A multifunctional phosphite-containing electrolyte for 5 V-class LiNi0.5Mn1.5O4 cathodes with superior electrochemical performance

Abstract

We report a highly promising organophosphorus compound with an organic substituent, tris(trimethylsilyl)phosphite (TMSP), to improve the electrochemical performance of 5 V-class LiNi_0.5Mn_1.5O₄ cathode materials. Our investigation reveals that TMSP alleviates the decomposition of LiPF₆ by hydrolysis, effectively eliminates HF promoting Mn/Ni dissolution from the cathode, and forms a protective layer on the cathode surface against severe electrolyte decomposition at high voltages. Remarkable improvements in the cycling stability and rate capability of high voltage cathodes were achieved in the TMSP-containing electrolyte. After 100 cycles at 60 °C, the discharge capacity retention was 73% in the baseline electrolyte, whereas the TMSP-added electrolyte maintained 90% of its initial discharge capacity. In addition, the LiNi_0.5Mn_1.5O₄ cathode with TMSP delivers a superior discharge capacity of 105 mA h g⁻¹ at a high rate of 3 C and an excellent capacity retention of 81% with a high coulombic efficiency of over 99.6% is exhibited for a graphite/LiNi_0.5Mn_1.5O₄ full cell after 100 cycles at 30 °C.