Glycerol Tris(2‐cyanoethyl) Ether as an Electrolyte Additive to Enhance the Cycling Stability of Lithium Cobalt Oxide Cathode at 4.5 V

Abstract

High‐voltage lithium cobalt oxide batteries are considered the ideal power source for portable devices, owing to their high‐energy density and accessible specific capacity. However, it is still challenging to achieve long‐term cycling stability when charging to the high cut‐off voltages (≥4.5 V vs. Li/Li+), owing to the unavoidable parasitic reactions at the cathode/electrolyte interface. Herein, we report an organic nitrile‐based molecule, glycerol tris(2‐cyanoethyl) ether (GTCE), as a novel electrolyte additive to improve the cycling stability of LiCoO2 (LCO) batteries at 2.75–4.5 V. Impressively, the LCO||Li metal half‐cell using the GTCE‐containing electrolyte (2 wt % GTCE in the base electrolyte, 1.0 M LiPF6 in EC/DEC/EMC=1/1/1, v/v) exhibits an outstanding capacity retention of 79.3 % over 150 cycles, superior to the battery with base electrolyte (only 27.4 %) under the same test conditions. It represents a feasible and valuable method to stabilize the cathode/electrolyte interface of high‐voltage lithium‐ion batteries.

Structure Property and Reaction Mechanism of Boron-Based High-Voltage Electrolyte Additives via First-Principles Calculations

“…It consists of a semicircle in the high-to-medium frequency and a slope line at low frequencies . The high-frequency semicircle part ( R ct ) corresponds to the interfacial charge-transfer process, and the low-frequency linear part ( R w ) corresponds to the Li + diffusion process. The R ct value of the LiCoO 2 /Li cells with 1 wt % TMB electrolyte or 1 wt % TCEB was lower than that of the base electrolyte after three cycles. It showed that the addition of TMB or TCEB effectively inhibits the deposition of Li + insulators produced by the decomposition of the carbonate electrolyte .…”