The Regulation of Local Li⁺ Coordination Environment for High-Performance Quasi-Solid-State Polymer Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Quasi-solid-state polymer electrolytes (QSPEs) offer flexibility and good electrode contact but suffer from low room temperature ionic conductivity.
• Enhancing ionic conductivity is crucial for QSPEs, with polymer structure and plasticizers being key factors.
• Existing research often neglects how plasticizer/polymer interactions influence Li+ coordination and ion transport heterogeneity.

Purpose of the Study:

• To investigate how different plasticizers (FEC and EC) affect Li+ coordination environments within hyperbranched polymer electrolytes.
• To elucidate the mechanism behind enhanced Li+ transport in QSPEs modulated by plasticizer choice.
• To optimize QSPEs for improved ionic conductivity and electrochemical performance.

Main Methods:

• Designed a hyperbranched polymer structure for QSPEs.
• Incorporated fluoroethylene carbonate (FEC) and ethylene carbonate (EC) as plasticizers.
• Analyzed Li+ coordination environments and ion transport mechanisms.
• Fabricated and tested Li||LiFePO4 batteries using the developed QSPEs.

Main Results:

• Fluoroethylene carbonate (FEC) exhibits weaker Li+ solvation than ethylene carbonate (EC), promoting polymer-matrix coordination with Li+.
• This weaker solvation facilitates accelerated Li+ transmission pathways within the QSPE.
• The QSPE with FEC demonstrated a superior ionic conductivity of 8.8 × 10-4 S cm-1 at room temperature.
• The Li||LiFePO4 battery with FEC-QSPE showed excellent capacity retention (83.79% after 2000 cycles).

Conclusions:

• The choice of plasticizer significantly impacts Li+ coordination and transport in QSPEs.
• FEC is a more effective plasticizer than EC for enhancing ionic conductivity and electrochemical stability in QSPEs.
• This work provides a new strategy for designing high-performance QSPEs by controlling Li+ coordination environments.