Realization of an anion insertion mechanism for high-rate electrochemical energy storage in highly crystalline few-layered potassium manganese dioxide nanosheets

Aqueous anionic energy storage with a non-flammable electrolyte has the advantage of high power density but suffers from limitations in terms of cycling performance. Herein, we report few-layered potassium manganese dioxide (K0.5Mn2O4.3(H2O)(0.5)) with high crystallinity that exhibits high-capacity anion storage and rapid insertion in aqueous K2SO4 electrolyte. In contrast to the storage of cations such as H+, Li+, Na+, and K+, the insertion of SO42- and OH- anions inhibits the migration of cations in the birnessite anode. The nanosheets with rapid anion insertion have excellent electrochemical properties, including a specific volumetric capacitance of 350 F cm(-3) at a current density of 1 mA cm(-2) at a mass loading of 10 mg cm(-2) and even 315 F cm(-3) at 20 mA cm(-2), showing their extremely high-rate performance and stable cycling performance of up to 10 000 cycles with 85% capacity retention. This impressive electrode material uses anion storage technology to complement existing cation storage for the preparation of a material that exhibits long-lifespan and high-power energy storage.

Automated summary

This study reports on aqueous anionic energy storage based on few-layered potassium manganese dioxide. This material exhibits high-capacity anion storage and rapid insertion in aqueous K2SO4 electrolyte, showing extremely high-rate performance and stable cycling performance.