MoS₂-based Composite Anodes For Lithium Ion Battery And Their Electrochemical Performance

Molybdenum disulfide（Mo S₂）as a typical two-dimensional（2D）transition metal sulfide,has attracted intense attention as anodes of lithium-ion batteries（LIBs）due to the unique 2D layered structure and high theoretical capacity(669 mAh g^-1).However,due to the high surface energy and interlayer van der Waals attraction,restacking of 2D nanosheets is almost inevitable.In addition,dramatic change in volume will lead to structural instability during the charge-discharge process,and thus deteriorates the performance of Mo S₂.One of the effective approaches is combining Mo S₂ nanosheets with stable substrate（such as TiO₂）.Another approach is assembling pristine 2D nanosheets into three-dimensional（3D）hierarchical architectures which could effectively preserve the individual nanosheets with largely exposed surface area,thus realizing the full merits of 2D nanomaterials.Furthermore,as semiconductor,the low intrinsic electric conductivity could lead to poor cyclability and rate capability.In order to address the issue,integrating Mo S₂ nanostructure with carbon material has received special interests.This work demonstrated a novel and scalable chemical vapor deposition（CVD）method using a mixture of ammonium molybdate,thiourea and glucose as starting materials for fabricating carbon and single-layer Mo S₂ nanosheets co-modified TiO₂nanocomposites（defined as Mo S₂-C@TiO₂）as superior LIBs anode materials.The effects of technical parameters on the structure and morphology were investigated,and the growth principles,electrochemical properties and lithium storage mechanism of MoS₂-C@TiO₂ electrode were discussed.The results show that the Mo S₂-C@TiO₂nanocomposites exhibit markedly enhanced lithium storage capability compared with pure TiO₂.The specific capacity can maintain 160 mAh g^-1 at a high current density of 1 C(1 C=167 mA g^-1)even after 300 discharge/charge cycles,indicating the great potential of the Mo S₂-C@TiO₂ on energy storage.In addition,hierarchical porous flower-like structures constructed from Mo S₂/C nanosheets（denoted as Mo S₂/C-HPF）have been successfully synthesized through a facile one-pot hydrothermal method by using CS₂ as soft-template and PVP as surfactant.The Mo S₂/C-HPF shows high capacity(940 mAh g^-1 at 220th cycle at 0.1A g^-1)when evaluated as LIBs anode,which shows excellent structure stability.The excellent cycling capability can be ascribed to the structure superiority and synergistic effect of Mo S₂/C:hollow/porous hierarchical Mo S₂ would facilitate electrolyte infusion,shorten Li⁺diffusion pathway and significantly buffer volume change during cycling,and carbon improves the overall electronic conductivity.In order to further increase the rate performances,carbon nanotubes（CNTs）was introduced to increase the electronic conductivity of the nanocomposites.The experimental results show that the Mo S₂/C-HPF-CNTs composites exhibit enhanced rate performance(693 mAh g^-1at 0.1 A g^-1,621 mAh g^-1 at 0.2 A g^-1,539 mAh g^-1 at 0.5 A g^-1,478 mAh g^-1 at 1 A g^-1,422 mAh g^-1 at 2 A g^-1,respectively),which could be attributed to the carbon nanotubes joining the Mo S₂ nanoflowers,shortening the diffusion distance of both electrons and ions.