Abstract
Gel polymer electrolytes have the advantages of both a solid electrolyte and a liquid electrolyte. As a transitional product before which a solid electrolyte can be comprehensively used, gel polymer electrolytes are of great research value. They can reduce the risk of spontaneous combustion and explosion caused by leakage during the use of conventional liquid electrolytes. Poly(vinylidene-fluoride-co-hexafluoropropylene) (PVDF–HFP), a material with excellent performance, has been widely utilized in the preparation of gel polymer electrolytes. Here, PVDF–HFP-based gel polymer membranes with polyvinyl pyrrolidone (PVP) pores were prepared using a phase inversion method, and Octavinyl-polyhedral oligomeric silsesquioxane (OVAPOSS) was doped to improve its temperature resistance as well as its ionic conductivity, to enhance its safety and electrochemical performance. The final prepared polymer membrane had a porosity of 85.06% and still had a certain mechanical strength at 160 °C without any shrinkage. The gel polymer electrolyte prepared with this polymer membrane had an ionic conductivity of 1.62 × 10−3 S·cm−1 at 30 °C, as well as an electrochemical window of about 5.5 V. The LiCoO2-Li button half-cell prepared therefrom had a specific capacity of 141 mAh·g−1 at a rate of 1C. The coulombic efficiency remained above 99% within 100 cycles and the capacity retention rate reached 99.5%, which reveals an excellent cycling stability.
Highlights
Since the invention of lithium-ion batteries in the 1870s, there has been significant development in various electronic mobile devices, due to their high specific capacity and portability which, in turn, have promoted the further development of the lithium-ion battery industry
The appearance of large pores indicated that more polyvinyl pyrrolidone (PVP) in the system had been transferred out, which was due to the fact that the unique organic–inorganic composite structure of OVAPOSS played an excellent role in its distribution in the organic membrane
PVDF–HFP, PVP, and OVAPOSS were used as raw materials to successfully prepare porous polymer membranes with a high performance and high safety using a phase inversion method
Summary
Since the invention of lithium-ion batteries in the 1870s, there has been significant development in various electronic mobile devices, due to their high specific capacity and portability which, in turn, have promoted the further development of the lithium-ion battery industry. The existing lithium-ion battery system mainly uses liquid electrolytes. Gel polymer electrolytes (GPEs) combine the characteristics of solid electrolytes and liquid electrolytes. Due to their good ionic conductivity (room temperature >10−4 S·cm−1), wide electrochemical window, and good electrode compatibility, GPEs have attracted much attention [5,6,7].Poly(1,1-difluoroethylene) (PVDF), an excellent material, has the advantages of corrosion resistance, temperature resistance, easy film formation, and a high dielectric constant. The crystallinity of PVDF–HFP is much lower than that of PVDF alone and the GPEs prepared by PVDF–HFP display a higher room temperature conductivity, so it is being widely applied in lithium-ion batteries [11]
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