Manufacture of non-aqueous redox flow batteries using sulfate-templated Dawson-type polyoxometalate with improved performances

The compatible redox pairs are essential to make non-aqueous redox flow batteries (NRFBs) reach their full potentials. Two novel NRFBs with polyoxometalate (POM) redox pairs were designed and investigated. [C16H36N](4)[S2W18O62] used as anolyte and benzophenone(BP) severed as catholyte in an asymmetric NRFB, these two diverse active species could cooperate well with each other and achieve a high theoretical cell voltage of 1.54 V. During the charge-discharge cyclic tests, it yielded impressive results with the coulombic efficiency more than 97%, and high voltage efficiency and energy efficiency were delivered without reduction. At the current density of 0.5 mA cm(-2), this reformative asymmetric battery delivered a volumetric capacity of 1.97 Ah L-1. The excellent stability of [C16H36N](4)[S2W18O62] was validated by the identical (HNMR)-H-1 and XRD spectra. As a comparison, the symmetric battery employed [C16H36N](4)[S2W18O62] both as anolyte and catholyte, which delivered a moderate performances with the coulombic efficiency was about 90%. Also, the permeability of polyoxoanion [S2W18O62](4-) cross through AMI-7001 membrane was 1.307x10(-7) cm(2) min(-1) and less than 1% of this active species had crossed over after 3 d stationary tests.

Automated summary

The novel non-aqueous redox flow batteries with polyoxometalate (POM) redox pairs exhibited high theoretical cell voltage and impressive performance during charge-discharge cyclic tests. The asymmetric NRFB using [C16H36N](4)[S2W18O62] and benzophenone as active species achieved a coulombic efficiency of over 97% and excellent stability, while the symmetric NRFB showed moderate performance with lower coulombic efficiency. The permeability of polyoxoanion [S2W18O62](4-) through the AMI-7001 membrane was also examined.