A battery module , comprising batteries sequentially arranged in a first direction (X); 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 (X); the two second side walls being respectively positioned at two sides of the electrode assembly in a second direction (Y), the second direction (Y) being perpendicular to the first direction (X); 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 (Y), and the second surface facing the first side wall in the first direction (X); 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 (Y); or the first electrode plate , the separator and the second electrode plate being stacked in the second direction (Y), the second direction (Y) being perpendicular to the first direction (X); a distance between the electrode assemblies of two adjacent batteries in the first direction (X) 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 (X); the two second side walls being respectively positioned at two sides of the electrode assembly in a second direction (Y), the second direction (Y) being perpendicular to the first direction (X); 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 (Y), and the second surface facing the first side wall in the first direction (X); 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 (Y); or the first electrode plate , the separator and the second electrode plate being stacked in the second direction (Y), the second direction (Y) being perpendicular to the first direction (X); a distance between the electrode assemblies of two adjacent batteries in the first direction (X) 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 . <EOS>