Previous work demonstrated that TiSnSb is a promising negative electrode material with high electrochemical performance due to the benefit of conversion type reaction vs Li. At low potentials, the volumetric change upon cycling entails electrolyte degradation which remains the main factor limiting the cycling life of TiSnSb based electrodes. To further improve the understanding of the formation of a solid electrolyte interphase (SEI) in the presence of alkyl carbonate based electrolytes and of its evolution upon cycling, powerful surface characterization techniques are combined for studying the electrode/electrolyte interface of TiSnSb composite electrodes. Electrochemical impedance spectroscopy is used for monitoring in situ the resistivity of the SEI, while XPS and solid state NMR spectroscopy can provide useful information on the SEI chemical composition and its evolution during cycling.
Recently, dinitriles (NC(CH ) CN) and especially adiponitrile (ADN, n=4) have attracted attention as safe electrolyte solvents owing to their chemical stability, high boiling points, high flash points, and low vapor pressure. The good solvation properties of ADN toward lithium salts and its high electrochemical stability (≈6 V vs. Li/Li ) make it suitable for safer Li-ions cells without performance loss. In this study, ADN is used as a single electrolyte solvent with lithium bis(trimethylsulfonyl)imide (LiTFSI). This electrolyte allows the use of aluminium collectors as almost no corrosion occurs at voltages up to 4.2 V. The physicochemical properties of the ADN-LiTFSI electrolyte, such as salt dissolution, conductivity, and viscosity, were determined. The cycling performances of batteries using Li Ti O (LTO) as the anode and LiNi Co Mn O (NMC) as the cathode were determined. The results indicate that LTO/NMC batteries exhibit excellent rate capabilities with a columbic efficiency close to 100 %. As an example, cells were able to reach a capacity of 165 mAh g at 0.1 C and a capacity retention of more than 98 % after 200 cycles at 0.5 C. In addition, electrodes analyses by SEM, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy after cycling confirming minimal surface changes of the electrodes in the studied battery system.
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