Optimizing interphase structure to enhance electrochemical performance of high voltage LiNi0.5Mn1.5O4 cathode via anhydride additives

Abstract

A series of anhydrides have been used as additives in carbonate-based electrolytes for optimizing the interphase of LiNi0.5Mn1.5O4 (LNMO) cathode material to enhance the electrochemical performance of high-voltage (5 V-class) lithium-ion batteries (LIBs). The cyclic stability and rate performance of high-voltage LNMO/Li cells were remarkably enhanced by introducing the anhydride additives into electrolyte. Specifically, the LNMO cathode in the electrolyte with butyric anhydride (BA) additives exhibits high capacity retention of 84.8% after 300 cycles at 1C, and outstanding rate capability of 112 mA h g−1 at 5C. By characterizations, it is rationally demonstrated that the cathode electrolyte interphase (CEI) can be optimized via using different anhydride additives which strongly depend on the molecular structure of anhydride, caused by the electronic and steric hindrance effects during the oxidation process. As a result, the butyric anhydride (BA) derived CEI film exhibits the most suitable microstructure on the LNMO surface, which not only can inhibit the continuous electrolyte decomposition but also facilitate the lithium-ion diffusion coefficient. Moreover, the anhydride can further consume the trace water of electrolyte to stabilize LiPF6 salt and scavenge the erosive HF. Therefore, such an electrolyte additive presents a potential which practical application in high voltage lithium-ion batteries.