Polyzwitterionic cross-linked double network hydrogel electrolyte enabling high-stable Zn anode

Zn metal anode suffers from dendrite issues and passive byproducts, which severely plagues the practical application of aqueous Zn metal batteries. Herein, a polyzwitterionic cross-linked double network hydrogel electrolyte composed of physical crosslinking (hyaluronic acid) and chemical crosslinking (synthetic zwitterionic monomer copolymerized with acrylamide) is introduced to overcome these obstacles. On the one hand, highly hydrophilic physical network provides an energy dissipation channel to buffer stress and builds a H2O-poor interface to avoid side reactions. On the other hand, the charged groups (sulfonic and imidazolyl) in chemical crosslinking structure build anion/cation transport channels to boost ions' kinetics migration and regulate the typical solvent structure [Zn(H2O)6]2+ to R-SO3− [Zn(H2O)4]2+, with uniform electric field distribution and significant resistance to dendrites and parasitic reactions. Based on the above functions, the symmetric zinc cell exhibits superior cycle stability for more than 420 h at a high current density of 5 mA·cm−2, and Zn∥MnO2 full cell has a reversible specific capacity of 150 mAh·g−1 after 1000 cycles at 2 C with this hydrogel electrolyte. Furthermore, the pouch cell delivers impressive flexibility and cyclability for energy-storage applications.