Polymer-Modulated Solvation Chemistry via Compatibilizing-Solvent Plasticization for Stable High-Energy Lithium Metal...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Poly(vinylidene fluoride) (PVDF)-based polymer electrolytes are crucial for high-energy, high-safety lithium metal batteries.
• Current limitations include unstable plasticizers (e.g., N,N-dimethylformamide) that compromise lithium reversibility and high-voltage stability.
• Thermodynamic immiscibility between polymers and favorable plasticizers hinders homogeneous electrolyte formation.

Purpose of the Study:

• To develop a strategy for homogeneous plasticization of PVDF-based polymer electrolytes using immiscible but electrochemically stable plasticizers.
• To overcome the thermodynamic limitations preventing uniform mixing of polymers and selected plasticizers.
• To enhance the performance and safety of lithium metal batteries through improved polymer electrolytes.

Main Methods:

• Utilized a descriptor-informed screening to identify electrochemically favorable plasticizers.
• Implemented a compatibilizing-solvent-enabled plasticization strategy using a transient solvent.
• Lowered the effective Flory-Huggins interaction parameter to achieve homogeneous plasticization of poly(vinylidene fluoride-co-hexafluoropropylene) with immiscible plasticizers like sulfolane.
• Investigated polymer-sulfolane interactions and their effect on the solid-electrolyte interphase.

Main Results:

• Achieved homogeneous plasticization of PVDF-based polymer electrolytes with immiscible plasticizers, exemplified by sulfolane.
• Demonstrated suppressed sulfolane migration and modulated anion-aggregate solvation structures, leading to fluorine-rich solid-electrolyte interphases.
• Attained an average lithium plating/stripping Coulombic efficiency of 99.1% over 1400 cycles.
• Supported stable cycling of 4.7 V Ni-rich cathodes at 20C (7.1 mA cm⁻²).
• Reached an energy density of 451.5 Wh kg⁻¹ in Ah-scale pouch cells.

Conclusions:

• The compatibilizing-solvent strategy provides a general route for expanding plasticizer design in PVDF-based polymer electrolytes.
• This approach significantly enhances lithium metal battery performance, including cycling stability and energy density.
• Offers a promising direction for the practical realization of high-energy and high-safety lithium metal batteries.