A battery includes a housing having a base. A battery cell stack and an enclosure are supported on the base of the housing. The battery cell stack includes a plurality of battery cells physically separated into a first battery cell group and a second battery cell group. The enclosure includes first and second support walls respectively disposed on opposite first and second sides of the first battery cell group and a canopy extending between the first and second support walls, above the first battery cell group. The enclosure partially surrounds the first battery cell group on three sides and establishes a physical and thermal barrier between the first battery cell group and the second battery cell group.