Multiple Electron Transfers Enable High‐Capacity Cathode Through Stable Anionic Redox

Abstract

Abstract Single‐electron transfer, low alkali metal contents, and large‐molecular masses limit the capacity of cathodes. This study uses a cost‐effective and light‐molecular‐mass orthosilicate material, K 2 FeSiO 4 , with a high initial potassium content, as a cathode for potassium‐ion batteries to enable the transfer of more than one electron. Despite the limited valence change of Fe ions during cycling, K 2 FeSiO 4 can undergo multiple electron transfers via successive oxygen anionic redox reactions to generate a high reversible capacity. Although the formation of O‒O dimers in K 2 FeSiO 4 occur upon removing large amounts of potassium, the strong binding effect of Si on O mitigates irreversible oxygen release and voltage degradation during cycling. K 2 FeSiO 4 achieves 236 mAh g −1 at 50 mA g −1 , with an energy density of 520 Wh kg −1 , which can be comparable with commercial LiFePO 4 materials. Moreover, it also exhibits 1400 stable cycles under high‐current conditions. These findings enhance the potential commercialization prospects for potassium‐ion batteries.