A mechanically robust all-solid-state supercapacitor based on a highly conductive double-network hydrogel electrolyte and Ti3C2Tx MXene electrode with anti-freezing property

Hydrogels are peculiarly attractive electrolyte materials for constructing flexible and secure all-solid-state supercapacitors due to their mechanical flexibility, ionic conductivity and noninflammability. However, upon severe mechanical stresses, hydrogel electrolyte-based supercapacitors will undergo irreversible structural damage, which results in dramatically fluctuant energy output. Additionally, invalid mechanical flexibility and serious capacitance degradation at subzero temperature are also urgent issues to be addressed. Herein, a mechanically reliable, exceptional-performance and anti-freezing all-solid-state supercapacitor is constructed from a highly ionic conductive double-network (DN) hydrogel electrolyte, intrinsically powerful Ti3C2Tx MXene film electrode and carbon nanotube film current collector. The DN hydrogel possesses impressive ionic conductivities of 4.8 and 3.6 S m−1 at room temperature and −20 °C, respectively, together with an effective energy-dissipation mechanism and freezing tolerance (