Abstract: A battery cell assembly includes a plurality of cylindrical cell blocks, each of the plurality of cylindrical cell blocks including a plurality of cylindrical cells, a block cover configured to cover an upper side of the plurality of cylindrical cell blocks and electrically connect the plurality of cylindrical cell blocks, a cooling plate located opposite to the block cover and disposed at a lower side of the plurality of cylindrical cell blocks and a heat transfer member disposed between the cooling plate and the plurality of cylindrical cell blocks and having a plurality of thermal interface materials corresponding to bottom portions of the plurality of cylindrical cells.