Hybrid Dynamic Covalent Network-Based Protecting Layer for Stable Li-Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Metallic lithium (Li) is a promising anode material for high-capacity energy storage.
• Challenges include lithium dendrite growth and unstable solid electrolyte interphase (SEI) layers.
• Developing protective layers is crucial for commercializing Li metal batteries.

Purpose of the Study:

• To develop a hybrid covalent adaptable polymer network (HCAPN) as a protective layer for metallic lithium anodes.
• To investigate the HCAPN's properties, including mechanical strength, solvent resistance, and self-healing capabilities.
• To evaluate the electrochemical performance of Li metal batteries utilizing the HCAPN protective layer.

Main Methods:

• Synthesized HCAPN via copolymerization and cross-linking with polyethylenimine (PEI) and amine-modified silicon dioxide (SiO2).
• Formed dynamic covalent bonds (vinylogous urethane) between polymer components.
• Assembled symmetric and full battery cells (HCAPN@Li||HCAPN@Li, HCAPN@Li||LiFePO4, HCAPN@Li||NCM811) for electrochemical testing.

Main Results:

• HCAPN exhibits enhanced mechanical properties, solvent resistance, and healability/recyclability.
• Symmetric cells (HCAPN@Li||HCAPN@Li) demonstrated a cycle life of 800 hours with low overpotential.
• Full cells showed excellent performance: 77% capacity retention over 400 cycles (LiFePO4) and 79% after 300 cycles (NCM811).

Conclusions:

• The HCAPN serves as an effective protective layer, inhibiting lithium dendrite growth.
• The hybrid dynamic covalent network offers a new strategy for stabilizing Li metal anodes.
• This approach significantly improves the electrochemical performance and cycle life of lithium-ion batteries.