The role of oxygen defects in high entropy perovskite for lithium ion batteries

Abstract

High entropy oxides have shown unprecedented vigor in electrochemical lithium storage owing to their remarkable comprehensive properties, especially phase and structure stability. However, the intrinsic low electrical conductivity of oxide materials can lead to sluggish reaction kinetics, a challenge that must be addressed for practical applications. In this paper, a perovskite La(FeCoNiCrMn)O_3-x high entropy oxide (PHEO-V_o) is designed by introducing defect engineering. Experiments and simulations together reveal the pivotal role of oxygen defects, which enhance Li⁺ adsorption, diffusion and insertion/extraction achievability in PHEO by creating unsaturated chemical bonds, local built-in electric fields and additional Li⁺ transport channels. These advantages endow the PHEO-V_o anode with low self-discharge rate and favorable rate performance, rendering the assembled PHEO-V_o//LiFePO₄ full cell with a high specific capacity of 93 mAh g^-1 (72 % capacity retention) after 200 cycles at 1 C. Analysis of the lithium storage mechanism indicates that the unique lattice stability of PHEO-V_o can significantly inhibit structure degradation and facilitate reversible redox reactions. It is believed that leveraging the fundamental benefits of high entropy perovskite and the optimized reaction kinetics through oxygen vacancies can provide valuable guidance for designing conversion-type electrodes with high energy storage potential.