The present disclosure is directed to an improved energy storage device having a housing with one or more side walls that define an internal volume. The side walls include a bottom side wall and a front side wall having an air inlet and outlet. The energy storage device also includes a plurality of cells arranged in a matrix within the internal volume atop the bottom side wall. Further, the cells define a top surface. In addition, the energy storage device includes an airflow distribution network configured with the air inlet and the air outlet. Moreover, the airflow distribution network is at least partially sealed from the plurality of cells (e.g. at the front side wall) so as to reduce temperature variability across the cells when external air is provided through the air inlet.