Battery pack case providing improved uniformity in coolant flux

A middle- or large-sized battery pack case in which a battery module having a plurality of stacked unit cells, which can be charged and discharged, is mounted, wherein

• the battery pack case is provided at an upper part and a lower part thereof with a coolant inlet port and a coolant outlet port, respectively, which are directed in opposite directions such that a coolant for cooling the unit cells can flow from one side to the other side of the battery module in the direction perpendicular to the stacking direction of the unit cells,
• the battery pack case is further provided with a coolant introduction part, as a flow space extending from the coolant inlet port to the battery module and a coolant discharge part, as another flow space extending from the battery module to the coolant outlet port, and
• an upper end inside part of the coolant introduction part facing a top of the cell stack is configured in a structure to include a first incline plane starting from the end opposite to the coolant inlet port and a second incline plane located between the first incline plane and the coolant inlet port such that the second incline plane has an inclination greater than that of the first incline plane;
• wherein the second incline plane has an inclination 20 to 500% greater than the inclination of the first incline plane within a range in which the second incline plane has an inclination not exceeding 45 degrees with respect to the top of the cell stack.