An end cover assembly for an energy-storage apparatus, comprising: a top cover having a first surface, wherein the top cover further defines a liquid-injection hole extending through the first surface; and the first surface comprises a first sub-surface and a second sub-surface connected to the first sub-surface, the first sub-surface is around the liquid-injection hole, the second sub-surface is around a periphery of the first sub-surface, and roughness of the first sub-surface is greater than roughness of the second sub-surface, characterized in that: the end cover assembly further comprises a sealing cap, and an annular welding portion located at a junction between the sealing cap and the top cover, wherein the sealing cap seals the liquid-injection hole and is connected to the top cover; the top cover is further provided with a first welding mark at the first sub-surface, and the first welding mark comprises a first end portion and a second end portion opposite to the first end portion; and the first end portion is connected to the welding portion, and the second end portion is located at a periphery of the welding portion and is spaced apart from the welding portion; and a ratio of an outer radius R4 of the welding portion to a length L2 of the first welding mark is in a range of 0.4 ≤ R4/L2 ≤ 2.8. a top cover having a first surface, wherein the top cover further defines a liquid-injection hole extending through the first surface; and the first surface comprises a first sub-surface and a second sub-surface connected to the first sub-surface, the first sub-surface is around the liquid-injection hole, the second sub-surface is around a periphery of the first sub-surface, and roughness of the first sub-surface is greater than roughness of the second sub-surface, characterized in that: the end cover assembly further comprises a sealing cap, and an annular welding portion located at a junction between the sealing cap and the top cover, wherein the sealing cap seals the liquid-injection hole and is connected to the top cover; the top cover is further provided with a first welding mark at the first sub-surface, and the first welding mark comprises a first end portion and a second end portion opposite to the first end portion; and the first end portion is connected to the welding portion, and the second end portion is located at a periphery of the welding portion and is spaced apart from the welding portion; and a ratio of an outer radius R4 of the welding portion to a length L2 of the first welding mark is in a range of 0.4 ≤ R4/L2 ≤ 2.8. the end cover assembly further comprises a sealing cap, and an annular welding portion located at a junction between the sealing cap and the top cover, wherein the sealing cap seals the liquid-injection hole and is connected to the top cover; the top cover is further provided with a first welding mark at the first sub-surface, and the first welding mark comprises a first end portion and a second end portion opposite to the first end portion; and the first end portion is connected to the welding portion, and the second end portion is located at a periphery of the welding portion and is spaced apart from the welding portion; and a ratio of an outer radius R4 of the welding portion to a length L2 of the first welding mark is in a range of 0.4 ≤ R4/L2 ≤ 2.8.