The Melioration of Solid Polymer Electrolyte(PVdF-HFP) in Lithium Batteries

• Main Authors: Wu, Ming-Long, 吳明龍
• Other Authors: Wan, Ben-Zu
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/35564862101413381408

碩士 === 國立臺灣大學 === 化學工程學研究所 === 88 === This study is focus on the melioration of PVdF-HFP(Poly (vinylidene defluoride)-co-Hexafluoropylene) polymer electrolyte. By adding some porous zeolite A、Y、ZSM-5、mordenite and MCM-41 in the electrolyte, the conductivity of it can be improved. Because the additives can adsorb a great quantity of plasticizer(EC/PC), which is a more valuable medium for the transmission of lithium ion in electrolyte. We synthesized the solid polymer electrolyte by solvent casting method. The additives in the electrolyte can be classified into three groups by the methods of pretreatment. The first group includes the fresh zeolite A、Y、ZSM-5、mordenite and MCM-41. The second contains zeolite A and Y after lithium ion exchanging procedure. The last kind of additives are these zeolites which are surface modified with CF3CH2CH2Si(OCH3)3. From a series of our study, we found that the additives zeolite A and Y can facilitate the conductivity of electrolyte more well than other additives. By the silane pre-treating procedure, the zeolites can even enhance the conducting ability of lithium ion in electrolyte, since the silane promote the dispersion of zeolites well in the organic polymer medium. At room temperature(25oC), the conductivity of the prototype electrolyte(without any additives) that we synthesized is 3.69×10-4(±0.20×10-4)S/cm. After surface modifying the fresh zeolite A by silane, the maximum conductivity we obtained is 1.20×10-3S/cm, about 3.5 times of the conductivity of the prototype electrolyte. Except electrolyte conductivity, we also investigated the mechanical strength of electrolyte by testing the relation between resistance loss and time, we found that the mechanical strength of electrolyte and the amount of additives are in direct proportion. By linear scanning voltage (LSV) testing, we can check the decomposing voltage of electrolytes. The decomposing voltage of the electrolytes that we synthesized is from 4.7V to 5.2V, which is above the average working voltage of lithium battery. That is, the electrolytes we synthesized can charge and discharge stably in the high working voltage environment of lithium battery.