Sea urchin-like asphalt-based graphene quantum dots/nickel cobalt bimetallic hydroxide for all-solid-state asymmetric supercapacitors

Composite materials combining carbon materials and transition metal hydroxides offer advantages such as high specific capacitance, high conductivity and low cost. However, the reported energy density of supercapacitors has been relatively low, limiting their widespread application. In this study, a high-performance hybrid electrode material, consisting of asphalt-based graphene quantum dots (AGQDs) and nickel-cobalt layered double hydroxide (NiCo-LDH) sea urchin-like structure, was successfully synthesized using a one-step hydrothermal method. By fully leveraging the cooperative interactions between NiCo-LDH and AGQDs, the electrode's charge transfer and storage capacity were significantly enhanced, demonstrating excellent electron transfer ability and electrochemical characteristics. The AGQDs/NiCo-LDH composite exhibited a specific capacitance of 1671.27 F g(-1) at 1 A g(-1), along with outstanding cyclic stability (retaining 75.94 % of capacitance after 5000 cycles). The assembled AGQDs/NiCo-LDH//AC Asymmetric supercapacitors (ASC) demonstrated a high energy density of 112.63 Wh kg(-1) at a power density of 750.83 W kg(-1). This breakthrough establishes AGQDs as a leading contender for high-performance electrochemical energy storage systems, opening up new prospects for sustainable and efficient energy solutions.