Investigation of the flow rate optimization of the Zn/LiFePO4 aqueous flow battery

Zn/LiFePO4 aqueous flow batteries are regarded as promising energy storage technologies due to their low cost, high safety, and high energy density, but the short cycle life hinders the further applications. In this work, the cycle life is improved by optimizing the electrolyte flow rate. The results show that as the flow rate increases, the capacity retention rate of the battery shows an initial increase but followed by a decrease. Compared with the capacity retention rate of 86.05% after 100 cycles with no flow, the capacity retention rate at the optimal flow rate of 0.25 mL min−1 can reach 106.35 %. Simulation results show that flow improves the uniformity of the electrolyte to some extent and reduces concentration polarization. For the decay of the capacity retention rate at high flow rates, two hypotheses are proposed, including the conjecture of “dead zone” and concerns about the effects of high flow rates on desolvation and adsorption processes based on the test results. In the future, more means are expected to be used to explore its mechanism more accurately. This work provides insights into the mechanisms of flow effects on cycle life and provides ideas for flow rate optimization for other types of flow batteries.