Comprehensive experimental and computational fluid mechanics analysis of flow channel designs for optimizing zinc–bromine redox flow battery performance

Flow-field optimization in zinc–bromine redox flow batteries (Zn–Br RFBs) requires simultaneous control of electrochemical performance, hydraulic energy consumption, and zinc morphology evolution—an interdependence that is absent in non-deposition flow systems. This study presents a three-dimensional multiphysics model, experimentally validated with a root mean square error (RMSE) of ≤5.61% at 10–30 mA cm −2 , designed to systematically assess the effects of various factors, including channel architecture (interdigitated, parallel, serpentine, and spiral), channel number, width, depth, electrolyte flow rate, and current density, on zinc deposition thickness, zinc regeneration factor (ZRF), energy efficiency, and power-based efficiency. Among the geometries examined, the serpentine design yielded the most uniform zinc deposition, reducing thickness by approximately 10% compared to other configurations, while achieving energy efficiency of 82.7% and power-based efficiency of 95.77% at 20 mA cm −2 and 20 mL min −1 . Increasing the flow rate improved the ZRF due to enhanced stripping completeness; however, it also raised pumping demands, leading to a decline in power-based efficiency under elevated flow conditions—highlighting a morphology–hydraulic trade-off inherent in deposition-based systems. Channel multiplicity showed a regime-dependent trend: single-channel serpentine designs showed favorable regeneration stability at low flow rates, while multi-channel configurations generally reduced hydraulic resistance and improved power-based efficiency at higher flow rates. Reducing channel width from 6.25 mm to 1.25 mm enhanced energy efficiency by 13.48% and improved deposition uniformity, while intermediate widths (2.42 mm) showed superior net performance at high flow rates due to reduced pumping losses. Although channel depth had a relatively minor effect on energy efficiency, with a reduction from 2 to 1 mm changing efficiency by only ~0.5%, deeper channels significantly impacted pressure drop (from 3441.16 to 2484.80 Pa) at an electrolyte flow rate of 60 mL min −1 . In contrast, intermediate depths maintained a balance between regeneration and hydraulic behavior. Additionally, experimental cyclic tests confirmed stable battery performance under cyclic conditions. Compression optimization increased energy efficiency by 18%, with electrode compression rising from 30 to 50%. By integrating zinc thickness evolution, regeneration capability, and power-based efficiency into a unified multi-criteria framework, this study establishes a morphology-aware optimization strategy for metal-deposition redox flow batteries, enabling a balanced design that harmonizes deposition stability with system-level energy efficiency across operating regimes.