Preparation and Structural Investigation of CuCl_2 Graphite Intercalation Compounds

Superfine graphite powder was prepared by ball-milling exfoliated graphite containing anhydrous CuCl2 in planetary ball milling systems. Nano-scale CuCl2 graphite intercalation compounds were synthesized by heating a mixture of anhydrous CuCl2 and graphite nanosheets. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and high-resolution transmission electron microscopy were performed to characterize the microstructures of stage-1 nano-scale CuCl2 graphite intercalation compounds. The structure and components of the domain wall and core in the nano-scale CuCl2 graphite intercalation compounds are described. The results show that the content of CuCl2 in the mixture plays a crucial role in the size of the nano-scale CuCl2 graphite intercalation compound.

Electrical Properties of Expanded Graphite Intercalation Compounds

The intercalation compounds of CuCl2 were synthesized with expanded graphite, whose magnitude of the electrical conductivity is about 10(3)S(.)cm(-1). Their electrical conductivity is 3 similar to6 times as high as that of the expanded graphite, and about 10 times as high as that of GIC made of the non-expanded graphite. The microanalysis results of chemical compounds by X-ray energy spectrum scanning of TEM testified that the atomic ratio of chloride and cupric is nonstoichoimetric. The multivalence and exchange of electrovalence of the cupric ion was confirmed by the XPS-ESCA. Vacancy of chlorine anion increases the concentration of charge carrier. The special stage structure, made of graphite and chloride, produces a weak chemical bond belt and provides a carrier space in the direction of GIC layer. These factors develop the electrical properties.

Synthesis of NdCl_3-FeCl_3-Graphite Intercalation Compounds

NdCl3-FeCl3-graphite intercalation compounds were synthesized by means of molten salt-exchange method.Their layer structure and the relative content of the elements were investigated by X-ray diffraction, scanning electronmicroscopy and energy dispersive X-ray spectroscopy. The results show that the products are mixtures of 2, 3,4-stages,among them, the c-axis repeat distance, Ic, of stage-3 NdCl3-GIC is 1. 6536±0. 0024 nm. In addition, the mechanismof RECl3 intercalation reaction was discussed.

Study of NdCl_3-FeCl_3-Graphite Intercalation Compounds by X-Ray Photoelectron Spectroscopy

NdCl 3 FeCl 3 graphite intercalation compounds were synthesized by molten salt exchange method. The state of the intercalates and the relative contents of Nd, Fe, Cl, C in the product were determined by X ray photoelectron spectroscopy(XPS). From the XPS data, it is concluded that the binding energy of Fe2p electrons is about 711 20～710 3 eV, the binding energy of Nd3d electrons is about 983 08～983 20 eV, and Fe in the product has two valence states (Fe 3+ and Fe 2+ ).

Electronic Effect of Carbon Support on Pt Catalyst Supported on Graphite Intercalation Compound

Graphite intercalation compounds（GIC） were tested as an experimental model for studying the electronic effect of carbon support on the catalytic activity and poisoning tolerance of Pt catalyst for direct methanol fuel cells. The GIC samples with different intercalation degrees were prepared by electrolyzing graphite flake in H2SO4 for varying the periods of time. The GIC-supported Pt catalyst was deposited electrochemically. The catalytic activity and poisoning tolerance of the GIC-supported Pt catalysts were evaluated. It was found that GIC with sulfate anion as intercalate was able to catalyze methanol electrooxidation, which could be related to the positive charges generated on the graphite layer upon intercalation. As intercalation degree increased, the catalytic activity of the GIC-supported Pt catalyst decreased while the poisoning tolerance improved. This suggests that electron donation from support to catalyst had great effect on both catalytic activity and poisoning tolerance of Pt catalyst. And intercalation can be adopted as another important way to make modification on carboneous catalyst support.

Doping inhomogeneity and staging of ultra-thin graphite intercalation compound flakes probed by visible and near-infrared Raman spectroscopy

When ultra-thin graphite intercalation compounds（GICs） are deposited on the SiO2/Si substrate, it is found that their colors are dependent on the thickness of GIC flakes. The sample colors of ultrathin GIC flakes can no longer provide qualitative information on the stage index. Here, multi-wavelength Raman spectroscopy is thus applied to study the doping inhomogeneity and staging of ultra-thin GICs by FeCl3 intercalation. The G band intensity of stage-1 GIC flakes is strongly enhanced by 532-nm laser excitation, while that of stage-2 and stage-3 flakes exhibits strong intensity enhancement for 785-nm laser excitation. The near-infrared lasers are suggested to probe the doping inhomogeneity and staging of ultra-thin GIC flakes.

STUDY ON THE MICROSTRUCTURE OF Fe-KCI GRAPHITE INTERCALATION COMPOUND

The intercalatants presence of Fe-KCl graphite intercalation compound (Fe-KCl G/C) is in the form of independent crystalline phase. In this paper, its distribution in the carbon interlayer, crystalline status and powder sizes have been studied by X-ray diffraction (XRD) , small angle X-ray scattering (SAXS) and transmission electron microscope (TEM). And the partial crystal structure of the GIC has been researched too.

A PRELIMINARY STUDY ON THE STABILITY OF TERNARY CoCl_2-FeCi_3 GRAPHITE INTERCALATION COMPOUNDS

The ternary CoCl2-FeCl3 graphite intercalation compounds (CoCl2-FeCl3 G/C) have been subjected to different treatments in various media. It is found that the CoCl2-FeCl3 GIC is stable 'when it is stored under conditions of opening to at-mosphere,whereas,acids,NaOH,boiling water,and heat treat-ments have different effects on the stability of the CoCl2-FeCl3 G/C.

In‐situ structural characterizations of electrochemical intercalation of graphite compounds

Graphite carbon has been successfully used for the anode materials of secondary ion batteries due to its capability of accommodating ions between graphite layers.The intercalation dynamics intrinsically determine the performance of the batteries.In this review,we summarize recent research progresses of structural characterizations on graphite intercalation in electrochemical devices,especially on the in‐situ study on the intercalations of Li/Na/K ions,AlCl4−and other anions,or solvents.These techniques,including X‐ray,electron microscopy,Raman,neutron scattering,nuclear magnetic resonance,and optical microscopy provide direct information of the reaction dynamics and help to understand the factors affecting the electrochemical performances of metallic ion batteries.

Electrochemically triggered decoupled transport behaviors in intercalated graphite:From energy storage to enhanced electromagnetic applications

Pyrolytic graphite (PG) with highly aligned graphene layers,present anisotropic electrical and thermal transport behavior,which is attractive in electronic,electrocatalyst and energy storage.Such pristine PG could meeting the limit of electrical conductivity (~2.5×10^(4) S·cm^(−1)),although efforts have been made for achieving high-purity sp^(2) hybridized carbon.For manipulating the electrical conductivity of PG,a facile and efficient electrochemical strategy is demonstrated to enhance electrical transport ability via reversible intercalation/de-intercalation of AlCl_(4)^(-)into the graphitic interlayers.With the stage evolution at different voltages,variable electrical and thermal transport behaviors could be achieved via controlling AlCl_(4)^(-)concentrations in the PG because of substantial variation in the electronic density of states.Such evolution leads to decoupled electrical and thermal transport (opposite variation trend) in the in-plane and out-of-plane directions,and the in-plane electrical conductivity of the pristine PG (1.25×10^(4) S·cm^(−1)) could be massively promoted to 4.09×10^(4) S·cm(AlCl_(4)^(-)intercalated PG),much better than the pristine bulk graphitic papers used for the electrical transport and electromagnetic shielding.The fundamental mechanism of decoupled transport feature and electrochemical strategy here could be extended into other anisotropic conductive bulks for achieving unusual behaviors.

Localized-domains staging structure and evolution in lithiated graphite

Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalation compounds with intriguing staging structures,which however are still unclear,especially in their nanostructure and dynamic transition mechanism.Herein,the nature of the staging structure and evolution of the lithium(Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale.The intercalated Li‐ions distribute unevenly,generating local stress and dislocations in the graphitic structure.Each staging compound is found macroscopically ordered but microscopically inhomogeneous,exhibiting a localized‐domains structural model.Our findings uncover the correlation between the long‐range ordered structure and short‐range domains,refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite,and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering.

Structure model and synthesis of NdCl_3-FeCl_3-graphite intercalation compounds

The distribution of the elements and microstructure of NdCI3-FeCI3-graphite intercalation compounds (GICs) were shown by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that Nd element intercalates into graphite, forming NdCI3-FeCI3-GICs, and the distribution of Nd and Fe is nearly even. On the basis of the data, a structure model for RECI3-GICs was founded, and the characteristic layer distance and the index of interval energy were calculated. The calculated results agree with experimental ones, and the relative errors are ±2%. Thus it can be seen that the (111) face is optimal direction for intercalation reaction of TbCl3-LuCl3, and the (001) face is that for LaCl3-GdCl3, because of the lowest interval energy.

Characteristics and Microstructure of Graphite Encapsulated Iron Nanoparticles

The graphite encapsulated a-Fe particles were prepared by reduction of stage-2 and stage-3 FeCI3 graphite intercalation compounds （GICs） with metallic potassium, X-ray diffraction analysis （XRD）, energy dispersive X-ray spectroscopy （EDS） investigation and transmission electron microscopy （TEM） observation show that the reduction products of stage-2 FeCl3-GICs contains more abundant a-Fe nanoparticles than those of stage-3. High-resolution TEM （HRTEM） observation reveals that the nanoparticle of a-Fe was polycrystals or twins, which was real or quasi two-dimension in shape, and whose space orientation was strictly controlled by the graphene. Based on the experiment results, a possible growth model of the graphite encapsulated ct-Fe was proposed.

Intercalation behavior of spiro-bipyrrolidinium cation into graphite electrodes from ethylene carbonate

The intercalation behavior of spiro-(1,1)-bipyrrolidinium cation(SBP+) into graphite electrode from spiro-(1,1)-bipyrrolidinium tetrafluoroborate-ethylene carbonate(SBPBF4-EC) solutions is investigated by conventional electrochemical tests and in situ X-ray diffraction measurements. Two kinds of graphite intercalation compounds(GICs) with discrete characteristic intercalated gallery heights(IGHs)(ca. 0.95 and0.75 nm) can be obtained with varying the salt concentration. The effect of graphite type is also addressed.

STRUCTURAL DESIGN OF X-RAY REFLEXIBLE MATERIALS—METAL—GIC

In this paper, computer simulation computation is used to investigate effects of the compositions and structure on reflective property of metal-graphite intercalation compounds which are X-ray reflexible ma-terials . The investigation provides effective means for structural design of high-reflectivity metal-GIC which meets various demands. The results show that metal-GIC have good reflective property on X-ray and are a kind of promising and new type X-ray reflexible materials.

Optimal charge inhomogeneity for the d+id-wave superconductivity in the intercalated graphite CaC_(6)

The coexistence of superconductivity and charge inhomogeneity was observed in many cuprate superconductors.The relationship between those two is still controversial.Similarly,in the graphene sheets of the intercalated graphitic superconductor CaC_(6),the charge inhomogeneity was also observed.We simulate such a system by constructing the Hubbard model on the honeycomb lattice with charge inhomogeneity imposed by force.Utilizing the finite-temperature determinant quantum Monte Carlo algorithm,we examine the relationship between the superconducting pairing and the charge inhomogeneity.An optimal charge inhomogeneity for the d+id-wave pairing is found.While for other artificial charge inhomogeneities,the d+id-wave pairing is monotonically suppressed.The possibleπ-phase shift induced by charge inhomogeneity is also examined.

Nb_(2)O_(5) nanocrystals decorated graphene composites as anode materials for high-performance dual-ion batteries

Niobium oxide(Nb_(2)O_(5))is a promising material in photocatalytic,solar cell,electronic like electron field emitters,and especially lithium-ion batteries(LIBs)because of its adjustable morphologies,controllable crystal type,stable structure,and environmental friendliness.However,its low electrical conductivity lowers the rate performance and limits the practical applications in LIBs.Herein,we present a one-step solid-state synthesis of orthogonal Nb_(2)O_(5) nanocrystals/graphene composites(Nb_(2)O_(5)/G)as high-performance anode materials in LIBs.Benefiting from the nanoscale crystalline structure Nb_(2)O_(5) and highly-conductive graphene substrate,the as-prepared Nb_(2)O_(5)/G exhibits excellent electrochemical performances.Impressively,a reversible structural phase transition between orthogonal Nb_(2)O_(5) and tetragonal Li1-xNbO_(2)(0<x<1)was verified by ex-situ transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).After coupling with graphite cathode based on PF6-intercalation/deintercalation mechanisms,Nb_(2)O_(5)/G||graphite dual-ion batteries(DIBs)full cell delivers good electrochemical performance in terms of cyclic performance and rate capability.We believe this work can provide a clear route towards developing advanced transition metal oxide/graphene composite anode and a comprehension of its electrochemical reaction mechanism.