• Korean Chemical Engineering Research
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• 제56권6호
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• pp.884-889
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• 2018

본 연구에서는 리튬이온커패시터의 음극으로 polyaniline $(PANI)/WO_3$ 전극을 제조하고, 이의 전기화학적 특성을 측정, 분석하였다. $WO_3$ 전극 표면에 PANI를 전기화학적으로 담지 하였을 때 PANI의 용량이 더해져 $WO_3$ 전극보다 충, 방전 용량이 향상되었다. 한편, 충, 방전 시 태양광을 조사하여 충, 방전 용량과 쿨롱 효율(coulombic efficiency)에 빛 조사가 미치는 영향을 파악하였다. $WO_3$ 전극과 $PANI/WO_3$ 전극에 태양광을 조사하였을 때, 두 전극의 충, 방전 용량과 쿨롱 효율은 태양광을 조사하지 않았을 때보다 증가하였다. 이는 $WO_3$가 빛 조사에 의해 광전자를 생성하여 전극의 전기화학적 특성에 영향을 주기 때문으로 해석되며, $PANI/WO_3$의 경우 PANI 또한 빛에 의해 여기 될 수 있어 전극의 특성이 변하게 된다. 빛 조사에 의해 추가로 생성된 광전자가 $Li^+$ 이온의 삽입(intercalation)에 사용되어 용량을 증가시킬 수 있을 뿐 아니라, 전극의 전도성을 높여 쿨롱 효율을 향상 시키는 것으로 여겨진다. $PANI/WO_3$는 충, 방전을 반복하여 진행하게 되면 PANI의 불안정성으로 인해 용량이 점차 감소되게 되지만, 빛 조사 시에는 생성된 광전자와 정공으로 인한 산화-환원 반응에 의해 PANI의 안정성이 크게 향상되어 충, 방전 용량의 감소없이 안정적으로 유지되었다.

• Carbon letters
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• 제26권
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• pp.1-10
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• 2018

Biochar obtained from the thermal conversion of biomass has high potential as a substitute material for activated carbon and other carbon-based materials because it is economical, environmentally friendly, and carbon-neutral. The physicochemical properties of biochar can also be controlled by a range of activation methods such as physical, chemical, and hydrothermal treatments. Activated biochar can be used as a catalyst for the catalytic pyrolysis of a biomass and as an absorbent for the removal of heavy metal ions and atmospheric pollutants. The applications of biochar are also expanding not only as a key component in producing energy storage materials, such as supercapacitors, lithium ion batteries, and fuel cells, but also in carbon capture and storage. This paper reviews the recent progress on the activation of biochar and its diverse present and future applications.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.216-216
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• 2003

The layered nickel oxides (LiNiO$_2$) have been studied for possible use as cathode materials i3l 4V lithium batteries. Although LiCoO$_2$ has been known as the best candidate material for Li-ion batteries, which produces the best performance LiNiO$_2$ is generally accepted as an attractive cathode material, because of its various advantages such as lower cost higher discharge capacity and better reversibility. In this investigation, we calculated the electric state of LiNiO$_2$ using DV-X$\alpha$ molecular orbital method in order to obtain the information of chemical bonding among the Li, Ni and O. In LiNiO$_2$, alternate layers of Li and Ni occupy the octahedral sites of a cubic close packing of oxide ions, making up a rhombohedral structure with an R-3m space group, Li in 3a, Ni in 3b, and O in 6c sites. On the basis of this, we made the cluster model and studied ionization of each atoms and interaction between atoms according to Mullilcen population analysis.

• 한국결정성장학회지
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• 제7권2호
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• pp.244-252
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• 1997

$LiCO_3, Al_2O_3, Fe_2O_3$ 혼합물을 1620K에서 반응시켜 리튬전지의 음극재료로 응용이 가능한 스핀넬형 $LiAl_{2.5}/Fe_{2.5}O_8$를 합성하였다. XRD의 Rietveld 해석을 통하여 결정구조 해석을 하였다. 고용체의 공간군은 $P4_3$32(a=8.1293$\AA$)이고, 결정구조해석의 최종 Residual index는 약 5%정도이었다. 역 스핀넬구조에서 양이온 $Al^{3+}, Fe^{3+}$은 4-배위와 6-배위로 위치하고, $Li^+$은 4b, 12d의 6-배위자리에 존재하였다.

• 한국세라믹학회지
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• 제40권6호
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• pp.513-518
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• 2003

La/sub 2/3-x/Li/sub 3x/□/sub 1/3-2x/TiO₃ compounds with x=0.13 and 0.12 were prepared by slow cooling (x=0.13) and rapid quenching (x=0.12) into the liquid nitrogen after sintering at 1350℃ for 6 h. Their crystal structure has been determined by Rietveld refinement of both the powder neutron and X-ray diffraction data. From neutron diffraction data, we found that the main phase was not tetragonal (P4/mmm), but trigonal (R3cH). The refinement of neutron diffraction for the slow cooled samples were in a good agreement with a new model; a mixture of trigonal (R3cH, 45.7 wt％), tetragonal (p4/mmm, 37.0 wt％), and Li/sub 0.57/Ti/sub 0.86/O₂(pbnm, 17.2 wt%), but the quenched sample was found not to contain tetragonal (p4/mmm). X-ray diffraction data couldn't be well fitted because of the Poor scattering factor of lithium ions and the similar reflection patterns among trigonal (R3cH), tetragonal (p4/mmm), and cubic (Pm3m). We also knew that one transport bottlenecks is destroyed by one La vacancy in the case of trigonal (R3cH).

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1102-1106
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• 2015

A hybrid supercapacitor (HS) is an energy storage device used to enhance the low weight energy density (Wh/kg) of a supercapacitor. On the other hand, a sudden decrease in capacity has been pointed out as a reliability problem after many charge/discharge cycles. The reliability problem of a HS affects the early aging process. In this study, the capacity performance of a HS was observed after charge/discharge. For detailed analysis of the initial charge/discharge cycles, the charge and discharge curve was measured at a low current density. In addition, a solid electrolyte interphase (SEI) layer was confirmed after the charge/discharge. A HC composed of a lithium titanate (LTO) anode and active carbon cathode was used. The charge/discharge efficiency of the first cycle was lower than the late cycles and the charge/discharge rate was also lower. This behavior was induced by SEI layer formation, which consumed Li ions in the LTO lattice. The formation of a SEI layer after the charge/discharge cycles was confirmed using a range of analysis techniques.

• Mass Spectrometry Letters
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• 제1권1호
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• pp.9-12
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• 2010

Trimethylboroxine (TMB) is a six-membered ring compound containing Lewis acidic boron and Lewis basic oxygen atoms that can bind halide anion and alkali metal cation, respectively. We employed Fourier transform ion cyclotron resonance spectroscopy to study the gas-phase binding of $LiBrLi^+$ and $F^-(KF)_2$ to TMB. TMB forms association complexes with both $LiBrLi^+$ and $F^-(KF)_2$ at room temperature, providing direct evidence for the ditopic binding. Interestingly, the $TMB{\cdot}F^-(KF)_2$ anion complex is formed 33 times faster than the $TMB{\cdot}Li^+BrLi$ cation complex. To gain insight into the ditopic binding of an ion pair, we examined the structures and energetics of $TMB{\cdot}Li^+$, $TMB{\cdot}F^-$, $TMB{\cdot}LiF$ (the contact ion pair), and $Li^+{\cdot}TMB{\cdot}F^-$ (the separated ion pair) using Hartree-Fock and density functional theory. Theory suggests that $F^-$ binds more strongly to TMB than $Li^+$ and the contact ion-pair binding ($TMB{\cdot}LiF$) is more stable than the separated ion-pair binding ($Li^+{\cdot}TMB{\cdot}F^-$).

• 분석과학
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• 제13권6호
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• pp.705-711
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• 2000

리튬 이차전지용 부극 재료로 페놀 수지로 부터 유도된 boron을 doping한 polyacene에 구조적 특성, 표면 특성 및 전기적 특성을 연구하였다. Polyacene탄소질에 boron의 함유량을 각각 5%, 10%, 15%, 20% 첨가하여 특성화하였다. X-선 회절 결과에 따르면, 이들 시료들은 대표적인 무정형 탄소의 회절형태를 나타내었다. 표면 상태는 반구형의 표면상태를 가지고 있음을 SEM 결과로부터 알 수 있었다. 전지의 이온과 전자전달효과를 알아보기 위한 전기 화학적 충전/방전 특성과 임피던스 측정의 결과에 의하면, 10%와 15% boron이 첨가된 시료는 다소 우수한 특성을 나타내고 있다.

• Journal of Electrochemical Science and Technology
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• 제5권3호
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• pp.87-93
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• 2014

The fluorine-substituted $0.3Li_2MnO_3{\cdot}0.7Li[Mn_{0.60}Ni_{0.25}Co_{0.15}]O_{2-x}F_x$ cathode materials were synthesized by using the transition metal precursor, $LiOH{\cdot}H_2O$ and LiF. This was to facilitate the movement of lithium ions by forming more compact SEI layer and to reduce the dissolution of transition metals. The $0.3Li_2MnO_3{\cdot}0.7Li[Mn_{0.60}Ni_{0.25}Co_{0.15}]O_{2-x}F_x$ cathode material was sphere-shaped and each secondary particle had $10{\sim}15{\mu}m$ in size. The fluorine-substituted cathodes initially delivered low discharge capacity, but it gradually increased until 50th charge-discharge cycles. These results indicated that fluorine substitution gave positive effects on the structural stabilization and resistance reduction in materials.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.634-637
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• 1999

The amorphous vanadium oxide as a cathode material is very preferable for fabricating high performance micro-battery. The amorphous vanadium oxide cathode is preferred over the crystalline form because three times more lithium ions can be inserted into the amorphous cathode, thus making a battery that has a higher capacity. The electrochemical properties of sputtered films are strongly dependent on the oxygen partial pressure in the sputtering gas. The effect of different oxygen partial pressure on the electrochemical properties of vanadium oxide thin films formed by r.f. reactive sputtering deposition were investigated. The stoichiometry of the as-deposited films were investigated by Auger electro spectroscopy. X-ray diffraction and atomic force microscopy measurements were carried out to investigate structural properties and surface morphology, respectively. For high oxygen partial pressure(>30% ), the films were polycrystalline V$_2$O$_{5}$ while an amorphous vanadium oxide was obtained at the lower oxygen partial pressure(< 15%). Half-cell tests were conducted to investigate the electrochemical properties of the vanadium oxide film cathode. The cell capacity was about 60 $\mu$ Ah/$\textrm{cm}^2$ m after 200 cycle when oxygen partial pressure was 20%. These results suggested that the capacity of the thin film battery based on vanadium oxide cathode was strongly depends on crystallinity.y.