Metastable state regulation and lattice modulation in layered cathodes for aluminum batteries

Aluminum batteries (ABs) are considered promising candidates for large-scale energy storage owing to their high volumetric capacity, abundant resources, and intrinsic safety. However, layered cathode materials generally suffer from diffusion hysteresis and structural instability induced by the strong electrostatic interaction of Al3+, which severely hinders the development of high-energy-density systems. This review breaks through conventional single-mode optimization strategies and innovatively establishes a synergistic design framework integrating lattice engineering with metastability regulation. Through cation/anion doping, interlayer spacing modulation, defect engineering, and strain regulation, the local electronic structure and ion migration pathways are optimized to reduce multivalent-ion diffusion barriers. Meanwhile, metastability regulation is introduced to activate unconventional energy-storage mechanisms, including anionic redox, transient phase evolution, and dynamically disordered structures, thereby unlocking the latent capacity of materials. Particular emphasis is placed on the synergistic effects of lattice reconstruction and metastable stabilization in enhancing energy density, suppressing structural degradation, and improving kinetic performance. In addition, key challenges related to electrolyte compatibility, interfacial stability, and scalable construction of metastable structures are systematically discussed. Finally, future directions involving high-entropy layered systems, advanced in situ characterization, and data-driven materials design are proposed.