Study on different power and cycling performance of crystalline KxMnO2·nH2O as cathode material for supercapacitors in Li2SO4, Na2SO4, and K2SO4 aqueous electrolytes

The charge/discharge, electrochemical impedance, cyclic voltammogram, and cycling behaviors of crystalline KxMnO2·nH2O as cathode material for supercapacitors in Li2SO4, Na2SO4, and K2SO4 electrolytes were compared. The different power and cycling performance of KxMnO2·nH2O during charge/discharge in the three electrolytes were elucidated by analyzing its composition and structure evolution. Compared with the Li2SO4 and Na2SO4 electrolytes, the highest ionic conductivity of K2SO4 electrolyte, the fastest charge-transfer process and slightest structural evolution of KxMnO2·nH2O during charge/discharge in the K2SO4 electrolyte lead to a superior power and cycling behavior for supercapacitor application.

► KxMnO2·nH2O presents different electrochemical behaviors in three aqueous electrolytes.
► The reasons for the different electrochemical behaviors were elucidated.
► KxMnO2·nH2O displays a superior power and cycling performance in K2SO4 electrolyte.