The Structure Design And Property Study Of Hollow Carbon Composite Tungsten Disulfide Anode Materials

Tungsten disulfide?WS₂?,which has a layered structure similar to graphene,has received more attention in a growing number of fields,offering more possibilities for the development of semiconductor,photodetector,electrocatalysis,photocatalysis and energy storage.When used as an anode for lithium-ion battery?LIBs?,WS₂ has the advantages of high theoretical specific capacity(433 mAh g^-1),wide operating temperature range and large interlayer space,etc.,but the large volume expansion and bad electronic conductivity seriously limit the development of WS₂ anode material.In order to improve the shortcomings of WS₂,two kinds of WS₂-based composites with different structures were designed and prepared to be used as anode for LIBs.Meanwhile,the improvement mechanism of the structure design on the electrochemical properties of WS₂-based materials was studied,and the performance of its electrochemical lithium storage was studied.By skillfully designing the“double-sided protective”structure,WS₂ nanosheets in situ grow on reduced graphene oxide hollow spheres?Hs-rGO?.Then nitrogen doped graphene?NG?is coated on the outer layer to obtained NG@WS₂@Hs-rGO.Double-sided protective structure of NG@WS₂@Hs-rGO is successfully fabricated via a facile synthesis strategy.When evaluated as an anode material for LIBs,at a high current density of 1000 mA g^-1,the NG@WS₂@Hs-rGO anode delivers a discharge capacity of 300.9 mAh g^-1 after 320 cycles.The capacity retention of the electrode material reaches as high as 106%of the discharge capacity after the 10^thh cycle.Internally,the elastic Hs-rGO provides space for the bulk expansion of WS₂.Externally,the outer layer of WS₂ coated with NG not only improves the conductivity,but also provides more active sites for Li⁺storage.The double-sided protective structure makes NG@WS₂@Hs-rGO a potential anode for light and high-performance LIBs.By properly designing the“three-layer shell”battery structure,NG,WS₂ and porous carbon shell?PCS?can play an effective synergistic role.PCS,as a template with rich functional groups,promotes the growth of WS₂ nanosheets under hydrothermal conditions.The outer NG coating layer effectively reduces the side reaction between the WS₂ and the electrolyte.At the same time,NG provides more active sites for Li⁺and Na⁺intercalation and thus enhances conductivity.For LIBs,the capacity of PCS/WS₂/NG anode can reach 324.7 mAh g^-1 after long cycling for510 cycles at a high current density of 2000 mA g^-1.For sodium-ion batteries?SIBs?,at the high current density of 500 mA g^-1,the PCS/WS₂/NG anode delivers a discharge capacity of 205.0 mAh g^-1 after the 900^th cycle.PCS/WS₂/NG anode shows very stable electrochemical performance.The distinctive structural characteristics and excellent electrochemical performance of PCS/WS₂/NG nanocomposite make it a promising anode material for the next-generation high performance batteries.