All-solid-state asymmetric supercapacitor based on porous cobalt selenide thin films

As a significant semiconductor material, cobalt selenide has enormous potential and extensive application prospects in the field of solar cells, photocatalysis and supercapacitor. In this paper, porous CoSe thin films were successfully fabricated on stainless-steel sheet using a facile, effective electrodeposition technique. Electrochemical tests reveal that the specific capacitance reaches as high as 510 F g−1 at the current density of 1 A g−1 with the capacitance retention of 91% over 5000 cycles. An asymmetric all-solid-state supercapacitor is fabricated using CoSe thin film as the positive electrode and activate carbon as the negative electrode. The combined solid device displays a high area specific capacitance of 18.1 mF cm−2 accompanied with good cycling stability, outstanding flexibility and satisfactory mechanical stability. Furthermore, the solid devices connected in series can power the red light-emitting diodes. The results show great potential for preparing large scale high energy density storage systems.