Aqueous zinc-based flow batteries have received considerable attention for large-scale energy storage due to their low cost, high safety and readily available raw materials. However, zinc dendrite shortens the cycle life, and limited zinc deposits at anodes reduce their capacity. Herein, we design a semi-solid reactor with 3D interconnected electron-ion networks to achieve high areal capacity and uniform distribution of reactive zinc. Multi-layered graphitic felt builds abundant avenues for electron transfer, and zinc slurry offers massive ions transfer channels. The kinetic resistance is 21.5 Ω cm-2, about one-twentieth of that in flood zincate solutions. The capacity is up to 100 mAh cm-2, which is among the highest values in zinc-based flow batteries. The assembled zinc-iron flow battery delivers high coulomb efficiency of 100% and energy efficiency of 85%. Additionally, zinc-iron flow batteries show outstanding cycle stability over 580 hours without performance degradation.