Key Technology And Equipment For Electrospinning The Separator For Power Lithium-ion Battery

At present, it is because that it has high operational voltage, high specificenergy, high energy density, long cycle lifetime, low self-discharge rate, smallenvironmental pollution, no memory effect, and so on, lithium-ion batteriesbecome the main power of many electronic products. With the rapid developmentof new energy vehicles, having more rapid performance of charging anddischarging, security and separator stability are necessary for lithium-on battery.In order to realize that, it is one of the most difficult problems that no enoughoutput and high quality of separator are produced by traditional productionprocess. Therefore, it is necessary to research new production equipment andprocess for developing separator of power lithium-on battery.In this dissertation, separators of lithium-on battery were made byelectrospinning. In order to improve output of separator, many varieties of nonozzle electrospinning equipment were invented independently. With manyvarieties kinds of polymer nanofiber membranes were produced by differentelectrospinning equipments. The fiber membranes were characterized, and thePVDF-PMMA composite nanofiber membranes were used as the separator oflithium-on battery, and their electrochemical performance was tested. Theproperty of the equipments developed here could be evaluated by thecharacterization data. The main research contents are as follows.Based on the basic principles of electrospinning, we designed many sets ofjet, collecting and supply devices through analyzing the forming process andconditions of the Taylor cone during electrospinning process. The jet devicesincluded planar metal, metal roller (drum) and metal wire, and the collectingdevices included rotating roller and conveyor. Compared with single nozzle, thedeveloped electrospinning equipment increased three orders of magnitude inyield.The polymer fiber membrane of PVA and PEO and the composite fibermembrane of PVA-PEO, PVA-PVP, and PVDF-PMMA were fabricated by usingdifferent electrospinning devices, and then these samples were characterized andanalyzed. The results showed that the spinning threshold voltage of the roller(drum) jet device was between60to70kV, the speed of jetting was fast, the fiberwas easy to adhere with each other, and its uniformity was poor. The newequipment consisting of the rotating roller, conveyor belt and circular collectiondevice solved the problems of the fiber adhesion, fiber standing and continuouscollection. The spinning threshold voltage of metal wire jet device was between 15to35kV. Different polymers and concentrations required differentelectrospinning voltage. The jetting speed of metal wire was moderate and mostfibers had good fibrous morphology.The PVDF-PMMA composite nanofiber membranes made by wire andsingle nozzle electrospinning equipment and commercial PP/PE/PP membranewere assembled into lithium-on battery, and their electrochemical performancewas tested. It was found that from aspects of uniformity, porosity, absorption rate,ionic conductivity, charge discharge and cycle performance, PVDF-PMMA fibermembrane prepared by metal wire device was poorer than that produced by thesingle nozzle device, while better than commercial PP/PE/PP membrane.