An end cover assembly for a battery cell, the end cover assembly comprising: an end cover; an electrode terminal disposed on the end cover; an insulating member for insulating the electrode terminal and the end cover and disposed to surround the electrode terminal, wherein the insulating member abuts the electrode terminal, at least one of the insulating member and the electrode terminal is provided with a stress relief groove, and the stress relief groove is configured to absorb stress generated by the electrode terminal's abutting the insulating member, the insulating member is provided with a through hole, the electrode terminal includes a columnar portion, and the columnar portion is disposed in the through hole and abuts at least part of a hole wall of the through hole; the stress relief groove is disposed along the circumferential direction of the through hole to absorb radial stress generated by the columnar portion's abutting the hole wall, the end cover includes a connecting hole, and the electrode terminal is disposed in the connecting hole, characterised in that: the insulating member includes a main body portion and a positioning portion connected to the main body portion, the main body portion is disposed outside of the connecting hole and extends outward from the hole wall of the connecting hole in both an axial direction and a radial direction of the connecting hole, and the positioning portion protrudes from the main body portion in the axial direction and is disposed in the connecting hole, and the through hole comprises a first through hole positioned in the main body portion and a second through hole positioned in the positioning portion, a radial size of the second through hole is greater than a radial size of the first through hole, the columnar portion of the electrode terminal is disposed in the first through hole and the second through hole and is separated from the hole wall of the second through hole by a predetermined distance. an end cover; an electrode terminal disposed on the end cover; an insulating member for insulating the electrode terminal and the end cover and disposed to surround the electrode terminal, wherein the insulating member abuts the electrode terminal, at least one of the insulating member and the electrode terminal is provided with a stress relief groove, and the stress relief groove is configured to absorb stress generated by the electrode terminal's abutting the insulating member, the insulating member is provided with a through hole, the electrode terminal includes a columnar portion, and the columnar portion is disposed in the through hole and abuts at least part of a hole wall of the through hole; the stress relief groove is disposed along the circumferential direction of the through hole to absorb radial stress generated by the columnar portion's abutting the hole wall, the end cover includes a connecting hole, and the electrode terminal is disposed in the connecting hole, characterised in that: the insulating member includes a main body portion and a positioning portion connected to the main body portion, the main body portion is disposed outside of the connecting hole and extends outward from the hole wall of the connecting hole in both an axial direction and a radial direction of the connecting hole, and the positioning portion protrudes from the main body portion in the axial direction and is disposed in the connecting hole, and the through hole comprises a first through hole positioned in the main body portion and a second through hole positioned in the positioning portion, a radial size of the second through hole is greater than a radial size of the first through hole, the columnar portion of the electrode terminal is disposed in the first through hole and the second through hole and is separated from the hole wall of the second through hole by a predetermined distance. the insulating member includes a main body portion and a positioning portion connected to the main body portion, the main body portion is disposed outside of the connecting hole and extends outward from the hole wall of the connecting hole in both an axial direction and a radial direction of the connecting hole, and the positioning portion protrudes from the main body portion in the axial direction and is disposed in the connecting hole, and the through hole comprises a first through hole positioned in the main body portion and a second through hole positioned in the positioning portion, a radial size of the second through hole is greater than a radial size of the first through hole, the columnar portion of the electrode terminal is disposed in the first through hole and the second through hole and is separated from the hole wall of the second through hole by a predetermined distance.