1、 锂离子电池论文：磷酸亚铁锂/硬碳锂离子电池的工艺及电化学性能研究【中文摘要】自从锂离子电池被成功研制并商业化以来,锂离子电池以其循环寿命长、工作电压高、安全性好、无记忆效应等特点越来越受到人们的青睐和重视。然而,锂离子电池电化学性能的好坏与其所使用的正负极材料、导电剂、粘结剂、电解液、隔膜等有着密切的关系。磷酸亚铁锂(LiFePO4)因其具有原料丰富、比容量高、结构稳定、安全性好等优点成为了一种比较有潜力的锂离子电池正极材料。同时,可以作为锂离子电池负极材料的硬碳(hard carbon, HC),由于其无规则的排序具有较高的容量、优良的循环性能和较低的造价等特性,使得人们对其产生了极大的兴
2、趣。本文将 LiFePO4 与硬碳组合成 LiFePO4/HC 电池,从正极材料所用的导电剂和粘结剂等工艺方面对 LiFePO4/Li 半电池及 LiFePO4/HC 全电池的电化学性能影响进行研究,并将 LiFePO4/HC 电池和 LiFePO4/石墨(AGP-3)电池的电化学性能进行比较,得出如下结论：1.对于 LiFePO4/Li 半电池,使用 Super P Li 做导电剂时,电池的电阻相对更小,在 0.2 C 和 1 C的放电倍率下,电池的放电平台都比使用乙炔黑做导电剂时更为平稳,且比容量更大。在 1 C 放电倍率下经过 150 个循环后,电池容量的保持率要相对更稳定。循环伏安测试
3、表明所使用的 LiFePO4 材料本身的循环可逆性较好,这与 LiFePO4 颗粒间存在的碳纳米管提高了其导电性可能有很大的关系。2.对于 LiFePO4/HC 全电池,同样我们得出使用 Super P Li 做导电剂时,电池的电阻相对更小且比容量更大。倍率性能测试显示,使用 Super P Li 做导电剂时电池的倍率性能更加优越,但是,可能由于所使用的粘结剂 PVDF 粘结性能不够好,使得电池在 10 C 的放电倍率下比容量很低。同时,与 LiFePO4/Li 半电池相比,全电池的电阻值要小,放电曲线没有出现平台且在 1 C 放电倍率下循环 150 次后电池的容量保持率要高。3.使用水性粘结
4、剂 SBR 和油性粘结剂 PVDF 制得 LiFePO4 极片,将其与金属锂片组合成LiFePO4/Li 电池。在 0.2 C 的放电倍率下,使用两种粘结剂体系电池的放电平台(约 3.38 V)都较为平稳,放电比容量基本相等,其中水性粘结剂 SBR 体系其比容量稍低一些,当电池放电倍率为 1 C 时,使用水性粘结剂 SBR 时,电池的首次和第 2 次放电比容量都比使用油性粘结剂 PVDF 时要高。从交流阻抗和循环寿命测试我们得知,使用水性粘结剂时电池的阻抗值更小,其 Rct 值为 89.68,在 1 C 的放电倍率下,经过 150 个循环后,电池容量的保持率要相对更稳定,其保持率为 65%。4
5、.使用两种粘结剂后,LiFePO4/HC 电池在 0.2 C 的放电倍率下,油性粘结剂体系的 LiFePO4/HC 电池的首次放电比容量要高于水性粘结剂体系,但随着循环的进行油性粘结剂体系的放电比容量会呈下降趋势,而水性粘结剂体系则会呈现一定的上升趋势。当电池在1 C 的放电倍率下进行放电时,与半电池测试结果相同,水性粘结剂体系电池的放电比容量要高于油性粘结剂体系且容量保持率要好,保持率为 97.9%。倍率性能测试显示,水性粘结剂体系电池的大倍率性能要好于油性粘结剂体系。此外,使用水性粘结剂时电池的阻抗值更小,其 Rct 值为 5.08,且无论哪种粘结剂全电池的阻抗值都要比半电池小。5.使用硬
6、碳做负极时电池的倍率性能要好,电池在 1 C 的充放电倍率下进行充放电时,LiFePO4/AGP-3 和 LiFePO4/HC 电池的放电比容量值分别为 0.2 C 倍率下的 84.3%和 91.0%,在 1 C 和 2 C 的放电倍率下,LiFePO4/AGP-3 电池的放电比容量要稍高于 LiFePO4/HC电池,但是当电池的放电倍率为 5 C 和 10 C 时,LiFePO4/HC 电池的放电比容量值却要高于 LiFePO4/AGP-3 电池。6.电池使用硬碳和石墨材料做负极时阻抗值相差不大,LiFePO4/HC 电池的 Rct 值稍小一些。1 C 的放电倍率下,LiFePO4/HC 电
7、池的循环寿命要比LiFePO4/AGP-3 电池长。此外,与正负极材料的半电池相比,在 10 C的放电倍率下,LiFePO4/HC 全电池的循环寿命要远远长于半电池,经过 2450 个循环后电池的放电比容量才降为首次的 60%。【英文摘要】Since lithium ion batteries have been successfully investigated and commercialized, they attract peoples attention for their properties such as long cycling life, high voltage, sec
8、urity, no memory effort. However, the electrochemical performance of lithium ion battery is affinitive with its cathode and anode materials, conductive agent, binder, electrolyte, separator et al. Lithium iron phosphate (LiFePO4) has been considered as a promising lithium ion battery because of its
9、rich raw materials, high capacity, stable structure, safety et al. As well, hard carbon (HC) with an inordinance structure which can be used for an anode material of lithium ion battery has been attracted peoples interest for its high capacity, excellent cycling performance and low cost et al. In th
10、is thesis, we have developed a lithium ion battery-LiFePO4/HC using LiFePO4 as cathode and hard carbon as anode to study the conductive agent and binder influence of the electrochemical properties of LiFePO4/Li half cell and LiFePO4/HC full cell. In addition, we compared the electrochemical performa
11、nce of LiFePO4/HC battery and LiFePO4/graphite (AGP-3). Through the experiments, we got the following conclusions:1. For LiFePO4/Li half cell, using Super P Li as conductive agent, the resistance of battery was smaller. At 0.2 C or 1 C rate, the discharge voltage plateau of the cell using Super P Li
12、 as the conductive agent was more stable than that of using acetylene black. After 150 cycles at 1 C rate, the capacity retention of the cell using Super P Li as conductive agent was higher. Cyclic voltammetry indicated that the LiFePO4 material has a good cyclic reversibility, which may be caused b
13、y the good conductivity results from the carbon fibers among LiFePO4 particles.2. For LiFePO4/HC full cell, we also got the conclusion that using Super P Li as conductive agent, the resistance of the cell was smaller and the capacity of it was higher. Rate performance test has shown that the cell us
14、ing Super P Li as conductive had better rate performance, however, the discharge capacity of the cell was small at 10 C rate neither using Super P Li or acetylene black as conductive agent, which maybe due to the the unsatisfactory bond performance of the PVDF binder. Comparing with the LiFePO4/Li h
15、alf cell, the resistance of the full cell was smaller and the capacity retention was higher after 150 cycles at 1 C rate.3. We have used a water binder (SBR) and an oiliness binder (PVDF) to make LiFePO4 cathode electrode, and assembled with lithium metal composing to LiFePO4Li lithium ion battery.
16、Both of the water-based binder system and the oil-based binder system, the discharge voltage plateau (about 3.38 V) of the cell were stable and the discharge capacity were almostly the same at 0.2 C discharge rate, however, the water-based binder system was a little lower. While at the discharge rat
17、e of 1 C, in the water-based binder system, the first and second discharge capacity of the cell was higher than that of the oil-based binder system. From the results of the EIS and cycle life tests demonstrated that the cell with water-based binder system had a smaller resistance with Rct equates to
18、 89.68and had better capacity retention which was 65% after 150 cycles at 1 C discharge rate.4. We had used two binders to assemble LiFePO4/HC full batteries, the initial discharge capacity of the cell with oil-based binder system was higher than the water-based binder system in the charge-discharge
19、 process at 0.2 C rate. However, as cycles proceed, the discharge capacity of the cell with oil-based binder system was decreased, while, the discharge capacity of the cell with water-based binder system had a little increased. As the same as the results of LiFePO4/Li half cell tests, the discharge
20、capacity of the cell with water-based binder system was higher than the cell with oil-based binder system, and its capacity retention was higher which was 97.9%. Rate performance test indicated that the cell with water-based binder system had a better rate performance. In addition, the water-based b
21、inder system had smaller resistance whose Rct was 5.08, however, whatever the binder we used, the resistance of the LiFePO4/HC full cell was smaller than the LiFePO4/Li half cell.5 The rate performance of the cell using hard carbon as anode was better. When the cells charge-discharge cycling at 1 C
22、rate, the initial discharge capacity of the LiFePO4/AGP-3 and LiFePO4/HC was 84.3% and 91.0% of the discharge capacity at 0.2 C rate. The discharge capacity of LiFePO4/AGP-3 cell was a little higher than LiFePO4/HC cell at 1 C rate or 2 C rate, however, on the contrary, the discharge capacity of LiF
23、ePO4/HC was higher when charge-discharged at 5 C or 10 C rate. 6. The resistance was almost the same when using hard carbon or graphite as anode, and the resistance of LiFePO4/HC was a little lower. The cycle life of LiFePO4/HC cell was longer than that of LiFePO4/HC cell, besides, the cycle life of
24、 the LiFePO4/HC full cell was longer than the LiFePO4/Li and HC/Li half cell, with its discharge capacity retention of 60% after 2450 cycles at 10 C rate.【关键词】锂离子电池 磷酸亚铁锂 硬碳 导电剂 粘结剂【英文关键词】lithium ion battery lithium iron phosphate hard carbon conductive agent binder【目录】磷酸亚铁锂/硬碳锂离子电池的工艺及电化学性能研究 摘要 3-
25、5 ABSTRACT 5-7 第 1 章 绪论 11-39 1.1 引言 11 1.2 锂离子电池的发展历程 11-12 1.3 锂离子电池的结构与工作原理 12-14 1.4 锂离子电池正极材料的研究进展 14-32 1.4.1 锂离子电池正极材料的选择要求 14-15 1.4.2 钴系正极材料 15-17 1.4.3 镍系正极材料 17-19 1.4.4 锰系正极材料 19-22 1.4.5 钒系正极材料 22-23 1.4.6 铁系正极材料 23-32 1.5 锂离子电池负极极材料的研究进展 32-35 1.5.1 碳材料 32-34 1.5.2 金属氧化物 34-35 1.6 锂离子电
26、池导电剂的研究进展 35-36 1.7 锂离子电池粘结剂的研究进展 36-37 1.8 本论文的主要研究目的和内容 37-38 1.9 本论文的创新之处 38-39 第 2 章 实验试剂与方法及原理 39-48 2.1 实验试剂 39-40 2.2 实验主要仪器 40 2.3 电极的制备及电池的组装 40-42 2.3.1 正极的制备 40-41 2.3.2 负极的制备 41 2.3.3 电池的组装 41-42 2.4 物理性能表征 42-44 2.4.1 扫描电子显微镜分析 42-43 2.4.2 透射电子显微镜分析 43 2.4.3 X 射线衍射测试 43 2.4.4 粒径分析 43-44
27、 2.5 电化学性能测试 44-48 2.5.1 恒流充放电池测试 44-46 2.5.2 循环伏安测试 46-47 2.5.3 交流阻抗测试 47-48 第 3 章 导电剂对 LiFePO_4/Li及 LiFePO_4/HC 电池性能的影响 48-61 3.1 引言 48 3.2 极片的制备及电池的组装 48-49 3.2.1 负极极片的制备 48 3.2.2 正极极片的制备 48-49 3.2.3 电池的组装 49 3.3 LiFePO_4材料的表征 49-51 3.3.1 扫描电子显微镜分析 49-50 3.3.2 透射电子显微镜分析 50 3.3.3 XRD 测试 50-51 3.4
28、电化学性能测试 51-59 3.4.1 不同导电剂对 LiFePO_4/Li 半电池电化学性能的影响 51-56 3.4.2 不同导电剂对 LiFePO_4/HC 全电池电化学性能的影响 56-59 3.5 本章小结 59-61 第 4 章 粘结剂对 LiFePO_4/Li 及 LiFePO_4/HC 电池性能的影响 61-74 4.1 引言 61 4.2 极片的制备及电池的组装 61-62 4.2.1 负极极片的制备 61-62 4.2.2 正极极片的制备 62 4.2.3 电池的组装 62 4.3 材料的表征 62-63 4.4 电化学性能测试 63-72 4.4.1 不同粘结剂对 LiF
29、ePO_4/Li 半电池电化学性能的影响 63-68 4.4.2 不同粘结剂对 LiFePO_4/HC 全电池电化学性能的影响 68-72 4.5 本章小结 72-74 第 5 章 LiFePO_4/HC 及 LiFePO_4/AGP-3 电池的电化学性能研究 74-85 5.1 引言 74 5.2 材料的表征 74-76 5.2.1 扫描电子显微镜分析 74-75 5.2.2 透射电子显微镜分析 75-76 5.2.3 粒径分析 76 5.3 电化学性能测试 76-83 5.3.1 充放电测试 76-79 5.3.2 循环伏安测试 79-80 5.3.3 交流阻抗测试 80-81 5.3.4 倍率性能测试 81-82 5.3.5 循环寿命测试 82-83 5.4 本章小结 83-85 第 6 章 结论与展望 85-87 6.1 结论 85-86 6.2 展望 86-87 致谢 87-88 参考文献 88-100 攻读学位期间的研究成果 100
