In the invention, several middle monoblock batteries (14) are fixed between monoblock batteries (15) on left side and monoblock batteries (16) on right side. Pressboards (7) are fixed on outside of monoblock batteries (15) on left side and monoblock batteries (16) on right side. There is through hole (12) on one side of pressboards (7). Safety valve (6) is fixed inside through hole (12) on pressboard (7). Air chambers are connected through hole (4). Pore ring (3) made from hydrophobic material is fixed inside through hole (4) on base plate (8) in bipolarity. The invention possesses advantages of reasonable design, simple structure, large power density, high energy density, suitable for operation under high energy density and production in large scale.