Iron-based fluorophosphate Na 2 FePO 4 F as a cathode for aqueous zinc-ion batteries.

Aqueous zinc-ion batteries form a key post-Li-ion batteries to cater the rising demand for grid storage. Fe-based compounds can be used as economical cathodes for zinc-ion batteries. Herein, we explored iron-based flourophosphate as a potential polyanionic cathode. Involving the Fe 3+/2+ redox process, it can reversibly intercalate Zn 2+ yielding a capacity of ∼80 mA h g -1 , involving a solid-solution mechanism. Polyanionic Fe-based phosphate frameworks can be harnessed as potential low-cost cathodes for secondary zinc-ion batteries.