Synthesis And Li-ion Storage Performance Of Graphene/Tin-based Nanocomposites

Lithium ion battery（LIB） has not only been widely used in portable electronic devices, but also been the main power source for applications in new energy vehicles. However, Graphite used as the anode material in commercial LIBs can not meet the demand of high energy and power density. Tin-based materials such as tin metal and its alloys, oxide and sulfide can exhibit much higher capacity than graphite, but they suffer from rapid capacity decay during the electrochemical cycling due to the large volume variation. High performance anode materials with high energy density, excellent cycle stability and rate capability are higly desired. Several kinds of graphene/tin-based nanocomposites were constructed in this work, and their structure and lithium storage performance were characterized in detail.（1） SnO₂/r GO nanocomposites were fabricated by a combination of sol- gel and solvothermal method using SnC l₄·5H₂O and graphene oxide（GO） as the raw materials. SnO₂ nanocrystals with an average size of 6.6 nm were uniformly dispersed on the surface of reduced graphene oxide（r GO） nanosheets. When evaluated as an anode of LIB, the SnO₂/rGO composites exhibited superior Li- ion storage performance with a high capacity, excellent cyclying stability and rate performance. A high capacity of 1019 mAhg^-1 was achieved after 280 cycles at a current density of 500 mA g^-1, it still remained at 655 mAh g^-1 even at a high current density of 5000 mA g^-1.（2） SnS₂/r GO nanocomposites were synthesized by refluxing an aqueous solution of GO, SnC l₄·5H₂O and thioacetamide with subsequent heat treatment. When used as an anode material, the SnS₂/rGO nanocomposites delievered a high capacity of 836 mAh g^-1 after 100 cycles at a current density of 200 mA g^-1. They could exhibit a reversible capacity of 432 mAh g^-1 even at a high current of 5000 mA g^-1.（3） SnO₂/SnS₂/rGO nanocomposites were prepared by a combination of sol- gel and solvothermal method using SnC l₄·5H₂O, GO and thiourea as the source mateirals. As an anode material, the SnO₂/SnS₂/rGO nanocomposites exhibited high reversible capacity of 1243 mAh g^-1 at a current density of 200 mA g^-1 after 100 cycles. When they were discharged and charged for 150 cycles at 1000 and 2000 mA g^-1, they could deliever 1058 and 834 mAh g^-1, respectively. The capacity could remain at 603 mAh g^-1 even at a high current density of 5000 mA g^-1, showing excel ent rate performance.（4） GO-melamine-cyanuric acid Polymer was first synthesized from the reaction of GO, melamine, and cyanuric acid. MoO₂/N-doped graphene nanosheets（MoO₂/NG） were then obtained by pyrolysis of molybdenum salt adsorbed on the GO-melamine-cyanuric acid polymer in flowing inert gas atomosphere. As the anode of LIB, the MoO₂/NG nanocomposites exhibited a good cycling performance with a high reversible capacity of 753 mAh g^-1 at a current density of 500 mA g^-1 after 400 cycles, and great rate performance with a capacity of 394 mAh g^-1 at 2000 mA g^-1.