All-Cation Engineering in One Step: Bulk and Surface Stability of LiCoO2 at 4.6 V

Abstract

The relentless demand for higher capacity forces high-voltage operation, under which deep delithiation of layered LiCoO2 (LCO) cathodes triggers rapid capacity decay via concurrent bulk collapse, surface oxygen evolution, and incessant interfacial side reactions. Here, an all-cation engineering strategy in one-step is proposed to integrate uniform bulk doping with surface gradient doping in high entropy configuration, thereby simultaneously achieving structure stability of LCO from bulk to surface at high voltage of 4.6 V. The incorporation of Cu, Mn, Fe, and Ni in bulk mitigates lattice strain and expands the interlayer spacing for rapid Li + transport. Concurrently, a robust high-entropy surface layer with the additional gradient addition of Mg and Al suppresses lattice oxygen release and detrimental interfacial reactions. Empowered by this synergistic dual-region stabilization, the engineered LCO delivers an exceptional reversible capacity of 201.2 mAh g -1 and retains 88.6% capacity after 400 cycles at 1 C. This approach provides a highly viable pathway for designing robust, high-energy-density layered cathodes.