A response time-based method to operando decouple the polarizations in redox flow batteries

The polarization of redox flow batteries (RFBs) consists of activation polarization, ohmic polarization, and concentration polarization. However, the three types of polarizations are coupled in practice, making it difficult to quantify the respective attributions to the total voltage loss and to compare the reported performance of RFBs under different working conditions. Here, we propose a method to operando decouple the polarizations of RFBs based on the different response times of the three kinds of polarizations. The decoupled polarizations in RFBs under different working conditions are presented with specific voltage losses, which clarifies the limit parameters of battery performance and makes the reports of RFBs comparable even with similar battery performances. This work opens up a method to quantitatively analyze activation polarization and concentration polarization separately in RFBs, which provides significant guidance for improving battery performance effectively. [Display omitted] •A response time-based method is proposed to operando decouple the polarizations in RFBs•The activity and mass transfer ability of electrodes are quantitatively analyzed•This method enables the performance reports of different RFBs comparable Wang et al. propose a response time-based method to operando decouple the polarizations in redox flow batteries (RFBs). This method enables us to analyze the activation and concentration polarizations in RFBs quantitatively and offers guidance for designing high-performance RFBs, making the reports of RFBs under different working conditions comparable.