Hierarchically structured vanadium pentoxide/reduced graphene oxide composite microballs for lithium ion battery cathodes

Nakhanivej, Puritut,Park, Sul Ki,Shin, Kang Ho,Yun, Sol,Park, Ho Seok Elsevier 2019 Journal of Power Sources Vol.436 No.-

<P><B>Abstract</B></P> <P>Vanadium pentoxide is considered as a candidate of cathode material for lithium-ion batteries owing to its high specific capacity, large potential window, and short diffusion pathway. However, vanadium pentoxide has its own limitations such as insufficient electronic conductivity, sluggish ion diffusion, and volume expansion. In order to resolve these problems, we demonstrate spray frozen assembly into hierarchically structured open-porous vanadium pentoxide/reduced graphene oxide composite microballs for high performance lithium-ion battery cathodes. The uniform distribution of vanadium pentoxide particles immobilized onto the open-porous surface of reduced graphene oxide microballs is associated with the short ion diffusion pathway, the percolated electronic conduction, and the buffering space. Accordingly, vanadium pentoxide/reduced graphene oxide composite microballs achieve the initial discharge capacity of 273 mAh g<SUP>−1</SUP> at 100 mA g<SUP>−1</SUP> which is higher than those of reduced graphene oxide (78 mAh g<SUP>−1</SUP>) and vanadium pentoxide (214 mAh g<SUP>−1</SUP>). When the current density increases from 100 to 1000 mA g<SUP>−1</SUP>, the capacity retention of vanadium pentoxide/reduced graphene oxide composite microballs is 51.3%, much greater than 36.4% of vanadium pentoxide particles. The capacity retention of 80.4% with the Coulombic efficiency of 97.1% over 200 cycles is twice greater than that of V<SUB>2</SUB>O<SUB>5</SUB> particles, indicating improved cyclic stability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> V<SUB>2</SUB>O<SUB>5</SUB>/rGO composite microballs are synthesized by spray frozen assembly. </LI> <LI> V<SUB>2</SUB>O<SUB>5</SUB> particles are uniformly distributed onto the graphene microballs. </LI> <LI> Open porous structure provides fast Li ion diffusion pathway. </LI> <LI> Rate and cyclic capabilities of V<SUB>2</SUB>O<SUB>5</SUB> are improved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Life Science : Natural vanadium-containing Jeju ground water stimulates glucose uptake through the activation of AMP-activated protein kinase in L6 myotubes

( Seung Lark Hwang ),( Hyeun Wook Chang ) 영남대학교 약품개발연구소 2012 영남대학교 약품개발연구소 연구업적집 Vol.22 No.0

The aim of this study was to elucidate the effects of natural vanadium-containing Jeju ground water on glucose uptake in L6 myotubes and adipogensesis in 3T3 L1 cells. The Jeju ground water samplescontaining vanadium components were designated as S1 (8.0 ± 0.9 μg/l), S2 (24.0 ± 2.0 μg/l), and S3 (26.0 ± 2.0 μg/l), respectively. To investigate the effects of the Jeju ground water on glucose uptake in L6 myotubes, L6 cells were differentiated in media containing deionized distilled water (DDW group) and the water samples (S1, S2, and S3 groups). After daily changes in cultured media containing theJeju ground water samples for 1 week, all samples had increased glucose uptake compared to the DDW group and the order of glucose uptake increased in parallel with vanadium content (S3 > S2 > S1). In addition, S3 significantly stimulated the phosphorylation of the Thr-172 residue of the AMP-activated protein kinase-α subunit and the Ser-79 subunit of acetyl-CoA carboxylase compared to the DDW group. The effect of glucose uptake by S3 was reversed by pretreatment with Compound C, an AMPK inhibitor. Interestingly, vanadium pentoxide also increased glucose uptake and activated AMPK activity in a dose-dependent manner. Furthermore, as compared to the DDW treated group, S3 treatment inhibited adipogenesis of 3T3-L1 cells by down regulation of expressions of adipogenic transcription factors. Taken together, these findings suggest that S3 displays beneficial effects in the treatment of diabetes, at least in part through the activation of AMPK activity.

Measuring the Local Electrical Properties of Individual Vanadium-pentoxide Nanowires by Using Electrostatic Force Microscopy

김덕현,김태경 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.12

A nanoscale investigation of the local electrical properties of individual vanadium-pentoxide (V2O5) nanowires (NWs) deposited on a SiO2/p+ Si substrate was carried out by using electrostatic force microscopy (EFM) in ambient conditions. We found that the EFM phase shift as an electrostatic response of V2O5 NWs to the biased-tip decreases with the lift height due to the electrostatic force gradient. We also observed that the EFM phase shift of V2O5 NWs shows the quadratic voltage dependence for a biased-tip with a fixed lift height. Furthermore, it is observed that the crossed junctions or bundles of the NWs compared to the single NWs showed higher electrostatic response, resulting in a large phase shift in the EFM measurements. These results suggest that the local electrical properties of V2O5 NW surface can be characterized in the nanoscale range by using EFM.

기상 포름알데히드 전환을 위해 실리카 지지체에 담지된 복합금속산화물 촉매의 반응성 연구

홍유미,박영권,김성수,이승재 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

포름알데히드는 자극성이 강한 냄새로 무색을 가진 기체상의 화학 물질로 고체산 촉매를 이용하여 포름알데히드(FA) 전환율을 알아보았다. PVMo촉매인 Phosphoric acid를 0.005mol, 0.01mol, 0.015mol, 0.02mol 비율로 Vanadium pentoxide를 0.001mol, 0.005mol, 0.01mol, 0.02mol 비율로 Molybdenum trioxide 0.01mol, 0.05mol, 0.1mol, 0.2mol로 몰 비율에 따라 지지체 실리카(Si)를 함침법으로 담지 하였다. 반응 실험은 PVMo/Si 촉매를 이용하여 포름알데히드, 메탄올, 물(Formadehyde 95.1mol/mol), N2 Balance로 된 혼합가스를 이용하여 촉매 1g을 촉매 관에 넣은 후, 반응기 온도는 110°C에서 150°C까지 1h동안 포름알데히드 흘려보내면서 기체크로마토그래피를 이용하여 알아보았다. 촉매의 특성은 XRD, BET, TPD, NH3-TPD로 분석하였다.

Correlation between Friction and Thickness of Vanadium-Pentoxide Nanowires

김택영 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.9

We investigated the correlation between friction and thickness of vanadium-pentoxide nanowires (V2O5 NWs) by using friction/atomic force microscopy (FFM/AFM). We observed that the friction signal generally increased with thickness in the FFM/AFM image of the V2O5 NWs. We constructed a two-dimensional (2D) correlation distribution of the frictional force and the thickness of the V2O5 NWs and found that they are strongly correlated; i.e., thicker NWs had higher friction. We also generated a histogram for the correlation factors obtained from each distribution and found that the most probable factor is 0.45. Furthermore, we found that the adhesion force between the tip and the V2O5 NWs was about −3 nN, and that the friction increased with increasing applied load for different thicknesses of V2O5 NWs. Our results provide an understanding of tribological and nanomechanical studies of various one-dimensional NWs for future fundamental research.

리튬이차전지용 AgxCuyV2O5 Xerogel의 전기화학적 특성

박희구 ( Heai Ku Park ),김용우 ( Yong Woo Kim ),이만호 ( Man Ho Lee ),백승욱 ( Seung Uk Paik ) 한국공업화학회 2003 공업화학 Vol.14 No.4

바나듐 산화물계 양극소재의 물성을 향상시키고자 졸겔법을 이용하여 제조한 V_2O_5 xerogel에 미량의 Ag와 Cu 원소를 도핑시켜 Ag_xCu_yV_2O_5 xnogel을 제조하여 리튬이차전지용 양극소재로서의 전기화학적 및 표면특성을 연구하였다. Ag_xCu_yV_2O_5 xnogel은 무정형의 층상 intercalation 소재로 표면구조는 섬유모양의 단위체가 서로 얽혀 일정한 방향으로 성장하여 비등방성 sheet를 형성하고 있다. 도핑되어진 Ag와 Cu의 양에 따른 전지용량 및 출력특성 등이 첨가량에 따라 변하였다. 전지의 평균용량은 적어도 120 mAh/g 이상이며 coulombic efficiency는 90% 이상으로 산화 ·환원과정이 가역적이며 사이클 특성이 우수하였다. In order to improve the properties of vanadium oxide as cathodes, Ag_xCu_yV_2O_5 gel was synthesized by deliberately adding a small amount of Ag and Cu to a V_2O_5 sol derived via sol-gel process. The electrochemical properties of a new mixed oxide Ag_xCu_yV_2O_5 xerogel as a Li intercalation compound have been investigated in the relation with structural characteristics. It appeared the amorphous layered material and entangled fibrous textures have been grown to form anisotropic corrugated fibrils. The specific capacity and rate characteristics were dependent upon the added amount of dopant, Cu and Ag. Average specific capacity of the Ag_xCu_yV_2O_5 xerogel was more than 120 mAh/g, and coulombic efficiency was at least ninety percent. The overall electrochemical properties, the reversibility and cell capacity, were enhanced compared to the undoped vanadium pentoxide.

A Novel Process for Manufacturing Vanadium Dioxide(VO2) as a resource of Vanadium Electrolyte from Vanadium Pentoxide(V2O5)

Kim Byung-Su,Ryu Tae-Gong,Choi Jihyuk,Park Tae Jun,장한권,Yoo JeongHyun,Suh Chang-Youl,Cho Sung-Wook,Roh Kimin 한국자원공학회 2022 Geosystem engineering Vol.25 No.4

A vanadium electrolyte for energy storage is generally prepared by dissolving vanadium pentoxide (V2O5) in sulfuric acid using oxalic acid ((COOH)2) as a reducing agent. However, there is a disadvantage that the dissolution rate in the sulfuric acid solution of V2O5 is very slow. In this study, a new process for producing vanadium dioxide (VO2), which has the faster dissolution rate than V2O5 in sulfuric acid solution, was developed. Vanadium dioxide (VO2) could be used in the production of a vanadium electrolyte for energy storage. The process developed in the study has the advantages of being economical and simple as compared to the existing process for producing VO2 from V2O5 using hydrogen or carbon monoxide as a reducing agent.

바나듐 레독스 흐름 전지용 고순도 오산화바나듐 및 전해액 제조 연구

김선경,권숙철,홍혜진,서용재,장한권,전호석,박인수 한국자원공학회 2021 한국자원공학회지 Vol.58 No.1

We investigated the hydrolytic precipitation process with regard to purification of low-purity vanadium pentoxide (V2O5) to obtain high-purity vanadium electrolyte (VE) of a vanadium redox flow battery (VRFB). The lowest purities of VE and V2O5 for VRFB, which were reviewed through the purity analysis of commercial VE, were found to be 99.98% and 99.8%, respectively. The hydrolytic precipitation process applied to V2O5 powder with 99.7% and 98.3% purity resulted in V2O5 powder with a purity higher than 99.8%. However, the V2O5 powder contained impurities such as Fe and Ga. To further improve the purity, a two-step process comprising red cake precipitation was applied. However, this process exhibited a low vanadium recovery rate; therefore, development of a new single purification process with a high vanadium recovery rate is required. 본 연구에서는 VRFB의 고순도 바나듐 전해액을 제조하기 위해 저순도 오산화바나듐의 고순도화공정으로 가수분해 침전 공정을 적용하였다. 상용 바나듐 전해액 순도 분석을 통하여 검토한 VRFB 용 바나듐 전해액 및 오산화바나듐의 최저 순도는 각각 99.98% 및 99.8%로 확인되었다. 초기 순도가 99.7% 및 98.3%인 오산화바나듐에 가수분해 침전 공정을 적용할 경우 99.8% 이상의 고순도 오산화바나듐이 제조되었지만 Fe, Ga 성분이 불순물로 함유되었다. 추가적인 순도 향상을 위해 red cake 침전 단계를 포함하는 2단계 공정을 적용하였으나 바나듐 회수율이 감소하는 단점이 확인되었다. 따라서 향후 단일 공정으로 구성되어 높은 바나듐 회수율을 얻을 수 있는 고순도 바나듐 정제공정 개발이 필요하다.

킬레이트제를 활용한 VRFB용 고순도 오산화바나듐 제조 연구

김선경,권숙철,김희서,서용재,유정현,장한권,전호석,박인수 한국자원리싸이클링학회 2022 資源 리싸이클링 Vol.31 No.2

This study implemented a chelating agent (Ethylenediaminetetraacetic acid, EDTA) in purification to obtain high-purity vanadium pentoxide (V2O5) for use in VRFB (Vanadium Redox Flow Battery). V2O5 (powder) was produced through the precipitation recovery of ammonium metavanadate (NH4VO3) from a vanadium solution, which was prepared using a low-purity vanadium raw material. The initial purity of the powder was estimated to be 99.7%. However, the use of a chelating agent improved its purity up to 99.9% or higher. It was conjectured that the added chelating agent reacted with the impurity ions to form a complex, stabilizing them. This improved the selectivity for vanadium in the recovery process. However, the prepared V2O5 powder exhibited higher contents of K, Mn, Fe, Na, and Al than those in the standard counterparts, thus necessitating additional research on its impurity separation. Furthermore, the vanadium electrolyte was prepared using the high-purity V2O5 powder in a newly developed direct electrolytic process. Its analytical properties were compared with those of commercial electrolytes. Owing to the high concentration of the K, Ca, Na, Al, Mg, and Si impurities in the produced vanadium electrolyte, the purity was analyzed to be 99.97%, lower than those (99.98%) of its commercial counterparts. Thus, further research on optimizing the high-purity V2O5 powder and electrolyte manufacturing processes may yield a process capable of commercialization. 본 연구에서는 VRFB용 고순도 오산화바나듐을 제조하기 위한 불순물 분리 정제 공정에서 킬레이트제(EDTA)의 영향을 조사하였다. 저순도 바나듐 원료를 이용하여 제조된 바나듐 용액으로부터 NH4VO3 을 침전 회수하여 제조된 최종 V2O5 분말의 순도는 99.7%로 분석되었지만 NH4VO3 침전 회수 공정에서 킬레이트제를 첨가한 경우 최종 V2O5 분말 순도가 99.9% 이상으로 향상되었다. 이러한 결과는 첨가된 킬레이트제가 불순물 이온과 반응하여 complex를 형성하고 불순물 이온이 안정화되기 때문에 침전 회수 공정에서 바나듐에 대한선택성이 향상된 것으로 판단된다. 하지만 제조된 V2O5 분말내에는 불순물 규격 대비 K, Mn, Fe, Na 및 Al 함유량이 높아 추가적인 불순물 정제 연구가 필요하였다. 고순도 V2O5 분말을 새롭게 개발된 직접 전해공정에 적용하여 바나듐 전해액을 제조하였고 이의 특성을 상용 전해액과 비교 분석하였다. 제조된 바나듐 전해액의 순도는 불순물 K, Ca, Na, Al, Mg 및 Si 성분의 높은 함량으로 인하여 상용 전해액의 순도 99.98%보다 낮은 99.97%로 분석되었다. 따라서 고순도 V2O5 분말 및 전해액 제조 공정의 불순물 분리 정제에 대한 추가적인 최적화 연구가 수행된다면 상용화가 가능한 공정이 개발될 것으로 기대된다.

Atomic Layer Deposition of Vanadium Pentoxide on Carbon Electrode for Enhanced Capacitance Performance in Capacitive Deionization

정상호,봉성율,이재영 한국공업화학회 2022 공업화학 Vol.33 No.3

We firstly observed that activated carbon (AC) deposited by atomic-layer vanadium pentoxide (V2O5) was used as CDI electrodes to utilize the high dielectric constant for enhancing the capacitance equipped with atomic layer deposition (ALD). It was demonstrated that the vanadium pentoxide (V2O5) with sub-nanometer layer was effectively deposited onto activated carbon, and the electric double-layer capacitance of the AC was improved due to an increase in the surface charge density originated from polarization, leading to high ion removal in CDI operation. It was confirmed that the performance of modified-AC increases more than 200%, comparable to that of pristine-AC under 1.5 V at 20 mL min-1 in CDI measurements.