【作者】 张利；

【导师】 刘伟；

【作者基本信息】 大连理工大学 ， 化学工程， 2021， 硕士

【摘要】 超级电容器作为一种新型绿色储能装置,由于功率密度高、循环寿命长等优点受到一定关注,但其能量密度有限、成本高等缺点限制了其广泛应用。水系中性电解质类型的超级电容器具有安全、廉价和高倍率性能的特点,尤其是由双电层电容器（EDLC）型负极和电池型正极组成的非对称电池可以提供较高的工作电压（大于2.0 V）,这使水系超级电容器具有较高的能量密度。开发具有高能量密度,低成本和长寿命的各种正极材料变得越来越迫切,而普鲁士蓝类似物（PBA）由于其高容量和出色的循环稳定性而备受关注。Cu Fe普鲁士蓝类似物,也称为六氰合铁酸铜（CuHCF）,有快速扩散的通道并充分容纳碱金属离子,使其成为有吸引力的电极材料。通常,CuHCF是通过共沉淀法制备,由于[Fe（CN）₆]^3-和Cu²⁺离子的沉淀反应非常快,以至于无法控制CuHCF晶体的生长。本文提出了一种有效的两步合成手段,以HKUST-1为模板以可控的方式制备CuHCF。此外,CuHCF材料被用于组装电池型超级电容器,其中活性炭被选作负极。具体的实验内容如下:先用PVP作表面活性剂辅助水热合成了HKUST-1正八面体前驱物,后用HKUST-1为模板来转化为CuHCF。通过XRD、SEM、TEM、FT-IR、XPS和氮气吸脱附等手段对其进行物理表征,同时探究了PVP对普鲁士蓝结构和形貌的影响。依表征结果推测最佳水热合成温度为120℃,PVP能将HKUST-1粒径较好的控制在3μm左右,2 mmol均苯三甲酸对应表面活性剂PVP最佳使用量为0.1 g,电化学表征得出使用K₃[Fe（CN）₆]转化的CuHCF性能更佳。SEM及TEM结果表明HKUST-1转化得到的CuHCF为细碎的颗粒,氮气吸脱附等温线可证明其微孔结构,孔径约0.55 nm。同时通过循环伏安法、恒流充放电法和交流阻抗图谱测试了CuHCF材料的电化学性能,将CuHCF材料的电位窗口设定为0.1-1V,在0.5 mol L^-1Na₂SO₄中性电解质中,CuHCF-2电极在1 A g^-1电流密度下比电容为254.1 F g^-1,且有优异的倍率性能和循环稳定性。后通过结合CV曲线和充放电前后CuHCF样品的XPS分析来解释其详细的储能机制,可以得出CuHCF材料在储能中Cu²⁺/Cu⁺氧化还原对被激活,即CuHCF样品通过Fe³⁺/Fe²⁺和Cu²⁺/Cu⁺氧化还原来进行充放电。用最佳CuHCF样品作正极、活性炭作负极组装的非对称超级电容器CuHCF//AC,电容器在1 A g^-1电流密度下比电容为45.7 F g^-1,在1066.4 W kg^-1的功率密度下能提供25.4 Wh kg^-1的能量密度,2000次循环后容量保持率为83%。并且本文结合了多壁碳纳米管和MnO₂纳米片来构建CuHCF/CNT和CuHCF/MnO₂复合材料来提高其综合性能。CuHCF/CNT材料由于颗粒容易聚集,其最高比电容为209.0 F g^-1;由于CuHCF和MnO₂纳米片良好的协同效应,CuHCF/MnO₂-1电极在1 A g^-1电流密度下比容量最高为260.9 F g^-1,优于单独的CuHCF和MnO₂电化学性能。同时通过在合成中掺杂Ni和Zn来得到Ni掺杂CuHCF和Zn掺杂CuHCF电极材料,掺入Ni和Zn后Cu Ni HCF和Cu Zn HCF的比容量没有明显的提升。更多还原

【Abstract】 As a new type of environmental energy storage device,supercapacitor has attracted much attention due to the advantages of high power density and long-cycle life,but its shortcomings such as low energy density and high cost limit the large-scale application.Supercapacitors with neutral aqueous electrolytes possess the features of safety,inexpensive and high rate performance.Especially,an asymmetrical cell consisting of an electric double-layer capacitor（EDLC）-type anode and a battery-type cathode can provide high operation voltage（ca.more than 2.0 V）,which endows aqueous supercapacitor with high energy density.There is an urgent demand to explore and develop a variety of cathode materials with high energy density,low cost,and long-cycle life.Currently,Prussian blue analogues（PBAs）have attracted much attention owing to their high capacity and remarkable cycle stability.CuFe Prussian blue analogue,which is also named as copper hexacyanoferrate（CuHCF）,allows fast diffusion and sufficient accommodation of alkali metal ions,making it an attractive electrode material.Generally,CuHCF is prepared by co-precipitation method.The precipitation reaction of[Fe（CN）₆]^3-and Cu²⁺ions is so fast that the growth of CuHCF crystals is uncontrollable.Herein,we proposed an effective two-step synthesis approach that HKUST-1 was used as template to prepare CuHCF in a controllable way.Furthermore,the CuHCF materials were utilized to assemble a supercapacitor cell,in which activated carbon was chosen as anode material.The detailed experimental contents are as follows:The precursor of HKUST-1 with regular octahedron structure was firstly synthesized hydrothermally using PVP as a surfactant,and then the HKUST-1 was converted into CuHCF.The material was characterized by means of XRD,SEM,TEM,FT-IR and nitrogen adsorption/desorption.The effect of PVP on CuHCF’s morphology and electrochemical properties was also investigated.The results showed that the optimal hydrothermal synthesis temperature was 120℃.The particle size of HKUST-1 could be controlled to 3μm with 0.1 g of PVP when the molar amount of 1,3,5-benzene tricarboxylic acid was 2 mmol.The characterization showed that the HKUST-1 derived CuHCF exhibited better performance.SEM and TEM images showed that the CuHCF was composed by fine particles,and the nitrogen adsorption and desorption isotherm proved its microporous structure with a pore size of about0.55 nm.The electrochemical performance of CuHCF was tested by cyclic voltammetry,galvanostaticcharge/discharge and AC impedance methods.The CuHCF electrode exhibited a specific capacity of 254.1 F g^-1 in the potential range of 0.1-1V at a current density of 1 A g^-1.According to the CV curve and the XPS results,the energy storage mechanism could be interpreted that the Cu²⁺/Cu⁺redox couple was activated during the processes of charge and discharge.Thus,the CuHCF electrode underwent the redox reactions of Fe³⁺/Fe²⁺and Cu²⁺/Cu⁺couples for charge storage.The obtained CuHCF was used as the positive electrode to assemble an asymmetric supercapacitor along with the activated carbon（AC）as the negative electrode.The hybrid cell CuHCF//AC delivered a specific capacitance of 45.7 F g^-1 at a current density of 1A g^-1,provided an energy density of 25.4 Wh kg^-1 at a power density of 1066.4 W kg^-1 and retained 83%capacitance after 2000 cycles.For improving its overall performance,building composite materials could be used as a common method.Meanwhile,multi-walled carbon nanotubes and MnO₂ nanosheets were employed to fabricate novel composite materials of CuHCF/CNT and CuHCF/MnO₂.The CuHCF/CNT material showed a specific capacitance of 209.0 F g^-1 with excellent rate performance.Furthermore,the CuHCF/MnO₂ hybrid material was fabricated.Because of the synergistic effect of CuHCF and MnO₂ nanosheets,the CuHCF/MnO₂ electrode exhibited a maximum specific capacity of 260.9 F g^-1 at a current density of 1 A g^-1,which was higher than the specific capacitance of CuHCF and MnO₂ alone.Furthermore,Ni-doped CuHCF and Zn-doped CuHCF materials were prepared with the goal of improving the electrochemical performance.No significant increase in specific capacity was observed on Cu Ni HCF and Cu Zn HCF materials.更多还原