Fine Tuning Water States in Hydrogels for High Voltage Aqueous Batteries

作者：Chuan Li, Xiaohong Zhu, Donghong Wang, Shuo Yang, Rong Zhang, Pei R. Li, Jun Fan, Hongfei Li, Chunyi Zhi · 发表于：ACS Nano · 年份：2024 · DOI：10.1021/acsnano.3c08398 · 被引用次数：88 · 研究领域：Advanced Battery Materials and Technologies、Advanced battery technologies research、Supercapacitor Materials and Fabrication

Hydrogels are widely used as quasi-solid-state electrolytes in aqueous batteries. However, they are not applicable in high-voltage batteries because the hydrogen evolution reaction cannot be effectively suppressed even when water is incorporated into the polymer network. Herein, by profoundly investigating the states of water molecules in hydrogels, we designed supramolecular hydrogel electrolytes featuring much more nonfreezable bound water and much less free water than that found in conventional hydrogels. Specifically, two strategies are developed to achieve this goal. One strategy is adopting monomers with a variety of hydrophilic groups to enhance the hydrophilicity of polymer chains. The other strategy is incorporating zwitterionic polymers or polymers with counterions as superhydrophilic units. In particular, the nonfreezable bound water content increased from 0.129 in the conventional hydrogel to >0.4 mg mg –1 in the fabricated hydrogels, while the free water content decreased from 1.232 to ∼0.15 mg mg –1 . As a result, a wide electrochemical stability window of up to 3.25 V was obtained with the fabricated hydrogels with low concentrations of incorporated salts and enhanced hydrophilic groups or superhydrophilic groups. The ionic conductivities achieved with our developed hydrogel electrolytes were much higher than those in the conventional highly concentrated salt electrolytes, and their cost is also much lower. The designed supramolecular hydrogel electrolytes endo...