NOVELTY - The battery (10) has a liquid-porous electrode layer provided with a set of micro and macro pores. The macro pores include a size, where order of magnitude is greater than the size of the macro pores. An electrolyte solution e.g. catholyle solution, is provided with reversible redox couple reactant i.e. charge carrier ion. The solution wets the electrode layer. The macro pores are arranged in a pattern that extends along an electrolyte solution flow direction via the electrode layer. The electrode layer extends between surfaces. A carbon backing layer is placed adjacent to the electrode layer.    USE - Flow battery for selectively storing and discharging electrical energy, converting the electrical energy generated by a renewable or non-renewable power system into chemical energy stored within a pair of electrolyte solutions e.g. anolyte and catholyte solutions, vanadium/vanadium electrolyte solutions and bromine/polysulphide electrolyte solutions, and for converting the stored chemical energy back into electrical energy.    ADVANTAGE - The battery tests heat treatment processes to convert carbon species to more graphitic forms so as to improve corrosion resistance. The carbon backing layer provides mechanical support to the electrode layer, improves uniform distribution of die electrolyte solution to the electrode layer, and provides a temporary electrolyte solution reservoir or additional surface area to complete redox reactions during rapid start up and transient conditions. The battery allows a column of macro pores adjacent to a surface of the electrode layer and provides a higher macro pore density than columns of macro pores proximate to another surface to reduce pressure drop adjacent to the former surface. The battery allows a column of micro pores adjacent to the latter surface of the electrode layer and provides higher micro pore density than the columns of micro pores proximate to the former surface to increase electrode surface area for electrochemical interactions with the respective electrolyte solutions in regions, thus increasing density of the redox reactions that occur near the latter surface of the electrode layer, and hence reducing ionic losses in a cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of a flow battery system including flow battery cells arranged in a stack.    Flow battery (10)    Electrolyte storage tanks (12, 14)    Electrolyte circuit loops (16, 18)    Flow battery cell (20)    Stack (21)