A Deep Eutectic Electrolyte Mimicking a Localized High-Concentration Environment Enables Reversible Aluminum...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aluminum metal batteries (AMBs) offer high theoretical capacity and safety but are limited by inefficient electrolytes for reversible aluminum plating/stripping.
• Developing stable and efficient electrolytes is crucial for advancing AMB technology.

Purpose of the Study:

• To design and develop a novel, economical, and low-corrosive deep eutectic electrolyte (DEE) for AMBs.
• To enhance the performance of aluminum electrodeposition and cycling stability.

Main Methods:

• A cost-effective AlCl3/tetramethylurea (TMU) deep eutectic electrolyte (DEE) was synthesized.
• A non-solvating co-solvent, 1,2-difluorobenzene (1,2-dFBn), was introduced to modify electrolyte properties.
• Electrochemical performance, including plating/stripping, cycling stability, and Coulombic efficiency, was evaluated.

Main Results:

• The AlCl3/TMU DEE demonstrated reversible Al electrodeposition with preferential (111) orientation.
• The addition of 1,2-dFBn reduced electrolyte viscosity and improved ionic conductivity.
• The optimized electrolyte enabled stable Al cycling for over 1,600 hours with ultralow polarization and promoted uniform Al deposition.
• Al||graphite cells achieved high capacity retention and nearly 100% Coulombic efficiency over 600 cycles.

Conclusions:

• The developed localized-high-concentration-electrolyte-like (LHCE-like) DEE offers a promising solution for stable and efficient AMBs.
• The rational design of electrolytes by incorporating specific co-solvents is key to overcoming challenges in aluminum battery technology.