Research On The Compatibility Between Sulfonium-Based Ionic Liquids Electrolytes And Ti-Based Anode Material (Li₄Ti₅O₁₂ Nanosheets

The researches of compatibility among components of lithium ion battery haveattracted great attention in recent years. Ionic liquids have many unique properties,such as nonvolatility, nonflammability, good thermal and electrochemical stability andhigh ionic conductivity. Ionic liquids are considered as the new promising electrolytesfor lithium ion battery to improve the problem of safty. It is important to investigatethe compatibility of ionic liquids and electrode materials in order to apply them inlithium ion batteries.Recently, few researches are involved with the compatibility between theelectrode materials and ionic liquid electrolytes, especially for sulfonium-based ionicliquids and nano Li₄Ti₅O₁₂ anode material.In this article, Li₄Ti₅O₁₂ nanosheets with a size range of 200⁴00nm weresynthesized by hydrothermal method from the amorphous hydrous titanium oxideprecursors. The as-prepared product is characterized by X-ray powder diffraction(XRD), scanning electron microscopy (SEM) and transmission electron microscopy(TEM). Meanwhile, electrochemical behaviors of Li₄Ti₅O₁₂ electrode in conventionalorganic electrolyte were investigated by using cyclic voltammetry, galvanostaticcharge and discharge and AC impedance techniques. The first discharge capacity at1C was 211 mAh/g, and after 100 cycles can also attained 162 mAh/g, close to thetheory capacity of Li₄Ti₅O₁₂ material.The electrochemical behaviors of Li₄Ti₅O₁₂ electrode in S₁₁₄TFSI and S₂₂₁TFSI electrolyte were investigated by using cyclic voltammetry and galvanostaticcharge-discharge techniques. The experiment results indicated that Li₄Ti₅O₁₂ electrodehas better compatibility with S₂₂₁TFSI electrolyte, and the first discharge capacity is195 mAh/g at 1C.The compatibilities of various cathode materials (LiMn₂O₄, LiFePO₄, LiCoO₂)with Li₄Ti₅O12/S₂₂₁TFSI system and the influence of lithium concentration werestudied. At 0.8M lithium concentration and the rate of 1C, the first dischargecapacities were 127 mAh/g, 134 mAh/g, 139 mAh/g, and after 100 cycles thedischarge capacities were 83 mAh/g, 108 mAh/g, 136 mAh/g separately.When the selected Li₄Ti₅O₁₂/0.8M LiTFSI S₂₂₁TFSI/LiCoO₂ system was beingcycled at 1C, 2C, 4C, 8C separately, the first discharge capacities were 139 mAh/g,115 mAh/g, 84 mAh/g, 55 mAh/g,and after 100 cycles the capacities were 136mAh/g, 100 mAh/g, 76 mAh/g, 46 mAh/g separately.