Disclosed herein is a battery module comprising a plurality of battery cells encased in an outer shell. The outer shell has disposed on an inner surface a flame retardant layer that comprises expandable graphite. The expandable graphite is operative to expand during an thermal event that results in an increase in battery module temperature. Disclosed herein too is a method comprising disposing in a battery module a flame retardant layer; where the battery module comprises a plurality of battery cells encased in an outer shell. The outer shell has disposed on an inner surface a flame retardant layer that comprises expandable graphite. The expandable graphite is operative to expand during an thermal event that results in an increase in battery module temperature.