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Partic. vol. 37 pp. 91-98 (April 2018)
doi: 10.1016/j.partic.2017.10.001

Enhanced wettability and thermal stability of nano-SiO2/poly(vinyl alcohol)-coated polypropylene composite separators for lithium-ion batteries

Zhixiong Zhanga, Wenhui Yuana,*, Li Lib

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cewhyuan@scut.edu.cn

Highlights

    • Nano-SiO2/PVA-coated PP composite separators were fabricated by sol–gel and dip-coating methods. • Effects of the tetraethoxysilane (TEOS) dosage on the composite separators were investigated. • Composite separator using 7.5 wt% TEOS exhibited better electrochemical performance.

Abstract

To improve the electrolyte wettability and thermal stability of polypropylene (PP) separators, nano-SiO2/poly(vinyl alcohol)-coated PP composite separators were prepared using a simple but efficient sol–gel and dip-coating method. The effects of the tetraethoxysilane (TEOS) dosage on the morphology, wettability, and thermal stability of the composite separators were investigated using Fourier-transform infrared spectroscopy, scanning electron microscopy, and contact-angle measurements. All the composite separators gave a smaller contact angle, higher electrolyte uptake, and lower thermal shrinkage compared with the PP separator, indicating enhanced wettability and thermal stability. Unlike the case for a traditional physical mixture, SiOC covalent bonds were formed in the coating layer. The composite separator with a TEOS dosage of 7.5 wt% had a unique porous structure combining hierarchical pores with interstitial voids, and gave the best wettability and thermal stability. The ionic conductivity of the composite separator containing 7.5 wt% TEOS was 1.26 mS/cm, which is much higher than that of the PP separator (0.74 mS/cm). The C-rate and cycling performances of batteries assembled with the composite separator containing 7.5 wt% TEOS were better than those of batteries containing PP separators.

Graphical abstract

Keywords

Wettability; Thermal stability; Composite separator; Lithium-ion batteries