All-temperature zinc batteries with high-entropy aqueous electrolyte

Abstract

Electrification of transportation and rising demand for grid energy storage continue to build momentum around batteries across the globe. However, the supply chain of Li-ion batteries is exposed to the increasing challenges of resourcing essential and scarce materials. Therefore, incentives to develop more sustainable battery chemistries are growing. Here we show an aqueous ZnCl2 electrolyte with introduced LiCl as supporting salt. Once the electrolyte is optimized to Li2ZnCl4⋅9H2O, the assembled Zn–air battery can sustain stable cycling over the course of 800 hours at a current density of 0.4 mA cm−2 between −60 °C and +80 °C, with 100% Coulombic efficiency for Zn stripping/plating. Even at −60 °C, >80% of room-temperature power density can be retained. Advanced characterization and theoretical calculations reveal a high-entropy solvation structure that is responsible for the excellent performance. The strong acidity allows ZnCl2 to accept donated Cl− ions to form ZnCl42− anions, while water molecules remain within the free solvent network at low salt concentration or coordinate with Li ions. Our work suggests an effective strategy for the rational design of electrolytes that could enable next-generation Zn batteries. Zinc batteries are receiving growing attention due to their sustainability merits not shared by lithium-ion technologies. Here the aqueous electrolyte design features unique solvation structures that render Zn–air pouch cell excellent cycling stability in a wide temperature range from −60 to 80 °C.