Effect of hydroxyls and particle size on the electrochemical performance of boehmite coated PE separators for lithium-ion batteries

Boehmite particles with or without hydroxyls and those of different particle sizes were coated on PE membrane with water-based slurry, and properties of coated separators were characterized. Scanning electron microscope (SEM) was used to examine the uniformity and integrity of the coatings. X-ray diffractometer (XRD) and Fourier transform infrared spectrometer (FT-IR) were used to identify the phases and hydroxyls, respectively. Half cells were assembled with metal Li and LiFePO4 as working electrodes, and their electrochemical performance were tested. It is found that coated separators with boehmite particles and those with hydroxyls removed do not show significant difference in water wettability, neither do corresponding cells in electrochemical performance. Although boehmite particles of all sizes investigated can be coated on PE to improve separator properties and cell electrochemical performance, particles with size distribution of (D10 0.35 μm, D50 0.50 μm, D90 0.67 μm) are the most effective.