Enhancing Stability of Glass Fiber Separators in Lithium-Ion Batteries through Sol-Gel Hybrid Coatings

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Lithium ion batteries are largely divided into an anode, a cathode, and a separator impregnated with an electrolyte. It is well known that the battery separator is an important element in all batteries, as it physically separates the anode and cathode to prevent the direct flow of electrons, and allows the flow of charge through the movement of ions. Polyolefin-based separators, which are widely used in existing batteries, are vulnerable to rapid environmental changes, drastically reducing battery performance. Additionally, the thermal contraction and expansion that leads to a short circuit significantly reduces the stability of the battery. To overcome stability in such extreme environments, glass fiber separators are emerging as an alternative. To overcome stability in such extreme environments, glass fiber separators are emerging as an alternative. Glass fiber has excellent mechanical properties, electrical insulation, heat resistance, and chemical resistance, so it can drastically improve the stability of the battery. It can also improve electrolyte impregnation by controlling porosity to improve battery performance.In this study, a sol-gel hybrid coating solution was synthesized and coated on a glass fiber separator to enhance the ionic conductivity and stability. The coating on glass fiber was performed using a dip coating method. The optimization of the hybrid solution and coating conditions led to a reduction in the porosity and enhancement of the flexibility of the glass fiber separators. The adhesion of the coating was evaluated by measuring the hardness of the coating using pencil hardness, and the results showed that the tensile strength of the coated glass fiber separator was improved by about two times compared to before coating. Finally, as a result of evaluating the electrical performance according to the coating, the battery performance was similar at room temperature. On the other hand, it was confirmed that the operating voltage and discharge time at low temperatures were increased by the sol-gel hybrid coating. These results suggest that the coated glass fiber separators are promising candidates for overcoming the stability of battery operation in extreme environments.