Electrode structure and preparation methods thereof

An electrode structure in a film-shaped form comprising a substrate and a sintered body,

• wherein the sintered body is a porous sintered body having a thickness of 20 μm to 100 μm that is formed by sintering a layer comprising valve metal particles having an average particle diameter, D50, of 1 μm to 10 μm on the surface of the substrate, and the sintered body comprises a first end that extends along a first edge of the electrode structure, a second end that extends along a second edge that is opposite the first edge, a length that extends perpendicularly to the first and second edges, and a series of cracks spaced at substantially regular intervals along the length of the sintered body that each penetrate and extend continuously from the first end to the second end
• wherein adjacent cracks are separated by intervals with an average length of no more than 0.15 mm,
• wherein the cracks have a width of no greater than 100 μm and are formed after a hydration treatment of the sintered body and before a formation process,
• wherein of the hydration treatment is performed at a temperature of 70° C. to 100° C. and a hydration treatment time of 1 minute to 16 minutes;
• wherein the formation process is carried out by applying a voltage to the sintered body and forms an oxide film with a dielectric function on the surface of the sintered body;
• wherein the substrate is a foil comprising a valve metal wherein the valve metal of the sintered body and the foil comprises aluminum or an aluminum alloy.