Solvent triggering assembly of self-supported MXene hydrogel for high performance asymmetric supercapacitors

Constructing 3D porous structure of MXene (Ti3C2Tx) is an efficient approach to prevent nanosheets restacking and realize prominent electrochemical functionality. However, the assembly of self-supported 3D Ti3C2Tx architecture is difficult due to the inherent rigidity and superior hydrophilicity of Ti3C2Tx nanosheets. Herein, a solvent-triggering gelation strategy is developed using polar aprotic N,N-Dimethylformamide and polar protic H2O as co-solvent to enhance hydrogen bonding and Ti-O-Ti covalent bonding between Ti3C2Tx nanosheets. Thereby, self-supported Ti3C2Tx hydrogel (MH12/5:5) in absence of any crosslinkers or substrates has been successfully fabricated. The MH12/5:5 hydrogel exhibits excellent specific capacitance of 384.4 F g1 and superb rate capability of 61 % in a broad current density range of 1–100 A g−1. Asymmetric supercapacitor has been assembled using MH12/5:5 hydrogel as negative electrode and a polyaniline hydrogel as positive electrode, which presents high energy density of 21.2 Wh kg−1. This solvent-triggering gelation strategy points toward a promising direction to develop self-supported MXene hydrogels for high performance energy storage devices.