An energy storage assembly includes a plurality of battery cells electrically connected to each other to form a battery pack in which the battery cells are grouped together to form a first stack of cells and a second stack of cells. The energy storage assembly also includes a first barrier disposed between the first stack of cells and the second stack of cells to reduce heat transfer between the first stack of cells and the second stack of cells. The energy storage assembly further includes a coolant plate disposed along the battery cells. The coolant plate defines a channel for guiding a fluid therethrough to thermally transfer heat away from the battery cells. The coolant plate defines a slot spaced from the channel, and the slot axially aligns with the first barrier to reduce heat transfer between the first stack of cells and the second stack of cells.