Ball-milling synthesis of ZnO@sulphur/carbon nanotubes and Ni(OH)2@sulphur/carbon nanotubes composites for high-performance lithium-sulphur batteries

Zinc oxide wrapped sulphur/carbon nanotubes (ZnO@S/CNT) and nickel hydroxide wrapped sulphur/carbon nanotubes (Ni(OH)2@S/CNT) nanocomposites are prepared using a simple, low cost and scalable ball-milling method. As the cathodes in Li-S batteries, the as-prepared ZnO@S/CNT composite illustrates a superior high initial capacity of 1663 mAh g−1 at a charge/discharge rate of 160 mA g−1, and maintains a reversible capacity at approximately 942 mAh g−1 after 70 cycles. While for Ni(OH)2@S/CNT composites, its initial capacity is also as high as 1331 mAh g−1, but a poorer cycling stability is presented. When the charge/discharge current is increased to 1600 mA g−1, a high reversible capacity of 698 mAh g−1 after 200 cycles still can be obtained for the ZnO@S/CNT composite, far better than that of Ni(OH)2@S/CNT composites. The better cycling performance and high discharge capacity can be attributed to the strong interactions between ZnO and Sx2− species, which is verified by the density functional theory (DFT) calculation result that the ZnO exhibits a higher adsorption energy for Li2S8 than the Ni(OH)2.