论文总字数：26116字

摘 要

目前，能源危机与环境污染是世界性两大难题，因此，开发新能源结构，寻找可再生的清洁、高效能源迫在眉睫。锂离子电池（LIBs) 由于成本及安全问题在大规模商业应用中受到抑制。而钠具有高储量、低成本，所以钠离子电池（SIBs)获得了高度吸引力，其作为电化学电源，可以满足大型电能储存需求。

但Na （0.102 nm）的半径比Li （0.076 nm)大了约40%，这种固有缺陷导致负极材料成为开发钠离子电池的关键问题之一。目前的主要负极材料集中在碳材料，合金化材料和金属氧化物。SnO₂因其环境友好性和非常低的成本及高理论容量(667 mA h g^-1), 受到特别的关注。然而SnO₂材料在钠离子嵌入和脱出时巨大的体积膨胀和收缩导致其循环寿命差，限制了它的实际应用。目前，提高SnO₂循环性能主要有两种途径，减小SnO₂颗粒尺寸或将SnO₂与碳进行复合。石墨烯(graphene)是近年来研究热点，它具有超高比表面积，高导电性，且化学和机械性能较好，被广泛应用到电极材料中。掺杂氮元素可以提供一定的活性位，加速电极反应的离子传输。

本文通过碳包覆SnO₂与氮掺杂石墨烯进行复合，探究不同氮掺杂量下复合材料的性能。本文首先采用XRD、SEM、TG等表征手段，研究复合材料的组成、形貌及碳含量；然后通过恒流充放电、倍率、循环伏安等方法，测定复合材料的电化学性能。实验结果表明，当尿素掺杂量为6 g时，SnO₂的担载量最高，在100 mA g^-1的电流密度下，首圈放电容量达到955.8 mA h g^-1，循环85圈容量为301.7 mA h g^-1，明显优于3 g和9 g的掺杂量。

关键词：钠离子电池 二氧化锡 石墨烯 负极材料

Preparation and Properties of Carbon-coated SnO₂ /Nitrogen

Doped Graphene Composite Electrode as Sodium-ion Battery Anodes

Abstract

At present, the energy crisis and environmental pollution are two major problems. Therefore, developing new energy structure, and looking for renewable clean, efficient energy are extremely urgent. Lithium-ion batteries (LIBs) were restricted in large-scale commercial application due to their cost and safety issues. Meanwhile, sodium-ion batteries (SIBs) have received wide attention because of sodium high reserves and low cost. So sodium ion battery is a potential electrochemical power supply to meet the needs of large-scale power storage.

However, the radius of Na (0.102 nm) is about 40% greater than that of Li (0.076 nm), which leads that the anode materials for the reversible sodium ion battery become the key issues in the development of sodium ion batteries. In response to this challenge, a wide variety of anode materials have been explored, including various carbonaceous materials, intermetallic compound materials and metal oxides. SnO₂ as a metal oxide, has attracted particular attention for its environmental benign, very low cost, and high theoretical capacity (667 mA h g^-1). However, SnO₂ exhibits relatively poor magnification performance and cycling performance, since the SnO₂ volume expands greatly during the embedding and delamination process, easily causing the electrode active material to fall off. In order to solve this problem, the researchers are constantly trying to study the optimization of tin oxide. At present, there are two main ways to improve the SnO₂ cycle performance, including reducing the size of SnO₂ particles and coating carbon. Graphene is a hot spot in recent years, it has a high specific surface area, high conductivity, and excellent chemical/mechanical properties, so it is widely used in electrode materials. The doping nitrogen element can provide a certain active site to accelerate the ion transport of the electrode.

In this paper, the effect of nitrogen doping content of carbon-coated SnO₂/nitrogen-doped graphene was investigated. The XRD, SEM and TG were used to study the composite, structure, morphology and carbon content. Furthermore, the

electrochemical performance of as-prepared anode materials was characterized by the galvanostatic charge-discharge and cyclic voltammery. When the doping content of urea was 6 g, the single load of SnO₂ is the highest. SnO₂@C/NG composite is able to deliver a high discharge capacity (955.8 mA h g^-1) in the first cycle at a current density of 100 mA g^-1, and deliver a relatively high reversible capacity of 301.7 mA h g^-1 after 85 cycles at 100 mA g^-1, significantly better than 3 g and 9 g doping amount.

Key words: Sodium ion battery; Tin dioxide; Graphene; Anode material

目 录

摘 要 I

Abstract II

第一章 绪论 1

1.1 前言 1

1.2 钠离子电池的工作原理及电池结构 2

1.2.1 钠离子电池的工作原理 2

1.2.2 钠离子电池的电池结构 3

1.3 钠离子电池研究现状 3

1.3.1 钠离子电池正极材料 3

1.3.1.1 过渡金属氧化物 3

1.3.1.2聚阴离子类 3

1.3.1.3普鲁士蓝类 4

1.3.2 钠离子电池负极材料 4

1.3.2.1碳材料 5

1.3.2.2合金材料 6

1.3.2.3金属氧化物 6

1.3.2.4 有机化合物 7

1.4二氧化锡材料研究概况 7

1.5 本文的研究目的和主要工作 9

第二章 实验与表征 14

2.1 实验试剂与仪器 10

2.2 复合材料的制备 11

2.2.1 SnO₂的制备 11

2.2.2 SnO₂@C的制备 12

2.2.3 SnO₂@C/NG的制备 12

2.3 复合材料的表征 12

2.4 电池的制备及组装 13

2.4.1 电极片的制备 13

2.4.2 电池的组装 13

2.5电化学性能测试 13

第三章 结果与讨论 14

3.1 复合材料的表征分析 14

3.1.1 复合材料X射线衍射分析(XRD) 14

3.1.2复合材料微观形貌表征(SEM) 14

3.1.3 复合材料热重分析（TG） 15

3.2 SnO₂@C/NG复合材料电化学性能分析 16

3.2.1电化学过程的分析 16

3.2.2电化学循环及倍率性能分析 16

第四章 结论与展望 20

4.1 结论 20

4.2 展望 20

参考文献 21

致 谢 24

第一章 绪论

1.1 前言

由于能源需求增加，化石燃料价格上涨及环境污染，对环保能源的呼吁日益提高，过去十年来，储能已成为全球日益关注的问题。过去几年的研究已取得许多突破，基于电池的电化学储（EES）技术表现出相当大的前景。它们具有高充放电效率，高能量密度、长循环寿命和低维护成本等优势，可以满足不同的电网功能。特别的，电池代表了可再生资源整合的可行储能技术，其能为电网提供间歇的能源。电池系统的结构使得它们非常适合在微型电网使用，如电动/混合动力电动车辆（EV/HEV）等。

现在，电网储能主要集中在锂离子电池上（LIBs）。锂离子电池作为便携式电子设备和车辆的主要电源，需求正在迅速增长^[1]。预测LIBs将继续成为重要储能系统，市场对锂资源有巨大需求，造成锂价格不断上涨，成本不断提高，所以实现锂电池的大规模储存并不经济。

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