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고엔트로피세라믹을 이용한 암염 구조 양극 소재 연구 동향
김민정(Minjeong Kim),구자훈(Jahun Koo),강민정(Minjeong Kang),송주아(Juah Song),김천중(Chunjoong Kim) 한국세라믹학회 2022 세라미스트 Vol.25 No.1
Development of lithium-ion rechargeable batteries with high energy storage capability are required in timely manner. Recently, it has been experimentally and computationally proven that oxides with the disordered rock salt structure can be charged and discharged in the Li-ion battery system. In particular, the high entropy disordered rock salt cathode has unique structure property, where both Li-ion and transition metal are randomly located on the cation sites. Such disordering in metal sites can migrate the Li-ion in a percolating way albeit with sluggish kinetics. Therefore, the high entropy disordered rock salt structure has attracted great attention due to its high energy density and stable structure. In this paper, we introduce a simple and effective strategy in the selection of transition metals for high entropy cathodes to achieve desired electrochemical properties.
윤홍관,홍순현,김도진,김천중,Yun, Hongkwan,Hong, Soonhyun,Kim, Dojin,Kim, Chunjoong 한국재료학회 2019 한국재료학회지 Vol.29 No.1
Recent industrialization has led to a high demand for the use of fossil fuels. Therefore, the need for producing hydrogen and its utilization is essential for a sustainable society. For an eco-friendly future technology, photoelectrochemical water splitting using solar energy has proven promising amongst many other candidates. With this technique, semiconductors can be used as photocatalysts to generate electrons by light absorption, resulting in the reduction of hydrogen ions. The photocatalysts must be chemically stable, economically inexpensive and be able to utilize a wide range of light. From this perspective, cuprous oxide($Cu_2O$) is a promising p-type semiconductor because of its appropriate band gap. However, a major hindrance to the use of $Cu_2O$ is its instability at the potential in which hydrogen ion is reduced. In this study, gold is used as a bottom electrode during electrodeposition to obtain a preferential growth along the (111) plane of $Cu_2O$ while imperfections of the $Cu_2O$ thin films are removed. This study investigates the photoelectrochemical properties of $Cu_2O$. However, severe photo-induced corrosion impedes the use of $Cu_2O$ as a photoelectrode. Two candidates, $TiO_2$ and $SnO_2$, are selected for the passivation layer on $Cu_2O$ by by considering the Pourbaix-diagram. $TiO_2$ and $SnO_2$ passivation layers are deposited by atomic layer deposition(ALD) and a sputtering process, respectively. The investigation of the photoelectrochemical properties confirmed that $SnO_2$ is a good passivation layer for $Cu_2O$.
박지환,양하늘,홍순현,김천중,김도진,Park, Jihwan,Nguyen, Duc Quang,Yang, Haneul,Hong, Soonhyun,Truong, Thi Hien,Kim, Chunjoong,Kim, Dojin 한국재료학회 2018 한국재료학회지 Vol.28 No.5
Hydrothermal synthesis of highly crystalline $TiO_2$ nanorods is a well-developed technique and the nanorods have been widely used as the template for growth of various core-shell nanorod structures. Magneli/CdS core-shell nanorod structures are fabricated for the photoelectrochemical cell (PEC) electrode to achieve enhanced carrier transport along the metallic magneli phase nanorod template. However, the long and thin $TiO_2$ nanorods may form a high resistance path to the electrons transferred from the CdS layer. $TiO_2$ nanorods synthesized are reduced to magneli phases, $TixO_{2x-1}$, by heat treatment in a hydrogen environment. Two types of magneli phase nanorods of $Ti_4O_7$ and $Ti_3O_5$ are synthesized. Structural morphology and X-ray diffraction analyses are carried out. CdS nano-films are deposited on the magneli nanorods for the main light absorption layer to form a photoanode, and the PEC performance is measured under simulated sunlight irradiation and compared with the conventional $TiO_2/CdS$ core-shell nanorod electrode. A higher photocurrent is observed from the stand-alone $Ti_3O_5/CdS$ core-shell nanorod structure in which the nanorods are grown on both sides of the seed layer.
칼슘 도핑을 통한 고 에너지 밀도를 가지는 Ni-rich 층상 구조형 양극 소재의 안정화
강범희,홍순현,윤홍관,김도진,김천중,Kang, Beomhee,Hong, Soonhyun,Yoon, Hongkwan,Kim, Dojin,Kim, Chunjoong 한국재료학회 2018 한국재료학회지 Vol.28 No.5
Lithium-ion batteries have been considered the most important devices to power mobile or small-sized devices due to their high energy density. $LixCoO_2$ has been studied as a cathode material for the Li-ion battery. However, the limitation of its capacity impedes the development of high capacity cathode materials with Ni, Mn, etc. in them. The substitution of Mn and Ni for Co leads to the formation of solid solution phase $LiNi_xMn_yCo_{1-x-y}O_2$ (NMC, both x and y < 1), which shows better battery performance than unsubstituted $LiCoO_2$. However, despite a high discharge capacity in the Ni-rich compound (Ni > 0.8 in the metal site), poor cycle retention capability still remains to be overcome. In this study, aiming to improve the stability of the physical and chemical bonding, we investigate the stabilization effect of Ca in the Ni-rich layered compound $Li(Ni_{0.83}Co_{0.12}Mn_{0.05})O_2$, and then Ca is added to the modified secondary particles to lower the degree of cationic mixing of the final particles. For the optimization of the final grains added with Ca, the Ca content (x = 0, 2.5, 5.0, 10.0 at.%) versus Li is analyzed.
산화니켈 및 탄소나노튜브/산화니켈 복합체 가스센서의 제작과 황화수소 감지 특성
양하늘,박지환,홍순현,윤홍관,김천중,김도진,Yang, Haneul,Chinh, Ngyuen Duc,Hieu, Ngyuen Minh,Park, Jihwan,Hong, Soonhyun,yun, Hongkwan,Kim, Chunjoong,Kim, Dojin 한국재료학회 2018 한국재료학회지 Vol.28 No.8
Nickel oxide(NiO) thin films, nanorods, and carbon nanotube(CNT)/NiO core-shell nanorod structures are fabricated by sputtering Nickel at different deposition time on alumina substrates or single wall carbon nanotube templates followed by oxidation treatments at different temperatures, 400 and $700^{\circ}C$. Structural analyses are carried out by scanning electron microscopy and x-ray diffraction. NiO thinfilm, nanorod and CNT/NiO core-shell nanorod structurals of the gas sensor structures are tested for detection of $H_2S$ gas. The NiO structures exhibit the highest response at $200^{\circ}C$ and high selectivity to $H_2S$ among other gases of NO, $NH_3$, $H_2$, CO, etc. The nanorod structures have a higher sensing performance than the thin films and carbon nanotube/NiO core-shell structures. The gold catalyst deposited on NiO nanorods further improve the sensing performance, particularly the recovery kinetics.
전자빔 증발법 박막 증착을 이용한 양극 산화 알루미늄 템플릿의 나노 포어 가공 연구
이승훈(Seung-Hun Lee),이민영(Minyoung Lee),김천중(Chunjoong Kim),김관오(Kwanoh Kim),윤재성(Jae Sung Yoon),유영은(Yeong-Eun Yoo),김정환(Jeong Hwan Kim) 한국표면공학회 2021 한국표면공학회지 Vol.54 No.1
The fabrication of nanopore membrane by deposition of Al₂O₃ film using electron-beam evaporation, which is fast, cost-effective, and negligible dependency on substance material, is investigated for potential applications in water purification and sensors. The decreased nanopore diameter owing to increased wall thickness is observed when Al₂O₃ film is deposited on anodic aluminum oxide membrane at higher deposition rate, although the evaporation process is generally known to induce a directional film deposition leading to the negligible change of pore diameter and wall thickness. This behavior can be attributed to the collision of evaporated Al₂O₃ particles by the decreased mean free path at higher deposition rate condition, resulting in the accumulation of Al₂O₃ materials on both the surface and the edge of the wall. The reduction of nanopore diameter by Al₂O₃ film deposition can be applied to the nanopore membrane fabrication with sub-100 nm pore diameter.
리튬 이차전지용 전극 및 연료전지 촉매 소재 연구 개발 동향
윤홍관(Hongkwan Yun),김다희(Dahee Kim),김천중(Chunjoong Kim),김용진(Young-Jin Kim),민지호(Ji Ho Min),정남기(Namgee Jung) 한국세라믹학회 2018 세라미스트 Vol.21 No.4
In this paper, we review about current development of electrode materials for Li-ion batteries and catalysts for fuel cells. We scrutinized various electrode materials for cathode and anode in Li-ion batteries, which include the materials currently being used in the industry and candidates with high energy density. While layered, spinel, olivine, and rock-salt type inorganic electrode materials were introduced as the cathode materials, the Li metal, graphite, Li-alloying metal, and oxide compound have been discussed for the application to the anode materials. In the development of fuel cell catalysts, the catalyst structures classified according to the catalyst composition and surface structure, such as Pt-based metal nanoparticles, non-Pt catalysts, and carbon-based materials, were discussed in detail. Moreover, various support materials used to maximize the active surface area of fuel cell catalysts were explained. New electrode materials and catalysts with both high electrochemical performance and stability can be developed based on the thorough understanding of earlier studied electrode materials and catalysts.