Highly Efficient Non-Nucleophilic Mg(CF₃SO₃)₂-Based Electrolyte for High-Power Mg/S Battery

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• High-energy magnesium-sulfur (Mg/S) batteries are hindered by the lack of affordable, non-nucleophilic electrolytes.
• Existing electrolytes often suffer from poor stability and limited Mg deposition/dissolution efficiency.

Purpose of the Study:

• To develop a low-cost, non-nucleophilic electrolyte for advanced Mg/S battery applications.
• To investigate the electrochemical properties and performance of the novel electrolyte in Mg/S batteries.

Main Methods:

• A non-nucleophilic electrolyte was synthesized by dissolving magnesium triflate (Mg(CF3SO3)2), magnesium chloride (MgCl2), and aluminum chloride (AlCl3) in 1,2-dimethoxyethane (DME).
• Electrochemical characterization, including cyclic voltammetry and galvanostatic cycling, was performed to evaluate Mg deposition/dissolution and Mg/S redox behavior.
• In-situ analysis was used to study the electrolyte's conditioning process and the transformation of active species.

Main Results:

• The developed electrolyte exhibits efficient reversible Mg deposition/dissolution with a low overpotential (~250 mV) and good oxidative stability up to 3.5 V after conditioning.
• A conditioning process was identified where active [Mg2(μ-Cl)2(DME)4]2+ species transform into [Mg3(μ3-Cl)(μ2-Cl)2(DME)7]3+ due to Al3+ deposition.
• The electrolyte demonstrated excellent compatibility and kinetics for reversible Mg/MgS redox, achieving a high specific capacity (866 mAh g-1 at 200 mA g-1) and power density (550 W kg-1).

Conclusions:

• This work presents a promising low-cost, non-nucleophilic electrolyte, overcoming a key limitation in Mg/S battery development.
• The novel electrolyte facilitates high performance in Mg/S batteries, offering a new direction for exploring high-power energy storage solutions.