Top cover, top cover assembly, battery monomer, battery and electric device

The utility model relates to a top cover, a top cover assembly, a battery monomer, a battery and an electric device. Liquid injection holes are formed in the top cover in a penetrating mode and comprise the first liquid injection hole and the second liquid injection hole which are sequentially formed in the center axis direction of the top cover. Wherein the radial size of the first liquid injection hole is larger than that of the second liquid injection hole, the radial size of the end, close to the second liquid injection hole, of the first liquid injection hole is D1, the radial size of the end, away from the second liquid injection hole, of the first liquid injection hole is D2, D1 is larger than D2, the size, in the central axis direction of the top cover, of the first liquid injection hole is H, (D1-D2)/2 = D0, H/D0 = A, A is 0.5-2.5, and D is larger than D2. Therefore, the manufacturing of the first liquid injection hole is facilitated, the thickness of the adhesive filled in the first liquid injection