Understanding the lithiation mechanism of Li2O-doped spinel high-entropy oxides as anode materials for Li-ion batteries

Abstract

High-entropy oxides (HEOs) have started to attract widespread interest as anode materials for lithium-ion batteries (LIBs), because of their high theoretical discharge capacities, fast ionic conductivity, and stable structure caused by the unique entropy stabilization effect and the “cocktail” effect. However, the lithiation mechanism of HEO anode is still conversional, which prevents its further development. Herein, we propose an Li₂O-doping strategy for improving the lithium storage ability of HEO anodes. Li₂O is successfully introduced into the spinel high-entropy oxide to obtain a (FeMgNiCrMnLi)₃O₄ anode (Li-SHEO) via a solution combustion synthesis and ball milling method. Experimental results show Li doping would induce the growth of oxygen vacancies and regulate the conversion reactions during the discharge process, leading to improved electrochemical performance. As a result, the lithiation process of an Li-SHEO anode includes an enhanced Li⁺ ion intercalation process and a typical conversion reaction. Compared with the (FeMgNiCrMnLi)₃O₄ (SHEO) anode, the Li-SHEO anode shows a high reversible discharge capacity of 850.7 mA h g⁻¹ after 200 cycles under a large current density of 2.0 A g⁻¹.