JP4849257B2 - Solid electrolyte and solid electrolytic capacitor using the same - Google Patents

Description

  The present invention relates to a solid electrolyte, a solid electrolytic capacitor using the same, and a manufacturing method thereof, and more particularly to a solid electrolyte having high withstand voltage characteristics and a solid electrolytic capacitor using the same.

  An electrolytic capacitor using a metal having a valve action such as aluminum can obtain a small size and a large capacity by expanding the surface of the dielectric by making the valve action metal as an anode electrode into the shape of an etching foil or the like. It is widely used because it can. In particular, a solid electrolytic capacitor using a solid electrolyte as an electrolyte has features such as small size, large capacity, low equivalent series resistance, easy to chip, and suitable for surface mounting. It is indispensable for miniaturization and high functionality of electronic equipment.

  As the solid electrolyte used for the solid electrolytic capacitor, a conductive polymer having high conductivity and excellent adhesion to the oxide film layer of the anode electrode is used as the solid electrolyte. As this conductive polymer, for example, polyaniline, polythiophene, polyethylenedioxythiophene and the like are known.

  Among these, polyethylenedioxythiophene (hereinafter referred to as PEDOT) has attracted attention as a conductive polymer that can achieve a high breakdown voltage because the withstand voltage can be increased with respect to the thickness of the oxide film. In the capacitor using PEDOT, chemical oxidative polymerization is used, and it is manufactured as follows. That is, the anode foil and the cathode foil are wound through a separator to form a capacitor element. The capacitor element is impregnated with EDOT and an oxidant solution and heated to form a PEDOT polymer layer between the two electrodes. An electrolytic capacitor is formed (Patent Document 1).

  Such a solid electrolytic capacitor is used for in-vehicle use and inverter use, but the working voltage increases from 20 WV to 35 WV, and in order to cope with these, the capacitor element is composed of a compound having a vinyl group and a boric acid compound. It is disclosed that the withstand voltage is increased by including a conjugate (Patent Document 2).

Japanese Patent Laid-Open No. 9-293639 JP 2003-100560 A

  However, even with such a technique, a high withstand voltage is not sufficient, and an object is to provide a solid electrolytic capacitor having a high withstand voltage characteristic and a method for manufacturing the same.

  In order to solve the above-mentioned problems, the solid electrolyte according to the first aspect of the present invention is prepared by dispersing a doped conductive polymer particle and preparing a solution in which an ion conductive polymer and an electrolyte salt thereof are dissolved. The solution is formed by removing the solvent.

  Further, the conductive polymer may be poly 3,4-ethylenedioxythiophene, and the ion conductive polymer may be polyethylene oxide.

  Further, poly3,4-ethylenedioxythiophene: polyethylene oxide = 1: 0.2 to 1: 1 may be used.

  In addition, the molar ratio between the oxygen atom of polyethylene oxide and the cation of the electrolyte salt may be 6-10.

  Next, the electrolyte salt may be ammonium borate.

  The solid electrolytic capacitor according to the second aspect of the present invention is characterized by using the solid electrolyte layer.

１） 表１は導電性高分子の分散液とイオン伝導性高分子とその電解質塩の三者の混合させた溶液から複合ポリマー膜を形成させ、コンデンサ素子を作製し、電圧掃引した際の絶縁破壊電圧を示したものである。導電性高分子とイオン伝導性高分子とその電解質塩からなるものは、イオン伝導性が発現し、皮膜の欠陥部の修復能の向上が図れるため、絶縁破壊電圧が向上する。
２） イオン伝導性高分子は常温固体であり、リフローなどの高温試験時に気化することがなく、水を加えた場合の高温気化の体積膨張による皮膜と高分子の剥離や高分子鎖同士の剥離が生じないため、容量の低下やＥＳＲの増大を防ぎ、製品としての高温時の特性劣化が防止できる。

1) Table 1 shows the insulation when a composite polymer film is formed from a mixed solution of a conductive polymer dispersion, an ion conductive polymer and an electrolyte salt thereof to produce a capacitor element and voltage is swept. The breakdown voltage is shown. Those composed of a conductive polymer, an ion conductive polymer, and an electrolyte salt thereof exhibit ionic conductivity and can improve the repair ability of defective portions of the film, so that the dielectric breakdown voltage is improved.
2) The ion-conductive polymer is a solid at room temperature and does not vaporize during high-temperature tests such as reflow. The film and polymer are peeled off due to the volume expansion of high-temperature vaporization when water is added. Therefore, a decrease in capacity and an increase in ESR can be prevented, and deterioration of characteristics at a high temperature as a product can be prevented.

  The present invention uses a three-component composite of doped conductive polymer particles, an ion conductive polymer, and an electrolyte salt thereof as an electrolyte of a solid electrolytic capacitor.

  A well-known polymer is used as the ion conductive polymer, and representative examples include polyether polymers such as polyethylene oxide (formula (1)) and polypropylene oxide. Polyester polymers and polyamine polymers Can also be used. Moreover, these copolymers, crosslinked bodies, and derivatives can also be used. Examples of the conductive polymer include poly 3,4-ethylenedioxythiophene and polyaniline. Of these, poly3,4-ethylenedioxythiophene is preferable.

  Examples of the electrolyte salt to be present as the conductive ion species of the ion conductive polymer include ammonia (formula (2)) as a cation, and examples of the anion include carboxylic acid such as adipic acid and boric acid. An electrolyte salt of a combination of anions is used. Here, Formula (3) shows PEDOT.

  The solid electrolyte of the present invention is a solid electrolyte formed by dispersing a conductive polymer particle, creating a solution in which an ion conductive polymer and an electrolyte salt thereof are dissolved, and removing the solvent of the solution. As an example, a solution in which conductive polymer particles are dispersed is mixed with a solution in which an ion conductive polymer and an electrolyte salt thereof are dissolved, and this mixed solution is dropped on an aluminum foil to remove the solvent by drying. To form a solid electrolyte.

  Since the solid electrolyte of the present invention uses a conductive polymer doped in advance, an oxidant is not used in the formation process of the solid electrolyte, and the oxide film of the solid electrolytic capacitor is not damaged by the oxidant. In addition, deterioration of the withstand voltage characteristics of the oxide film can be prevented.

  Here, FIG. 1a and FIG. 1b are graphs showing the effect of the amount of electrolytic salt on the capacity characteristics and ESR characteristics of the capacitor using the composite polymer film. As an aluminum substrate, an aluminum etching foil formed by conversion at 160 V is used. The weight ratio of the aqueous dispersion of PEDOT is 3 wt%, and the weight ratio of the PEO solution to the aqueous solution of ammonium borate is 1 wt%. FIG. 1a shows the capacitance characteristics with respect to the molar ratio of oxygen atom and ammonium cation of PEO, and FIG. 1b shows the ESR value with respect to the molar ratio.

  FIG. 2 shows the breakdown voltage characteristics of an etching foil type capacitor using a composite polymer film. A short of the molar ratio when an aluminum etching foil made of 160V is used as an aluminum substrate and left in a decompressor at a temperature of 25 degrees Celsius and 5 kPa as a low-humidity condition for 15 hours or more and then voltage application is started. The voltage characteristics are shown. From these results, the molar ratio of the ion conductive polymer to the electrolyte salt is preferably 6 to 10.

  An aqueous solution in which ammonium pentaborate was dissolved in a 1 wt% polyeryrene oxide (PEO) aqueous solution so that the ammonium cation was 1/8 mol with respect to 1 mol of PEO oxygen atoms was prepared. Further, a dispersion aqueous solution containing 3,4-ethylenedioxythiophene (PEDOT) particles having a particle size of 3 wt% of 30 to 40 nm was prepared. These aqueous solutions were mixed at different ratios of PEDOT and PEO to prepare solutions. An aqueous solution was dropped onto an aluminum plain foil and dried to form a polymer layer of several tens of μm, and the capacitance, ESR, and withstand voltage were measured. Each is shown in Figures 3a-4b of the attachment.

Example 1
In Example 1, the PEOOT dispersion aqueous solution was added with a PEO aqueous solution, and the plain foil was evaluated for capacitance characteristics and ESR characteristics. The foil used for the evaluation is a plain foil, which is formed at 150V. For PEO, 1 wt% PEO aqueous solution and 3 wt% PEDOT dispersion aqueous solution are used for ammonium pentaborate (O / NH4). It shows that the capacitance is high at any compounding ratio.

  On the other hand, FIG. 3b shows the PEO ratio characteristics of the ESR value against PEDOT under the same conditions. It is shown that the PEDOT: PEO ratio can be suppressed to several times increase up to 1: 3.

(Example 2)
In Example 2, the VI characteristics and the short voltage characteristics are shown for the PEDOT dispersion aqueous solution, the PEO aqueous solution, and the plain foil. The foil used for the evaluation is a plain foil, which is formed at 150V. About PEO, 1 wt% PEO aqueous solution and 3 wt% PEDOT dispersion aqueous solution are used for ammonium borate (O / NH4).

  FIG. 4a shows the current characteristics with respect to the applied voltage under this condition. It is shown that the pressure resistance increases as the compounding ratio increases.

  FIG. 4b shows the short voltage characteristics under this condition. The short-circuit voltage increases until the molar ratio is 4, and the short-circuit voltage is constant when the molar ratio is 4 or more.

  From the above, in the range of PEDOT: PEO = 1: 0.3 to 1: 1, both the capacitance and the ESR are good, and the withstand voltage characteristic is improved as compared with PEDOT.

The capacity | capacitance characteristic graph about the capacitor | condenser using the composite polymer film concerning this invention is shown. The ESR value characteristic graph with respect to the molar ratio of the oxygen atom in PEO and the ammonia cation about the capacitor | condenser using the composite polymer film which concerns on this invention is shown. The breakdown voltage characteristic graph of the etching foil type capacitor using the composite polymer film concerning the present invention is shown. The capacity | capacitance characteristic graph about the PEO ratio characteristic with respect to PEDOT of the electrostatic capacitance in the capacitor | condenser which concerns on this invention is shown. The capacity | capacitance characteristic graph about the PEO ratio characteristic with respect to PEDOT of the electrostatic capacitance in the capacitor | condenser which concerns on this invention is shown. The current characteristic graph with respect to the applied voltage in the capacitor | condenser which concerns on this invention is shown. The short voltage characteristic graph with respect to the applied voltage in the capacitor | condenser which concerns on this invention is shown.

Claims (5)

A conductive polymer particle made of doped poly 3,4-ethylenedioxythiophene is dispersed and a solution in which an ion conductive polymer made of polyethylene oxide and its electrolyte salt are dissolved is prepared. Solid electrolyte formed by removal. Poly 3,4-ethylenedioxythiophene: polyethylene oxide = 1: 0.2 to 1: solid electrolyte according to claim 1 1. The solid electrolyte according to claim 1 or 2 , wherein the molar ratio of cations of polyethylene oxide and electrolyte salt is 6 to 10. The solid electrolyte according to any one of claims 1 to 3 , wherein the electrolyte salt is ammonium borate. The solid electrolytic capacitor using a solid electrolyte layer as described in any one of claims 1 to 4.

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