Poly(vinyl alcohol) hydrogel containing deep eutectic solvents as electrolytes with co-nonsolvency effect for anti-freezing zinc-ion hybrid supercapacitors

An anti-freezing, low-cost, and high-strength poly(vinyl alcohol) (PVA) hydrogel electrolyte containing Zn(ClO 4 ) 2 ·6H 2 O/ethylene glycol (EG) deep eutectic solvents (DES) and water is designed based on the effect of co-nonsolvency. The sodium dodecyl benzene sulfonate (SDBS) is proposed as an additive to regulate the solvation shell, releasing more ClO 4 − ions, and H 2 O in the solvation structure. The ClO 4 − ions, EG, and SDBS synergistically destroy the consecutive hydrogen bonding network among H 2 O molecules, depressing the solid-liquid transition temperature of the DES-SxP gel to −56.98 °C. Moreover, the generation of new H-bonds among ClO 4 − ions, EG, and SDBS with H 2 O immeasurably prohibits the activity of H 2 O, disrupting the hazardous side reactions as well as dendrites related to H 2 O molecules and extremely extending the electrochemical window (3.04 V). The assembled Zn||Zn symmetrical cells can cycle over 980 h at 1 mA cm −2 at room temperature. The internal resistance of zinc-ion hybrid supercapacitors declined to 17.02 Ω and the cyclic stability of zinc-ion hybrid supercapacitors improved to 8000 cycles with a considerable specific capacity of 88.75 mAh g −1 at 5 A g −1 and 20000 cycles with 65.71 mAh g −1 at 10 A g −1 under −20 °C.