A three dimensional, transient, non-isothermal model of all-vanadium redox flow batteries

A three-dimensional (3-D) transient non-isothermal model of VRFBs is developed by rigorously accounting for the electrochemical reactions of four kinds of vanadium ions (V
²⁺
, V
³⁺
VO
²⁺
and VO
₂
⁺
) and resultant mass and heat transport processes. Particular emphasis is placed on analyzing various heat generation mechanisms, including irreversible and reversible heat generations due to vanadium redox reactions and joule heating arising from the solid electronic and electrolyte ionic resistances. The 3-D model is first validated against voltage evolution curves measured under charging and discharging processes. The model predictions compare well with the experimental data over a wide range of SOCs, and further reveal key electrochemical and transport phenomena inside VRFBs through multi-dimensional contours of solid /electrolyte potentials, species concentration, and temperature. This full 3-D comprehensive VRFB model can be applied to multi-cell stacks in order to find optimal design and operating conditions.