Recent advances and design strategies of cathode materials for aqueous aluminum-ion batteries

The growing global energy demand stimulates the urgent need for safe, sustainable, and cost-effective energy storage technologies. Aqueous aluminum-ion batteries (AAIBs) have emerged as promising candidates owing to their abundant resources, intrinsic safety, environmental compatibility, and high capacity. AAIB research has seen rapid development, focusing on high-capacity cathodes compatible with Al anodes. The high charge density of trivalent Al³⁺ induces strong electrostatic interactions with the cathode, impeding ion transport, causing structural distortion, and accelerating capacity decay, while side reactions in aqueous electrolytes further limit reversibility and stability. Addressing these challenges requires a mechanistic understanding of how the cathode composition and structure regulate Al³⁺-cathode interactions and redox behavior. This review analyzes the fundamental Al³⁺ storage mechanisms in AAIBs, emphasizing the influence of cathode chemistry, structural characteristics, and electrolyte environment on ion transport, Al³⁺-cathode interactions and electrochemical performance. Furthermore, representative cathodes, including manganese-based oxides, vanadium-based compounds, Prussian blue analogues and organic cathode materials, are systematically summarized in terms of structure, performance, and optimization strategies. Finally, the review outlines current challenges and prospective research directions for advancing next-generation high-performance AAIB cathodes. This review is expected to provide valuable insights for guiding cathode material design and inspire future strategies to enhance the capacity, stability, and rate performance of AAIBs.