Abstract
AbstractAn aqueous silica (SiO2) dispersion was prepared by using silica as ceramic particles, polyvinyl alcohol (PVA) as a binder and deionized water as a dispersion medium. A SiO2 ceramic layer was applied to the surface of the polypropylene (PP) separator by dip coating. The separators before and after modification were characterized by XRD, SEM, DTA, lyophilic performance test, contact angle test and heat resistance test. The separators were assembled into lithium-ion batteries for electrochemical performance test. The results show that after the successful introduction of SiO2/PVA coating on the surface of PP separator, the lyophilic and heat resistance and electrochemical performance of PP separator have been improved significantly. The battery rate performance and cycle performance are significantly improved. Especially the capacity retention rate of the original separator was only 75.79% at 100 charge-discharge times, and that of the modified separator was as high as 87.18%.
Highlights
A suitable size PP (Celgard 2400) separator was completely immersed in absolute ethanol for about 20 min and dried at 60°C for use. 0.5 g of Polyvinyl alcohol (PVA) (1788, 44.05 Mw, Aladdin) powders were added into 50 mL of deionized water, and continue stirring at 90°C until PVA was completely dissolved. 0.5 g of nano-SiO2 powder was added in the PVA solution system
The thermal shrinkage of the separators (2 cm × 2 cm) were calculated by measuring the size variation after being heat treated for 1 h at different temperatures (130-170°C), using Eq 2: Thermal shrinkage = So −St ×100% [2] So where So is the area of the original separator, and St is the area of the separator after being heat treated for 60 min [19]
SiO2/PVA slurry was prepared by using nano-SiO2 ceramic powder as filler, PVA as binder and deionized water as solvent
Summary
X. Wang et al.: Preparation and performance of polypropylene separator 471 composite membrane has good electrolyte wettability and absorption, high ionic conductivity, which makes lithium ion batteries have excellent cycle performance. Shi et al prepared a separator modified by nanometer ceramic powders for lithium-ion battery, which showed good high temperature stability, high absorption and wettability of electrolytes [15]. The composite membrane is mainly composed of calcium carbonate powder and polymer binder It has high porosity and good capillary properties, and has good wettability with liquid electrolyte. Considering the liquidphilic and heat-resistant properties of the separator, in this work, SiO2 is selected as inorganic ceramic filler. The heat resistances, hydrophilic and electrochemical properties of the composite separator were investigated
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