Rechargeable Calcium-Sulfur Batteries Enabled by an Efficient Borate-Based Electrolyte.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Rechargeable metal-sulfur batteries offer high energy density and low cost.
• Multivalent-metal anodes, like calcium, are promising due to their potential for dendrite-free deposition.
• Calcium-sulfur (Ca-S) battery development is hindered by the lack of suitable electrolytes for reversible calcium and sulfur reactions.

Purpose of the Study:

• To investigate a room-temperature calcium-sulfur battery system.
• To develop and evaluate a stable and efficient electrolyte for Ca-S batteries.
• To understand the electrochemical behavior and redox chemistry of Ca-S systems.

Main Methods:

• Electrochemical studies of a room-temperature Ca-S battery.
• Utilizing a calcium tetrakis(hexafluoroisopropyloxy) borate (Ca[B(hfip)4]2) electrolyte.
• Mechanistic investigations into sulfur redox reactions and calcium deposition.

Main Results:

• The Ca-S batteries achieved a cell voltage of approximately 2.1 V.
• Demonstrated good reversibility in the electrochemical cycling.
• Identified polysulfide/sulfide species involved in the sulfur redox chemistry within the calcium-based system.

Conclusions:

• A stable and efficient Ca[B(hfip)4]2 electrolyte enables functional room-temperature Ca-S batteries.
• The developed Ca-S battery exhibits promising performance characteristics for energy storage.
• Further research into the redox mechanisms can optimize Ca-S battery technology.