Origin of capacitance decay for a flower-like δ-MnO2 aqueous supercapacitor electrode: The quantitative surface and electrochemical analysis

Herein, we report the electrochemical energy storage performance of δ-MnO2 (K-birnessite MnO2) as supercapacitor electrode material in Na2SO4 aqueous electrolyte. The electrode exhibited considerable electrochemical performances due to the fast intercalation/deintercalation reactions of Na+ on the pseudocapacitive MnO2 surface. However, a long-term cyclic stability test of the electrode at a low specific current (1 A g−1) demonstrated a decline...