A symmetric all-organic non-aqueous redox flow-type battery was investigated employing the neutral small molecule radical 3-phenyl-1,5-di-p-tolylverdazyl,which can be reversibly oxidized and reduced in one-electron processes,as the sole charge storage material.Cyclic voltammetry of the verdazyl radical in 0.5 M tetrabutylammonium hexafluorophosphate (TBAPF6) in acetonitrile revealed redox couples at-0.17 V and-1.15 V vs.Ag+/Ag,leading to a theoretical cell voltage of 0.98 V.From the dependence of peak currents on the square root of the scan rate,diffusion coefficients on the order of 4 × 10 6 cm2 s-1 were demonstrated.Cycling performance was assessed in a static cell employing a Tokoyuma AHA anion exchange membrane,with 0.04 M verdazyl as catholyte and anolyte in 0.5 M TBAPF6 in acetonitrile at a current density of 0.12 mA cm 2.Although coulombic efficiencies were good (94％-97％) throughout the experiment,the capacity faded gradually from high initial values of 93％ of the theoretical discharge capacity to 35％ by the 50th cycle.Voltage and energy efficiencies were 68％ and 65％,respectively.Postcycling analysis by cyclic voltammetry revealed that decomposition of the active material with cycling is a leading cause of cell degradation.