The invention relates to a stack of electrochemical cells (10A, 10B), divided up into at least two groups (A, B), each cell comprising a distribution circuit for a reactive species, and each group of cells comprising a separate supply collector (2A; 2B). At least one cell (10B) comprises a homogenization compartment (60B) comprising: a plurality of longitudinal conduits (61B) designed to receive the flow of the reactive species coming from the supply collector (2B) of the corresponding group and to distribute it over the inlet (51B) of the distribution circuit for the cell; and, a transverse conduit (62B) for homogenization connecting the longitudinal conduits (61B) to one another in a fluid sense.