Constructing Efficient Pvdf-Hfp-Based Intercalated Composite Solid Electrolytes Via Competitive Solvation Structures for Rechargeable Lithium Metal Batteries

Abstract

Solid electrolytes (SEs) based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) are considered promising candidates for use in lithium metal batteries (LMBs). However, the development of PVDF-HFP-based solid-state lithium batteries (SSLBs) has been severely hindered by the low ionic conductivity and high electrolyte-electrode interfacial resistance. Herein, we develop a novel PVDF-HFP-based intercalated composite solid-state electrolyte via a competitive model for strong polar solvation. The [Li+-solvent] coordination structure significantly restricted the activity of the primary solvent, dimethyl sulfoxide (DMSO), reducing interfacial resistance and improving interfacial stability. To further optimize the solvation structure, N-methyl-2-pyrrolidone (NMP), a highly polar co-solvent with stronger cationic interactions, is utilized to replace the solvation sites of the primary solvent, resulting in micro-solvation competition and forming a loose Li+ coordination configuration. Additionally, montmorillonite (MMT), characterized by its large initial interlayer spacing and exchangeable interlayer cations, permits the insertion of PVDF-HFP polymer chains. The orderly arrangement of polymer chains between MMT layers creates efficient pathways for Li+, significantly enhancing the ionic conductivity for the intercalated composite solid-state electrolyte. Consequently, the intercalated composite solid-state electrolyte exhibits high ionic conductivity (1.058 mS cm−1). The assembled LFP||Li cell could stably cycle for 1000 cycles at a rate of 1C. This study offers valuable insights into the design of improved PVDF-HFP-based electrolytes for LMBs.

Keywords: Intercalated Composite Solid Electrolytes, PVDF-HFP, Competitive Solvation Structures, Lithium metal batteries