NiFe2O4-Coated Activated Carbon Composite as a Cathode Material for Lithium–Sulfur Batteries

Lithium–sulfur batteries are promising as next-generation rechargeable energy-storage devices because of their high energy density, low cost, and environmental friendliness. However, sulfur cathodes suffer from low specific capacity caused by the poor electrical conductivities of the active materials and fast capacity decay resulting from polysulfide dissolution/shuttling. Herein, we report a facile and low-cost method to solve these problems using an activated carbon (AC)–NiFe 2 O 4 /S hybrid material in which NiFe 2 O 4 is uniformly distributed on AC through a simple wet impregnation method. The AC–NiFe 2 O 4 /S material not only has a strong catalytic effect on sulfur reduction, but also provides strong binding sites to trap polysulfide intermediates. An AC–NiFe 2 O 4 /S electrode shows favorable electrochemical properties including stable reversible capacity (0.24% capacity decay per cycle at 0.1 C, retaining a capacity of 602.7 mAh g −1 after 170 cycles; stable cycling at 0.5 C, retaining a capacity of 501.9 mAh g −1 after 100 cycles), excellent rate performance, and fast electrochemical reaction kinetics compared with those of a reference AC/S electrode, which are attributed to the synergistic effects between NiFe2O4 and AC.