Pre-Deoxidation of Layered Ni-Rich Cathodes to Construct a Stable Interface with Electrolyte for Long Cycling Life

Abstract

Ni-rich layered oxides as the cathode materials of high-energy-density lithium-ion batteries (LIBs) suffer from capacity decay and structural instability owing to oxygen loss during cycling. It is a huge challenge to prevent the oxygen loss of Ni-rich cathode materials during long cycling. Here, a pre-deoxidation of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) single crystal materials is achieved by heat treatment at elevated temperatures in argon condition to form a stable surface with rock salt structure. The stable surface structure with oxygen vacancy defects successfully suppresses the harmful phase transitions of NCM811 and effectively improves the stability of the NCM811/electrolyte interface during cycling at a high cut-off voltage. In addition, the intragranular structural evolution and cation mixing degree is inhibited to effectively suppress the intergranular cracking and particle pulverization of cathode during long cycling. The pre-deoxidation of NCM811 exhibits 70.6% capacity retention after 1000 cycles at the current density of 0.5 C between 2.8 and 4.3 V, which is much larger than that of pristine NCM811 capacity retention of 27.3%. The strategy of pre-deoxidation of Ni-rich layered structure cathode to regulate the defect chemistry and surface structure provides a facile and effective way to achieve long cycling life high-energy density LIBs.