A high energy density asymmetric supercapacitor based on a CoNi-layered double hydroxide and activated carbon

A high performance asymmetric supercapacitor was fabricated using a CoNi-layered double hydroxide (CoNi-LDH) as the positive electrode and activated carbon as the negative electrode in an electrolyte of 6 M aqueous KOH. The supercapacitor tan be cycled reversibly in a wide potential window of 0-1. 5 V and exhibits a remarkable energy density of 46. 3 Wh . kg(-1) at a power density of 102. 3 W . kg(-1), a high energy density of 25. 6 Wh . kg(-1) even at a high power density of 1 704. 5 W . kg(-1) These values are much higher than those of a symmetric supercapacitor using only activated carbon (6. 9 Wh . kg(-1)). The results can be ascribed to the high specific capacitance and rate capability of the CoNi-LDH, and the complementary potential windows of the two electrodes that increase the working voltage of the supercapacitor. The supercapacitor also exhibits stable cycling with a 84.5% capacitance retention after 1 000 cycles.