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铝电解电容器用阳极箔增容技术基础研究

发布时间:2019-01-11 14:23
【摘要】:铝电解电容器因其优良的性能、低廉的价格及可靠的质量在通讯市场、生活电器领域、工业领域等得到了广泛的应用。同时,电子产品的快速发展也对铝电解电容器的小型化、高比容等性能提出了更高的要求。而实现电解电容器小型化、高比容的关键技术在于有效提高阳极箔的电容。阳极箔的电容计算公式为C=(εε0S)/d,其中ε0为真空介电常数(8.85×10-12(F·m-1)),S表示电极板的有效面积,d表示的氧化膜的厚度。无论A1203是无定形结构还是晶形结构,其相对介电常数ε是确定的,在8~10之间。氧化膜的厚度d可以用公式d=Ea.K表示,其中Ea表示化成电压,K表示氧化膜的形成常数。为此,当化成电压Ea一定时,d是一定的,很难通过减小d的数值来提高比电容。基于上述分析,本文通过在腐蚀工艺中引入超声强化传质来改善铝箔的发孔状态,即通过优化蚀孔形貌,增大S继而提高C;其次,在化成工艺中引入Ti02-Al203复合介电膜层来增大ε,继而提高C。主要的研究内容及结论如下:(1)在辅助超声条件下,通过直流电解腐蚀制备高压电极铝箔。具体通过计时电位、动电位极化、循环伏安、交流阻抗等测试手段,详细研究了超声强化传质对腐蚀箔的电化学行为及界面行为的作用规律。采用XRD能谱、扫描电镜及低温N2吸附等手段对腐蚀箔进行表征。结果表明超声搅拌作用有效抑制了氧化铝膜的生长,通过增加氧化铝/电解液界面处C1-的吸附量促进了点蚀的萌生,通过减小氧化铝/电解液界面处扩散层的厚度,即减小电解液的传质阻力,强化了 Cl-向孔内以及生成产物A13+、A1C13向孔外的扩散。最终,超声辅助制备的腐蚀箔的双电层电容Cdl、蚀孔密度、平均蚀孔孔径/平均蚀孔深度及孔径/孔深的均一性都得到了提高。(2)运用溶胶—凝胶法在腐蚀箔表面引入了 TiO2阀金属氧化物,化成处理后获得了高介电常数的Al2O3-TiO2复合介电膜层。用扫描电镜、EDS能谱以及XRD能谱分析了氧化膜的表面形貌、成分及腐蚀箔截面处Ti元素的分布特点。研究结果表明,经过550 ℃C热处理后,锐钛矿型Ti02已成功获得,但随着涂覆量的增加,蚀孔孔径减小且被堵塞的几率变大,涂层缺陷更易形成。此外,氧化膜的升压曲线、动电位极化曲线以及交流阻抗曲线的分析结果表明,当单位腐蚀箔表面Ti的涂覆量为4.4 mg·cm-2时,化成阶段消耗的形成电量最小,相对无涂层腐蚀箔减少了 85%,与之对应的化成箔的比容达到最大值(54.16μF·cm-2),相对无涂层化成箔比容增加了 25.84%。
[Abstract]:Aluminum electrolytic capacitors have been widely used in communication market, household appliances and industrial fields because of their excellent performance, low price and reliable quality. At the same time, the rapid development of electronic products also put forward higher requirements for the miniaturization and high specific capacity of aluminum electrolytic capacitors. The key technology to realize the miniaturization and high specific capacity of electrolytic capacitor is to increase the capacitance of anode foil effectively. The capacitance formula of anodic foil is C = (蔚 -0S) / d, where 蔚 _ 0 is the vacuum dielectric constant (8.85 脳 10 ~ (-12) (F _ m ~ (-1), S) is the effective area of the electrode plate and d is the thickness of the oxide film. Regardless of whether A1203 is amorphous or crystalline, the relative dielectric constant 蔚 is determined between 810 and 10. The thickness d of the oxide film can be expressed by the formula d=Ea.K, where Ea denotes the formation voltage and K represents the formation constant of the oxide film. For this reason, when the formation voltage Ea is constant, d is certain, so it is difficult to increase the specific capacitance by reducing the value of d. Based on the above analysis, ultrasonic enhanced mass transfer is introduced into the corrosion process to improve the formation of aluminum foil, that is to say, by optimizing the morphology of the etching hole, increasing S and then increasing the C; Secondly, the Ti02-Al203 composite dielectric layer was introduced to increase 蔚 and then to increase C. The main research contents and conclusions are as follows: (1) High voltage electrode aluminum foil was prepared by direct current electrolysis under the condition of assisted ultrasound. By means of chronopotentiometry, potentiodynamic polarization, cyclic voltammetry and AC impedance, the effect of ultrasonic enhanced mass transfer on the electrochemical behavior and interface behavior of corrosion foil was studied in detail. Corrosion foil was characterized by XRD, SEM and N2 adsorption at low temperature. The results show that ultrasonic stirring can effectively inhibit the growth of alumina membrane, promote the initiation of pitting corrosion by increasing the adsorption of C1- at the interface of alumina / electrolyte, and decrease the thickness of diffusion layer at the interface of alumina / electrolyte. By reducing the mass transfer resistance of the electrolyte, the diffusion of Cl- into the pore and the formation products A13 and A1C13 out of the pore was strengthened. Finally, ultrasonic assisted preparation of the double-layer capacitance Cdl, etching hole density of the etched foil, The uniformity of average pore diameter / average hole depth and pore diameter / hole depth were improved. (2) TiO2 valve metal oxide was introduced on the surface of corroded foil by sol-gel method. The Al2O3-TiO2 composite dielectric film with high dielectric constant was obtained. The surface morphology, composition and distribution of Ti elements in the section of the corrosion foil were analyzed by SEM, EDS and XRD spectra. The results show that anatase Ti02 has been successfully obtained after heat treatment at 550 鈩,

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