Entropy-Driven Modulation Enables Atomic-Level Interactions for High-Rate Capacity Cathode Materials in Rechargeable Aqueous Aluminum-Ion Batteries
Aqueous aluminum-ion batteries (AAIBs) are promising for large-scale energy storage due to safety, sustainability, and theoretical high capacity. However, sluggish electron/ion transport in conventional cathodes limits rate capability. Here, we first propose high-entropy engineering of metal oxides (HEOs) as cathodes in AAIBs, leveraging the 'cocktail effect' and abundant electron transport pathways to enhance rate-capacity. Atomic-level interactions between different metal atoms broaden the d-band with reduced electronic level degeneracy, facilitating rapid electron transport, achieving one of the best rate capabilities (119.4 mAh g−1 at 10.0 A g−1) among metal-oxide cathodes. The disordered layered oxides formed with a high-entropy framework alleviate electrostatic repulsion between aluminum ions and the fixed lattice, mitigating structural degradation and imparting excellent cycling stability (over 95.1 mAh g−1 after 500 cycles at 2.0 A g−1). The optimized HEO-Cr cathode (Fe0.6Co0.6Ni0.6Mn0.6Cr0.6O4) exhibits outstanding rate performance and cycling stability. DFT simulations and electrochemical tests reveal that multi-transition metal incorporation, bandgap narrowing, and unique lattice structure drastically enhance electron transport efficiency. The layered phase formed after cycling, based on a high-entropy framework, overcomes challenges from high charge density aluminum ions, significantly enhancing cycling stability. This work paves the way for high-performance AAIBs and other aqueous multivalent metal ion batteries by rationally designing high-entropy engineering.