Ferromagnetic Bimetallic Catalysts Enhance the Overall Performance of Lithium–Sulfur Batteries under a Magnetic Field

Sluggish reaction kinetics and severe dendrite growth are two main obstacles that hinder lithium–sulfur batteries (LSBs) from practical applications. Here, unconventionally d–p hybridized ferromagnetic Fe₃M (M = Al, Si, Ga, Ge, Sn) materials are studied as the electrocatalysts and conductive scaffolds for LSBs. This reveals that under a magnetic field, the d–p hybridization can be obviously enhanced via the electron cloud overlap between M and Fe atoms around the Fermi level, thereby leading to highly improved kinetics of the entire Li–S reactions. Furthermore, the magnetic field and magnetized Fe₃M can locally regulate the diffusion pathways of Li⁺ through the Lorentz force, facilitating uniform lithium deposition. With Fe₃Ga as the optimal option, under a magnetic field of 280 mT, the Fe₃Ga@CNF/S cathode delivers specific capacities of 1343.3 and 1091.7 mA h g^–1, respectively, at 0.1C and 3.0C, along with an ultralow capacity decay rate of only 0.0065% for 300 cycles at 10.0C, while the Fe₃Ga@CNF/Li anode maintains a low overpotential of 24.5 mV over 100 days of cycling at 5 mA cm^–2. Consequently, the performances of the Li–S full cell with the Fe₃Ga@CNF/S cathode and the Fe₃Ga@CNF/Li anode are significantly improved, producing a capacity of 1027.1 mA h g^–1 at 0.2C and 657.5 mA h g^–1 at 3.0C, and a Li–S pouch cell with a sulfur loading of 0.146 g delivers a high specific energy density of 317 Wh kg^–1 when tested under the magnetic field.