Graphite Interlayer Research Articles

In Situ Formation of Nanoparticles on Carbon Nanofiber Surface Using Ceramic Intercalating Agents

Nickel silicide nanoparticles were prepared in situ on carbon nanofibers through pyrolysis of electrospun fibers containing poly(acrylonitrile) (PAN, carbon fiber precursor), silazane (SiCN ceramic precursor), and nickel chloride (nickel source). SiCN ceramics produced in carbon nanofibers during the pyrolysis expanded the graphitic interlayer spacing and facilitated the diffusion of metal atoms to the fiber surfaces, leading to the formation of nickel silicide nanoparticles at a reduced temperature. In addition, nickel silicide nanoparticles catalyzed an in situ formation of carbon nanotubes, with carbon sourced from the decomposition of silazane. The method introduces a simple route to produce carbon supported metal nanoparticles for catalysis and energy storage applications.

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.

Strength of diamond - silicon carbide interfaces in silicon carbide bonded diamond materials containing graphitic interlayers

The properties of composite materials strongly depend on the bonding between the reinforcement particles and the matrix phase. High strengths of the diamond/SiC interface have recently been reported for silicon carbide bonded diamond materials. Due to the metastable character of diamond under manufacturing conditions, graphite interlayers can form within the diamond/SiC interface. In order to investigate their influence on the strength of the interface, a material with intentionally generated graphitic interlayers was prepared and micro-cantilevers were cut by focused ion beam milling (FIB) at the SiC/graphite-interlayer/diamond interface. By in-situ bending experiments inside a scanning electron microscope (SEM), a mean value of 7.0 ± 1.2 GPa was obtained as interface strength, which is only slightly lower than the value of graphite-free SiC/diamond interfaces. These values are indicative of direct covalent bonding of the graphitic layers to the diamond reinforcement particles. The results show that thin graphitic interlayers have only little effect on the properties of SiC bonded diamond materials.

Oxidating Fresh Porous Graphene Networks toward Ultra‐Large Graphene Oxide with Electrical Conductivity

AbstractUltra‐large graphene oxide (ULGO) is one of the most important graphene derivates because of its processability in constructing various macrostructures with unique properties. However, existing oxidation–exfoliation technologies are limited in the available size range, structure controllability, and preparation efficiency of ULGO by the slow oxidant diffusion among graphite interlayers. Herein, a highly efficient strategy to fabricate ULGO featuring the oxidation of porous graphene networks freshly derived from electrochemical delamination, which highlights the significance of not only creation but also keeping of the fast diffusion channels for oxidant, is proposed. Consuming only 40 min and ultralow oxidant dosage (1 wt equiv.), this economical oxidation realizes high‐yield preparation (≈99.5%) of ULGO with record‐large average size (188.3 µm) and unusual low‐defect structure. Unlike previous reports, free‐standing films assembled from the as‐prepared ULGO exhibit an unexpected electrical conductivity (305.3 S m−1) alongside record‐breaking mechanical properties (21.2 GPa in Young's modulus, 392.1 MPa in tensile strength). Also, the advantage of ULGO in constructing commercially desirable thick graphene films with high thermal conductivity is demonstrated (≈100 µm, 1576.1±26.7 W m−1 K−1). This new strategy based on new findings in mechanism provides a highly efficient route to enlarge lateral size and expand physical properties of graphene oxide.

Monolithic robust hybrid sponge with enhanced light adsorption and ultrafast photothermal heating rate for rapid oil cleaning

It remains a significant challenge to develop a photothermal adsorbent with a heating response as fast as a joule-heating adsorbent and simultaneously possessing excellent mechanical stability and reusability for rapid oil cleaning. Here, we report a novel monolithic design to fabricate a photothermal hybrid sponge for rapid oil cleaning by integrating graphite interlayer compounds as photothermal units into the three-dimensional photothermal network of carbon nanotubes. This unique monolithic design enabled the hybrid sponge to present excellent photothermal performance: firstly, the superhydrophobic hybrid sponge has low thermal resistance resulting from the defectless surface; secondly, the photothermal units were weaved in the photothermal network, preventing detachment in the cycling and providing ultrafast photothermal heating rate. The hybrid sponge rises to 81 °C in merely 25 s under irradiation (1 Sun), superior to most photothermal oil adsorbents reported so far. This study provides a new structural design for constructing photothermal adsorbents with a fast-heating response for rapid crude oil cleaning.

Kinetic Analysis of Bio-oil Derived Hierarchically Porous Carbon for Superior Li+/Na+ Storage.

Herein, an efficient biomass utilization is proposed to prepare bio-oil-derived carbon (BODPC) with hierarchical pores and certain H/O/N functionalities for superior Li+/Na+ storage. Kinetic analyses reveal that BODPC has similar behavior in the electrochemical Li+ and Na+ storage processes, in terms of physical adsorption (Stage I), chemical redox reactions with surface functionalities (Stage II), and insertion into the graphitic interlayer (Stage III). Promisingly, BODPC exhibits a high reversible specific capacity (1881.7 mAh g-1 for Li+ and 461.0 mAh g-1 for Na+ at 0.1 A g-1), superior rate capability (674.1 mAh g-1 for Li+ and 125.7 mAh g-1 for Na+ at 5.0 A g-1), and long-term cyclability. More notably, the BODPC with highly capacitive-dominant behavior would hold great promise for the applications of high-power, durable, and safe rechargeable batteries/capacitors.

Mechanism for the Intercalation of Aniline Cations into the Interlayers of Graphite.

The dynamic behaviors of aniline cation (ANI+) intercalating into graphite interlayers are systematically studied by experimental studies and multiscale simulations. The in situ intercalation polymerization designed by response surface methods implies the importance of ultrasonication for achieving the intercalation of ANI+. Molecular dynamics and quantum chemical simulations prove the adsorption of ANI+ onto graphite surfaces by cation–π electrostatic interactions, weakening the π–π interactions between graphene layers. The ultrasonication that follows breaks the hydrated ANI+ clusters into individual ANI+. Thus, the released positive charges of these dissociative cations and reduced steric hindrance significantly improve their intercalation ability. With the initial kinetic energy provided by ultrasonic field, the activated ANI+ are able to intercalate into the interlayer of graphite. This work demonstrates the intercalation behaviors of ANI+, which provides an opportunity for investigations regarding organic-molecule-intercalated graphite compounds.

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.

Investigating the output performance of triboelectric nanogenerators with single/double-sided interlayer

To enhance the electric outputs of triboelectric nanogenerators (TENG), embedding interlayers provides an effective strategy. However, the proposed researches mainly focus on negative interlayers, such as polyimide (PI), and the influence of the PI thickness and other materials on the output performance of TENGs has not been systematically investigated. Here, PI interlayers with different thicknesses were used to perform experiments. According to the experimental results, the electric outputs of TENGs with the rise of PI thickness decrease, and compared to a traditional TENG, the output voltage of the TENG with a 0.01 mm thick PI interlayer increases by a ratio of 5. Then, the influence of interlayers into the positive electrode on the electric outputs of TENGs is studied. The experimental results manifest that the output voltage of the TENG with a graphite paper interlayer is 1.26 times higher than that of TENGs without interlayers. Finally, the output performance of TENGs with negative and positive interlayers was explored. Due to the coupling effect of PI and graphite paper interlayers, the electric outputs of the TENG declines. The work can be of great significance as a design reference for developing high-performance TENGs.

Zinc-guided 3D graphene bulk materials for high-performance binder-free anodes of potassium-ion batteries

Potassium ion batteries are promisingly proposed for the large cale energy storage. However, potassium with large ion radius causes severe volumetric expansion of anodes during charging, which deteriorates the rate and the cycling performances of batteries. Herein, a honeycomb-like graphene monolith with rich micropores is prepared. The monolith is further applied as the binder-free anode for potassium ion batteries. It shows the remarkable rate performance with a capacity of 180 mAh g−1 at a current density of 10 A g−1, and it can stably run for 4000 cycles at 1 A g−1. Kinetic studies and theoretical analyses reveal that the large graphitic interlayer spacing, the nitrogen doping, and the 3D network structure can significantly promote the diffusion rate, the absorption of potassium ions, as well as the transports of electrons and ions. The graphene-based potassium ion batteries can thus boost the development of renewable energies.

Petroleum pitch derived carbon as both cathode and anode materials for advanced potassium-ion hybrid capacitors

Potassium-ion hybrid capacitors (PIHCs) are considered as ideal devices for large-scale electrochemical energy storage because of their low reduction potential, environmental-friendly and abundant potassium resources in the earth. However, the simple and eco-friendly preparation of well-matched cathode and anode materials is still with great challenges. With the same petroleum pitch (with asphaltenes removed by n-heptane) as carbon source, herein we reported low-cost and non-corrosive processes to construct two carbon materials, namely soft carbon nanosheets (SCNs) and active carbon nanosheets (ACNs), as anode and cathode materials, respectively, to assemble high performance PIHCs. The SCNs with expanded graphitic interlayer spacing of 0.396 nm and abundant surface defects present super rate capability and high pseudocapacitive proportion. In addition, the ACNs with hierarchical pores structure, which accelerates the adsorption and transport of electrolyte ions, exhibit outstanding capacitive performance. By optimizing the voltage window and mass ratio of cathode and anode, the SCNs//ACNs PIHCs deliver a high energy density of 124.0 Wh kg−1 at a power density output of 198.9 W kg−1 and an ultralong lifespan over 9000 cycles. This work opens a new avenue to increase the value-added utilization of petroleum pitch for innovative potassium-based energy storage technology.

Polymerization Initiated by Graphite Intercalation Compounds Revisited: One-Pot Synthesis of Amphiphilic Pentablock Copolymers

This study reports the first attempt to employ a potassium–graphite intercalation compound (KC24) as an initiator for the one-pot synthesis of a multi-block copolymer. The results obtained show that KC24 successfully initiated the copolymerization, leading to a copolymer consisting of poly(styrene), poly(methyl methacrylate) and poly(ethylene oxide) blocks. When all three comonomers were introduced simultaneously or in a specific sequence, the resulting copolymers had molecular masses in the range between 170,000 Da and 280,000 Da. Their composition was investigated by size-exclusion chromatography with triple detection (dRI/UV/IR) and 1H-NMR. The analyses indicated that all copolymers were enriched in methyl methacrylate (50–66 mol%) despite the fact that the comonomers were added in equimolar amounts. Due to the layered structure of the initiator, the polymerization took place in the graphite interlayer spaces and lead to extensive delamination, indicating at the potential to produce in situ graphite/copolymer composite materials.

High Graphitic Carbon Derived from Coconut Coir Waste by Promoting Potassium Hydroxide in the Catalytic Graphitization Process for Lithium-Ion Battery Anodes

Graphite is a critical material for lithium-ion battery (LIB) anodes. However, its fabrication using a simple route and sustainable carbon sources still remains a great challenge. In this current work, we fabricate high graphitic carbon from coconut coir waste by combining potassium hydroxide (KOH) and a Ni-based catalyst in a one-pot graphitization process. The graphitic carbon (1200-ANi-KOH) shows good electrochemistry performance as the anode of LIB with a specific capacity of 397.60 mA h/g, exceeding commercial graphite (339.90 mA h/g) and a high graphitic degree of IG/ID (1.99) with a surface area of 162.31 m2/g. The synergistic effect of K and Ni metal interaction with amorphous carbon promotes internal heating and catalytic graphitization, resulting in an ordered carbon structure and a greater area of graphitic structure. Ion diffusion in the graphite interlayer was found to be the dominant ion storage mechanism at 1200-ANi-KOH, which is comparable to the commercial graphite mechanism. Finally, this simple one-pot graphitization process succeeded in converting coconut coir waste into a graphitic material with a high graphitization degree and excellent LIB anode performance.

Essential Electronic Properties of Stage-1 Li/Li+-Graphite-Intercalation Compounds for Different Concentrations

We use first-principles calculations within the density functional theory (DFT) to explore the electronic properties of stage-1 Li- and Li+-graphite-intercalation compounds (GIC) for different concentrations of LiCx/Li+Cx, with x = 6, 12, 18, 24, 32 and 36. The essential properties, e.g., geometric structures, band structures and spatial charge distributions are determined by the hybridization of the orbitals, the main focus of our work. The band structures/density of states/spatial charge distributions display that Li-GIC shows a blue shift of Fermi energy just like metals, but Li+-GIC still remains as in the original graphite or exhibits so-called semi-metallic properties, possessing the same densities of free electrons and holes. According to these properties, we find that there exist weak but significant van der Waals interactions between interlayers of graphite, and 2s-2pz hybridization between Li and C. There scarcely exist strong interactions between Li+-C. The dominant interaction between the Li and C is 2s-2pz orbital-orbital coupling; the orbital-orbital coupling is not significant in the Li+ and C cases, but dipole-diploe coupling is.

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.

Device level reversible potassium intercalation into bilayer graphene

Electrochemical intercalation and storage of alkali metal ions into the graphite interlayer space is a key ingredient for commercial rechargeable ion batteries. While this has been exceptionally fruitful for lithium, the use of other more abundant chemical species such as potassium has fallen behind due to their less favorable ionic radius and host–guest interactions. Here, we deploy a device level on-chip cell architecture to study the reversible intercalation of potassium into the single van der Waals gallery of a graphene bilayer at room temperature and monitor in a time-dependent manner the electronic properties of the graphene bilayer during the insertion and extraction processes. The potassium diffusion is highly reversible and a charge transfer up to about 2.5 × 1013 cm−2 is achieved. The diffusion coefficient well exceeds 10−7 cm2 s−1 at room temperature, an order of magnitude larger than previously reported values in graphite and other compounds.

Structural degradation of graphite anode induced by dissolved manganese ions in lithium-ion batteries

Manganese (Mn) species deposited on anodes have been identified as one of the primary sources of capacity and power fading in Li-ion batteries (LIBs). Previous studies have overwhelmingly focused on the effect of Mn species present on the anode surface on the electrochemical performance of LIBs and their relation to chemical degradation of the solid electrolyte interphase (SEI). This study investigates the role of Mn ions dissolved in electrolytes in the structural degradation of a graphite anode. X-ray diffraction results find evidence for the hypothesis that dissolved Mn ions could co-intercalate into the graphite structure at an early stage of the Li-ion intercalation. Furthermore, Raman spectroscopy results demonstrate severe local surface disordering of graphite in the presence of Mn ions. Calculations based on density functional theory (DFT) support the experimental findings, revealing that Mn co-intercalated into the graphite structure inhibits the expansion of the graphite interlayers upon Li-ion intercalation. Results from this study provide new insights into the current mechanisms of the degradation of manganese-based cathode–graphite battery cells. The proposed mechanism of graphite structural degradation induced by Mn ions can help researchers and engineers design LIBs with longer lifespans.

Selective transport of water molecules through interlayer spaces in graphite

Interlayer space in graphite is impermeable to ions and molecules, including protons. Its controlled expansion would find several applications in desalination, gas purification, high-density batteries, etc. In the past, metal intercalation has been used to modify graphitic interlayer spaces; however, resultant intercalation compounds are unstable in water. Here, we successfully expanded graphite interlayer spaces by intercalating aqueous KCl ions electrochemically. Our spectroscopy studies provide clear evidence for cation-π interactions explaining the stability of the devices, though weak anion-π interactions were also detectable. The water conductivity shows several orders of enhancement when compared to unintercalated graphite. Water evaporation experiments further confirm the high permeation rate. There is weak ion permeation through interlayer spaces, up to the highest chloride concentration of 1 M, an indication of sterically limited transport. In these very few transported ions, we observe hydration energy-dependent selectivity between salt ions. These strongly suggest a soft ball model of steric exclusion, which is rarely reported. These findings improve our understanding of molecular and ionic transport at the atomic scale.

“Sticky” carbon coating enables high-area-capacity lithium storage of silicon-graphitic carbon hybrid

Pulverization and surface instability have been identified as the main impediments to the application of Si anodes in high-energy lithium-ion batteries (LIBs). In this study, a Si-graphitic carbon hybrid (SiG) is created via embedding Si nanoparticles in between expanding graphite interlayers, thus to be adopted as a model system to unravel structure-properties relations for LIBs applications. We explore the impact of artificial surface coating layers on the lithium cycling performance of SiG particles. In comparison with native SiG and carbon-coated SiG (CC-SiG), we find that the “sticky-carbon” coating, i.e., an epoxy-rich layer on top of the carbon coating, gave rise to superior cycle performance. In the “sticky carbon” coated SiG (SCC-SiG), the surface chemistry appears to have a pivotal role in both alleviating electrode disintegration and forming a favorable SEI rich in fluorine-polymers. These positive findings are examined in electrodes with mass loading ranging from 1.0 to 5.0 mg/cm2, achieving area capacities up to ∼5.0 mAh/cm2. A full cell adopting >6 mg/cm2 LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode and SCC-SiG delivers stable cycling performances. It is hence unraveled that the carbon coating layer with reactive surface groups on the top is an unrecognized key for wide range of Si-based anodes.

Molecular Structural Influence of Glymes on Co-Intercalation Behavior of Solvated Li+ in Graphite Electrodes

Solvated Li+ ions are intercalated into graphite in a dilute glyme-based solution and this reaction has attracted much attention for use in advanced lithium-ion batteries due to their high rate capability. In this study, Li+ co-intercalation behaviors in asymmetric glymes (CH3O(CH2CH2O) n C4H9, n = 2 or 3) were investigated and compared to those in symmetric glymes (CH3O(CH2CH2O) n CH3, n = 1–4). Despite the large alkyl sidechains of asymmetric glymes, co-intercalation reactions of solvated Li+ proceeded as well as those in symmetric glymes. In charge and discharge measurements, the reversible capacities in asymmetric glyme-based solutions were smaller than those in symmetric glymes except for tetraglyme, which showed the lowest reversible capacity. There was no clear difference in the sandwich distances of glyme-Li-GICs calculated from X-ray diffraction patterns of both symmetric and asymmetric glymes. Therefore, solvated Li+ ions with asymmetric glymes occupied more space in the graphite interlayer compared to symmetric glymes, which resulted in smaller reversible capacities for asymmetric glymes. These results demonstrate the influence of solvent-related structures of GICs on reversible capacities for co-intercalation systems.