Electric Field Propelled Anion-Type Solvation Structure Reconstruction With Accelerated Kinetics for Low-Temperature Zinc Metal Batteries.

Abstract

Organic-rich eutectic electrolytes, which have been prevalent to address the electrolyte freezing and Zn dendrite growth challenges for low-temperature aqueous zinc-based batteries, suffer from sluggish Zn²⁺ desolvation kinetics and mass transport. Here, we introduce aprotic acetone as a cosolvent to improve the performance of aqueous Zn(BF₄)₂-based electrolyte under cold environments. Leveraging dynamic keto-enol tautomerism in the primary solvation sheath of Zn²⁺ propelled by the electrical double layer electric field, an anion-type solvation structure is established, which shortens the Zn²⁺ desolvation path with accelerated kinetics and constructs a tough and tight interface with a gradient organic-inorganic configuration, eventually enabling uniform Zn deposition at low temperatures. As a result, Zn||Zn symmetric cells sustain for 7500 h at 1 mA·cm^-2 and over 1200 h with 34.2 % DOD at 10 mA·cm^-2 under -40°C. Pouch-cell properties are demonstrated by matching a PEDOT-V₂O₅ cathode, which harvests a high capacity of 150 mAh over 210 cycles under practical conditions (N/P = 4.33 and E/C = 6.0 µL mg^-1) and holds approaching 100 % capacity retention at -40°C. This work provides an effective strategy toward industrializing practical cold-resistant zinc-based batteries via modulating the electrolyte structure.