A battery module, comprising: a plurality of battery cells stacked on one another; a cell housing configured to accommodate the plurality of battery cells; and a cover bus bar configured to cover an entire upper side of the cell housing and electrically connected to electrodes (110, 130) of the plurality of battery cells through electrode connection layers (710, 730) having a layered structure, wherein the cover bus bar has a layered structure including the electrode connection layers (710, 730) and insulation layers (750, 770, 790) for insulating the electrode connection layers (710, 730), wherein the electrode connection layers (710, 730) are disposed between the insulation layers (750, 770, 790), respectively, wherein the cover bus bar includes: a first insulation layer configured to form a lower side of the cover bus bar and provided to face the plurality of battery cells; a first electrode connection layer disposed at an upper side of the first insulation layer and electrically connected to one of positive electrodes and negative electrodes (110, 130) of the plurality of battery cells; a second insulation layer disposed at an upper side of the first electrode connection layer; a second electrode connection layer disposed at an upper side of the second insulation layer and electrically connected to the other of the positive electrode and the negative electrode (110, 130) of the plurality of battery cells; and a third insulation layer disposed at an upper side of the second electrode connection layer to form an upper side of the cover bus bar, where the battery module further comprises a heatsink mounted to at least one of the cell housing and the cover bus bar to cool the plurality of battery cells, where the battery module further comprises a phase change material filled in the cell housing so that the plurality of battery cells are partially immersed therein, the phase change material being adapted to guide cooling of the plurality of battery cells by evaporating when a temperature of the plurality of battery cells is raised and then moving toward the cover bus bar, and consequently liquefying by the heatsink and moving to a lower side of the cell housing. a plurality of battery cells stacked on one another; a cell housing configured to accommodate the plurality of battery cells; and a cover bus bar configured to cover an entire upper side of the cell housing and electrically connected to electrodes (110, 130) of the plurality of battery cells through electrode connection layers (710, 730) having a layered structure, wherein the cover bus bar has a layered structure including the electrode connection layers (710, 730) and insulation layers (750, 770, 790) for insulating the electrode connection layers (710, 730), wherein the electrode connection layers (710, 730) are disposed between the insulation layers (750, 770, 790), respectively, wherein the cover bus bar includes: a first insulation layer configured to form a lower side of the cover bus bar and provided to face the plurality of battery cells; a first electrode connection layer disposed at an upper side of the first insulation layer and electrically connected to one of positive electrodes and negative electrodes (110, 130) of the plurality of battery cells; a second insulation layer disposed at an upper side of the first electrode connection layer; a second electrode connection layer disposed at an upper side of the second insulation layer and electrically connected to the other of the positive electrode and the negative electrode (110, 130) of the plurality of battery cells; and a third insulation layer disposed at an upper side of the second electrode connection layer to form an upper side of the cover bus bar, a first insulation layer configured to form a lower side of the cover bus bar and provided to face the plurality of battery cells; a first electrode connection layer disposed at an upper side of the first insulation layer and electrically connected to one of positive electrodes and negative electrodes (110, 130) of the plurality of battery cells; a second insulation layer disposed at an upper side of the first electrode connection layer; a second electrode connection layer disposed at an upper side of the second insulation layer and electrically connected to the other of the positive electrode and the negative electrode (110, 130) of the plurality of battery cells; and a third insulation layer disposed at an upper side of the second electrode connection layer to form an upper side of the cover bus bar, where the battery module further comprises a heatsink mounted to at least one of the cell housing and the cover bus bar to cool the plurality of battery cells, where the battery module further comprises a phase change material filled in the cell housing so that the plurality of battery cells are partially immersed therein, the phase change material being adapted to guide cooling of the plurality of battery cells by evaporating when a temperature of the plurality of battery cells is raised and then moving toward the cover bus bar, and consequently liquefying by the heatsink and moving to a lower side of the cell housing.