Research on Zn doping α-MnO₂ of NH₄⁺ hybrid capacitor and its electrochemical performance

The electrode materials of NH₄⁺ hybrid capacitors are easily dissolved in acidic electrolyte, which leads to the collapse of bulk structure of the material, and excessively rapid capacity decay, thus limiting the extensive application of NH₄⁺ hybrid capacitors. The tunnel structured Zn_xMnO₂ materials are prepared through one step hydrothermal method, which are characterized by XRD, SEM, FTIR, and XPS for Zn_xMnO₂ cathode. Electrochemical performance test of Zn_xMnO₂ materials shows the capacity of Zn_xMnO₂ material can achieve 350 F/g upon stabilization with current density of 0.5 A/g. A novel ammonium ion hybrid supercapacitor (A-HSC) is constructed with tunneling Zn_xMnO₂ as the cathode material and commercial activated carbon as the negative electrode; The capacitor has a high voltage window which can work stably within in the voltage window of 0-1.6 V and provides energy density of 86 Wh/kg. The excellent cycling stability with 80% capacity remains after 5 000 cycles at a current density of 5 A/g. The hybrid capacitor proves that Zn_xMnO₂ is a promising NH₄⁺ storage electrode material, which is significant for the construction of a new generation of aqueous ammonium ion capacitors.