钒酸盐纳米线阵列电极设计及其储锂性能研究

发布时间：2018-03-02 10:23

本文关键词： 钒酸钠钒酸铁钒酸锂钒酸钾纳米线锂离子电池　出处：《武汉纺织大学》2017年硕士论文　论文类型：学位论文

【摘要】：化石燃料的使用造成环境污染及资源日渐枯竭,锂离子电池具有能量密度高,循环使用寿命长等优点是解决当今能源问题的有效途径之一。钒氧化物纳米材料是典型的层状物,其开放结构可以使锂离子嵌入电极材料内。然而,钒氧化物的缺陷是导电率低,在充放电时结构不稳定,将其与碳质材料复合或引入金属离子能显著的改善上述问题。本论文围绕钒酸盐纳米材料,采用一步溶液热法和后续煅烧处理成功制备了钒酸钠(Na_5V_(12)O_(32))纳米线阵列,钒酸铁(Fe_(0.12)V_2O_5)纳米线阵列,钒酸锂-还原石墨烯(Li_(0.04)V_2O_5@rGO)纳米复合物,钒酸钾(KVO)纳米线阵列,并研究了其储锂性能。Na_5V_(12)O_(32)纳米线的结构和形貌分别采用XRD,SEM,TEM进行表征,纳米线的长度约为10.5μm。该纳米线阵列具有高比表面积且直接生长在作为集流体的钛片上,能有效的提高锂离子迁移速率。本文对比了不同反应时间和不同煅烧温度下制备产物的电化学性能,反应时间为1 h,煅烧温度为250oC的样品电化学性能最优。其作为正极材料在电压范围2.0-4.0 V,电流密度为50 mA g-1时的首次放电比容量为339 mAh g-1经过50次充放电循环后放电比容量仍为289 mAh g-1,容量保持率为85%。对制备的Fe_(0.12)V_2O_5进行SEM,TEM表征,其纳米线直径约为30 nm,长度为几个微米并为多孔结构。改变反应时间制备的样品形貌不同,本论文提出了相应的生长机理。Fe_(0.12)V_2O_5作为锂离子电池正极材料时,在电压范围2.0-3.6 V,电流密度30 mA g-1经过100次充放电循环后放电比容量为278 mAh g-1,容量保持率为89%。当充放电电压范围扩大为1.0-4.0 V时,在电流密度为500 mA g-1下,经过500次充放电循环后放电比容量仍为289 mAh g-1。Li_(0.04)V_2O_5@rGO纳米复合物中Li0.05V2O5纳米线分散在还原石墨烯上,由于这种独特结构,Li_(0.04)V_2O_5@rGO纳米复合物具有优良的倍率性能和循环稳定性。Li_(0.04)V_2O_5与rGO复合前后电荷转移电阻由178?降为81?。在电流密度为100 mA g-1时,可逆放电比容量为738 mAh g-1,经过500次充放电循环后放电比容量仍有731 mAh g-1。生长在钛网上的KVO纳米线的形貌,晶型结构和组分分别通过SEM,TEM,XRD,XPS进行表征。该柔性电极经过300次充放电循环后,其放电比容量仍高达270 mAh g-1。此外,该电极材料具有优良的倍率性能,当电流密度为960 mA g-1时,放电比容量为214mAh g-1。
[Abstract]:The use of fossil fuels causes environmental pollution and resource depletion. Lithium ion batteries have the advantages of high energy density and long cycle life. Vanadium oxide nanomaterials are typical layers. The open structure allows lithium ions to be embedded in the electrode material. However, the defect of vanadium oxide is its low conductivity and unstable structure during charge and discharge. Compounding it with carbon materials or introducing metal ions can significantly improve the above problems. In this paper, a one-step solution thermal method and a subsequent calcination process were used to prepare a sodium vanadate Na _ 5V _ T _ 12 / O _ (32) wire array around vanadate nanomaterials. The structure and morphology of the nanowires were characterized by XRD- SEMTEM. The structure and morphology of the nanowire arrays of Fex 0.12V _ 2O _ 5), lithium vanadate-reductive graphene (Li) 0.04 / V _ 2O _ 5r GOA nanocomposites, potassium vanadate / KVOO _ 2 nanowire arrays, and the lithium storage properties of the nanowires, Na _ 5V _ (12) O _ 2O _ 32) nanowires were characterized by XRD- SEMTEM, respectively. The nanowires are about 10.5 渭 m in length. The nanowire array has a high specific surface area and is grown directly on a titanium chip as a fluid collector. The electrochemical properties of the prepared products at different reaction time and calcination temperature were compared. When the reaction time is 1 h and the calcination temperature is 250oC, the electrochemical performance of the sample is optimal. The initial discharge specific capacity of the sample is 339 mAh g ~ (-1) after 50 cycles of charge and discharge when it is used as cathode material in the voltage range of 2.0-4.0 V and the current density of 50 Ma g ~ (-1). The electrical specific capacity is still 289 mAh g-1, and the capacity retention is 85. The Fe_(0.12)V_2O_5 prepared is characterized by SEM. The diameter of nanowires is about 30 nm, the length of nanowires is several microns and the structure is porous. The morphology of the samples prepared by changing the reaction time is different. In this paper, the corresponding growth mechanism. In the voltage range of 2.0-3.6 V, the specific discharge capacity of 30mAg-1 is 278mAg-1 after 100 cycles of charge and discharge, and the capacity retention is 890.When the voltage range of charge and discharge is expanded to 1.0-4.0 V, when the current density is 500mAg-1, the discharge specific capacity is 278mAg-1. After 500 charge-discharge cycles, the specific discharge capacity of the Li0.05V2O5 nanowires was still 289 mAh g-1. 1. The Li0.05V2O5 nanowires were dispersed on the reduced graphene in the V _ 2O _ 5R _ go nanocomposites. Because of this unique structure, the Litix 0.04 / V _ 2O-V _ 2O-V _ 2O _ 5C nanocomposite has excellent scaling performance and cyclic stability. Liji _ (0.04) / V _ 2O _ (5) has a charge-transfer resistance from 178 to 178 before and after the combination of the rGO and the Liji _ (0.04) V _ 2O _ (5). Down to 81? When the current density is 100mAg ~ (-1), the specific capacity of reversible discharge is 738 mAh g ~ (-1). After 500 cycles, the specific discharge capacity is still 731 mAh g ~ (-1). The morphology of KVO nanowires grown on titanium mesh is observed. The crystal structure and composition were characterized by SEMMOTEMX RDX XPS. The specific discharge capacity of the flexible electrode was still as high as 270 mAh g-1 after 300 cycles of charge and discharge. In addition, the electrode material had excellent rate performance, and when the current density was 960 Ma g ~ (-1), the specific discharge capacity of the electrode was still as high as 270 mg ~ (-1). The specific discharge capacity is 214mAh g-1.
【学位授予单位】：武汉纺织大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912

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