Lignin-based macromolecular composite solid electrolyte enabling high-performance sodium metal batteries via...

Area of Science:

• Materials Science
• Electrochemistry
• Sustainable Chemistry

Background:

• Solid polymer electrolytes (SPEs) are crucial for sodium metal batteries but face challenges with low ionic conductivity and interfacial instability.
• Alkali lignin, a renewable biopolymer, offers a rigid structure and functional groups suitable for developing advanced solid electrolytes.

Purpose of the Study:

• To develop a sustainable and high-performance solid polymer electrolyte for sodium metal batteries using alkali lignin.
• To enhance the ionic conductivity and interfacial stability of SPEs through the incorporation of magnesium fluoride (MgF2).

Main Methods:

• A hybrid polymer matrix was fabricated using alkali lignin and polyvinylidene fluoride (PVDF).
• Low-cost MgF2 was introduced as an inorganic filler to improve ion transport and electrochemical performance.
• The electrochemical properties and cycling stability of the optimized electrolyte (LPM4) were evaluated in a Na3V2(PO4)3//Na full cell.

Main Results:

• The optimized lignin/PVDF/MgF2 electrolyte (LPM4) achieved a room-temperature ionic conductivity of 2.23 × 10^-4 S cm^-1.
• An electrochemical stability window of 4.87 V was observed, indicating good stability.
• The Na3V2(PO4)3//Na full cell demonstrated excellent cycling stability, retaining 88.14% capacity after 100 cycles.
• MgF2 was found to promote ion dissociation and form a stable, fluorine-rich interphase, enhancing interfacial stability.

Conclusions:

• This research successfully valorizes industrial lignin waste into a functional component for biomass-based solid electrolytes.
• The developed lignin-based SPE offers a promising materials strategy for advancing the performance and sustainability of sodium metal batteries.