Battery

The negative electrode forms a honeycomb core. The honeycomb core includes a first face, a second face, a partition, and a circumferential wall. The second face faces the first face. The partition is formed between the first face and the second face. In a cross section parallel to the first face, the partition separates a plurality of hollow cells. The separator includes a first layer. The first layer covers at least part of the partition. The cross section parallel to the first face includes a central part and an inner circumferential part. The central part is surrounded by the inner circumferential part. In the central part, the hollow cells have a first average filling factor. In the inner circumferential part, the hollow cells have a second average filling factor. The second average filling factor is 2.1 times or more the first average filling factor.