Interlayer Spacing Of Graphite Research Articles

Self-Standing vanadium oxide pillared carbon microfiber film as an excellent anode for lithium & sodium ion batteries

Insertion of substances (such as atoms/molecules/ions) into the interlayer spaces of graphite to increase its layer separation is found to be extremely useful for sodium-ion batteries (SIBs). Therefore, expanded graphitic systems are the obvious choice as anode material for both lithium/sodium-ion batteries (LIBs/SIBs). Hard carbon-based materials altogether give a decent electrochemical performance, as well as allow structural integrity for long-term use. Herein, we report a facile route to prepare free-standing vanadium oxide doped carbon microfibers (V@CMFs) films. The V@CMFs show ∼ 200 % expansion in the graphitic interlayer distances while accommodating minute deformations in the final compound which is further theoretically verified as the stage-1 type dilute graphite intercalation compound (GICs) with pillar-like structures. Best battery performance was obtained for the 1 % doped (V1@CMFs) sample, with an initial discharge capacity of 1501.8 and 703.4 mAhg−1, reversible capacities of 1253.8 and 288.7 mAhg−1 at 20 mAg−1, and rate capabilities i.e., 362.4 and 108.1 mAhg−1 at 1600 mAg−1, for LIBs and SIBs, respectively. The results revealed that the rate capability and the reversible specific capacity of the 1 % vanadium oxide doped carbon microfibers (V1@CMFs) are significantly superior compared to the pristine and previous reports. Here, the incorporation of just 1 % vanadium oxide acts as a pillar, enhancing the stability and conductivity of the carbon. Thus, the present work highlights the utility of molecularly doped GICs as potential anode materials for LIBs/SIBs.

N/P/O co-doped porous carbon derived from agroindustry waste of peanut shell for sodium-ion storage

Porous bio‑carbon from agroindustry waste behaves one of the most promising anode materials for sodium-ion batteries (SIBs) because of its high sodium storage capacity, low cost, sustainability, and low charge/discharge voltage platform. Herein, we have developed a new N/P/O co-doped porous hard carbon derived from peanut shell (PSCNP) synthesized via KOH activation, hydrothermal doping combined with carbonization method, using chitosan as nitrogen source, phytic acid as phosphorus source, and peanut shell as carbon and oxygen source. Through seriously regulating the calcination temperature, the optimal PSCNP-800 carbonization at 800 °C can well combine the advantages of the natural rich porous microstructure of peanut shells, large graphite interlayer spacing (0.379 nm), and short diffusion distance for sodium-ion. As an advanced anode for SIBs, the PSCNP-800 delivered a reversible capacity of 248.8 mAh g−1 after 100 cycles at 25 mA g−1. This work could provide a possible idea for the preparation of N/P/O co-doped porous hard carbon from low-cost agroindustry waste as anodes for SIBs.

Impact of Na at the low temperature Fe catalysis on high quality cellulose-based graphitic carbon

Biomass-based graphitic carbon is a promising material, but the effect mechanism of inherent alkali metals on the catalytic pyrolysis of biomass is still unclear. In this study, cellulose was selected as the model substance, and the influence mechanism of Na on the graphitization of cellulose catalytic pyrolysis was investigated through a combination of experiments and theoretical calculations. The results indicate that Na can interact with the carbon skeleton through van der Waals forces, thereby altering the spatial structure of graphite crystals and increasing the interlayer spacing of graphite by 27.7%. In addition, Na can coexist with Fe(III) in the form of oxides, while also increasing the reaction energy barrier of reverse hydroxylation and dehydration cyclization, decreasing the generation of reducing gases mainly composed of CO. This impedes the reduction of iron-based catalysts, thereby affecting the formation of the graphite microcrystalline structure. The research indicates that maintaining the ratio of Na content to iron-based catalysts within a 1:1 range is optimal for producing graphite carbon from cellulose.

A superior sodium-ion anode material from PAN/lignin-derived carbon nanofibers with inter-connected structure prepared through phosphoric acid induced cross-linking

A feasible route to fabricate phosphorus-doped carbon nanofibers (P-CNFs) with an inter-connected structure has been demonstrated through electrospinning, stabilization, and subsequent phosphoric acid impregnation and carbonization processes using polyacrylonitrile and lignin as carbon sources. The results illustrate that the phosphoric acid induced cross-linking could be beneficial to acquire the closed-pore structure and the heteroatom-doped surface chemistry of nanofibers. As a result, the P-CNFs exhibit higher interlayer spacing of graphite and lower BET specific surface area compared to the pristine CNFs. The P-CNFs as an anode material for sodium-ion batteries (SIBs) present a high reversible capacity 278 mA h g−1 at 0.2 A g−1 and a superior initial Coulomb efficiency (ICE) of 78.86 %. Moreover, the reversible capacity of P-CNFs can be stably maintained near the initial capacity after 5000 cycles at 1 A g−1, showing exceptional structural stability and cycling durability. Meanwhile, the sodium storage mechanism of P-CNFs was investigated using in-situ Raman and ex-situ XRD analysis to understand the exceptional structural stability and Na+ adsorption capacity of P-CNFs. This work provides valuable insights for the design of carbon nanofibers with an inter-connected structure as anode materials for SIBs, exhibiting outstanding electrochemical properties.

Low friction coefficient bioinspired copper/graphene nanolaminates with high content graphene

Graphene is widely used in metal matrix composites (MMC) to improve the tribological properties of metal due to its special lamellar structure and excellent tribological properties. However, because the aggregation of graphene, it is difficult to increase the content of graphene in metal materials, which seriously hinders the further optimization of friction coefficient. In this paper, we report a bioinspired strategy to fabricate nacre-like copper/graphene nanolaminates through chemical intercalation of copper precursor into the interlayer space of expandable graphite and subsequent reduction. The regular parallel arrangement of graphene can greatly improve the agglomeration phenomenon and the aspect ratio of graphene, which harden the copper matrix by effectively restricting the motion of dislocation and also form continuous lubricating film on the surface. A low dry sliding friction coefficient 0.13 is thus obtained among copper-based composites without severely deteriorating the electrical properties, providing new prospect in sliding electrical contact applications.

Invasive alien plant biomass-derived hard carbon anode for sodium-ion batteries

In the context of rampant growth of invasive plants, finding suitable ways for resource utilization has become the optimal choice for invasive plant management. In the field of energy storage, sodium-ion batteries have been limited by the lack of appropriate anode materials, and hard carbon stands out as the most promising candidate. Therefore, this study focuses on the preparation of biomass-derived carbons from three invasive plant species, namely Spartina alterniflora Loisel., Solidago canadensis L., and Erigeron canadensis L., through high-temperature carbonization. The resulting biomass carbons are then subjected to cleaning and activation processes to prepare sodium-ion anode materials. The internal structure of the materials was characterized using SEM, TEM, XRD, XPS, Raman spectroscopy, and BET. The materials exhibited a significant amount of pore structures, with interlayer spacing around 0.37 nm, which is larger than the original graphite interlayer spacing. The plant anode materials were assembled into full batteries for cyclic charge/discharge tests. The results show that all three anode materials have good multiplicative performance and excellent cyclable charge/discharge. After 100 cycles at a current of 50 mA in the voltage range of 0–3.0 V, the reversible capacities of the three materials reached 245.3, 207.19, and 227.12 mAh/g, respectively. Among them, the material derived from Spartina alterniflora maintained a capacity of 141.63 mAh/g even after 1000 cycles at a current of 200 mA, demonstrating the best capacity performance.

CALCULATION OF THE ELECTRODE REACTION RATE ON A GRAPHITE CATHODE OF ALUMINUM-ION BATTERY WITH 1-ETHYL-3-METHYLIMIDAZOLIUM CHLORIDE

A method for determining the rate of sorption of chloraluminate complexes on graphite material as the main cathode reaction in aluminum-ion batteries with an ionic liquid as an electrolyte is proposed in terms of classic chemical kinetics approach. The method is applied to the description of the rate of a one-electron cathode reaction that is in the case the sorption/desorption of complexes on the electrode surface with no migration in the interlayer space of graphite taken into account. The experimental part is based on the selection and providing of measurement conditions and the ratio of the components of the cell to ensure that the rate of the cathode process sets the rate of current generation of the cell. The rate of supply/removal of electrons, as participants in the reaction, thus can be directly related to the reaction rate on graphite. The point of reaching the limiting current on the polarization curve in that case corresponds the limiting rate of the chemical sorption reaction. The approach takes into account the effect of other limiting processes, such as the rate of removal/supply of electrons, the rate of removal/supply of ions to/from the electrolyte volume, and the rate of anodic dissolution/deposition of aluminum. The calculated value of the reaction rate for graphite material grade EC-02 and low-temperature ionic liquid 1-ethyl-3-methylimidazole chloride in a mixture with aluminum chloride (1 : 1.3) was calculated to be 46 µmol/cm2 · s.

Tribological properties of low-temperature time-dependent pretreated graphite for mechanical seal pairs in high-speed turbopump

AbstractThe friction coefficient and wear rate of pretreated graphite with liquid nitrogen were obtained by using a ball-on-disk tester, and the wear of GCr15–graphite seal pairs with the low-temperature time-dependent pretreatment was discussed by comparing the wear morphology. The results show that liquid nitrogen pretreatment can affect the hardness and interlayer spacing of graphite. The range of the friction coefficients of pretreated graphite changes from 0.17 to 0.22. With the increase of liquid nitrogen pretreatment time, the wear mechanism of graphite would change from dominated three-body wear to adhesion wear. The experimental results of the mechanical seal with liquid nitrogen pretreatment show that the wear rate of stator is less than 0.00165 mm3·N−1·m−1, and the graphite shows a good low-temperature compatibility.

In Situ Pore Formation in Graphite Through Solvent Co‐Intercalation: A New Model for The Formation of Ternary Graphite Intercalation Compounds Bridging Batteries and Supercapacitors

AbstractFor Li‐ion and Na‐ion batteries, the intercalation behavior of graphite anodes is quite different. While Li‐ions intercalate, Na‐ions only co‐intercalate with solvent molecules from the electrolyte solution leading to ternary graphite intercalation compound (t‐GIC) formation along with an expansion of the graphite interlayer spacing to 1.2 nm. This large interlayer spacing represents a micropore with parallel slit geometry. Little is known about t‐GIC formation, but it is commonly believed that throughout the reaction the ion is accompanied by either a full or partial solvation shell. Here, it is elucidated for the first time, using two independent methods – mass measurements and electrochemical impedance spectroscopy – supplemented by operando microscopy, entropymetry and simulations, that the storage mechanism is far more complex. A new model for the electrochemical solvent co‐intercalation process is proposed: As soon as solvated ions enter, the graphite structure is flooded with free solvents, which are subsequently replaced by solvated ions. Close to full sodiation, few free solvents remain and structural rearrangement take place to reach the full storage capacity. Thus, t‐GICs represent a unique case of switchable microporous systems and hence appear as a bridge between ion storage in the bulk phase and in micropores, i.e., between batteries and supercapacitors.

Thermal volatilisation analysis of graphite intercalation compound fire retardants

Thermally expandable graphites are becoming increasingly popular as intumescent fire retardants for polymeric systems due to their excellent thermal and barrier properties. Therefore, it is important to understand their thermal degradation pathways and monitor products for any that may be toxic or affect the stability of the polymer. Here, two commercially available thermally expandable graphites with different intercalated acids have been analyzed using thermal volatilisation analysis—sub-ambient distillation (TVA-SAD), mass spectrometry (MS) and Fourier transform infrared spectroscopy (FTIR). Results confirm the presence of three principal thermal events relating to the expansion of graphite nitrate and graphite bisulfate. Isothermal analyses provide a deeper understanding of the processes and decomposition products released from each stage. For both graphites, desorption of migrating gases and volatilisation of water occur in the first instance. Graphite bisulfate releases CO2, CO, and water upon expansion and releases a significant volume of SO2 subsequently. Graphite nitrate expansion proceeds with the release of NO2, NO, CO and water. Additionally, the release of non-condensable species and carbonyl-derived fragments suggests that the exfoliation process occurs by multiple different degradation processes. For expansion to occur, sufficient pressure must be produced in the graphite interlayer spacing; this is achieved by volatilisation of intercalated species and by the decomposition of functional groups on the outer edges and basal planes created from the oxidation of graphite.

Enhanced electrical conductivity of pitch-derived carbon via graphene template effects for high electrically conductive composites

Large-scale preparation of cheap and high-performance carbonaceous materials is in urgent need due to the huge demand of carbonaceous materials-organic binder composites for Joule heating. Here, carbon-based electrothermal composites with high electrical conductivity were fabricated by adjusting the morphology and structure of pitch-based carbonaceous materials (PC) through the use of graphene as structure-directing agent to tune the orientation and carbonization of coal pitch. It is demonstrated that the addition of graphene can effectively promote the formation of graphitized carbon, increase the content of sp2C, reduce defective carbon and increase the graphite interlayer spacing. 1% graphene-added PC-PVDF composite exhibits 290% increase in the carrier concentration, 190% enhancement in mobility, and 67% reduction in the volume resistivity compared to PC-PVDF composite. Molecular simulations elucidate that the graphene edges favor pitch carbonization and improve the orientation factor and energy gap of carbon materials. This study provides clues for design of low-cost pitch-derived carbon materials-binder composites.

Diazotization Grafting Phenol for Improving the Electrochemical Performance of Graphite Anode

Capacity fading resulting from graphite exfoliation is a thorny problem for real application of the graphite anodes in lithium-ion batteries. In this paper, we report on diazotization grafting phenol for graphite flakes to settle this issue, using 4-aminophenol and tert-butyl nitrite as the diazonium reagents. Diazotization grafting phenol enables expansion of graphite interlayer spacing and formation of surface protective layer, yielding modified graphite anodes with improved electrode kinetics, and significantly improved cycling stability. Also, the phenol modifier contributes additional specific capacity to the anode through reversible redox reaction of phenol hydroxyls with Li+ ions. The modified graphite anode with mole percent of 4-aminophenol to graphite being 5% retains a discharge specific capacity of 361 mA h g‒1 after 300 cycles at 1C, presenting capacity retention of 90.5% relative to the initial cycle, much higher than that of 156 mA h g‒1 and 54.2% for pristine graphite.

Phosphorus/sulfur co-doped hard carbon with a well-designed porous bowl-like structure and enhanced initial coulombic efficiency for high-performance sodium storage

Hard carbon with high specific capacity and cost-effective characteristics has emerged as a critical material in the study of sodium-ion batteries (SIBs) anodes. However, their unsatisfactory initial coulombic efficiency (ICE) and ineluctable structural deformation during long-cycling work seriously hinder their application in practice. Here, phosphorus/sulfur co-doped hard carbon with a porous bowl-like structure (denoted as P/S-HCB) is developed to achieve high performance. The experimental data show that the doping of S increased the interlayer spacing of graphite in the surface/subsurface region, the doping of P promoted the formation of C-S-P and P-O bonds, which can contribute to abundant structural defects and redox reaction sites that not only improves structural stability but also contributes to the capacitive process under high rate. The as-fabricated P/S-HCB electrode demonstrates outstanding Na-ion storage performance regarding high ICE of 88.71%, the high-reversibility capacity of about 450 mA h g−1 after 140 cycles at 0.2 A g−1, extraordinary rate capability of 216.3 mA h g−1 at 10 A g−1, and long-term cycling stability of 276 mA h g−1 after 3000 cycles at 10 A g−1. These results show a novel approach to developing advanced hard carbon materials for sodium storage.

Role of pH value on electrophoretic deposition of nano-silica onto carbon fibers for a tailored bond behavior with cementitious matrices

Electrophoretic deposition (EPD) of nano-silica (NS) onto carbon fiber (CF) surfaces may considerably improve the bond properties toward cementitious matrices. In the article at hand, varied pH conditions (neutral, acidic, and alkaline environments) are studied during EPD for a tailorable interfacial bond. Zeta potential measurements and cyclic voltammetry (CV) confirmed the importance of pH with regard to the EPD process. Scanning electron microscopy (SEM) and X- ray photoelectron spectroscopy (XPS) revealed that an acidic environment enables the most pronounced and homogeneous NS coating on the CF surfaces. X-ray diffraction (XRD) analysis delivered deeper insights into the microstructures of modified CFs, indicating a decreased graphite interlayer spacing d002 and an increased crystallite size Lc after treatment. This results in a changed temperature-stability as well as mechanical properties, as revealed by thermogravimetric analysis (TGA), single-fiber tensile tests, and Weibull analysis.To assess the interaction of the modified CFs with cementitious matrices, single-fiber pullout tests were performed, showing the highest bond strength and total pullout work of CFs treated in an acidic environment. This is mainly explained by a reaction of the high number of NS particles with calcium hydroxide to form calcium silicate hydrate (C-S-H) gel and, thus, intensifying the interfacial transition zone, subsequently increasing the bond properties of CF to a matrix. As well, abundant oxygen-related functional groups were introduced on the CF surfaces from anodic oxidation, leading to an enhanced bond by promoting precipitation of cement hydration products onto the CF surfaces.

Effect of Boron Doping on the Interlayer Spacing of Graphite.

Boron-doped graphite was prepared by the heat treatment of coke using B4C powder as a graphitization catalyst to investigate the effects of the substitutional boron atoms on the interlayer spacing of graphite. Boron atoms can be successfully incorporated into the lattice of graphite by heat treatment, resulting in a reduction in the interlayer spacing of graphite to a value close to that of ideal graphite (0.3354 nm). With an increase in the catalyst mass ratio, the content of substituted boron in the samples increased significantly, causing a decrease in the interlayer spacing of the boron-doped graphite. Density functional theory calculations suggested that the effects of the substitutional boron atoms on the interlayer spacing of the graphite may be attributed to the transfer of Π electrons between layers, the increase in the electrostatic surface potential of the carbon layer due to the electron-deficient nature of boron atoms, and Poisson contraction along the c-axis.

Controllable construction of hierarchically porous carbon composite of nanosheet network for advanced dual-carbon potassium-ion capacitors

Benefitting from the abundance and inexpensive nature of potassium resources, potassium-ion energy storage technology is considered a potential alternative to current lithium-ion systems. Potassium-ion capacitors (PICs) as a burgeoning K-ion electrochemical energy storage device, are capable of delivering high energy at high power without sacrificing lifespan. However, owing to the sluggish kinetics and significant volume change induced by the large K+-diameter, matched electrode materials with good ion accessibility and fast K+ intercalation/deintercalation capability are urgently desired. In this work, pine needles and graphene oxide (GO) are utilized as precursors to fabricate oxygen-doped activated carbon/graphene (OAC/G) porous nanosheet composites. The introduction of GO not only induces the generation of interconnected nanosheet network, but also increases the oxygen-doping content of the composite, thus expanding the graphite interlayer spacing. Experimental analysis combined with first-principle calculations reveal the transport/storage mechanism of K+ in the OAC/G composite anode, demonstrating that the high surface area, sufficient reactive sites, enlarged interlayer distance and open channels in the porous nanosheet network contribute to rapid and effective K+ diffusion and storage. When incorporated with pine needle-activated carbon as cathode, the assembled dual-carbon PICs can function at a high voltage of 5 V, exhibiting a high energy density of 156.7 Wh kg−1 at a power density of 500 W kg−1 along with a satisfied cycle life, which highlights their potential application in economic and advanced PICs.

Ultrasonic-Assisted Diels-Alder Reaction Exfoliation of Graphite into Graphene with High Resveratrol Adsorption Capacity.

Scalable preparation of graphene with high adsorption capacity is an important prerequisite for fully realizing its commercial application. Herein, we propose an environmentally friendly route for exfoliation of graphene, which is established based on the Diels–Alder reaction. In our route, N-(4-hydroxyl phenyl) maleimide enters between the flakes as an intercalating agent and participates in the Diels–Alder reaction as a dienophile to increase the interlayer spacing of graphite. Then, graphite is exfoliated into graphene with the aid of ultrasound. The exfoliated product is hydroxyl phenyl functionalized graphene with a thickness of 0.5–1.5 nm and an average lateral size of about 500–800 nm. The exfoliation process does not involve any acid or catalyst and would be a safe and environmentally friendly approach. In addition, the exfoliated graphite shows high resveratrol adsorption capacity, which is ten times that of macroporous resins reported in the literature. Thus, the method proposed herein yields exfoliated graphite with high resveratrol adsorption capacity and is of great significance for the mass production of graphene for practical applications.

Interlayer Design of Pillared Graphite by Na-Halide Cluster Intercalation for Anode Materials of Sodium-Ion Batteries.

Graphite is currently utilized as anode materials for Li-ion batteries, but it is well-known that graphite does not show good electrochemical performances as the anode material for sodium-ion batteries (SIBs). It was also reported that the low electrochemical performances of graphite originated from the larger ionic radius of the sodium ion due to the required higher strain energy for sodium-ion intercalation into graphite leading to an unstable sodium-ion intercalated graphite intercalation compound (GIC). In this work, using first-principles calculations, we introduce pillaring effects of NanX (n = 3 and 4; X = F, Cl, or Br) halide clusters in GICs, which become electrochemically active for Na redox reactions. Specifically, to enable sodium-ion intercalation into graphite, the interlayer spacing of graphite is required to increase over 3.9 Å, and NanX halide cluster GICs maintain an expanded interlayer spacing of >3.9 Å. This enlarged interlayer spacing of NanX halide cluster GICs facilitates stable intercalation of sodium ions. Na3F, Na4Cl, and Na4Br halide clusters are identified as suitable pillar candidates for anode materials because they not only expand the interlayer spacing but also provide reasonable binding energy for intercalated sodium ions for reversible deintercalation. Based on the model analysis, theoretical capacities of Na3F, Na4Cl, and Na4Br halide cluster GICs are estimated respectively to be 186, 155, and 155 mA h g–1. These predictions would provide a rational strategy guiding the search for promising anode materials for SIBs.

Improvement of alkali metal ion batteries via interlayer engineering of anodes: from graphite to graphene.

Interlayer engineering of graphite anodes in alkali metal ion (M = Li, Na, and K) batteries is carried out based on the first-principles calculations. By increasing the interlayer spacing of graphite, the specific capacity of Li or Na does not increase while that of K increases continuously (from 279 mA h g-1 at the equilibrium interlayer spacing to 1396 mA h g-1 at the interlayer spacing of 20.0 Å). As the interlayer spacing increases, the electrostatic potential of graphite becomes smoother, and the ability to buffer the electrostatic potential fluctuation becomes poorer in M ions. These two effects jointly lead to minima of the diffusion barrier of M ions on graphite (0.01-0.05 eV), instead of strictly monotonous declines with the increasing interlayer spacing. To perform the interlayer engineering of anode candidates more efficiently, a set of high-throughput programs has been developed and can be easily applied to other systems. Our research has guiding significance for achieving the optimal effect in interlayer engineering experimentally.

Nitrogen and sulfur co-doped mesoporous carbon derived from ionic liquid as high-performance anode material for sodium ion batteries

Abstract Sodium ion batteries (SIBs) are widely considered as one of the most potential alternatives to traditional lithium ion batteries (LIBs) thanks to abundance of sodium on earth. Although these batteries have very similar electrochemistry, the graphite-based LIB anode cannot be directly applied for SIBs due to the much larger ionic radius of Na+. Herein, we report nitrogen and sulfur co-doped mesoporous carbon (NSPC) as high-performance anode material for SIBs, which is synthesized via a salt template strategy with an ionic liquid as the carbon and doping source. After carbonization, the mesoporous NSPC contains a high nitrogen content of 10.45 wt% and 1.52 wt% of sulfur with an enlarged graphite interlayer spacing to facilitate Na+ intercalation. When used as an anode in SIBs, the NSPC shows a good electrochemical performance with a specific capacity of 243 mAh g−1 after 240 charge-discharge cycles at 0.14 A g−1. The reversible capacity remains at 102 mAh g−1 after 5,000 cycles at 1.40 A g−1. The high-performance of the NSPC for Na+ storage is attributed to the double doped heteroatoms and mesoporous structure, which synergistically enhance the storage capacity and rate capability, and maintain the electrode stability during cycling.