Overcoming the Obstacle of Polymer-Polymer Resistances in Double Layer Solid Polymer Electrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• High-energy-density lithium batteries require advanced electrolytes.
• Double-layer solid polymer electrolytes (DLSPEs) offer a promising strategy by combining layers stable against lithium metal and high-voltage cathodes.
• Understanding interfacial properties is crucial for optimizing DLSPE performance.

Purpose of the Study:

• To investigate the primary source of electrolyte resistance in DLSPEs.
• To quantify the contribution of the polymer-polymer interface to overall resistance.
• To explore methods for reducing interfacial resistance in DLSPEs.

Main Methods:

• Electrochemical Impedance Spectroscopy (EIS) was employed for in-depth analysis.
• DLSPEs composed of polyether-, polyester-, or polycarbonate-based solid polymer electrolytes were studied.
• Systematic variation of salt concentration (LiTFSI) was performed.

Main Results:

• The polymer-polymer interface was identified as the dominant contributor to electrolyte resistance in DLSPEs.
• Interfacial resistance was found to be approximately 10-fold higher than bulk ionic resistance.
• Increasing LiTFSI salt concentration from 25 to 50 wt % significantly lowered interfacial resistance.

Conclusions:

• The polymer-polymer interface is a critical bottleneck for ionic transport in DLSPEs.
• Enhanced miscibility at the interface, achieved by increasing salt concentration, effectively reduces interfacial resistance.
• Optimizing interfacial properties is key to developing high-performance DLSPEs for advanced lithium batteries.