CELL STACK AND REDOX FLOW BATTERY

A cell stack is in which a plurality of battery cells are stacked, including an electrode of a porous body, and a bipolar plate facing the electrode, in which the bipolar plate includes an introduction portion of an electrolyte, a discharge portion of the electrolyte, and a plurality of first grooves extending from a side at which the introduction portion is disposed toward a side at which the discharge portion is disposed, each of the plurality of first grooves allows the electrolyte in each of the plurality of first grooves flow toward the discharge portion, R2/R1 is 7×10−11 or more and 2×10−4 or less, R1 is a permeation resistance indicating a difficulty of a flow of the electrolyte in the electrode, and R2 is a permeation resistance indicating the difficulty of the flow of the electrolyte in each of the plurality of first grooves.