Facile and scalable fabrication of MnO2 nanocrystallines and enhanced electrochemical performance of MnO2/MoS2 inner heterojunction structure for supercapacitor application

Abstract In order to improve the production rate of MnO2 as the excellent supercapacitor materials and enhance the performance of MnO2 based pseudocapacitor, an innovative mechanical method of ultrasonic assisted shear exfoliation is developed to prepare MnO2 nanocrystalline in large quantities, and then the MoS2 composites are deposited by simple magnetron sputtering to form inner heterojunction structure to improve the overall supercapacitor performance. The electrochemical performances of the electrodes fabricated by commodity MnO2 (c-MnO2), sheared MnO2 (s-MnO2) and s-MnO2/MoS2 are studied respectively. The results demonstrate that as-prepared s-MnO2 presents better supercapacitor performance compared with c-MnO2 due to the increase of specific surface area after the shearing process. In addition, the s-MnO2/MoS2 inner heterostructure shows the best electrochemical reversibility, the highest rate capacity, the most excellent specific capacitance (~224 mF cm−2) and the highest conductivity among three working electrode materials because of its high specific surface area and good conductivity. The symmetrical all-solid-state supercapacitor based on s-MnO2/MoS2 is fabricated, its specific capacitance can still maintain 90% after 3000 cycles of charging/discharging process, and this all-solid-state supercapacitor can power a group of 43 light-emitting diodes (LEDs). In addition, the packaged supercapacitor device can gain excellent capacitance performance during bending.