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 can 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 1704.5 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 1000 cycles.