Self‐Supporting CuCo 2 S 4 Microspheres for High‐Performance Flexible Asymmetric Solid‐State Supercapacitors

Copper cobalt sulfide (CuCo 2 S 4 ) microspheres were grown directly on a carbon cloth (CC) substrate via a facile hydrothermal synthesis route. The possible formation mechanism of flower‐like CuCo 2 S 4 microspheres was also discussed. The resultant composite was explored as a binder‐free electrode for supercapacitors, delivering a high capacitance of 166.67 mAh g –1 at 1 A g –1 , excellent rate capability (108.33 mAh g –1 at 10 A g –1 ) and pronounced long‐term cyclability up to 3000 cycles. A flexible solid state supercapacitor was also assembled with binder‐free electrode materials and exhibits an energy density of 17.12 Wh kg –1 at a power density of 194.4 W kg –1 , and a good cycling stability with 78.4 % of initial capacity retention rate can be maintained at 1 A g –1 after 3000 cycles. In addition, the electrochemical performance of supercapacitor device is still quite stable even if it was bent 180° or twisted 150°. Two charged CuCo 2 S 4 /CC//AC supercapacitors in series can light 1 red color LED's (2 V) for 5 minutes. All these features indicate that the CuCo 2 S 4 /CC device is an excellent candidate for energy storage.