Hybrid anode and electrolytic capacitor

A method of forming an anode for a capacitor, comprising:

• generating tunnels in a tunneled portion of an aluminum current collector such that the tunnels extend from a first face of the current collector to a second face of the current collector,
• the tunnels having an average width greater than 1.5 μm and less than 10 μm, and
• the tunnels having an average tunnel density greater than 5 M/cm2 and less than 90 M/cm2,
• adding active layers to the tunneled portion of the current collector such that the current collector is positioned between the active layers and the one or more active layers are not positioned over a tab portion of the current collector,
• the tab portion of the current collector excludes the tunnels,
• an average width of all of the tunnels that extend from the first face of the current collector to the second face of the current collector and that are between the active layers is greater than 1.5 μm and less than 10 μm, and
• the one or more active layers including fused particles;
• and
• fabricating the capacitor such that the tab portion provides electrical communication between the anode and a terminal that is accessible from outside of a case of the capacitor.