A battery may include: a box; a first battery cell group and a second battery cell group, where the first battery cell and the second battery cell may have a same battery capacity and different volumetric energy densities. First battery cells in the first battery cell group and second battery cells in the second battery cell group may be arranged in a first direction (x), and the first battery cell group and the second battery cell group may be arranged in a second direction (y). A size of the first battery cell may be different from a size of the second battery cell in the first direction (x), and a size of the first battery cell group may be the same as a size of the second battery cell group in the first direction (x).