兰州大学机构库 >材料与能源学院
硅基复合材料负极的制备及其在锂离子电池中的应用研究
Alternative TitlePreparation of silicon-based composite anodes and their application in lithium-ion batteries
马耀东
Subtype博士
Thesis Advisor贺德衍
2023-08-27
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学博士
Degree Discipline凝聚态物理
Keyword锂离子电池 lithium-ion batteries 硅基负极材料 silicon-based anode material 硅碳复合 silicon-carbon composites 能量密度 energy density 全电池 full cell
Abstract

锂离子电池作为优秀的储能器件势必在“双碳”目标达成中扮演重要的角色。近年来,随着锂离子电池的广泛应用和蓬勃发展,对电池综合性能的要求也在不断提升。因此,急需发展具有更高能量密度、更高功率密度、更高安全性和更长寿命的新型锂离子电池。

作为锂离子电池中的主要组件之一,通过改善负极的电化学性能可以有效提升锂离子电池的性能。硅材料因具有极高的储锂比容量、丰富的资源和绿色环保等优点,作为锂离子电池的负极材料应用潜力巨大。然而,硅材料在电化学嵌锂反应中会产生显著的体积膨胀,严重阻碍了它在实际中的应用。为此,在目前产业化的硅碳负极中,硅的质量占比较低,相应的电极容量也较低,并且生产成本高于传统负极。

为了改善硅基复合材料的电化学性能,在提高锂离子电池能量密度的同时,尽可能的降低生产成本,需要对硅基复合材料自身、材料合成制备方法、活性材料配比、电极制备工艺等进行深入研究。

在本论文中,作者尝试通过优化活性材料的配比、电极制备工艺、硅基复合材料制备工艺等提高硅基负极的电化学性能,研究了所制备的硅基负极材料在锂离子电池中的应用。论文的主要内容和获得的结果如下:

1. 制备了多孔碳包覆的硅纳米颗粒,研究了与商用石墨混合组成负极材料。通过调控多孔碳包覆的硅纳米颗粒与商用石墨的质量配比,实现了对所制备Si@PC/G负极比容量的有效控制,减少了高成本活性材料的使用。优化的Si@PC/G负极表现出良好的循环性能,首次库伦效率为82.1%,在1000 mA g-1的电流密度下循环250次后,放电比容量为970.59 mAh g-1。Si@PC/G负极与 LiNi0.8Mn0.1Co0.1O2 正极组装的全电池呈现良好的循环稳定性,在电堆模型下具有较高的体积能量密度。

2. 制备了硅碳“混凝土”结构的无粘结剂硅纳米颗粒负极。硅碳“混凝土”有效结合了电极中的活性材料以及活性材料与集流体,减少了电极材料中非活性体积的占比。所制备的Si@C/G负极表现出良好的循环性能,首次库伦效率为83.4%,在2000 mA g-1的电流密度下循环250次后,放电比容量为983 mAh g-1。Si@C/G负极与LiCoO2正极组装的全电池具有良好的循环稳定性,电堆模型计算的电池能量密度为 940.2 Wh L-1,远高于传统石墨//LiCoO2体系的体积能量密度。

3. 使用商用微米级硅颗粒,采用球磨工艺,并在抗坏血酸辅助下以相对温和的合成方法制备了硅基还原氧化石墨烯泡沫。实验发现,所制备的复合材料中石墨烯片层分布均匀且结构平整,同时具有较低的含氧量。作为锂离子电池负极材料,所构筑的三维导电网络具有良好的电荷输运特性,石墨烯片层能够有效缓冲硅颗粒在充放电循环中的体积膨胀并稳定所形成的固态电解质界面(SEI)膜。优化实验条件所制备的负极,首次库伦效率可达83.3%,在1000 mA g-1的电流密度下循环300次后,可逆比容量为738 mAh g-1。预锂化后的负极与LiNi0.8Mn0.1Co0.1O2正极组装的全电池呈现良好的循环稳定性,电堆模型的体积能量密度可达846.3 Wh L-1

4. 使用硅铝合金原材料和溶胶-凝胶法获得了一种碳包覆的多孔硅微米颗粒。硅微米颗粒中丰富的孔隙可以容纳嵌锂反应时膨胀的体积,碳包覆则有效稳定了所形成的SEI膜,提高了活性材料的导电性,从而使所制备的硅基复合材料具有良好的电化学性能。所制备的代表性负极在1000 mA g-1的电流密度下循环150次后容量保持率达到97.5%,放电比容量为845 mAh g-1。与LiNi0.8Mn0.1Co0.1O2正极组装的全电池呈现良好的循环稳定性,在电堆模型下具有较高的体积能量密度,表明使用价格低廉的原材料,通过一定的修饰可以获得优异的电化学性能。

Other Abstract

Lithium-ion batteries are bound to play an important role in the achievement of the "dual carbon" target as an excellent energy storage device. In recent years, the requirements for the comprehensive performance of batteries are increasing with the wide application and vigorous developments of lithium-ion batteries. Thus, there is an urgent requirement to develop new lithium-ion batteries with higher energy density, higher power density, safety and longer cycle life.

The anode is one of the main components in lithium-ion batteries. The performance of lithium-ion batteries can be effectively promoted by improving the electrochemical performance of the anode. The potential application of silicon in the new-generation lithium-ion batteries is immeasurable because of its extremely high lithium storage capacity, abundant resources and environmental protection. However, silicon exhibits a significant volume expansion during the electrochemical lithiation process, which severely hinders its practical application. Therefore, the weight ratio of silicon and the corresponding electrode capacity of the current industrialized silicon-carbon anode are low, and the production cost is higher than that of the traditional anode.

In order to improve the electrochemical performance of silicon composites, while increasing the energy density of lithium-ion batteries and reducing the production cost as much as possible. It is necessary to carry out a thorough research on the silicon composite materials, the preparation method of material synthesis, the ratio of active material component, and the electrode preparation process.

In this paper, the author attempted to improve the electrochemical performance of silicon-based anodes by optimizing the ratio of active materials and the electrode preparation process, preparation of silicon-based composite materials, and further investigated the application of the as-prepared silicon-based anode materials in lithium-ion batteries. The main contents and results of the paper are as follows:

1. Porous carbon coated silicon nanoparticles were prepared and mixed with commercial graphite as anode materials for research. Controlling the specific capacity of the prepared Si@PC/G anode and reduce the utilization of expensive active material are achieved by regulating the weight ratio of porous carbon coated silicon nanoparticles to commercial graphite. The optimized Si@PC/G anode exhibits a good cycling performance with an initial Coulombic efficiency of 82.1%. After 250 cycles at a current density of 1000 mA g-1, the discharge specific capacity of the anode is 970.59 mAh g-1. The full cell assembled with Si@PC/G anode and LiNi0.8Mn0.1Co0.1O2 cathode shows an excellent cycle stability with a high stack cell energy density.

2. Binder-free silicon nanoparticle anode with a silicon carbon "concrete" structure was prepared. The silicon carbon "concrete" effectively combines the active material in the electrode as well as the active material and the current collector, reducing the proportion of inactive volume in the electrode. The as-prepared Si@C/G anode exhibits a good cycling performance with an initial Coulombic efficiency of 83.4%. After 250 cycles at a current density of 2000 mA g-1, the discharge specific capacity of the electrode is 983 mAh g-1. The full cell assembled with Si@C/G anode and LiCoO2 cathode shows a good cycle stability. The battery energy density calculated by the stack cell model is 940.2 Wh L-1, which is much higher than the volume energy density of the traditional graphite// LiCoO2 system.

3. Silicon-based reduced graphene oxide foam obtained by gentle synthesis with the assistance of ascorbic acid while using the commercial micron-scale silicon particles and the ball mill technology. The obtained reduced graphene oxide layer is flat and distribute uniformly in silicon-based reduced graphene oxide foam which has a low oxygen content according to the experiment results. The three-dimensional conductive network provided by prepared silicon-based reduced graphene oxide foam has a fast charge transport character. At the same time, the uniformly distributed and flat graphene layers can effectively buffer the volume expansion of silicon in the cycles while stabilizing the SEI film. The initial Coulombic efficiency of the anode optimized the experimental conditions is 83.3%. After the 300 cycles at a current density of 1000 mA g-1, the specific capacity of the anode is 738 mAh g-1. The full cell assembled with pre-lithiated anode and LiNi0.8MN0.1Co0.1O2 cathode is also exhibit a good cycle stability with a high stack cell energy density of 846.3 Wh L-1.

4. Carbon coated porous silicon microparticle was obtained using Si-Al alloy raw materials and sol-gel methods. The abundant pores in the silicon microparticles can accommodate the expanded volume during the lithium intercalation reaction, and the coated carbon effectively stabilizes the SEI film while improving the conductivity of the active material, which enables the prepared silicon-based composites to exhibit a good electrochemical performance. The prepared representative anode exhibited a capacity retention rate of 97.5% after 150 cycles at a current density of 1000 mA g-1 with the discharge specific capacity of 845 mAh g-1. The full cell assembled with the LiNi0.8MN0.1Co0.1O2 cathode exhibits a good cycle stability and a high volume energy density under the stack cell model, indicating the excellent electrochemical performance can be obtained through the use of inexpensive raw materials and certain modifications.

Subject Area半导体储能材料与器件
MOST Discipline Catalogue理学 - 物理学 - 凝聚态物理
URL查看原文
Language中文
Other Code262010_120170904921
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/538006
Collection材料与能源学院
Affiliation
兰州大学材料与能源学院
Recommended Citation
GB/T 7714
马耀东. 硅基复合材料负极的制备及其在锂离子电池中的应用研究[D]. 兰州. 兰州大学,2023.
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