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In a typical Al–air battery, the air cathode functions as a deposition substrate for discharge products while allowing O2 entrance. Herein, we present an air electrode that simultaneously allows two discharge processes. The function of the metal–air battery is enabled by using porous carbon nanotube (CNT)-based tissue substrates. In contrast, the fluorinated graphite (CFx) coating on the CNT substrate provides an additional discharge process, enhancing discharge capacity. Two CFx loadings are investigated, and their performances are compared with that of a pristine CNT tissue. Electrochemical evaluations, including half- and full-cell measurements, are performed to examine the effect of the coating layer thickness on the ability of the cell to function at high discharge rates. High CFx loadings improved the cell performance and increased discharge capacities (an increase of ~ 3 mAh cm−2 for the 0.1 mA cm−2 and ~ 5 mAh cm−2 for the 0.25 mA cm−2 evaluations) until reaching high discharge loads. When applying 0.5 mA cm−2, the additional layer restricts O2 access into the cell, preventing the metal–air battery from functioning as intended. High-resolution scanning electron microscopy and energy-dispersive X-ray spectroscopy are used to characterize the discharge products deposited on this unique electrode. [ABSTRACT FROM AUTHOR]

Although the primary lithium/fluorinated graphite battery has a high energy density of 3725 Wh kg−1, its complete irreversibility based on a conversion reaction between Li and fluorinated graphite hampers wide applications in rechargeable systems. Here, a new rechargeable three‐electrode battery configuration involving lithium, fluorinated graphite, and sulfur electrodes is developed, in which the initial middle‐fluorinated graphite cathode can be electrochemically transformed into a hybrid lithium anode, showing a low overpotential (12 mV), long cycle life (2000 h) and good deep stripping/plating features. This rechargeable battery delivers a high gravimetric energy density of 507.7 Wh kg−1 on the basis of the total mass of the three‐electrode materials. Moreover, the excessive consumption of lithium in the system can be in situ replenished, further lengthening the lifespan. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen doped sub-fluorinated graphite with larger layer spacing material. • Simple and effective modified method without high temperature or pressure. • Fluorinated graphite can obtain a power density of 40.23 kW kg−1. • The dependence of cathode material structure, LiF and cathode swelling is provided. Lithium/carbon fluorides batteries own a high theoretical energy density of 2180 Wh kg−1 and exceptional shelf life, but poor electrode kinetics, low electronic conductivity of cathode, and cathode swelling during discharge. In this work, fluorinated graphite is modified by a controllable solvent treatment using N-methyl-2-pyrrolidone at medium temperature (50 ∼ 90 °C). The modified fluorinated graphite is doped with nitrogen atoms and owns increased interlayer spacing and electrochemical active semi-ionic C F bonds, providing a higher conductivity and facilitating the diffusion of Li+ or solvent Li+. The maximum power density of the modified fluorinated graphite is 40.23 kW kg−1 at 25C. To elucidate the cathode swelling of the fluorinated graphite, in-situ confocal optical microscope and in-situ X-ray diffraction are conducted for the first time. It is found that the formation and accumulation of crystalline LiF during discharge, as well as the interlayer spacing of fluorinated graphite, are related to the cathode swelling in liquid electrolyte. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorinated graphite (FG) CF 0.4 is irradiated with a synchrotron white beam. • XPS spectra showed little change in the composition of the irradiated layers. • Under photon action, HNO 3 , NO 2 , NO, and N 2 decompose inside the FG matrix. • Embedded NO x molecules stimulate FG defluorination and vacancy formation. • Nitrogen from NO x molecules saturates the boundaries of vacancies. Layered fluorinated graphite material can become an efficient nanoreactor for photochemical reactions. In this work, we compared the photochemical behavior of partially fluorinated graphite (FG) and FG containing nitrogen oxides in the interlayer space (NO x @FG) under the action of a high-intense polychromatic photon beam from the synchrotron radiation source BESSY II. Analysis of the chemical and electronic states of the samples was performed using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. Density functional theory calculations were used to interpret and analyze the experimental data. It was found that nitrogen oxides promote the photo-induced degradation of the FG matrix, namely, its partial defluorination, formation of vacancies and doping with nitrogen, while the empty FG had a high photoresistance to synchrotron radiation. The results obtained can be used in the development of new approaches to the modification of graphene layers and in the creation of photostable materials for optical elements. [ABSTRACT FROM AUTHOR]

• The CF 0.75 cathode has successfully modified by an ultrathin carbon layer (CF 0.75 @C). • The modified CF 0.75 @C has a high degree of disorganization. • The modified CF 0.75 @C provides additional paths for electronic transmission. • The Li/CF x primary batteries using of CF 0.75 @C cathode achieve better performance. To improve the electrochemical performance of lithium/fluorinated graphite (Li/CF x) primary batteries, the surface of fluorinated graphite cathode is modified with ultrathin carbon layer (CF 0.75 @C) by hydrothermal method. The electrochemical performance and voltage delay of the CF 0.75 @C are significantly improved compared to the pristine CF 0.75 , due to the carbon coating reducing charge transfer resistance and providing more electrons/ions transport paths. As a result, the assembled batteries can discharge at a high rate of 6C and exhibit a specific capacity of 327 mAh/g, corresponding to a high energy density of 625 Wh kg−1. In addition, the optimized batteries exhibit excellent high and low temperature performances (−20 °C ∼ 80 °C), which can be used regularly under harsh conditions. Significantly, this research provides a novel idea to achieve Li/CF x primary batteries with high discharge speed, low voltage delays and a wide temperature range. [ABSTRACT FROM AUTHOR]

The deintercalation process for the first stage fluorinated graphite inclusion compound CFBr·0.285CHCN was studied under isothermal conditions. It was shown by a combination of gravimetric and X ray diffraction methods that the decomposition of the first stage inclusion compound into the second stage compound (and gaseous CHCN) under isothermal conditions proceeds through the mixed-layer state that simultaneously consists of three main microphases: the first, the second and the fourth stages of filling with their identity periods 9.42, 15.50 and 27.8 Å, respectively, and of the second stage of filling in its labile extended state with the identity period of about 16.3 Å. It follows from structural properties that the C-C bonds of 'guest' molecules are mostly coplanar with the fluorocarbon layers of the 'host' matrix. [ABSTRACT FROM AUTHOR]

Few-layer graphene samples have been obtained by a thermal expansion of bromine-intercalated fluorinated graphite with a ∼C2F matrix composition at 600, 700, and 800 °C. X-ray photoelectron spectroscopy detected that the products contained almost the same quantities of foreign atoms independently on the exfoliation temperature. However, the Raman spectra showed a progressive increase in the relative intensity of the D mode with the temperature growth. This was attributed to more edge states developed in graphene planes at the higher temperature. Thin films from obtained samples were tested as sensors using 1000 ppm nitrogen dioxide (NO2) in argon. The film from few-layer graphene produced at 800 °C had the largest relative response, while its recovery was quite low at room temperature. The sensor performances were related with the structural characteristics of the exfoliated graphenes. Left: Relative response of gas sensors based on few-layer graphene products of an expansion of fluorinated graphite at 600, 700, and 800 °C toward 1000 ppm NO2. Right: Proposed structures of the products. [ABSTRACT FROM AUTHOR]

The poor electronic conductivity of fluorinated graphite (CF x) is one of the key problems limiting its electrochemical performance. Herein, polydopamine−derived nitrogen−doped carbon coating is adapted to improve the electrochemical performance of CF x by modifying its electronic conductivity. The effects of dopamine hydrochloride/CF x ratio and the carbonization temperature on the electrochemical performance of nitrogen−doped carbon coated CF x samples (CF x @NC−x−y) cathodes are investigated. CF x @NC−x−y cathodes present enhanced rate performance and discharge plateau, and increased energy and power densities, compared with the pristine CF x. Particularly, the CF x @NC−3−350 achieves optimized electrochemical performance, such as a discharge capacity of 550.5 mAh g−1 with a plateau of 2.18 V at 2000 mA g−1, corresponding to high power and energy densities of 4360 W kg−1 and 1171.2 Wh kg−1, whereas the pristine CF x is unable to work. The enhanced electrochemical performance is contributed to the improved electronic conductivity of the nitrogen−doped carbon−coated CF x. [ABSTRACT FROM AUTHOR]

Few-layer graphene materials have been produced by decomposition of fluorinated graphite intercalated with acetonitrile (CH3CN) or isopropylamine ((CH3)2CHNH2) in the conditions of thermal shock. Electronic structure of the samples before and after exfoliation was studied using near-edge X-ray absorption fine structure and X-ray photoelectron spectroscopy. Analysis of the spectroscopic data revealed the same set of nitrogen species in both exfoliation products that indicates decomposition of the intercalated molecules to the atomic state. Most of the nitrogen atoms were incorporated at the edges of graphene layers in pyridinic and protonated nitrogen forms. A difference in the electrochemical performance of the graphene materials was related with the exfoliation degree and the defect density in the graphene layers. Schematic representation of a process of thermal exfoliation of acetonitrile-intercalated fluorinated graphite. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new route for efficient and high-yield production of F-diamane-like nanosheets. • Using expanded graphite allows uniform dispersion of F atoms in the carbon lattice. • The exfoliation of expanded fluorinated graphite can be readily achieved. • Mild sonication produced F-diamane-like nanosheets up to micrometers in size. • Pre-exfoliation/fluorination and sonication is suitable for large-scale preparation. Ultrathin diamond (diamane)-like films or nanosheets have recently been experimentally obtained through chemically induced phase transition (e.g., fluorination) of bilayer graphene films or graphite flakes. To fully exploit the properties of diamane, further advances in the synthesis methods for its large-scale production are required. Herein, we report a new route for the efficient and high-yield production of fluorinated diamane (F-diamane)-like nanosheets. This is achieved by direct fluorination of expandable graphite or thermally expanded graphite with molecular fluorine to form stage-2 graphite fluoride (C 2 F) n made of stacked layers of F-diamane. Subsequently, mild sonication is implemented to exfoliate the layers into F-diamane-like nanosheets of hundreds of nanometers to a few micrometers in lateral size, with a thickness of mostly < 10 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydration process had been visualized on the fluorinated graphite (FG) layer for the first time. • By building a hydrate formation platform, FG made the hydrate grow upward. • Gas storage rate of FG + SDS system was 20.84 cm3·g−1·min−1, far higher than other materials. • Excellent stability of FG made the performance remain at about 90% after 10 cycles. Achieving rapid and high gas storage is the primary goal of solidified natural gas storage (SNG) using hydrate. In this study, the formation and decomposition process of hydrate were visualized on the fluorinated graphite (FG) layer for the first time by sapphire visible vessel. The results show that, the addition of FG alone can promote the formation of hydrate. After adding fluorinated graphite into SDS system, the gas storage capacity can be further increased to 165.2 cm3 STP/g H 2 O, and the average gas storage rate can be further increased to 20.84 cm3·g−1·min−1, which were 154.7% and 507.7% of SDS system, respectively. Meanwhile, the decomposition speed was faster than SDS system. After optimizing the experimental conditions, it was found that FG-1 with superhydrophobicity could stably exist in the gas–liquid interface and cover it when the dosage reached 1 wt% (13.95 mg·cm−2), and the combination with 300 ppm SDS could greatly promote the growth of hydrate. In addition, the excellent stability of FG made the performance of FG + SDS system remain at about 90% after 10 cycles. The unique growth phenomenon of hydrate in fluorinated graphite system was interesting. By building a hydrate formation platform, FG made water pumped from below to the gas phase and hydrate grow upward continuously. In comparison with other reported carbon nanoparticles, FG system maintained similar gas storage and had excellent gas storage speed, which was 1.35 ∼ 40.67 times faster under similar conditions. Therefore, the reusable FG + SDS system with high gas storage capacity and fast growth rate without induction time and mechanical agitation was a promising alternative to hydrate-based SNG technology. [ABSTRACT FROM AUTHOR]

Inclusion compounds (intercalates) of fluorinated graphite matrix with butanone (CFBr· yCHCOCH, x = 0.49, 0.69, 0.87, 0.92, z ≈ 0.01) were prepared by guest substitution from acetonitrile to butanone. The kinetics of the thermal decomposition (the 1st stage of filling → the 2nd stage of filling) was studied under isothermal conditions at 294-313 K. The relationship of the host matrices structure with inclusion compounds' thermal properties and kinetic parameters is discussed. [ABSTRACT FROM AUTHOR]

Fluorinated graphitic layers with good mechanical and chemical stability, polar C–F bonds, and tunable bandgap are attractive for a variety of applications. In this work, we investigated the photolysis of fluorinated graphites with interlayer embedded acetonitrile, which is the simplest representative of the acetonitrile-containing photosensitizing family. The samples were continuously illuminated in situ with high-brightness non-monochromatized synchrotron radiation. Changes in the compositions of the samples were monitored using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS N K-edge spectra showed that acetonitrile dissociates to form HCN and N2 molecules after exposure to the white beam for 2 s, and the latter molecules completely disappear after exposure for 200 s. The original composition of fluorinated matrices CF0.3 and CF0.5 is changed to CF0.10 and GF0.17, respectively. The highly fluorinated layers lose fluorine atoms together with carbon neighbors, creating atomic vacancies. The edges of vacancies are terminated with the nitrogen atoms and form pyridinic and pyrrolic units. Our in situ studies show that the photolysis products of acetonitrile depend on the photon irradiation duration and composition of the initial CFx matrix. The obtained results evaluate the radiation damage of the acetonitrile-intercalated fluorinated graphites and the opportunities to synthesize nitrogen-doped graphene materials. [ABSTRACT FROM AUTHOR]

An X-ray diffraction technique for the study of imperfect crystals of natural graphite and its fluorinated products is proposed. The diffraction patterns measured are free from the preferred orientation effect and provide the simulation based on a 1D disordered crystal. [ABSTRACT FROM AUTHOR]

Thermal dissociation processes for acetonitrile inclusion compounds based on the polymer fluorographite host matrix CFBr· yCHCN, where x = 0.49-0.92, y = 0.174-0.285, are investigated. Thermodynamic parameters (Δ H°, Δ S°, Δ G°) for deintercalation of the compounds of the first filling step into the compounds of the second step and gaseous guest within temperature range 294-352 K were determined. The effect of the host matrix fluorination degree on the thermodynamic characteristics of the studied processes is demonstrated. [ABSTRACT FROM AUTHOR]

Inclusion compounds (intercalates) of fluorinated graphite matrix with acetone (CFBr· y(CH)CO, x = 0.49, 0.69, 0.87, 0.92, z ≈ 0.01) were prepared by guest substitution from acetonitrile to acetone. The kinetics of the thermal decomposition (the first stage of filling → the second stage of filling) was studied under isothermal conditions at 292-313 K. The relationship of the host matrices structure with inclusion compounds thermal properties and kinetic parameters is discussed. [ABSTRACT FROM AUTHOR]

Abstract: The discharge performance of Li/CF x (x =1) battery is improved by using multi-walled carbon nanotubes (MWCNTs) as an alternative conductive additive. Compared with the battery using acetylene black as conductive additive at the same amount, the Li/CF x battery using MWCNTs as conductive additive has higher specific capacity and energy density as well as smoother voltage plateau, especially at higher discharge rate. The specific capacity at discharge rate of 1C is improved by nearly 26% when MWCNTs are employed as conductive additive. Meanwhile, it is also found that the discharge performance is able to be tuned by the amount of MWCNTs and the battery containing more MWCNTs is favorable to be discharged at higher rates. The specific capacity of Li/CF x battery with 11.09wt.% MWCNTs is approximately 712mAhg−1 at the discharge rate of 1C. It is proposed that the formed three-dimensional networks of MWCNTs in cathode, which enlarges the contact area of interphase and facilitates electrons delivery, accelerates the rates of lithium ion diffusion into the fluorinated layers and electrons transport in cathode at the same time, which improves the discharge performance of Li/CF x battery subsequently, especially at higher rates. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical performances of fluorinated graphite have been improved by coating a uniform carbon layer on commercial CF x (x =1) powder used as cathode material in lithium battery. In comparison with the cell using un-coated CF x as cathode, the cell using carbon coated CF x cathode has a higher energy density and higher power density, particularly at higher discharge current rates (1C above). This is because the conductive carbon coating provides the exterior connectivity between particles for facile electron conduction, resulting in high rate performance. [Copyright &y& Elsevier]

Inclusion compounds (intercalates) of fluorinated graphite matrix with 1,2-dichloroethane (C2FxBrz·yC2H4Cl2, x=0.49, 0.69, 0.87, 0.92, z≈0.01) were synthesized by guest substitution from acetonitrile to dichloroethane. The kinetics of the thermal decomposition (the 1st stage of filling→the 2nd stage of filling) was studied under isothermal conditions at 289–313 K. The relationship between the structure of host matrices with thermal properties and kinetic parameters of inclusion compounds is discussed. [ABSTRACT FROM AUTHOR]

Inclusion compounds (intercalates) of fluorinated graphite matrix with chloroform (C2FxBrz· yCHCl3, x=0.49, 0.69, 0.87, 0.92, z=0.01) were synthesized by guest substitution from acetonitrile to chloroform. The kinetics of the thermal decomposition (the 1st stage of filling → the 2nd stage of filling) was studied under isothermal conditions at 286–311 K. The relationship between the structure of matrices intercalates with thermal properties and kinetic parameters of inclusion compounds is discussed. [ABSTRACT FROM AUTHOR]

Inclusion compounds: intercalates of fluorinated graphite matrix with acetonitrile (C2FxBrz· yCH3CN, x=0.92, 0.87, 0.69 and 0.49, z≈0.01) were synthesized. The kinetics of the thermal decomposition (the 1st stage of filling→the 2nd stage of filling) was studied under isothermal conditions. The relationship between intercalates properties and composition and structure of the matrix is discussed. [ABSTRACT FROM AUTHOR]

Structures and electronic properties are presented for three types of sp 2 /sp 3 mixed nano-carbon systems. Nano-diamond/nano-graphite conversion takes place around 1600°C, which changes the magnetism from sp 3 -defect-dominated one to π-edge state originating one. Fluorination in the initial stage, which prefers edge carbon sites of nano-graphites, destroys the π-edge states, and the succeeding fluorination generates sp 3 -defects with surrounding σ-non-bonding state at the interior carbon sites. Diamond-like-carbon has non-equilibrium sp 2 /sp 3 mixed structure with atomic scale disorders, which is easily converted to 3D random network of nano-graphite domains by heat-treatment. [ABSTRACT FROM AUTHOR]

• Composition of graphite fluoride C 2 F x is controlled by changing the ratio BrF 3 /Br 2 in reaction. • The size of sp2 carbon regions increases with the decrease of x in C 2 F x. • Replacement of guest molecules in C 2 F x has little effect on the matrix properties. • Br 2 guests in C 2 F x are difficultly substitutable for CH 3 CN when x < 0.5. The interaction of graphite with a gaseous mixture of BrF 3 and Br 2 at room temperature produced fluorinated graphite intercalation compounds with bromine. By changing the concentration of BrF 3 in Br 2 from 6.2 to 2.9 % we were able to obtain matrices of fluorinated graphene layers (C 2 F x) n with x = 0.76, 0.66, 0.35, 0.25. It was shown that bromine was completely replaced by acetonitrile in the (C 2 F x) n with x > 0.6, while two types of guests (CH 3 CN and Br 2) were present between the layers with the lower fluorine loading. The Van der Waals forces hold CH 3 CN molecules in the (C 2 F x) n host. The interaction of Br 2 molecules with sp2 -carbon regions remained in the C 2 F x layers has donor-acceptor type. The models of guest molecules packing in host matrices (C 2 F x) n are considered using the data on the stoichiometry and X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]