Abstract: The present invention provides a redox flow type battery which a liquid-circulating battery comprising a battery cell and storage tanks for positive and negative electrolytes, wherein the battery cell is separated by a membrane to provide a positive cell and a negative cell, each cell having a liquid-permeable porous electrode disposed therein, wherein the positive and negative electrolytes are sulfuric acid aqueous solutions with vanadium ion concentrations of 0.5 mol/l to 8 mol/l and the electrolyte which migrates through the membrane over cycles of charge and discharge is returned from the storage tank where the liquid increases to the storage tank where the liquid decreases in order to keep the change in the amounts of the positive and negative electrolytes in a certain range while charge and discharge are carried out.

Abstract: The present invention provides a liquid-circulating battery including a positive electrode, a negative electrode, a permeable membrane interposed between the positive and negative electrodes to hold the same in separated relation to each other and to partition the same into a positive chamber and a negative chamber, two porous liquid-permeable carbon electrodes disposed respectively in the positive and negative electrolytic solutions being circulated respectively into the positive and negative chambers such that an oxidation-reduction reaction occurs and causes charging and discharging, wherein the permeable membrane is an ion-exchange me membrane including as an ion exchanger layer a polymeric pellicle which results from crosslinking of a halogenated alkylated product of an aromatic polysulfone type polymer with use of a polyamine and which has an ion exchange capacity of 0.3 to 8.0 milliequivalent/gram of dry resin and a thickness 0.1 to 120 .mu.