(Invited) ZnCl2-Based Water-in-Salt Electrolytes in Zn Batteries

Abstract

A storage battery should be safe, ideally has the energy density and cycle life of Li-ion batteries, and can be manufactured at a similar cost as Lead-Acid batteries. The excellent performance and the low cost will result in a low levelized energy cost (LEC). The commercialization of such a battery technology will be disruptive to the entire energy industry. Such batteries will increase the adoption of renewables, microgrids, and home power, and enable a more reliable and resilient grid. A new electrolyte system is a pivot to transform the conventional primary Zn batteries into highly reversible secondary batteries. Our recent results demonstrate that ZnCl2 based aqueous electrolytes render plating and stripping of Zn metal anode highly reversible. Zn metal anode in such electrolytes exhibits a Coulombic efficiency of 99.8% at 1 mA cm-2, and does not grow any irregular morphology, including dendrites. Our new electrolytes take on the hydrogen evolution reaction—the showstopper—in Zn metal batteries by strengthening the O-H covalent bonds of water. Such a Zn anode delivers a long cycle life of 1500 cycles by coupling with a commercially available cathode. We have also explored the new electrolytes to address the cathode dissolution problem of Zn metal batteries by leveraging on the reversible anion storage that delivers very stable cycling performance. The research on such new electrolytes broadens the horizon of the electrochemical energy storage.