NiCo2S4/S Composites Used as Cathode Materials in Lithium-Sulfur Batteries with High Performance

Two kinds of NiCo2S4 with good conductivity, strong polarity and good electrochemical activity were prepared by hydrothermal method. Both served as sulfur host in Li-S batteries and showed outstanding electrochemical performances. By comparison, the importance of structure for high capacity and long cycle stability of lithium-sulfur battery is further illustrated. Application of lithium-sulfur battery has been limited due to polysulfide dissolution, the insulating nature of sulfur and the volumetric strain produced during charge and discharge process. To improve the performance of Li-S batteries, two kinds of bimetallic sulfides of NiCo2S4 with flaky (F-NiCo2S4) and sea urchin-like (S-NiCo2S4) structures were synthesized by using simple hydrothermal method, which were used as sulfur carriers in lithium-sulfur batteries and showed excellent electrochemical properties. At 0.2C, both electrodes of F-NiCo2S4/S and S-NiCo2S4/S have high pristine discharge specific capacities of 986mAhg-1 and 959mAhg-1. At high current density of 4C, the F-NiCo2S4/S electrode still has a high pristine discharge specific capacity of 673mAhg-1 and a coulombic efficiency of 97.00%. The specific capacity can remain at 526mAhg-1 with a low average attenuation of 0.17% even after 130 cycles. The excellent electrochemical performances of the cathode material can be ascribed to the synergistic effect of tubular morphology, good electrical conductivity and strong adsorption ability of NiCo2S4 matrix for polysulfide. The job provides a new scheme and material for application of lithium-sulfur batteries with high performance.