Graphite Foil Research Articles

Laser irradiation of graphite foils as robust current collectors for high-mass loaded electrodes of supercapacitors

Laser irradiation of graphite foils as robust current collectors for high-mass loaded electrodes of supercapacitors

Layered graphite foil/poly(3,4-ethylenedioxythiophene) electrode-enabled flexible electrochemical capacitors with observably boosted performances

• A simple mechanically exfoliated method is proposed to prepare LGF current collector. • LGF shows a unique layered microstructure with observably enlarged surface area. • The electrochemical properties of PEDOT are significantly affected by polymerized parameters. • LGF-constructed electrodes show observably enhanced electrochemical properties. • LGF/PEDOT flexible EC features high electrochemical properties and mechanical flexibility. Seeking a cheap flexible current collector and further enhancing charge storage capacity are still two crucial challenges to promote the practical applications of flexible electrochemical capacitors. In this work, we first fabricate layered graphite foil (LGF) current collector from low-cost GF by a facile and scalable mechanically exfoliated method. And meanwhile, the electropolymerization parameter-dependent supercapacitive performance of the poly(3,4-ethylenedioxythiophene) (PEDOT) as the electroactive material is investigated in detail. Electrochemical measurements verify that the electrochemical performances of PEDOT are notably improved via optimizing the electropolymerization parameters. More importantly, the capacitive behaviors of PEDOT electrodes are further observably boosted through using LGF current collector compared to GF, attributed to the 3D interface established between the PEDOT films and LGF. The LGF/PEDOT electrodes yield an areal-specific capacitance of 122.3 mF cm −2 and achieve high rate capability. Furthermore, a symmetrical electrochemical capacitor assembled by the LGF/PEDOT electrodes show superior electrochemical capacitive properties and highly mechanical flexibility. Even more impressively, it retains 92.1% and 94.3% of initial capacitance after 10,000 charge–discharge cycles and harsh mechanical deformation for 500 times, respectively. The LGF we develop not only ensures its high flexibility but distinctly enhances its electrochemical properties.

A novel approach for the recovery and cyclic utilization of valuable metals by co-smelting spent lithium-ion batteries with copper slag

Achieving efficient and low-cost recycling of spent lithium-ion batteries (LIBs) is of great significance to the sustainable development of the clean energy industry and energy metal resources. This study developed a co-smelting process for the simultaneous recovery of valuable metals from spent LIBs and copper slag by using copper slag as the only flux, CaCl2 as the chlorine donor, and anode graphite and aluminium foil in spent LIBs as reductants. Co, Cu, Ni and Fe from spent LIBs and copper slag are recovered in the form of alloys. The Li is transferred from the slag to the gas phase through the chlorination reaction, which efficiently separates and enriches Li during the co-smelting process. Under the optimized conditions, the recoveries of Co, Cu, Ni and Fe were 99.13 %, 98.04 %, 99.30 % and 97.98 %, respectively, and the Li volatilization rate was 97.86 %. The influences of the processing parameters on the metal recovery and Li volatilization rate were assessed. The reaction mechanism was elucidated based on thermodynamics and phase transitions. In addition, a strategy for the preparation of high value-added products from the smelted products was provided. Lithium-containing dust can be used to prepare battery grade Li2CO3, and smelting slag can be used to prepare glass ceramics. The proposed co-smelting process is feasible for the comprehensive recovery of valuable metals from spent LIBs and copper slag, and thus, it has good application prospects and advantages. Meanwhile, the problem of difficulty in lithium recovery in the traditional process is solved.

Helium Dielectric Barrier Discharge Plasma Jet (DBD Jet)-Processed Graphite Foil as Current Collector for Paper-Based Fluidic Aluminum-Air Batteries

A helium (He) dielectric barrier discharge plasma jet (DBD jet) was used for the first time for treating graphite foil as the current collector of a paper-based fluidic aluminum-air battery. The main purpose was to improve the distribution of the catalyst layer through modification and functionalization of the graphite foil surface. The plasma functionalized the graphite foil surface to enhance the wettability where the more hydroxyl could be observed from XPS results. The 30 s-He DBD jet treatment on the graphite foil significantly improved the battery performance. The best current density of 85.6 mA/cm2 and power density of 40.98 mW/cm2 were achieved. The energy density was also improved to 720 Wh/kg.

Polymer-Garnet-Based Composite Cathodes for Solid-State Li Batteries

All-solid-state lithium batteries (ASSLBs) can potentially outperform conventional Li-ion batteries with liquid or polymer electrolyte. One example for solid electrolytes is the garnet-type oxide Li7La3Zr2O12 (LLZO). LLZO has a wide electrochemical window, stability vs. lithium, and good ionic conductivity at room temperature. The cathode in ASSLBs is manufactured from a cathode active material (CAM), such as LiCoO2 (LCO). The efficiency of Li-ion storage can be improved by the use of a composite cathode consisting from a CAM and an ion-conducting ceramic, e.g. LCO/LLZO. In such a composite cathode, LLZO delivers Li-ions through the whole bulk enhancing the volumetric loading of LCO. In this work the addition of polymer electrolyte into LCO/LLZO composite cathode was proposed, aiming at further increase of cell performance due to facilitation of CAM usage, similar to the approach of manufacturing of polymer-ceramic electrolytes. They are fabricated mostly by tape casting of slurry with polymer matrix, ceramic filler and a solvent. An alternative technology includes free sintering of tape-casted LCO/LLZO porous network and subsequent infiltration by liquid or polymer electrolyte. Free sintering of LCO/LLZO composite requires relatively high temperature and/or long sintering time. This results in loss of volatile Li with decrease in electrochemical performance.In the present work the LCO/LLZO composite cathode was manufactured in a powder-based process by Field-Assisted Sintering Technique also known as Spark Plasma Sintering (FAST/SPS). Fast heating (100°C/min and higher) and application of mechanical pressure during FAST/SPS enable reduction of sintering temperature and processing time needed for fabrication of nearly-fully-dense composite.[1] Thereby, Li evaporation and grain growth can be significantly reduced. This technology was used in our previous work for fabrication of half-cells with dense LLZO electrolyte and dense LCO/LLZO composite cathode. However, the appearance of side phase after sintering at low pressure and a residual porosity was observed. The reason for that was partial reduction of oxides by carbon originated from graphite foil in FAST/SPS setup. In the presented work, the graphite foil was replaced by carbon-free mica foil. This measure enabled FAST/SPS sintering of porous LCO/LLZO network without side phase formation. The obtained porous skeleton was infiltrated with polymer electrolyte to fabricate a polymer-ceramic composite cathode. The cathode was assembled with an anodic half-cell consisting of dense FAST/SPS-sintered LLZO electrolyte and attached indium (In) foil used as anode. The ASSLB with polymer-ceramic composite cathode showed significantly lower interfacial impedance and remarkably higher area-specific storage capacity as compared to the similar ASSLBs with pure ceramic (porous or dense) composite cathodes. Thus, the functionality and the advanced storage capacity of the proposed polymer-ceramic cathode and related ASSLB architecture were demonstrated.[2]

Preparation of WO3 Films on Titanium and Graphite Foil for Fuel Cell and Supercapacitor Applications by Electrochemical (Cathodic) Deposition Method

Preparation of WO3 Films on Titanium and Graphite Foil for Fuel Cell and Supercapacitor Applications by Electrochemical (Cathodic) Deposition Method

Superconducting-like and magnetic transitions in oxygen-implanted diamond-like and amorphous carbon films, and in highly oriented pyrolytic graphite

In our previously published work, we have reported colossal magnetoresistance, Andreev oscillations, ferromagnetism, and granular superconductivity in oxygen-implanted carbon fibers, graphite foils, and highly oriented pyrolytic graphite (HOPG). In this follow-up research, more results on these oxygen-implanted graphite samples are presented. We show results from transport measurements on oxygen-implanted diamond-like carbon thin coatings, amorphous carbon films, and HOPG. Significantly, a three-order magnitude drop in the electrical resistance of the oxygen-implanted diamond-like carbon films is observed at the 50 K temperature that we have previously reported for the transition to the superconducting state. Below 50 K, the films’ resistance oscillates between the high and low resistance states, less when the sample is under a transverse magnetic field. This metastability between the insulating and superconducting-like states possibly reflects the evolution of the amplitude for the superconducting order parameter also known as the longitudinal Higgs mode. Transitions to low resistance state and metastability are also observed for amorphous carbon films. Finally, the HOPG samples’ resistance have a thermally activated term that can be understood on the basis of the Langer–Ambegaokar–McCumber–Halperin model applied to narrow SC channels in which thermal fluctuations can cause phase slips. We also find that in oxygen-implanted carbon materials, the electron charge and spin correlations do not compete and their interplay rather facilitates the emergence of high-temperature superconductivity, and thus, additional unexpected effects like Heisenberg spin waves and magneto-structural transitions are observed.

Electrochemical Synthesis of Coatings Based on Polydiphenylamine-2-carboxylic Acid on Anodized Graphite Foil Modified by Graphene Nanosheets and Manganese Oxides

Electrochemical Synthesis of Coatings Based on Polydiphenylamine-2-carboxylic Acid on Anodized Graphite Foil Modified by Graphene Nanosheets and Manganese Oxides

Perylenediimide/Graphite Foil‐Based Electrode Materials with Outstanding Cycling Stability for Symmetric Supercapacitor Device Architectures

Herein, pyridine functionalized naphthalenediimide (NDI‐Py) and perylenediimide (PDI‐Py) derivatives are synthesized and characterized using modern techniques. NDI‐Py and PDI‐Py in combination with graphite foil (GF) are employed as electrode materials for supercapacitor (SC) applications. Under the three‐electrode system, the electrode materials based on NDI‐Py/GF and PDI‐Py/GF composite electrode exhibit specific capacitance (C sp) of about 118 and 179 F g−1 at 5 mV s−1 from cyclic voltammetry (CV) and 132 and 197 F g−1 at 1 A g−1 from galvanostatic charge–discharge (GCD) curves. The electrochemical performance behaviors of these electrodes are mainly contributed by surface reactions along with the Faradaic redox reactions such as pseudocapacitance. The corresponding two‐electrode symmetric SC device based on PDI‐Py/GF//PDI‐Py/GF exhibits a high energy density of 46 Wh kg−1 at a power density of 3060 W kg−1 at 1 A g−1 current density, which is further retained at 13 Wh kg−1 and 15 300 W kg−1 energy and power density, respectively, at 5 A g−1 current density. Moreover, the symmetrical SC device based on PDI‐Py/GF//PDI‐Py/GF shows outstanding cyclic stability for 10 000 charge–discharge cycles while maintaining 95% of the original capacitance.

TiO2 nanorods decorated on RGO sheet for an excellent energy storage performance

Herein, we report nanocomposite of titanium dioxide (TiO2) nanorods decorated reduced graphene oxide (TiO2/RGO) nanocomposite prepared using the simple, one-pot hydrothermal route for electrode material in supercapacitor applications. A systematic comparison study was carried out for the TiO2 nanorods coated on graphite foil in presence of alkaline media 3 M KOH, NaCl, and Na2SO4 using the three-electrode method. The TiO2/RGO composite shows an excellent specific capacitance (Csp) of 330 Fg-1 at the discharge current density 0.5 Ag-1 in presence of 3 M KOH electrolyte solution. The obtained highest specific capacitance values in order by various electrolytes are observed as KOH > NaCl > Na2SO4. The long-term cycle stability of charge and discharge cycle at current density 0.5 Ag-1 over 1000 cycles and only 8% decay in the specific capacitance of TiO2/RGO nanocomposite was observed in 3 M KOH electrolyte. The improved electrochemical performance TiO2/RGOcomposite in presence of KOH electrolyte is shown to be the most suitable electrode for the supercapacitors.

Electrochemical behavior of polydiphenylamine-2-carboxylic acid and its hybrid nanocomposites with single-walled carbon nanotubes on anodized graphite foil in lithium aprotic electrolyte

Electrochemical properties of novel electrode coatings based on polydiphenylamine-2-carboxylic acid (PDPAC) and its hybrid nanocomposites with single-walled carbon nanotubes (SWCNT) were studied for the first time. PDPAC and SWCNT/PDPAC nanomaterials were synthesized via in situ oxidative polymerization in the homogeneous acidic medium (in 5 М H2SO4) and in the heterophase system in an alkaline medium (in a mixture of chloroform and NH4OH). Hybrid electrodes are flexible strips of anodized graphite foil (AGF) with electroactive layers of stable suspensions of polymers and nanocomposites in formic acid (FA) formed on their surface, without any binding and electrically conductive additives. The roughened surface and presence of oxygen-containing groups on the AGF surface provide good adhesion of the electroactive coatings. The use of the modified graphite foil as a current collector leads to a significant increase in the electrochemical capacitance and stability of the coatings. The specific electrochemical capacitance of electroactive coatings on AGF depends on the reaction medium pH for the coatings synthesis and reaches 421, 258, 150 F∙g−1 for PDPACac and 438, 350, 259 F∙g−1 for SWCNT/PDPACac, prepared in an acidic medium (pH = 0.3), and 202, 106, 63 F∙g−1 for PDPACalk and 278, 191, 129 F∙g−1 for SWCNT/PDPACalk, obtained in an alkaline medium (pH = 11.4), at charge-discharge currents of 0.5, 1.5, 3.0 mА·cm−2, respectively, in 1 М LiClO4 organic electrolyte in propylene carbonate. The PDPAC and SWCNT/PDPAC electroactive coatings are characterized by high stability of electrochemical properties at Coulombic efficiency up to 96–100%. The main contribution to the electrochemical capacitance is provided by the charging of the electric double layer.

Bimetallic NiFe hydroxide coated onto commercial graphite foil as efficient supercapacitor electrode

Attaining high specific energy meanwhile detaining the specific power achieved, is a significant challenge faced in modern era supercapacitors. Coupling two highly electroactive metal ions together in an array, holds sanguinity to attain high energy and power proficiencies. Ni(OH)2 being an economical battery-grade electrode material, has respectable charge-storage competence, but suffers from sluggish ion mobility. Benefitting from the lamellar structure and easy tunability of layered double hydroxide (LDH), swifter ion/electron mobility and improved conductivity is achievable. Herein this work, conductive iron (Fe) species incorporated with nickel hydroxide matrix to form LDH structure through facile coprecipitation strategy is proposed. The upshot of varying nickel iron ratio on the structural, functional, morphology and electrochemical characteristics is inspected. The best composition had an admirable specific capacity of 381 C g−1 (1368 F g−1) at 1 A g−1 with an ability to retain 87.5% of the initial capacity even after 5000 successive charge-discharge cycles. The symmetric supercapacitor developed using the optimal NiFe LDH over commercial graphite foil, furnishes a specific energy of 66.13 W h kg−1 at specific power 1483 W kg−1. Moreover, the corrosion and radiation inertness of commercial graphite foil, widens the scope of utilization of the fabricated supercapacitor.

Vertically aligned graphene prepared by the electrochemical anodization of graphite foil for supercapacitor electrodes

Vertically aligned graphene (VAG) improves the specific capacitance of electric double layer capacitor (EDLC) electrodes, because VAGs increase the specific surface area of electrode and promote ion diffusion. Herein, we demonstrate a facile approach for preparing the VAGs with outstanding areal specific capacitance by electrochemical anodization of graphite foil (GF). As the anodizing time increases, the graphite layers in the anodized GF (AGF) electrodes expand due to ion intercalation and bubbles. Each graphite layer is vertically aligned, resulting in the formation of VAG sheets on the GF surface. The AGF electrode exhibits an excellent specific areal capacitance of 2.79 Fcm−2 at a current density of 2 mAcm−2, which is higher than that of the GF electrode by a factor of 17.43. The EDLC device using AGF electrodes exhibits an outstanding specific areal capacitance of 1.43 Fcm−2 at a current density of 2 mAcm−2 and a favorable cycling stability retaining 90% of its initial capacitance after 2000 cycles at a current density of 20 mAcm−2. This AGF electrode fabrication method is simple, cost-effective, and eco-friendly. We believe that the fabrication of AGF electrodes may be a significant contribution to the development of high-performance supercapacitors as well as the eco-friendly energy industry.

Synthesis of h-BN through spark plasma sintering with urea and boric acid as the starting materials

This present work investigated the capability of the spark plasma sintering (SPS) method to synthesize h-BN powders from urea and acid boric mixture without any extra additives. Accordingly, the 1:1 M ratio of the starting materials was mixed through a simple method at the aqueous solution and then dried at a hot plate (80 °C) while it was stirred. Subsequently, the mixture was directly inserted to a graphite mold and the sintering process was performed with the constant pressure of 10 MPa and the initial vacuum condition of 19 Pa, as well as the maximum temperature of 1950 °C. Then, the obtained powders were ground and the graphite foils as the separators were removed from the sample. The prepared thin layer of the specimen was milled by the agate mortar. The characterization of the obtained powders was done without any post treatment. The XRD patterns demonstrated only h-BN peaks, as the applied high sintering temperature removed any impurities at this system according to the vacuum condition. The FESEM images of the synthesized powders demonstrated the formation of flower-like h-BN powders. Moreover, the HRTEM images of the prepared powders showed the formation of a highly crystalline h-BN.

Electrochemical deposition of PEDOT/MoS2 composite films for supercapacitors

Composite materials based on conducting polymers and transitional metal chalcogenides have attracted considerable attention as electrode materials for supercapacitors. Molybdenum disulfide is a layered transitional metal dichalcogenide extensively researched in energy storage and conversion applications, and poly(3,4-ethylenedioxythiophene) (PEDOT) is an intrinsically conducting polymer that can act as a conductive matrix. We propose a single-step electrochemical deposition of PEDOT/MoS2 composite materials from the dispersion containing commercially available MoS2 platelets and EDOT monomer. Potentiodynamic, galvanostatic, and potentiostatic modes are all suitable for synthesis of the materials with predominant content of MoS2, which is attached to the current collector via conducting PEDOT matrix. The materials can work in various water-based electrolytes and combine capacitor-like and redox pseudocapacitive response. The composites deposited on graphite foil in assembled asymmetric cells with Kynol carbon cloth counter-electrode deliver up to 870 mF cm−2 areal capacitance in LiClO4 aqueous solution at a current density of 1 mA cm−2 due to combined capacitive input of both components.

Fracture peculiarities and high-temperature strength of bulk polycrystalline boron

We report the mechanical behavior of a bulk boron ceramic prepared by spark plasma sintering of commercially-available β-boron powder. In order to fabricate polycrystalline boron ceramic, we used a protective tantalum foil reacted with carbon from the graphite die or graphite foil forming a thin layer of TaB2 and TaC covering the boron specimen. This is the first study to show the high-temperature flexural strength, toughness, and Young's moduli of boron up to 1400 °C. At 1600 °C and above, boron will react with testing environment forming an outer shell.The flexural strength and fracture toughness at room temperature reached an average of 340 MPa and 4.1 MPa m1/2, respectively. Despite showing clear signs of plastic deformation on the strain-stress curves, the yield strength of the monolithic boron ceramic exceed 1 GPa at 1200 °C. It was determined that fracture at elevated temperatures follows a quasi-transgranular mechanism, where the sub-grains of the boron fracture as plate-like structures. An interpretation for the observed fracture behavior was proposed.

Helium Dielectric Barrier Discharge Plasma Jet (Dbdjet) Processed Graphite Foil as Current Collector for Paper-Based Fluidic Aluminum-Air Batteries

Helium Dielectric Barrier Discharge Plasma Jet (Dbdjet) Processed Graphite Foil as Current Collector for Paper-Based Fluidic Aluminum-Air Batteries

Promising Material Based on Paraffin‐Impregnated Graphite Foil with Increased Electrochemical Stability for Bipolar Plates of Vanadium Redox Flow Battery

AbstractThe development of effective power sources is a major challenge for global energetics. Among various power sources, the redox flow batteries (RFB) have distinctive feature due to the flexibility of adjusting the capacity and power to the needs of the customer. The vanadium RFBs are already available in the stationary storage market, but their widespread distribution requires a significant reduction in the levelized cost of storage (LCOS). Therefore, a number of works are devoted to the development of more available materials for the RFB. The utilization of affordable graphite foil (GF) for fabricating bipolar plates as well as a method for increasing its electrochemical stability by a fluoropolymer were earlier proposed. In this work, we have demonstrated an approach to significantly reduce the porosity of GF by impregnation with paraffin P‐2. Such modification significantly increases GF stability and retains the RFB performance at a high level comparable to commercial graphite.

Development of Ti PVD Films to Limit the Carburization of Metal Powders during SPS Process

Spark plasma sintering technique is used for the fabrication of dense materials with a fine-grained microstructure. In this process, a powder is placed into a graphite mold and a uniaxial pressure is applied by two graphite punches. A graphite foil is inserted between the punches and the powder and between the mold and the powder to ensure good electrical, physical and thermal contact. One of the major drawbacks during sintering of metal powders is the carburization of the powder in contact with the graphite foils. In this study, a PVD coating of titanium was applied on the graphite foils in contact with the metal powder (pure iron). The results are promising, as the investigations show that the application of a Ti PVD film of 1.5 and 1.1 µm thickness is effective to completely avoid the carburization of iron powder. Carbon diffuses inside the PVD film during sintering. In parallel, iron diffusion was revealed inside the Ti coating of 1.5 µm thickness. On the other hand, a Ti PVD film of 0.5 µm thickness provides a protection against carbon diffusion just on the sides in contact with the mold, proving that the coating thickness represents an important parameter to consider.

Ethanol electro-oxidation by Pt/r(GO-ZSM)/ graphite foil

Ethanol electro-oxidation by Pt/r(GO-ZSM)/ graphite foil