A battery module, comprising batteries sequentially arranged in a first direction; the battery comprising an electrode assembly, a case and a cap assembly, the electrode assembly being received in the case, and the cap assembly being connected with the case; the case comprising two first side walls and two second side walls, and the two first side walls being respectively positioned at two sides of the electrode assembly in the first direction; the two second side walls being respectively positioned at two sides of the electrode assembly in a second direction, the second direction being perpendicular to the first direction; the first side walls of two adjacent batteries facing each other;an area of the first side wall being defined as S 1, an area of the second side wall being defined as S2, and S2 being larger than S1; the electrode assembly comprising two first surfaces and two second surfaces (11 1e), and an area of the first surface being larger than an area of the second surface; the first surface facing the second side wall in the second direction, and the second surface facing the first side wall in the first direction; the electrode assembly comprising a first electrode plate, a second electrode plate (11 1b) and a separator (11 1c) provided between the first electrode plate and the second electrode plate; the first electrode plate, the separator and the second electrode plate being wound to a flat shape, and the two first surfaces being flat surfaces and facing each other in the second direction; or the first electrode plate, the separator and the second electrode plate being stacked in the second direction, the second direction being perpendicular to the first direction; a distance between the electrode assemblies of two adjacent batteries in the first direction being defined as D, S 1 and D satisfying a relationship: 1.2 × 10 − 5 mm − 1 ≤ D / S 1 ≤ 500 × 10 − 5 mm − 1. the battery comprising an electrode assembly, a case and a cap assembly, the electrode assembly being received in the case, and the cap assembly being connected with the case; the case comprising two first side walls and two second side walls, and the two first side walls being respectively positioned at two sides of the electrode assembly in the first direction; the two second side walls being respectively positioned at two sides of the electrode assembly in a second direction, the second direction being perpendicular to the first direction; the first side walls of two adjacent batteries facing each other;an area of the first side wall being defined as S 1, an area of the second side wall being defined as S2, and S2 being larger than S1; the electrode assembly comprising two first surfaces and two second surfaces (11 1e), and an area of the first surface being larger than an area of the second surface; the first surface facing the second side wall in the second direction, and the second surface facing the first side wall in the first direction; the electrode assembly comprising a first electrode plate, a second electrode plate (11 1b) and a separator (11 1c) provided between the first electrode plate and the second electrode plate; the first electrode plate, the separator and the second electrode plate being wound to a flat shape, and the two first surfaces being flat surfaces and facing each other in the second direction; or the first electrode plate, the separator and the second electrode plate being stacked in the second direction, the second direction being perpendicular to the first direction; a distance between the electrode assemblies of two adjacent batteries in the first direction being defined as D, S 1 and D satisfying a relationship: 1.2 × 10 − 5 mm − 1 ≤ D / S 1 ≤ 500 × 10 − 5 mm − 1.