Plasma Modified Polypropylene Membranes as the Lithium-Ion Battery Separators

摘要

To reduce the thermal shrinkage of the polymeric separators and improve the safety of the Li-ion batteries,plasma treatment and plasma enhanced vapor chemical deposition(PECVD)of SiO_x-like are carried out on polypropylene(PP)separators,respectively.Critical parameters for separator properties,such as the thermal shrinkage rate,porosity,wettability,and mechanical strength,are evaluated on the plasma treated PP membranes.O_2 plasma treatment is found to remarkably improve the wettability,porosity and electrolyte uptake.PECVD SiO_x-like coatings are found to be able to effectively reduce the thermal shrinkage rate of the membranes and increase the ionic conductivity.The electrolyte-philicity of the Si Ox-like coating surface can be tuned by the varying O_2 content in the gas mixture during the deposition.Though still acceptable,the mechanical strength is reduced after PECVD,which is due to the plasma etching.