Modification of solid electrolyte interface layer between PVDF-based electrolyte and lithium anode

Abstract

Poly(vinylidene fluoride) (PVDF)-based polymer electrolytes (PEs) with good electrochemical performance and processability as well as low-cost advantage, have great potential applications in solid-state lithium (Li) metal batteries (SSLMBs). PVDF-based PEs are generally produced by employing a solution-casting approach with N,N-dimethylformamide (DMF) as the solvent, accompanied by the formation of [DMF-Li+] complex, which facilitates the Li-ion transport. However, the residual DMF can react continuously with lithium (Li) metal, thereby deteriorating the interface layer in the middle of the PVDF-based PEs and Li anodes. Herein, we introduce propylene carbonate (PC) into the PVDF-based PEs to regulate the solvation structure and stabilize the interface layer between the PEs and Li anodes. PC accelerates the dissociation of lithium oxalyldifluoroborate (LiODFB). Consequently, “lithium propylene dicarbonate (LPDC)‒B-O″ oligomer forms as the interfacial layer with high tenacity, homogeneity, and densification, which improves the interfacial contact and suppresses the continuous reaction between the residual DMF and Li anode. We further demonstrate that the PVDF-based PE prepared with DMF-PC mix-solvents shows improved room-temperature ionic conductivity (1.18 × 10−3 S/cm), enhanced stability against electrodes, and superior cycling performance in LiCoO2-based SSLMBs (maintaining 84 % of the initial discharge capacity after 300 cycles).