Cellulose Reinforced Eutectogel Electrolyte for Flexible Zinc-Ion Hybrid Supercapacitors

Abstract

The eutectogel electrolyte has shown significant potential for zinc-ion hybrid supercapacitors (ZHSCs) due to its cost-effectiveness, temperature resistance, and high safety. However, the poor mechanical strength and complex preparation process of the eutectogel electrolyte have become the main barriers to the practical application of ZHSCs. Herein, we developed a cellulose reinforced polyacrylamide (PAM)-based eutectogel (CPG) electrolyte for ZHSCs via an in situ one-step radical polymerization process. The dispersed cellulosic fiber plays a crucial role in stabilizing the network structure and widening the pore size of eutectogel, which improves mechanical properties and ion transport rate. Furthermore, the ternary deep eutectic solvent including choline chloride, urea, ethylene glycol, and ZnCl2 endows eutectogel with intrinsic thermal stability, antidrying (with weight remaining almost unchanged after 20 days), and antifreezing properties. Thus, the as-prepared eutectogel electrolyte exhibits decent mechanical properties (tensile strength of 35.3 kPa and compressive strength of 117.0 kPa), high zinc ion transference number (0.68), superb flexibility, and good adhesion. With these superiorities, the symmetric cell employing the CPG electrolyte achieves stable cycling over 1390 h, and the assembled flexible ZHSC demonstrates favorable mechanical deformation adaptability under various severe conditions and operational feasibility in a wide temperature range from −15 to 60 °C. This work offers a promising strategy for designing multifunctional eutectogel electrolytes for applications in flexible ZHSCs.