Electrode foil with edge region thickness variation for improved electrolytic capacitor reliability

An electrolytic capacitor comprising

• a wound capacitor element,
• wherein the capacitor element includes a wound body obtained by winding together a band-shaped anode foil, a band-shaped cathode foil, and a separator arranged between the anode foil and the cathode foil,
• at least one of the anode foil and the cathode foil includes a band-shaped metal foil having a first region and a second region other than the first region,
• the metal foil includes a first edge portion extending in a length direction of the metal foil and a second edge portion that is opposite to the first edge portion,
• the second region is at least one of a 2A region extending linearly along the first edge portion and a 2B region extending linearly along the second edge portion,
• the thickness of the second region is smaller than the thickness of the first region,
• steps are provided between the first region and the second region on both surfaces of the metal foil,
• the anode foil includes the metal foil having porous portions on surfaces of the first region and the second region, and a dielectric layer covering a surface of the porous portions, and
• a ratio of a most frequent pore diameter P2 of the porous portion in the second region to a most frequent pore diameter P1 of the porous portion in the first region:
• P2/P1 is 0.3 or more and 0.8 or less.

An electrolytic capacitor comprising

• a stack in which a plurality of stacked capacitor elements are stacked,
• wherein the capacitor elements each include:
• a metal foil having a cathode forming portion, an anode extraction portion extending from one edge portion of the cathode forming portion, and a porous portion on a surface of the metal foil;
• a dielectric layer covering the cathode forming portion;
• and
• a cathode portion covering the dielectric layer,
• the cathode forming portion includes a first region and a second region other than the first region,
• the second region is a region extending linearly along another edge portion of the cathode forming portion other than the one edge portion,
• the thickness of the second region is smaller than the thickness of the first region,
• steps are provided between the first region and the second region on both surfaces of the metal foil, and
• a ratio of a most frequent pore diameter P2 of the porous portion in the second region to a most frequent pore diameter P1 of the porous portion in the first region:
• P2/P1 is 0.3 or more and 0.8 or less.

A method for manufacturing an electrolytic capacitor, comprising:

• a first step of preparing a metal base sheet having a plurality of first regions and a plurality of cutting regions alternately in stripes;
• a second step of compressing the cutting regions in a thickness direction of the metal base sheet to form a plurality of second regions;
• and
• a third step of obtaining a plurality of electrode foils by cutting central portions of the cutting regions in a width direction of the cutting regions, along a length direction of the cutting regions such that each of the plurality of electrode foils has the first region and the second region, wherein
• the first step includes a step of forming a porous portion by roughening a surface of the metal base sheet,
• the first region is band-shaped,
• the first step includes a step of forming a dielectric layer covering a surface of the porous portion,
• a band-shaped anode foil is obtained as the electrode foil in the third step, and
• a ratio of a most frequent pore diameter P2 of the porous portion in the second region to a most frequent pore diameter P1 of the porous portion in the first region:
• P2/P1 is 0.3 or more and 0.8 or less.