Dual-Field Amplification via Nanotip-Engineered Catalysts for Efficient Spin-State and Ion Regulation in...

Modulating the electronic structure of catalysts through external magnetic fields is a promising strategy for enhancing electrocatalytic activity, which has been successfully demonstrated in the oxygen evolution reaction (OER), zinc-air batteries and lithium-sulfur batteries. However, conventional magnetic regulation approaches typically focus solely on spin-state modulation, neglecting the ion transport limitations in practical systems. Additionally, existing permanent magnets and ferromagnetic additives generate magnetic fields with limited intensity and nonuniform directionality, restricting their effectiveness. Herein, we propose a tip-enhanced magnetic-electric dual-field strategy by rationally designing ferromagnetic NiCo₂O₄ catalysts with nanotip architectures to address long-standing kinetic bottlenecks in aluminum-sulfur (Al-S) batteries. Finite element analysis demonstrates that the high-curvature tips significantly amplify local electric and magnetic fields by approximately 4.2- and 2.6-fold, respectively, under an external field. Moreover, the induced spin-state transition of Ni³⁺ to high-spin (HS) states enhances d-p orbital hybridization with polysulfide intermediates, effectively lowering reaction barriers. This dual enhancement synergistically promotes ion transport via magnetohydrodynamic (MHD) effects, leading to substantially reduced voltage hysteresis and markedly improved electrochemical performance, delivering a high reversible capacity of 513 mAh g^-1 after 700 cycles in Al-S batteries. By integrating geometric field amplification with spin-state modulation, this work presents a highly efficient and scalable strategy for approach to designing high-performance catalysts for advanced Al-S batteries.