Aqueous Casting of Polymeric Electrolyte Membranes for Solid Rechargeable Na Batteries

Organic solid electrolytes for rechargeable batteries are usually produced by dissolving or suspending all components and casting. For decades, acetonitrile has been widely used despite its rapid reaction with alkali metals, forming toxic products such as cyanide. Using large amounts of acetonitrile for industrial applications may pose health and environmental concerns. In addition, researchers claim that even if the solid electrolyte membranes contain residual trace water, this may positively affect the transport properties of Na ions in PEO, and those batteries with electrolytes containing trace water showed significantly improved electrochemical performance. Here, an aqueous medium was considered for casting solid polymer electrolyte membranes. Na ions conducting membranes produced with water were characterized and compared to traditional ones, produced with organic solvents. Spectral studies and electrochemical measurements of symmetric cells with Na metal electrodes under static and dynamic conditions and all-solid-state Na batteries showed that the membranes cast from aqueous media are similar to their counterparts, cast from organic volatile solvents. Surprisingly, the water-cast membranes exhibit better performance as solid electrolytes than similar membranes prepared with organic solvents.