A secondary battery, a battery pack and a device using the battery are provided, wherein the end cover assembly includes: an end cover with a through hole for injection of electrolyte and an accommodating part, the accommodating part is arranged on a side far away from a shell of the end cover and is arranged along a circumferential direction of the through hole; a sealing element; and a cover body for covering at least part of the sealing element, the cover body is rotatable and includes a limiting part; when the cover body rotates to a first position, the limiting part is located inside the accommodating part to limit separation of the cover body from the end cover; when the cover body rotates to a second position, the limiting part and the accommodating part are misplaced to realize separation of the cover body from the end cover.