Titanium-Cerium Redox Flow Batteries for Grid-Scale Electrical Energy Storage

The development of redox flow batteries (RFBs) has gained increased attention due to the need of mitigating emission pollution from fossil fuels by developing renewable energy storage system. Among all the different types of RFBs, all vanadium one (VRFBs) are the most prevalent type because crossover contamination is avoided by using only one metal element. However, VRFBs still suffer from limitations such as low output voltage, low efficiency, and high material cost. Titanium (Ti) and cerium (Ce), on the contrary, are available in abundance and have lower cost. Moreover, the standard potential of Ti-Ce combination is much higher than that of VRFBs (1.61 vs. 1.23 V). Herein, we have studied and compared the performance of Ti-Ce RFBs with sulfuric acid (SA) and methanesulfonic acid (MSA) serving as the supporting electrolyte. We applied an asymmetric electrode configuration, i.e., carbon felt for Ti side and carbon paper for Ce side, to further promote the batteries performance. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used to analyze the mass transport and reaction kinetics of the Ti-Ce system. Electrochemical impedance spectroscopy (EIS) was used to analyze the contribution of different types of polarization. Ti-Ce RFBs demonstrated an energy efficiency around 80 % at 100 mA/cm 2 , and excellent capacity retention.