摘 要

锂离子电池由于具有比能量高、充放电能力强、循环寿命长、储能效率高等一系列优点，已成为当今备受瞩目的储能设备之一。电池隔膜直接影响电池的电极结构，充放电性能及安全性能。锂离子电池要求隔膜具有优良的机械强度、较快的电解液吸液速率和较高的保液率、高度化学稳定性、低表面电阻等特性。其中，聚丙烯隔膜具有化学稳定性高、比电阻小、透气性好、成本低等优点，是最常用的电池隔膜之一。但其亲水性差，无法保证良好的电解液吸液速率和保液率，严重影响了锂离子电池的性能。本文采用热引发接枝的方法，以2-丙烯酰胺-2-甲基丙磺酸和对甲基苯磺酸钠为单体，以过硫酸钾为引发剂，将磺酸基团接枝到聚丙烯隔膜，进行亲水改性。讨论了采用不同单体，不同时间，不同引发剂对隔膜和电池性能的影响。

实验结果表明：1）当使用过硫酸钾为引发剂，AMPS或对甲基苯磺酸钠为单体，70°C下反应，成功将磺酸基接枝到聚丙烯薄膜；当使用[2-（甲基丙烯酰基氧基）乙基]二甲基-（3-磺酸丙基）氢氧化铵为单体，过硫酸钾为引发剂，可以将磺酸基接枝到聚乙烯膜上。2）当使用过硫酸钾为引发剂，2-丙烯酰胺-2-甲基丙磺酸为接枝单体，单体浓度为1.5 mol/L时，反应温度70°C，反应时间5 h，接枝效果最好，此时电池性能略有提升。电池初始充电比容量为143.8 mAh/g，放电比容量为143.1 mAh/g，经过30次循环库伦效率为97%，放电极比容量为144.9 mAh/g，充电比容量为140.1 mAh/g。

关键词：锂离子电池；聚丙烯隔膜；接枝聚合；热引发

Abstract

With high specific energy, high rate discharge capability, long cycle life, strong energy efficiency and a series of advantages, lithium-ion battery has become one of the greatest potential energy storage equipment. As an important part of lithium-ion battery, separators impose a direct impact on the battery electrode structure, charge-discharge properties and safety performance. Separators are supposed to have a series of characteristics, such as excellent mechanical strength, faster liquid absorption speed and higher liquid retention rate, high chemical stability and low surface resistance. As one of the most commonly used battery separators, the polypropylene separator possesses an apparent advantage over high chemical stability, low specific resistance, great permeability and low cost. However, due to its poor hydrophilic, effective liquid absorption speed and liquid retention rate can not be guaranteed, which has a negative impact on the performance of lithium-ion battery. In this paper, the sulfonic acid groups were grafted on the Polypropylene separators for hydrophilic modification. In the process, 2-acrylamido-2-methylpropanesulfonic acid and sodium p-toluenesulfonate are use as grafting monomers and potassium persulfate are used as initiator.The influence of monomer types, time and initiator on the performance of battery were investigated.

The results show that: 1) The sulfonic acid group is successfully grafted onto the PP film under the following reaction conditions: potassium persulfate is used as the initiator, AMPS or sodium p-toluenesulfonate is used as monomer, the grafting reaction temperature was 70 °C, the reaction time was 5 h. The sulfonic acid group is grafted onto the PE film when potassium persulfate is used as the initiator, [2- (methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium hydroxide is used as monomer, the grafting reaction temperature was 70 °C and the reaction time was 5 h. 2)The grafting effect reached the highest point when the concentration of monomer was 1.5 mol / L. At the moment, the battery performance has been improved slightly. The initial charge specific capacity has reached 143.8 mAh / g and the initial charge specific capacity is 143.1 mAh / g. After 30 cycles, the coulomb efficiency is 97%, the discharge specific capacity is 144.9 mAh / g, and the charge specific capacity is 140.1 mAh / g.

Key Words：lithium-ion battery; polypropylene separators; graft polymerization; thermal initiation

目 录

第1章 绪论 1

1.1 选题背景及意义 1

1.2 锂离子电池隔膜 3

1.2.1性能意义 3

1.2.2隔膜分类 3

1.3 聚烯烃隔膜亲水改性办法 4

1.4本论文研究思路与主要内容 5

第2章 实验部分 6

2.1 仪器与药品 6

2.1.1实验药品与试剂 6

2.1.2 实验仪器 8

2.2 实验方案 8

2.3正极材料的制备 10

2.4锂离子电池的制备 10

第3章 性能表征与结果讨论 11

3.1红外结果讨论 11

3.2接触角测试 12

3.3交流阻抗测试 13

3.4恒流充放电测试 14

3.5结论与展望 15

3.5.1 结论 15

3.5.2 展望 15

参考文献 16

致 谢 18

第1章 绪论

1.1 选题背景及意义

伴随经济高速增长，一系列环境问题及能源短缺问题越来越突出，国家出台相关政策大量扶持相应研究，其中，锂离子电池就是重要的一项。锂离子电池结构如下：

图1.1 锂离子电池结构示意图

充电时，Li 从正极脱嵌经过电解质迁移到负极材料中，电子从外电路转移到碳负极，保证电荷平衡^[1]。放电则是充电的逆向过程。锂离子穿梭效率决定了电池的工作性能，电池的充电容量越高与嵌入的锂离子数量呈正相关关系^[2]。由于具备高能量密度（3800mAh/g）及输出电压、高储能效率、优良的循环性能、环境友好、无记忆效应等优点，锂离子电池在电子产品领域应用诸多。

然而一些技术难题阻碍了锂离子电池在航空，电动汽车等领域进一步应用：