• 한국세라믹학회지
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• 제41권1호
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• pp.86-91
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• 2004

기계 화학법에 의해서 70-300nm 수준의 입도 분포를 갖는 $LiCoO_2$ 양극 분말을 제작하였다. $K_2SO_4$에 의하여 코팅 된 Li-Co 전구체는 약 $800^{\circ}C$에서 고온상 $LiCoO_2$로 결정화 되었으며, 이때 이 온도까지는 열분해 또는 서로 반응을 하지 않는 $K_2SO_4$의 영향에 의하여 분말의 입성장이 억제되어 나노 크기에 접근하는 입자를 얻을 수 있었고, 상대적으로 큰 표면 에너지에 기인하여 입자의 모양이 구형에 가깝게 형성되어 졌다. 합성돤 분말은 상용화 분말과 동일한 결정특성을 보였으나 , 투과전자현미경의 회절패턴 분석결과, 층상 뿐 아니라 부분적으로 정방정의 $LiCoO_2$ 상을 갖는 것으로 나타났다. 이러한 정방정은 주로 입자 표면에 존재하게 되어 Li의 확산을 용이하지 않게 하므로, 합성된 $LiCoO_2$ 분말은 그 크기가 나노에 접근함에도 불구하고 전체 용량 및 rate 용량이 상용화 분할보다 더 낮은 값을 보였다. 이상의 결과로부터 뛰어난 고출력 및 고성능의 전지 제작을 위하여 분말의 크기를 미세화하는 작업은 물론 입자 표면의 결정상이 잘 조절된 분말을 사용하는 것이 바람직함을 알 수 있다.

• 전기화학회지
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• 제14권2호
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• pp.98-103
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• 2011

본 연구에서는 리튬 이차 전지의 양극 재료인 $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$을 공침법(co-precipitation)을 활용하여 성공적으로 합성하였다. 이때 $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$의 금속염 농도를 실험 변수로 하여 합성 조건을 변화 시키면서 금속염 농도 변화로 인한 전지 특성의 영향을 분석하였다. SEM(scanning electron microscope)과 XRD (X-Ray Diffraction) 분석결과 금속염의 농도(2몰/L)가 높을 경우 분말의 균일성과 구조의 결정성이 떨어져 전지 특성이 저하되는 현상이 발생하였다. 균일성과 결정성을 향상시키기 위하여 금속염의 농도(1몰/L)를 줄여 합성 한 결과 입도의 미분이 적고 균일성이 및 구조적 결정성이 증가됨을 확인하였다. 또한 충/방전 용량, C-rate, 사이클 등 전기화학적 특성에서도 상대적으로 우수한 특성을 보였다. 이러한 측정 결과를 바탕으로 $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ 물질의 금속염 농도에 따른 영향을 종합적으로 고찰하였다.

• 한국세라믹학회지
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• 제41권11호
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• pp.793-796
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• 2004

Process Parameters were studied in synthesis of LiCoO$_2$ Powder by ultrasonic spray Pyrolysis. Concentration of the mixed solution influenced the size, shape, and yield of the synthesized powder. The yield was affected primarily by the height of the solution, and then by the flow rate of a carrier gas. The temperature of the reactor governed the crystallinity and morphology of the powder. LiCoO$_2$ powders were synthesized as a layered high temperature phase above 800$^{\circ}C$. The synthesized powders were sphere and secondary Particles consisted of primary particles of 55-70 nm. The secondary Particles became bigger from 0.28 to 1.43 $\mu\textrm{m}$ as the concentration of the solution was increased from 0.05 to 2.0 M. The 2.0 M solution provided the highest production rate.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.355-359
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• 2010

A $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ cathode was modified by applying a $ZrF_x$ coating. The surface-modified cathodes were characterized by XRD, SEM, EDS, TEM techniques. XRD patterns of $ZrF_x$-coated $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ revealed that the coating did not affect the crystal structure of the parent powder. SEM and TEM images showed that $ZrF_x$ nano-particles were formed as a coating layer, and EDS data confirmed that $ZrF_x$ distributed uniformly on the surface the powder. Capacity retention of coated samples at high C rates was superior to that of pristine sample. However, as the coating concentration increases beyond the optimum concentration, the rate capability was deteriorated. Whereas, as the increase of coating concentration to 2.0 wt %, the cyclic performances of the electrodes under the severe conditions (high cut-off voltage, 4.8 V, and high measurement temperature, $55^{\circ}C$) were improved considerably.

• 한국수소및신에너지학회논문집
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• 제24권2호
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• pp.160-171
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• 2013

$LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ powder for cathode materials in lithium rechargeable batteries was treated by atmospheric plasma containing hydrogen to investigate the relationship between charge/discharge performance and physical/chemical changes of materials. Hydrogen plasma at atmosphere pressure was irradiated on the surface of active materials, and the change for their crystal structure, surface morphology, and chemical composition were observed by XRD, SEM-EDS and titration method, respectively. The crystal structure and surface morphology of $H_2$ plasma-treated powders were not changed but their chemical compositions were slightly varied. For charge/discharge test, $H_2$ plasma affected initial capacity and rate capability of active materials but continuous cycling was not subject to plasma treatment. Therefore, it was observed that $H_2$ plasma treatment affected the surface of materials and caused the change of chemical composition.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2584-2588
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• 2009

The effect of $LaF_3$ coating on the structural and electrochemical properties of $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_{2}$ cathodes was investigated using XRD, SEM, TEM, and a cycler. The coating layer consisted of nano-sized particles attached nonuniformly to the surface of pristine powder. Despite the surface coating treatment, phase difference by $LaF_3$ coating was not detected. The discharge capacities of coated electrodes were a little lower than that of pristine sample at a 1 C rate. However, as the C rate increases, the capacity retention of the coated sample becomes obviously superior to that of the pristine sample. The cyclic performances of the electrodes in the voltage range of 4.8 $\sim$ 3.0 V were also improved by the surface coating. Such enhancement is attributed to the presence of the $LaF_3$ coating layer, which effectively suppressd the reaction between electrodes and electrolytes on the surface of the $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_{2}$ electrode.

• 한국분말재료학회지
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• 제8권3호
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• pp.163-167
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• 2001

A bulk porous $CaZrO_3/MgO$ composite with plantinum nano-dispersion was synthesized in air atmosphere through the combination of several in situ reactions, including the pyrolysis of $PtO_2$. A mixture of $CaMg(CO_3)_2$(dolomite), $ZrO_2$, $PtO_2$ and LiF (0.5 wt%, as an additive) was cold isostatically pressed at 200 MPa and sintered at $1100^{\circ}C$ for 2 h. The porous $CaZrO_3/MgO/Pt$ composite ($CaZrO_3/MgO$ : Pt=99 : 1 in volume) had a uniformly open-porous structure (porosity: 56%) with three-dimensional (3-D) network and a narrow pore-size distribution, similarly to the porous $CaZrO_3/MgO$ composites reported before. Catalytic Properties (viz., NO direct decomposition and NO reduction by $C_2H_4$) of the $CaZrO_3/MgO/Pt$ composite were investigated up to $900^{\circ}C$. In the absence of oxygen, the NO conversion rate reached ~52% for the direct decomposition and ~100% for the reduction by $C_2H_4$, respectively. The results suggest the possibility of the porous composite as a multifunctional filter, i.e., simultaneous hot gas-filtering and $de-NO_x$ in one component.

• Bulletin of the Korean Chemical Society
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• 제30권8호
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• pp.1719-1723
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• 2009

The LiFeP$O_4$ powder was synthesized by using the solid state reaction method with Fe($C_2O_4){\cdot}2H_2O,\;(NH_4)_2HPO_4,\;Li_2CO_3$, and chitosan as a carbon precursor material for a cathode of a lithium-ion battery. The chitosan added LiFePO4 powder was calcined at 350 ${^{\circ}C}$ for 5 hours and then 800 ${^{\circ}C}$ for 12 hours for the calcination. Then we calcined again at 800 ${^{\circ}C}$ for 12 hours. We characterized the synthesized compounds via the crystallinity, the valence states of iron ions, and their shapes using TGA, XRD, SEM, TEM, and XPS. We found that the synthesized powders were carbon-coated using TEM images and the iron ion is substituted from 3+ to 2+ through XPS measurements. We observed voltage characteristics and initial charge-discharge characteristics according to the C rate in LiFeP$O_4$ batteries. The obtained initial specific capacity of the chitosan added LiFeP$O_4$ powder is 110 mAh/g, which is much larger than that of LiFeP$O_4$ only powder.