Hydrogel Electrolyte Film with Low‐Temperature Adaptability for Flexible Quasi‐Solid‐State Batteries

Abstract Considering the merits and shortcomings of conventional hydrogels in terms of low‐temperature adaptability, a new type of hydrogel electrolyte, reinforced by hydrogen bonding and containing just 6.8% water, is fabricated. This hydrogel film exhibits a high ionic conductivity of 3.9 mS cm −1 at room temperature and maintains its flexibility even at −40 °C. The hydrogel‐based quasi‐solid‐state cell shows good cyclic stability performance, retaining 80.3% of its initial capacity after 800 cycles. Furthermore, it performs well in sub‐zero conditions, retaining 89.6% of its capacity at −30 °C (0.5C) and releasing 56.4 mAh g −1 at −40 °C (0.1C). Notably, the cyclic stability of the LTE‐based flexible full cell maintains well even under 180° bending and 15% stretching. This can be attributed to the polymer network with hydrophilic groups, which disrupts the hydrogen‐bond networks of original water molecules and forms abundant new hydrogen bonding interactions between the polymer chains and water molecules. These interactions are crucial for improving low‐temperature adaptability. Overall, this work offers a promising approach to creating low‐temperature adaptable hydrogels that can be used to develop wearable energy‐storage devices.