Iron Phosphate Hydroxide Hydrate As a Novel Anode Material for Advanced Aqueous Full Potassium-Ion Batteries

The development of aqueous potassium-ion batteries is limited by the lack of suitable anode materials. Here, a novel anode material, iron phosphate hydroxide hydrate Fe1.19PO4(OH)0.18(H2O)0.3, was introduced and synthesized, which delivers considerable reversible capacities of 80 mA h g-1 at 0.05 A g-1. An aqueous full potassium-ion battery assembled with the K2Zn3(Fe(CN)6)2 cathode exhibits 80% capacity retention after 1000 cycles.