A battery capable of improving cycle characteristics is provided. An anode active material layer is formed by a vapor phase method, and includes Si as an element. In the anode active material layer, a plurality of primary particles formed by growth in a thickness direction are included, and the plurality of primary particles are agglomerated to form a plurality of secondary particles. Each secondary particle is separated by a groove formed by charge and discharge, and some of primary particles are split particles split by the groove. The average number of the split particles per secondary particle in 5 or more adjacent secondary particles is 10 or more. Moreover, the primary particles and the secondary particles are inclined to the same side.