Disclosed herein is a battery cell assembly including a battery cell array including two or more battery cells, each of which has an electrode assembly of a cathode/separator/anode structure disposed in a battery case together with an electrolyte in a sealed state, arranged in the lateral direction, and a protection circuit module (PCM) connected to the upper end of the battery cell array to control the operation of the battery pack, wherein the outer sides of the battery cells or the outer side of the battery cell array is coated with a resin by insert injection molding excluding electrode terminals of the battery cells.