Proton-cooperated copper-ion storage in vanadium hexacyanoferrate cathode enables high-performance aqueous copper metal battery

Vanadium hexacyanoferrate (VHCF) has shown great application potential as a cathode material for multivalent-ion batteries due to its low cost, ease of synthesis, and high capacity. However, its electrochemical performance and mechanism in aqueous copper metal batteries (ACMBs) have not been explored. Herein, a nanosized VHCF was used as the cathode material for ACMBs, and the effects of adding H₂SO₄ to the electrolyte on the battery's electrochemical properties were systematically investigated. The VHCF||CuSO₄ + H₂SO₄||Cu battery exhibited higher energy density, power density, and cycling stability than the VHCF||CuSO₄||Cu battery. Specifically, the discharge capacity could reach 81.6 mAh g⁻¹ with an energy density of 55.6 Wh Kg⁻¹ at 0.2 A g⁻¹; the specific capacity remained at 48.7 mAh g⁻¹ after 2000 cycles with a capacity retention ratio of 63.8 %; the power density could reach 4213 W Kg⁻¹ at a current density of 5 A g⁻¹. This enhancement can be attributed to enhanced proton-cooperated copper ion storage and reaction kinetics in the VHCF cathode, along with improved reversibility of the copper anode. This work can offer new ideas for the design of electrode materials and electrolytes for ACMBs.