Characteristics of the all-vanadium redox flow battery using anion exchange membrane

• A three commercial anion exchange membrane was evaluated for the application as a separator in the all-vanadium redox flow battery (V-RFB).
• AFN membrane (ASTOM Co.) was selected as a separator in V-RFB with its largely unchanged membrane resistance during durability test.
• AFN membrane had a good performance as a separator in V-RFB.
• An average energy efficiency in V-RFB using 1M VOSO4 in 2M H2SO4 and 2M VOSO4 in 4M H2SO4 solution were 72.0% and 74.8%, respectively.

Three commercial anion exchange membranes were evaluated the chemical stability with an increase of soaking time in a pentavalent vanadium ion (VO2+) solution. The membrane resistances of anion exchange membranes in 1M (mol/L) H2SO4 aqueous solution were measured as an indicator of chemical stability. AFN membrane (ASTOM Co., Japan) was selected as a separator in an all-vanadium redox flow battery (V-RFB). The cell performance of V-RFB using AFN membrane was measured at a current density of 60 mA/cm2. The cell resistance for the charge had almost the same value (in the range of 3.47–3.67 Ω cm2) with an increase in the state of charge (SOC). For the discharge, the cell resistance had almost the same value (in the range of 2.00–2.25 Ω cm2) with an increase in the state of discharge (SOD). The cell efficiency of the V-RFB using the AFN membrane was evaluated at each cycle. The average energy efficiency was 72.0%. Thus, the AFN anion exchange membrane is well suited for use in a V-RFB as a separator.