Optimization of flow field distribution to improve desalination performance of battery electrode deionization by designing flow channel structure

Battery electrode deionization (BDI) is a technique for removing salts from brine. It works with the aid of electrochemical reactions between ions and active compounds in electrodes under the electric field. In the BDI device, the function of the flow channel is to transport the electrolyte into the cell and assign the reactants to the electrode surface. The BDI flow field with classical plate structures typically suffers large flow dead zones, which greatly reduces the uniformity of the reactants supplied to the electrodes. This will affect the desalination performance of the cell. In particular, the flow field distribution will have an increasing impact on the desalination performance, considering the demand for commercialization and large scaling. In this work, five flow channel proposals of the BDI device are investigated numerically. Flow patterns and intercalation-Na clouds are used to analyze the distribution of the flow field and the intercalation-Na degree. The uniformity factors are introduced to describe the uniformity of Na+ ion concentration and intercalation-Na degree distribution. The salt adsorption capacity (SAC), average salt adsorption rate (ASAR), and volumetric energy consumption are used to evaluate the desalination performance of the system. The results showed that proposals with flow field design can effectively reduce the dead zone within the flow channel and utilize the electrodes more uniformly and fully, and the SAC and ASAR are also improved as a result. Reducing the charging current density and increasing the inlet flow rate can optimize the uniformity of ion distribution within the flow channel and the uniform utilization of the electrode, as well as reduce the volumetric energy consumption.