Improved cycling stability of LiCoO2 at 4.5 V via surface modification of cathode plates with conductive LLTO

Abstract

The stability issue of LiCoO 2 cycled at high voltages is one of the burning questions for the development of lithium ion batteries with high energy density and long cycling life. Although it is effective to improve the cycling performance of LiCoO 2 via coating individual LiCoO 2 particles with another metal oxides or fluorides, the rate capacity is generally compromised because the typical coating materials are poor conductors. Herein, amorphous Li 0.33 La 0.56 TiO 3 , one of the most successful solid electrolytes, was directly deposited on the surface of made-up LiCoO 2 cathode plates through magnetron sputtering. Not only the inherent conductive network in the made-up LiCoO 2 cathode plates was retained, but also the Li + transport in bulk and across the cathode-electrolyte interface was enhanced. In addition, the surface chemical analysis of the cycled LiCoO 2 cathode plates suggests that most of the stability issues can be addressed via the deposition of amorphous Li 0.33 La 0.56 TiO 3 . With an optimized deposition time, the LiCoO 2 cathode plates modified by Li 0.33 La 0.56 TiO 3 performed a steady reversible capacity of 150 mAh/g at 0.2 C with the cut-off voltage from 2.75 to 4.5 V vs. Li + /Li, and an 84.6% capacity gain at 5 C comparing with the pristine one.