Researchers from the Shanghai Institute of Ceramics of the Chinese Academy of Sciences have proposed a new "water-in-ionogel" aqueous polymer electrolyte. The electrolyte has high operating cell voltage, high water content and low salt concentration for operation at low temperatures.

lithium battery

Electric vehicles and flexible electronics are in a new era of thriving, and there is an urgent need for a safe, high-energy and sustainable battery that can withstand bumps and bends, even immersion in water, and work in sub-zero environments while maintaining electrochemical performance.

Among various energy storage technologies, aqueous rechargeable Na-ion batteries with nonflammable aqueous electrolytes have inherent advantages such as safety, non-toxicity, and low cost, which have led to great interest in energy storage systems.

Due to its salting-out at low temperature, high freezing point, and slow charge transport kinetics at the electrolyte-electrode interfacial layer, traditional "water-in-salt" electrolytes have high concentrations of fluoride salts and molecularly crowded aqueous electrolytes, which Confinement in a crowded polyethylene glycol (PEG) network with poor low temperature performance.

In this study, water in copolymerized PEG-derivatized poly(ethylene glycol) methyl ether methacrylate (PEGMA) and bisphenol A ethoxylated dimethacrylate (BEMA) formed cross-linked gels , thereby generating an antifreeze solid electrolyte by changing hydrogen bonds.

In addition, a typical electrolyte additive, fluoroethylene carbonate, was introduced into the PEGMA-BEMA system to form OH...F bonds, weaken the H-bond network in aqueous solution, thereby lowering the freezing point, and build a solid-electrolyte interface for low temperature ion diffusion.

A polymer-aqueous sodium-ion full battery consisting of a manganese-based cathode and a hard carbon anode can deliver high energy density, the researchers said.

What's more, this eco-friendly water-based polymer battery can be freely sealed, making it an ultra-thin, lightweight battery that performs well under harsh conditions such as bending, cutting, immersion in water, or fire.

This is the first attempt to achieve high-pressure aqueous electrolytes that can operate at low temperatures. In the future, researchers will work to improve the voltage window and transport properties of water in ionogel electrolytes for low-cost, sustainable energy storage, even at sub-zero temperatures or in water.