Abstract: The present disclosure provides a flow battery and a cell stack. The cell stack includes: a first end plate; a second end plate; and at least one cell module arranged between the first end plate and the second end plate. Each cell module includes a first flow channel end plate, a second flow channel end plate arranged opposite to the first flow channel end plate, and single-cell assemblies arranged between the first flow channel end plate and the second flow channel end plate. The single-cell assemblies include at least three hermetically-assembled cell assemblies, the first flow channel end plate is provided with arch-like flow channels, the second flow channel end plate is provided with arch-like flow channels, and each arch-like flow channel is provided with a flow channel aperture in communication with the at least three hermetically-assembled cell assemblies.