Abstract: Electrochemical cells, such as those present within flow batteries, can have at least one electrode with a density gradient in which the density increases outwardly from a separator. Such electrodes can decrease contact resistance and lessen the incidence of parasitic reactions in the electrochemical cell. Flow batteries containing the electrochemical cells can include: a first half-cell containing a first electrode, a second half-cell containing a second electrode, and a separator disposed between the first half-cell and the second half-cell. At least one of the first electrode and the second electrode has a density gradient such that a density of at least one of the first electrode and the second electrode increases outwardly from the separator.