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A solid electrolyte interphase (SEI) on an anode is a critical issue in lithium-ion batteries because it is related to cycling stability. In this study, we introduce a semi-ionic C F bond on the surface of graphite (SICF) via plasma fluorination to introduce a LiF-based SEI layer on the anode during the first cycle. In the charge-discharge profiles and cyclic voltammetry curves, a peak related to the LiF-based SEI formation was clearly observed for SICF. In particular, SICF had an excellent long-term cycling stability of 98.8% for 100 cycles (1.0 C-rate). From the anodes of the disassembled coin cells, it was found that semi-ionic C F bonds improved the formation of a stable LiF-based SEI layer and decreased the number of side reactions with HF, which was produced from PF5. Moreover, SICF exhibited a lower volume expansion compared to that of the pristine anode and the anode with covalent C F bonds. Therefore, introducing a semi-ionic C F bond via plasma fluorination is a key strategy for forming a LiF-based SEI layer on the graphite anode surface that enhances the cycling stability of lithium-ion batteries.

The present study aimed to identify the required characteristics of binder pitches in the filler-binder mixing process to effectively manufacture graphite blocks. To this end, a binder pitch was separated into pitch fractions of varying molecular-weight segments. The role and effectiveness of each pitch fraction were then analyzed with respect to their molecular-weight distribution. As a result, the optimal molecular-weight distribution was determined. More specifically, a coal-tar pitch was separated into solvent-soluble and solvent-insoluble fractions. The molecular-weight distribution was determined according to this classification, and the characteristics of each pitch fraction were examined. The pitch separation process was conducted using three solvents: hexane, toluene, and quinoline. The resulting pitch was separated into the following pitch fractions: hexane-soluble (HS), hexane-insoluble-toluene-soluble (HI-TS), toluene-insoluble-quinoline-soluble (TI-QS), and quinoline-insoluble (QI). Fourier transform infrared (FT-IR) spectrum, matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), and softening point of each pitch fraction were measured. Also, pitch samples were refabricated while varying the mixing ratio of these pitch fractions, and carbon blocks were then prepared using them. The compressive strength and porosity of these blocks were measured and compared. The P154_B pitch with a high content of TI-QS was used to fabricate a green block. Due to the high viscosity of the binder used, the fluidity was not sufficiently high, and thus, the green block made of this pitch had relatively low strength. The other blocks had similar levels of strength. After the carbonization process, the carbon block with a high content of HS (P352_B-C) and the carbon block with the HS content removed (P073_B-C) showed lower compressive strength than their respective green-block counterparts (P352_B and P073_B). However, their strength was higher compared to those of the other carbon blocks. In the case of carbon block P073_B-C, the HS content was completely removed, and thus, the content of TI-QS (β-resin) was relatively high. Accordingly, this carbon block ended up with large amounts of components that had high coking values (CVs), and this contributed to limiting the formation of pores. Therefore, the compressive strength of this carbon block was high. In the case of the carbon block with a high content of HS (P352_B-C), a suitable level of viscosity was achieved because the HS components ensured high fluidity. As a result, blocks with higher density and compressive strength could be fabricated. The major findings of the present study confirm that producing carbon blocks with high mechanical properties requires binder pitches with a balanced combination of suitable viscosity to ensure sufficiently high fluidity and a proper level of CV to effectively suppress the formation of pores in the mixing and molding process.

In the present study, pyrolyzed fuel oil (PFO)-based pitch without impurities was used to prepare coke under pressure, and the preparation yield and the powder resistance depending on the graphitization were investigated. The preparation yield of green coke by pressurized coking at 500 °C was about 26–27% higher than that at normal pressure. However, the coke yield after the thermal treatment of green coke at 900 °C was lower by 10.6–14.8% at the pressurization conditions than under normal pressure. This may be because the substances that are not vaporized under the pressurized conditions remain in the reactants and then are discharged later. The coke yield after the thermal treatment at 900 °C was higher by 14.9–28.3% under the pressurized conditions than under the normal pressure, indicating that the low-boiling point materials of the pitch participated more in coke polymerization under the pressurized conditions. The density of the coke prepared under the pressurized conditions was lower than that of the coke prepared under normal pressure, because the low-boiling point materials of the pitch participated in the reaction. However, after graphitization, the density values became similar (2.27–2.26 g/cm3). The volume resistivity of the graphitized samples was in a range of 0.499 × 10–2–0.384 × 10–2 Ω cm, indicating that the coke samples have similar electrical properties. The results of the present study show that, in comparison with the conventional normal-pressure process, the pressurized coking process can improve the yield through the participation of low-boiling point materials in the polymerization reaction, while maintaining the properties of the prepared coke and graphite, such as the conductivity and density.

Fly ash consists of various metal oxides which can remove SO2 gas by the catalyst effect. When fly ash is added in the preparation process of pitch-based activated carbon, the pitch particles aggregate and fly ash is embedded in the activated carbon. To increase SO2 gas removal performance, activated carbon was prepared by surface-treated fly ash and petroleum-based pitch. Carboxyl groups were introduced into the fly ash by malic acid treatment. The introduced carboxyl groups acted as an activation agent to create micropore around the fly ash, and created micropores were exposed to the fly ash outside of the activated carbon. The exposed fly ash increased removal amount of SO2 gas by a catalytic effect of the metal oxides. The SO2 gas removal performance improved by 34% because of the catalyst effect of the exposed fly ash and improvement in the micropore structure in the activated carbon.

In this study, pitch crosslinked by oxygen function groups was made into activated carbon (AC) and pore structure was observed. The oxygen functional groups were introduced by the addition of waste PET for pitch synthesis. Activation agent ratios used to obtain the AC during the activation process were 1:1, 1:2 and 1:4 (pitch:KOH, w/w). The oxygen content in the prepared pitch was characterized by elemental analysis. Also, the molecular weight of pitch was investigated by MALDI-TOF. Specific surface area and micropore volume of the prepared AC were determined by the argon adsorption–desorption analysis and calculated using the Brunauer–Emmett–Teller and Horvath–Kawazoe equations, respectively. Micropore fraction of PET-free AC was smaller than that of PET-added AC. At high activation agent ratio, mesopores were created when the micropore structure collapsed. However, in the PET-added AC, due to the oxygen crosslinking effect, the micropore structure and micropore size were maintained even at a high activation agent ratio. Therefore, PET AC was found to have a higher micropore fraction than that of PET-free AC.

Hard carbon is difficult to prepare as high-crystallinity synthetic graphite even with graphitization (over 2400 °C), so only soft carbon has been used as a raw material for the preparation of synthetic graphite. Therefore, the selection of raw materials for synthetic graphite preparation is limited. In this study, synthetic graphite was prepared from hard carbon-based carbon black (HCCB) to overcome the issue of the limited selection of synthetic graphite raw materials. Synthetic graphite was prepared by a 3-step heat treatment from a mixture of HCCB and Si. SiC was synthesized from HCCB by a first heat treatment, and unreacted HCCB was removed through a second heat treatment. In a third heat treatment, synthetic graphite was prepared by removing Si from SiC. The prepared synthetic graphite had a high-crystallinity and few defects, and the powder electrical conductivity was approximately 22.7 times higher than that of graphitized HCCB. The introduced new method is expected to induce diversification of raw materials for the preparation of synthetic graphite, thereby solving the problems of the traditional preparation method.

The present study was conducted to investigate changes in the thermal conductivity of petroleum pitch-based carbon molded bodies prepared by anisotropic (uniaxial) molding under different molding pressures. The carbon molded bodies were prepared using needle coke and petroleum-based binder pitch polymers (softening point: 150 ℃). Green blocks prepared under high molding pressure showed a higher particle orientation value up to 16.4 &mu, m. Graphite blocks, prepared by graphitizing the green blocks at 2800 ℃ showed a similar trend. The pores in the carbon molded body were filled with low boiling point substances, generated by the thermal treatment of the binder pitch polymer or air that could not be discharged during the molding procedure. Therefore, when phonons encountered a pore, phonon scattering, rather than phonon transport, occurred, and thus the heat transport from the hot zone to a cold zone became slow. As a result, although the particle orientation was a little higher in the B_10-G sample than in the B_20-G sample (in the error range), the thermal conductivity was higher in the B_20-G sample, which may be because the B_10-G sample had a higher porosity than the B_20-G sample.

The effect of oxidation on carbonization and physical activation of pitch was determined for synthesis of activated carbon (AC). The prepared AC from non-oxidized pitch exhibited a low specific surface area of 0.2 m2/g. On the other hand, the specific surface area of prepared AC from the oxidized pitch increased up to 729.6 m2/g even by same activation process. The introduced oxygen functional groups were almost removed during carbonization (with only 3.1% or less oxygen remaining); therefore, they did not directly affect the activation process. However, introduced oxygen functional groups prevented the rearrangement of the pitch molecules during carbonization. This effect decreased the crystallinity of the carbonized pitch and increased the number of defects present. The defects acted as active sites and improved the pore structure; thus, AC with a high specific surface area was prepared.

This study aims to examine absorption characteristics of toluene, isopropyl alcohol (IPA), ethyl acetate (EA), and ternary-compounds, all of which are widely used in industrial processes, by means of four types of commercial acti- vated carbon substances. It turned out that among the three types of volatile organic compounds, the breakthrough point of activated carbon and that of IPA, whose affinity was the lowest, were the lowest, and then that of EA and that of tol- uene in the order. With the breakthrough point of IPA, which was the shortest, as the standard, changes in the break- through points of unary-compounds, binary-compounds, and ternary-compounds were examined. As a result, it turned out that the larger the number of elements, the lower the breakthrough point. This resulted from competitive adsorption, that is, substitution of substances with a low level of affinity with those with a high level of affinity. Hence, the adsorp- tion of toluene-IPA-EA and ternary-compounds require a design of the activated carbon bed based on the breakthrough of IPA, and in the design of activated carbon beds in actual industries as well, a substance whose level of affinity is the lowest needs to be the standard.

The graphite block as a phase change materials (PCMs) was manufactured by graphitization of a carbon block. Carbon blocks were prepared by filler (cokes or graphite) and binder (pitch). The binder-coated filler was thermally treated for carbonization. The gases generated from the evaporation of low molecular weight components in the binder pitch during the carbonization process were not released to the outside. Consequently, porosity and volume expansion were increased in artificial graphite, and thereby the thermal conductivity decreased. In this study, to prevent the decrease of thermal conductivity in the artificial graphite due to the disadvantages of binder pitch, the carbon block was prepared by the addition of carbon black, which can absorb low molecular weight compounds and release the generated gas. The properties of the prepared carbon blocks were analyzed by SEM, TGA, and thermal conductivity. The addition of carbon black (CB) decreased the porosity and volume expansion of the carbon blocks by 38.3% and 65.9%, respectively, and increased the thermal conductivity by 57.1%. The CB absorbed the low molecular weight compounds of binder pitch and induced the release of generated gases during the carbonization process to decrease porosity, and the thermal conductivity of the carbon block increased.