Realizing wide-temperature Zn metal anodes through concurrent interface stability regulation and solvation structure modulation

Abstract

Stable cycling of Zn metal anodes under thermal extremes remains a grand challenge with the corresponding failure mechanisms largely unexplored. Here, we unravel the origin of thermal instability during Zn plating/stripping. The low temperature renders deteriorative dendrites growth, while a high temperature causes aggravating parasitic reactions. Zn metal/electrolyte interface and electrolyte solvation chemistry are then regulated via the introduction of oligomer poly(ethylene glycol) dimethyl ether as a competitive-solvent into the aqueous electrolyte to circumvent these issues. Complementary experimental and theoretical studies demonstrate that the competitive-solvent shifts water-occupied interface into oligomer one through preferential Zn surface adsorption, enabling dendrite-free Zn morphologies. Furthermore, such solvent alters the electrolyte interaction by re-constructing oligomer/water hydrogen bonds and participating in the solvation sheath of Zn ions, which highly alleviates parasitic reactions. Consequently, Zn metal anodes deliver more than 1600 h Zn cyclic lifetime at all the tested temperatures of 0, 25 and 50 °C, over 10-fold enhancement than in pristine electrolytes. Application-wise, competitive-solvent suppresses the fast cathode dissolution because of highly reduced water activities and realizes the stable Zn/V2O5 full cells over a wide temperature range from -15 to 65 °C.