Designing multi-tentacle electrolytes to enable fast and deep cycling of aqueous Zn batteries at low temperatures

Abstract

Rechargeable aqueous zinc batteries (AZBs) offer a safe and sustainable solution for large-scale energy storage, but the freezing of electrolytes prevents AZBs from working at low temperatures. Recent research has shown that the freezing point can be effectively lowered by using either concentrated salts or organic-rich electrolytes. However, these strategies result in either low oxidation stability or sluggish mass transport at low temperatures. Here, we report a multi-tentacle electrolyte (MTE) strategy that enables stable, fast and deep cycling of AZBs at −40 °C. The MTE leverages the abundant hydrogen-bonding sites of multi-tentacle salts and organics. Adding small amounts of multi-tentacle moieties not only effectively confines water molecules’ movement and prevents their icing even at −60 °C, but also maintains low viscosity and high ionic conductivity of the electrolyte at low temperatures. At −40 °C, Zn metal anodes could stably cycle for more than 1100 hours at a high current density of 2 mA cm⁻² and a high capacity of 2 mA h cm⁻²; high-capacity AZBs (3.4 mA h cm⁻²) sustain 1000 stable cycling with 99.99% retention per cycle in the MTE. The MTE strategy is also versatile to high-voltage LiMn₂O₄ cathodes, which further enhances the energy density of AZBs to 154.4 W h kg_LMO⁻¹ at −40 °C.