Asymmetric structure design of a vanadium redox flow battery for improved battery performance

In this study, asymmetric porous electrode compression and asymmetric blocked serpentine flow field designs are proposed. With a well-developed 3-D VRFB model incorporating electrode compression effect, the compression ratio for each half-cell and the block factor of each flow field are delicately optimized, and their impacts on battery performance as well as power loss mechanism were analyzed in detail. Results indicate that the optimal asymmetric structure with four design variables are negative electrode compression rate of 0.38, positive electrode compression rate of 0.5, negative block factor of 0.9 and positive block factor of 0.6 at flow rate of 80 ml mi n − 1 and current density of 200 mA c m − 2 . As compared with the optimal symmetric structure design (i.e., electrode compression rate of 0.41 and block factor of 0.8 for both electrodes), the optimal asymmetric structure shows 3.3%-5.4% increment in the net discharge power for various state of charge from 0.1 to 0.9, which is mainly due to the decreased reaction loss and pump loss in negative side as well as the reduced ohmic loss in positive side. Also, it was shown that the same optimal structure with four design parameters can also be achieved by using genetic algorithm, which indicates the reliability of the present optimization.