Rong-Ao Tong,Linhui Chen,Bingbing Fan,Gang Shao,Ruiping Liu,Chang-An Wang
All solid-state lithium metal batteries are viewed as a potential next-generation energy storage technology due to their high energy density and better safety performance. The study on solid-state electrolytes (SSE) is of crucial importance for the development of technology in this field. Here, we develop a solvent-free preparation and matrix modification process for all-solid-state composite electrolytes (CSEs) based on the blended PVDF-HFP/PEO polymer matrix, and systematically study the effects of the solvent-free process on their properties. The results show that the solvent-free PVDF-HFP/PEO/10 wt % LLZTO solid-state electrolytes (1:1 mass ratio blended polymer matrix) combine the electrochemical and mechanical advantages of both polymers, thus-prepared electrolytes perform excellent tensile strength and ductility (over 500% strain for polymer matrix as well as 170% strain and 4.78 MPa strength for CSEs), and the ionic conductivity can reach ∼6.2 × 10–4 S·cm–1 at 80 °C. At the same time, the electrochemical stability and cycle stability of the electrolytes are enhanced due to the optimized process. The discoloration reaction of PVDF-HFP in composite electrolytes is further studied in this work as well. In addition to excellent performance, the simple process based on the solvent-free method also lays the foundation for scale-up production.
The poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is expected to prepare electrolytes with wide electrochemical window owing to its excellent antioxidant capability. However, the inert lithium ion conduction of the C–C skeleton severely limits its electrochemical application. In this work, high-voltage-resistant sulfolane (SL) is used as a plasticizer into the PVDF-HFP skeleton to prepare gel electrolytes. Moreover, to alleviate the incompatibility of SL with lithium metal by the strong dipole–dipole interaction between poly(ethylene oxide) (PEO) and SL, a plasticized PVDF-HFP/PEO gel polymer electrolyte (PPS-GPE) was achieved, which exhibits a high ionic conductivity of 1.67 × 10–4 S cm–1 and an electrochemical stability window of 4.8 V. The assembled Li||LiCoO2 cells show a high average discharge capacity of 153 mA h g–1 between 3.0 and 4.4 V, with a retention of 77% within 400 cycles at 0.2 C. This work provides a new strategy for the development of high-voltage, high energy density, and high safety lithium metal batteries.
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