Fabrication of a novel sandwich-like composite separator with enhanced physical and electrochemical performances for lithium-ion battery

• A sandwich-like PP nonwoven/PVdF-HFP separator with the introduction of PMMA nanoparticles on the surface is constructed.
• The composite separator possesses enhanced thermal stability and electrolyte uptake.
• The coin-type half-cells display excellent C-rate capacity and cyclability.

In this work, two kinds of composite separators are prepared and used for lithium-ion batteries, which are a PP nonwoven/PVdF-HFP/PMMA blending-type composite separator (CS) and a sandwich-like PP nonwoven/PVdF-HFP composite separator with the introduction of PMMA nanoparticles on the surface (nano-CS). The morphology, electrolyte uptake, ionic conductivity and electrochemical properties of the separators are studied by SEM analysis, impedance measurements, charge–discharge cycle and C-rate tests, respectively. The nano-CS and CS(0.2) exhibit similar properties in electrolyte uptake (212% and 202%, respectively) and porosity (77.9% and 75.3%, respectively). Nonetheless, nano-CS shows enhanced thermal stability and higher ionic conductivity compared with CS(0.2) and commercial PP nonwoven/PVdF-HFP separators. Meanwhile, the LiFePO4/Li half-cell assembled with nano-CS displays the best C-rate capacity and cyclability especially at the high discharge current rate, indicating that the nano-CS separator is a kind of promising candidate for the high-performance lithium-ion batteries.

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