A lower box body, wherein the lower box body has an accommodating area for accommodating a battery cell; the lower box body is further provided with an exhaust port and an exhaust channel, and the exhaust port is in communication with the exhaust channel; the exhaust port is arranged in the corresponding accommodating area; and the lower box body further comprises an exhaust assembly, the exhaust assembly is configured to block the exhaust port, and the exhaust assembly is configured to be open when pressure in the accommodating area reaches a set value, so that gas in the accommodating area enters the exhaust channel through the exhaust port; wherein the exhaust assembly comprises a ventilation frame and a baffle; the ventilation frame is close to the accommodating area relative to the baffle; the ventilation frame is connected to a periphery of the exhaust port, and the ventilation frame and the baffle are rotatably connected; when the pressure of the accommodating area does not reach the set value, the baffle covers the ventilation frame; and when the pressure of the accommodating area reaches the set value, the baffle rotates and opens to allow the gas to penetrate the ventilation frame and enter the exhaust channel; wherein the ventilation frame comprises a first body and a first connection part that are connected; the first body is in a mesh structure; wherein the baffle comprises a second body and a second connection part that are connected; the exhaust assembly further comprises a rotating shaft; the first connection part and the second connection part are rotatably connected through the rotating shaft; when the pressure of the accommodating area does not reach the set value, the second body covers the first body; and when the pressure of the accommodating area reaches the set value, the second body is separated from the first body, so that the gas penetrates the first body and enters the exhaust channel. the lower box body is further provided with an exhaust port and an exhaust channel, and the exhaust port is in communication with the exhaust channel; the exhaust port is arranged in the corresponding accommodating area; and the lower box body further comprises an exhaust assembly, the exhaust assembly is configured to block the exhaust port, and the exhaust assembly is configured to be open when pressure in the accommodating area reaches a set value, so that gas in the accommodating area enters the exhaust channel through the exhaust port; wherein the exhaust assembly comprises a ventilation frame and a baffle; the ventilation frame is close to the accommodating area relative to the baffle; the ventilation frame is connected to a periphery of the exhaust port, and the ventilation frame and the baffle are rotatably connected; when the pressure of the accommodating area does not reach the set value, the baffle covers the ventilation frame; and when the pressure of the accommodating area reaches the set value, the baffle rotates and opens to allow the gas to penetrate the ventilation frame and enter the exhaust channel; wherein the ventilation frame comprises a first body and a first connection part that are connected; the first body is in a mesh structure; wherein the baffle comprises a second body and a second connection part that are connected; the exhaust assembly further comprises a rotating shaft; the first connection part and the second connection part are rotatably connected through the rotating shaft; when the pressure of the accommodating area does not reach the set value, the second body covers the first body; and when the pressure of the accommodating area reaches the set value, the second body is separated from the first body, so that the gas penetrates the first body and enters the exhaust channel.