Facile synthesis of ZnS nanoparticles decorated on defective CNTs with excellent performances for lithium-ion batteries anode material

Abstract

Zinc sulfide (ZnS) is expected to be a potential replacement of commercial graphite as the anode material for lithium-ion batteries (LIBs) due to its non-toxicity, high theoretical capacity and low cost. Nevertheless, there are still several problems for the application of ZnS during lithium-ion storage process, such as undergoing intercalation/extraction reaction, conversion reaction (ZnS to Zn and LiS2) and alloying reaction (LixZn), which make ZnS exhibit more pronounced polarization and lower reversible capacity at high current density. In order to overcome these problems, in this work we designed a composite (ZnS-CNTs) of etched multi-walled carbon nanotubes (CNTs) and ZnS nanoparticles used as the anode material of LIBs. CNTs were etched in air to obtain rough surfaces with many defects, which could provide many active sites for the growth of ZnS nanoparticles. The ZnS-CNTs composite exhibits high reversible capacity of 451.3 mAh/g after 1200 cycles at a high current density of 5 A/g, and superior rate capability (377.8 mAh/g at 8 A/g). Interestingly, the ZnS-CNTs electrode exhibits the typical specific capacity recovery phenomenon, resulting in an excellent stability during the long-term cycling. SEM images of the ZnS-CNTs electrode materials after different cycles show that the ZnS nanoparticles and CNTs gradually merged together with the increase of cycles, which not only effectively alleviates the structural damage caused by volume change of ZnS in the charge and discharge cycling, but also greatly increases the specific capacity due to the increase of its electrochemical reaction area.