Progress on High-Entropy Oxide Anode Materials for Advanced Lithium-Ion Batteries

The rapid development of electric vehicles and large-scale energy storage is driving the requirements for lithium-ion batteries (LIBs) with high energy density, long cycle life, and enhanced safety. However, the commercial graphite anode (372 mAh g^-1) struggles to meet these demands. Transition metal oxides are considered as promising anode alternatives due to higher specific capacity and low cost, while their wide application is limited by volume expansion and low conductivity, resulting in rapid capacity fading and poor rate performance. In 2018, the first application of high-entropy oxides (HEOs) as LIB anodes was reported, which attracted the attention of researchers. HEO anodes exhibit outstanding structural stability and electrochemical reversibility owing to their high-entropy effect, lattice distortion, cocktail effect, and sluggish diffusion. This review summarizes recent works on HEO anodes for LIBs, focusing on their structural types, synthesis methods, and advanced characterization techniques. Moreover, lithium storage mechanisms are discussed. Finally, this article points the challenges of HEO anodes, including low reversible capacity, low initial coulombic efficiency, and unclear reaction mechanisms. In the future, the researchers should focus on computational modeling, machine learning, and advanced in situ characterization to explore the next-generation HEO anodes for LIBs.