Method for producing electrode for aluminum electrolytic capacitor

Abstract

In the manufacture of electrodes for electrolytic capacitors, in the hydration step, the aluminum electrode is immersed in a hydration treatment solution at a temperature of 80°C or higher to form a hydration film on the aluminum electrode, and then in the chemical conversion step, the aluminum electrode is chemically treated. Conversion until a chemical conversion voltage above 400V. The hydration treatment liquid contains a hydration inhibitor. For the thickness of the hydration film formed in the hydration step, the average thickness of the hydration film formed from the surface of the aluminum electrode to a depth of 100 μm is t1, and the thickness of the hydration film formed at a depth of 100 μm or more from the surface of the aluminum electrode When the average thickness s of the hydrated film is t2, the following conditions are satisfied: 0.6≤t2 / t1≤1.

Description

technical field [0001] The present invention relates to a method for producing an electrode for an aluminum electrolytic capacitor by chemically converting an aluminum electrode. Background technique [0002] A method for producing an electrode for an aluminum electrolytic capacitor used as an anode of an aluminum electrolytic capacitor for medium and high voltages is known in which a step of boiling the aluminum electrode with pure water is performed before performing a chemical conversion treatment. By boiling pure water, the power consumption required for the chemical conversion can be kept low, and the electrostatic capacitance after the chemical conversion can be made high. [0003] However, since aluminum has high reactivity with water, the hydration reaction between the aluminum electrode and water when pure water is boiled is intense. Therefore, the hydrated film generated by boiling pure water is porous and has many defects. Therefore, defects remain in the chemic...

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Problems solved by technology

Therefore, when an etched foil having tunnel-like pits (pits) is used as an aluminum electrode for medium and high voltages, the pits will be clogged on the surface due to the hydrates generated by the intense hydration reaction, and further, due to the clogging or generation of Bubbles, there is a tendency for the hydration reaction to be difficult to proceed in the depth of the pit

In addition, when a porous aluminum electrode obtained by forming a porous layer composed of a sintered layer of aluminum powder on the surface of an aluminum core material is used as an aluminum electrode, a violent hydration reaction proceeds on the surface of the aluminum electrode, so The resulting hydrates can cause clogging near the surface

In addition, due to the clogging or generated air bubbles, the hydration reaction in the deep part (deep part) of the porous layer is difficult to proceed, and a hydration film is formed inappropriately.

When such a situation occurs, it is difficult to discharge the gas generated inside the porous layer during the subsequent chemical conversion, and the porous layer is destroyed, thereby increasing the leakage current of the electrode for aluminum electrolytic capacitors.

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