Surface Reconstruction and Lattice Oxygen Modulation of 4.6 V LiCoO2 Cathode for Enhanced Fast-Charging Durability

Abstract

Increasing the charging cutoff voltage is the most direct way to enhance the energy density of LiCoO₂, but it brings severe adverse effects. Here we propose a synergistic strategy of surface reconstruction and lattice oxygen modulation by Ba-doping to improve structural stability and electrochemical performance. Ba-doped LiCoO₂ presents fast-charging durability at 4.6 V, and enhanced capacity retention of 69.4% after 200 cycles at 1 C compared to 16.8% for pristine LiCoO₂. Introducing both the large ionic radius of Ba and lattice oxygen vacancies facilitates lithium-ion transport. The surface construction tailors the residual alkali layer and rocksalt phase. Two-phase hybrids with heterogeneous Li⁺ (de)lithiation were observed in pristine LiCoO₂ during cycling, while a spinel phase with 3D lithium-ion diffusion channels was observed in Ba-doped LiCoO₂. Our strategy suppresses lattice strain, structural degradation, and microcracks, and alleviates gas release during fast charging at high voltage, revealing the potential of lattice engineering to meet the demands of high-voltage batteries.