High Lithium Salt Content PVDF-Based Solid-State Composite Polymer Electrolyte Enhanced by h-BN Nanosheets

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Solid composite polymer electrolytes (SCPEs) are crucial for high-energy-density lithium metal batteries due to safety advantages.
• However, their overall performance, including ion transport and dendrite inhibition, requires significant improvement for practical applications.

Purpose of the Study:

• To develop an enhanced SCPE based on poly(vinylidene fluoride) (PVDF) with high lithium salt content, incorporating hexagonal boron nitride (h-BN) nanosheets.
• To investigate the electrochemical performance, ion transport properties, and lithium dendrite suppression capabilities of the modified SCPE.

Main Methods:

• Fabrication of a high lithium salt content PVDF-based SCPE incorporating h-BN nanosheets.
• Electrochemical characterization including ionic conductivity, Li+ ion transfer number, and electrochemical stability window measurements.
• Mechanical strength testing and density functional theory (DFT) calculations to understand ion transport mechanisms.
• Assembly and testing of symmetric Li/Li and asymmetric Li/LiFePO4 batteries using the developed SCPE.

Main Results:

• The optimized SCPE (PVDF-L70-B5) exhibited excellent ionic conductivity (2.98×10⁻⁴ S cm⁻¹), a high Li+ ion transfer number (0.62), and a wide electrochemical stability window (5.24 V).
• The material demonstrated strong mechanical strength (3.45 MPa) and effectively inhibited lithium dendrite growth.
• DFT calculations confirmed that h-BN promotes LiTFSI dissociation and Li+ ion transfer.
• Assembled batteries showed high reversible capacity, long-term cycle stability, and good rate performance at various temperatures.

Conclusions:

• The developed h-BN-enhanced SCPE offers superior electrochemical performance and mechanical properties for solid-state lithium batteries.
• This material effectively suppresses lithium dendrite formation, enhancing battery safety and longevity.
• The study presents a promising new pathway for fabricating high-energy-density and safe solid-state lithium batteries.