Preparation method of square battery cell and square battery cell

The invention relates to the technical field of batteries, in particular to a preparation method of a square battery cell and the square battery cell. The preparation method of the square battery cell comprises the following steps that an insulated cooling fin is provided, the cooling fin comprises a vertical plate and at least one bottom plate, and the bottom plate is arranged at at least one end, in the height direction, of the vertical plate; and the negative pole piece, the diaphragm and the positive pole piece are wound or laminated to form a battery cell main body. Before the battery cell main body is pressurized, the vertical plate is inserted into the battery cell main body, and the bottom plate is exposed out of one axial end of the battery cell main body. The battery cell main body is pressurized, and the pressure direction is parallel to the plate thickness direction of the vertical plate, so that one side of the vertical plate in the thickness direction is attached to the negative pole piece, the