Ultra-robust Single-Ion Conducting Composite Electrolytes for Stable Li-Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Single-ion conducting polymer electrolytes (SIPEs) offer high lithium-ion (Li+) transport efficiency but suffer from low ionic conductivity.
• Plasticizers improve SIPE ionic conductivity but compromise mechanical strength, hindering their use as solid electrolytes.

Purpose of the Study:

• To overcome the trade-off between ionic conductivity and mechanical robustness in SIPEs.
• To design and fabricate advanced composite membranes for high-performance solid-state batteries.

Main Methods:

• Cross-linking linear SIPEs with a glass-mesh substrate to create a composite membrane (c-SIPM60).
• Incorporating additional lithium salts into a similar composite membrane (c-HTPM60) to enhance ionic conductivity.
• Evaluating electrochemical performance, including ionic conductivity, Li+ transport number, mechanical strength, and cycling stability of LiFePO4//c-SIPM60/Li and LiFePO4//c-HTPM60/Li cells.

Main Results:

• The c-SIPM60 membrane exhibited a Li+ transport number close to 1, tensile strength of 22 MPa, and ionic conductivity of 1.2 × 10-4 S/cm at 25 °C.
• Li/c-SIPM60/Li symmetric cells showed stable cycling for 1200 h; LiFePO4/c-SIPM60/Li cells demonstrated good reversibility.
• The c-HTPM60 membrane maintained high Li+ transport efficiency while increasing ionic conductivity, enabling LiFePO4/c-HTPM60/Li cells to retain >75.6% capacity after 700 cycles at 25 °C.

Conclusions:

• A novel composite membrane design successfully balances high Li+ transport, ionic conductivity, and mechanical robustness.
• These advanced solid electrolytes offer effective Li+ transport for next-generation energy storage systems.
• The findings provide valuable insights for developing high-performance solid electrolytes.