| CPC H01M 10/0436 (2013.01) [H01M 4/70 (2013.01); H01M 50/105 (2021.01); H01M 50/119 (2021.01); H01M 50/121 (2021.01); H01M 50/124 (2021.01); H01M 50/133 (2021.01); H01M 50/46 (2021.01); H01M 50/466 (2021.01); H01M 50/533 (2021.01); H01M 50/55 (2021.01); H01M 50/557 (2021.01); H01M 2220/30 (2013.01)] | 10 Claims |

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1. A secondary battery comprising:
a positive electrode current collector;
a positive electrode active material layer; and
a film inside which the positive electrode current collector and the positive electrode active material layer are sandwiched,
wherein the film has a pattern including first depressions extending along a first direction and second depressions extending along a second direction intersecting the first direction in both a center portion of the film and an end portion of the film,
wherein the first direction and the second direction are not parallel to an edge in a width direction of the film,
wherein a depth of the first depressions in the center portion is larger than a depth of the first depressions in the end portion,
wherein a depth of the second depressions in the center portion is larger than a depth of the second depressions in the end portion,
wherein the positive electrode current collector comprises a protruding portion, and wherein the protruding portion has a curved shape.
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