离子液体电沉积锗基材料及其电化学性能研究

发布时间：2018-01-13 22:20

本文关键词：离子液体电沉积锗基材料及其电化学性能研究　出处：《哈尔滨工业大学》2017年博士论文　论文类型：学位论文

【摘要】：锗基材料由于其优异的电化学性能被认为是锂离子电池负极材料的理想选择之一。但是,在电池充放电过程中,锗基材料巨大的体积膨胀会导致电极粉化、剥落,严重影响电池的循环性能。同时,锗的传统制备方法存在着高能耗、高污染等问题。本文以缓解锗基材料的粉化问题,提高材料的循环稳定性为目的,设计出不同形貌的锗基材料及锗基复合材料,包括:锗纳米薄膜、锗纳米线、三维泡沫镍-锗、三维锗-镍纳米圆锥阵列、三维锗-碳材料、锗/碳纳米管复合材料、锗/石墨烯复合材料及锗/聚3,4-乙撑二氧噻吩(PEDOT)复合材料。并采用离子液体电沉积实现对各种锗基材料的高效、绿色、低能、无催化剂及粘结剂制备,研究锗离子在离子液体电沉积的电化学过程,探讨微纳米结构与性能之间潜在的关系和规律。通过离子液体电沉积在室温条件下制备锗薄膜,在沉积过程中通过水含量控制目标产物的形貌,使用未蒸馏的[BMIm]TFSA(水含量96 ppm)沉积可以得到二维多孔锗薄膜,而使用蒸馏后的[BMIm]TFSA(水含量2 ppm)沉积可得到三维多孔锗薄膜。在离子液体电沉积过程中,通过模板辅助法制备出3DOM Ge薄膜。对比热蒸镀法和溶剂热法,体现离子液体电沉积在制备锗基材料上的优势。通过调节工艺参数实现锗基材料的低能耗、高效率、无催化剂制备。利用离子液体电沉积制备多孔锗薄膜,并通过循环伏安及电流-时间曲线等电化学手段研究锗离子在[EMIm]Tf2N中的电化学过程及成核机理。发现沉积多孔锗薄膜的最佳工艺条件为:电解液为1.5 mol/L Al Cl3+0.1 mol/L GeCl4/[EMIm]Tf2N,沉积电势为-1.3~-1.4 V,电解液温度为室温或60 oC。在1.5 mol/L Al Cl3+0.1 mol/L Ge Cl4/[EMIm]Tf2N体系中,锗离子在镍基底上的电沉积过程是受扩散步骤控制的不可逆电极过程,锗离子的成核过程与三维连续成核生长机制相符。通过退火多孔锗薄膜制备出不依靠模板且无催化剂离子的锗纳米线,在退火过程中,锗粒子遵循Lifshitz-Slyozov-Wagner理论进行晶粒熟化及重新生长,随着退火温度的升高,锗纳米粒子逐渐聚集形成多孔锗岛,最终形成锗纳米线。锗纳米线电极具有优异的循环稳定性能及倍率性能,其在0.1 C(1 C=1600 m A/g)倍率下,循环200次后的可逆容量可达1200 m Ah/g,首次库伦效率可达81.3%,5 C倍率下的放电比容量为620 m Ah/g。利用离子液体电沉积将锗沉积在不同形貌的三维集流体上,制备出三维锗电极并研究测试其电化学性能。三维结构可以为活性物质锗提供足够的体积膨胀空间,提高锗电极的循环稳定性,制备出的三维锗电极(泡沫镍-锗)在0.1 C倍率下循环100次后其放电比容量可以达到871 m Ah/g,自支撑三维锗电极(锗-镍纳米圆锥阵列)循环100次后的可逆容量为500 m Ah/g。三维电极的倍率性能也较二维锗电极有显著提升,尤其在5 C倍率下,三维电极的放电比容量均大于200 m Ah/g,而二维电极的放电比容量还不足100 m Ah/g。利用碳的韧性缓冲锗在充放电过程中的体积膨胀,制备出三维锗碳电极并测试其电化学性能。三维锗碳电极在循环100次后的放电比容量可维持在924 m Ah/g,在5 C倍率下的可逆容量为514 m Ah/g。利用离子液体电沉积制备出锗/碳纳米管、锗/石墨烯及锗/聚3,4-乙撑二氧噻吩(PEDOT)复合材料。锗/碳纳米管复合材料在第200次循环后其放电比容量仍可达到851 m Ah/g。在高倍率5 C条件下循环,其放电比容量为880 m Ah/g。其优异的电化学性能主要是取决于复合材料自身的三维多孔结构及碳纳米管的高导电性。利用离子液体电沉积制备出自支撑锗/石墨烯复合材料。该材料在第200次循环后其放电比容量仍可达到1213 m Ah/g。在高倍率5 C条件下循环,其放电比容量为540 m Ah/g。该材料优异的电化学性能与石墨烯优异的导电特性密不可分。利用离子液体电沉积制备出PEDOT薄膜,并利用二次离子液体电沉积制备出锗/PEDOT复合材料,由于PEDOT薄膜的诱导作用,促使锗在其上生长为花状分级结构,为锗的体积膨胀预留出足够空间。该材料在循环200次后,其放电比容量可达到1329 m Ah/g,在高倍率5 C条件下循环,其放电比容量为1137 m Ah/g。
[Abstract]:Germanium based materials due to its excellent electrochemical performance is considered to be one of the ideal choice of anode materials for lithium ion batteries. However, in the battery charge and discharge process, the volume of germanium based materials will lead to a huge expansion of the electrode powder, peeling, serious impact on the cycle performance of the battery. At the same time, the traditional method of preparation of germanium are high energy consumption, high pollution and other issues. In this paper, in order to ease the pulverization of germanium based materials, improve the cycle stability of the material for the purpose of design of germanium based material and germanium based composite materials with different morphologies, including: germanium films, germanium nanowires, three-dimensional nickel foam germanium, germanium three-dimensional nickel nanocones. Three dimensional germanium carbon materials, germanium / carbon nanotube composite materials, germanium and germanium / graphene composite 3,4- / poly ethylene oxygen two thiophene (PEDOT) composite materials. And the ionic liquid electrodeposition to achieve high efficiency, the germanium based materials of green, low energy, no hurry Agent and binder preparation, electrochemical process of germanium ions in ionic liquid deposition, discussion between micro structure and properties of nano potential relations and laws. Through ionic liquid deposition at room temperature in the preparation of germanium thin film deposition process by morphology, controlling the water content of the target products, not using distillation [BMIm]TFSA (water content 96 ppm) deposition can obtain two-dimensional porous SiGe thin films, and the use of [BMIm]TFSA (distilled water content 2 ppm) deposition can get three-dimensional porous SiGe thin films. In the process of electro deposition in ionic liquids by template assisted preparation of 3DOM Ge films. Compared the thermal evaporation method and solvothermal method, reflect the ionic liquid electrodeposition preparation of germanium based material advantages in the system. By adjusting the process parameters to achieve low power consumption, high efficiency of germanium based materials, catalyst preparation. The ionic liquid prepared by electrodeposition of porous SiGe thin films, and And the mechanism of nucleation after cyclic voltammetry and current time curves of germanium ions in [EMIm]Tf2N electrochemical method in electrochemical process. The optimum process conditions that deposited porous germanium film as electrolyte of 1.5 mol/L Al Cl3+0.1: -1.3~ mol/L GeCl4/[EMIm]Tf2N -1.4 V, deposition potential, electrolyte at room temperature or 60 oC. in 1.5 mol/L Al Cl3+0.1 mol/L Ge Cl4/[EMIm]Tf2N system, the electrodeposition process of germanium ions in the nickel substrate is controlled by the diffusion process of irreversible electrode process, germanium ion and three-dimensional nucleation process continuous nucleation and growth mechanism of match. By annealing porous germanium thin film prepared without template and catalyst free ions in germanium nanowires in the annealing process, the germanium particles follow the Lifshitz-Slyozov-Wagner theory of grain maturation and re growth, with the increase of annealing temperature, germanium nanoparticles gradually gathered into shape Ge hole Island, and ultimately the formation of germanium nanowires. Germanium nanowire electrode with cyclic stability and excellent rate performance, the 0.1 C (1 C=1600 m A/g), reversible capacity of up to 200 cycles after 1200 m Ah/g, the first Kulun efficiency up to 81.3%, 5 at C rate discharge capacity 620 m Ah/g. using ionic liquid electro deposition of germanium deposited 3D collector in different morphologies, prepare3-d germanium electrode and its electrochemical performance test research. The three-dimensional structure can provide enough space for the volume expansion of active substances to improve the cycle stability of germanium, germanium electrode, three-dimensional germanium electrode prepared (foam Ni GE) cycle at a rate of 0.1 C after 100 cycles the discharge capacity can reach 871 m Ah/g, free-standing three-dimensional germanium (GE electrode nickel nanocones) reversible capacity after 100 cycles for 500 m Ah/g. ratio can also be compared with two-dimensional three-dimensional electrode Germanium electrode has significantly improved, especially at a rate of 5 C, the discharge specific capacity of the three-dimensional electrode was more than 200 m Ah/g, and the discharge capacity than the two-dimensional electrode is less than 100 m Ah/g. using carbon germanium toughness buffer in the process of charge and discharge volume expansion prepare3-d germanium carbon electrodes and its electrochemical test the performance of carbon electrode in three-dimensional germanium. After 100 cycles the capacity can be maintained at 924 m Ah/g, the reversible capacity at a rate of 5 C for 514 m Ah/g. using ionic liquid prepared by electrodeposition from germanium / carbon nanotubes, germanium and germanium / graphene / poly ethylene 3,4- two oxygen thiophene (PEDOT) composite materials. The germanium / carbon nanotube composite material after 200th cycles the discharge capacity can reach 851 m Ah/g. cycle in high rate under the condition of 5 C, the discharge capacity was 880 m Ah/g. for its excellent electrochemical performance mainly depends on the three-dimensional porous structure of composite materials and their The high conductivity of carbon nanotubes. The ionic liquid prepared by electrodeposition from supporting Ge / graphene composites. The materials after 200th cycles the discharge capacity can reach 1213 m Ah/g. cycle in high rate under the condition of 5 C, the discharge capacity of conductive properties and electrochemistry properties of the graphene material with excellent 540 m Ah/g. excellent inseparable. PEDOT films were prepared by ionic liquid electrodeposition, and the use of the two ionic liquids were prepared by electro deposition of Ge /PEDOT composites, due to the induced effect of PEDOT film on the growth, prompted the germanium flower like hierarchical structure, as the germanium volume expansion set aside enough space. In the material after 200 cycles, the discharge capacity can reach 1329 m Ah/g, circulating in the high rate under the condition of 5 C, the discharge capacity of 1137 m Ah/g.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM912;O646

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