Enabling low-temperature aqueous zinc/copper-sulfur hybrid batteries through electrolyte design

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable aqueous batteries are crucial for grid-scale energy storage but face challenges with low specific energy and poor performance at low temperatures.
• Current low-temperature aqueous batteries often employ ion-insertion positive electrodes with limited capacity, hindering overall energy density.
• Aqueous sulfur-based batteries offer high theoretical capacity, but their low-temperature operation is difficult to achieve without compromising room-temperature performance.

Purpose of the Study:

• To develop a high-performance, low-temperature rechargeable aqueous battery.
• To address the limitations of existing aqueous batteries in cold environments.
• To enhance the specific energy and operational stability of sulfur-based batteries at sub-zero temperatures.

Main Methods:

• Development of a novel electrolyte based on copper tetrafluoroborate (Cu(BF₄)₂) with a low glass transition temperature (-115.1°C) and high ionic conductivity (5.16 mS cm^-1 at -60°C).
• Fabrication and testing of a zinc-sulfur (Zn-S) battery system utilizing the new electrolyte.
• Performance evaluation of the Zn-S battery at low temperatures, including discharge capacity and specific energy measurements.

Main Results:

• The Cu(BF₄)₂-based electrolyte demonstrated excellent low-temperature properties, enabling faster reaction kinetics compared to traditional CuSO₄-based electrolytes.
• The developed zinc-sulfur battery achieved a high discharge capacity of 348 mA h g_(S+Zn)^-1 at -50°C.
• The battery exhibited a specific energy of 339 W h kg_(S+Zn)^-1 at -50°C, demonstrating competitive performance with existing aqueous battery technologies.

Conclusions:

• The novel Cu(BF₄)₂-based electrolyte is highly effective for low-temperature aqueous batteries.
• The developed zinc-sulfur battery offers a promising solution for large-scale energy storage in cold climates.
• This research overcomes key limitations in aqueous sulfur battery technology, paving the way for wider adoption in demanding environments.