Eutectic-electrolyte-enabled zinc metal batteries towards wide temperature and voltage windows

Abstract

Zinc metal batteries (ZMBs) are highly promising devices for large-scale energy storage applications. However, the commonly used aqueous electrolyte often leads to issues such as hydrogen evolution, narrow temperature range, and dendrite growth, significantly limiting electrochemical and thermal windows of ZMBs. Here, we report a nonflammable deep eutectic electrolyte (DEE), achieving wide electrochemical (3.0 V vs. Zn/Zn²⁺) and thermal-stability (−70 °C to 160 °C) windows. Benefiting from these characteristics, DEE contributes to promoting the small and compact Zn nucleation, eliminating hydrogen evolution, and generating a robust organic–inorganic-coupled solid–electrolyte interphase, reaching sustained Zn plating/stripping performance in Zn–Zn symmetric cells and Zn–V₂O₅ cells. More importantly, DEE enables ZMBs to be cycled in a wide temperature range of −20 °C to 80 °C, exceeding most aqueous electrolytes in high-temperature range. Furthermore, we demonstrate the potential of DEE for high-voltage cells with Zn-ion capacitors cycled up to 2.5 V. Our findings provide insightful understandings of the Zn plating/stripping chemistry in organic coordination environments and a practical stable electrolyte with wide temperature and electrochemical windows.