Tuning Co/O Redox Chemistry via Fermi Level Regulation for Stable High-Voltage LiCoO2

LiCoO2 (LCO) is ideal for 3C electronics due to its high tap density. However, the excessive O -> Co charge transfer at high delithiation leads to irreversible Co reduction, O release, and structural degradation, deteriorating the high-voltage performance of LCO. Herein, we propose to regulate the intrinsic Fermi level via uneven trace Zr/Mg doping. First, the increase of electron density in the Fermi level mitigates both the O oxidation/coupled Co reduction through alleviating the O -> Co charge transfer, restraining the formations of Co2+ and O-2. This elevates Co redox activity and reduces O redox activity. In addition, the structural evolution of the cathode at delithiation is simplified. The modulated LCO delivers a high discharge capacity and a high cycling stability with 4.5 and 4.6 V ceilings. This study sheds new light on the modulation of Co/O redox chemistry and the reliable large-scale production of high-voltage LiCoO2.

Automated summary

By modulating the intrinsic Fermi level of LiCoO2 through uneven trace Zr/Mg doping, the high-voltage performance and cycling stability of LiCoO2 have been improved, and the structural evolution of the cathode during delithiation has been simplified. This study sheds new light on the modulation of Co/O redox chemistry and the reliable large-scale production of high-voltage LiCoO2.