| The purpose of this paper is to prepare anode materials for high performance sodium ion batteries,ensuring the material capacity,improving both its cycle performance and rate stability.This research mainly includes the following aspects:firstly,preparing nitrogen and sulfur codoped graphene nanosheets(NS-GNS)though a simple sol-gel method,optimizing the procedure of fabricating graphene.By controlling the heatreatment temperature,graphene nanosheets with proper nitrogen and sulfur dopants as well as superior morphology were obtained.Also,in order to learn its electrochemical performance,NS-GNS was tested in sodium ion half cells.The tests show that the heteroatom-doped graphene has a good cycle and rate performance at the sintering temperature of 750 ℃.The electrode have a relatively high capacity of-300 mAh g-1 at a current density of 0.1 A g-1 and significantly,it can cycle for 10000 cycles almost without no decay at a current density of 1 A g-1.Secondly,in order to further improve the capacity of NS-GNS,N and S codoped graphene nanosheets and the growth of ultrafine cobalt sulfide(CoSx)quantum were integrated into one simple synthesis procedure by adding cobalt salt in the facile sol-gel method to prepare CoSx@NSC nanocomposites.CoSx quantum and NSC reduced the sodium ion diffusion distance,improving the electrochemical performance.The NSC can on the one hand provides lots of active sites for sodium storage and on the other hand,it can protect cobalt sulfide quantum in it and effectively improve both cycle and rate performance of the electrode.Consequently,the CoSx@NSC nanocomposites can deliver a very high capacity of around 600 mAh g-1 as sodium-ion batteries(SIBs)anodes at a current density of 1 A g-1,exhibiting good rate capability with～500 mA h g-1 capacity retained at a large current density of 10 A g-1 and noticeably improved cycle performance.The research in this paper provide new thoughts and perspectives for high-performance anode materials for sodium ion batteries. |
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