High-performance supercapacitor based on 3D Ti₃C₂T_x electrodes and sulfonated lignin gel electrolyte

Supercapacitors are highly efficient energy storage systems. The electrode substances and electrolytes, which form their primary components, are key areas of research for scientists. In this study, the transition metal material Ti₃C₂T_x and Poly(3,4-ethylenedioxythiophene) (PEDOT)-based polyacrylamide dual-crosslinked network polymers with good conductivity are selected as the cathode material and gel electrolyte, respectively. To address issues such as self-aggregation of Ti₃C₂T_x during use, insufficient energy density, and poor dispersibility of 3,4-Ethylenedioxythiophene (EDOT) during the preparation of the hydrogel, polystyrene nanospheres are first used as templates to convert Ti₃C₂T_x from a two-dimensional sheet to a three-dimensional spherical structure, followed by the introduction of bimetallic cobalt-nickel hydroxide (CoNi-OH) to effectively enhance its performance. In addition, sulfonated lignin (SL) is incorporated into the hydrogel to improve the dispersibility of PEDOT in water-based solvents, promoting the development of a uniform hydrogel. The results show that the fabricated composite CoNi-OH/3D Ti₃C₂T_x exhibits a specific capacitance of up to 2020 ± 50F g^-1 at a current density of 1 A g^-1. The assembled asymmetric supercapacitor demonstrates a specific capacitance of 278.3 ± 30F g^-1. At a power density of 750 W kg^-1, it exhibits an energy density of 87 Wh kg^-1. After 7,000 cycles of testing, the device shows a Coulombic efficiency of 99.4 % ± 0.1 % and maintains 83.7 % ± 0.2 % of its initial capacitance at a current density of 3 A g^-1. These findings indicate that the CoNi-OH/3D Ti₃C₂T_x electrodes and PEDOT/SL gel electrolytes have significant potential for development in the energy storage field.