SECONDARY BATTERY

A battery module includes a battery assembly including a plurality of sub-packing units, the plurality of sub-packing units respectively including a cell housing, at least one battery cell accommodated in an internal space of the cell housing, and at least one vent hole disposed in the cell housing and connecting the internal space to an outside of the cell housing, and a flame blocking structure coupled to the battery assembly, and including an inlet hole connected to the vent hole, an inner chamber communicating with the inlet hole, an outlet hole communicating with the inner chamber and the outside, and at least one partition wall protruding into the inner chamber.