Toward Superior Electrochemical Capacitance with Hierarchically Nanostructured Polypyrrole/MXene Hybrid Hydrogel Modified by Lignosulfonate

Although the Ti3C2 MXene has demonstrated exceptional promise for supercapacitor applications, its practical implementation is limited by its inherent tendency of undergoing restacking and oxidation. Herein, we propose a facile self-assembly strategy of in situ polymerization to construct lignosulfonate (LS)-modified polypyrrole (PPy)/MXene hybrid hydrogels with a hierarchical porous structure. The formed PPy nanoparticles and coating layer effectively prevent MXene restacking and oxidation, while enhancing electrical conductivity and electrochemical activity. Furthermore, LS contributes redox-active quinone groups, further promoting electron and proton storage and exchange. The hierarchical heterostructure provides continuous ion-diffusion pathways and exposes abundant electroactive sites, yielding a remarkable specific capacitance of 663.7 F g–1 at 0.2 A g–1 with 81.2% capacitance retention and 95.3% Coulombic efficiency after 5000 cycles at 2 A g–1. Assembled solid-state symmetric supercapacitors achieve an exceptional energy density of 29.3 W h kg–1 at 200 W kg–1 and maintain 12.4 W h kg–1 at an ultrahigh power density of 3200 W kg–1, alongside fairly good cycling stability (87.6% capacitance retention) and a Coulombic efficiency of 94.1% over 5000 cycles. These results highlight the multifunctionality of the LS component within the hybrid hydrogels─simultaneously stabilizing the structure, improving electrical conductivity, generating cross-links, and contributing toward pseudocapacitance─establishing LS-modified PPy/MXene hybrid hydrogels as high-performance electrode materials for advanced supercapacitor applications.