Hyunjoo Bang

Effects of Metal Ions on the Structural and Thermal Stabilities of Li [ Ni1 − x − y Co x Mn y ] O2 ( x + y ⩽ 0.5 ) Studied by In Situ High Temperature XRD

Highly crystalline Li[Ni 1-x-y Co x Mn y ]O 2 (x + y ≤ 0.5) (Li[Ni 0.6 Co 0.2 Mn 0.2 ]O 2 , Li[Ni 0.55 Co 0.15 Mn 0.3 ]O 2 , and Li[Ni 0.5 Co 0.25 Mn 0.25 ]O 2 ) were synthesized through a coprecipitation method. The capacities of the prepared samples were proportional to the amount of Ni in the host structure. The thermogravimetric analysis (TGA) and in situ high-temperature-X-ray diffraction (HT-XRD) analysis revealed that changes in the amount of manganese ions in the host structure profoundly affect the structural stability of the samples with x + y ≤ 0.5. Li[Ni 0.55 CoO 0.15 Mn 0.3 ]O 2 , containing the highest manganese content (y = 0.3), showed the most stable structural integrity among the samples as confirmed by in situ HT-XRD. The electrochemical performances of the samples in Ni amount (0.5 ≤ 1 - x - y ≤ 0.6) with the variation of Co (0.15 ≤ x ≤ 0.25) did not significantly vary under the test conditions (3.0-4.3 V). The small increase of Mn ions plays an important role in preservation of its initial structural symmetry during the high-temperature heating as well as electrochemical cycling. Furthermore, the structural stability has a relationship with the thermal stability and the electrochemical stability, especially at an elevated temperature (55°C). On the basis of the differential scanning calorimetry and TGA results, the Li[Ni 0.55 Co 0.15 Mn 0.3 ]O 2 sample demonstrated improved thermal stability compared to the other samples.

Physical and Electrochemical Properties of Li [ Ni0.4Co x Mn0.6 − x ] O2 ( x = 0.1 – 0.4 ) Electrode Materials Synthesized via Coprecipitation

Highly crystalline Li[Ni 0.4 Co x Mn 0.6-x ]O 2 (x = 0.1-0.4) powders were synthesized from LiOH.H 2 O and coprecipitated [Ni 0 4Co x Mn 0 .6-x ](OH):, (x = 0.1, 0.2, 0.3 and 0.4) hydroxides. In order to evaluate the impact of Co and Mn ratio on the structure, X-ray absorption near edge spectroscopy (XANES) and Rietveld refinement analyses of X-ray diffraction data were carried out. XANES results indicated that the Li[Ni 0.4 Co x Mn 0.6-x ]O 2 (x = 0.1-0.4) consist of Ni 2+ , Co 3+ , and Mn 4+ in the crystal structure. Rietveld refinement analysis of the Li[Ni 0.4 Co x Mn 06-x ]O 2 (x = 0.1-0.4) revealed that an increase of Co content decreases both lattice parameters of a and c axes simultaneously. An increase of Co content results in an increase of specific discharge capacity, but the corresponding operation voltages were slightly shifted to lower voltage. Decreases in electrochemically inactive tetravalent Mn content in overall metal compositions are one of the possible reasons for the lowering of onset exothermic reaction temperature as confirmed by differential scanning calorimetric experiments.

Consecutive CVD of Al ∕ Co Bilayers on SiO2 or Alq3 Surfaces at Low Temperature of 70 ° C

There are difficulties in the nucleation of Al on SiO 2 and polymer surfaces at temperatures below 100°C using MPA as the Al precursor. In this study, Al/Co bilayer structures were deposited on SiO 2 or tris-(8-hydroxyquinoline) aluminum (Alq 3 ) surfaces at a low temperature of 70°C using a consecutive chemical vapor deposition (CVD) method. The use of Co 2 (CO) 8 as a precursor allowed the deposition of a continuous Co thin film on SiO 2 at 70°C, which provided effective nucleation sites for Al CVD at the same temperature. The predeposited Co underlayer was used to promote the nucleation of Al using MPA as the Al precursor. This resulted in the deposition of uniformly thick Al thin films with a smooth surface morphology (root-mean-square = 7.3 nm for 110 nm thick Al), a low resistivity of 4.2 μΩ cm, and negligible carbon contamination. Compared with the continuous films of Co on SiO 2 , there is isolated growth of Co on Alq 3 surfaces, which resulted in Al thin films with a rough surface (root-mean-square = 83.2 nm for 70-140 nm Al), a resistivity of 3.4-7.5 μΩ cm, and 3.0 atom % C contamination.

Electrochemical Properties of Spinel LiMn 2 O 4 Prepared Through Different Synthesis Routes

리튬이온전지의 스피넬형 양극활물질

Electrochemical characterization of Li2MnO3–Li[Ni1/3Co1/3Mn1/3]O2–LiNiO2 cathode synthesized via co-precipitation for lithium secondary batteries

LiMn_2O_4

Improvement of electrochemical and thermal properties of Li[Ni0.8Co0.1Mn0.1]O2 positive electrode materials by multiple metal (Al, Mg) substitution

의 입자 크기 및 비표면적의 전기화학 특성상의 영향을 고찰하기 위하여 스피넬 물질을 공침법과 고상법에 의해 합성되었다. X-선 회절분석을 통하여 합성된 두 물질 모두 Fd3m space group을 갖는 스피넬 구조가 형성된 것을 확인하였다. 공침법을 사용하여 얻은 물질은...