Flexible Zn-ion hybrid supercapacitor enabled by N-Doped MnO2 cathode with high energy density and ultra-long cycle life

Abstract

To meet the higher requirements for green energy, high-performance renewable energy technology based on earth‑abundant materials is essential. Aqueous zinc-ion hybrid supercapacitors (ZSC) have been regarded as an attractive candidate for sustainable electrochemical energy storage device combining the advantages of batteries and supercapacitors, but their unsatisfactory cycling stability and low energy density remain a problem to be solved. Herein, nitrogen-doped MnO₂ (N-MnO₂) nanowalls were synthesized by in situ deposition, which provides rich ion transport pathway and accelerates the extraction/insertion of zinc ions. As a result, N-MnO₂ anode can be assembled to an aqueous zinc-ion hybrid capacitor with AC cathodes, presenting a high energy density of 712.5 μWh cm⁻² at a power density of 1000 μW cm⁻² (1 mA cm⁻²) and excellent cycle stability with a capacity retention rate of 92.9 % in 25,000 charge-discharge cycles. In addition, the flexible hybrid supercapacitor exhibits excellent mechanical flexibility, and the electrochemical performance remains stable under different bending angles. This work shows that ZSC device based on N-MnO₂ nanowalls hold great potential for new energy storage devices.