3D Heterogeneous Co 3 O 4 @Co 3 S 4 Nanoarrays Grown on Ni Foam as a Binder‐Free Electrode for Lithium‐Ion Batteries

Co 3 O 4 @Co 3 S 4 nanoarrays on Ni foam (abbreviated as Co 3 O 4 @Co 3 S 4 NAs) were prepared by using a facile synthesis method, which involves hydrothermal preparation, low‐temperature thermal decomposition of Co(OH) y (CO 3 ) 0.5(2‐y) ⋅ 11H 2 O, and sulfurization. The material exhibited good electrical conductivity, high specific capacity, and cycling stability with a reversible capacity of 1050 mAh g −1 at 200 mA g −1 after 40 cycles and an initial coulombic efficiency of 82.25 %. At a high current density (1500 mA g −1 ), the capacity reached up to 808.1 mAh g −1 . The excellent lithium‐storage performance of Co 3 O 4 @Co 3 S 4 NAs can be ascribed to the synergistic effect between Co 3 O 4 and Co 3 S 4 , along with the contribution of the Ni foam. The method described in this paper can be extended to enhance the electrochemical performance of other metal oxides.