Interfacial stability between PVDF-based SPEs and lithium metal anode

The interfacial stability between PVDF-based solid polymer electrolytes (SPEs) and lithium metal anode is an important factor in determining the overall performance and safety of lithium-metal batteries.

PVDF-based SPEs, such as poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), have been widely used as solid electrolytes due to their high ionic conductivity and good mechanical properties. However, the reactivity between the electrolyte and lithium metal can lead to the formation of unwanted side reactions, such as lithium dendrite growth, which can cause short circuits and compromise battery safety.

To improve the interfacial stability, several strategies can be employed:

1. Surface Modification: The surface of the lithium metal anode can be modified to enhance the adhesion and compatibility with the PVDF-based SPE. For example, applying a thin layer of protective coating, such as lithium-ion conductive polymers or ceramic materials, can help prevent direct contact between the lithium metal and electrolyte, reducing the reactivity.

2. Electrolyte Additives: Introducing specific additives into the PVDF-based SPE can improve the interfacial stability. Lithium salts, such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium difluoro(oxalato)borate (LiDFOB), have been used to enhance the compatibility between the electrolyte and lithium metal anode.

3. Interfacial Layer: Forming a stable interfacial layer between the lithium metal and PVDF-based SPE can effectively impede the growth of lithium dendrites. This can be achieved by depositing a layer of solid electrolyte interphase (SEI) on the lithium metal surface, either through pre-treatment or by the deposition of ions from the PVDF-based SPE during initial cycling.

4. Electrode Design: Optimal electrode design can also contribute to improving the interfacial stability. For example, using thin and uniform lithium metal foil as the anode can reduce the formation and growth of lithium dendrites.

It is important to note that the choice of PVDF-based SPE formulation, electrode materials, and battery operating conditions can significantly influence the interfacial stability. Extensive characterization techniques, such as cyclic voltammetry, impedance spectroscopy, and scanning electron microscopy, are typically employed to evaluate the interfacial stability and overall performance of the lithium-metal battery system.