Incorporating Interstitial Carbon Atoms and Graphene Quantum Dots in Crystalline Ni(OH)Cl for Ultrastable and Superior Rate Supercapacitors

Abstract Despite their high theoretical capacity, Ni‐based materials are hindered by significant issues such as structural degradation, low intrinsic conductivity, and sluggish kinetics, resulting in poor stability and rate performance. Herein, the Ni(OH)Cl‐ICA‐GQDs incorporated with interstitial carbon atoms (ICAs) and graphene quantum dots (GQDs) are proposed to radically reverse its structural stability and electronic transport capability. ICAs can induce lattice micro‐strain that adjusts bond lengths and angles, leading to intrinsically ameliorated structural stability under alkaline and even acidic conditions. GQDs promote the formation of micro‐conductive circuits, optimizing the electronic configuration and redox kinetics. As a result, the Ni(OH)Cl‐ICA‐GQDs electrode achieves exceptional cyclic stability (91.5% retention after 20 000 cycles versus 70.3% retention after 2000 cycles for Ni(OH)Cl) and remarkable rate capability (312C g −1 at 100 A g −1 vs 109C g −1 at 50 A g −1 for Ni(OH)Cl). Furthermore, the Ni(OH)Cl‐ICA‐GQDs//AC hybrid supercapacitor achieves an ultrahigh power density of 41.5 kW kg −1 with an energy density of 28.8 Wh kg −1 , surpassing most Ni‐based supercapacitors. This approach offers a promising strategy for the precise modification of high‐performance electrodes for energy storage applications.