Through carbon coating to significantly boost the electrochemical performance of nickel oxide

Abstract

NiO is a conventionally low performance electrode material for supercapacitors, especially its extremely low cycling stability. The effect of so far strategies including combination with carbon materials, cobalt ions-doping, and formation of nanostructure for improving the performance of NiO are proven limited. Therefore, it is reasonable to infer that the acknowledged electrochemical mechanism about NiO exists a deviation from the actual situation. In this work, we try to use a synergistic strategy of carbon coating and cobalt ions-doping to obtain the high performance NiO. The investigation results prove that the low cycling stability of NiO originates from its dissolution–recrystallization behavior instead of the acknowledged mechanism of stress-induced structure collapse. The carbon coating and cobalt ions-doping improve the external electron transfer property of NiO and its intrinsic electrical conductivity respectively, thus promoting its electro-activity. Consequently, the modified NiO achieves a high specific capacity of 460.8C g⁻¹ at low current density of 2.0 A g⁻¹ and keeps a high capacity retention of 61.8 % at high current density of 39.3 A g⁻¹. On the other hand, the carbon coating suppresses the dissolution–recrystallization behavior of NiO by its physical hindrance effect, leading to the promotion of its cycling stability from < 10,000 to 80,000 cycles. The results in this work demonstrates the key role of carbon coating in significantly boosting the performance of NiO.