Phase-Separation-Mediated “Sea–Island” Microstructure for Strong and Tough Hydrogel Electrolytes for Zinc Metal Batteries

Due to the proliferation of wearable and implantable medical electronic devices, there have been extensive explorations into the utilization of hydrogel electrolytes with exceptional flexibility in zinc metal batteries. The construction of dual-network hydrogels can effectively yield hydrogels possessing high mechanical properties and fatigue resistance. However, the poor compatibility between two polymer networks causes a fact that achieving a uniform dual-network structure becomes challenging. In such cases, the distribution of these two polymer networks significantly impacts the performance of the hydrogels. In this study, a "sea–island" hydrogel is designed by employing a nonsolvent-induced phase separation strategy involving poly(ether sulfone) within a homogeneous poly(vinyl alcohol) hydrogel network. The continuous poly(vinyl alcohol) network ensures the flexibility and ionic conductivity of the hydrogel, while the dispersed poly(ether sulfone) network enhances its strength and facilitates zinc ion transport. The results demonstrate that this unique structured hydrogel electrolyte exhibits a remarkable battery lifetime of 2, 100 h at an area capacity of 1 mAh cm–2 and a current density of 1 mA cm–2. Moreover, the fully flexible all-in-one zinc metal battery fabricated based on this hydrogel manifests exceptional mechanical and electrochemical properties. This study presents a promising approach for constructing advanced integrated flexible zinc metal batteries.