N-doped and expanded graphene oxides as Li-S cathodes prepared from polyallylamine hydrochloride

김백환,김석 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

In this study, we used polyallylamine (PAA) for doping source and spacer. PAA-Graphene oxide (GO) composite was synthesized with hydrothermal method. For preparing composites, we used oxygen containing groups of GO and amine groups of PAA. There are two mechanisms for synthesizing PAA-GO composite; epoxide opening reaction and amidations. Then, PAA-GO composite was annealed to pyrolysis temperature of the PAA. After annealing, sulfur was loaded and PAA-GO-Sulfur (PGS) cathode was prepared. We confirmed variable C-N bonds with Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) was used for analyzing presence of Elemental sulfur (S8) loaded and d-spacing of PGS cathode. Electrochemical properties were examined by cyclic voltammetry (CV) and discharge/charge performances. Initial discharge capacity of PGS cathode was higher than that of graphene oxide annealed at same temperature.

제조물책임법 실행에 따른 국제품질경영시스템과 한국산업규격 및 제품안전 경영의 통합시스템 구축에 관한 연구

김백환,유왕진 한국경영공학회 2003 한국경영공학회지 Vol.8 No.1

The rapid introduction of product liability has recently been a prevalent phenomenon, as global changes arising from rapid development in science and the economy have resulted in a highly interconnected world economy. This study was established, based on current literature and business consulting cases in the position of companies, and is one of the operating subjects in a system for legal responsibility in manufactured products. The characteristics of the integrated system in this thesis are as follows: 1. It is an integrated model of systems required by different organizations, different from an integrated system required by the same organization. 2. The initial integrated system designed in this thesis integrated the different system types from the existing ones in terms of a controlled process. In other words, KS is a nation formulated and a nation led certification, which is conducted as a compulsory system. While ISO 9001:2000 is an international organization established and private organization-led certification. It is optional. PSM, which is not a certification concept, but which still requires a self-operation system, is neither compulsory nor part of the national legal system. 3. The standards and laws that initially presented 3 integrated systems are similar in that they are required by many domestic firms for their management of the business. In this study, a method to design a reasonable and integrated model that could enhance

Electrochemical and structural properties of lithium battery anode materials by using a molecular weight controlled pitch derived from petroleum residue

김백환,김지홍,김종구,배민정,임지선,이철위,김석 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.41 No.-

The petroleum pitch derived from pyrolyzed fuel oil (PFO) was prepared and modified using the solventextraction method to study the effect of the pitch fraction on electrochemical and structural behaviors. The modified pitches were Hexane-insoluble, Toluene-insoluble and NMP-insoluble pitches. To confirmthe structural characteristic parameters such as (La, d002, IG/ID and true density), X-ray diffraction, Ramanspectroscopy and true density measurements were conducted. Electrochemical properties weremeasured using the coin cell test. Based on the electrochemical properties and structural analyses, theschematic design of the micro-carbon domain was proposed, and the role of each fraction (hexanesoluble,hexane-soluble and toluene-insoluble, Toluene-insoluble and NMPI-insoluble and NMPIfractions) was studied. Each fraction affected the coke during carbonization, and the hexane-solublefraction and hexane-soluble and toluene-insoluble fraction affected the initial efficiency and Li+[2TD$DIF] iondiffusion resistance.

Studies on the preparation and carbonization behavior of molecular weight controlled petroleum pitch carbons

김백환,김석 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

The petroleum pitch is one of the precursor of softcarbon as an anode material. The pitch has compelx material because of its various aromatic hydrocarbons and controlling molecular weight of this pitch could be a solution for improving anode properties. The pitch was prepared from pyrolysed fuel oil in a 400-ml reactor under N2 flow at a rate of 100ml/min. The molecular-weight of the pitch could be controlled by solvent extraction method. Solvent extraction was performed by hexane, toluene, tetrahydrofuran, and N-methyl-2-pyrollidone. Thermal analysis was conducted for the carbonization behavior of each samples. The crystallinity was confirmed by the X-ray diffraction (XRD). In conclusion, the molecular weight-controlled pitches showed different condensation behavior and different crystallinity.

Effect of process-control factors on electrochemical properties of pitch-based carbons

김백환,임지선,이철위,김석 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0

Petroleum pitch-coke was manufactured after carbonization with petroleum residue based pitch as a precursor, prepared by different process. We controlled the heat treatment temperature and holding time at target temperature. Considering the yield, the carbonization temperature was set to 900℃. To verify the crystalline lattice parameter of different samples, X-ray diffraction (XRD) was used and calculated lattice parameter by scherrer equation. The Lattice parameter Lc (stacking height) calculated by the equation was proportional to processing time and heating temperature. Electrochemical properties were measured by constant current (CC) / constant voltage (CV) charge / discharge for practical approach. The initial efficiency was somewhat increased in limited range and the initial discharge capacity was decreased in accordance with higher heating temperature of each samples. Consequently, the pitch-coke which made at high temperature and have long holding time showed better reversibility and structure for cycling.

Controlling the electrochemical properties of an anode prepared from pitch-based soft carbon for Li-ion batteries

김백환,김지홍,김종구,임지선,이철위,김석 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.45 No.-

A petroleum residue-based carbon electrode for use in a lithium-ion battery was prepared through thethermal reaction of pyrolyzed fuel oil. The samples were characterized by their softening point,crystallinity and battery performance. The softening point and pitch crystallinity increased with higherreaction temperatures and longer reaction times. The prepared pitch-based carbon had a 300–350 mAh/g capacity and 71–78% initial efficiency. Notably, the high-softening-point pitch resulted in thedeveloped crystallinity through polymerization and condensation. In conclusion, the high-softeningpointpitch had a better initial efficiency and rate capability based on its high crystallinity.

Enhancement of electrochemical properties of petroleum pitch having a low softening point using solvent extraction methods

김백환,김석 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

The petroleum pitch having a low softening point (141℃) prepared and carbonized for anode materials. The feed was pyrolysed fuel oil and reacted in a 5-L reactor at a ramping rate of 3℃/min, under N2 flow. To confirm the composition of the prepared pitch, solvent fractionation method was conducted, and the contents of the Hexane soluble (HS) fraction was 39%. After solvent fractionation, HS-fraction was eliminated from the pitch and residue pitch was also carbonized. X-ray diffraction (XRD) was used and calculated lattice parameter by scherrer equation. Electrochemical properties were measured using CR2032-type coin cells, and all samples were charged with constant current /constant voltage charge. The initial efficiency and rate capability of the prepared coke was low, but the coke prepared from HS-free pitch showed increased electrochemical properties. Consequently, the HS-fraction of the pitch having low softening point could increase the carbon defect during the carbonization.

Electrochemical properties of the modified petroleum pitch composites by using natural graphite

김백환,김석 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

The petroleum pitch having softening point of 178℃ was prepared for precursor of the coke material. Where, using the solvent extraction method, the pitches insoluble in hexane (HI) and toluene (TI) were prepared. Then the HI and TI were dissolved in THF solvent and the natural graphite powder was added to the prepared solution. After vigorous stirring, the THF solvent completely vaporized and the modified pitch-coated natural graphite (MPNGs) was prepared. The crystallinity of the MPNG were confirmed by X-ray diffraction (XRD). Raman spectroscopy was conducted for identifying the defect of the MPNGs. The electrochemical properties of the MPNGs were tested using CR2032-type coin cells, and all samples were charged with constant current (CC)/constant voltage (CV) charge. The rate capability test of the MPNGs were conducted at 0.1C~20 C, where 1C rate is 360 mAh/g. The prepared MPNGs showed excellent performance in the rate capability.

Oxygen content effect on electrochemical behaviors of graphene oxide-sulfur cathodes

김백환,김석 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

In this study, we heated Graphene oxide(GO) using furnace at different temperature to control the ratio of oxygen containing groups(OCGs) of GO and compared electrochemical performances each modified GO-S sample. It is known that Oxygen containing groups of Graphene oxide show strong binding with polysulfides generated during cycling and can improve the sulfur loading ratio of the modified GO. OCGs ratio could be controlled with thermal treatment and confirmed with FTIR and d-spacing of XRD. We confirmed reduction properties of GO-S composite with cyclic voltammograms(CVs) and Specific Capacity of GO-S cathode measured by 0.2C rate. Cycling performances suggest that the thermal treated GO-S cathode showed better electrochemical performances than normal GO-S samples.

Surface modification of nanoporous carbon electrodes by a pitch coating for rechargeable lithium-sulfur batteries

김백환,김석 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

Graphene is one of the promising materials in lithium-sulfur batteries as cathode material, but is somewhat limited to confine sulfur owing to its 2D-structure. The pitch distilled from petroleum is one of the most-used carbon material in lithium ion batteries for modifying graphite anode and attributes to improve capacity. In this experiment, we prepared cathode material by coating graphene oxide with pitch and conducted thermal treatment. This coating process could reduce capacity loss for dissolution of polysulfide into electrolyte. For comparison, we used only graphene oxide as cathode and others were same. Electrochemical properties were characterized by cyclic voltammetry in 1M LiTFSI electrolyte.