Flexible zinc ion hybrid capacitors with high energy density and long cycling life based on nanoneedle-like MnO2@CC electrode

Abstract

Zinc ion hybrid capacitor (ZIHC), as a new type of energy storage device, show great potential due to their high energy density and power density. However, their undesired structure deformation and poor cycling stability urgently need to be addressed. Herein, we developed a flexible ZIHC device with nanoneedle-like MnO2@CC as the cathode electrode and activated carbon derived from biomass material loofah as the anode electrode. During the charging generation, the by-products of Zn4(OH)6SO4⋅xH2O is proved to formed on the surface of the electrode, which is one of the key factors for the high capacity. Therefore, the flexible ZIHC device with ZnCl2/MnSO4/PVA electrolyte presents a good specific capacity of 1217.4 mF cm−2 at 2 mA cm−2, and high energy-power densities characteristic (676.3 μWh cm−2 at 2000 μW cm−2). More importantly, the device can maintain good performance after bended repeatedly, and the capacity of the device did not decay after 5000 cycles in aqueous electrolyte. The results of our study contribute greatly to the development of safe, reliable, and high electrochemical performance flexible ZIHC.