Boosting Dendrite-Free Zinc Anode with Strongly Polar Functional Group Terminated Hydrogel Electrolyte for High-Safe Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have become a promising energy storage device due to their low cost and high security. However, the severe dendrite growth and side reactions on metallic zinc (Zn) anode hamper their commercial implementation. Herein, a strongly electronegative trifluoroborate anion (& horbar;BF3-) functionalized polyacrylamide hydrogel (PAME) is well-designed and constructed as the quasi-solid-state electrolyte to overcome these obstacles. The PAME chain segments terminated with strongly polar functional groups promote the conversion of water molecules from free water to bound water through the enhanced hydrogen bonding interaction to alleviate the side reactions. Furthermore, the PAME electrolyte featured with hierarchically porous structure and enhanced electrostatic interaction among the & horbar;BF3- groups, and Zn2+ ions homogenizes the high-flux Zn ion transport and induce the uniform deposition to restrain dendrite growth. Consequently, the assembled Zn & Vert;PAME & Vert;Zn batteries deliver remarkable cycling stability over 1800 h at 1 mA cm-2 and 900 h at 15 mA cm-2. Additionally, the constructed Zn & Vert;PAME & Vert;MnO2 full cells achieve a reversible capacity of 202 mAh g-1 at 2.0 A g-1 with a capacity retention rate of 91.4% over 500 cycles. This work sheds light on constructing the strongly polar hydrogel electrolyte to boost free-dendrite Zn anodes for long-lifespan AZIBs.