• 전기화학회지
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• 제14권2호
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• pp.117-124
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• 2011

We demonstrate a new surface modification of high-voltage lithium cobalt oxide ($LiCoO_2$) cathode active materials for lithium-ion batteries. This approach is based on exploitation of a polarity-tuned gel polymer electrolyte (GPE) coating. Herein, two contrast polymers having different polarity are chosen: polyimide (PI) synthesized from thermally curing 4-component (pyromellitic dianhydride/biphenyl dianhydride/phenylenediamine/oxydianiline) polyamic acid (as a polar GPE) and ethylene-vinyl acetate copolymer (EVA) containing 12 wt% vinyl acetate repeating unit (as a less polar GPE). The strong affinity of polyamic acid for $LiCoO_2$ allows the resulting PI coating layer to present a highly-continuous surface film of nanometer thickness. On the other hand, the less polar EVA coating layer is poorly deposited onto the $LiCoO_2$, resulting in a locally agglomerated morphology with relatively high thickness. Based on the characterization of GPE coating layers, their structural difference on the electrochemical performance and thermal stability of high-voltage (herein, 4.4 V) $LiCoO_2$ is thoroughly investigated. In comparison to the EVA coating layer, the PI coating layer is effective in preventing the direct exposure of $LiCoO_2$ to liquid electrolyte, which thus plays a viable role in improving the high-voltage cell performance and mitigating the interfacial exothermic reaction between the charged $LiCoO_2$ and liquid electrolytes.

• 한국입자에어로졸학회지
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• 제15권4호
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• pp.127-137
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• 2019

Recently, high electrochemical performance anode materials for lithium ion secondary batteries are of interest. Here, we present silicon-carbon-graphene (Si-C-GR) composites for high performance anode materials of lithium ion secondary battery (LIB). Aerosol process and heat-treatment were employed to prepare the Si-C-GR composites using a colloidal mixture of silicon, glucose, and graphene oxide precursor. The effects of the size of the silicon particles in Si-C-GR composites on the material properties including the morphology and crystal structure were investigated. Silicon particles ranged from 50 nm to 1 ㎛ in average diameter were employed while concentration of silicon, graphene oxide and glucose was fixed in the aerosol precursor. Morphology of as-fabricated Si-C-GR composites was generally the shape of a crumpled paper ball and the Si particles were well wrapped in carbon and graphene. The size range of composites was about from 2.2 to 2.9 ㎛. The composites including silicon particles larger than 200 nm in size exhibited higher performance as LIB anodes such as capacity and coulombic efficiency than silicon particles less than 100 nm, which were about 1500 mAh/g at 100 cycles in capacity and 99% in coulombic efficiency, respectively.

• 한국표면공학회지
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• 제56권1호
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• pp.104-114
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• 2023

Three dimensional (3D) porous structures consisting of Cu@CoO core-shell-type nano-dendrites were synthesized and tested as the anode materials in lithium secondary batteries. For this purpose, first, the 3D porous films comprising Cu@Co core-shell-type nano-dendrites with various thicknesses were fabricated through the electrochemical co-deposition of Cu and Co. Then the Co shells were selectively anodized to form Co hydroxides, which was finally dehydrated to get Cu@CoO nanodendrites. The resulting electrodes exhibited very high reversible specific capacity almost 1.4~2.4 times the theoretical capacity of commercial graphite, and excellent capacity retention (~90%@50^th cycle) as compared with those of the existing transition metal oxides. From the analysis of the cumulative irreversible capacity and morphology change during charge/discharge cycling, it proved that the excellent capacity retention was attributed to the unique structural feature of our core-shell structure where only the thin CoO shell participates in the lithium storage. In addition, our electrodes showed a superb rate performance (70.5%@10.8 C-rate), most likely due to the open porous structure of 3D films, large surface area thanks to the dendritic structure, and fast electron transport through Cu core network.

• 전기화학회지
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• 제27권2호
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• pp.73-79
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• 2024

화석 연료의 사용이 증가함에 따라 이산화탄소와 같은 온실 가스의 배출량이 함께 증가하며 발생하는 환경 문제의 해결을 위해 이차전지와 같은 친환경 에너지 저장 기술이 주목받고 있다. 리튬 이온 전지의 중대형 전지를 제작하기 위해서는 고용량과 고효율 뿐만 아니라 우수한 안정성을 지니는 배터리의 전극 소재의 개발이 필수적이다. 이를 위해 고분자의 합성을 토대로 고용량을 얻을 수 있는 실리콘과 합성한 후 reduced Graphene Oxide (rGO)를 첨가하여 전극 활 물질을 제조해 물리적 특성과 전기화학적 성능을 분석하였다. 제조한 전극은 실리콘에 고분자를 탄화시켜 코팅하고 기계적 강도와 높은 안정성을 보이는 rGO를 첨가해 실리콘에 탄소를 코팅하는 Si@C 복합체에 비해 개선된 용량과 향상된 안정성을 보이는 것을 확인했다.

• 한국세라믹학회지
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• 제48권6호
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• pp.636-640
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• 2011

Nano-sized cobalt (II) oxide nanoparticles with a high crystallinity were synthesized using thermolysis of a $Co^{2+}$-oleate precursor at 310$^{\circ}C$. The phase and morphology of as-prepared cobalt oxide nanoparticles were characterized using X-ray diffraction, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller surface area measurements. The cobalt oxide nanoparticles were found to be spherical nanoclusters with an average diameter of approximately 200 nm, consisting of tiny nanocrystals (10-20 nm). Furthermore, the Li electroactivites of the cobalt oxide nanoparticles were investigated using cyclic voltammetry and galvanostatic cycling. The cobalt oxide nanoparticles could deliver high capacities over 420 mA h $g^{-1}$ at a C/5 current rate.

• 한국세라믹학회지
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• 제38권8호
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• pp.683-686
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• 2001

Electrochemically active lithium nickel cobalt oxide thin-film was not fabricated until now. The thin-film was deposited by RF magnetron sputtering at room temperature, and its initial phase was amorphous. By varying deposition condition, the different characteristics of thin-film were achieved. Using electrochemical analyses, the relationship between physical and electrochemical characteristics was identified. Crystallized thin-film by RTA (Rapid Thermal Annealing) was shown a good capacity and cycle property.

• 한국세라믹학회지
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• 제43권9호
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• pp.588-593
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• 2006

Spinel phase $LiMn_2O_4$ is of great interest as cathode materials for lithium-ion batteries. In this study, SHS (Self propagating High-temperature Synthesis) method to synthesize spinel $LiMn_2O_4$ directly from lithium nitrate, manganese oxide, manganese and sodium chloride were investigated. The influence of Li/Mn ratio, the heat-treated condition of product have been explored. The resultant $LiMn_2O_4$ synthesized under the optimum synthesis conditions shows perfect spinel structure, uniform particle size and excellent electrochemical performances.

• 청정기술
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• 제20권3호
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• pp.277-282
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• 2014

본 연구에서는 EVA를 바인더로 사용하여 우레탄 폼(PU)에 LMO를 고정화한 PU-LMO를 제조하였다. XRD 및 SEM 분석을 통해서 EVA에 의해 LMO가 폴리우레탄에 잘 고정화된 것을 확인할 수 있었다. PU-LMO를 제조시에 EVA/LMO의 최적비율은 0.26이었다. PU-LMO에 의한 리튬이온의 흡착 속도는 유사 2차 속도 모델식에 잘 부합하였다. 평형실험 데이터는 Langmuir 흡착 등온식에 잘 적용되었으며, 최대 흡착량은 17.09 mg/g이었다. PU-LMO는 리튬이온에 대한 분배계수($K_d$)가 다른 금속들의 $K_d$ 값에 비해 높게 나타나 뛰어난 리튬 이온 선택성과 높은 흡착량을 보였다.

• 한국수소및신에너지학회논문집
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• 제17권1호
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• pp.39-46
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• 2006

Highly ordered Li dispersed nickel oxide nanotubes were prepared with anodic aluminum oxide (AAO) template for hydrogen storage. Electron microscope results showed that uniform length and diameter of nickel oxide nanotubes were obtained. The wall thickness and outer diameter of nickel oxide nanotubes are about 40 - 50 nm and 200 - 400 nm, respectively. It was observed that the diameter of nickel oxide nanotubes is bigger than the pore diameter of AAO template. Li dispersed nickel oxide were consisted of nanoflakes and had structures of nanotubes and nanorods. For increasing the hydrogen adsorption and desorption capacity, the Li dispersed nickel oxide nanotubes were fluorinated. The fluorinated Li dispersed nickel oxide nanotubes showed 1.65 wt% of the hydrogen adsorption capacities at 77 K under 47 atm.

• 한국환경보건학회지
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• 제14권1호
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• pp.11-22
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• 1988

Calcium oxide, lithium oxide and titanium oxide were investigated as additives of zinc oxide for the removal of hydrogen sulfide at high temperature. This experiment was performed in the range of 1.0-2.0 vol.% H$_2$S concentration at 623-873 K reaction temperature, using a thermogravimetric analyzer. A pore blocking model was found to fit the reaction rate and the kinetics data were sucessfully expressed by this model. The reactions between additive sorbents and hydrogen sulfide were first order with respect to hydrogen sulfide concentration in a gaseous mixture with nitrogen. Among the used sorbents, ZnO-CaO 0.5 at.% and ZnO-TiO$_2$ 2.0 at.% sorbents had the best additive effects on the sulfidation reaction between additive sorbents and hydrogen sulfide, whereas the ZnO-Li$_2$O sorbents were ineffective.