High-Entropy Non-Flammable Ionic Liquid/Dimethoxymethane Composite Electrolyte for High-Performance Lithium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-energy-density and safe lithium-ion batteries are crucial for next-generation energy storage.
• Current electrolytes face challenges with safety, stability, and performance at high voltages.
• Advancements in electrolyte composition are needed to overcome these limitations.

Purpose of the Study:

• To develop and characterize a novel high-entropy ionic liquid/ether composite electrolyte.
• To investigate the unique coordination structure and its impact on ion transport and interphase formation.
• To evaluate the electrolyte's performance in high-voltage lithium-ion batteries with advanced electrode materials.

Main Methods:

• Synthesis of a composite electrolyte comprising N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMP-TFSI) ionic liquid, dimethoxymethane (DME), lithium difluoro(oxalato)borate (LiDFOB), fluoroethylene carbonate (FEC), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE).
• Analysis of the electrolyte's coordination structure and its effect on Li+ desolvation kinetics and solid-electrolyte interphase (SEI) chemistry.
• Electrochemical testing of full cells using graphite and SiOₓ anodes, and a LiNi₀.₈Co₀.₁Mn₀.₁O₂ cathode at 4.5V.
• Operando X-ray diffraction (XRD) to study ion intercalation behavior.

Main Results:

• The proposed electrolyte exhibits low flammability, high thermal stability, and negligible corrosivity towards aluminum current collectors.
• It operates stably at potentials up to 5V and demonstrates excellent compatibility with graphite, SiOₓ anodes, and LiNi₀.₈Co₀.₁Mn₀.₁O₂ cathodes.
• Operando XRD confirmed the suppression of DME and PMP⁺ co-intercalation into graphite, a common issue.
• A 4.5V LiNi₀.₈Co₀.₁Mn₀.₁O₂//graphite full cell showed superior specific capacity, rate capability, and cycling stability.

Conclusions:

• The high-entropy ionic liquid/ether composite electrolyte offers a promising solution for high-voltage, high-safety lithium-ion batteries.
• The unique coordination environment within the electrolyte contributes to improved interfacial stability and ion transport.
• This electrolyte demonstrates significant potential for practical applications in advanced energy storage systems.