Universal Anion-Interface-Confinement Strategy to Regulate Robust Solid-Electrolyte Interphase for Lithium Metal...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium metal batteries (LMBs) face performance and safety issues due to lithium metal's reactivity and uneven Li+ deposition/stripping.
• Existing separators often fail to mitigate these challenges, limiting LMB cycle life and stability.

Purpose of the Study:

• To design and fabricate a multifunctional ferroelectric composite separator for improved LMB performance.
• To investigate the mechanism by which the ferroelectric separator regulates the solid-electrolyte interphase (SEI) and ion transport.

Main Methods:

• Fabrication of a composite separator using ferroelectric β-polyvinylidene fluoride (β-PVDF) with directional dipole arrangement.
• Characterization of the separator's properties and the resulting SEI layer on the lithium metal anode.
• Electrochemical testing of Li||Li symmetrical cells and full cells (with LiFePO4 cathode) to evaluate performance and stability.

Main Results:

• The directional dipoles in the β-PVDF separator induced anion interface confinement and promoted complete lithium salt reduction.
• A robust, inorganic-rich SEI layer was formed on the Li metal anode, ensuring uniform Li+ distribution and high interface stability.
• Li||Li symmetrical cells achieved over 4000 h of stable cycling, and a full cell retained 96.84% capacity after 960 cycles.

Conclusions:

• The ferroelectric composite separator effectively enhances the stability and cycle life of lithium metal batteries.
• This strategy offers a novel approach to regulate SEI chemistry using functional coatings and multiphysical fields for anion migration control.