| 题名 | 新型硼酸锂盐基聚合物电解质的制备与性能研究 |
| 作者 | 王学江 |
| 学位类别 | 硕士 |
| 答辩日期 | 2013-07 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 刘志宏 ; 崔光磊 |
| 关键词 | 聚合物电解质 单离子导体 聚合硼酸锂盐 高温电池 锂离子电池 |
| 学位专业 | 化学工程 |
| 中文摘要 | 聚合物电解质是锂离子电池的关键材料之一，具有隔绝正负极片防止电池短路和提供锂离子传输的作用。本论文设计并合成了一种新型的聚合物硼酸锂盐——酒石酸硼酸锂盐(PLTB)，并基于该锂盐制备出了一种单离子导体类聚合物电解质。该聚合物电解质表现出宽的电化学稳定窗口，良好的离子电导率，高的锂离子迁移数，以及优异的高温稳定性能。最后将聚合物电解质组装成锂离子电池进行充放电性能，倍率性能和循环性能等测试。具体主要包括以下几个方面的内容：(1) 采用水相法一步合成了一种聚合物型的锂盐(PLTB)，该方法制备工艺简单，反应以水作为介质，副产物仅有水生成，符合绿色化学发展理念，可应用于产业化生产。制备出的PLTB以聚阴离子作为主链，并且具有比双草酸硼酸锂盐(LiBOB)更高的锂离子浓度。该锂盐的热分解温度高达330 ℃，高于LiBOB的热分解温度(302 ℃)。(2) 基于该锂盐，我们制备出了单离子导体类聚合物电解质PLTB@PVDF-HFP，并加入适量的增塑剂以改善其离子电导率。聚合物电解质中PLTB与PVDF-HFP具有良好的相容性且分散均匀稳定，制备的膜不含有孔结构。该聚合物电解质高温下表现出高的电化学稳定性(20 ℃下氧化分解电位为5.0 V vs. Li+/Li，下同，80 ℃下氧化分解电位为4.7 V)和低电位下良好的嵌脱锂能力，与金属锂片良好的相容性，优异的钝化集流体铝的能力，室温下表现出良好的离子电导率(EC/DMC-PLTB@PVDF-HFP室温下的离子电导率为5.0×10-4 S cm-1，EC/DMC: PLTB@PVDF-HFP = 2: 1, w: w)，高的锂离子迁移数(t+ = 0.92)。(3) 基于制备出的PLTB基聚合物电解质，我们组装了Li4Ti5O12//EC/DMC -PLTB@PVDF-HFP (EC/DMC: PLTB@PVDF-HFP = 2: 1, w: w)//LiFePO4电池。PLTB基聚合物电解质与Li4Ti5O12电极、LiFePO4电极都表现出良好的相容性和界面稳定性。作为单离子导体类聚合物电解质，EC/DMC-PLTB@PVDF-HFP (75 μm)在比商业化隔膜(25 μm)更厚的情况下，其电池具有跟液态电解液体系(LiPF6-EC/DMC)电池同样小的充放电过电势。同时，Li4Ti5O12//EC/DMC-PLTB@ PVDF-HFP//LiFePO4电池在20 ℃和60 ℃下都表现出了良好的充放电曲线，平稳的充放电平台，良好的倍率性能，良好的循环稳定性和高的库伦效率。
(4) 基于制备出的PLTB基聚合物电解质，我们组装了Li/PC-PLTB@PVDF- HFP (PC: PLTB@PVDF-HFP = 1: 1, w: w)/LiFePO4电池。发现电池在120 ℃高温下依然具有良好的充放电曲线及充放电平台，电池表现出良好的倍率性能，在0.5 C下优异的循环稳定性、高的放电容量和高的库伦效率。同时，我们对金属锂片表面的锂枝晶问题进行了探讨，发现商业化电解液体系电池循环后锂片表面有大量的锂枝晶产生，而我们的聚合物锂离子电池由于使用不具有孔结构的聚合物电解质，其循环后锂片表面无明显的锂枝晶产生，这可以大大提高电池的安全性能。Li/PC-PLTB@PVDF-HFP/LiFePO4二次电池在120 ℃高温下的成功运行使其在特殊应用领域中具有非常大的发展前景，有望应用于未来的石油、天然气探勘，以及航天，军工等领域。 |
| 英文摘要 | As one of the key components in lithium ion batteries, the polymer electrolyte plays a significant role in insulating the cathode and anode to avoid short circuit and providing the transmission of lithium ions. In this dissertation, a novel polymeric lithium tartaric acid borate (PLTB) was designed and synthesized. And a new kind of single-ion polymer electrolyte based on PLTB was further prepared. The polymer electrolyte exhibited excellent electrochemical stability, favorable ionic conductivity, high lithium ion transference number and excellent stability at high temperature. The coin cells were assembled using as-prepared polymer electrolyte and the battery performance was examined, such as charge/discharge profiles, rate performance, cycling performance and coulombic efficiency. These are described as follows:(i) A novel PLTB was synthesized via a one-step reaction in an aqueous solution. The PLTB was low cost owing to abundant precursors from biomass and the facile synthesis. Besides, the synthesis process was benign to environment because of using aqueous solution and biomass based materials. The as-prepared PLTB processed a polyanion structure as a main chain and had a higher lithium ion concentration than LiBOB. In addition, PLTB had a higher thermal decomposition temperature at 330 ℃, when compared with that of LiBOB (302 ℃).(ii) A new kind of single-ion polymer electrolyte (PLTB@PVDF-HFP) was prepared based on PLTB, and some amount of plasticizer was added to improve its ionic conductivity at room temperature. The solvent swollen PLTB@PVDF-HFP (S-PLTB@PVDF-HFP) was homogeneous and there was no porous structure, which was vital to prevent the generation of Li dendrite. It was manifested that the S-PLTB@PVDF-HFP exhibited excellent electrochemical stability (oxidatively degrade above 5.0 V at 20 ℃ and 4.7 V at 80 ℃) and lithium deposition-stripping performance, favorable ionic conductivity at room temperature (5.0×10-4 S cm-1 for EC/DMC-PLTB@PVDF-HFP (EC/DMC: PLTB@PVDF-HFP = 2: 1, w: w)), high lithium ion transference number (t+ = 0.92).(iii) The Li4Ti5O12//EC/DMC-PLTB@PVDF-HFP (EC/DMC: PLTB@PVDF- HFP = 2: 1, w: w)//LiFePO4 cells were assembled. The cells showed good charge/ discharge profiles and stable charge/discharge plateaus at 20 ℃ and 60 ℃, which meant that PLTB@PVDF-HFP based polymer electrolyte had good interface compatibility with Li4Ti5O12 and LiFePO4 electrodes. In the case of our polymer electrolyte (75 μm) thicker than the membrane (25 μm), the polarization and resultant voltage difference of PLTB@PVDF-HFP based cells was comparable to that of LiPF6 electrolyte based cells under 0.5 C at ambient temperature, which was attributed to the high lithium ion transference number. Also, the Li4Ti5O12//EC/ DMC-PLTB@PVDF-HFP//LiFePO4 cells exhibited preferable rate capability, excellent cycling performance and high coulombic efficiency both at 20 ℃ and 60 ℃. (iv) Li/PC-PLTB@PVDF-HFP (PC: PLTB@PVDF-HFP = 1: 1, w: w)/LiFePO4 cells were assembled to present superior battery performance under higher temperature, such as 120 ℃. It was manifested that the cells exhibited excellent charge/discharge profiles, stable charge/discharge plateaus, good rate capability, good cycling performance and high coulombic efficiency. In the Li//LiPF6-EC/DMC //LiFePO4 cells using Celgard 2500 as separator, the surface of lithium metal foil became rather rough and was composed of a large amount of Li dendrites after 50 cycles at 50 ℃. While, for the Li/PC-PLTB@PVDF-HFP/LiFePO4 cells, the surface of lithium metal foil was relatively smooth and there was no sign of Li dendrite after 50 cycles at 50 ℃. The PC-PLTB@PVDF-HFP was homogeneous which was vital to prevent the generation of Li dendrite, and this could greatly improve the safety characteristic of the battery. The successful operation of our Li/PC-PLTB@ PVDF-HFP/LiFePO4 cells under the temperature of 120 ℃ could endow this kind of polymer electrolyte based cells a very promising application for some special fields, such as drilling tools' power battery for the oil drilling market, aerospace, aviation and military industry. |
| 语种 | 中文 |
| 学科主题 | 仿生能源系统 |
| 公开日期 | 2013-07-13 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.qibebt.ac.cn:8080/handle/337004/1511]  |
| 专题 | 青岛生物能源与过程研究所_仿生能源与储能系统团队 |
| 推荐引用方式 GB/T 7714 | 王学江. 新型硼酸锂盐基聚合物电解质的制备与性能研究[D]. 北京. 中国科学院研究生院. 2013. |
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