A battery cell for use in a redox flow battery, the battery cell including an electrode, a membrane facing one of both surfaces of the electrode, and a bipolar plate facing the other surface of the electrode, wherein the bipolar plate includes, in a surface thereof facing the electrode, a flow channel for an electrolyte, the electrode is a porous body containing carbon materials, and a compressive strain in a thickness direction of the electrode when a compressive stress of 0.8 MPa is applied in the thickness direction of the electrode is 20% or more and 60% or less.