An effect of electrolyte flow rate on the performance of zinc-bromine flow battery

A zinc bromine flow battery (ZBB) is an attractive and useful technology for the application of utility energy storage, but the distinctive electrochemical characteristics of the electrolyte during the cell operation cause a... [ view full abstract ]

A zinc bromine flow battery (ZBB) is an attractive and useful technology for the application of utility energy storage, but the distinctive electrochemical characteristics of the electrolyte during the cell operation cause a lot of problems. Especially, during cyclic operation a problem of obstructing the flow of anolyte takes place caused by the residual zinc in carbon electrode felt of a zinc-half cell, and this potentially leads to a bad effect on the stability and efficiency of the ZBB cells. This paper deals with an experimental analysis due to various flow rates of electrolyte in ZBB cell. To evaluate the performance of cyclic operation in terms of flow rates of electrolyte, all experiments are carried out with a miniature unit cell (active area: 100 cm²) employing 2.25M ZnBr2 electrolyte at a current density of 10 and 20 mA/cm² for 25-cycle operation. The measurements of cell efficiency are performed with increasing flow rate from 100mL/min to 500mL/min in every 5^th cycle charge and discharge. Experimental results show that the most stable efficiency is indicated at 200 mL/min flow rate with both 10 and 20 mA/cm² as current density. It also appears that the difference increasing between two flow rates of anolyte and catholyte. This paper provides a new insight into long-term cyclic operation of ZBBs and consequently, the flow rates of anolyte and catholyte must be considered as a key factor that affects the performance of ZBBs.