Temperature-Driven Anisotropic Mg2+ Doping for a Pillared LiCoO2 Interlayer Surface in High-Voltage Applications

High-voltagelithium cobalt oxide (LiCoO2) has the highestvolumetric energy density among commercial cathode materials in lithium-ionbatteries due to its high working voltage and compacted density. However,under high voltage (4.6 V), the capacity of LiCoO2 fadesrapidly due to parasitic reactions of high-valent cobalt with theelectrolyte and the loss of lattice oxygen at the interface. In thisstudy, we report a temperature-driven anisotropic doping phenomenonof Mg2+ that results in surface-populated Mg2+ doping to the side of the (003) plane of LiCoO2. Mg2+ dopants enter the Li+ sites, lower the valencestate of Co ions with less hybridization between the O 2p and Co 3dorbitals, promote the formation of surface Li+/Co2+ anti-sites, and suppress lattice oxygen loss on the surface. Asa result, the modified LiCoO2 demonstrates excellent cyclingperformance under 4.6 V, reaching an energy density of 911.2 Wh/kgat 0.1C and retaining 92.7% (184.3 mAh g(-1)) of itscapacity after 100 cycles at 1C. Our results highlight a promisingavenue for enhancing the electrochemical performance of LiCoO2 by anisotropic surface doping with Mg2+.

Automated summary

This study reports a temperature-driven anisotropic doping phenomenon of Mg2+ that results in surface-populated Mg2+ doping to the side of the (003) plane of LiCoO2. The Mg2+ dopants lower the valence state of Co ions, promote the formation of surface Li+/Co2+ anti-sites, and suppress lattice oxygen loss, leading to excellent cycling performance of modified LiCoO2 under high voltage. The modified LiCoO2 achieves a high energy density and retains a high capacity after multiple cycles, highlighting the promising potential of anisotropic surface doping with Mg2+.