In-Situ Synthesized Gel Polymer Electrolyte Enable High Capacity and Long-Cycle-Life Lithium Metal Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Solid-state lithium-metal batteries (SSLMBs) offer enhanced safety and stability but are limited by low ionic conductivity and narrow electrochemical windows.
• Developing advanced electrolytes is crucial for overcoming these limitations and enabling practical SSLMB applications.

Purpose of the Study:

• To develop novel in-situ polymerized electrolytes (IPEs) for SSLMBs with improved ionic conductivity, lithium transference number, and electrochemical stability.
• To evaluate the electrochemical performance of IPEs in symmetrical lithium cells and solid-state LiFePO4||Li batteries.

Main Methods:

• In-situ polymerization of electrolytes using acrylonitrile (AN) and ethylene glycol dimethacrylate (EGDMA).
• Characterization of ionic conductivity, lithium transference number (tLi+), and electrochemical stable window (ESW) of the IPEs.
• Testing of symmetrical Li||Li cells for lithium stripping/plating stability.
• Assembly and cycling performance evaluation of solid-state LiFePO4||Li batteries using the developed IPEs.

Main Results:

• The IPEs achieved high ionic conductivity (1.77×10⁻³ S/cm at 25°C), an ultrahigh tLi+ of 0.784, and a wide ESW of 5.65 V.
• Symmetrical Li||Li cells demonstrated stable cycling for over 3000 hours.
• LiFePO4||Li batteries exhibited excellent long-cycle performance: over 700 cycles at 2.5C (95% retention) and 1000 cycles at 1C (85% retention).

Conclusions:

• In-situ polymerized electrolytes based on polyacrylonitrile (PAN) significantly enhance SSLMB performance and safety.
• The developed IPEs show great promise for advancing the practical application of high-safety, high-energy-density solid-state batteries.
• In-situ solidification technology offers a viable route for creating advanced electrolytes for next-generation batteries.