Chemical competing diffusion for ultra-high voltage LiCoO₂

Elevating the operation voltage (≥4.6 V) is essential to realize higher energy density LiCoO₂ (LCO) based lithium-ion batteries (LIBs). However, higher cut-off voltage is inevitably accompanied by more severe material degradation from the surface to the bulk. Herein, a complexing doping strategy involving in trace multi-element (Ti, Mo, W and Mg) in LCO was proposed. Particularly, due to the limited vacancies produced by the LCO precursor during lithiation, a special competitive doping phenomenon of above elements were happened. The Mg content decreased sharply with the doping depth, while other elements are uniformly distributed throughout the particle. Therefore, a high-entropy zone was established in LCO surface, which could serve as “interface rivet” to elevate the surface stability. Furthermore, the other doping elements with high bonding energy to oxygen could act as “oxygen anchor” to enhance the bulk integrity. As a result, this robust LCO structure greatly enhanced the Li-ion diffusion dynamics, enabling the modified sample exhibited remarkable rate performance. Half-cells employing the modified LCO exhibited 80 % capacity retention after 300 cycles, and the capacity retention of full cell is 90 % after 400 cycles. This work provided a promising way for commercializing LCO material at high voltage and fast charging for LIBs.