Sb as High-Capacity Anion Host for H⁺/PO₄^3- Reverse Dual-Ion Battery

Aqueous proton batteries (APBs) have attracted increasing attention due to their high-power capability and low-temperature tolerance. Electrode materials remain a bottleneck and have restricted the further development of APBs. Here, we report H⁺/PO₄^3- reverse dual-ion batteries (RDIBs) with a Sb anode functioning as PO₄^3- host and a Turnbull blue analogue (TBA) or tetrachloro-p-benzoquinone (TCBQ) cathode as H⁺ host. The Sb anode reversibly accommodates PO₄^3- via the equation Sb + PO₄^3- - 3e^- ↔ SbPO₄ at −0.2-0 V vs Ag/AgCl and delivers a specific capacity of 686 mAh/g. Pairing with a TBA cathode, the resultant TBA|Sb RDIB exhibits acceptable cycling stability and rate capability even under a positive/negative (P/N) mass ratio of 7. Another TCBQ|Sb RDIB features a flat voltage platform and operation competence at −30 °C. Our work enriches anion hosts for high-capacity DIBs and offers a configuration solution to the practicality of H⁺-deficient electrodes in proton-based energy storage devices.