A morphology control engineered strategy of Ti3C2Tx/sulfated cellulose nanofibril composite film towards high-performance flexible supercapacitor electrode

2D Ti3C2Tx MXene is an ideal material for fabricating supercapacitor electrodes due to its excellent physical -chemical properties. However, the inherent self-stacking, narrow interlayer spacing, and low general mechani-cal strength limit its application in flexible supercapacitors. Herein, facile structural engineering strategies by drying (vacuum drying, freeze drying, and spin drying) were proposed to fabricate 3D high-performance Ti3C2Tx/sulfated cellulose nanofibril (SCNF) self-supporting film supercapacitor electrodes. Compared with other composite films, the freeze-dried Ti3C2Tx/SCNF composite film exhibited a looser interlayer structure with more space which was conducive to charge storage and ion transport in the electrolyte. Therefore, the freeze-dried Ti3C2Tx/SCNF composite film exhibited a higher specific capacitance (220 F/g) compared to the vacuum-dried Ti3C2Tx/SCNF composite film (191 F/g) and the spin-dried Ti3C2Tx/SCNF composite film (211 F/ g). After 5000 cycles, the capacitance retention rate of the freeze-dried Ti3C2Tx/SCNF film electrode was close to 100 %, showing excellent cycle performance. Meanwhile, the tensile strength of freeze-dried Ti3C2Tx/SCNF composite film (13.7 MPa) was much greater than that of the pure film (7.4 MPa). This work demonstrated a facile strategy for control of Ti3C2Tx/SCNF composite film interlayer structure by drying for fabricating well -designed structured flexible and free-standing supercapacitor electrodes.

Automated summary

Facile structural engineering strategies using drying methods (vacuum drying, freeze drying, and spin drying) were proposed to fabricate high-performance Ti3C2Tx/sulfated cellulose nanofibril (SCNF) self-supporting film supercapacitor electrodes. The freeze-dried Ti3C2Tx/SCNF composite film exhibited a looser interlayer structure with more space, leading to higher specific capacitance and better cycle performance compared to other composite films. Additionally, the freeze-dried composite film showed increased tensile strength. This work provides a simple strategy for controlling the interlayer structure of Ti3C2Tx/SCNF composite films and fabricating well-designed flexible and free-standing supercapacitor electrodes.