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Lithium Storage Performance And Mechanism Of 3D Graphene/MoS2 Heterojunction Reinfored Sn-based Lithium Ion Battery Anode

Posted on:2017-07-31Degree:MasterType:Thesis
Country:ChinaCandidate:X H ChaiFull Text:PDF
GTID:2321330515467356Subject:Materials engineering
Abstract/Summary:PDF Full Text Request
Although graphene/Sn based lithium ion battery?LIB?anode materials have been widely studied with excellent lithium storage properties at present,developing graphene/Sn based hybrids with unique structures with higher lithium storage capacity and excellent rate capability is still a great challenge,due to the relatively lower reversible capacity of graphene resulting in an unsatisfactory lithium storage capability of the whole composite system.The unique two-dimensional MoS2 nanoplates matches more perfectly with graphene compared to the zero-demensional particles or one-dimensional nano-structures.Meanwhile,the introduction of MoS2 nanoplates provides more active sites for the decoration of Sn nanoparticles,and also limits their agglomeration and growth to some extent.Besides,as a kind of novel active materials,MoS2 nanoplates with large specific surface area offer more sites for lithium ions storage.Therefore,making ternary composites of graphene,MoS2 nanoplates and Sn NPs is expected to further improve the comprehensive electrochemical performance of the composite electrode by the synergetic effect of the three components.Therefore,this work demonstrated a novel and scalable in situ chemical vapor deposition?CVD?technique followed by reduction process in hydrogen atmosphere using a mixture of citric acid,stannous chloride,ammonium molybdate and thiourea as basic materials and a three-dimensional?3D?self-assembly of NaCl particles as templates for fabricating 3D vertically stacked graphene/MoS2 heterjunction networks anchored with Sn nanoparticles encapsulated with carbon shells?designated as 3D VS-MoS2/GHNS/Sn@C?as superior LIB anode.materials The effects of technical parameters on the composition,structure and morphology of the composites were investigated and the growth principles,electrochemical properties and lithium storage mechanism of 3D VS-MoS2/GHNS/Sn@C electrode were discussed.Our research shows that the steric hindrance effect of self-assembled NaCl particles provide templates for constructing continuous 3D porous carbon network,in which the wall thickness can be adjusted by the control of the adding amount of NaCl within a certain range.During the low-temperature reduction process,the MoS2 nanosheets supported on the graphene surface effectively prevent the agglomeration of Sn droplets,promoting small Sn nanoparticles homogenously anchored on the 3D vertically stacked graphene/MoS2 heterjunction networks.In addition,the in-situ grown graphene/MoS2 heterjunction structures dramatically improve the lithium storage properties of the Sn based anode materials.As a consequence,the optimized 3D VS-MoS2/GHNS/Sn@C hybrid anode exhibits good rate performance?1015.9 mAh g-1 at 0.5C,948.5 mAh g-1 at 1 C,850.9 mAh g-1 at 2 C,779.7 mAh g-1 at 3 C,698.5 mAh g-1 at 4 C and 631.8 mAh g-1 at 5 C,1 C=1A g-1?,high reversible capacity and good cycling stability?a high initial charge capacity of 1464 mAh g-1 was achieved and the capacity maintained 1614 mAh g-1 after 80 cycles at 0.2 A g-1?,confirming the outstanding stability of the ternary composites in high rate tests.The excellent lithium storage capability can be ascribed to the following reasons: the perfectly matched graphene/MoS2 heterjunction,interconnected 3D porous graphene network structure as well as a tightly bonded interface between graphene,MoS2 and Sn NPs.
Keywords/Search Tags:graphene, Sn@C nanoparticles, MoS2 nanosheets, chemical vapor deposition, lithium-ion batteries, anode
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