode and cathode materials in advanced Li-ion batteries. Lightweight, loaded and flexible electrode construction materials will be discussed in this talk.

Resume : Scientific literature about modelling, especially physics based models, abounds in discharge models for lithium ion batteries. However charge models have received much less attention. Every secondary lithium batteries undergo multiple charge as well as discharge cycles. Vehicles with electric traction usually come with regenerative braking, wherein a battery is subjected to very transient conditions and high charge rates. Moreover, fast charging remains one of the most important factors in electric traction vehicle adoption. One reason for this lack of focus on charge models is that the same set of parameters is assumed to be valid for both charging and discharging. In this work, this hypothesis is tested and a charge model is developed starting with a validated physics based discharge model of a lithium iron phosphate – graphite battery. This validated discharged model is first reversed to get the charge model and is then compared against experiments. It is seen that this model needs to be modified to represent the actual charging behaviour. This process of adapting the model is described in the work. Finally after optimizing the charge model, the parameters that give rise to the different electrochemical and thermal behaviour in these two models are compared and analysed for the differences and similarities. Focus on differences in the heat generation of these models is emphasized because of its importance in designing proper heat management systems for batteries. In particular, it is shown that in the development of the charge model, consideration of hysteresis effect and charge dependent radius is critical.

Resume : Aging of lithium ion batteries during usage leads to capacity- and power fade. Thus, aging modifies the internal cell properties as a function of the time and usage parameters. In the framework of the large-scale EU-project “Materials for Ageing Resistant Li-ion High Energy Storage for the Electric Vehicle” (MARS-EV), extensive aging tests for studying the degradation of commercial high-energy lithium ion cells have been carried out at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg (Germany). The goal is to implement an aging model into a Particle filter used for precise state of charge estimation. The tests are divided into calendric and cycle ageing test. Cycle tests were carried out for different ambient temperatures, cycle current amplitudes and depth of discharge while for storage tests the state of charge and the ambient temperature were variated. The characterization of the cells at different aging stages was done with a wide range of electrical characterization methods like electrochemical impedance spectroscopy, capacity tests, open circuit voltage measurements and pulse-power tests. Thereby the influence of external aging conditions on the degradation of the cell parameters could be investigated. At a late stage in battery life, an accelerated capacity decrease was observed. In this talk we present an aging model dependent on the usage parameters. Additionally we show the parametrization of a dynamic equivalent circuit model using impedance spectroscopy measurements as well as pulse-power test in time domain. The resulting electrical model was implemented in an algorithm using Particle filter for state-of-charge estimation. The accuracy and precision of the electrical model and the state-of-charge estimator could be verified by comparing simulations and measurements. Current profiles typical for electric vehicles have been tested for this purpose.