Concentrated Chloride Electrolytes Enable High-Efficiency, Long-Cycling, and Dendrite-Free Aqueous Trivalent Antimony Batteries.

Aqueous trivalent metal batteries are promising energy storage systems, which can leverage unique three-electron redox reactions to deliver high capacity and high energy. Among them, antimony (Sb) stands out with a high capacity (660 mAh g-1), abundant availability, and low cost. However, the severe Sb3+ hydrolysis reaction drastically hinders the development of aqueous antimony batteries. Herein, we address this issue by employing a concentrated lithium chloride electrolyte, which stabilizes reactive Sb3+ ions via forming robust antimony-chloride complexes. This approach effectively mitigates hydrolysis and achieves highly reversible Sb plating behavior, leading to high efficiency (99.7-99.8%), long lifespan (7,300 hours, 10 months), and uniform spherical deposition morphology. When paired with a manganese dioxide (MnO2) cathode, the Sb‖MnO2 battery demonstrates a high capacity of 309 mAh g-1 and exceptional cycling stability of 50,000 cycles (~70% retention). Additionally, Sb shows promise as a high-capacity cathode, which can integrate with low-potential zinc into novel dual-metal plating batteries with long cycling life (4,000 hours). This work not only deepens our fundamental understanding of trivalent Sb3+ redox chemistry but also opens new opportunities to stabilize hydrolysable and high-charge-density cations for multivalent battery applications.