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Recently, due to the rapid increase in the demand for artificial graphite, there has been a strong need to improve the productivity of artificial graphite. In this study, we propose a new efficient process by eliminating the carbonation stage from the existing process. The conventional graphite manufacturing process usually involves a series of stages: the pulverization of needle-type coke, the granulation of pitch and coke premix, carbonation, graphitization, and surface treatment to compensate voids formed within particles. The process seems time-consuming and costly. Therefore, in our proposed shortened process, we have eliminated the carbonization stage. Instead of petroleum-derived pitch, coal tar pitch was employed. Coal tar pitch has a lower softening point than binder pitch. Apart from the cost-effectiveness of the process, it has enhanced the properties of artificial graphite by a uniform coating using a lower amount of hard carbon. In addition, the whole manufacturing time and cost was reduced by 12 h and 20% due to the skipped manufacturing step, respectively. It was observed that the artificial graphite produced by the newly proposed shortened process had improved physical properties related to the density and graphitization degree, and also showed an improvement in electrochemical performance. Raman 3D mapping and the electrochemical evaluation of artificial graphite were mainly used to compare the physical properties. This shortened process not only reduces the manufacturing cost, but also contributes to the improved performance of lithium-ion battery anode material. [ABSTRACT FROM AUTHOR]

As the demand for artificial graphite for lithium-ion battery (LIB) anode materials is on the rise, technologies for optimizing the manufacturing processes and reducing the production costs of artificial graphite are crucial. At the same time, globally, regulations on the generation of harmful volatile substances during the artificial graphite production process are also becoming increasingly stringent. In this study, we focused on a continuous kneading process that minimizes the emission of volatile substances during the manufacturing of artificial graphite. To this end, a carbonized material was first prepared from a mixture of needle coke and binder pitch and processed at 3200 °C using two types of co-rotating twin-screw extruder-based continuous kneading equipment to ultimately obtain artificial graphite. The physical properties of the carbonized as well as graphitized materials were analyzed, which revealed the superior performance of the LIB anode material, namely a discharge capacity of greater than or equal to 350 mAh/g, and an initial efficiency of 91% or higher. Thus, a continuous kneading manufacturing process that emits less harmful volatile substances and provides artificial graphite with sufficient battery performance was demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: In situ preparation of carbon nanotubes on the surface of spherical graphite particles is made by chemical vapor deposition, resulting in an “urchin-like” hybrid material. TEM and SEM images show that carbon nanotubes are herringbone with turbulent layered structure, less than 100nm in diameter and several micrometers in length in the average. The hybrid''s use as an anode material in lithium ion batteries is examined using constant current charge–discharge tests, which prove that carbon nanotubes oriented on the surface effectively improve the reversible capacity. Cyclic voltammogram shows that there is no cathodic peak for the reaction of the Fe catalyst with Li+ in the charge-charge process in 0.0–1.6V vs. Li/Li+ potential range. [Copyright &y& Elsevier]

Novel composites of silicon monoxide, pyrolytic carbon and carbon nanofiber (SiO/PyC/CNF) were hybridized with natural graphite (NG) as a means of improving the anodic performance of Li-ion batteries. Samples were made with hybridization levels of 10–30 wt% of NG exhibited excellent cyclability with a discharge capacity of 389–522 mAh g−1 in a Li-ion battery system. SiO/PyC/CNF composite hybrids showed better cyclability than other carbon composites containing SiO/PyC and SiO/CNF. These hybridization effects were attributed to the lower contact resistance of SiO/PyC/CNF in the electrode. The internal spaces created throughout the SiO/PyC/CNF composite and their effect on material dispersion in the hybridized electrodes may have prevented electrode damage by relieving tensions induced by the expansion of SiO particles in the electrode over the course of repeated charge and discharge processes. [ABSTRACT FROM AUTHOR]

Abstract: The large irreversible capacity of hard carbon limits its widespread commercialization for Li-ion batteries. To reduce the initial irreversible capacity of hard carbon, we investigated the effect of carbonization treatment of the precursor under vacuum on the irreversible capacity of resultant hard carbon. Compared with the sample carbonized under Ar atmosphere, the sample carbonized under vacuum obtained a lower irreversible capacity of 58mAhg−1, due to the formation of pyrolytic carbon film on the surface, and the reduction of BET surface area, amount of heteroatoms and hydroxyl groups. [Copyright &y& Elsevier]

Anodic hard carbon for lithium-ion batteries with high discharge capacity was successfully developed using mangrove green tree as a cheap raw material. To obtain commercial-level first-cycle Coulombic efficiency, the effects of heat pre-treatment in the low temperature range of 450–600 °C at various pressures, to produce optimized char precursor before carbonization, were closely investigated, focusing on synthetic yield, structural and physical properties, first-cycle Coulombic efficiency, and discharge capacity of the resulting hard carbon. The hard carbon with heat pre-treatment involving optimum fabrication conditions of 500 °C in inner gas at 0.7 MPa for 39 days exhibited higher synthetic yield of 30.0 wt% and better first-cycle Coulombic efficiency of 81% and discharge capacity of 424 mAh/g than that prepared through direct one-step carbonization, due to low H/C and O diff /C ratios and a pore structure promoting lithium-ion insertion/desertion. [ABSTRACT FROM AUTHOR]

Carbon-fluorine (C m F n ) groups were selectively introduced on the surface of natural and synthetic graphites through plasma-fluorination using C 4 F 8 vacuum plasma treatment. The type of carbon-fluorine bondings on the plasma-fluorinated graphite surface were selectively controlled by adjusting plasma processing time from 10 to 20 min. Systematic surface analyses revealed that the fluorine amount on the surface of plasma-fluorinated graphite was determined by the type of intrinsic structure and degree of graphitization of graphite. The electronegative semi-ionic carbon-fluorine groups on the graphite surface reduced the resistance related to lithium ion migration and charge transfer, leading to highest discharge capacity of 387 mA h/g at 1st cycle and discharge capacity of 293 mA h/g at high 10 C rate without deteriorating the 1st cycle Coulombic efficiency. This novel vacuum plasma treatment of introducing highly electronegative C m F n species on graphite can illuminate a new route of preparing superior lithium ion battery anode. [ABSTRACT FROM AUTHOR]

Effects of compositions and softening points of coal tar pitches (CTPs) on the electrochemical performances especially for first cycle Coulombic efficiency and rate performance, of the amorphous carbon coating on the graphite surface were closely examined. CTPs with higher softening points could afford the better homogeneous amorphous carbon coating on the graphite surface, resulting in the better enhancing rate performance of graphite anode without decreasing the first cycle Coulombic efficiency. CTP with almost complete absence of hexane soluble (HS) fraction always showed the good enhancing effect of the rate performance. HS fraction of CTP, which is a reason for inducing surface defects on the coated carbon, hindered the enhancing effect of electrochemical performances. CTP derived amorphous carbon coating could effectively decrease charge transfer resistance on the graphite electrode–electrolyte interface. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) have unique structural characteristics, such as a nanometer diameter, a fibrous structure, and high crystallinity, and thus, are expected to be promising important materials for energy and environment applications. However, difficulties in handling and the high production costs of CNFs often hamper the industrialization of products from CNF alone. On the other hand, hybridization of CNF with other materials can improve their weaknesses, increase performance, and/or give them new abilities. In this paper, we introduce the effectiveness of CNFs as complementary functional materials especially for applications in the energy and environment fields, such as Li-ion secondary batteries, fuel cells, electric double-layer capacitors, and air purification. [TANSO 2013 (No. 260) 313–9.] [ABSTRACT FROM AUTHOR]

Abstract: Mesophase pitch-derived synthetic graphite was hybridized with natural graphite/carbon nanofiber (NG/CNF) composites prepared by mechanical mixing, carbonization, and graphitization processes. Addition of the NG/CNF composites introduced effective internal pores inside the synthetic graphite matrix, thereby improving the rate performance, 1st cycle coulombic efficiency, and cyclability. Hybridized graphite with 10wt% of added NG/CNF composite exhibited the best rate performance, with a discharge capacity retention rate of over 90% after a 5C discharge test. [Copyright &y& Elsevier]

Abstract: Solid electrolyte interphase (SEI) formation behavior was carefully tracked on the well-defined edge and basal surfaces of carbon nanofibers. The effects of boron doping on SEI formation were also examined. Platelet carbon nanofibers (PCNFs) successfully afforded well-defined edge and basal surfaces. Surface morphology and chemistry were controlled by graphitization, nitric acid treatment and boron doping. The surface morphologies of various well-defined PCNFs were observed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The SEI of PCNF with edge surfaces was more abundant and four times thicker than those of PCNF-G and PCNF-B-G with basal surfaces. The SEI of PCNF-G-NA without boron doping was much more abundant and three times thicker than that of PCNF-B-G-NA with boron doping. [Copyright &y& Elsevier]

Abstract: In this study, the microstructure of mangrove-charcoal-derived carbon (MC) was studied using XRD, STM and TEM. MC was found to consist of aligned quasi-spherical structural units with diameters of around 5–20nm. It shows typical hard carbon characteristics, including a strongly disoriented single graphene layer and BSU, formed by two or three graphene layers stacked nearly parallel. Some curved and faceted graphene layers, especially closed carbon nanoparticles with fullerene-like, were observed in the as-prepared samples. MC was also evaluated as an anodic material for Li-ion batteries. MC carbonized at 1000°C possessed the highest available discharge capacity (below 0.5V) of 335mAhg−1, the high first-cycle coulombic efficiency of 73.7%, good rate and cyclic capability and PC-based electrolyte compatibility. 7Li nuclear magnetic resonance (NMR) spectra of fully lithiated mangrove charcoal-derived carbons indicated the co-existence of three Li species. [Copyright &y& Elsevier]

Abstract: The suggested pyrolytic carbon (PC) coated Si-carbon nanofiber (CNF) composites can be a solution to provide higher discharge capacity and cycle-ability facilitating the 1st cycle coulombic efficiency of cheap metallic Si particles as an appropriate anodic material for Li-ion battery. The CNFs on the surface of Si particle can provide flexible space to relieve volumetric expansion during charge. Well-controlled PC coating on the surface of Si particle can improve the coherence of CNFs on the Si particle, thereby to enhance the role of CNF as all the more effective electrode material. The additional PC coating on the Si–CNF composite can accomplish the lower surface area and afford the improvement of the 1st cycle coulombic efficiency. Ingenious combinations of PC coating and CNF compositeness successfully made the novel type Si–CNF composite to achieve a remarkable discharge capacity (1115mAhg−1), an excellent cycle-ability (77% retention rate after 20th cycle), and a good 1st cycle coulombic efficiency (79%) for the effective application as an anode material. [Copyright &y& Elsevier]