锂离子电池ge基负极材料的制备及其储锂性能研究

全文摘要

作为储能设备的锂离子电池（LIBs）具有能量密度高、功率大、寿命长和环境友好等特点。但市售LIBs石墨负极的理论容量仅有372 mAh g-1，这难以满足能量储存系统的建立、大型电动汽车等发展的要求。负极材料是LIBs的重要组成部分，因而，高容量负极材料的开发成为提高LIBs性能的决定因素。作为锂离子电池负极材料，Ge具有比容量高，操作电压低、电子传输速率快等优势，有望替代石墨负极。但在循环过程中，Ge体积膨胀严重，造成它的循环性能差，阻碍了实际应用。

为了提高Ge负极材料的循环稳定性，研究者提出了纳米结构化和碳材料复合两种方法。具有不同相貌的纳米结构具有表面积大，离子/电子传输快的特点。而碳质材料具有高的导电性、好的机械柔韧性以及热和化学稳定性。在前人工作的基础上，本文开展了以下两方面的内容：

（一）以市售的GeO2、GO和纯水为原料，基于溶解-重结晶的机理制得了GeO2/graphene复合物。复合物制备过程中所用的化学试剂和仪器无毒且便宜。用作LIBs负极材料进行性能测试时，结果表明：该电极具有好的循环性能和高的可逆容量：首次充电容量高达1637 mAh g-1，循环80圈后可逆容量保持在640 mAh g-1。

（二）针对传统1 D纳米结构合成过程复杂、使用贵金属催化剂的缺点，本文通过静电纺丝的方法合成了Ge/CNFs。该材料表现出良好的储锂性能：在100 mA g-1的电流密度下，循环30圈后仍具有643.2 mAh g-1的可逆容量，约为石墨负极的2倍。这主要归因于：（1）多孔结构能够增加电极与电解质的接触面积；（2）Li+较短的扩散距离；（3）电子沿1 D方向快速传输，提高了电极的导电性。

关键词：锂离子电池Ge负极静电纺丝石墨烯

Abstract

Lithium-ion batteries (LIBs), as energy storage devices, have the characteristics of high energy density, high power density, long service life and environmental friendliness. Nevertheless, the graphite anode (372 mAh g-1) has a very low specific capacity, which is unable to fulfil the establishment of energy storage systems as well as the demands of large electric vehicles development. To further improve the performance of LIBs, the attention is then focused on the electrode materials with hig her speciﬁc capacity. As the anode of LIBs, Ge is of great interest since it has higher speciﬁc capacity than

traditional carbon anodes. However, the poor cyclability due to the large volume change of Ge upon insertion/extraction of lithium has been an impediment to its practical application.

In order to improve the cycle stability of the Ge anode materials, strategies for nanostructure and hybridization with carbonaceous material have been proposed. Nanostructure with versatile morphology can provide high surface area, fast lithium and electron transportation. While, carbonaceous material exhibit superior electrical conductivity, good flexibility as well as excellent thermal and chemical stability.

Based on the summary of literature research, the main content of this paper is as follows:

(1) Based on the mechanism of dissolution-recrystallization, a facile green solution route using only GeO2 powder, graphene oxide and puriﬁed water has been developed to prepare a GeO2/graphene composite. It is worth noting that the solvent, reagents, as well as instruments we used in the preparation process of the composites are innocuous and inexpensive. The results of battery performance test show that the synthesis of compound electrode has good cycle performance and reversible capacity. The composite electrode exhibits a high initial reversible charge capacity of 1637 mAh g-1, exhibiting a high charge capacity of 640 mAh g-1 after 80 cycles.

(2) the conventional synthesis of 1 D nanostructures involved the complicated process and the use of expensive catalyst. Here, we report a facile preparation of a

Abstract

Ge/CNFs by electrospinning. In half cell test, Ge/CNFs composite electrode shows a high initial reversible charge capacity of 643.2 mAh g-1 after 30 cycles under the current density of 100 mAh g-1. The excellent electrochemical performance of Ge/CNFs may be ascribed to the following reasons: (1) the porous structure can increase the contact area of the electrode and the electrolyte; (2) the short diffusion distance of Li+; (3) the fast transfer of electron along the direction of one-dimensional, which improved the electrical conductivity of electrode.

Keywords: Lithium-ion battery, Ge anode, electrospinning, graphene

III

全文摘要 .................................................................................................... I Abstract ...................................................................................................... II 目录 .......................................................................................................... I V 第1章绪论 . (6)

1.1 锂离子电池简介 (6)

1.1.1 锂离子电池的发展历史 (6)

1.1.2 锂离子电池的组成及工作原理 (7)

1.2 锂离子电池负极材料 (8)

1.2.1碳负极材料 (8)

1.2.2 Ge基负极材料 (9)

1.3 实验的选题背景和研究内容 (22)

参考文献 (23)

第2章GeO2/graphene复合物的绿合成及储锂性能研究 (31)

2.1 引言 (31)

2.2 实验部分 (32)

2.2.1 材料制备所用化学试剂和仪器 (32)

2.2.2 氧化石墨的制备 (33)

2.2.3 GeO2/graphene复合物的制备 (33)

2.2.4 材料表征 (34)

2.2.5 电化学测试 (34)

2.3 结果与讨论 (34)

2.4 本章小结 (41)

参考文献 (42)

第3章多通道Ge/CNFs的静电纺丝法合成及其储锂性能的研究 (46)

3.1 引言 (46)

3.2 实验部分 (47)

3.2.1 材料制备所用化学药品和仪器 (47)

3.2.2 材料的制备 (48)

3.2.3 材料表征 (48)

3.3.4 电化学测试 (49)

3.3 结果与讨论 (49)

3.4 本章小结 (57)

参考文献 (57)

个人简历、在学期间发表的学术论文与科研成果 (61)

致谢 (62)

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