The flow battery comprises a first semi-cell (2), wherein a first electrolyte is fed through a first electrode (21); a second semi-cell (3), wherein a second electrolyte is fed through a second electrode (31); a partition membrane (4) disposed between the first electrode (21) and second electrode (31) in order to prevent them from reciprocally contacting with each other, and suitable to enable ions to permeate; and at least one porous barrier material layer (5) disposed between the first electrode (21) and second electrode (31), and suitable to block an undesired flow of ions of one or both the electrolytes through the partition membrane (4), the barrier material layer (5) having zones with different selectivities towards the ions whose flow is undesired.