An energy storage system includes a cell having a flow chamber for receiving electrolyte, and an electrode positioned in the cell. The electrode includes a base plate having a generally planar portion and a plurality of partially cutout portions partially cut out from the generally planar portion to define a plurality of openings in the base plate. Each cutout portion is attached to the generally planar portion and has a projecting part that extends away from the generally planar portion. Furthermore, the openings and the cutout portions are configured to enhance mixing of the electrolyte when the electrolyte is received in the flow chamber.