Magneto‐Electrodeposition and Field‐Enhanced Ion Transport in Zn‐MnO 2 Batteries

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) are promising alternatives to lithium‐ion systems for safe and low‐cost energy storage; however, their practical application is limited by poor cyclability, cathode degradation, and sluggish kinetics. Here, we introduce a magnetic‐field‐assisted electrodeposition strategy, termed magneto‐electrodeposition (MED), to fabricate MnO 2 cathodes. The applied magnetic field induces Lorentz‐force‐driven magnetohydrodynamics, enhancing Mn 2+ ion transport and enabling the formation of uniform and robust MnO 2 coatings with enhanced δ‐MnO 2 character. Structural analyses confirm that, through the MED approach, MnO 2 depositions with higher Mn content (14.6%) and mass loading (26.6%) are obtained compared to conventional electrodeposited cathodes. Electrochemical characterization revealed improved charge‐transfer kinetics, with ∼95% reduced interfacial resistance (R ct ). The optimized MED MnO 2 cathode delivered an initial areal capacity of 0.62 mAh cm − 2 , nearly twice the conventionally electrodeposited cathode, with 73% capacity retention after 100 cycles. Introducing an internal magnetic field during operation further enhances performance, with 10 mT being optimal for improving Zn 2 + transport. Consequently, the Zn‐MnO 2 cell employing the MED cathode delivers stable cycling for ∼315 cycles, outperforming the conventionally electrodeposited cathode, which fails after ∼130 cycles. This work demonstrates that coupling magneto‐electrodeposition with in‐operando magnetic‐field‐assistance provides a scalable strategy to engineer cathodes and regulate ion transport for high‐performance AZIBs.