Mitigating evolution of lattice oxygen and stabilizing structure of lithium-rich oxides by fabricating surface oxygen defects

Lithium-rich layered cathode material Li_1·2Ni_0·13Co_0·13Mn_0·54O₂ has attracted extensive attention owing to high specific capacity and energy density from its distinctive anionic redox chemistry. However, the material suffers from low Coulombic efficiency, serious capacity attenuation, severe voltage decay which can be ascribed to the irreversible oxygen loss and phase transformation. Herein, oxygen defects are induced through the pre-extraction of lithium and oxygen from Li₂MnO₃ component on the surface of the material accompanying with the generation of spinel structure via a facile method of hydrothermal reaction assisted with calcination clarified by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The material exhibits excellent electrochemical properties including enhanced initial Coulombic efficiency over 87% and prominent capacity retention of 89.7% after 100 cycles superior to those for the pristine, which are attributed to the fact that oxygen defects inhibit evolution of oxygen, and alleviate the lattice microstrain along consecutive delithiation/lithiation process to improve mechanical property of material. Besides, the Galvanostatic Intermittent Titration Technique (GITT) manifests that the material possesses superior dynamic condition. These results indicate that oxygen defects are beneficial to stabilize the lattice oxygen on the surface of the lithium-rich layered oxides for a high-performance cathode material for lithium-ion batteries.