Asymmetric supercapacitors with high energy density based on helical hierarchical porous Na MnO and MoO.

Helical hierarchical porous Na MnO/CC and MoO/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 MnO/CC as the positive electrodes and helical MoO/CC as the negative electrodes, high performance Na MnO/CC//MoO/CC asymmetric supercapacitors (ASCs) are successfully assembled, and they achieve a maximum volume of 2.04 F cm and a maximum energy density of 0.92 mW h cm for the whole device and an excellent cycling stability with 97.22% retention after 6000 cycles.