Suppressing Intergranular Cracking with Near-Surface Layer Regulation for Electrochemical-Thermal Stabilization of LiCoO2

To further meet the application needs of lithium-ion batteries, developing cathodes with higher voltage and higher operating temperatures has become a primary goal. However, LiCoO2 cathodes encounter structural issues, particle fracture, and side reactions during high-voltage and high-temperature cycling. Thus, this work designs a novel interface engineering approach involving near-surface Li layer regulation and enhances the stability of the R3̄m layered structure, suppressing intergranular cracking. An undistorted surface with reduced phase transitions was revealed by the HAADF-STEM. The interface regulation by post-cycle simulations and XRD stabilizes interplanar spacing. The strong B-O bonds lower the O 2p energies, preventing oxygen loss and side reactions confirmed by XPS and band structure. Therefore, even under 50 °C, the half-cell maintains a capacity retention rate of 79% after 200 cycles at 5C at 4.5 V.