• Bulletin of the Korean Chemical Society
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• 제21권11호
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• pp.1125-1132
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• 2000

The pH effect of the precursor solution on the preparation of $LiCoO_2$ by a solution phase reaction containing malonic acid was carried out. Layered $LiCoO_2$ powders were obtained with the precursors prepared at the different pHs (4, 7, and 9) and heat-treated at $700^{\circ}C(LiCoO_2-700)$ or $850^{\circ}C(LiCoO_2-850)$ in air. pHs of the media for precursor synthesis affects the charge/discharge and electrochemical properties of the $LiCoO_2electrodes.$ Upon irrespective of pH of the precursor media, X-ray diffraction spectra recorded for $LiCoO_2-850$ powder showed higher peak intensity ratio of I(003)/I(104) than that of $LiCoO_2-700$, since the better crystallization of the former crystallized better. However, $LiCoO_2$ synthesized at pH 4 displayed an abnormal higher intensity ratio of I(003)/I(104) than those synthesized at pH 7 and 9. The surface morphology of the $LiCoO_2-850$ powders was rougher and more irregular than that of $LiCoO_2-700$ made from the precursor synthesized at pH 7 and 9. The $LiCoO_2electrodes$ prepared with the precursors synthesized at pH 7 and 9 showed a better electrochemical and charge/discharge characteristics. From the AC impedance spectroscopic experiments for the electrode made from the precursor prepared in pH 7, the chemical diffusivity of Li ions (DLi+) in $Li0.58CoO_2determined$ was 2.7 ${\times}$10-8 $cm^2s-1$. A cell composed of the $LiCoO_2-700$ cathode prepared in pH 7 with Lithium metal anode reveals an initial discharge specific capacity of 119.8 mAhg-1 at a current density of 10.0 mAg-1 between 3.5 V and 4.3 V. The full-cell composed with $LiCoO_2-700$ cathode prepared in pH 7 and the Mesocarbon Pitch-based Carbon Fiber (MPCF) anode separated by a Cellgard 2400 membrane showed a good cycleability. In addition, it was operated over 100 charge/discharge cycles and displayed an average reversible capacity of nearly 130 mAhg-1.

• 전기화학회지
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• 제27권3호
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• pp.88-96
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• 2024

리튬금속(Li metal)은 높은 비용량과 에너지 밀도, 낮은 표준 전극 전위로 인해 유망한 음극활 물질로 각광받아온 재료이지만, 충·방전 시 발생하는 수지상 결정인 덴드라이트(dendrite)로 인해 안전성 및 수명안정성에 한계가 있었다. 본 연구에서는 나노 파이버(Nano Fiber) 형태의 도전재인 vapor grown carbon fiber (VGCF)와 은(Ag)의 복합체가 코팅된 분리막을 개발하였으며, 해당 분리막이 리튬금속 음극의 전기화학 특성에 미치는 영향을 연구하였다. VGCF와 Ag의 시너지 효과를 확인하기 위하여 표면 처리되지 않은 분리막, VGCF만 단면 코팅 처리된 분리막을 각각 준비하여 Ag-VGCF 분리막과 비교 평가하였다. Bare 분리막의 경우, 초기 충·방전 과정에서 리튬금속 표면이 덴드라이트로 뒤덮인 반면, VGCF 분리막 및 Ag-VGCF 분리막 모두 분리막 표면에 코팅된 전도성 코팅층 내부에 리튬이 석출되는 거동을 보였다. 또한 Ag-VGCF 분리막은 VGCF 분리막 대비 더욱 균일한 형상의 석출 형태를 보였다. 그 결과 Ag-VGCF 분리막은 Bare 분리막 및 VGCF 분리막 대비 향상된 전기화학적 특성을 보였다.

• 한국세라믹학회지
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• 제47권6호
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• pp.638-642
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• 2010

The spinel material $Li_4Ti_5O_{12}$ has attracted considerable attention as an anode electrode material for many battery applications owing to its light weight and high energy density. However, the real capacity of $Li_4Ti_5O_{12}$ powder as determined by the solid-state method is lower than the ideal capacity. In this study, we investigated the effect of the dopants in M-doped spinel $Ba_xLi_{4-2x}Ti_5O_{12}$(x=0.005, 0.05, 0.1) powders prepared by the solid-state reaction method and used as the anode material in lithiumion batteries. The results confirmed the effect of the Ba and Sr dopants on the powder properties of the spinel $Li_4Ti_5O_{12}$, which exhibited a pure spinel structure without any secondary phase in its XRD pattern. Moreover, the electrochemical properties of the spinel M-LTO materials were investigated using a half cell. The electrochemical data show that cells with anodes made of undoped $Li_4Ti_5O_{12}$ and Ba- and Sr-doped $Li_4Ti_5O_{12}$ have discharge capacities of 97, 130, and 112 mAh/g, respectively, at the first cycle. Moreover, the Ba- and Sr-doped spinel $Li_4Ti_5O_{12}$ demonstrated good properties in the mid-voltage range at 1.55 V, showing stable cyclic voltammogram properties which surpassed those of the same material without Ba or Sr at 1 C after 100 cycles.

• Journal of Electrochemical Science and Technology
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• 제1권1호
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• pp.39-44
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• 2010

1.5 V and 3.0 V-class film-type primary batteries were designed for radio frequency identification (RFID) tag. Efficient fabrication processes such as screen-printings of conducting layer ($25{\mu}m$), active material layer ($40{\mu}m$ for anode and $80{\mu}m$ for cathode), and electrolyte/separator/electrolyte layer ($100{\mu}m$), were adopted to give better performances of the 1.5 V-class film-type Leclanch$\acute{e}$ primary battery for battery-assisted passive (BAP) RFID tag. Lithium (Li) metal is used as an anode material in a 3.0 V-class film-type $MnO_2||$Li primary battery to increase the operating voltage and discharge capacity for application to active sensor tags of a radio frequency identification system. The fabricated 3.0 V-class film-type Li primary battery passes several safety tests and achieves a discharge capacity of more than 9 mAh $cm^{-2}$.

• 한국세라믹학회지
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• 제49권6호
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• pp.659-662
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• 2012

Yttrium (Y) and niobium (Nb) doped spherical $Li_4Ti_5O_{12}$ were synthesized to improve the energy density and electrochemical properties of anode material. The synthesized crystal was $Li_4Ti_5O_{12}$, the particle size was less than $1{\mu}m$ and the morphology was spherical and well dispersed. The Y and Nb optimal doping amounts were 1 mol% and 0.5 mol%, respectively. The initial capacity of the dopant discharge and charge capacity were respectively 149mAh/g and 143 mAh/g and were significantly improved compared to the undoped condition at 129 mAh/g. Also, the capacity retention of 0.2 C/5 C was 74% for each was improved to 94% and 89%. It was consequently found that Y and Nb doping into the $Li_4Ti_5O_{12}$ matrix reduces the polarization and resistance of the solid electrolyte interface (SEI) layer during the electrochemical reaction.

• 공업화학
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• 제32권6호
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• pp.607-612
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• 2021

실리콘(Si) 활물질은 낮은 전위와 높은 에너지 밀도를 가지고 있어 현재 활용되고 있는 흑연을 대체할 수 있는 소재로 기대되고 있다. 그러나 반복적인 충, 방전 과정 중 부피 팽창으로 인한 실리콘 입자의 붕괴와 지속적인 전해질 분해 반응이 문제점으로 지적되고 있다. 이와 같은 문제를 해결하기 위해 본 연구에서는 실리콘 음극에 대한 효과적인 바인더로서 가교 결합이 가능한 Castor oil 기반의 수분산 폴리우레탄을 제조하였으며(CWPU), 이를 다량의 Oxirane 작용기를 가진 Tris(2,3-epoxypropyl) isocyanurate (TGIC)와 결합시켜 기계적으로 안정한 3차원 네트워크 구조를 형성하였다. CWPU-TGIC 바인더로 제조된 실리콘 음극은 안정적인 장기 수명 특성뿐만 아니라 우수한 방전 용량을 나타내었다. 이러한 결과는 CWPU-TGIC 바인더가 장기간 반복되는 충, 방전 과정 동안 실리콘 음극의 큰 부피 변화를 효과적으로 완화하는 것으로 분석되었다. 본 연구 결과는 실리콘 음극의 전기화학적 특성을 향상시키기 위한 효과적인 친환경 바인더의 가능성을 제시한다.

• Corrosion Science and Technology
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• 제20권4호
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• pp.183-188
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• 2021

The increasing demand for energy storage in mobile electronic devices and electric vehicles has emphasized the importance of electrochemical energy storage devices such as Li-ion batteries (LIBs) and supercapacitors. For reversible Li storage, alternative anode materials are actively being developed. In this study, we designed and fabricated an Nb₂O₅-Li₃VO₄ composite for use as an anode material in LIBs and hybrid supercapacitors. Nb₂O₅ powders were dissolved into a solution and the precursors were precipitated onto Li₃VO₄ through a simple, low-temperature hydrothermal reaction. The annealing process yielded an Nb₂O₅-Li₃VO₄ composite that was characterized by X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy. Electrochemical tests revealed that the Nb₂O₅-Li₃VO₄ composite electrode demonstrated increased capacities of approximately 350 and 140 mAh g^-1 at 0.1 and 5 C, respectively, were maintained up to 1000 cycles. The reversible capacity and rate capability of the composite electrode were enhanced compared to those of pure Nb₂O₅-based electrodes. These results can be attributed to the microstructure design of the synthesized composite material.

• 한국결정성장학회지
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• 제8권3호
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• pp.435-441
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• 1998

리튬 이온전지의 양극으로 사용되는 Li-SGICs를 혼합가압법에 의하여 Li의 함유량에 따라 합성하였다. 이들 합성된 화합물을 X-선 회절법 및 DSC 열 분석법을 이용하여 특성화하였다. X-선 회절 분석결과에 의하며 리튬의 함유량이 증가함에 따라 낮은 stage가 관찰되었으나, 각각의 화합물들은 혼재된 stage를 가지고 있음이 나타났다. Li30wt%-SGIC의 경우 지배적으로 1stage의 구조가 나타났지만 순수한 1stage의 화합물은 얻을 수가 없었고, 이는 인조 흑연의 구조적 특성 때문으로 예상할 수 있다. DSC에 의한 열역학적 결과로부터 화합물에 대한 엔탈피의 변화량($\Delta$H)과 엔트로피의 변화량($\Delta$S)을 구하였다. 이들로부터 Li-SGIC의 발열반응과 흡열반응의 결과들은 인조 흑연사이에 존재하던 리튬이 열에 의하여 deintercalation이 일어날 때의 열적 안정성과 관련이 있음을 알 수 있었다. 또한 열적 변이가 일어나는 동안 Li30wt%-SGIC의 구조변화에 대하여 토론하였다.

• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.650-654
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• 2006

[ $LiNi_{0.4}Mn_{0.3}Co_{0.3}O_2$ ] cathode material was synthesized by a mixed hydroxide method. Structural characterization was carried out using X-ray diffraction studies. Electrochemical studies were performed by assembling 2032 coin cells with lithium metal as an anode. DSC (Differential scanning calorimetry) data showed that exothermic reactions of $LiNi_{0.4}Mn_{0.3}Co_{0.3}O_2$ charged to 4.3 V versus Li started at high temperatures$(280\sim390^{\circ}C)$. The cell of $LiNi_{0.4}Mn_{0.3}Co_{0.3}O_2$ mixed cathode delivered a discharge capacity of 150 mAh/g at a 0.2 C rate. The capacity of the cell decreased with the current rate and a useful capacity of 134 mAh/g was obtained at a 2 C rate. The reversible capacity after 100th cycles was 126 mAh/g when a cell was cycled at a current rate of 0.5 C in $2.8\sim4.3V$.

• Journal of Electrochemical Science and Technology
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• 제11권4호
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• pp.384-391
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• 2020

Due to its characteristics of light weight, high energy density, good safety, long service life, no memory effect, and environmental friendliness, lithium-ion batteries (LIBs) are widely used in various portable electronic products. The capacity and performance of LIBs largely depend on the performance of electrode materials. Therefore, the development of better positive and negative materials is the focus of current research. The application of metal organic framework materials (MOFs) derivatives in energy storage has attracted much attention and research. Using MOFs as precursors, porous metal oxides and porous carbon materials with controllable structure can be obtained. In this paper, rod-shaped Co-MOF-74 was grown on Ni Foam (NF) by hydrothermal method, and then Co-MOF-74/NF precursor was heat-treated to obtain rodshaped Co₃O₄/NF. Ni Foam was skeleton structured, which effectively relieved. The change of internal stress changes and destroys the structural volume of the electrode material and reduces the capacity attenuation. Co₃O₄/NF composite material has a specific discharge capacity of up to 1858 mA h/g for the first time, and a reversible capacity of up to 902.4 mA h/g at a current density of 200 mA/g, and has excellent rate and impedance performance. The synthesis strategy reported in this article opens the way to design high-performance electrodes for energy storage and electrochemical catalysis.