Design,Synthesis And Lithium Storage Of Properties Research Of Transition Metal Oxide (Mo、Co、Fe)/Graphene Nanocomposites

Rechargeable lithium-ion batteries（LIBs）have been widely used in portable electronics,electric vehicles,and stationary energy storage systems.In order to further improve the electrochemical properties of lithium-ion batteries,it has the advantages of long cycle life,high energy density etc,Therefore,the need to invent new electrode materials to improve battery performance.Due to their generally high specific capacity,Transition metal oxides are very promising as anode materials for lithium-ion batteries.However,due to the low conductivity of the transition metal oxide anode material and the Transition metal oxide particles in the lithium-ion battery charge and discharge process is extremely easy to agglomerate,seriously hindered its direct use as a lithium ion battery anode material,on the other hand,due to the perfect graphene Two-dimensional nanostructures and good electrical conductivity.Therefore,this paper combines the advantages of graphene and transition metal oxides,and designs and synthesizes transition metal oxide/graphene nanocomposites for use in lithium-ion batteries.The specific research contents are as follows:（1）A new porous MoO₂-Cu/C/graphene quadruple nanocomposite was designed and synthesized by a facile one-pot chemical precipitation method followed by calcination.As an anode for lithium ion batteries,the porous MoO₂-Cu/C/graphene nanocomposite delivers a high reversible capacity with significantly enhanced cycling stability(1114.8 mAh g^-1 after 100 cycles at 0.1 A g^-1)and rate capability(892.6 mAh g^-1 and 702.2 mAh g^-1 at 1 A g^-1 and 2 A g^-1,respectively).The greatly improved performances could be attributed to the positive synergistic effect of MoO₂nano-octahedrons,Cu,carbon network derived from metal-organic framework,and graphene:the MoO₂ nano-octahedrons as lithium storage active materials,Cu phase as excellent conductor to improve the rate capability,the in-situ electrochemically carbon network as conductor and spacer to improve the rate capability and buffer the volume changes,and graphene as an efficient three dimensional conductive network to further accommodate the volume change of electrode materials.（2）CoFe₂O₄/graphene nanosheets（GNS）nanocomposites derived from bi-metal organic frameworks and graphene oxides were firstly synthesized via a facile one-pot chemical precipitation with subsequent thermal decomposition method.As an anode for lithium ion batteries,the CoFe₂O₄/GNS nanocomposites exhibited an obvious enhancement electrochemical property in terms of a higher discharge capacity of1061.7 mAh g^-1 after 100 cycles at 100 mA g^-1 with 75.1%capacity retention and the excellent reversible capacity of 956.2 mAh g^-1 when the charge-discharge rate returned from 2 A g^-1 to 0.1 A g^-1 after 60 cycles.This enhancement could be attributed to the synergistic effects between Co and Fe oxides,and the graphene nanosheets which could not only accommodate the volume variations of CoFe2O4nanoparticles during cycling,but also improve the contact area between electrolyte and electrodes.