Impact of cellulose nanofibril modification on the electrochemical performance of Ti3C2Tx-based supercapacitors

Abstract

Two-dimensional MXenes (Ti₃C₂T_x) exhibit metallic conductivity and high capacitance, making them a promising electrode material for flexible supercapacitors. However, the self-stacking of Ti₃C₂T_x nanosheets hinders ion transport and diffusion, adversely affecting electrochemical performance. Here, we study the incorporation of one-dimensional (1D) cellulose nanofibrils (CNFs) with Ti₃C₂T_x via interfacial interactions to show the possibility of preventing the close packing of conductive nanosheets, improving electrolyte ion transport and enhancing the mechanical strength and robustness of the dried material, enabling the fabrication of flexible, self-supporting hybrid films. For this purpose, we consider the impact of surface-modified CNFs on the structure and performance of Ti₃C₂T_x composite electrodes. Sulfated CNFs (SCNFs) are evaluated as scaffolding materials and compared with unmodified CNFs and carboxymethylated CNFs (CMCNFs). The Ti₃C₂T_x/SCNF hybrid electrode is demonstrated to achieve a specific capacitance of 218.3 F g⁻¹ at 1 A g⁻¹ and stable charge/discharge cycling. A symmetric solid-state supercapacitor is assembled with Ti₃C₂T_x/SCNF hybrid electrodes and shown to deliver an excellent specific capacitance of 241.2 mF cm⁻², an energy density of 12.3 µWh cm⁻² at a power density of 148.4 µW cm⁻². Notably, the device maintains nearly constant capacitance under 180° bending. Overall, this work highlights an effective approach for developing high-performance flexible electrodes, advancing the development of next-generation energy storage devices.