【作者】 田雷雷；

【导师】 魏贤勇； 庄全超；

【作者基本信息】 中国矿业大学 ， 化学工艺， 2014， 博士

【摘要】 石墨烯基复合材料具有独特的物理化学性质，其在电化学储锂等诸多领域具有极大的应用潜力。精细调控石墨烯基复合材料中不同基元材料的结构、形貌和界面耦合形态，进而优化复合材料电极的导电性、结构稳定性和电极界面性能，对开发高能量密度、大功率密度和循环稳定的新型储锂材料具有重要意义。本论文以石墨烯基复合材料的可控制备与电化学储锂性能为主线，分别从石墨烯材料的储锂机制、石墨烯对过渡金属化合物材料储锂性能的影响、石墨烯基复合材料的调控合成及其电化学性能，以及高含量氮掺杂对石墨烯电化学性能的影响等方面进行了研究。使用电化学阻抗谱（EIS）法系统地研究了石墨烯材料电极的首次阴极极化过程，分析了锂离子嵌入过程中的SEI膜阻抗和电荷传递电阻随电极极化电位的变化。研究表明，石墨烯材料电极表面的SEI膜主要在0.95~0.7V之间形成，石墨烯电极在较低电极电位下的嵌锂反应具有较好的可逆性，测得锂离子在石墨烯材料电极中的电化学嵌入反应的对称因子α为0.446。直接使用氧化石墨烯为原料，采用水热-自组装法制备了石墨烯基纳米Fe2O3复合材料。该复合材料中的石墨烯和Fe2O3纳米晶均具有可逆储锂功能，还会发挥协同储锂效应，贡献额外的储锂容量，从而实现较高的可逆容量、优异的循环性能，复合材料电极在100mA g-1电流密度下的可逆容量为1052mAh g-1，在100周循环过程中的可逆容量始终保持在1000±50mAh g-1，此外，复合材料电极还具有优异的倍率性能。分别使用矿化剂和热处理调控石墨烯基复合材料的结构和形貌，优化复合材料的导电性能、结构稳定性和电极界面性能。研究表明，石墨烯表面负载NiO纳米盘复合材料具有较好的结构稳定性，能有效抑制电极表面SEI膜的破损和反复生成过程，该复合材料电极的可逆转化反应过程分两步进行。石墨烯包裹Cu2+1O/Cu复合材料电极在50mA g1电流密度下的可逆容量438mAh g1，60周的容量保持率为84%；同时也具有优良的倍率性能。采用自下而上法制备了高含量氮掺杂石墨烯，研究了氮掺杂和缺陷结构对石墨烯的电化学性能影响，发现氮掺杂石墨烯的储锂反应在低倍率下兼具锂离子电池和法拉第电容器的特征，在大倍率下为单纯的法拉第电容特征。氮掺杂石墨烯电极100mAg-1电流密度下具的首周可逆容量为832.4mAh g-1，第108周的可逆容量为750.7mAh g-1，电流密度提升到10000mAg-1，可逆容量为333mAh g-1。更多还原

【Abstract】 By virtue of their extraordinary physicochemical properties, graphene-basedcomposites (GBC) have been intensively explored for electrochemical lithium-storageand other applications. Artful control of the structure, morphology, and coupling ofthe units should be a key importance to improve the conductance, structure stability,and electrode interface of the composites, and pave the way to the design andfabrication of novel GBC with high energy, high power density and long life. In thisdissertation, mechanism of lithium storage in graphene nanosheets (GNS), effects ofGNS to the lithium storage performances of transition metal compounds, controlledsynthesis and electrochemical performances of GBC, and effects of nitrogen dopantsto the electrochemical performances of GNS have been investigated.The first cathode polarization of the GNS electrode has been systematicallyinvestigated by using electrochemical impedance spectroscopy. Variations of solidelectrolyte interphase films resistance and charge transfer resistance with the electrodepotential have been studied, relational kinetic parameters of the lithium intercalationin GNS electrode have been calculated.Fe2O3-graphene hybrid materials have been fabricated by a hydrothermal strategy,graphene oxide has been directly utilized without any reduction. In the fabricatedmaterials, both graphene sheets and Fe2O3nanoparticles play roles in lithium storage,moreover, extra capacity could also been given due to the synergetic effect. Enhancedreversible capacity, perfect cycling stability and excellent rate capability have beenachieved accordingly.Appropriate mineralizers and heat processing have been explored respectively totailoring the morphologies and structures of GBC, and consequent improving theconductance, structure stability, and electrode interface performances of thecomposite. Enhanced capacity and superior cycling stability of GBC have beenachieved, effects of morphologies and structures to the lithium storage in GBC havebeen clarified.High concentration nitrogen doped graphene sheets (NGS) have been synthesized,effects of nitrogen dopants and structure defects to the electrochemical performancesof graphene sheets have been investigated. It have been found that the NGS presented a superior lithium storage performance with a hybrid feature of lithium ion batteryand faradic capacitor at a low rate and a faradic capacitor feature at a high rate.更多还原