Graphene instead of graphite doping potassium ferrate for intrinsically reforming both conductivity and stability of super-iron(vi) battery

Abstract

Graphene possesses an intrinsic electronic structure and electrochemical properties that theoretically compensate for the low conductivity and poor stability of ferrate(VI) salts. A graphene coating strategy is proposed to replace graphite conductive additives, intrinsically enhancing both the conductivity and stability of potassium ferrate(VI) for battery applications. The intrinsic modification of ferrates using graphene or graphene oxide (GO) yields materials termed graphene-modified ferrates or GO-modified ferrates. Graphene's exceptional electrical conductivity significantly improves the electrical properties of ferrate(VI) battery materials. Carbon atoms in graphene provide lone-pair electrons that coordinate with ferrates, forming an electron-coordination composite structure. This interaction alleviates the electron deficiency associated with iron(VI) in these materials, facilitating improved charge transfer and contributing to enhanced overall battery performance. Electrochemical evaluations demonstrate that the hydrolysis stability of coated potassium ferrate is significantly influenced by both the coating type and the applied heat treatment. Notably, the graphene-modified ferrate(VI) battery exhibits an extended discharge duration, characterized by a prolonged time for the voltage to decrease to 0.7 V, achieving a discharge efficiency of 49%. Furthermore, the graphene coating optimizes charge transfer, culminating in a discharge efficiency of up to 82%. These findings provide robust evidence for advancing electrode materials in super-iron battery applications.