BATTERY PACK

본 발명의 일 실시예에 따른 전고체 이차 전지는, 전극 조립체; 및 상기 전극 조립체를 수용하는 케이스를 포함하고, 상기 전극 조립체는, 단위 셀부, 음극 집전체부 및 양극 집전체부를 포함하고, 상기 케이스는 서로 절연된 제1,2 케이스를 포함하고, 상기 음극 집전체부는 상기 제1 케이스와 접촉하고, 상기 양극 집전체부는 상기 제2 케이스와 접촉한다. A battery pack includes: a plurality of battery cells in a plurality of columns, the battery cells in each of the columns being located along a column direction, and the battery cells in the columns adjacent to each other being located along a zigzag pattern in a row direction while alternately shifted forward and rearward in the column direction; a plurality of cooling pieces, each of the cooling pieces being located between the battery cells in the columns adjacent to each other, and extending in a meander shape along an outer circumference of the battery cells in the columns adjacent to each other; and a bus bar on a terminal surface of the battery cells to electrically connect the battery cells to each other in rows adjacent to each other, the terminal surface being a surface on which different first and second electrodes are exposed.