Solvent control of water O-H bonds for highly reversible zinc ion batteries

Aqueous Zn-ion batteries have attracted increasing research interest; however, the development of these batteries has been hindered by several challenges, including dendrite growth, Zn corrosion, cathode material degradation, limited temperature adaptability and electrochemical stability window, which are associated with water activity and the solvation structure of electrolytes. Here we report that water activity is suppressed by increasing the electron density of the water protons through interactions with highly polar dimethylacetamide and trimethyl phosphate molecules. Meanwhile, the Zn corrosion in the hybrid electrolyte is mitigated, and the electrochemical stability window and the operating temperature of the electrolyte are extended. The dimethylacetamide alters the surface energy of Zn, guiding the (002) plane dominated deposition of Zn. Molecular dynamics simulation evidences Zn2+ ions are solvated with fewer water molecules, resulting in lower lattice strain in the NaV3O8 center dot 1.5H(2)O cathode during the insertion of hydrated Zn2+ ions, boosting the lifespan of Zn|| NaV3O8 center dot 1.5H(2)O cell to 3000 cycles. The electrochemical performance of aqueous zinc ion batteries is limited by water activity. Here, the authors propose a hybrid electrolyte that incorporate strongly polar molecules to strengthen the water O-H bonds, thus reduce water activity and improve the electrochemical performance of the batteries.