Modulating Solvent Layer Structure of Li+ to Achieve a Stable High-Voltage Electrolyte for Lithium-Ion Batteries

With the increasing demand for high energy density batteries with high voltage and stable electrode/electrolyte interfaces, the use of low cost and high stability electrolyte additives to modify electrolytes is becoming more and more important. In this study, tetramethylene sulfone (TS) additives based on conventional carbonate electrolytes are investigated to identify the solvated layer structure, the stability of the electrolyte, and the improved effect on batteries. Based on the dynamic simulation and physical-chemical property analysis, TS can participate in the solvation structure of Li+ which contributed to the improved high-voltage stability of the electrolyte and the formation of a stable interlayer at the electrode. The uniform layer formed by the TS additive electrolyte inhibits the excessive decomposition of the electrolyte, and the reduced active Li loss of the LiCoO2 cathode (LCO) electrode can reduce the interface impedance and increase the ion diffusion rate, thus making the structure of the electrode material more stable. Moreover, the LCO structures after cycling detected by X-ray diffraction verify that the protection effect of the TS additive electrolyte is more obvious at high voltage and high current density. As a result, the TS additive for carbonate-based electrolytes can remain stable at a high voltage and form a stable interlayer due to the modification of the solvated layer structure, which help improve the cycle life and specific capacity of the battery. This study provided a construction idea for high-voltage electrolytes and high energy density batteries.