Solid Polymer Electrolytes with Flexible Framework of SiO₂ Nanofibers for Highly Safe Solid Lithium Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Solid lithium batteries require advanced electrolytes with high ionic conductivity and mechanical stability.
• Composite electrolytes with polymers and 3D fillers offer continuous ion pathways and improved mechanical properties.

Purpose of the Study:

• To develop a novel composite electrolyte for solid lithium batteries using polyethylene oxide-lithium (bis trifluoromethyl) sulfate-succinonitrile (PLS) and 3D SiO2 nanofibers (3D SiO2 NFs).
• To investigate the ionic conductivity, mechanical properties, dendrite suppression, and thermal safety of the developed composite electrolyte.

Main Methods:

• Preparation of a composite electrolyte by combining PLS with 3D SiO2 NFs.
• Characterization of the electrolyte's ionic conductivity, tensile strength, and area specific resistance.
• Assembly and testing of Li/LiFePO4 solid lithium batteries using the composite electrolyte.
• Evaluation of battery performance, including specific capacity, capacity degradation, and thermal safety.

Main Results:

• The composite electrolyte exhibited a total conductivity of 9.32 × 10^-5 S cm^-1 at 30 °C.
• The electrolyte possessed a tensile strength of 7.4 MPa and an area specific resistance of 29.0 Ω cm^2.
• Li/LiFePO4 cells showed an initial specific capacity of 167.9 mAh g^-1 with only 3.28% capacity degradation after 100 cycles.
• The 3D structure suppressed dendrite growth and enhanced electrical field homogenization.
• The cells demonstrated automatic shutdown above 400 °C due to PLS decomposition, ensuring safety.

Conclusions:

• The developed PLS/3D SiO2 NFs composite electrolyte offers high ionic conductivity and excellent mechanical properties for solid lithium batteries.
• The 3D nanostructure effectively suppresses lithium dendrite growth, improving battery cycle life.
• The composite electrolyte exhibits superior thermal safety, with automatic shutdown capabilities at elevated temperatures.
• This composite electrolyte represents a promising advancement for high-performance and safe solid lithium batteries.