"Rigid Exterior, Soft Interior" Design Enables High-Voltage Polyether Electrolytes for Quasi-Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Polyether electrolytes are crucial for lithium metal batteries but suffer from instability at high voltages.
• Instability of the electrolyte and interphases limits the application of polyether electrolytes in high-voltage lithium metal batteries.

Purpose of the Study:

• To develop a novel high-voltage polyether electrolyte with enhanced stability and performance for lithium metal batteries.
• To investigate the effect of a "rigid exterior, soft interior" design on electrolyte properties and battery performance.

Main Methods:

• Fabrication of a polyether electrolyte featuring a 3D fluorine-contained network (rigid exterior) and a unique solvation structure with intensified Li+-anion coordination (soft interior).
• Characterization of the electrolyte's ionic conductivity, Li+ transference number, and electrochemical stability window.
• Evaluation of the electrolyte's interfacial properties and performance in Li||Li, Li||NCM811, and Li||NCM523 quasi-solid-state batteries (QSSBs).

Main Results:

• The novel electrolyte exhibits an ionic conductivity of 1.13 mS cm-1 at 25 °C, a Li+ transference number of 0.85, and an electrochemical stability window exceeding 5 V.
• The electrolyte forms salt-philic, solvent-phobic interfacial films, enhancing electrolyte/electrode interphase stability.
• Exceptional cyclability over 4000 h in Li||Li cells and superior performance in 4.6 V Li||NCM811 QSSBs were demonstrated.
• A 4.3 V Li||NCM523 QSSB achieved ~100% Coulombic efficiency and 95.4% capacity retention after 600 cycles at 3C.
• A 4.5 V Li||NCM811 QSSB showed over 96.3% capacity retention after 400 cycles at 1C.

Conclusions:

• The
• rigid exterior, soft interior
• design successfully enhances the stability and electrochemical performance of polyether electrolytes for high-voltage applications.
• The developed electrolyte shows great promise for next-generation quasi-solid-state lithium metal batteries.
• The electrolyte's ability to form stable interphases is key to achieving long cycle life and high capacity retention.