Super-Elastic and Temperature-Tolerant Hydrogel Electrodes for Supercapacitors via MXene Enhanced Ice-Templating Synthesis.

Developing flexible energy storage devices with good deformation resistance under extreme operating conditions is highly desirable yet remains very challenging. Super-elastic MXene-enhanced polyvinyl alcohol/polyaniline (AMPH) hydrogel electrodes are designed and synthesized through vertical gradient ice templating-induced polymerization. This approach allows for the unidirectional growth of polyaniline (PANI) and 2D MXene layers along the elongated arrayed ice crystals in a controlled manner. The resulting 3D unidirectional AMPH hydrogel exhibits inherent stretchability and electronic conductivity, with the ability to completely recover its shape even under extreme conditions, such as 500% tensile strain, 50% compressive strain. The presence of MXene in the hydrogel electrode enhances its resilience to mechanical compression and stretching, resulting in less variation in resistance. AMPH has a specific capacitance of 130.68 and 88.02 mF cm at a current density of 0.2 and 2 mA cm, respectively, and retains 90% and 70% of its original capacitance at elongation of 100% and 200%, respectively. AMPH-based supercapacitors demonstrate exceptional performance in high salinity environments and wide temperature ranges (-30-80 °C). The high electrochemical activity, temperature tolerance, and mechanical robustness of AMPH-based supercapacitor endow it promising as the power supply for flexible and wearable electronic devices.