A water-based silica (SiO2) dispersion was prepared with SiO2 as ceramic particle and polyvinyl alcohol (PVA) as binder

and the composite separator for lithium-ion batteries was prepared by the introduction of SiO2 layer on both sides of polypropylene (PP) separator surface through a dip-coating process.The surface and cross-section morphology of SiO2/PVA layer were investigated

and the porous structure of pristine and composite separators was quantitatively analyzed by the porosity and the Gurley value.The contact angles of water and water-based SiO2 dispersion with and without the surfactant on PP surface were measured

and the influence of the coated layers on thermal stability

wettability

electrolyte uptake

ionic conductivity

C-rate capability and cyclability was researched.The test results showed that the coated layer had porous network structure and its thickness was only 800 nm.Owing to the introduction of the porous thin layer on PP separator surface

the porosity of the composite separator increased to 62.9% and the Gurley value of composite separator decreased to 515 s.Compared to the pristine separator

the composite separator showed not only lower thermal shrinkage but also better wettability with liquid electrolyte and higher electrolyte uptake.Furthermore

the composite separator exhibited higher ionic conductivity and better cell performance such as C-rate capability and cycle performance.