High Performance 4.6 V LiCoO₂ Cathode Materials Enabled by Surface Lattice Modulation.

Abstract

Charging the cathode of LiCoO₂ (LCO) to higher voltages, typically 4.6 V, is able to increase reversible capacity, but meanwhile raises serious stability issues. Here, through a decomposition-induced reconstruction (DIR) process, we demonstrate the possibility of modulating the surface lattice of LCO with high precision in depth control, thereby enabling the 4.6 V LCO cathode to have both high capacity and structural integrity. Following the precise construction of a conformal Y(OH)CO₃ nanoshell, a sintering process induces the hydrocarbonate decomposition, which releases CO₂ to transform the layered structure of the LCO crust into rock-salt-like lattices, forming a renovated surface with high electrochemical and mechanical stability. The prepared LCO cathode delivers a high reversible capacity of 215.8 mAh g^-1 at 0.1 C with an extraordinary capacity retention of 93.0% after 100 cycles at 4.6 V. The much-improved stability is meanwhile manifested by cyclability test at 1 C (85.5% vs 13.6% of pristine LCO after 500 cycles), as well as tests at harsh conditions. Our results highlight the essential role played by the surface chemistry in addressing the stability issue of high voltage LCO cathode, and provide useful guidelines for the development of lithium-ion batteries with higher energy density.