高性能锂离子电池Si，Ge负极材料的设计与研究
文献类型：学位论文
| 作者 | 张传建 |
| 学位类别 | 博士 |
| 答辩日期 | 2013-06 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 崔光磊 |
| 关键词 | 硅 锗 纳米结构 混合传输材料 锂离子电池 |
| 学位专业 | 化学工程 |
| 中文摘要 | 移动终端市场的爆炸式增长极大地带动了对高能量密度锂离子电池的需求。锂离子电池性能取决于电极材料的结构和性质。在本论文中，我们致力于研究高容量的Si和Ge负极材料，并基于电子和离子的混合传输理论，设计和构建了一系列复合纳米结构。主要研究工作包括以下几方面：(1)采用低成本的SiO2为前驱体，以高温热还原法大量制备了Si@SiOx核壳纳米线。实验结果表明Ti粉仅仅作为还原剂还原SiO2, 球形Si@SiOx核壳纳米颗粒催化了纳米线沿[111]晶向生长。表面的氧化层限制了Si在嵌锂过程中的体积膨胀，同时构建了稳定的界面。基于独特的一维核壳结构，Si@SiOx纳米线表现出了良好的电化学性能。较低的原料成本和简单的制备方法，使Si@SiOx核壳纳米线可以成为一种有前景的锂离子电池负极材料。(2)设计并制备了Ge/Carbon nanotubes/Cu (Ge/CNTs/Cu)弹性电极并在不添加粘结剂和导电剂的条件下应用于锂离子电池。CNTs构成的导电网络实现了电子从Ge活性材料到Cu集流体的快速转移，同时弹性骨架限制了Ge颗粒在嵌锂过程中的体积膨胀，维持了电极结构的完整性。优异的电池性能，温和的制备条件以及新颖的结构，使这种三维弹性电极可以成为一种有潜力的负极材料应用于高能锂离子电池。(3)通过NaBH4的同步还原法，在溶液中制备了Ge/石墨烯复合材料(Ge/G)。添加适量的石墨烯可以使Ge纳米颗粒在石墨烯表面的均匀生长和附着。石墨烯的二维层状结构很好的限制了Ge纳米颗粒的团聚，同时实现了电化学反应过程中电子的快速转移。由于石墨烯导电网络的存在，Ge/G复合材料相对于Ge纳米颗粒显示出了优异的循环和倍率性能。(4)通过氢气气氛下550 ˚C还原在Ti集流体表面沉积的GeO2立方颗粒得到了具有多孔结构的Ge立方颗粒。良好的材料结晶度，多孔结构以及没有氧化层的表面使多孔Ge立方颗粒具有91.8 %的超高首次库伦效率。经过200 mA g-1电流密度下100个充放电循环，电极结构保持良好，实现了能量的稳定输出。高导电性的原位碳包覆层极大的提高了多孔Ge立方颗粒的大电流充放电能力。 |
| 英文摘要 | Mobile terminal devices’ markets are experiencing explosive growth which increases the globe demand for Lithium-ion batteries (LIBs) with high energy density. Battery performances depend on the structure and properties of electrode materials. In this thesis, we focused our attention on Si and Ge anodes with high capacity. Novel nanostructures were designed and constructed based on the concept of mixed conducting theory for electron and ion. The concrete research contents are summarized as follows:(1) Bulk-quantity silicon@silicon oxide core-shell nanowires were explored via a high temperature reduction method from cheap silica precursor. Experimental results reveal that it is the spherical silicon nanoparticles with oxide shell rather than titanium powders that catalyze the nanowires grow along [111] direction. The oxide sheath limits the expansion of Si core during Li insertion and builds a stable interface. The obtained silicon@silicon oxide core-shell nanowires exhibited excellent electrochemical performances which were benefit from the unique core-shell structure. The low cost synthesis routes as well as the outstanding performance endow these silicon@silicon oxide nanowires a promising anode material for high-power Li-ion battery.(2) An elastic Ge/Carbon nanotubes/Cu foam monolith for rechargeable lithium-ion batteries’ anode was designed and fabricated without any polymer binder or additives. It is demonstrated that an enhanced cycle performance can be acquired because conductive Carbon nanotubes (CNTs) accelerate the electron diffusion from Ge active particles to copper foam current collector and elastic CNTs framework buffers the expansion of Ge particles which maintain a well structural integrity. Enhanced performances and mild preparation conditions, as well as the unique electrode structure endow this 3D elastic monolith a promising candidate for anode of high energy lithium batteries.(3) Germanium nanoparticles/graphene composite (Ge/G) was synthesized via a simultaneous reduction in solution by NaBH4. Ge nanoparticles embedded uniformly throughout the graphene surface by adding optimum amount of graphene. The two dimentional graphene layer prevents the aggregation of Ge nanoparticles, as well as realizes the fast electron transfer during electrochemical reaction. The Ge/G composite exhits improved cycling and rate performance compared with bare Ge nanoparticles due to the conductive network suppled by graphene.
(4) Porous Ge cubes were fabricated by reducing its oxide precursor which deposited on a titanium foil under hydrogen atmosphere at 550 ˚C. High crystallinity, porous structure and free of oxide surface are responsible for the ultra high initial coulombic efficiency of 91.8 %. A good electrode mophorlogy which was well-maintained after 100 charge-discharge cycles at a current density of 200 mA g-1 accounts for the stable energy delivery. In-situ carbon layer coated porous Ge cube displays an excellent rate capability due to its conductive sheath. |
| 学科主题 | 仿生能源系统 |
| 语种 | 中文 |
| 公开日期 | 2013-07-13 |
| 源URL | [http://ir.qibebt.ac.cn:8080/handle/337004/1494]  |
| 专题 | 青岛生物能源与过程研究所_仿生能源与储能系统团队 |
| 推荐引用方式 GB/T 7714 | 张传建. 高性能锂离子电池Si，Ge负极材料的设计与研究[D]. 北京. 中国科学院研究生院. 2013. |
入库方式： OAI收割
来源：青岛生物能源与过程研究所
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