Scaling up Tubular Redox Flow Batteries: Electrode Configuration Effects on Current Distribution and Performance

Redox flow batteries are a promising energy storage technology for mitigating the intermittency of renewable energy sources. Despite certain technologies have progressed to partial commercialization, high system cost remains a barrier to broader adoption. Conventional parallel-plate architectures have provided limited potential for substantial stack cost reduction. Recently, tubular designs have emerged as an alternative, offering improved membrane packing and potential enhanced volumetric performance. In this study, we investigate scaling-up strategies for tubular redox flow batteries and demonstrate that electrode geometry fundamentally alters the appropriate performance metric. Experimental results show that, in single-tube cells, the coaxial design achieves better areal performance than the quasi-coaxial design, primarily due to improved current-distribution uniformity. However, numerical simulations of multi-tubular systems reveal that the quasi-coaxial configuration delivers superior volumetric performance by benefiting from enhanced packing efficiency. These findings emphasize an intrinsic trade-off between areal and volumetric performance and provide new insight into the cost-effective scaling strategy for tubular flow batteries.