The impact of end plates on the uniformity of electrode compression in Flow Battery stacks for reducing ohmic losses due to contact resistances

Technological development plays a crucial role in the successful realization of large Flow Battery (FB) systems and can significantly contribute to reducing capital costs. FBs represent a sophisticated technology necessitating complicated engineering. In this work a numerical modeling of the mechanical behavior of Vanadium Flow Battery (VFB) stack with COMSOL Multiphysics® has been performed. During VFB stack assembly, it is crucial to apply adequate external pressure to properly seal the cells and prevent leaks, ensuring optimal electrical performance of the battery. Achieving homogeneous compression of the stack helps reduce ohmic losses by establishing effective contact between the cell components and minimizing contact resistance. In particular, this study examines the influence of endplate geometry and bolt configuration on the distribution of contact pressure within an industrial scale VFB stack. The pressure is applied using metal end-plates secured with bolts. The thickness of the endplates, along with the number and placement of bolts, is optimized to achieve uniform contact pressure across the active area. This research offers a framework for the optimal mechanical design of VFB stacks. More generally, the same analysis can be applied to all Fuel Cell (FC) reactors utilizing the stack configuration outlined below.