Metal Chalcogenides/Grphene Composites Prepared For Energy Storage

Metal chalcogenides(MCs)as anode materials in lithium-ion batteries(LIBs)/sodium-ion batteries(SIBs)have attracted wide attention,because MCs own higher theoretical capacity.However,MCs have some drawbacks,such as a large volume expansion,a poor cycle stability during the discharge/charge process and a poor rate performance.In order to improve its electrochemical performance,the usual strategy has two aspects:on the one hand,reducing the material size and preparing the special morphology nanostructure;on the other hand,using graphene and preparing graphene-based composite nanomaterials.In addition,compared to metal sulfidse,the research of the metal selenides and tellurides is relatively rare,especially tellurides.In this study,CO0.85Se nanosheeets with a thickness of about 5 nm,CoTe2 with a particle size of about 121 nm and Bi2Te3 nanoplates with a particle size of about 350 nm are prepared by solvothermal method,and their graphene composites are prepared by appropriate methods.Through the analysis,we find that between Co0.85Se,CoTe2,Bi2Te3 and graphene have strong interfacial interactions.As an anode material for LIBs,the flexible Co0.85Se nanosheets/graphene film exhibits a high initial reversible capacity of 680 mA h g-1 at 50 mA g-1.As an anode for SIBs,the flexible Co0.85Se nanosheets/graphene film exhibits the initial reversible capacity is 388 mA h g-1 at 50 mA g-1;CoTe2/graphene composite exhibits the high initial reversible gravimetric capacity of 382 mA h g-1 and volumetric capacity of 695.2 mAh cm+3 at50 mAg-1,and after 100 cycles,the gravimetric capacity and volumetric capacity still remain at 356 mA h g-1 and 647.9 mA h cm-3,respectively;Bi2Te3/graphene composite exhibits the high initial reversible gravimetric capacity of 416 mA h g-1 and volumetric capacity of 648.9 mA h cm-3 at 100 mA g-1.In addition,they also exhibit excellent rate performance.Based on these,they have excellent electrochemical performance.The excellent electrochemical performance should be attributed to the special structure of the Co0.85Se nanosheets/graphene film,CoTe2/graphene composite and Bi2Te3/graphene composite:On the one hand,there are the strong interfacial interactions between active materials and graphene in these composites,which can enhance electron transfer.On the other hand,graphene in composites can not only improve the conductivity,but also buffer the volume expansion of the active materials during the charging and discharging process.This project promote the development of LIBs/SIBs anode materials and further promote the application of this kind of materials.