Compositeof Carbon And Nanomaterials Electrodeand Their Electrochemical Performances

Combine of carbon and high capacity nanomaterials is an effective strategy to enhance the electrochemical performances of lithium ion batteries (LIBs). There arevarious way that carbon combine with other nanomaterials, such as mixture, carbon coated, carbon loading and so on. In this study, we design a new a new nanostructure for electrode:strain-free ring-shaped core-shell structure; and demonstrated the structure that carbon and electrode materials contact more closely: Ferric chloride-graphite intercalation compounds(FeCl3-GICs); and developed a space-confined nanoreactor strategy to synthesize a new composite material: FeCl2-graphite sandwich composite with Cl doping in graphite layers. The specific contenr is as follows:1. We demonstrated a new structure for electrode:Fe3O4@C core-shell nanorings (R-Fe3O4@C). R-Fe3O4@C were fabricated by a synchronous reduction and carbon deposition process.When tested as anode forlithium ion batteries (LIBs),R-Fe3O4@C exhibitexcellent cycling and rate performance, delivering areversible capacity of923mAh g-1at200mA g-1after160cycles, and632mAh g-1at1000mA g-1. The improved electrochemical performances are attributed to the uniform strain-free ring-shaped core-shell structure of R-Fe3O4@C, which possess the feature of reduced diffusion length for Li-ion, incremental exposed active sites between active materials and electrolytes, and improved structural stability for buffering the volume variation during the Li+insertion/extraction.2. Graphene-wrapped Fe2O3nanorings (RGO/Fe2O3) was synthesized by a facial approach which assembled with graphene and the Fe2O3nanorings precursor through the Colloidal Coagulation Effect at room temperature. The uniform Fe2O3nanorings that prepared by hydrothermal routes were homogeneously distribution and well-warpped by graphene. When tested as anode for lithium ion batteries, RGO/Fe2O3exhibits a high capacity and good cycling stability. This could attribute to the interaction of ring-shaped structure and graphene sheets, which inherit the good kinetic properties of Fe2O3nanorings and enhance the structural integrity with graphene sheets support.3. We demonstrated the structure that carbon and electrode materials contact more closely:Ferric chloride-graphite intercalation compounds(FeCl3-GICs).FeCl3-GICs with the structure ofstage1and stage2were synthesized by the reaction of FeCl3and expanded graphite (EG) in stainless-steel autoclave under air atmosphere. As theanode material for lithium ion batteries, these FeCl3-GICs show high capacity, excellentcycling stability and rate capability. The specific capacity for stage2FeCl3is as high as813mAh g-1at200mA g-1and719mAh g-1at500mA g-1after100cycles. Theextraordinaryelectrochemical performancecanbeattributedtotheunique intercalation structureofthe FeCl3-GICs, which possess the feature ofenhanced electricalconductivity and the increment of surface electrochemical reactivity derived from the increased interlayer spacing of graphite.4. To explore new possibilities for anodes, we have created a FeCl2-graphite sandwich composite with Cl doping in graphite layers (C-Cl/FeCl2/C-Cl) as a new type of anode material for Li-ion batteries (LIBs). This new composite has been prepared from the stage2FeCl3-graphite intercalation compounds through the thermal decomposition FeCl3â†'FeCl2+Cl within the graphite interlayers. Notably, the graphite layers act as the space-confined nanoreactor, which can avoid the fast aggregation of FeCl2crystalsand direct the growth of FeCl2crystals. More importantly, graphite layers can suppress the release of Cl and trap Cl to form C-Cl and an intercalation of Cl in graphite, exhibiting Ï€-electron delocalization effect, which is favorable to increasing the electric conductivity and could be benefit to the storage of Li-ions. As an anode material for LIBs, the C-Cl/FeCl2/C-Cl delivers a reversible capacity as large as1043mAh g-1at a current density of500mA g-1after350cycles, and exhibits almost100%capacity retention after1000cycles at1000mA g-1. The outstanding electrochemical performance could be attributed to the combination of the advantages in this unique sandwich structure and Cl-doping of graphite layers.