Broadening Applicability of the Poor Academic's Method for Reversing Polarity in Redox Flow Cell Cycling

Abstract

The use of symmetrical cells is becoming popular for the search of new electroactive materials in redox flow batteries. Unfortunately, low-cost battery cyclers, commonly used for electrochemical battery testing, are not compatible with symmetrical cells since they usually cannot apply negative bias voltages needed for symmetrical cells. The insertion of a Ni−Cd battery in the voltage sensing path is a simple and effective methodology to overcome this limitation for certain battery cyclers. Herein, the validity of this useful method is evaluated for other battery cyclers, realizing that the strategy is not universal. A modified methodology is developed for a battery cycler in which the previous method is not valid. The new strategy is based on inserting a Ni-MH battery in the current path, and enables using a low-cost Neware CT-4008T-5V6A-S1 cycler for ferro- /ferricyanide symmetrical cells demonstrating proper operation for >19 days. This new method possesses advantages, e. g. direct reading of the cell voltage, and disadvantages, e. g. the Ni-MH battery is charged/discharged during operation, which are discussed. The four battery cyclers evaluated show that, despite neither method is universal, both methods are complementary to each other. Thus, the decision of using either one method or the other must be reached on a case-by-case basis.