Vanadium hexacyanoferrate as high-capacity cathode for fast proton storage

Proton electrochemistry is promising for developing future energy storage devices with both high capacity and good rate capability. However, the development of this technology is now hindered by the limited choice of accessible electrodes, especially for cathodes. Herein, we report vanadium hexacyanoferrate (VHCF) as a candidate cathode for proton batteries. Exploiting dual redox-centers of vanadium and iron, VHCF delivers a high specific capacity of 108 mA h g-1. Furthermore, an outstanding rate capability (∼60% of initial value at 100C) and stable cycling for tens of thousands of cycles are also demonstrated. These results are anticipated to inspire searches for more accessible materials and accelerate advances in energy storage devices.