Extrusion coating device, pole piece coating machine and battery production system

The extrusion coating device comprises a shell (10) provided with an inner cavity, the shell wall of the shell (10) is provided with a feeding port (11) and a coating outlet (12) which are both communicated with the inner cavity, and the coating outlet (12) is in a seam shape; the coating device further comprises a porous structure (20) which is arranged in the inner cavity and located on a material flowing path between the feeding port (11) and the coating outlet (12) so that at least one part of materials can penetrate through the porous structure (20). The invention further discloses a pole piece coating machine comprising the extrusion coating device and a battery production system comprising the pole piece coating machine.