3D纳米结构铜集流体上锗电极的制备及电化学性能研究

发布时间：2018-04-12 01:03

本文选题：铜集流体 + 锗　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：Ge因为其极高的比容量,被认为是下一代极具前景的锂离子电池负极材料。然而,由于Ge作为锂离子电池负极材料时严重的体积膨胀(370%)容易造成Ge活性物质的损失,使得Ge的比容量急剧下降,不利于电池容量的稳定性保持,故设计出合理的Ge电极以减少Ge在充放电过程中的损失,成为国内外科学家研究的重点,也面临着很大的挑战。具有3D结构的集流体可以为Ge活性物质在充放电过程中的体积膨胀提供缓冲空间,防止Ge出现粉化脱落等优点。因此本论文通过制备特殊形貌铜集流体,构筑3D结构铜集流体,在其上制备锗电极材料,深入研究集流体的结构对构筑的电极材料电化学性能的影响。首先通过用电镀法,制备出枝晶铜集流体,在此集流体上负载锗薄膜,制备三维纳米Cu/Ge电极,对其进行SEM、XRD等分析测试,并以此Cu/Ge电极组装电池测试其储锂性能,与商业用集流体进行比较。结果表明,在C/10倍率下,首次充放电比容量分别为1171.3m Ah/g和1700.6m Ah/g,首次库伦效率为68.88%,经过100次循环后,充放电比容量为821.1m Ah/g与856.1m Ah/g,优于商业用铜集流体材料,同时倍率性能与商业铜集流体相比,也得到了显著提高。采用氢气泡沫法制备了多孔铜集流体,研究多种因素,如电镀时间、铜盐浓度、电极间距对铜集流体孔形貌和结构的影响,得到最佳的工艺参数。在多孔铜集流体上负载Ge薄膜,经过高温退火处理后,得到三维纳米多孔Ge电极,该电极由于其良好的导电性、高比表面积和多孔结构,表现出良好的储锂性能。在C/10倍率下,首次充放电比容量分别为1351.6m Ah/g和1767.5m Ah/g,首次库伦效率达到76.47%,100次循环后,放电比容量保持为1260m Ah/g,表现出优异的循环稳定性。同时在倍率为5C时,比容量达到420.1m Ah/g,具备良好的高倍率性能。以离子液体电沉积方法制备棒状铜集流体,通过研究沉积电位对铜集流体形貌的影响,制备出不同电位下的菜花状铜集流体,并用离子液体电沉积法在铜集流体上负载锗薄膜,设计了耐腐蚀性、稳定性强的棒状与菜花状Cu/Ge电极。通过研究其充放电性能,得出棒状集流体由于没法为Ge在充放电过程中的体积膨胀提供缓冲空间而使得其比容量下降较快,而菜花状集流体,在沉积电压为-1.4V时得到的集流体,在C/10下,首次放电比容量为1776.8m Ah/g,经过100次循环后,比容量依旧为655.6m Ah/g,表现出较好的循环稳定性。
[Abstract]:GE is considered to be a promising cathode material for lithium ion batteries due to its high specific capacity.However, due to the serious volume expansion of GE as anode material for lithium-ion batteries, the loss of GE active substances is easy to be caused, and the specific capacity of GE decreases sharply, which is not conducive to the stability of the battery capacity.Therefore, the design of a reasonable GE electrode to reduce the loss of GE in charge and discharge process has become the focus of scientists at home and abroad, and is also facing a great challenge.The collector with 3D structure can provide buffer space for the volumetric expansion of GE active substances during charge and discharge, and prevent GE from being powdered off.Therefore, in this thesis, 3D structure copper collector was constructed by preparing copper collector with special morphology, on which germanium electrode materials were prepared, and the effect of collector structure on electrochemical properties of the electrode materials was studied in depth.Firstly, dendritic copper collector was prepared by electroplating method, on which germanium thin film was loaded. Three-dimensional nanocrystalline Cu/Ge electrode was prepared, and its lithium storage performance was tested by Cu/Ge electrode assembly battery.Compared with commercial fluid collection.The results show that at C / 10 ratio, the first charge-discharge capacity is 1171.3 Ah/g and 1700.6 m / g, respectively, and the first Coulomb efficiency is 68.88. After 100 cycles, the charge-discharge capacity is 821.1m Ah/g and 856.1 m / g, which is superior to that of commercial copper collector.At the same time, compared with commercial copper collector, the performance of the rate is also significantly improved.Porous copper was prepared by hydrogen foam method. The effects of various factors such as electroplating time, copper salt concentration and electrode spacing on the pore morphology and structure of copper collector were studied. The optimum process parameters were obtained.After high temperature annealing, three dimensional nano-porous GE electrode was obtained on porous copper collector. The electrode exhibits good lithium storage properties due to its good conductivity, high specific surface area and porous structure.At C / 10 ratio, the first charge / discharge specific capacity is 1351.6 m Ah/g and 1767.5 m / g, respectively. After the first Coulomb efficiency reaches 76.47m / 100 cycles, the discharge specific capacity remains 1260 m / g, showing excellent cycle stability.At the same time, the specific capacity is 420.1m Ah. / g when the ratio is 5C, and it has good performance of high rate.The rod copper collector was prepared by ionic liquid electrodeposition. By studying the effect of deposition potential on the morphology of copper collector, the cauliflower copper collector was prepared under different potentials. Germanium thin films were deposited on copper collector by ionic liquid electrodeposition.The rod and cauliflower Cu/Ge electrodes with strong corrosion resistance and stability were designed.By studying its charge-discharge performance, it is concluded that the specific capacity of the rod collector decreases faster because it can not provide buffer space for the volume expansion of GE during the charging and discharging process, while the cauliflower collector is obtained at the deposition voltage of -1.4 V.At C / 10, the specific capacity of the first discharge is 1776.8 m / g. After 100 cycles, the specific capacity is still 655.6 m / g, showing good cyclic stability.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM912

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