Air-Stable Binary Hydrated Eutectic Electrolytes with Unique Solvation Structure for Rechargeable Aluminum-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aluminum-ion batteries (AIBs) offer a promising alternative to lithium-ion batteries for large-scale energy storage due to aluminum's abundance, low cost, and safety.
• Current AIB development is hindered by expensive, corrosive, and humidity-sensitive AlCl3-based ionic liquid electrolytes.

Purpose of the Study:

• To develop a low-cost, non-corrosive, and air-stable hydrated eutectic electrolyte for AIBs.
• To optimize the electrolyte's solvation structure for stable and reversible aluminum deposition and stripping.
• To demonstrate the performance of AIBs utilizing the novel electrolyte and a vanadium oxide nanorod cathode.

Main Methods:

• A hydrated eutectic electrolyte was synthesized using aluminum perchlorate nonahydrate and methylurea (MU).
• The molar ratio of components was optimized to achieve a specific solvation structure (average coordination number of 2.4).
• In situ synchrotron radiation X-ray diffraction was used to study Al3+ insertion/extraction mechanisms.

Main Results:

• The optimized aluminum perchlorate nonahydrate/MU hydrated deep eutectic electrolyte (AMHEE) facilitated stable and reversible aluminum deposition/stripping.
• An AIB utilizing AMHEE and a vanadium oxide nanorod cathode achieved a high discharge capacity of 320 mAh g-1 with good capacity retention.
• The AMHEE exhibited low desolvation energy, enabling efficient Al3+ ion transport.

Conclusions:

• The developed AMHEE presents a low-cost, safe, and environmentally friendly electrolyte solution for sustainable AIBs.
• This work paves the way for practical and high-performance aluminum-ion battery applications.
• The optimized solvation structure is key to achieving efficient electrochemical performance in AIBs.