Computational study of effects of contact resistance on a large-scale vanadium redox flow battery stack

Computational models are developed to allow for a deeper understanding of design factors that affect the lifetime of a vanadium redox flow battery (VRFB) stack, particularly related with the contact-resistance issue of end cells in a large-scale stack. A simplified microcontact-resistance model and a physics-based macrocontact-resistance model are constructed to investigate the effect of contact resistance on the performance and longevity of VRFB stacks. A microcontact-resistance model predicts significant heat accumulation in the current-collector plate that can result in irreversible damage of plastic materials and an electrical-voltage loss if the contact resistance is not properly engineered in the stack design. Furthermore, the physics-based macrocontact-resistance model investigates abrupt voltage and current distortion in the bipolar plate that is in imperfect contact with the current collector; this results in the local corrosion of the bipolar plate. To ensure a long lifetime of VRFBs, a stack design with minimal contact resistance (less than 0.1 Ω cm2) is required. The structural design of the endplate as well as the selection of a high-stiffness material is critical to mitigate the bending issue and reduce contact resistance.