Antifreezing polymeric-acid electrolyte for high-performance aqueous zinc-ion batteries

Zinc (Zn) anodes suffer from hydrogen evolution, surface passivation, and dendrite growth, severely restricting the practical application of aqueous Zn-ion batteries (ZIBs). Here, we report an antifreezing polymeric-acid electrolyte with polyethylene glycol diacid (PEGDA) to realize stable Zn anodes in strongly acidic environment and enable high-performance ZIBs. The polymeric-acid electrolyte provides a strongly acidic environment to eliminate the surface passivation of Zn anodes associated with OH−, changes Zn-ion solvation structure to alleviate H2O-decomposition-induced side reactions, and enables a dendrite-free Zn deposition with an epitaxial growth along the (002)Zn plane. Stable cross-linked polymeric electrode/electrolyte interphases (-ZnOOC-PEG-COOZn-) at bilateral electrodes are formed. Accordingly, the Zn anodes exhibit a high average Coulombic efficiency (CE) of 99.89% over 2500 cycles, even at a high depth of discharge (64%). The Zn//Zn symmetric cells deliver an ultra-long cycling life over 5700 h at 1 mA cm−2 and 1 mA h cm−2. The Zn//ZnxV2O5·nH2O full cells show excellent cycling stability (10,000 cycles) and capacity retention (80.60%) at high current densities. We also demonstrate practical pouch cells showing outstanding electrochemical performance. The electrolyte can enable batteries to work at subzero temperatures (−10 °C) with excellent performance (an average Zn plating/stripping CE of 99.95% for 1200 cycles).