Accelerating interfacial charge transfer via spin polarized Ni-doped Co3O4 for high-performance zinc-iron flow batteries

Interfacial charge-transfer critically governs Zn plating/stripping kinetics and determines the electrochemical performance of zinc‑iron flow batteries. However, the regulation of electron-transfer pathways at the spin-level remains unexplored. Herein, we propose a micro-interface spin engineering strategy using Ni-doped spinel Co 3 O 4 as a model catalyst and reveal that the local spin configuration serves as a fundamental descriptor for regulating interfacial electron transfer pathways during zinc deposition. Guided by the Mott two-current model, Ni doping modulates the spin structure of spinel Co 3 O 4 , creating asymmetric spin-dependent channels and establishing a dominant low-resistance spin transport pathway. As a result, Ni-doped Co 3 O 4 markedly lowers the apparent activation energy for interfacial Zn/Zn 2+ charge transfer from 23.61 kJ·mol −1 to 12.79 kJ·mol −1 and exhibits the lowest charge-transfer resistance. The optimized spin-dependent transport pathway further promotes uniform Zn nucleation and surface diffusion, effectively suppressing dendrite formation. Benefiting from these advantages, the zinc‑iron flow battery maintains an energy efficiency above 80% at 100 mA·cm −2 and sustains over 600 cycles with negligible capacity decay. This work establishes a mechanistic framework linking local spin polarization with interfacial electron-transfer pathways, offering new insight into spin-regulated Zn deposition kinetics and providing a rational strategy for designing high-performance zinc-based flow batteries.