Investigations of the influences of K+ impurity on the electrolyte for vanadium redox flow battery

It is important to systematically investigate the effects of K impurity on the performance of electrolyte, in order to provide a practical guidance for the electrolyte production and regeneration. The conductivity of electrolyte decreased with the addition of K impurity while the viscosity increased. The static stability tests found that K impurity had slightly effect on the stability of V(III) electrolyte, while it was harmful to the stability of V3.5+ and V(V) electrolyte. In addition, the electrochemical performance of electrolyte and the efficiency of vanadium redox flow battery (VRFB) decreased when the concentration of K impurity was over 8.0 × 10−3 mol L−1. Moreover, the K-V precipitation adsorbed on the graphite felt electrode, resulting in the deteriorated efficiency of VRFB. The temperature adaptability of VRFB tests showed that the VRFB could operate successfully from − 10 to 40 °C when the K impurity was below 8.0 × 10−3 mol L−1 in electrolyte.