Performance improvements for the all-copper redox flow battery: Membranes, electrodes, and electrolytes

Abstract

The ever-increasing demand for renewable energy storage has led to the development of many energy storage systems, such as redox flow batteries (RFBs), including vanadium, iron–chromium, and the copper redox flow battery (CuRFB). A multitude of materials and electrolytes have been investigated to improve the performance of the CuRFB using an in-house manufactured cell. Using carbon ink coatings for the negative electrode and modern ion exchange membranes (IEMs), this version of the CuRFB was improved to current efficiencies above 95% with high voltage efficiencies of up to 81%, thereby improving energy efficiency by nearly 9% over the previous state of the art at 20 mA cm −2. Additionally, the operating time of the CuRFB was significantly extended over 210 h of operation (50 cycles), 32% of the capacity remaining, without maintenance. Finally, stability of the new system with modern IEMs was proven by operation for over 1200 h operation, with over 300 charge and discharge cycles performed.