In Situ Polymerized Flame Retardant Gel Electrolyte for High-Performance and Safety-Enhanced Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Lithium metal batteries (LMBs) face safety challenges due to flammable electrolytes and interfacial issues.
• Developing stable and safe electrolytes is crucial for advancing high-energy-density batteries.

Purpose of the Study:

• To introduce a novel flame retardant gel electrolyte (FRGE) for improved LMB safety and performance.
• To investigate the interfacial compatibility and dendrite suppression capabilities of the new FRGE.

Main Methods:

• Synthesized FRGE using in situ polymerization of polyethylene glycol dimethacrylate (PEGDMA) and pentaerythritol tetraacrylate (PETEA) with a novel flame-retardant solvent, triethyl 2-fluoro-2-phosphonoacetate (TFPA).
• Evaluated interfacial compatibility with Li metal anodes and Li dendrite growth inhibition in Li||Li symmetric cells.
• Measured ionic conductivity and Li+ transference number of the FRGE.
• Tested the electrochemical performance of a LiFePO4|FRGE|Li cell.

Main Results:

• The FRGE demonstrated excellent interfacial compatibility with Li metal anodes, effectively inhibiting Li dendrite growth.
• Achieved stable cycling over 500 hours in Li||Li symmetric cells at 1 mA cm-2 and 1 mAh cm-2.
• FRGE exhibited high ionic conductivity (3.15 mS cm-1) and a Li+ transference number of 0.47.
• The LiFePO4|FRGE|Li cell showed remarkable long-term cycling stability with 94.6% capacity retention after 700 cycles.

Conclusions:

• The developed FRGE offers a promising solution for enhancing the safety and electrochemical performance of Li metal batteries.
• The polymer skeleton effectively restricts free phosphate molecules, leading to stable interfaces and suppressed dendrite formation.
• This research presents a new strategy for developing high-safety, high-energy-density LMBs.