Improving High Voltage Interfacial and Structural Stability of Layered Lithium-Rich Oxide Cathode by Using a Boracic Electrolyte Additive

In this work, a boracic electrolyte additive trimethyl borate (TMB) was investigated to improve the interfacial and structural stability of layered lithium-rich oxide (LLO) at high operating potential. The LLO in electrolyte with 2% TMB additive shows high capacity retention of 84.5% after 300 cycles at 0.5 C and good rate capability of 120 mAh g(-1) at 4 C rate, comparing to 17.9% after 250 cycles and 65 mAh g(-1) at 4 C rate of baseline electrolyte. The results from DFT calculation, dQ/dV, EIS, chronoamperometry and physical characterizations indicate that TMB has higher oxidation activity than baseline electrolyte. The preferential oxidation of TMB generates an effective protective film on the LLO surface, which greatly restrains the continuous oxidation of baseline electrolyte and enhances the structural stability of electrode, leading to excellent cyclic and rate performances of LLO at high operating potential. (C) 2016 The Electrochemical Society. All rights reserved.