A high-efficiency and long-cycling aqueous indium metal battery enabled by synergistic In ³⁺ /K ⁺ interactions

Aqueous trivalent metal batteries are promising options for energy storage, owing to their ability to transfer three electrons during redox reactions. However, advances in this field have been limited by challenges such as incompatible M³⁺/M electrode potentials and salt hydrolysis. Herein, we identify the trivalent indium metal as a viable candidate and demonstrate a high-performance indium-Prussian blue hybrid battery using a K⁺/In³⁺ mixture electrolyte. Interestingly, there exists a synergistic interaction between K⁺ and In³⁺ ions, which enhances the coulombic efficiency and prolongs the cycling life. Specifically, the addition of K⁺ elevates the In³⁺/In plating efficiency from 99.3% to 99.6%, due to the decreased electrolyte acidity and enlarged indium particle size. Simultaneously, the presence of In³⁺ creates an inherently acidic environment (pH ∼3.1), which effectively stabilizes K⁺ insertion into the Prussian blue framework. Consequently, this hybrid battery delivered a high capacity of 130 mA h g^-1, an exceptional rate of 96 A g^-1 (∼740 C), and an extraordinary cycling life of 48 000 cycles. This work offers an innovative approach to develop high-performance hybrid metal batteries.