A battery module includes one or more first battery cells and one or more second battery cells. A first number a of the one or more first battery cells is greater than or equal to a second number b of the one or more second battery cells. A first product X1 of a first volumetric energy density E1 and a first thickness T1 of each of the one or more first battery cells and a second product X2 of a second volumetric energy density E2 and a second thickness T2 of each of the one or more second battery cells satisfy. 0.35≤X1/X2≤18.