Effect of separator coating layer thickness on thermal and electrochemical properties of lithium-ion secondary batteries

This study addresses the critical gap in understanding the quantitative relationship between the thickness of ceramic coatings on separators and the overall performance of lithium-ion batteries (LIBs). Through a comprehensive investigation into the effects of varying alumina coating thicknesses on polyethylene (PE) separators, we have elucidated the impact of single-sided and double-sided coatings on separator characteristics and, consequently, on cell performance. Our findings demonstrate that increasing the thickness of the single-sided alumina coating up to 4 µm markedly enhances the mechanical and thermal stability of the separators. Also, we showed the superior thermal stability and electrochemical performance of 2 µm double-sided coating layer compared to 4 µm single-sided coating layer. Utilizing scanning electron microscopy, 3D shape analysis, and a suite of mechanical and electrochemical evaluations, we have detailed the positive ramifications of the alumina coating process. This study not only establishes a clear correlation between alumina coating thickness and separator performance but also advocates for an optimal double-side 2 µm alumina coating. Such a configuration promises to advance the energy density and safety of LIBs, offering insights for future battery development and separator optimization.