The family of layered materials currently attracting most interest for practical applications is that of Li and Mn-rich Li 1+x M 1-x O 2 layered oxides, with the overall Li/M ratio >1, M being Mn, Ni and Co 3d transition metals. Indeed, they offer very high reversible capacities (> 230 mAh/g) and the composition rich in manganese fulfills sustainability, availability and cost issues. The exceptional capacity delivered by these layered oxides is in fact explained by the reversible participation of oxygen anions to the redox processes. [1-4] This reaction is reversible within the bulk, occurring without any major structural modification, whereas oxidized oxygen ions are destabilized at the surface, leading to oxygen loss and structural reorganization at the outer part of the particle. [5-6] This structural reorganization is at the origin of a voltage profile evolution upon cycling and of a continuous decrease in energy, and its kinetics is obviously highly dependent on the composition of the pristine material. [7] The challenge in the field is now to develop alternative compounds with low cost and environmentally friendly metals being able to promote the participation of oxygen anions in the redox processes, with optimized and stabilized electrochemical performance over long range cycling. A large number of compositions are currently under study in our group at ICMCB, screening the composition in transition metal ions in a series of materials Li(Ni II Mn IV x+3y Co III 1-2(x+2y) )O 2 recently reported to stabilize cationic vacancies on the transition metal sites ( i.e. in the slabs). [8-10] We focused our efforts on compositions showing a Li/M ratio ranging between 1 and 1.5 and a Mn content being at least 45 at.% of M, as they deliver very attractive reversible capacities with a limited first cycle irreversible capacity. The phase diagram was established as function of the M composition and of the Li/M ratio using the combination of Synchrotron X-ray and neutron powder diffraction analyses. During this presentation, we will discuss in details the relationship between the synthesis conditions, the composition, the structure and the electrochemical performance of these materials, but also the subtle differences identified in the structural modifications observed in different cycling conditions to determine the optimized formation of the electrode material for its cyclability upon long range cycling. Acknowledgments The authors thank Cathy Denage, Laëtitia Etienne and Eric Lebraud (ICMCB) for SEM, ICP-OES and routine XRD analyses respectively, as well as the ANR and DGA for the funding of the project SILMARILION ANR-16-CE05-0015-02. References [1] H. Koga, L. Croguennec, M. Ménétrier, Ph. Mannessiez, F. Weill, C. Delmas, J. Power Sources 2013 , 236, 250 [2] H. Koga, L. Croguennec, M. Ménétrier, K. Douhil, S. Belin, L. Bourgeois, E. Suard, F. Weill, C. Delmas, J. Electrochem. Soc. 2013 , 160(6) , A786 [3] M. Sathiya, K. Ramesha, G. Rousse, D. Foix, D. Gonbeau, A.S. Prakash, M.L. Doublet, K. Hemalatha, J.-M. Tarascon, Chem. Mater. 2013 , 25 , 1121 [4] M. Sathiya, G. Rousse, K. Ramesha, C.P. Laisa, H. Vezin, M.T. Sougrati, M.L. Doublet, D. Foix, D. Gonbeau, W. Walker, A.S. Prakash, M. Ben Hassine, L. Dupont, J-M. Tarascon, Nat. Mater. 2013 , 12 , 827 [5] A. Boulineau, L. Simonin, J.-F. Colin, C. Bourbon, S. Patoux, Nano Lett. 2013 , 13 , 3857 [6] C. Genevois, H. Koga, L. Croguennec, M. Ménétrier, C. Delmas, F. Weill, J. Phys. Chem. C 2015 , 119 (1), 75 [7] M. Sathiya, A.M. Abakumov, D. Foix, G. Rousse, K. Ramesha, H. Vezin, C.P. Laisa, A. Prakash, D. Gonbeau, M. Saubanère, M.-L. Doublet, G. VanTendeloo, J.-M. Tarascon, Nat. Mater. 2015 , 14 , 230 [8] E. McCalla, A.W. Rowe, J. Camardese, J. R. Dahn, Chem. Mater. 2013 , 25, 2716 [9] R. Shunmugasundaram, R.S. Arumugam, J.R. Dahn, Chem. Mater. 2015 , 27, 757 [10] R. Shunmugasundaram, R. S. Arumugam, K. J. Harris, G. R. Goward, J. R. Dahn, Chem. Mater. 2016 , 26, 55

The lithium and lithium-ion battery electrode chemical stability in the pristine state has rarely been considered as a function of the binder choice and the electrode processing. In this work, X-ray photoelectron spectroscopy (XPS) and XPS imaging analyses associated with complementary Mössbauer spectroscopy are used in order to study the chemical stability of two pristine positive electrodes: (i) an extruded LiFePO4-based electrode formulated with different polymer matrices [polyethylene oxide and a polyvinylidene difluoride (PVdF)] and processed at different temperatures (90 and 130 °C, respectively) and (ii) a Li[Ni0.5Mn0.3Co0.2]O2 (NMC)-based electrode processed by tape-casting, followed by a mild or heavy calendering treatment. These analyses have allowed the identification of reactivity mechanisms at the interface of the active material and the polymer in the case of PVdF-based electrodes.

In article number 1701988, Joël Gaubicher, Philippe Poizot, Fabrice Odobel and co-workers report the first ever battery material that works with simultaneous uptake and release of both cations and anions. This represents one of a new family of organic electrode materials that shows great promise, thereby promoting the design of cutting-edge, low-cost, rocking-chair dual-ion aqueous batteries.

Among the candidates as negative electrode, silicon is now one of the most attractive alternatives to graphite and has been the subject of many investigations for the past decade. The commercialization of Si electrodes is nevertheless blocked by the inability to overcome the mechanical degradation and electrolyte consumption occurring as a result of the inherent volume expansion upon silicon alloying. The unique combination of their properties renders ionic liquids very attractive and promising candidates to replace the benchmark organic carbonates and could enable an enhanced control of species constituting the solid-electrolyte interface (SEI). In the present study, evolutions of ionic liquid based electrolytes (pure ionic liquid and ionic liquid/carbonate mixes) and the subsequently formed SEI are monitored upon aging and cycling in full Li-ion cells using nonprelithiated silicon electrodes. X-ray photoelectron spectroscopy, typically probing the first few nm of the surface of the sample, allowed monitoring of the evolution and possible degradation of the ionic liquid based electrolytes upon aging and cycling of complete Si/NMC batteries. Magic angle spinning NMR combined with scanning transmission electron microscopy-electron energy loss spectroscopy is more sensitive to changes occurring in the SEI composition. The degradation of ionic liquid components PYR13 and TFSI is evidenced and their influence on the formation of species at the surface of the silicon electrode clearly observed. However, the presence of the ionic liquid components does not prevent the degradation of carbonates in the parasitic reactions that are consuming the cyclable lithium. Therefore, the failure mechanism scenario is similar to that observed for the full cell using benchmark carbonate electrolytes. Hazard level assessments nevertheless reveal that the addition of ionic liquids is in fact able to moderate the intensity of safety relevant events and improve the cell safety.

•Thiophene is grafted to silicon to allow for intimate contact.•Modification with the thiophene layer acts as a pre-existing SEI layer.•The thiophene layer results in improved cycle life.•Further improvements will be possible by forming conducting polymer composites.

The failure mechanism of silicon-based electrodes has been studied only in a half-cell configuration so far. Here, a combination of 7Li, 19F MAS NMR, XPS, TOF-SIMS, and STEM-EELS, provides an in-depth characterization of the solid electrolyte interphase (SEI) formation on the surface of silicon and its evolution upon aging and cycling with LiNi1/3Mn1/3Co1/3O2 as the positive electrode in a full Li-ion cell configuration. This multiprobe approach indicates that the electrolyte degradation process observed in the case of full Li-ion cells exhibits many similarities to what has been observed in the case of half-cells in previous works, in particular during the early stages of the cycling. Like in the case of Si/Li half-cells, the development of the inorganic part of the SEI mostly occurs during the early stage of cycling while an incessant degradation of the organic solvents of the electrolyte occurs upon cycling. However, for extended cycling, all the lithium available for cycling is consumed because of parasitic reactions and is either trapped in an intermediate part of the SEI or in the electrolyte. This nevertheless does not prevent the further degradation of the organic electrolyte solvents, leading to the formation of lithium-free organic degradation products at the extreme surface of the SEI. At this point, without any available lithium left, the cell cannot function properly anymore. Cycled positive and negative electrodes do not show any sign of particles disconnection or clogging of their porosity by electrolyte degradation products and can still function in half-cell configuration. The failure mechanism for full Li-ion cells appears then very different from that known for half-cells and is clearly due to a lack of cyclable lithium because of parasitic reactions occurring before the accumulation of electrolyte degradation products clogs the porosity of the composite electrode or disconnects the active material particles.

Understanding the aging mechanism of silicon-based negative electrodes for lithium-ion batteries upon cycling is essential to solve the problem of low coulombic efficiency and capacity fading and further to implement this new high-capacity material in commercial cells. Nevertheless, such studies have so far focused on half cells in which silicon is cycled versus an infinite reservoir of lithium. In the present work, the aging mechanism of silicon-based electrodes is studied upon cycling in a full Li-ion cell configuration with LiCoO2 as the positive electrode. Postmortem analyses of both electrodes clearly indicate that neither one of them contains lithium and that no discernible degradation results from the cycling. The aging mechanism can be explained by the reduction of solvent molecules. Electrons extracted from the positive electrode are responsible for an internal imbalance in the cell, which results in progressive slippage of the electrodes and reduces the compositional range of cyclable lithium ions for both electrodes.

Continuous solid electrolyte interface (SEI) formation remains the limiting factor of the lifetime of silicon nanoparticles (SiNPs) based negative electrodes. Methods that could provide clear diagnosis of the electrode degradation are of utmost necessity to streamline further developments. We demonstrate that electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM can be used to quickly map SEI components and quantify LixSi alloys from single experiments with resolutions down to 5 nm. Exploiting the low-loss part of the EEL spectrum allowed us to circumvent the degradation phenomena that have so far crippled the application of this technique on such beam-sensitive compounds. Our results provide unprecedented insight into silicon aging mechanisms in full cell configuration. We observe the morphology of the SEI to be extremely heterogeneous at the particle scale but with clear chemical evolutions with extended cycling coming from both SEI accumulation and a transition from lithium-rich carbonate-like compounds to lithium-poor ones. Thanks to the retrieval of several results from a single data set we were able to correlate local discrepancies in lithiation to the initial crystallinity of silicon as well as to the local SEI chemistry and morphology. This study emphasizes how initial heterogeneities in the percolating electronic network and the porosity affect SiNPs aggregates along cycling. These findings pinpoint the crucial role of an optimized formulation in silicon-based thick electrodes.

ELECTRODES IN FULL LI-ION CELLS Lucille Quazuguel, Nicolas Dupré, Philippe Moreau, Christian Rudish, Julien Danet, Maxime Boniface, Eric De Vito, Sandrine Lyonnard, Pascale Bayle Guillemaud and Dominique Guyomard 1 Institut des matériaux Jean Rouxel (IMN), Université de Nantes-CNRS, 2 rue de la Houssinière, 44322 Nantes, France 2 Commissariat à l’énergie atomique et aux énergies alternatives (CEA), INAC, F-38054 Grenoble 9, France

Sodium-ion batteries (SIB) are considered as an attractive alternative to lithium-ion batteries (LIB) as they could potentially be much less expensive, safer, and environmentally friendlier[1]. Clearly, one of the major concerns that we are currently faced with consists in determining to what extent the results gathered over the past twenty years in the Li battery field, can be transferred to the Na one. Our research directly addresses this issue by highlighting two facts: 1-The Na intercalation process in FePO4 is significantly different from the Li one with the existence of a stable intermediate composition Na2/3FePO4.[2],[3],[4],[5] By combining electronic and X-Ray synchrotron radiation diffractions as well as Mössbauer and NMR spectroscopies, we identified the intermediate phase as a fully ordered Na2/3FePO4 composition showing a vacancy ordering along the channels coupled with a FeII/FeIII charge ordering. Thanks to ab initio DFT calculations a very good agreement between all analytical methods was found and definitely confirms the good assignment of the superstructure.[6] 2-Contrary to what has hitherto been observed for Li batteries, the thermodynamic phase diagram of FePO4[3] needs thorough reassessment as far as the dynamic intercalation/deintercalation of Na ions within a cycling battery is concerned. Indeed, based on operando synchrotron X-Ray diffraction, we show that structural phase transformation does not proceed at constant composition. Instead, we witnessed the occurrence of vastly extended limits of solubility, which are characterized by continuous variations in the lattice metric mirroring that of the Na occupancy. This striking result[7], hitherto unseen in material science, to our knowledge, results in Na batteries having an enormous advantage over Li ones, since the lattice volume mismatch during phase transformation is reduced by a factor of 30% and 10% on charge and discharge, respectively when compared to what is predicted based on the thermodynamic phase diagram. Kinetically controlled structural behavior such as this could clearly compensate for the less efficient Na-related SEI, as well as the larger size of Na ions compared to Li ones. We anticipate the elucidation of further noteworthy examples pertaining to the influence of dynamics on the structural behavior of positive and especially negative electrode materials of Na batteries in the near future. In light of these findings the Na intercalation process in FePO4 will be discussed. [1] Ellis, B. L. & Nazar, L. F. Current Opinion in Solid State & Materials Science, 2012, 16, 168-177 [2] Moreau, P.; Guyomard, D.; Gaubicher, J.; Boucher, F. Chem Mater 2010, 22, 4126–4128. [3] Casas-Cabanas, M.; Roddatis, V. V.; Saurel, D.; Kubiak, P.; Carretero-Gonzalez, J.; Palomares, V.; Serras, P.; Rojo, T. J Mater Chem 2012, 22, 17421–17423. [4] Lu, J.; Chung, S. C.; Nishimura, S.; Oyama, G.; Yamada, A. Chemistry of Materials 2013, 25, 4557–4565. [5] Zaghib, K.; Trottier, J.; Hovington, P.; Brochu, F.; Guerfi, A.; Mauger, A.; Julien, C. M. J Power Sources, 2011, 196, 9612-9617 [6] Boucher, F. ; Gaubicher J.; Guyomard D. ; Moreau, P., Chem. Mat., submitted [7] Gaubicher, J.; Boucher, F.; Moreau, P.; Cuisinier, M.; Soudan, P.; Elkaim, E.; Guyomard, D. Electrochem Commun, 2014, 38, 104-106

Because of the large energy separation between O-K and Mo-L2,3 edges, extracting precise and reliable chemical information from core-loss EELS analyze of molybdenum oxides has always been a challenge. In this regard Mo-M2,3 edges represents an interesting alternative as they are situated close to the O-K edges. They should allow thus the extraction of a wealth of chemical information from the same spectra. However the main difficulty to overcome in order to work properly with these edges is the delayed maxima of the Mo-M4,5 edges which hinders the automated background subtraction with the usual inverse power low function. In this study we propose another background subtraction method specifically designed to overcome this obstacle and we apply it to the study of MoO3 and MoO2. We are able to show that quantitative chemical information can be precisely and accurately determined from the joined analyze of O-K and Mo-M2,3 edges. In particular k-factors are derived as a function of the integration window width and standard errors close to 2% are reported. The possibility to discriminate the two oxides thanks to chemical shifts and energy-loss near-edge structures is also investigated and discussed. Furthermore the M3/M2 ratios are derived and are found to be strongly dependent on the local chemical environment. This result is confirmed by multiplet calculations for which the crystal field parameters have been determined by ab initio calculations. The whole methodology as well as the conclusions presented in this paper should be easily transposable to any transitions metal oxides of the 4d family. This work should open a new and easier way regarding the quantitative EELS analyses of these compounds.

A pluri-disciplinary approach and a combination of techniques are used here to finely describe the surface of silicon nanoparticles used as active material in negative composite electrodes for lithium batteries. Although the surface of silicon particles is playing a major role in the electrochemical performance, it has rarely been characterized in depth. With respect to infrared analysis, we propose an analytical protocol, derived from the studies devoted to high specific area silica samples. Three different nanometric silicon powders are studied: a commercial one and two home synthesized silicon powders with specially designed surfaces. With respect to previous works and common belief, we demonstrate, on the electrochemical performance, a favorable effect of a particular thin layer silicon oxide with a well-defined SiO2 composition at the extreme surface of the silicon particles.

The surface chemistry of aged Li4Ti5O12 and LiFePO4 electrodes that have been cycled in a full cell configuration are examined using nuclear magnetic resonance. The failure mechanism of such cells has been previously identified to be an electrode capacity slippage process caused by the loss of charge carriers: electrons or lithium ions. The electrode-electrolyte interphase is quantitatively analyzed after cycling thanks to a calibration of NMR spectra. LiF is detected at both electrodes: about 1.2 mu mol mg(-1) at the Li4Ti5O12-based electrode and about 0.35 mu mol mg(-1) at the LiFePO4-based electrode, and it is the main component amongst lithiated species. By comparison with gravimetric studies, LiF cannot be the only component of the interphase. From a correlation between the amount of detected LiF and the electrode capacity slippage of the battery, different reaction paths are proposed at each electrode, involving either moisture-driven catalysis or reductive process that consumes a quantity of charge from the electrode. (C) 2014 Elsevier Ltd. All rights reserved.

The morphological and the electrical properties of carbon coated LiFePO4 (LFPC) active material functionalized by 4-ethynylbenzene tetrafluoroboratediazonium salt were investigated. For this purpose, FTIR, Raman, XPS, High Resolution Transmission Electron Microscopy (HRTEM) and Broadband Dielectric Spectroscopy (BDS) were considered. Electronic conductivities of LFPC samples at room temperature were found to decrease in a large frequency range upon simple immersion in polar solvents and to decrease further upon functionalization. Due to their high dipole moment, strongly physisorbed molecules detected by XPS likely add barriers to electron hopping. Significant alteration of the carbon coating conductivity was only observed, however, upon functionalization. This effect is most presumably associated with an increase in the sp(3) content determined by Raman spectroscopy, which is a strong indication of the formation of a covalent bond between the organic layer and the carbon coating. In this case, the electron flux appears to be redirected and relayed by short-range (intra chain) and long-range (inter chain) electron transport through molecular oligomers anchored at the LFPC surface. The latter are controlled by tunnelling and slightly activated hopping, which enable higher conductivity at low temperature (T < 250 K). Alteration of the electron transport within the carbon coating also allows detection of a relaxation phenomenon that corresponds to small polaron hopping in bulk LiFePO4. XPS and HRTEM images allow a clear correlation of these findings with the island type oligomeric structure of grafted molecules.

This study conveys striking findings regarding the operando structural behavior of the Na/FePO4 system during a charge and discharge cycle. From Rietveld refinements of synchrotron operando X-ray diffraction data, it appears that the active material presents large, non-stoichiometric domains while undergoing structural phase transformation. The corresponding extended limits of solubility are characterized by continuous variations in the metrics that mirror the entry of Na occupancy values into thermodynamically forbidden regions. A major consequence of this smoothed phase transformation is a significant decrease in the lattice volume mismatch, which could well compensate for the less efficient Na-based systems with respect to SEI and adverse effect of cation size in comparison to Li batteries. Comparison of the lattice volume mismatch on charge and discharge revealed an explanation for the asymmetry of the electrochemical curve.

For the last 10 years, a tremendous amount of work has been published to solve the problem of capacity fade of silicon-based electrodes which prevents their utilization in commercial lithium-ion batteries. The use of Si nanoparticles/nanowires to better accommodate large strain without cracking has developed and is very popular in the academic community. By playing on the nano-architecturing effect or tailoring the composite electrode formulation, several groups have reached up to 1000 cycles in half-cells versus lithium metal [1,2]. However, a careful look at the papers shows that in all studies the active mass loading is very low, typically less than 1 mg per cm², and thus the practical surface capacity of the corresponding electrodes is low, typically less than 1 mAh per cm². This is much lower than that of the state of the art graphite-based negative electrode, which reaches up to 5 mAh per cm² in cellular phones for example. As a consequence, although silicon is much more attractive than graphite due to its very high gravimetric capacity (3572 mAh g-1 versus 372 mAh g-1 for graphite) and volumetric capacity (2249 versus 779 mAh cm-3 for graphite), Si-based composite electrodes show lower practical surface capacity, as a matter of fact. The point is that the cycle life of Si-based electrodes dramatically decreases as the active mass loading increases, e.g. 1000 cycles at 0.5 mg per cm² vs. 50 cycles at 4 mg per cm² (Figure 1). We demonstrated that using copper foam instead of copper foil as current collector shows a great advantage in the cycle life and power performance. More than 400 cycles at an impressive Si loading of 10 mg cm-² could be reached, i.e. with a surface capacity of 10 mAh cm-2 [3]. The thinness of the composite coating on the foam walls favors a better preservation of the electronic wiring upon cycling and fast lithium ion diffusion. A higher coulombic efficiency in half cells with lithium metal as the counter electrode is achieved by using carbon nanofibers (CNF) rather than carbon black (CB). The possibility to reach in practice higher surface could allow a significant increase of both the volumetric and gravimetric energy densities by 23% and 19%, respectively, for the Cu foam-Silicon//LiFePO4 stack compared to the Graphite/LiFePO4 stack of traditional design. Acknowledgements Financial funding from the Agence Nationale de la Recherche (ANR) of France (BASILIC project) and the Natural Science and Engineering Research Council (NSERC) of Canada is acknowledged. The authors thank D. Pilon (Metafoam Inc.) for supplying the Cu foams. References [1] L. Hu, F. La Mantia, H. Wu, X. Xie, J. McDonough, M. Pasta, Y. Cui, Adv. Energy Mater., 1, 1012 (2011). [2] I. Kovalenko, B. Zdyrko, A. Magasinski, B. Hertzberg, Z. Milicev, R. Burtovyy, I. Luzinov and G. Yushin, Science, 334, 75 (2011). [3] D. Mazouzi, , D. Reyter, M. Gauthier, P. Moreau, D. Guyomard, L. Roué, B. Lestriez, Adv. Energy Mater., DOI: 10.1002/aenm.201301718. Figure 1. (a) Surface SEM images of a Cu foam filled with 5 mg of Si/CNF/CMC/Buffer composite electrode (4.6 mg Si per cm2). (b) Cycle life as a function of the active mass loading for Foil-Si/CB/CMC/Buffer and Foam-Si/CNF/CMC/Buffer electrodes (Si//Li half-cell with LP30+2%VC+10%FEC, capacity limitation of 1200mAh per g of Si).

Li4Ti5O12/LiFePO4 cells are cycled under 4 different conditions of discharge profile (galvanostatic or driving-based) and cycling rates (C/8 or 1C) during 4–5 months. All the cells exhibit capacity fade whose extent is not correlated with the aging condition. In order to understand aging phenomena, cells are disassembled at the end of cycle life and the recovered electrodes are analyzed using electrochemistry, electron microscopy, XRD and MAS-NMR. Positive and negative electrodes show no loss in active material and no change in electrochemical activity, active material structure and composite electrode structure. This rules out any irreversible electrode degradation. Lithium stoichiometry estimated by both XRD and electrochemistry is unexpectedly low in the positive electrode when the aging is stopped at full discharge. That indicates a loss of cyclable lithium or electrons leading to cell balancing evolution. That loss may have been caused by parasitic reactions occurring at both electrodes, in accordance with their rich surface chemistry as evidenced by MAS-NMR.

Degradation of the electrochemical performance of LiFePO4 upon air exposure, assigned to a corrosion-type aging mechanism, implies the incorporation of hydroxyl groups and the formation of an amorphous tavorite-like phase at the surface. Using a carbon coating provides an efficient protection from this detrimental process but also modifies the surface in contact with the electrolyte. The formation and evolution of electrode/electrolyte interphases forming on both air-aged and carbon coated LiFePO4 are discussed based on combined quantitative 7Li, 19F MAS NMR, EIS and EELS measurements. Concerning the air-aged LiFePO4, the electrode/electrolyte interactions are dominated by the dissolution of the active material and an exacerbated reaction of incorporated hydroxyl groups with the electrolyte salt, resulting in a LiF rich interphase. This dissolution of the outer part of active material particles is accompanied by the departure of the previously formed interphase and a new interphase is then formed on a newly exposed surface. The resistive LiF rich interphase passivates the active material particles during cycling, forming a resistive film, hindering both Li ion transfer and material corrosion. Cellulose acetate based carbon coating prevents air-aging but yields to an accumulation of organic lithiated species, allowing Li transfer and maintaining good electrochemical performance.

The Mott insulator compound GaV4S8 exhibits resistive switching (RS) properties under electric pulses which could be used in the domain of data storage for future replacement of Flash technology. In this work, we present the characterization and the resistive switching performances of three devices containing GaV4S8 thin films with various electrode sizes and geometries, i.e. planar interdigit electrodes and Metal/Insulator/Metal Au/GaV4S8/Au structures. First, we evidence the good quality of the interfaces between GaV4S8 layers and gold electrodes through transmission electron microscopy observations which allows reliable electrical characterizations. Then, we demonstrate a downscaling effect as the resistive switching amplitude ΔR/R=(Rhigh−Rlow)/Rlow increases from a few percents to more than 600% as the electrode size decreases from 50×50μm2 to 2×2μm2. Finally we show that other performances such as cycling endurance, reaching more than 65,000 RS cycles, data retention time till 10years or writing speed below 100ns confirm the high potential of GaV4S8 as active material in future resistive random access memories or Mott memories.