• 한국자기학회:학술대회 개요집
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• 한국자기학회 1998년도 춘계연구발표회 논문개요집
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• pp.68-69
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• 1998

• 전기화학회지
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• 제16권4호
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• pp.191-197
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• 2013

리튬2차전지용 양극소재인 $Li(Ni_{0.5}Co_{0.2}Mn_{0.3})O_2$를 공침법을 이용해 $Ni_{0.5}Co_{0.2}Mn_{0.3}(OH)_2$ 전구체로부터 합성하였고, 공침조건을 조절하여 전구체의 1차 입자 형상을 Flake형상과 Needle형상으로 제어하였다. 동일한 공정으로 리튬과 혼합하고 열처리하여, 입도, 탭밀도, 화학적 성분 등이 동일한 분체물성의 양극 소재를 합성하였다. 전구체의 1차입자 형상에 따른 $Li(Ni_{0.5}Co_{0.2}Mn_{0.3})O_2$의 전기화학적 특성을 평가하고, 이 특성의 변화를 SEM, XRD, EELS로 이용하여 분석하여 연관성을 고찰하였다. Needle형상 전구체로 합성한 $Li(Ni_{0.5}Co_{0.2}Mn_{0.3})O_2$ 양극의 1차입자는 Flake형상 전구체로 합성한 경우보다 작고, EELS결과로는 입자표면의 Li농도가 내부보다 상대적으로 높았다. 전기화학적인 수명과 출력특성에서 Needle형상 전구체로 합성한 양극이 Flake형상 전구체의 경우보다 우수한 특성을 보였는데, 임피던스 측정으로부터 낮은 전하이동저항에 연관되어 있을 것으로 생각된다.

• 한국재료학회지
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• 제9권10호
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• pp.985-991
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• 1999

Incoloy 800H, KSA (Kaeri Superalloy)-6, Inconel 600 및 Hastelloy C-276 합금의 용융염에서의 부식거동을 650~85$0^{\circ}C$ 온도범위에서 조사하였다. LiCl-Li$_2$O혼합용융염에서의 부식은 Li$_2$O에 의한 염기성 용해 기구에 의해 진행되며, 부식속도가 LiCl에서보다 훨씬 빠르게 나타났다. 혼합용융염 LiCl-Li$_2$O에서는 Ni기 합금의 부식속도가 Fe기 합금보다 빠르고, Mo와 W의 함량이 높은 Hastelloy C-276이 가장 빠른 부식속도를 나타내었다. 용융염 LiCl에서는 LiCrO$_2$의 단일 부식층이 형성되고, LiCl-Li$_2$O 혼합용융염에서는 산화물과 Ni의 2상구조의 다공성 부식층이 형성되었다.

• 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.

• 한국전기전자재료학회논문지
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• 제22권10호
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• pp.890-896
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• 2009

Li(Ni, Co, Mn)$O_2$ has been known as one of the most promising cathode materials for lithium secondary batteries. However, it has some problems to overcome for commercialization such as inferior rate capability and unstable thermal stability. In order to address these problems, surface modification of cathode materials by coating has been investigated. In the coating techniques, selection of coating material is a key factor of obtaining enhanced properties of cathode materials. In this work, we introduced solid electrolyte (Li-La-Ti-O) as a coating material on the surface of $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_2$ cathode. Specially, we focused on a rate performance of Li-La-Ti-O coated $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_2$ cathode. Both bare and Li-La-Ti-O 2 wt.% coated sample showed similar discharge capacity at 0.5C rate. However, as the increase of charge-discharge rate to 3C, the coated samples displayed better discharge capacity and cyclic performance than those of bare sample.

• 공업화학
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• 제10권3호
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• pp.491-495
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• 1999

졸겔법에 의하여 리튬전지용 $Ni_{0.2}V_2O_5$ aerogel (ARG) 양극 소재를 개발하여 전기화학적 특성을 조사하였다. ARG는 무정형의 층상화합물로 $400^{\circ}C$ 이상에서 열처리할 경우 orthorhombic 구조로 전환되었으며, 표면구조는 섬유 모양의 단위체가 서로 얽혀 일정한 방향으로 성장하여 비등방성 sheet를 형성하고 있다. 리튬 이온이 층간 삽입될 수 있는 다수의 특정한 에너지 준위의 자리가 ARG내에 존재하며, 전지의 평균전위는 3.1 V (vs. $Li/Li^+$) 이었다. ARG 리튬이차전지의 계면저항은 ARG층 내 리튬 몰분율에 상관없이 일정한 반면, 전하이동저항은 개로전압에서 최대이며 ARG내 리튬 이온의 농도가 증가할수록 증가하였다.

• 한국세라믹학회지
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• 제40권6호
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• pp.507-512
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• 2003

The LiN $i_{l-y}$ $Co_{y}$ $O_2$ samples were synthesized at 80$0^{\circ}C$ and 85$0^{\circ}C$, by the solid-state reaction method, from the various starting materials LiOH, L $i_2$C $O_3$, NiO, NiC $O_3$, $Co_3$ $O_4$, CoC $O_3$, and their electrochemical properties are investigated. The LiN $i_{l-y}$ $Co_{y}$ $O_2$ pre-pared from L $i_2$C $O_3$, NiO, and $Co_3$ $O_4$ exhibited the $\alpha$-NaFe $O_2$ structure of the rhombohedral system (space group; R3m). As the Co content increased, the lattice parameters a and c decreased. The reason is that the radius of Co ion is smaller than that of Ni ion. The increase in da shows that two-dimensional structure develops better as the Co content increases. The LiN $i_{0.7}$ $Co_{03}$. $O_2$［HOO(800,0.3)] synthesized at 80$0^{\circ}C$from LiOH, NiO, and $Co_3$ $O_4$ exhibited the largest first discharge capacity 162 mAh/g. The size of particles increases roughly as the valve of y increases. The samples with the larger particles have the larger first discharge capacities. The cycling performances of the samples with the first discharge capacity larger than 150 mAh/g were investigated. The LiN $i_{0.9}$ $Co_{0.1}$ $O_2$［COO(850,0.1)］ synthesized at 85$0^{\circ}C$ from L $i_2$C $O_3$, NiO, and $Co_3$ $O_4$ showed an excellent cycling performance. The sample with the larger first discharge capacity will be under the more severe lattice destruction, due to the expansion and contraction of the lattice during intercalation and deintercalation, than the sample with the smaller first discharge capacity. As the first discharge capacity increases, the capacity fading rate thus increases.increases.s.s.s.

• 한국세라믹학회지
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• 제42권9호
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• pp.631-636
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• 2005

$LiNi_{1-y}Ga_yO_2$ (y = 0.005, 0.010, 0.025, 0.050, and 0.100) were synthesized by the solid-state reaction method after mechanical mixing, and their_electrochemical properties were investigated. All the $LiNi_{1-y}Ga_yO_2$ (y=0.005, 0.010, 0.025, 0.050, and 0.100) samples had the R3m structure. The sample with y = 0.025 showed the largest first discharge capacity (131.4 mAh/g) and good cycling performance [discharge capacity 117.5 mAh/g ($89.4{\%}$ of the first discharge capacity) at the 20th cycle]. The first discharge capacity decreased as the value of y increased. The samples with y = 0.010 and y = 0.005 had small R-factor but their cycling performance was worse than that of the sample with y = 0.025. All the $LiNi_{1-y}Ga_yO_2$ samples had smaller discharge capacities than $LiNiO_2$, but their cycling performances were better than that of $LiNiO_2$.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.237-245
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• 2021

Atomic layer deposition (ALD) enhances the stability of cathode materials via surface modification. Previous studies have demonstrated that an Ni-rich cathode, such as LiNi_0.8Co_0.1Mn_0.1O₂, is a promising candidate owing to its high capacity, but is limited by poor cycle stability. In this study, to enhance the stability of the Ni-rich cathode, synthesized LiNi_0.8Co_0.1Mn_0.1O₂ was coated with Al₂O₃ using ALD. Thus, the surface-modified cathode exhibited enhanced stability by protecting the interface from Ni-O formation during the cycling process. The coated LiNi_0.8Co_0.1Mn_0.1O₂ exhibited a capacity of 176 mAh g^-1 at 1 C and retained up to 72% of the initial capacity after 100 cycles within a range of 2.8-4.3 V (vs Li/Li⁺. In contrast, pristine LiNi_0.8Co_0.1Mn_0.1O₂ presented only 58% of capacity retention after 100 cycles with an initial capacity of 173 mAh g^-1. Improved cyclability may be a result of the ALD coating, which physically protects the electrode by modifying the interface, and prevents degradation by resisting side reactions that result in capacity decay. The electrochemical impedance spectra and structural and morphological analysis performed using electron microscopy and X-ray techniques establish the surface enhancement resulting from the aforementioned strategy.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1598-1602
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• 2009

The particle size of Li[$Ni_{0.2}Li_{0.2}Mn_{0.6}]O_2$ cathode powder was controlled effectively by dispersion using lauric acid as a surfactant. The samples treated by lauric acid showed smaller particles of approximately half the original size compared to the particles of a pristine sample. A structural change due to the dispersion of Li[$Ni_{0.2}Li_{0.2}Mn_{0.6}]O_2$ powder was not detected. The rate performance of the Li[$Ni_{0.2}Li_{0.2}Mn_{0.6}]O_2$ cathode was improved by dispersion using lauric acid, which was likely due to the decrease of the particle size. In particular, a sample dispersed pristine powder using lauric acid (L2) presented a greatly enhanced discharge capacity and capacity retention at a high C rate. The discharge capacity of a pristine sample was only 133 m$Ahg^{-1}$ (3C rate) and 96 m$Ahg^{-1}$ (12C rate) at the tenth cycle. In contrast, the L2 electrode delivered higher discharge capacities of 160 m$Ahg^{-1}$ (3C rate) and 129 m$Ahg^{-1}$ (12C rate) at the tenth cycle. The capacity retention at a rate of 12C/2C was also enhanced from ~ 45% (pristine sample) to 57% (L2) by treatment with lauric acid.