MnO2 loaded flower-like carbon microspheres derived from polyimides for high-performance supercapacitors

Herein, the flower-like carbon microspheres derived from polyimides(PI) are prepared by solvothermal method and carbonization. Then, the MnO2 loaded carbon microflowers are obtained by hydrothermal process. The influences of mass ratio of carbon microflowers to KMnO4, hydrothermal time and temperature on the electrochemical behaviors of the composites are investigated. After optimizing conditions, the MC(1:3)-80-8 exhibits a higher specific capacity of 145.40 mAh g-1 (523.43 F g-1) at 0.5 A g-1. Furthermore, the optimum composite electrodes are fabricated into a symmetric supercapacitor(SC), which attains an energy density of 16.7 Wh kg- 1, coupled with a power density of 193 W kg- 1. The SC exhibits a long-time cycle stability of 93.5% after 20,000 charge and discharge cycles at 1 A g-1. Besides, only one SC can successfully light a LED more than three minutes. Therefore, the MnO2 loaded flower-like carbon microsphere composites are one kind of valuable candidates for electrode materials of supercapacitors.