【作者】 刘越；

【导师】 苏冬； 单丹；

【作者基本信息】 天津大学 ， 材料工程， 2019， 硕士

【摘要】 柔性超级电容器具有高功率密度、快速充放电、循环寿命长等优点,能够满足未来柔性电子器件的快速发展需求。二维石墨烯（rGO）膜,作为最有潜力与高容量的双金属硫化物复合的材料,能进一步提高容量。但是,在组装过程中rGO纳米片会发生自堆叠,形成致密的层结构,影响了电解液离子的扩散,进而影响了其电化学性能。本论文从调控双金属硫化物的形貌和构建三维框架结构出发,设计并制备具有疏松层状结构的双金属硫化物/石墨烯复合膜电极,研究了其组装过程、形貌结构和电化学性能,并应用于柔性非对称超级电容器。采用水热法并改变反应条件调控NiCo₂S₄的微观形貌,获得纳米球、纳米片和纳米管三种结构的NiCo₂S₄,并通过真空抽滤法与rGO复合,得到NiCo₂S₄/rGO复合膜,其中NiCo₂S₄纳米管的独特中空结构最适合组装复合膜。研究了NiCo₂S₄-NT@rGO复合膜的形貌结构及其电化学性能,在电流密度为1 A/g时比容量为771.4 F/g。优良的电化学性能来自于管状结构的大比表面积,中空的结构和插入rGO之间后形成的孔道,有利于离子/电子的快速传输。采用水热反应和冷冻干燥法制备的三维NiCo₂S₄@rGO框架,再通过真空抽滤法构建形成NiCo₂S₄@rGO/rGO复合膜。复合膜具有疏松的层状结构,有利于离子的自由扩散并为电子提供了快速传输的通道,这种结构来自空间位阻效应和三维框架结构的支撑作用。复合膜展现了高比容量、优异的倍率性能和循环稳定性,在电流密度为1 A/g时,比容量可达1100 F/g,电流密度扩大十倍后,容量保留率为89.1%,并且5000次充放电循环后容量保留率为90.2%。采用相同的以rGO基三维框架结构组装复合膜的思路成功制备得到Zn-Co-S@rGO/rGO和Mn-Co-S@rGO/rGO复合膜。研究表明,这两种复合膜都具有疏松的层状结构,以及优异的电化学性能（在电流密度为1 A/g时,比容量分别为1005.0和977.8 F/g）。以NiCo₂S₄@rGO/rGO复合膜作为正极,rGO膜为负极组装成柔性非对称超级电容器,能够使绿色LED灯发光,其最大工作电压可达1.8 V,在857.6 W/kg的高功率密度下具有30.0 Wh/kg的高能量密度。更多还原

【Abstract】 The rapid development of future flexible electronic devices has called for ever-growing demands for flexible supercapacitors with high power density,fast charging-discharging rate and long cycle life.Two-dimensional reduced graphene oxide（rGO）film,as one of the most promising materials,can be combined with bimetallic sulfide to further improve capacity performance.However,the rGO nanosheets will self-stack in assembly process,leading to a compact layered structure,which affects the diffusion of electrolyte ions,further affects the electrochemical performance.In this paper,we designed and prepared a loose layered bimetallic sulfide/rGO film electrode by controlling the morphology of bimetallic sulfides and constructing three-dimensional framework structure,and studied the assembly process,morphology structure and electrochemical performance,as well as applied to flexible asymmetric supercapacitors.NiCo₂S₄with different morphology structure（i.e.,nanoparticle,nanosheet,nanotube）were prepared by hydrothermal process through changing the reaction conditions,and assembled to NiCo₂S₄/rGO films with rGO through vacuum filtration.NiCo₂S₄nanotubes with unique hollow structure become one of the most suitable materials to assemble rGO-based hybrid film.The morphology structure and electrochemical performance of NiCo₂S₄-NT@rGO film were studied.The hybrid film exhibits high specific capacitance of 771.4 F/g at the current density of 1 A/g.The good electrochemical performance come from the tube-like structure with large specific surface area,and the channels formed from the hollow structure of the tubes and the intercalation into rGO,which facilitate the ions/electrons transport.NiCo₂S₄@rGO/rGO film constructed by three-dimensional NiCo₂S₄@rGO frameworks was prepared through the hydrothermal process,freeze-drying and vacuum filtration.The hybrid film possesses a loose layered structure due to the steric effect and the support of rGO-based three-dimensional framework structure,which facilitate the free diffusion of electrolyte ions and provide the fast transmission channels for electrons,and exhibiting a high specific capacitance of 1100.0 F/g at 1 A/g,a good rate performance of 89.1%capacity retention at 10 A/g coupled with long cycling stability of 90.2%after 5000 cycles.Zn-Co-S@rGO/rGO and Mn-Co-S@rGO/rGO film were successfully prepared through the same idea of assembling a hybrid film from rGO-based three-dimensional framework structure.Our studies show that both films possess the loose layered structure and excellent electrochemical performance（1005.0 and 977.8 F/g at 1 A/g）.A flexible asymmetric supercapacitor assembled using the NiCo₂S₄@rGO/rGO film as cathode and the rGO film as anode can light up a group of green LEDs,and shows a high energy density of 30.0 Wh/kg at a power density of 857.6 W/kg at an extended operating voltage of 1.8 V.更多还原