Abstract: Housing structures for slim batteries are provided. A housing structure comprises a plastic frame surrounding the battery and two metal plates. The battery is covered by the metal plates from opposite sides thereof, respectively. Each of the metal plates comprises a laminar body and a plurality of anchor-shaped protrusions extending therefrom and joining in the plastic frame. Each of the protrusions comprises a flat front edge and two side edges extending from opposite sides thereof to the laminar body, wherein each of the side edges has a smooth recess. The flat front edge of the anchor-shaped protrusion increases effective area of ultrasonic welding. The recess increases contact surface between the frame and the protrusion, improving ultrasonic or high frequency welding and facilitating robust connection thereof.