Vanadium hexacyanoferrate as high-performance proton cathode for aqueous hydrogen gas-proton battery

Hydrogen gas-proton batteries (HPBs), utilizing protons as the charge carrier driven by the hydrogen gas anode, demonstrate exceptional rate capability and superior cycling stability in full-cell configurations, and are considered as ideal aqueous proton batteries (APBs) for next-generation energy storage. However, the HPBs still exhibit deficiencies in discharge voltage and specific capacity. Herein, a promising proton cathode, vanadium hexacyanoferrate (VHCF), is developed as a new choice for HPB. Benefiting from the open-framework structure and two redox-active sites (vanadium and iron) of VHCF cathode, the HPB delivers a high specific capacity of 117.8 mAh·g⁻¹ and a discharge voltage of 1.06 V. At room temperature, superior rate capability (48% of the initial capacity at 3000 C) and stable cycling for 600,000 cycles (with 60% capacity retention) are demonstrated, which is the highest value reported for APBs to date. The excellent rate and cycling stability can be maintained at high mass loadings of 25 mg·cm⁻² and low-temperature surroundings (−40 °C). This work is anticipated to motivate the exploration of additional APBs and accelerate advancements in energy storage technology.