Bipolar plate, cell frame, battery cell, cell stack, and redox flow battery

A bipolar plate comprising a first surface and a second surface facing each other, wherein

• each of the first surface and the second surface includes a first edge, a second edge, and a middle region,
• the first edge is an edge located on a side to which an electrolyte is supplied,
• the second edge is an edge located on a side from which the electrolyte is discharged,
• the middle region is a region within 20% of an edge interval from a middle line toward each of the first edge and the second edge,
• the middle line comprising a center line bisecting a distance between the first edge and the second edge,
• the edge interval is an interval between the first edge and the second edge,
• the middle region on at least one of the first surface and the second surface includes a plurality of groove portions through which the electrolyte flows,
• the middle region includes a specific cross section obtained by cutting the bipolar plate in a specific direction,
• the specific direction is a direction orthogonal to a direction from the first edge toward the second edge,
• the specific cross section is a cross section having a cross-sectional area ratio B/(A+B) greater than or equal to 0.05 and less than or equal to 0.60,
• A is a cross-sectional area of the bipolar plate, and
• B is a total cross-sectional area of the plurality of groove portions.