Selective construction of amorphous/crystalline heterostructure high entropy oxide for Li-ion batteries

Abstract

High entropy oxides (HEO) are widely used as anode for lithium-ion batteries due to their exceptional chemical stability and mechanical strength. However, HEO encounters challenges such as low initial coulomb efficiency (ICE) and poor capacity. To address these issues, a simple mechanochemical method is employed to selectively amorphized and densely embed LiF within the HEO matrix. Taking advantage of the differing chemical properties of LiF and HEO, the transformation of LiF’s crystal structure not only overcomes its poor ionic conductivity but also successfully constructs an amorphous LiF/crystalline HEO heterostructure, which also improves the transport capacity of lithium ions. Additionally, the presence of abundant defects (e.g., oxygen vacancies, dislocations, and stacking faults) boosts the material's lithium transport and storage capacity. Furthermore, LiF facilitates the formation of a stable solid electrolyte interface (SEI) film on the HEO surface, preventing the corrosion of active materials and minimizing side reactions, effectively improving the ICE. The as-prepared LiF/HEO-48 demonstrates a superior initial capacity of 1632.9/1158.5 mAh g−1, along with an ICE of 70.9%. It maintains a high reversible capacity of 552.2 mAh g−1 after 1000 cycles at 0.5 A g−1, and even after 400 cycles at 2 A g−1, it retains 99.4% of its capacity. This study may open up new ways to selectively construct amorphous/heterostructures to improve the ICE and capacity of lithium-ion anodes.