High-loading cobalt-doped manganese tetroxide on carbon cloth as an electrode material for high-performance zinc ion hybrid capacitors

Abstract

Despite its quick development, zinc-ion hybrid capacitors (ZIHCs) are still in their infancy regarding the field of producing high-loading (8–10 mg cm−2) and high area energy density equivalent to that of zinc-ion batteries. This is because high-loading electrode materials have sluggish electron transport and ion migration kinetics. In the present work, cobalt-doped trimanganese tetroxide nanoparticles are fabricated and distributed uniformly over the flexible carbon cloth surface with a high loading of 14.2 mg cm−2 for large-scale production of ZIHCs. Owing to the enhancement of the [MnO6] octahedron conductivity and the diffusion coefficient of Zn2+ to embedding and de-embedding the Co–Mn3O4 cathode after Co doping, the as-prepared liquid ZIHC demonstrates excellent electrochemical performance and high capacity. The area capacitance of the ZIHC can reach 4102.56 mF cm−2 at a current density of 2 mA cm−2 with a maximum area energy density of 2166.70 μWh cm−2, which is comparable to the energy capacity of zinc-ion batteries. The quasi-solid flexible ZIHCs with the Co–Mn3O4 cathode and the activated carbon anode can realize an excellent energy density of 672.45 μWh cm−2 at a power density of 1.8 mW cm−2 with high mechanical flexibility, which has a potential to develop a new generation of flexible energy storage devices.