Disclosed herein is a secondary battery pack including a battery cell having an electrode assembly of a cathode/separator/anode structure mounted in a battery case together with an electrolyte in a sealed state, an insulative mounting member having openings, through which electrode terminals of the battery cell are exposed to the outside, the insulative mounting member being configured to have a structure in which a safety element is mounted to the top of the insulative mounting member, the insulative mounting member being disposed in direct contact with the top of the battery cell, and an insulative cap coupled to the top of the battery cell so that the insulative cap surrounds the insulative mounting member in a state in which the safety element is mounted to the insulative mounting member, wherein the battery case is provided at the top thereof with a coupling groove, and the insulative cap is provided at the bottom thereof with a coupling protrusion formed in a shape corresponding to the coupling groove, the coupling of the insulative cap to the battery cell being achieved by the insertion of the coupling protrusion into the coupling groove.