Abstract:

With the advancement of science and technology, various intelligent electronic devices, electric vehicles and grid systems have grown rapidly, and people have a growing demand for high energy density and rechargeable battery systems. In the past few decades, the development of lithium-ion batteries has made great progress. Lithium-ion batteries consisting of positive and negative electrodes, electrolytes and separators has the danger of volatile and leakage, leading to short circuit, fire, explosion and other safety accidents. The emergence of solid electrolytes has largely eliminated this safety hazard. The solid-state electrolyte can not only separate the positive and negative electrodes in the battery to prevent internal short circuits, but also act as an ion conductor to achieve the dual role of lithium ion transfer between positive and negative active substances. The solid-state electrolyte has become one of the research hotspots in the field of new energy. At present, the preparation methods of solid electrolyte membranes mainly include organic solvent casting/coating or hot molding. Organic solvents used by these methods are not friendly to the environment and these methods have disadvantages like high manufacturing cost and low production efficiency. To solve this problem, this paper proposed a new method for preparing PEO-based composite solid electrolyte membrane based on tensile stress and solvent-free melting, characterized the crystalline morpho-logy and microscopic morphology of the electrolyte membrane by SEM and XRD, and characterized the thermal properties of the membrane by DSC and FT-IR. The electrochemical performance of the membrane was characte-rized by linear sweep voltammetry and conductivity test. The results show that, as compared with simple mechanical mixing, the PEO/LiTFSI/PVDF composite solid electrolyte membrane prepared based on tensile stress and solvent-free melting has better lithium salt dispersibility. Ionic conductivity test shows that, even the proposed method does not use organic solvents, it is still comparable to the ionic conductivity of electrolyte membranes prepared by the solution method. When the content of PVDF-HFP is 30%, the ionic conductivity of the PEO-based solid polymer electrolyte membrane at 60 ℃ reaches 2.07×10^-4 S/cm, and the electrochemical stability window is 5.0 V.

Key words: lithium-ion battery, composite solid electrolyte, polyethylene oxide, melting preparation, tensile stress, ionic conductivity