• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.219-223
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• 2000

All-solid state lithium rechargeable thin film batteries were fabricated with the configuration of$Cu_{0.5}V_2O_5/Lipon/Li$ using sequential thin film techniques. Copper vanadium oxide thin films and Lipon thin films were prepared by DC reactive dual source magnetron sputtering and RF magnetron sputtering, respectively. According to XRD analysis, we found out that copper vanadium oxide thin films were amorphous. The electrochemical behaviour of them was examined in half cell system using EC : DMC(1:1 in IM $LiPF_5$) liquid electrolyte. The ionic conductivity of Lipon thin film was $1.02\times10^{-6}S/cm$ at $25^{\circ}C$ and $Cu_{0.5}V_2O_5/Lipon/Li$ cell showed that the discharge capacity was about $50{\mu}Ah/cm^2{\mu}m$ beyond 500cyc1es.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.292-299
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• 2014

In this study, nitrogen doped carbon felt (CFt) is prepared using thermal oxidation and liquid phase ammonia treatment to improve the efficiency for vanadium redox flow batteries (VRFB). The electrochemical properties of prepared CFt electrodes are investigated using cyclic voltammetry (CV) and charge/discharge test. The XPS result shows that the increase of liquid phase ammonia treatment temperature leads to the increased nitrogen functional group on the CFt surface. Redox reaction characteristics using CV reveal that the liquid phase ammonia treated CFt electrodes are more reversible than the thermally oxidized CFt. When CFt is treated by the liquid phase ammonia at $300^{\circ}C$, VRFB cell energy efficiency, voltage efficiency, and current efficiency are increased about 6.93%, 1.0%, and 4.5%, respectively, compared to those of the thermally oxidized CFt. These results are because nitrogen functional groups on CFt help to improve the electrochemical properties of redox reaction between electrode and electrolyte interface.

• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.49-56
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• 2010

This study investigated how the surface of Al-12wt.%Si alloy modified by the plasma electrolytic oxidation process (PEO). The PEO process was performed in an electrolyte with sodium hexametaphsphate as a conducting salt, and the effect of ammonium metavanadate on variations in the morphology of electrochemically generated oxide layers on the alloy surface was investigated. It is difficult to form a uniform passive oxide layer on Al alloys with a high Si content due to the differences in the oxidation behavior of the silicon-rich phase and the aluminum-rich phase. The oxide layer covered the entire surface of the Al-12WT.%Si alloy uniformly when ammonium metavanadate was added to the electrolyte. The oxide layer was confirmed as a mixture of $V_2O_3$ and $V_2O_5$ by XPS analysis. In addition, the oxide layer obtained by the PEO process with ammonium metavanadate exhibited a black color. Application of this surface modification method is expected to solve the problem of the lack of uniformity in the coloring of oxide layeres caused by different oxidation behaviors during a surface treatment.

• Journal of the Korean Ceramic Society
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• v.38 no.3
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• pp.274-279
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• 2001

Pt/Ti/Si 기판 위에 성장시킨 박막 전지용 비정질 산화 바나듐 박막에 고상 전해질 박막 LiPON을 이용하여 전고상형 박막전지를 제작하여 충-방전 시험을 시행하였다. 이렇게 제작된 전고상형 박막전지는 500 사이클 이상까지 평균 15$\mu$Ah의 방전용량을 나타내었으나 초기 사이클 영역부터 방전 용량의 감소가 일어나기 시작했다. 박막 전지의 방전 용량 감소에 따른 비정질 산화 바나듐 박막의 구조적 특성 변화를 관찰하기 위하여 고분해능 현미경 분석을 시행하였다. 충-방전을 하지 않은 초기의 산화 바나듐 박막은 입계를 갖지 않고 다결정 특성을 보이지 않는 완전한 비정질 특성을 보였고 이는 TED 결과와 일치하였다. 그러나 450번의 반복적인 충-방전을 시행한 후의 비정질 산화 바나듐 박막 내에는 microcrystalline 형태의 산화 바나듐의 형성됨을 고분해능 전자 현미경 분석을 통해 발견할 수 있었다. 비정질 산화바나듐 박막의 방전 용량 감소의 원인인 Li의 비가역적 탈-삽입은 비정질 내에 형성된 microcrystalline에 의해 유발된다고 사료된다. 또한 LiPON 전해질 박막과 산화 바나듐 박막사이의 계면에 Li 이온과 산화바나듐과의 반응에 의해 형성된 계면 층에 발견할 수 있었는데 이러한 계면 층 역시 Li 확산과 계면 저항에 영향을 주어 방전 용량 감소에 원인으로 작용한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.304-304
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• 2006

Ternary tellurite glassy systems ($Li_2O-V_2O_5-TeO_2$) have been synthesised using Vanadium oxide as a network former and Lithium oxide as network modifier. The addition of a metal oxide makes them electric or mixed electric-ionic conductors, which are of potential interest as cathode materials for solid-state batteries. This glass-ceramics crystallized from the $Li_2O-V_2O_5-TeO_2$ system are particularly interesting, because they exhibit high conductivity (up to $5.63{\times}10^{-5}$ S/cm) at room temperature the glass samples were prepared by quenching the melt on the copper plate and the glass-ceramics were heat-treated at crystallizing temperature determined from differential thermal analysis (DTA). The electric DC conductivity result have been analyzed in terms of a small polaron-hopping model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.334-335
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• 2005

Ternary tellurite glassy systems ($Li_2O-V_2O_5-P_2O_5$) have been synthesised using Vanadium oxide as a network former and Lithium oxide as network modifier. The addition of a metal? oxide makes them electric or mixed electric-ionic conductors, which are of potential interest as cathode' materials for solid-state batteries. This glass-ceramics crystallized from the $Li_2O-V_2O_5-P_2O_5$ system are particularly interesting, because they exhibit high conductivity (up to $5.95\times10^{-4}$ S/cm) at room temperature. the glass samples were prepared by quenching the melt on the copper plate and the glass-ceramics were heat-treated at crystallizing temperature determined from differential thermal analysis (DTA). The electric D.C conductivity result have been analyzed in terms of a small polaron-hopping model.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.197-197
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• 2016

Commercially pure titanium (CP Ti) and Ti-6Al-4V alloys have been widely used for biomedical applications. However, the use of the Ti-6Al-4V alloy in biomaterial is then a subject of controversy because aluminum ions and vanadium oxide have potential detrimental influence on the human body due to vanadium and aluminum. Hence, recent works showed that the synthesis of new Ti-based alloys for implant application involves more biocompatible metallic alloying element, such as, Nb, Hf, Zr and Mo. In particular, Nb and Hf are one of the most effective Ti ${\beta}-stabilizer$ and reducing the elastic modulus. Plasma electrolyte oxidation (PEO) is known as excellent method in the biocompatibility of biomaterial due to quickly coating time and controlled coating condition. The anodized oxide layer and diameter modulation of Ti alloys can be obtained function of improvement of cell adhesion. Manganese(Mn) plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. Radio frequency(RF) magnetron sputtering in the various PVD methods has high deposition rates, high-purity films, extremely high adhesion of films, and excellent uniform layers for depositing a wide range of materials, including metals, alloys and ceramics like a hydroxyapatite. The aim of this study is to research the Mn coatings on the micro-pore formed Ti-29Nb-xHf alloys by RF-magnetron sputtering for dental applications. Ti-29Nb-xHf (x= 0, 3, 7 and 15wt%, mass fraction) alloys were prepared Ti-29Nb-xHf alloys of containing Hf up from 0 wt% to 15 wt% were melted by using a vacuum furnace. Ti-29Nb-xHf alloys were homogenized for 2 hr at $1050^{\circ}C$. Each alloy was anodized in solution containing typically 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate at room temperature. A direct current power source was used for the process of anodization. Anodized alloys was prepared using 270V~300V anodization voltage at room. Mn coatings was produced by RF-magnetron sputtering system. RF power of 100W was applied to the target for 1h at room temperature. The microstructure, phase and composition of Mn coated oxide surface of Ti-29Nb-xHf alloys were examined by FE-SEM, EDS, and XRD.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.557-564
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• 2021

Sr_0.92Y_0.08Ti_1-xV_xO_3-δ (SYTV) with perovskite structure was investigated as an alternative anode to utilize H₂S containing fuels in solid oxide fuel cells. To improve the electrochemical performance of Sr_0.92Y_0.08TiO_3-δ (SYT), vanadium(V) was substituted to titanium(Ti) at the B-site of the SYT perovskites. The SYTV synthesized by the Pechini method was chemically compatible with the YSZ electrolyte without additional by-products formation under the cell fabricating conditions. As increasing V substitution amounts, the oxygen vacancies increased, resulting to increasing ionic conductivity of the anode. The cell performance in pure H₂ at 850 ℃ is 19.30 mW/cm² and 34.87 mW/cm² for a 1 mol.% and 7 mol.% of V substituted anodes, respectively. The cell performance using H₂ fuel containing 1000 ppm of H₂S at 850 ℃ was 23.37 mW/cm² and 73.11 mW/cm² for a 1 mol.% and 7 mol.% of V substituted anodes, respectively.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.44-48
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• 2000

Amorphous $V_2O_5$ cathode thin films were prepared by DC-magnetron sputtering at room temperature and the thin film rechargeable lithium batteries were fabricated with the configuration of $V_2O_5/LIPON/Li$ using sequential ex-situ thin film deposition techniques. The electrochemical characteristics of $V_2O_5$ cathode materials Prepared at 80/20 of $Ar/O_2$ ratio showed high capacity and cycling behaviors by half cell test. LIPON solid electrolytes films were prepared by RF-magnetron sputtering using the self-made $Li_3PO_4$ target in pure $N_2$ atmosphere, and it was very stable for lithium contact in the range of 1.2-4.0 V vs. Li. Metallic lithium were deposited on LIPON electrolyte by thermal evaporation methode in dry room. Vanadium oxide based full cell system showed the initial discharge capacity of $150{\mu}A/cm^2{\mu}m$ in the range of $1.2\~3.5V$.

• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.148-154
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• 2019

Vanadium oxide based materials have been studied as novel negative electrode materials in lithium-ion batteries (LIBs) because of their high specific capacity. In this study, potassium metavanadate ($KVO_3$) was synthesized and its electrochemical properties are evaluated as a negative electrode materials. The aqueous solution of $NH_4VO_3$ is mixed with a stoichiometric amount of KOH. The solution is boiled to remove $NH_3$ gas and dried to obtain a precipitate. The obtained $KVO_3$ powders are heat-treated at 300 and $500^{\circ}C$ for 8 h in air. As the heat treatment temperature increases, the initial reversible capacity decreases, but the cycle performance and Coulombic efficiency are improved slightly. On the contrary, the electrochemical performances of the $KVO_3$ electrodes are greatly improved when a polyacrylic acid (PAA) as binder was used instead of polyvinylidene fluoride (PVDF) and a fluoroethylene carbonate (FEC) was used as electrolyte additive. The initial reversible capacity of the $KVO_3$ is 1169 mAh/g and the Coulombic efficiency is improved to 76.3% with moderate cycle performance. The $KVO_3$ has the potential as a novel high-capacity negative electrode materials.