Study On Performance Of P(VDF-TrFE)-based Composite Lithium Ion Battery Separator

Storing the current remaining energy through the battery is one of the most convenient and effective ways to solve the energy shortage problem in the future,and the lithium ion battery is the main power source of many electronic devices at present.However,the development of separators is the bottleneck of the rapid development of lithium-ion batteries,so the development of new composite separators is the top priority for improving the performance of lithium batteries.In this paper,the fluoropolymer P（VDF-TrFE）with high dielectric constant and low crystallinity is selected as the matrix,inorganic nanoparticles are added to it,and the composite film is prepared by solution casting.The morphology,crystallinity,thermal stability,mechanical properties,liquid absorption and electrochemical stability of the composite film were tested by SEM,XRD,DSC,TGA,FT-IR.tensile test and electrochemical test.T he research results are as follows:1)P（VDF-TrFE）material was prepared by dehydrochlorination reaction,and BaTiO₃ and ZrO₂ nanoparticles with different mass fractions were added to it for compounding,and then BaTiO₃/P（VDF-TrFE）and ZrO₂/P（VDF-TrFE）nanocomposite film.It was found that with the increase of the doping amount of inorganic ceramic particles,the crystallinity,tensile fracture strength,porosity and liquid absorption rate of the separator gradually increased.When the mass percentage of the ceramic particles reached 15%,the performance of the separator could reach the optimal value,above The performance is better than the commercial film Celgard 2400.2)PDA@BaTiO₃ and PDA@ZrO₂ nanoparticles with different mass fractions were added to the P（VDF-TrFE）polymer matrix respectively,and PDA@BaTiO₃/P（VDF-TrFE）and PDA@ZrO₂/were prepared by solution casting P（VDF-TrFE）composite film.It was found by comparison that the crystallinity of the composite membrane modified by hydroxyl-rich PDA cell temperature.At the same time,the modification of dopamine reduced the tensile strength of the PDA@ZrO₂/P（VDF-TrFE）separator,but the elongation at break increased significantly,the mechanical strength was improved,and the porosity and wettability were improved.3)The button battery was assembled in the traditional way and its performance was tested.It was found that the discharge specific capacity of the ZrO₂/P（VDF-TrFE）battery separator was as high as 135 mA·h·g-1,and the Coulomb efficiency continued to stabilize at 100%The interface impedance value is less than that of the commercial Celgard 2400 sample film.In addition,the interface impedance of the ZrO₂/P（VDF-TrFE）separator with a mass percentage of 15%is smaller,and the internal redox reaction of the battery is easier;compared to before coating,The PDA@ZrO₂/P（VDF-TrFE）diaphragm is in closer contact with the electrode,the interface impedance is smaller,and it is more conducive to charge transfer,indicating that the modification of the PDA is beneficial to improve the affinity between the diaphragm and the electrode.The above results show that P（VDF-TrFE）ferroelectric polymer is used as the base material,and the composite film constructed by PDA modified BaTiO₃ and ZrO₂ as filled inorganic material has excellent mechanical and physical and chemical properties,plus the use of its encapsulated button battery with excellent charge and discharge performance,the PDA@BaTiO₃/P（VDF-TrFE）and PDA@ZrO₂/P（VDF-TrFE）separators can be said to provide references for subsequent application research.