A new redox flow battery of high energy density with V/Mn hybrid redox couples

Mn3+/Mn2+ redox couple with high reaction potential was successfully introduced into a redox flow battery, and the hybrid V/Mn flow cell with multiple redox couples based on Mn(III)/Mn(II) vs. V(III)/V(II) and V(V)/V(IV) vs. V(III)/V(II) was investigated. The results show that the concentration of sulfuric acid of 4 M is suitable for the viscosity, electrical conductivity, and electrochemical performance. Redox flow battery employing V/Mn and V as positive and negative active species was assembled and the charge-discharge performance was evaluated. The hybrid V/Mn flow cell exhibits good capacity retention and energy efficiency can reach up to 80% over 40 cycles. The energy density of 17.85 W h l−1 is achieved for V/Mn hybrid cell, 25.3% higher than that of all vanadium cell.