论文总字数：28783字

摘 要

随着社会的进步和时代的发展，便携式电子设备逐渐占领了人们的生活。而这种生活的改变源自于锂离子电池，锂离子电池自问世以来就受到了广泛的关注，它的存在为人们的生活提供了极大的便利。但是因为锂的地壳含量极低且成本高而抑制了锂离子电池的发展，所以人们迫切需要开发一种新型储能系统。地壳含量排名第六的钠成为了人们关注的重点，并且其成本低，因此吸引了更多人对钠离子电池进行研究，有望其可以替代锂离子电池成为新一代储能系统。

对于钠离子电池，虽然已经开发了许多正极材料，但一直缺乏综合性能优良的负极材料。在已发现的负极材料中，含碳负极材料具有广阔的应用背景，其中硬碳因为其成本低、制备方便、良好的综合性能等优点，被广泛应用在钠离子电池中。硬碳是无定形的，是由随机堆积的石墨烯层组成的，主要有三部分提供储钠空间，即石墨烯层间、表面缺陷以及封闭孔隙。为了获得性能更为优良的以硬碳为负极材料的钠离子电池，人们通过各种新型制备方法来制备硬碳或者是改变电解质来获得。经过许多人的研究发现，硬碳与醚基电解质具有更好的相容性，因而在本课题中，着重于对比酯基电解质和醚基电解质对硬碳的不同的影响，并且通过对硬碳的典型充放电曲线来判断钠在不同的溶剂中插入硬碳的行为特性。

在本文中，通过组装以硬碳为工作电极，分别以酯基和醚基电解质为电解质的钠半电池来进行电池性能测试。经由电化学工作站进行循环伏安测试和交流阻抗测试，蓝电系统进行循环性能测试和倍率性能测试。通过观察测试所得数据可以看出，硬碳与醚基电解质相容的更好，对比酯基电解质，在醚基电解质中硬碳具有更好的稳定性、循环性能以及倍率性能等。在醚基电解质中在电流密度为1 C下电池经过800次循环后，其首圈可逆容量为267.6 mAh g^-1，并且循环800次后，其容量保持率仍为75.8 %，表明硬碳在醚基电解质具有较高的长循环能力和容量保持率。

硬碳的放电曲线一般分为两部分，高压斜坡区代表钠吸附在硬碳表面缺陷或杂原子上，而低压平台区代表钠插层或者钠填充封闭孔隙。为了判断两种不同溶剂对钠插入硬碳的行为特性的不同，本文主要对比了两种放电曲线的差异。在高电流密度下，在酯基电解质中几乎不存在低压平台区，而醚基电解质仍具有较长的平台区，这表明了在酯基电解质中，钠插入硬碳主要倾向于缺陷位的吸附，而在醚基电解质中则倾向于钠插层或者钠填充封闭孔隙。因此，在醚基电解质中会提供更多的平台容量，有利于提高硬碳的总容量。最后，通过对比阻抗图可以发现，钠在插入硬碳时在表面形成了钝化层，并且在醚基电解质中的钝化层要更薄，更有利于钠的插入。

关键词：钠离子电池 硬碳 醚基电解质 酯基电解质 插层

Sodium Intercalation in Hard Carbon among Different Solvents

Abstract

With the progress of society and the development of the times, portable electronic devices gradually occupy people's lives. The change of life comes from lithium-ion battery, which has been widely concerned since it was born, and its existence provides great convenience for people's life. However, because of the low content in the earth's crust and high cost of lithium, the development of lithium-ion batteries is restrained. So people urgently need to develop a new energy storage system. Sodium, the sixth largest in the earth's crust, has become the focus of people's attention, and its cost is low. Therefore, more and more people are attracted to study the sodium ion battery, which is expected to replace the lithium ion battery as a new generation of energy storage system.

Although many cathode materials have been developed for sodium ion batteries, there is a lack of anode materials with excellent comprehensive performance. Among the discovered anode materials, carbon containing anode materials have a wide application background, among which hard carbon is widely used in sodium ion batteries because of its low cost, convenient preparation, good comprehensive performance and other advantages. Hard carbon is amorphous and consists of randomly stacked graphene layers, in which three sites are provided for sodium to store, i.e. graphene interlayer, surface defects and closed pores. In order to obtain a better performance sodium ion battery with hard carbon as the anode material, people use various new preparation methods to prepare hard carbon or change the electrolyte to obtain it. Through many people's researches, it is found that hard carbon and ether based electrolyte have better compatibility, so in this topic, we focus on comparing the different effects of ester based electrolyte and ether based electrolyte on hard carbon, and judge the behavior characteristics of sodium inserting hard carbon in different solvents through the typical charge discharge curve of hard carbon.

In this paper, we assembled the sodium half cells with hard carbon as working electrode and ester or ether as electrolyte to test the performance. Cyclic voltammetry and AC impedance tests were carried out by electrochemical workstation, and cyclic and rate performance tests were carried out by LAND system. It can be seen from the test data that hard carbon is better compatible with the ether based electrolyte. Compared with the ester based electrolyte, hard carbon has better stability, cycle and rate performance in the ether based electrolyte. After 800 cycles at current density of 1 C, the reversible capacity of the battery is 267.6 mAh g^-1 in the first cycle, and after 800 cycles, the capacity retention rate is still 75.8 %, which sheds light on that hard carbon in the ether electrolyte has excellent long cycle performance and high capacity retention.

The discharge curve of hard carbon is generally divided into two parts. The high-pressure slope area represents sodium adsorbed on the defects or heteroatoms of hard carbon, while the low-pressure platform area represents sodium intercalation or sodium filled sealed pores. In order to distinguish the difference of the behavior of sodium intercalation into hard carbon between two different solvents, this paper mainly compares the difference of the two discharge curves. At high current density, there is almost no low-pressure plateau in the ester based electrolyte, but the ether based electrolyte still has a long plateau, which shows that in the ester based electrolyte, the sodium inserted into hard carbon tends to adsorption at the defect site, while it tends to sodium intercalation or sodium filled sealed pores in the ether based electrolyte. Therefore, more platform capacity will be provided in the ether based electrolyte, which is conducive to improving the total capacity of hard carbon. Finally, it can be found that the passivation layer is formed on the surface when sodium is inserted into the hard carbon, and the passivation layer in the ether based electrolyte is thinner, which is more conducive to the insertion of sodium.

Key Words: Sodium ion battery; Hard carbon; Ether; Ester; Intercalation

目 录

摘 要 I

ABSTRACT III

1.1 引言 1

1.1.1 锂离子电池的发展 1

1.1.2 钠离子电池的正负极材料 1

1.2 硬碳的性质 2

1.2.1 硬碳的结构 2

1.2.2 硬碳的插入特性 3

1.3 常用电解质的性质 3

1.3.1 电解质的分类 3

1.3.2固体电解质界面（SEI） 4

1.3.3电解质的作用比较 4

1.4 本文研究内容 5

第二章 实验材料与方法 7

2.1 实验原料 7

2.2 实验器材 7

2.3 实验方法与步骤 8

2.3.1 硬碳制备 8

2.3.2 电池组装 8

2.4 分析方法 8

2.4.1 硬碳材料 8

2.4.2 电池性能测试 9

第三章 讨论与分析 11

3.1 硬碳的表征 11

3.2 不同电解质中硬碳的储钠性能对比 11

3.3 不同电解质中硬碳的储钠机制分析 14

3.4 不同电解质中固体电解质界面（SEI）对比 16

3.5 本章小结 17

第四章 结论与展望 18

4.1 结论 18

4.2 展望 18

4.2.1 不同的盐对钠插入硬碳是否有影响？ 18

4.2.2 钠在插入硬碳时是以什么形式插入？ 18

参考文献 20

致谢 24

第一章 绪论

1.1 引言

1.1.1 锂离子电池的发展

随着改革步伐的加快，社会快速发展，我国的化石燃料消耗量近年来不断增加，其造成的环境污染等问题也日益加剧。为推进生态文明建设，寻找一种绿色、环保、可再生的新能源势在必行，相信在将来多种新能源耦合工作系统会成为发展的趋势。为适应新型的供能系统，电力储存装置也需要进行更新换代，具有理论能量密度高、循环寿命长等优点的锂离子电池有望成为最具竞争力的储能系统之一。自1991年索尼（Sony）采用古迪纳夫理论将锂离子电池正式投入使用以来，人们便开始对其进行了大量的研究^[1]。因为锂离子电池的出现，才会诞生智能手机、平板电脑和笔记本电脑等存在在人们日常生活每一处的便携电子设备，才会有苹果、三星和特斯拉等公司的建立，由此可以看出，锂离子电池对现代人类社会发展做出了巨大的贡献。

请支付后下载全文，论文总字数：28783字