PVA-ZrO2 multilayer composite separator with enhanced electrolyte property and mechanical strength for lithium-ion batteries

The separator has an important influence on safety and charge-discharge performances of lithium-ion batteries. In this work, a multilayer composite separator is designed and fabricated by alternate electrospinning of poly (vinyl alcohol) (PVA) nanofibers and electrospraying of ZrO2 nanoparticles. The physical-chemical properties of the separator are systematically investigated. The design of such a layer-by-layer structure not only enhances the electrolyte uptake/retention and thermal resistance but also improves the mechanical strength of the composite separator. In comparison with PE separator and pure PVA electrospun separator, this PVA-ZrO2 composite separator exhibits satisfactory thermal resistance (area shrinkage ratio of 0% at 160 °C), ionic conductivity (2.19 mS/cm), electrolyte wettability (uptake of 350%) and tensile strength (14.5 MPa) as well as better interface compatibility. Moreover, a LiFePO4–Li half-cell with PVA-ZrO2 composite separator displays superior C-rate and cycling performances. It shows a high discharge capacity of 73.0 mA h/g at 16C, which is about 50% of that at 0.2C. The reason for the high capacity retention is the efficient Li+ transmission through the separator, resulting from the well-defined porous structure and the Lewis acid-base interactions of the PVA-ZrO2 composite separator. It can be concluded that this type composite separator with layer-by-layer structure possesses good application prospects for high-performance lithium-ion batteries.