Electrode for secondary battery and secondary battery

An electrode for a secondary battery, comprising:

• a substrate;
• and
• an active material layer, wherein
• the active material layer is placed on a surface of the substrate,
• one or more grooves are formed in a surface of the active material layer,
• the groove extends linearly in a direction perpendicular to a thickness direction of the active material layer,
• the groove has an open portion on a periphery of the active material layer,
• the open portion opens in the direction perpendicular to the thickness direction,
• the groove, which extends linearly from the open portion to another open portion on an another periphery of the active material layer, includes a first region and a second region,
• the first region is a single continuous region on the groove,
• the second region is interposed between the open portion and the first region, and
• in a cross section perpendicular to a direction in which the groove extends,
• the first region has a first cross-sectional area and has a first depth,
• the second region has a second cross-sectional area and has a second depth,
• the second cross-sectional area is smaller than the first cross-sectional area, and
• the second depth is smaller than the first depth.