Concentrated Ionic-Liquid-Based Electrolytes for High-Voltage Lithium Batteries with Improved Performance at Room...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Conventional organic electrolytes in batteries pose safety risks.
• High viscosity of ionic liquids (ILs) limits their electrochemical performance at room temperature.
• Developing safer, high-performance electrolytes is crucial for advanced energy storage.

Purpose of the Study:

• To synthesize and evaluate novel ionic liquids with enhanced fluidity for battery applications.
• To investigate the electrochemical performance of IL-based electrolytes in Li/Li_1.2 Ni_0.2 Mn_0.6 O₂ cells.
• To explore strategies for improving the rate capability of IL-based electrolytes at room temperature.

Main Methods:

• Synthesis of alkoxy-functionalized cations and asymmetric imide anions for ILs.
• Fabrication and electrochemical testing of Li/Li_1.2 Ni_0.2 Mn_0.6 O₂ cells using novel IL electrolytes.
• Analysis of cycling stability, capacity retention, and coulombic efficiency.
• Investigation of Li-concentrated IL electrolytes to assess rate performance.

Main Results:

• The Li/Li_1.2 Ni_0.2 Mn_0.6 O₂ cell with DEMEFTFSI electrolyte showed an initial capacity of 153 mAh g^-1 (2.5-4.6 V).
• Achieved 65.5% capacity retention over 500 cycles with >99.5% coulombic efficiency.
• Li-concentrated IL electrolytes improved room-temperature rate capability, attributed to Li⁺ aggregate species formation.

Conclusions:

• Alkoxy-functionalized cations and asymmetric imide anions effectively reduce IL viscosity and enhance fluidity.
• Novel IL electrolytes offer improved safety and electrochemical stability for lithium-ion batteries.
• Li-concentrated IL electrolytes present a promising pathway to overcome rate limitations at room temperature.