END COVER ASSEMBLY, BATTERY, AND ENERGY STORAGE DEVICE

An end cover assembly includes a top cover unit, a pole, an upper plastic member, and a fixing member. The pole penetrates the top cover unit and includes a base portion and a connecting portion protruding from an end surface of the base portion. A part of the end surface of the base portion outside a coverage area of the connecting portion is formed as a step surface surrounding the connecting portion. The upper plastic member is at least partially sleeved on a peripheral side of the base portion. The upper plastic member is partially located at a side of the top cover unit. The fixing member is partially located at the other side of the top cover unit. A seam is formed between the fixing member and the connecting portion and surrounds the connecting portion, and the step surface abuts against the fixing member and cover the seam.