Chloride-Reinforced Solid Polymer Electrolyte for High-Performance Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Flexible solid-state polymer electrolytes (SPEs) are crucial for all-solid-state lithium batteries (ASSLBs) due to intimate electrode contact and reduced interfacial impedance.
• However, limitations in ionic conductivity and mechanical strength hinder the widespread adoption of SPEs.
• Developing robust SPEs with high performance is essential for advancing battery technology.

Purpose of the Study:

• To enhance the ionic conductivity and mechanical properties of poly(ethylene oxide) (PEO)-based solid-state polymer electrolytes.
• To investigate the synergistic effects of incorporating Li2ZrCl6 (LZC) into PEO-based SPEs for improved ASSLB performance.
• To explore the potential of chloride-polymer composite electrolytes for next-generation solid-state lithium metal batteries.

Main Methods:

• Incorporation of the chloride superionic conductor Li2ZrCl6 (LZC) into a poly(ethylene oxide) (PEO) polymer electrolyte matrix.
• Characterization of ionic conductivity and Li-ion transference number at elevated temperatures (60 °C).
• Investigation of the interaction between LZC and PEO using FT-IR and Raman spectroscopy.
• Electrochemical testing of Li||Li symmetric cells and LiFePO4||Li ASSLBs to evaluate cycling stability and performance.

Main Results:

• The composite electrolyte achieved a high ionic conductivity of 5.98 × 10^-4 S cm^-1 at 60 °C and a Li-ion transference number of 0.44.
• Spectroscopic analysis confirmed interactions between LZC and PEO, inhibiting PEO decomposition and promoting uniform Li-ion deposition.
• Li||Li cells exhibited low polarization (30 mV) after 1000 hours of cycling.
• LiFePO4||Li ASSLBs with 1% LZC demonstrated excellent cycling performance, retaining 145.4 mA h g^-1 after 400 cycles at 0.5 C.

Conclusions:

• The addition of Li2ZrCl6 significantly enhances the ionic conductivity and mechanical strength of PEO-based SPEs.
• The synergistic combination of chloride and polymer electrolytes offers a promising pathway for developing high-performance ASSLBs.
• This composite electrolyte material shows great potential for future solid-state lithium metal battery applications.