Carbon-SupportedIn₂O₃ Cathodewith a Solution-to-Solid Conversion Chemistry Enables Fast-Chargingand Durable Aluminum Battery

Conversion-type materials are promising cathodes with high theoretical capacities for rechargeable aluminum batteries (RABs). However, the cathodes are mainly based on a solid-to-solid conversion chemistry with sluggish reaction kinetics, resulting in a large volume change and severe electrode pulverization during cycling. Herein, a solution-to-solid conversion chemistry which resolves the cycling problems is found in carbon-supported In₂O₃ (In₂O₃@C) cathode, which exhibits fast-charging rate capability and excellent cycling stability in RABs. The In₂O₃@C architecture is featured with rod-shaped hollow carbon decorated with ultrafine In₂O₃ nanoparticles. The solid In₂O₃ converse into soluble InCl (In⁺) in the first discharge. In the following cycles, a reversible solution-to-solid conversion reaction occurs between soluble InCl (In⁺) and sparingly soluble InCl₃. The highly conductive carbon skeleton provides sufficient reaction sites to guarantee the reversible precipitation of solid InCl₃ as a charge product. Meanwhile, due to fast oxidation kinetics and the self-healing property of the solution phase, the Al|In₂O₃@C cell exhibits a high capacity of 335 mA h g^–1 with marginal cell overpotential of just 50 mV at 0.2 A g^–1, superior charging rate capability, and outstanding cycling stability at 5 A g^–1. This work provides insights into the development of cathode materials with a solution-to-solid reaction mechanism for high-performance RABs.