Modification And Application Of Polyetherimide Based Separator For Lithium-Sulfur Battery

Lithium-sulfur battery has excellent theoretical specific capacity and energy density,which can theoretically adapt the increasing requirements of energy storage system.As an important part of battery,separator affects the electrochemical stability and life of battery.In this paper,polyetherimide（PEI）was used as the polymer matrix to prepare separator for lithium-sulfur battery,which was filled with nanoparticles and modified on surface to optimize its performance.At the same time,the modified separator was filled with carbon material to prepare interlayer and applied to lithium-sulfur battery.The main contents are as follows:（1）Using PEI as the polymer matrix and nano Zr O₂as filler,a novel separator was prepared by NIPS method,and the effects of nano Zr O₂on the performance of the PEI based separator was studied.The prepared PEI separator has a typical asymmetric finger-like pore structure.When the addition amount of Zr O₂is 6 wt%,the reversible capacity of lithium-sulfur battery reaches 496 m Ah g^-1after 100 cycles with the discharged rate of 0.2 C,and its capacity retention rate reaches 38%with the discharged rate of 2 C.（2）Taking the optimal PEI separator filled with Zr O₂（PZ-6）as based separator,a composite layer on the surface of the separator was obtained by interfacial polymerization/carbon coating,and the effects of two modification methods on the properties of the separator were studied.The effect of carbon coating on the performance of the separator is mainly to inhibit the shuttle of polysulfides,while the effect of interfacial polymerization on the performance of the separator is mainly to improve the lithium ions transfer ability.The prepared composite layer can get both advantages of them.The modified interfacial polymerization/carbon coating（JCPZ）separator has an initial discharge capacity of 1242 m Ah g^-1with the discharged rate of 0.2 C,a capacity retention rate of 68%after200 cycles,high lithium ion transfer number（0.55）and diffusion coefficient(2.16×10^-8cm s^-1).（3）PZ-6 casting solution was filled with conductive carbon to prepare the separator,which was used as an interlayer in lithium-sulfur battery.It can be seen from SEM that the obtained interlayer has the same structure as PZ-6 separator.The lithium-sulfur battery using PE separator with graphene interlayer（GPZ）has excellent initial cycle discharge specific capacity(1280 m Ah g^-1with the discharged rate of 0.2 C),high capacity retention（60.9%after 200 cycles）and good rate performance(580 m Ah g^-1at 2 C).The introduction of graphene not only promotes the lithium ions transfer ability of the interlayer,but also plays an important role in preventing the shuttle of polysulfides.