新型聚碳酸酯电解质制备及在高性能固态锂电池中的性能研究

发布时间：2018-02-09 01:27

本文关键词： 固态聚合物电解质聚碳酸酯缩聚高电压锂离子电池　出处：《青岛科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：液态锂离子电池中的电解液普遍存在易挥发、易燃的特点,在使用过程中存在安全隐患,固态聚合物电解质因为可以有效的解决电解液这方面的缺陷而受到广泛关注。聚合物电解质同时具有质量轻、粘弹性好,易成膜等优点,用其组装的锂离子电池已经为手机、笔记本电脑等电子设备提供了高效电源。随着电极材料的不断进步,聚合物电解质已经成为决定固态聚合物锂离子电池性能的关键材料。(1)本论文利用酯交换反应合成了两种新型的聚碳酸酯,聚二乙二醇碳酸酯(PDEC)和聚三乙二醇碳酸酯(PTEC)在室温下均为无定形态的淡黄色蜡状固体,并且玻璃化转变温度均在-20 oC以下,有利于其在锂离子电池聚合物电解质中的使用。选择碳酸二乙酯与二元醇摩尔比为1.2:1,这样保证了酯交换反应的充分,制备出的聚碳酸酯分子量在8000 g·mol-1左右。(2)通过溶液浇铸法制备出两种聚合物电解质膜,分别为PDEC-LiTFSI和PTEC-LiTFSI与纤维素复合电解质膜。PTEC-LiTFSI比PDEC-LiTFSI的离子电导率高,是因为PTEC具有比PDEC更低的玻璃化转变温度,分子链段运动活性更强。实验结果证明,筛选出的PTEC基电解质在25 oC下的离子电导率为1.12×10-5S·cm-1,锂离子迁移数为0.39,电化学窗口可以达到4.5 V。用PTEC基电解质组装的LiFePO_4半电池在室温0.05 C倍率下可以可逆的充放电。此外,PTEC基组装的高电压LiFe_(0.2)Mn_(0.8)PO_4半电池(截止电压4.35 V),在室温下具有很好的倍率性能和循环稳定性。(3)设计并合成了新型的氟代聚碳酸酯,聚四氟丁烷碳酸酯(PTFBC),室温下PTFBC为白色固体粉末,重均分子量为207500 g mol-1,分散度为2.3,熔融温度为105.2 oC。通过溶液浇铸法制备的聚合物电解质膜,形貌上平整且致密。该薄膜具有良好的阻燃效果,在室温下离子电导率可以达到1.31×10-4 S·cm-1,电化学稳定窗口可以达到5 V,锂离子迁移数为0.52。PTFBC聚合物电解质优异的电化学性能使其在高电压电池体系中的应用具有光明的前景。
[Abstract]:The electrolyte in lithium-ion battery is volatile and flammable. Solid polymer electrolytes have attracted wide attention because they can effectively solve the defects in electrolyte. Polymer electrolytes also have the advantages of light weight, good viscoelasticity and easy film formation. The lithium ion batteries assembled with them have been used for mobile phones. Laptop computers and other electronic devices provide efficient power supply. With the development of electrode materials, Polymer electrolyte has become the key material to determine the performance of solid-state polymer lithium-ion battery. In this paper, two new polycarbonate were synthesized by transesterification. Poly (ethylene glycol carbonate) (PDEC) and poly (triethylene glycol carbonate) (PTEC) are amorphous yellowish waxy solids at room temperature, and the glass transition temperature is below -20oC. The molar ratio of diethyl carbonate to diol is 1.2: 1, which ensures the sufficient transesterification. The molecular weight of the prepared polycarbonate was about 8000 g 路mol-1. (2) two kinds of polymer electrolyte membranes were prepared by solution casting. They were PDEC-LiTFSI and PTEC-LiTFSI / Cellulose composite electrolyte membranes. PTEC-LiTFSI had higher ionic conductivity than PDEC-LiTFSI. This is because PTEC has a lower glass transition temperature than PDEC and is more active in segment motion. The ionic conductivity of the selected PTEC based electrolyte is 1.12 脳 10 ~ (-5) S 路cm ~ (-1), the number of lithium ion migration is 0.39, and the electrochemical window can reach 4.5 V. the LiFePO_4 half-cell assembled with PTEC based electrolyte can be reversibly charged and discharged at the rate of 0.05C at room temperature. In addition, a novel fluorinated polycarbonate was designed and synthesized by a high voltage LiFe_(0.2)Mn_(0.8)PO_4 half-cell (cutoff voltage 4.35V, with good rate performance and cyclic stability at room temperature). Polytetrafluorobutane carbonate (PTFB C), PTFBC is a white solid powder at room temperature, the weight average molecular weight is 207500 g mol -1, the dispersion is 2.3, and the melting temperature is 105.2oC. the polymer electrolyte membrane was prepared by solution casting method. The film has good flame-retardant effect. At room temperature, the ionic conductivity can reach 1.31 脳 10 ~ (-4) S 路cm ~ (-1), the electrochemical stability window can reach 5 V, the lithium ion mobility number is 0.52.PTFBC polymer electrolyte has excellent electrochemical performance, so it has a bright future in high-voltage battery system.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ317;TM912

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