Magnetic-field-guided catalytic effect mitigates Li₂S passivation of lithium-sulfur batteries

Polysulfides shuttle and Li₂S passivation are considered key problems of lithium-sulfur (Li-S) batteries, seriously hindering sulfur recycling for practical applications. However, the prevailing strategies for introducing electrocatalysts focus mainly on the polysulfides-shuttle effect, whereas Li₂S passivation involving solid conversions with high energy barriers has been rarely studied and remains challenging. Herein, we propose that applying a magnetic field (MF) to weak ferromagnetism α-Fe₂O₃ shows an enhanced effect, not only suppressing the polysulfides shuttle, but also alleviating Li₂S passivation by synchronously catalysing polysulfides conversion and Li₂S deposition/dissociation. Experimental and theoretical studies reveal that the MF can promote the consistent alignment of magnetic-domain orientations in α-Fe₂O₃ and enhance the electron spin polarization of the Fe 3d orbital, which shifts the center of the Fe d-band towards the Fermi level and increases the hybridization degree between Fe 3d and S 3p orbitals in α-Fe₂O₃-Li₂S₆ or α-Fe₂O₃-Li₂S, thus enhancing the adsorption and catalysis of polysulfides and solid products. As a result, after using a 400-mT MF, the α-Fe₂O₃/S cathode shows outstanding cycling stability and excellent rate capability. The research demonstrates that MF-guided electrocatalysis represents an effective solution to the challenging problems of Li-S batteries.