Surface Modifications on LiCoO2-Based Cathodes for High-Density Lithium-Ion Batteries with Long Cycle Life

Abstract

Commercial rechargeable lithium-ion batteries (LIBs) use LiCoO2(LCO) as the cathode, which shows relatively low energy capacity (~140 mAh/g) and suffers poor cycle life performance. To develop next-generation LIBs with high voltage, high capacity and long cycle life, surface modifications on cathodes have been applied. We start with thin layers of Li2SrSiO4(LSSO) synthesized from sol-gel method to coat on the LCO surfaces and to test the optimal conditions, namely thickness and annealing temperature, for LIB performances in both half-cell and full cell configurations. LSSO is predicted by theoretical calculation1as the best surface coating but our results show that LSSO alone cannot lead to improved performance at 4.5 V cut-off voltage but a combination of LSSO and Al2O3could yield the best protection and performance. Following a series of electrochemical tests, electron microscopy and synchrotron X-ray characterizations, we provide some insights about mechanism in our surface modification. [1] M. Aykol et al., Nature Communications, 7, 2016, 13779