A UV cross-linked gel polymer electrolyte enabling high-rate and high voltage window for quasi-solid-state supercapacitors

Serving as a promising alternative to liquid electrolyte in the application of portable and wearable devices, gel polymer electrolytes (GPEs) are expected to obtain more preferable properties rather than just be satisfied with the merits of high safety and deformability. Here, an easy-operated method is employed to fabricate cross-linked composite polymer membranes used for GPEs assisted by UV irradiation, in which N-doped carbon quantum dots (N-CQDs) and TiO₂ are introduced as photocatalysts and additives to improve the performances of GPEs. Specifically, N-CQDs participate as a cross-linker to construct the inner porous structure, and TiO₂ nanoparticles serve as a stabilizer to improve the electrochemical stability of GPEs under high voltage (3.5 V). The excellent thermal and mechanical stability of the membrane fabricated in this work guarantee the safety of the supercapacitors (SCs). This GPE based SC not only exhibits prominent rate performance (105% capacitance retention at the current density of 40 A/g) and cyclic stability (85% at 1 A/g under 3.5 V after 20,000 cycles), but also displays remarkable energy density (42.88 Wh kg⁻¹) with high power density (19.3 kW kg⁻¹). Moreover, the superior rate and cycling performances of the as-prepared GPE based flexible SCs under flat and bending state confirm the feasibility of its application in flexible energy storage devices.