Synergetic Modulation of Ion Flux and Water Activity in a Single Zn²⁺ Conductor Hydrogel Electrolyte for Ultrastable Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) suffer from dendrite growth, hydrogen evolution reaction (HER), and cathode dissolution. To overcome the above issues, we designed a single Zn2+ conductor hydrogel electrolyte (poly 3-sulfopropyl acrylate zinc, PSPAZn) through UV photopolymerization of the designed monomer zinc salt of SPAZn. The polymerized and fixed anion chains with single Zn2+-conducting characteristics not only promote the uniform distribution of Zn2+ ion flux by charge interaction but also decrease the concentration polarization, leading to nondendrite Zn deposition behavior. Meanwhile, the water activity is significantly reduced due to abundant hydrophilic groups in polymer side chains, effectively inhibiting HER and the dissolution of cathode materials. Consequently, the lifespan of a zinc anode with PSPAZn electrolyte is extended to more than 3000 h, and the Zn/MnO2 full ZIBs also exhibit a high capacity retention of 77.1% after 220 cycles without MnSO4 additive. Such a simple kilogram-scale preparation strategy should offer opportunities for developing practical ZIBs.