The intercalation compounds of CuCl2 were synthesized with expanded graphite, whose magni-tude of the electrical conductivity is about 103S.cm1. Their electrical conductivity is 3-6 times as high as that of the expand...The intercalation compounds of CuCl2 were synthesized with expanded graphite, whose magni-tude of the electrical conductivity is about 103S.cm1. Their electrical conductivity is 3-6 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 nonstoichoi-metric. 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.展开更多
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 ...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.展开更多
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 ele...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.展开更多
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 ph...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+ ).展开更多
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 cond...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.展开更多
Rare-earth oxide graphite intercalation compounds (CeO-GICs) were prepared using graphite and CeOas raw materials by vacuum heat-treatment. The stage-5 GICs was formed after heat treatment at 800 ℃, and it was examin...Rare-earth oxide graphite intercalation compounds (CeO-GICs) were prepared using graphite and CeOas raw materials by vacuum heat-treatment. The stage-5 GICs was formed after heat treatment at 800 ℃, and it was examined and characterized by X-ray diffraction (XRD). The XRD analysis of intercalation compounds indicated that a number of non-carbon reactant (atom, molecule, ion or groups) could intercalate the layers of graphite with reticulated layer structure physically. Consequently the layered structure of graphite changed and new physical and chemical properties were obtained. X-ray photoelectron spectroscopy (XPS) suggested that the compound intercalated into graphite should contain CeⅣ compounds.展开更多
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 ...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.展开更多
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 intercalati...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.展开更多
Graphite is a universal host material for ion intercalation. Li+-graphite intercalation compounds (GICs) have been successfully utilized as the anode material in commercial lithium-ion batteries.Similarly, anion-graph...Graphite is a universal host material for ion intercalation. Li+-graphite intercalation compounds (GICs) have been successfully utilized as the anode material in commercial lithium-ion batteries.Similarly, anion-graphite intercalation compounds (AGICs) have been coming into their own in dual-ion batteries [1]. It is imperative to deepen an understanding of anion storage mechanisms in graphite electrode.展开更多
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 mee...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.展开更多
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 ca...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.展开更多
Composites based on ultradispersed polytetrafluoroethylene and intercalated graphite oxide compounds with dodecahydro-closo-dodecaborates and methods of their fabrication have been developed. The fabricated composites...Composites based on ultradispersed polytetrafluoroethylene and intercalated graphite oxide compounds with dodecahydro-closo-dodecaborates and methods of their fabrication have been developed. The fabricated composites have been characterized using XRD analysis, and optical microscopy. These composites are distinguished with completeness of their combustion, since the combustion products comprise gaseous boron fluorine-containing compounds of boron, boron trifluoride (BF3), and boron oxyfluoride ((BOF)3). Besides, these composites are characterized with increased energy capacity as compared to purely oxygen-containing compounds, since the heat of formation of boron fluorine-containing compounds is higher than that of boron oxide. Introduction of ultradispersed polytetrafluoroethylene imparts composites with hydrophobicity, thus improving their functioning properties.展开更多
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 fu...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.展开更多
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 powd...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.展开更多
FeCI3-intercalated graphite intercalation compounds (GICs) with high reversible capacity and high volumetric energy density are attractive anode material alternatives of commercial graphite. However, the rapid capacit...FeCI3-intercalated graphite intercalation compounds (GICs) with high reversible capacity and high volumetric energy density are attractive anode material alternatives of commercial graphite. However, the rapid capacity decay, which was induced by chloride dissolution and shuttling issues, hindered their practical application. To address this problem, here, we introduce flake-like Fe2O3 species with inherently polar surface on the edge of FeCl3 -intercalated GICs through microwave-assisted transformation of a fraction of FeCl3 component. Theoretical simulations and physical/electrochemical studies demonstrate that the introduced Fe2O3 component can afford sufficient polar active sites for chemically bonding the soluble FeCl3 and LiCl species based on the polar-polar interaction mechanism, further inhibiting the outward diffusion of the chlorides and immobilizing them within the GIC material. In a lithium ion cell, the FeCl3 -intercalated GIC with a suitable Fe2O3 content shows remarkably improved cycling stability with a high reversible capacity of 1,041 mAh·g^-1 at a current density of 200 mA·g^-1. Capacity retention of 91 % is achieved at a high current density of 1,000 mA·g^-1 over 300 cycles. This work opens up the new prospect for immobilizing chlorides by introducing inorganic species in GIC for long-cycle electrochemical batteries.展开更多
The laws of forming metal- ammonia- graphite biintercalation compound (MAGBC ) undr natural or electrolytic conditions were studied by selecting microstructural parameter functions in accordance with the chemcal bond ...The laws of forming metal- ammonia- graphite biintercalation compound (MAGBC ) undr natural or electrolytic conditions were studied by selecting microstructural parameter functions in accordance with the chemcal bond theory, and function Φ(g) was proposed to characterize the capability of metal-liquid ammonia solutions to be interalated and the relevant laws were thus summed up together with structural paramter diagrams. Results in general agreement with experimental facts, and some expected results without experiment reports as well, were obtained and satisfactorily explained from the view point of energy.展开更多
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 th...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.展开更多
Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1...Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1/2)a_0 x a_0 superstructure is formed, aregiven, and the results are in good agreement with the experiments and theoretical calculations. Therelationship between critical temperature and M-ion-vacancy interaction parameter is linear.展开更多
Aluminum storage systems with graphite cathode have been greatly promoting the development of state-of-the-art rechargeable aluminum batteries over the last five years;this is due to the ultra-stable cycling,high capa...Aluminum storage systems with graphite cathode have been greatly promoting the development of state-of-the-art rechargeable aluminum batteries over the last five years;this is due to the ultra-stable cycling,high capacity,and good safety of the systems.This study discussed the change of electrochemical behaviors caused by the structural difference between flake graphite and expandable graphite,the effects of temperature on the electrochemical performance of graphite in low-cost AlCl_(3)-NaCl inorganic molten salt,and the reaction mechanisms of aluminum complex ions in both graphite materials by scanning electron microscopy,X-ray diffraction,Raman spectroscopy,cyclic voltammetry,and galvanostatic charge-discharge measurements.It was found that flake graphite stacked with noticeably small and thin graphene nanosheets exhibited high capacity and fairly good rate capability.The battery could achieve a high capacity of^219 mA·h·g^(-1) over 1200 cycles at a high current density of 5 A·g^(-1),with Coulombic efficiency of 94.1%.Moreover,the reaction mechanisms are clarified:For the flake graphite with small and thin graphene nanosheets and high mesopore structures,the reaction mechanism consisted of not only the intercalation of AlCl4^-anions between graphene layers but also the adsorption of Al Cl4^-anions within mesopores;however,for the well-stacked and highly parallel layered large-size expandable graphite,the reaction mechanism mainly involved the intercalation of AlCl4^-anions.展开更多
Exfoliated graphite was prepared by chemical route and then further subjected to thermal oxidation and sonication for size reduction and increased interlayer spacing in natural flake graphite. Exfoliated graphite/ABS ...Exfoliated graphite was prepared by chemical route and then further subjected to thermal oxidation and sonication for size reduction and increased interlayer spacing in natural flake graphite. Exfoliated graphite/ABS composites were pre-pared with varying filler concentration by solution casting method. Exfoliated graphite and composites were character-ised by scanning electron microscopy and energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and X-ray diffractometry techniques. After thermal exfoliation significant peak of graphite at 2? = 26.4? disappeared completely, confirming successful exfoliation of graphite. SEM images revealed homogeneous dispersion of exfoliated graphite in the matrix and EDAX confirmed successful reduction of graphite oxide.展开更多
基金This paper was the part of doctor thesis of China Uni-versity of Geoscience, (Beijing). The project was sup-' ported by Natio
文摘The intercalation compounds of CuCl2 were synthesized with expanded graphite, whose magni-tude of the electrical conductivity is about 103S.cm1. Their electrical conductivity is 3-6 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 nonstoichoi-metric. 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.
基金the National Natural Science Fund(50774071) ;the Natural Science Foundation of Hubei Province(2004ABA090).
文摘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.
文摘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.
文摘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+ ).
文摘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.
基金the National Basic Research Programof China (2004CB217808)National Natural Science Foundation of China (90306014 ,20471041)Youth Science Foundation of Shanxi Province (2006021020)
文摘Rare-earth oxide graphite intercalation compounds (CeO-GICs) were prepared using graphite and CeOas raw materials by vacuum heat-treatment. The stage-5 GICs was formed after heat treatment at 800 ℃, and it was examined and characterized by X-ray diffraction (XRD). The XRD analysis of intercalation compounds indicated that a number of non-carbon reactant (atom, molecule, ion or groups) could intercalate the layers of graphite with reticulated layer structure physically. Consequently the layered structure of graphite changed and new physical and chemical properties were obtained. X-ray photoelectron spectroscopy (XPS) suggested that the compound intercalated into graphite should contain CeⅣ compounds.
文摘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.
基金support from the National Natural Science Foundation of China(NSFC nos.52172257,22005334,21773301 and 52022106)the Natural Science Foundation of Beijing(grant no.Z200013).
文摘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.
基金financially supported by the National Natural Science Foundation of China(21975251)。
文摘Graphite is a universal host material for ion intercalation. Li+-graphite intercalation compounds (GICs) have been successfully utilized as the anode material in commercial lithium-ion batteries.Similarly, anion-graphite intercalation compounds (AGICs) have been coming into their own in dual-ion batteries [1]. It is imperative to deepen an understanding of anion storage mechanisms in graphite electrode.
基金financially supported by the National Key R&D Program of China (No. 2018YFB0104400)the National Natural Science Foundation of China (Nos. 52074036, 51725401, and 51874019)Beijing Municipal Science and Technology Commission (No. Z191100002719007)
文摘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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11225421,11474277,and 11434010)
文摘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.
文摘Composites based on ultradispersed polytetrafluoroethylene and intercalated graphite oxide compounds with dodecahydro-closo-dodecaborates and methods of their fabrication have been developed. The fabricated composites have been characterized using XRD analysis, and optical microscopy. These composites are distinguished with completeness of their combustion, since the combustion products comprise gaseous boron fluorine-containing compounds of boron, boron trifluoride (BF3), and boron oxyfluoride ((BOF)3). Besides, these composites are characterized with increased energy capacity as compared to purely oxygen-containing compounds, since the heat of formation of boron fluorine-containing compounds is higher than that of boron oxide. Introduction of ultradispersed polytetrafluoroethylene imparts composites with hydrophobicity, thus improving their functioning properties.
基金Supported by the National Natural Science Foundation of China(No.20673068)
文摘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.
文摘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.
基金the National Natural Science Foundation of China (No.51502086)Natural Science Foundation of Hunan Province (No.2018JJ3042)Hunan Province Science and Technology Plan Projects (No.2017TP1009).
文摘FeCI3-intercalated graphite intercalation compounds (GICs) with high reversible capacity and high volumetric energy density are attractive anode material alternatives of commercial graphite. However, the rapid capacity decay, which was induced by chloride dissolution and shuttling issues, hindered their practical application. To address this problem, here, we introduce flake-like Fe2O3 species with inherently polar surface on the edge of FeCl3 -intercalated GICs through microwave-assisted transformation of a fraction of FeCl3 component. Theoretical simulations and physical/electrochemical studies demonstrate that the introduced Fe2O3 component can afford sufficient polar active sites for chemically bonding the soluble FeCl3 and LiCl species based on the polar-polar interaction mechanism, further inhibiting the outward diffusion of the chlorides and immobilizing them within the GIC material. In a lithium ion cell, the FeCl3 -intercalated GIC with a suitable Fe2O3 content shows remarkably improved cycling stability with a high reversible capacity of 1,041 mAh·g^-1 at a current density of 200 mA·g^-1. Capacity retention of 91 % is achieved at a high current density of 1,000 mA·g^-1 over 300 cycles. This work opens up the new prospect for immobilizing chlorides by introducing inorganic species in GIC for long-cycle electrochemical batteries.
文摘The laws of forming metal- ammonia- graphite biintercalation compound (MAGBC ) undr natural or electrolytic conditions were studied by selecting microstructural parameter functions in accordance with the chemcal bond theory, and function Φ(g) was proposed to characterize the capability of metal-liquid ammonia solutions to be interalated and the relevant laws were thus summed up together with structural paramter diagrams. Results in general agreement with experimental facts, and some expected results without experiment reports as well, were obtained and satisfactorily explained from the view point of energy.
文摘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.
基金This work was supported by the Foundation of Civil Aviation University of China (No. 2001-3-18).
文摘Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1/2)a_0 x a_0 superstructure is formed, aregiven, and the results are in good agreement with the experiments and theoretical calculations. Therelationship between critical temperature and M-ion-vacancy interaction parameter is linear.
基金the National Natural Science Foundation of China(No.51804022)the Fundamental Research Funds for the Central Universities(No.FRF-TP-18-003C2)。
文摘Aluminum storage systems with graphite cathode have been greatly promoting the development of state-of-the-art rechargeable aluminum batteries over the last five years;this is due to the ultra-stable cycling,high capacity,and good safety of the systems.This study discussed the change of electrochemical behaviors caused by the structural difference between flake graphite and expandable graphite,the effects of temperature on the electrochemical performance of graphite in low-cost AlCl_(3)-NaCl inorganic molten salt,and the reaction mechanisms of aluminum complex ions in both graphite materials by scanning electron microscopy,X-ray diffraction,Raman spectroscopy,cyclic voltammetry,and galvanostatic charge-discharge measurements.It was found that flake graphite stacked with noticeably small and thin graphene nanosheets exhibited high capacity and fairly good rate capability.The battery could achieve a high capacity of^219 mA·h·g^(-1) over 1200 cycles at a high current density of 5 A·g^(-1),with Coulombic efficiency of 94.1%.Moreover,the reaction mechanisms are clarified:For the flake graphite with small and thin graphene nanosheets and high mesopore structures,the reaction mechanism consisted of not only the intercalation of AlCl4^-anions between graphene layers but also the adsorption of Al Cl4^-anions within mesopores;however,for the well-stacked and highly parallel layered large-size expandable graphite,the reaction mechanism mainly involved the intercalation of AlCl4^-anions.
文摘Exfoliated graphite was prepared by chemical route and then further subjected to thermal oxidation and sonication for size reduction and increased interlayer spacing in natural flake graphite. Exfoliated graphite/ABS composites were pre-pared with varying filler concentration by solution casting method. Exfoliated graphite and composites were character-ised by scanning electron microscopy and energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and X-ray diffractometry techniques. After thermal exfoliation significant peak of graphite at 2? = 26.4? disappeared completely, confirming successful exfoliation of graphite. SEM images revealed homogeneous dispersion of exfoliated graphite in the matrix and EDAX confirmed successful reduction of graphite oxide.