US Patent 8394529 Preparation of flow cell battery electrolytes from raw materials

A method for preparing a redox flow battery electrolyte is provided. In some embodiments, the method includes the processing of raw materials that include sources of chromium ions and/or iron ions. The method further comprises the removal of impurities such as metal ions from those raw materials. In some embodiments, an ammonium salt may be used to remove metal impurities from an aqueous mixture of chromium ions and/or iron ions. Further provided is a redox flow battery comprising at least one electrolyte prepared from the above-identified methods.