A Hydrogel Electrolyte-Based Zn-CO₂ Battery with Improved Life

Environmental-friendly aqueous Zn-CO₂ batteries present bifunctional potentials of achieving carbon neutrality and energy storage. Nonetheless, anode corrosions derived from H₂O molecules and high risks of volatilization and leakage hinder the advancement of Zn-CO₂ batteries. In this work, polyvinyl alcohol (PVA)-based hydrogel electrolyte with fast ion diffusion kinetics, high mechanical strength, and flexibility is developed to replace liquid electrolyte. Since hydroxyl radicals in the polymer chain can interact with H₂O and Zn²⁺, electrode corrosion from free H₂O and active H₂O around Zn²⁺ is significantly inhibited, facilitating the uniform deposition of Zn²⁺ cations. The introduction of an ionic liquid plasticizer further enhances the interaction between Zn²⁺ and polymer backbone, as well as amorphous extent of the electrolyte. The hydrogel electrolyte possesses adequate self-healing ability, whose ionic conductivity reaches 7.95 × 10^-3 S cm^-1. The symmetric Zn metal batteries containing the electrolyte remain steady for >2000 h under different current densities. Furthermore, the Zn-CO₂ battery based on Ru nanoparticles cathode and hydrogel electrolyte realizes a discharge capacity of 6028 mAh g^-1 and stable cyclicity for 90 times. The reaction path of hydrogel electrolyte-based Zn-CO₂ battery is that CO₂ is reduced to ZnCO₃ and C species followed by reversible decomposition of discharge products on recharge.