Mechanically robust and highly conductive hydrogels with synergistic cross-linking networks for flexible supercapacitors

Gel electrolyte-based supercapacitors have attracted extensive attention due to their excellent performance for wearable integration. However, traditional gel electrolytes typically struggle to simultaneously meet the dual requirements of mechanical strength and high ionic conductivity, and often lose performance in complex environments. In this work, we utilize betaine hydrochloride (BH) simultaneously as a cross-linking agent, conductive agent, and anti-freezing agent to regulate metal coordination networks and construct a multiple cross-linking system. The synthesized PADBZ gel electrolyte exhibits both high stretchability (tensile strain of 2138%), high strength (tensile stress of 3.1 MPa), high ionic conductivity (15.20 S m −1 ) and good environmental adaptability. The flexible supercapacitor constructed from it demonstrates high areal specific capacitance (158.3 mF cm −2 ) and excellent cycling stability (86.36% capacitance retention after 10,000 cycles), supporting good operation under various complex working environments. This strategy opens new avenues for designing multifunctional integrated gel electrolytes and their applications in flexible energy storage devices.