NOVELTY - A reversible fuel cell (C1,C1') has a positive electrode (6,6') having manganese dioxide, a negative electrode (4,4') having hydrogen occlusion material, separator (5,5') and electrolyte solution (3,3'). Hydride of hydrogen storage material (M) decomposes to give storage material, hydrogen and electron, and manganese oxide reacts with hydrogen and electron to give manganese peroxide during discharge reaction. Storage material reacts with hydrogen to give hydride of storage material, and manganese peroxide reacts with oxygen to give manganese oxide and water, by charge reaction.    USE - Reversible fuel cell. Uses include but are not limited to industrial and domestic electrical storage apparatus, power supply for electric vehicle, fuel cell electric vehicle, electric train, etc.    ADVANTAGE - The reversible fuel cell and cell system have exceptional energy usage efficiency, energy density, and load-following characteristics.    DETAILED DESCRIPTION - A reversible fuel cell has a positive electrode containing manganese dioxide, a negative electrode containing a hydrogen occlusion material, a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution. The negative electrode and the positive electrode are electrodes for generating electricity, and are adapted for electrolyzing the electrolyte solution using an electric current supplied from an outside source. Hydride of hydrogen storage material (M) decomposes to give hydrogen storage material, hydrogen and electron, and manganese oxide reacts with hydrogen and electron to give manganese peroxide during discharge reaction of negative electrode and positive electrode. Hydrogen storage material reacts with 1/2 mol of hydrogen to give hydride of hydrogen storage material, and manganese peroxide reacts with oxygen to give manganese oxide and water, by charge reaction of negative electrode and positive electrode. Hydrogen and oxygen are dissolved in electrolyte solution. INDEPENDENT CLAIMS are included for the following:    (1) reversible fuel cell module;    (2) reversible fuel cell bank; and    (3) reversible fuel cell system.    DESCRIPTION OF DRAWING(S) - The drawings show the sectional view of reversible fuel cell and schematic view of modification of reversible fuel cell. (Drawing includes non-English language text)    Electrolyte solution (3,3')    Negative electrode (4,4')    Separator (5,5')    Positive electrode (6,6')    Oxygen storing room (7,7')    Reversible fuel cell (C1,C2)