A freezing-tolerant superior proton conductive hydrogel comprised of sulfonated poly(ether-ether-ketone) and poly(vinyl-alcohol) as a quasi-solid-state electrolyte in a proton battery

Aqueous proton batteries (APBs) are regarded as one of the most promising energy storage devices for the next-generation batteries owing to their high safety, high power density and environmental friendliness, while the study of their electrolytes is still in the infancy regarding metal-based batteries. Herein, we present a double-network hydrogel as a quasi-solid-state electrolyte in a proton battery. Sulfonated poly(ether-ether-ketone) and an ethylene glycol/water solvent are incorporated within the poly(vinyl alcohol) hydrogel network to enhance the mechanical properties, resulting in a tensile strength of 4.37 MPa and a toughness strain of 663%. This composite also exhibits remarkable proton conductivity (8.8 x 10-3/1.1 x 10-1 S cm-1 at -35/70 & DEG;C, ambient humidity) and low temperature tolerance (-50 & DEG;C). A quasi-solid-state proton "rocking-chair" battery demonstrates stable cycling and high rate capability (77% capacity retention after 500 cycles at 1 A g-1 at 25 & DEG;C and 95% capacity retention rate over 100 cycles at -20 & DEG;C). This study provides a new possible practical application of hydrogel as a proton battery electrolyte, which could advance the development of proton electrochemical devices. The double-network hydrogel as a quasi-solid-state electrolyte in a proton battery for the first time, which shows stable cycling and high rate capability.