| Lithium-ion battery separator is an important part of lithium-ion battery technology,and its performance can directly affect the electrochemical performance of the battery.Therefore,the research of separator has great research value for the development of battery technology.Electrospinning technology as a new film-making technology can be found in many fields,and its special film-forming process can also make the lithium ion battery separators with better electrochemical performance.However,electrospinning technology is still in the research stage The lower output and poorer mechanical strength of electrospun film make it difficult to adapt the industrial production.In order to explore the film forming mechanism of electrospinning,increase electrospinning film production efficiency,understand the performance of electrospun separators in lithium-ion battery systems,and improve their mechanical strength.The main content of the paper is as follows(1)The basic theories of hydrodynamics and electrodynamics involved in the electrospinning process are described and analyzed,and the force of charged droplets in the space electric field is analyzed.In the electrospinning technology,the process of droplets becoming jets was simulated,and the jet state under different voltages,viscosities,and surface tensions was analyzed and discussed,and the main factors affecting jet ejection in needleless electrospinning technology were determined.And provide the theoretical basis for the design of needleless electrostatic spinning equipment.(2)Through the electric field simulation of spinning electrodes of different shapes such as circles,triangles,quadrilaterals,pentagons,and hexagons,by comparing the average value and the variation coefficient(CV value)of the electrode peaks at various angles during rotation),established the quadrilateral electrode as the best spinning electrode in the design situation.By comparing the mean value of the electric field intensity and the CV value on the plane 0.5 mm above each spinning electrode under different arrangement conditions,the spinning electrode with a pitch of 7 mm and the staggered arrangement mode was established as the optimal spinning electrode model under design conditions.Designed the liquid supply system and receiving device matched with the needleless electrostatic spinning nozzle,and completed the construction of the needleless electrostatic spinning prototype.The accuracy of the simulation content and the reliability of the designed spinning electrode were verified by the spinning experiment.(3)The electrospun polyimide(PI)fiber membrane was assembled into a button-type lithium ion battery,which was subjected to an electrochemical test.The test results showed that the ionic conductivity of the PI membrane was 1.310E-3 S/cm.The chemical stability window is 5.5 V,which is higher than the traditional Asahi PE membrane 0.201 E-3 S/cm ion conductivity and its 4 V-4.5 V electrochemical stability window.The physical properties such as surface morphology,thermal stability,and contact angle of PI film were measured(4)Two improvements are proposed for the poor tensile strength of electrospun films.One is the oriented nanofiber membrane collected by high-speed rollers,the tensile strength of the fiber membrane is increased to 63.5 MPa,and the porosity is 78.3%?Further,by adjusting the receiving speed of the drum,a multi-oriented composite film with a sandwich structure had be prepared to adjust the balance between the porosity and tensile strength of the fiber film.The other is skeleton composite nanofiber membrane which composite by melted polymer skeleton that prepared by the electrostatic direct writing technology and the PI electrospun film.And the tensile strength of the fiber membrane is increased to 34.2 MPa. |
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