A PVDF/g-C₃N₄-Based Composite Polymer Electrolytes for Sodium-Ion Battery

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Polyvinylidene difluoride (PVDF) and amorphous hexafluoropropylene (HFP) copolymerized polymer solid electrolytes are promising for sodium-based batteries.
• These electrolytes suffer from low room temperature ionic conductivity, limiting their practical application.
• Enhancing ionic conductivity and stability is crucial for developing efficient solid-state sodium-ion and sodium-metal batteries.

Purpose of the Study:

• To improve the properties of PVDF-HFP copolymer electrolytes by incorporating graphitic carbon nitride (g-C3N4) nanosheets.
• To investigate the effect of g-C3N4 as a nanofiller on the structural, electrical, mechanical, and thermal properties of composite solid polymer electrolytes (CSPEs).
• To evaluate the performance of g-C3N4 CSPEs in sodium-metal batteries.

Main Methods:

• Synthesis of g-C3N4 nanosheets and their incorporation into PVDF-HFP copolymer to form CSPEs.
• Structural analysis to determine changes in crystallinity and morphology.
• Electrochemical characterization including ionic conductivity, Na+ transference number, and cyclic voltammetry.
• Mechanical and thermal stability testing.
• Fabrication and testing of sodium-metal batteries using Na3V2(PO4)3 as the cathode.

Main Results:

• g-C3N4 incorporation reduced the crystallinity of the PVDF-HFP matrix and promoted sodium salt dissociation.
• The resulting g-C3N4 CSPEs exhibited enhanced ionic conductivity, Na+ transference number, mechanical properties, and thermal stability.
• A low Na deposition/dissolution overpotential of approximately 100 mV at 1 mA cm-2 after 160 cycles was achieved.
• Sodium-metal batteries utilizing g-C3N4 CSPEs showed reduced polarization (90 mV) and a stable reversible capacity of 93 mAh g-1 after 200 cycles at 1 C.

Conclusions:

• Graphitic carbon nitride nanosheets are effective nanofillers for enhancing the performance of PVDF-HFP based solid polymer electrolytes.
• The modified CSPEs demonstrate superior electrochemical and mechanical properties, suitable for advanced sodium battery applications.
• The use of g-C3N4 CSPEs contributes to improved cycling stability and reduced overpotential in sodium-metal batteries.