摘 要

在过去的几十年里，锂离子电池已经被证明是一种性能极佳的二次电池，但是锂储量有限、价格十分昂贵并且在全球分布不均，这导致了锂离子电池很难作为大规模储能器件获得十分长远的发展。而钠资源丰富，价格相对较低廉，作为锂的一个很好的替代物，引起了人们很大的兴趣对其进行研究。目前对钠离子电池的研究主要集中在负极材料方面，基于现有的较为成熟和完善的锂离子电池技术，人们已经对多种可能适合的钠离子电池负极材料进行了尝试，比如碳基材料、钛基材料、过渡金属氧化物材料、合金材料等，然而由于钠离子半径（1.02Å）相对锂离子半径（0.76Å）要大得多，导致大多数负极材料都存在比容量小、倍率性能低、循环稳定性差等问题。

在此基础上，本文通过对目前常见的负极材料进行分析与比较，选择使用水热法在碳布的分层微纤维上（C）原位生长二氧化锡（SnO₂）纳米晶层，得到无粘合剂的多层纳米复合芯--壳结构材料SnO₂@C，并在此基础上做出了改良--即在材料的外表面再包覆上一层碳层制得C@SnO₂@C，这一材料有效的克服了以往存在于负极材料中的各种问题。在CS310电化学工作站上对电池进行恒电流充放电测试、循环伏安测试和交流阻抗测试，研究材料的电化学性能。结果表明，水热合成法原位生长得到的二氧化锡纳米晶体结构十分整齐的包覆在碳纤维表面，且外表面碳涂层的存在，使得材料中间层金属氧化物如同夹心一般，在充放电过程中容易出现的材料因体积膨胀而导致电池损坏的情况得到了很大的改善，显著提高了材料的比容量、使用寿命和倍率性能。通过比较不同材料的循环性能，在多圈循环后，材料仍然具有一定的容量保持，显示出良好的循环性能。

本实验通过水热合成在具有表面涂层的碳布分层微纤维原位生长二氧化锡纳米晶层，得到C@SnO₂@CC纳米结构复合材料，研究其结构稳定性及电化学储能机理，为钠离子电池负极材料的制备提供部分参考和实验依据，为二氧化锡等金属氧化物在负极材料中的应用提供参照及事实依据，为解决钠离子电池负极材料中存在的各种问题提供一个解决的思路及方法，为钠离子电池的发展与研究做出微薄的贡献。

关键词：钠离子电池；SnO₂@C；水热合成；负极材料

Abstract

Over the past few decades, lithium-ion batteries have been proven to be excellent rechargeable batteries. But as for lithium, the reserves are limited, the price is expensive and the distribution is uneven in the world, which led to the result that lithium-ion battery is difficult to have a very long-term development as a large-scale Energy storage device. However, in the world, the sodium, which is rich in resources, and has a relatively lower price, as an alternative substitute for lithium, has aroused great interest in its research. At present, the research on sodium-ion batteries is mainly focused on the cathode materials. Inspired by the lithium-ion batteries, people have been tried a variety of cathode materials, such as carbon-based materials, titanium-based materials, transition metal oxide materials, alloy materials and so on. However, since the sodium ion radius (1.02 Å) is much larger than the lithium ion radius (0.76Å), most of the cathode materials have some problems such as small specific capacity, low rate capacity and poor cycle stability.

Based on such situations, this article analyzes and compares the often used cathode materials, and then use hydrothermal synthesis method to grow tin dioxide (SnO₂) nanocrystalline layer in situ on the layered microfibers of carbon cloth (CC)，and then get the multilayer nanocomposite core-shell structure material--SnO₂@C. After that, modified on the basis of this, the outer surface of the material is coated with a layer of carbon layer to produce C@SnO₂@C. This material effectively overcomes the problems that existed in the cathode material in the past. On the CS310 electrochemical workstation, the battery was subjected by constant current charge/discharge test, Cyclic Voltammetry test and AC impedance test to study the electrochemical properties of the material. The results show that the structure of tin dioxide nanocrystals obtained by hydrothermal synthesis method is very neatly coated on the surface of carbon fiber, and the presence of carbon coating on the outer surface makes the metal oxide in the middle layer of the material as a sandwich. The process of prone to material due to volume expansion and lead to damage to the battery situation has been greatly improved, which significantly improved the specific capacity, life and rate capacity of the material. By comparing the cyclic properties of different materials, the materials still have certain capacity retention after the multi-turn cycle, which shows good cycle performance.

In this experiment, the tin dioxide nanocrystalline layer was grown in situ on carbon fiber microfibers with surface coating carbon, and the structural stability and electrochemical energy storage mechanism were studied. It provides some reference and experimental basis for the preparation of cathodic materials for sodium ion batteries. It provides reference and factual basis for the application of metal oxides such as tin dioxide in cathode materials. It provides a solution to the problems existing in cathode materials of sodium ion batteries. To make modest contribution for the development and research of sodium-ion batteries .

Key words：Sodium(Na)-ion batteries; SnO₂@C; Hydrothermal synthesis method; Cathode material

目 录

摘 要 III

Abstract IV

目 录 VI

第一章 绪论 1

1.1 钠离子电池负极材料的研究及发展 2

1.1.1 钛基材料 2

1.1.2 碳基材料 2

1.1.3 合金材料 3

1.1.4 金属氧化物 3

1.1.5 复合材料 4

1.2 SnO₂@C纳米材料的性能、应用及完善 4

1.2.1 SnO₂@C纳米材料的结构及性能 4

1.2.2 SnO₂@C纳米材料在钠离子电池中的应用及机理 5

1.2.3 SnO₂@C纳米材料的完善 6

1.3实验方案的研究与意义 7

第二章 实验部分 8

2.1 SnO₂@C纳米材料的制备 8

2.1.1 实验用品 8

2.1.2 负极材料的制备 9

2.2 电化学性能测试及表征 10

2.2.1 扫描电子显微镜（SEM） 10

2.2.2 恒电流充放电测试 10

2.2.3 循环伏安测试 11

2.2.4 交流阻抗测试 11

2.3 实验结果与分析 12

2.3.1扫描电子显微镜（SEM） 12

2.3.2 恒电流充放电测试 12

2.3.3 循环伏安测试 16

2.3.4 交流阻抗测试 17

第三章 实验结论 19

参考文献 20

致谢 22

第一章 绪论

随着夏季温度的逐渐升高，秋冬季节雾霾天气持续时间逐渐变长，环境问题变得越来越显著；再加上波动不断的油价，越来越普及的电动车，制约人类社会可持续发展的两大难题--环境与能源，再次被人们提上了议程。一方面，现存环境问题有很大一部分是由于现有化石能源的大规模使用带来的；另一方面，人类的生存对化石能源等的需求却一点都没有降低。因此，清洁可再生能源的研究与发展就变得至关重要与刻不容缓。然而，目前常见的清洁可再生能源（太阳能、风能、地热能、潮汐能等）却在很大程度上严重依赖储能器件的存储来使用。过去三十多年的研究表明，锂离子电池是一种性能极佳的可循环电池，但是锂离子电池的大规模使用仍然存在一定的阻碍，因为目前地球上已知的锂储量十分有限，而且锂作为一种价格昂贵的金属，无形之中提高了锂离子电池的研究与使用成本，增加了人们的负担，最后，锂金属资源地域分布不均，很难满足人们日渐提升的需求，因此，锂离子电池不利于当作大规模储能器件长期广泛的应用。在此基础上，作为锂离子电池的替代物的钠离子电池应运而生。

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