TOP CAP ASSEMBLY, BATTERY, AND ELECTRICAL DEVICE

A top cap assembly includes a top cap plate, a mounting piece, and a protection film. The top cap plate includes an inner side and an outer side disposed opposite to each other along a thickness direction of the top cap plate, the inner side and the outer side are spaced apart from each other to form a receptacle in between, and the receptacle communicates with an outside space. The mounting piece is disposed protrusively in the receptacle and comprising a fixed end and a free end disposed opposite to each other. The fixed end is disposed on a wall of the receptacle, and the free end extends along the thickness direction of the top cap plate and is spaced apart from the wall of the receptacle to form a threading clearance. One end of the protection film is attached to the mounting piece through the threading clearance.