Synergistic electrolyte additives for enhancing the performance of high-voltage lithium-ion cathodes in half-cells and full-cells

Abstract Herein we address the key challenge towards the practical use of high-voltage lithium-ion cathode materials, i.e., the insufficient stability of the electrolyte towards oxidation. The transition metals in such materials, especially nickel, catalyze the decomposition reaction of the electrolyte, ultimately leading to poor cycling stability and rapid fading of the battery. To tackle this challenge, a new combination of electrolyte additives is introduced, targeting stabilized electrode/electrolyte interfaces and interphases for both the anode and cathode. The results show that the synergistic effect of tris(trimethylsilyl) phosphite (TTSPi) and bis(2,2,2-trifluoroethyl) carbonate (TFEC) can significantly improve the performance of cathode half-cells and also of lithium-ion full-cells with a cell voltage higher than 4.5 V. Cells using both TTSPi and TFEC as additives show greatly enhanced cycling stability, increased capacity, and improved coulombic efficiency, which can be even further improved when adding also lithium bis(oxalato)borate.