Nitrogen-doped laser-induced graphene electrodes were fabricated by one-stepin situCO₂laser pyrolysis, exhibiting superior electrochemical performance for flexible supercapacitor applications.

The micro/nanostructure of electrode materials is one of the key factors affecting the performance of supercapacitors. Here, a hybrid electrode composed of nickel–cobalt layered double hydroxide (NC-LDH) nanosheets supported on vertical graphene fibers was designed for flexible supercapacitors. An efficient and low-cost laser-induced technology was explored to synthesize vertical graphene fibers using polyphenylene sulfide (PPS) as a precursor. By double laser writing in two directions perpendicular to each other, laser-induced graphene (LIG) fibers with improved conductivity and optimized morphology were achieved. As a result, porous NC-LDH nanosheets with high specific capacitance can be uniformly loaded onto LIG fibers by the electrodeposition method. The as-obtained composite with fast electron transfer and efficient ion transport properties was used as a supercapacitor electrode, achieving an ultrahigh specific capacitance of 4503 mF cm⁻² at 1.0 mA cm⁻² in a standard three-electrode system. Furthermore, a flexible asymmetric supercapacitor (ASC) was successfully assembled using NC-LDH/LIG as the positive electrode and activated carbon as the negative electrode with the PVA–KOH gel electrolyte, obtaining a high energy density of 219 μW h cm⁻² at a power density of 378 μW cm⁻². These excellent electrochemical properties are attributed to the rational structural design of the electrode and the synergistic effect of each electrode component, which exhibits great application prospects in flexible energy storage devices.

Enhancing the energy storage capacity of supercapacitors is facing great challenges. Converting solar energy into heat energy has emerged as a promising strategy to enhance the capacity of energy storage devices by elevating their working temperature, especially under low-temperature conditions. Unlike traditional energy storage devices, higher requirements are put forward for the cycle stability of solar thermal device electrodes. Herein, a novel light-absorbing structure of supercapacitor electrodes composed of 3D porous graphene and polypyrrole is established. The uniform composite structure and matching thermal expansion properties of the composite electrode endows the fabricated solar-thermal micro-supercapacitor (ST-MSC) with superior capacitance and cycling stability. Under one solar irradiation, the temperature of the ST-MSC increases to 60 °C, leading to a 4.8-fold increase in the specific capacitance and energy density (up to 2754 mF cm⁻² and 646.6 µW h cm⁻², respectively); the ST-MSC exhibits excellent cycle stability with 85.8% capacitance retention after 10 000 cycles, which is much better than most of the reported ST-MSCs. Moreover, at a low temperature of −30 °C, the severely attenuated capacitance performance of the ST-MSC is greatly improved under one solar irradiation to a level close to that at room temperature. This work provides a new strategy for designing solar thermal electrodes and their derived high-performance energy storage devices.