High-Efficiency Zinc-Metal Anode Enabled by Liquefied Gas Electrolytes

The practical applications of rechargeable zinc metal batteries are prevented by poor Zn reversibility, which induces both inferior Coulombic efficiency (CE) and zinc dendrite growth that worsens at low temperatures because of deteriorated kinetics in both charge and mass transfer. Herein, a liquefied gas electrolyte based on a mixture of fluoromethane and difluoromethane is demonstrated, which displays an excellent conductivity (>3.4 mS cm–1) across a broad temperature range (−60 to +20 °C) and enables highly reversible Zn cycling with no evidence of shorting behavior at both room temperature and −20 °C for over 200 cycles (>400 h) with an average CE of >99.3% and 20% Zn utilization per cycle. Density functional theory calculations showed that such improvements benefited from a ZnF2-enriched interphase formed on the anode because of decomposition of the liquefied gas electrolyte. This electrolyte was verified in a Zn||Na2V6O16·1.63H2O cell with stable performance, where a similar ZnF2-rich interphase was also confirmed.