The application relates to the technical field of energy storage devices, and in particular, to a device, a battery pack, a battery module, and a connection assembly. The connection assembly includes: a connecting sheet; an insulating film which is connected to a plurality of the connecting sheets, where the insulating film is provided with a weakened portion. In the present application, the weakened portion has weaker strength. When force is applied, deformation and/or breakage occur/occurs at the weakened portion, thereby reducing the risk of tearing at other positions of the insulating film, improving the flexibility of the connection assembly, and reducing the risk of exposure of the connecting sheet due to the tearing of the insulating film, such that the risk of short circuit between the connecting sheet and other conductive component is reduced, and the safety performance of the battery module is improved.