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

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.