Abstract: The present invention relates to a polymer blend proton exchange membrane comprising a soluble polymer and a sulfonated polymer, wherein the soluble polymer is at least one polymer selected from the group consisting of polysulfone, polyethersulfone and polyvinylidene fluoride, the sulfonated polymer is at least one polymer selected from the group consisting of sulfonated poly(ether-ether-ketone), sulfonated poly(ether-ketone-ether-ketone-ketone), sulfonated poly(phthalazinone ether keton), sulfonated phenolphthalein poly(ether sulfone), sulfonated polyimides, sulfonated polyphosphazene and sulfonated polybenzimidazole, and wherein the degree of sulfonation of the sulfonated polymer is in the range of 96% to 118%. The present invention further relates to a method for manufacturing the polymer blend proton exchange membrane.

Abstract: The present invention provides a redox flow battery comprising a positive electrolyte storage tank and a negative electrolyte storage tank, wherein the positive electrolyte storage tank and the negative electrolyte storage tank is kept to be in liquid communication through a pipe, wherein the length-to-diameter ratio of the pipe for the liquid communication is not less than about 10. The present invention also provides a method for operating the redox flow battery continuously in a long period of time.