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. <EOS>