【作者】 宁静；

【导师】 张进成； Donglei Fan；

【作者基本信息】 西安电子科技大学 ， 微电子学与固体电子学， 2015， 博士

【摘要】 随着经济的高速发展,人类目前面临严重的能源短缺和环境污染。为此,各国积极开展新型能源器件的研发。其中,以超级电容和化学电池为代表的电化学储能器件因其具有超高的能量密度和功率密度、以及超高的循环寿命及转换效率,被认为是最具可行性的清洁能源器件,在国防、医疗以及新兴产业等领域具有广阔的应用前景。作为储能器件的核心部件,电极材料的性能和其结构的改进则是制约新型储能器件应用的关键。目前,商业化的储能器件一般采用含镉、铅的石墨基电极材料,然而这种器件不仅质量重、毒性大、循环效率差,而且电容量和能量密度偏低。因此,研发超高功率及能量密度、超长循环寿命的轻质新型储能器件具有极高的科学研究价值和应用前景。本文旨在研制基于3D多孔石墨烯结构的新型高性能的电极材料及储能器件,着力解决制约超级电容和化学电池等储能器件性能的容量损失、老化、功率及能量密度受限等关键科学问题。通过研制新型的电极材料、结构和储能模块,建立3D石墨烯基集成电极的结构与功能构筑模型,揭示其储能机理及结构性能对其储能性能的影响机制,为新型3D石墨烯多孔石墨烯的储能应用奠定了必要的理论和实验基础。本文所取得的研究成果和创新点如下：1.系统研究了Cu衬底上石墨烯CVD制备的成核机理、缺陷形成与控制机理,重点揭示了Cu衬底预处理、生长温度、气氛比例及气体流量等关键因素对石墨烯质量和性能的影响机制,建立了晶圆级高质量石墨烯的CVD可控生长模型。在此基础上,本文创新性的提出一种基于低压CVD系统的分步调压法高效制备超大晶畴2D单晶石墨烯的方法,并成功制备单晶畴尺寸超过1 mm、载流子迁移率高于6000 cm2/Vs的石墨烯样品(转移至r面蓝宝石衬底),与国际先进水平相当。2.开展了大面积石墨烯的无损转移和改性研究,分析厘清了各类非晶态、多晶态和晶态衬底的晶体类型、表面平整度、亲水性和极性等特性对转移其上的石墨烯性能的作用机制。针对石墨烯器件制备中的退火修复环节后性能退化问题,深入分析了氢气退火处理中各关键因素对石墨烯性能的影响机制,创新性的提出了氢气退火中的表面清洁效应、非故意掺杂效应和结构缺陷等机制的联合作用模型。同时,提出一种新型的自支撑石墨烯无损叠层转移技术,为石墨烯透明导电薄膜应用提供了新思路。3.基于2D石墨烯的CVD成核机制及可控制备机理,结合电化学沉积与极化腐蚀机理及表面修饰效应,创新性的提出了一种基于3D柔性多孔石墨烯的结构和功能模块构筑技术,系统探讨了平衡电位、液相传输、弗莱德电位等因素对多孔化合金基底结构的作用机制,揭示了3D多孔石墨烯(3DMG)的成核机理。采用这项技术,本文成功制备了具有高比表面积、导电性和浸润性的低缺陷3DMG,并研究了该结构作为新型电极材料,在储能器件中的电化学性质。4.采用3D多孔石墨烯与Ni(OH)2结合的复合材料成功制备储能器件的集成电极,并着重研究了该集成电极的高性能储能机理,以及单晶Ni(OH)2的成核质量与形貌结构对集成电极性能的影响机制。研究表明,该集成电极具备优异的电容性能,当基于全电极的质量时,其比容量高达～1149 F/g：在充放电4000次后,其放电量仅降低2.5%；另外,该集成电极还具有优异的电池性能,当电流密度为1.5A/g时,其放电量高达480 mAh/g。以上结果与国际上已经报道的先进水平相当。5.在厘清3D多孔石墨烯高储能机理的基础上,成功制备了3DMG/Mn3O4集成电极,并深入探究了3D石墨烯与Mn3O4的界面特性和晶粒粒度对该集成电极性能的影响机制、3DMG/Mn3O4的表面形貌对该集成电极电容性能的影响机制。并基于微孔及介孔内的质子扩散、电子转移动力学,揭示了微介孔是氧化还原反应时快速扩散的关键因素。同时,针对常规超级电容的工作电压和能量密度较低这个缺陷,成功研制了3DSG/Mn3O4/3DMG的高性能不对称超级电容,其能量密度高达71.4Wh/Kg,功率密度为300 KW/Kg,在经历3000个循环后,电容的损失量仅为10%,为不对称超级电容的储能应用提供了理论和实验基础。更多还原

【Abstract】 With the fast development of the economy, the shortage of energy sources and environmental pollution become the two threats to the human society. Many countries put their efforts to develop the new energy storages. Among them, clean energy technologies, supercapacitors and batteries are the most representative electrochemical energy storage and conversion, which playing the important role in national defense, medical treatment and the new industry because of their extremely high-energy and power densities, superior cycle lifetime and conversion efficiency. As a heart of the energy storage device, the key to expanding its application is to improve the electrode’s performance and structures. At present, the commercial energy storage devices in general are used graphite powder based electrodes containing such as Cr, Li. However, these devices are not only heavy, high toxicity, and poor cycle efficiency, but also quite low energy and power densities. Therefore, high-energy and power densities, long cycle lifetime and light new energy storage device have high research value and application prospect.In this thesis, the novel 3D porous graphene electrode materials and devices are brought forward to solve the mainly problems of energy storage devices, such as the loss of the capacity, aging, the restriction of energy and power densities. By developing the new electrode materials, devices and energy storage module,3D graphene based integrated electrode construction and functional architectures is reported. This work reveals the mechanism of energy storage, and the influence mechanism of its structure to performance to energy storage properties, providing an essential theoretical and experimental basis for the application of new 3D graphene based integrated energy storage device. The main research results and contributions of this thesis are listed as follows:1. Systematic research on graphene on Cu by CVD for the nucleation mechanism, defect formation and control mechanism, and reveal the impact of the key factors such as the Cu pretreatment, the growth temperature, the ratio and flow of the gas on qualities and performance of graphene. On the basis of the model of growth crystal high quality graphene, a novel low pressure CVD method was used to prepare squite large crystal single domain size of 2D graphene over 1 mm, carrier mobility of 6000 cm2/Vs (transferred on r-sapphire), which has achieved the international advanced level.2. A study of the influence mechanism of the nondestructive transferred and modified large size graphene, analyses the various amorphous, polycrystalline and crystal of the substrates, such as crystal type, surface planeness, hydrophobicity and polarity. Moreover, in order to solve the annealing problem of the preparation of the graphene based device, a comprehensive study on the combined effects of hydrogen thermal annealing process on the morphological, structural and electrical properties of transferring graphene is proposed. Finally, a novel self-supporting transfer method was brought to investigate on the electrical and optical properties of the layer-stacked graphene transparent electrodes, achieving smoother surface morphologies than the traditional transfer method, which provides a new approach of graphene in the application of transparent conductive films.3. Based on the nucleation and controlled preparation mechanism of the 2D graphene, an innovative mechanism for the synthesis of 3D multilevel porous graphene superstructures using strategically engineered Cu-Ni catalysts are reported. The as-grown graphene is 3D, multilevel porous, freestanding, and flexible after selective etching of the catalysts and CVD. Then systematically discuss the mechanism of equilibrium potential, liquid phase transmission, Flarch potential to porous alloy substrate construction, reveal the nucleation of 3D porous graphene (3DMG). Overall, the reported mechanism for the synthesis of 3D porous graphene is the first of its kind, which may potentially spur a new paradigm for manufacturing 3D porous graphene materials for an array of energy storage applications.4.3DMG coated with thin nickel hydroxide nanoplates (Ni (OH) 2) was applied as integrated electrodes, and discuss the energy storage properties of its high performance. Then, the influence mechanism of quality and mophynologe of the crystal Ni (OH) 2 was discussed. When these electrodes as supercapacitors, the integrated electrodes offer the capacitance of ～1149 F/g based on total weight of the electrodes. Moreover, when the electrodes as alkaline batteries, a remarkable discharge capacity of 480 mAh/g at a rate of 1.5 A/g. Compared with previous reports, they also exhibit excellent cycling performance with 97.5% capacitance retention after 4000 cycles. The performance above has achieved the international advanced level.5. Based on the energy storage properties of high performance of 3DMG above, 3DMG/Mn3O4 were made as integrated electrodes, and deeply investigated the influence mechanism of 3DMG/Mn3O4 interface characteristics and crystal size to electrode performance. Moreover, the influence mechanism for 3DMG/Mn3O4 mophynologe to capacitive performance was also discussed. The proton diffusion and electron transfer kinetics within the microspores and mesopores reveals the micro mesoporous is a key factor in the redox rapid diffusion. Finally, high performance asymmetric supercapacitor of 3DSG/Mn3O4/3DMG was made in order to improve the work voltage and energy densities. This supercapacitor has a remarkable energy density of 71.4 Wh/Kg, and power density of 300 KW/Kg. It also exhibits cyclability with 90% capacitance retention after 3000 cycles, which providing the basis of theoretical and experimental of the applications asymmetric supercapacitor.更多还原