Asymmetric supercapacitors with high energy density based on helical hierarchical porous NaxMnO2 and MoO2

Abstract

Helical hierarchical porous Na_xMnO₂/CC and MoO₂/CC, which are assembled from nanosheets and nanoparticles, respectively, are fabricated using a simple electrodeposition method. These unique helical porous structures enable electrodes to have a high capacitance and an outstanding cycling performance. Based on the helical Na_xMnO₂/CC as the positive electrodes and helical MoO₂/CC as the negative electrodes, high performance Na_xMnO₂/CC//MoO₂/CC asymmetric supercapacitors (ASCs) are successfully assembled, and they achieve a maximum volume C_sp of 2.04 F cm⁻³ and a maximum energy density of 0.92 mW h cm⁻³ for the whole device and an excellent cycling stability with 97.22% C_sp retention after 6000 cycles.