Hydrogen bond acceptor lined hydrogel electrolyte toward Dendrite-Free aqueous Zn ion batteries with low temperature adaptability

Flexible aqueous Zn-ion batteries (AZIBs) are recognized as a prospective energy storage device benefiting from their high security, low price and competitive electrochemical performance. But there are two drawbacks that seriously hinder the actual utilization of AZIBs, which are the dendrite growth of zinc anodes and the freezing of liquid electrolytes at subzero temperatures. To this end, functional three-dimensional network hydrogel electrolyte lined with hydrogen bond acceptor (denoted as PDC-20 gel electrolyte) was designed to address this challenge. The hydrogen bond acceptor dimethyl sulfoxide (DMSO), H2O and polymer chains can form a ternary hydrogen bond to improve mechanical performances of the hydrogel electrolyte. Meanwhile, DMSO breaks the hydrogen bond of water, greatly reduces the freezing point of the hydrogel electrolyte, reconstructs the solvation structure of Zn2+ in the hydrogel, optimizes the deposition kinetics of Zn2+, and ultimately achieves effective inhibition of Zn dendrites and side reactions. Therefore, the Zn//Zn symmetry battery with PDC-20 gel electrolyte can achieve a stable plating/stripping process for 1300 h at 2 mA cm−2 with set capacity of 2 mAh cm−2. The assembled Zn//MnO2/CNT battery has a large specific capacity of 238.4 mAh/g and a high cycle stability of 5000 cycles at 2 A/g at room temperature. A high ion conductivity of 2.82 mS cm−1 and a specific capacity of 160.5 mAh/g were still achieved at −20 °C. This study offers an inspiring strategy and good feasibility to design high performance antifreeze flexible batteries by introducing hydrogen bond acceptor.