Study On Preparation And Performance Of PI/POSS/Li-OMMT Lithium-ion Battery Separator

Lithium-ion battery separator is one of the important battery components that could isolate positive and negative electrodes,store electrolyte and provide carrier transport channels.The properties of existing polyolefin separators have some weakness,such as low porosity,poor electrolyte wettability,and heat resistance are also limited by the polyolefin material,which gradually fail to meet the performance requirements of high-performance lithium-ion batteries.Therefore,it is necessary to develop a separator with excellent comprehensive performance to promote the development of the new energy industry.In this experiment,fiber separators were prepared by electrospin,and biphenyl-type polyimide(PI)was used as the substrate to provide good heat resistance for the separators.Aminopropyl caged sesquisiloxane(OAPS)and lithium-based montmorillonite(Li-OMMT)were selected to enhance the electrochemical performance of PI fiber separators by dynamic equilibrium transport of lithium-ions and lithium enrichment,and the prepared fiber separators were subjected to fiber morphology,mechanics,thermal and other properties testing and analysis.Firstly,OAPS was selected to modify PI to investigate the effect of OAPS contents on the performance of PI/OAPS fiber separator.The performance of the fiber separator was better when the OAPS content was 1.2 wt%.To further enhance the electrochemical performance of the 1.2 wt%PI/OAPS fiber separator,Li-OMMT was selected for its pre-lithiation modification,and PI/OAPS/Li-OMMT fiber separators with different Li-OMMT contents were prepared.The test results showed that the best overall performance of the fiber membrane was achieved when the Li-OMMT content was 3wt%,and the fiber membrane had good morphology,porosity of 65%,tensile strength of 6.72 MPa,no dimensional shrinkage at 300°C,and initial decomposition temperature is 536°C.The CR 2032 cell was assembled using Celgard 2400,PI,1.2 wt%PI/OAPS and 3wt%PI/OAPS/Li-OMMT fiber separator for electrochemical and cell performance tests,respectively.The test results showed that the best battery performance was achieved using the 3 wt%PI/OAPS/Li-OMMT fiber separator,with the interfacial impedance between the electrode and separator reduced to 267?,the ionic conductivity increased to 2.54×10^-3S/cm,and the electrochemical stability window reached 5.39 V.The coulomb efficiency in the first charge/discharge test reached 94.66%,and the initial discharge specific capacity at 1 C was 130.41 m Ah/g.and the capacity retention rate was 96.04%after 100 cycles,while showing good multiplicative performance.Collectively,the 3 wt%PI/OAPS/Li-OMMT fiber separator performed better than the pure PI fiber separator and the Celgard 2400 separator.