Artificial cathode-electrolyte interphases on nickel-rich cathode materials modified by silyl functional group

Song, Hye Ji,Jang, Seol Heui,Ahn, Juhyeon,Oh, Si Hyoung,Yim, Taeeun Elsevier 2019 Journal of Power Sources Vol.416 No.-

<P><B>Abstract</B></P> <P>Nickel-rich nickel-cobalt-manganese layered oxides receive significant attention as advanced cathode materials, however, they suffer from poor cycling performance at elevated temperature because of surface instability. In this study, we develop nickel-rich cathode materials modified by an artificial cathode-electrolyte interphase layer embedding silyl ether functional groups. An artificial cathode-electrolyte interphase layer-functionalized nickel-rich cathode materials are simply synthesized via a wet-coating-based thermal treatment using a dimethoxydimethylsilane as an organic precursor. The task-specific silyl ether functional groups are effective in selectively scavenging nucleophilic fluoride species, which potentially triggers the dissolution of transition metal components into the electrolyte. Microscopic analyses indicate that the artificial cathode-electrolyte interphase layer is well developed on the surface of the nickel-rich cathode materials with several nanometers-thickness. The cells cycled with functionalized nickel-rich cathodes exhibit much higher cycling retentions (∼70.0%) than the cell cycled with bare nickel-rich cathode (47.1%) at high temperature. Additional systematical analyses indicate that the artificial cathode-electrolyte interphase layers effectively mitigate the electrolyte decomposition and the dissolution of transition metal components, thereby improving the cycling behavior of the cell on the basis of increased interfacial stability of nickel-rich cathode materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Artificial CEI layer was introduced by Si-based precursor on Ni-rich NCM cathode. </LI> <LI> Si-based artificial CEI layer was provided by wet coating-based one-step process. </LI> <LI> Task-specific Si–O functional groups on CEI layer were effective in F<SUP>−</SUP> scavenging. </LI> <LI> Si-based CEI layer improved interfacial stability of Ni-rich NCM cathode. </LI> <LI> Si-based artificial CEI layer allowed enhanced cycle retention at high temperature. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

대관령의 일조시간을 이용한 월별 일사량의 추정

박진기, 오시영, 백신철, 김봉섭, 신형섭, 박종화 忠北大學校 農業科學硏究所 2013 農業科學硏究 Vol.29 No.1

The monthly mean daily global solar radiation and sunshine duration, have been employed in this study to develop correlation model for Daegwallyeong during 2011. The corresponding monthly value of extraterrestrial solar radiation and possible duration of sunshine are calculated for Daegwallyeong meteorological data. Forecasting performance parameters such as coefficient of determination (R2), mean bias error (MBE) and root mean square error (RMSE) are presented as analyzed for the model. The model with multi-linear regression has the highest R2 value of 0.95 and average MBE and RMSE values of −0.11 MJ/m2day and 1.63 MJ/m2day, respectively. The model exhibited negative MBE which shows that the model resulted in underestimation of the global solar radiation relative to the meteorological measured value. The equation could be employed in the estimation of solar radiation at Daegwallyeong, other locations with similar meteorological characteristics.

Simultaneous etching and transfer — Free multilayer graphene sheets derived from C₆₀ thin films

Hudaya, Chairul,Ahn, Minjeh,Oh, Si Hyoung,Jeon, Bup Ju,Sung, Yung-Eun,Lee, Joong Kee Elsevier 2018 Journal of industrial and engineering chemistry Vol.64 No.-

<P><B>Abstract</B></P> <P>Despite the advantage of chemical vapor deposition (CVD) for realization of large area epitaxial growth of graphene on transition metal catalysts, both etching and transfer process of CVD-grown graphene sheets still remain a big challenge. Here we demonstrate the formation of multilayer graphene (MLG) sheets tailored from C<SUB>60</SUB> thin films on the top of Si/Ni substrate without etching and transfer steps based on Ni films. This self-assembled process separates the MLG sheets from the conductive Ni catalyst, embarking a possibility for direct characterizations of MLG sheets. The fine-tuned C<SUB>60</SUB> films (30nm) are transformed into approximately 17 MLG sheets, thus making it large-area MLG sheets for a variety of direct applications.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis and Characterization of Cathode Materials for the Lithium Secondary Batteries by Spray Drying Method

Oh, Si-Hyoung,Jeong, Woon-Tae,Cho, Won-Il,Cho, Byung-Won The Korean Electrochemical Society 2005 한국전기화학회지 Vol.8 No.1

It has been known that the synthesis of the cathode materials for the lithium rechargeable batteries by the sol-gel process has many advantages over the conventional solid-state method. It has been, however, a continuing issue that new additional steps should be introduced to commercialize this process. In this work, spray drying was introduced to the existing sol-gel process as a continuous mass production method of the pre-heat treatment precursor materials. The precursors of $LiCoO_2$ and $LiNi_{0.8}Co_{0.2}O_2$ were continuously produced through spray drying from the solution containing stoichiometric amount of lithium, cobalt, and nickel sources as well as a chelating agent. The process variables, such as pH of the starting solution, spray drying conditions, and calcination conditions were optimized. The XRD pattern for the synthesized material indicated a good crystallinity with a layered structure.

신생아 및 영아 피부에서 Malassezia 효모균의 분포

오창근,권경술,이채욱,조시형,장호선,박재형 대한의진균학회 1999 대한의진균학회지 Vol.4 No.1

Background: Malassezia yeasts are normal skin flora of humans. But skin colonization appear to be controversial during neonate. Objective: We prospectively studied the distribution of Malassezia yeasts on clinically normal skin of neonates and infants for providing the basic data for proving the relationship of Malassezia yeasts and pathogenesis of the diseases of neonates and infants. Methods: A total of 200 subjects were studied using the direct smear test with 20% Parker ink/KOH solution. The numbers of the Malassezia yeasts per high power field were counted according to a bacterial index of lepra bacilli in patients of leprosy In order to identify risk factors for the distribution of Malassezia yeasts, we compared sex, mode of delivery, gestational age, birthweight during the first week of life by statistical method of the logistic regression. Results: Of the 200 neonates and infants under 12 weeks, 121 (60.5%) revealed Malassezia yeasts in at least a part of five examined sites. The prevalence of Malassezia yeasts was increased according to the age. No association was found between the incidence of Malassezia yeasts and sex, mode of delivery, gestational age, birth weight. Conclusion: We conclude that Malassezia yeasts colonize on the skin of neonates and infants.

Trends in the Incidence and Treatment of Cerebrovascular Diseases in Korea : Part I. Intracranial Aneurysm, Intracerebral Hemorrhage, and Arteriovenous Malformation

Lee, Si Un,Kim, Tackeun,Kwon, O-Ki,Bang, Jae Seung,Ban, Seung Pil,Byoun, Hyoung Soo,Oh, Chang Wan The Korean Neurosurgical Society 2020 Journal of Korean neurosurgical society Vol.63 No.1

Objective : To analyze the incidence and treatment trends of hemorrhagic stroke (HS), according to HS subtypes, using nationwide data in Korea from January 2008 to December 2016. Methods : We used data from the national health-claim database provided by the National Health Insurance Service for 2008-2016 using the International Classification of Diseases. The crude incidence and age-standardized incidence of each disease associated with HS, which included intracranial aneurysm (IA), hypertensive intracerebral hemorrhage (ICH), and arteriovenous malformation (AVM), were calculated and additional analysis was conducted according to age and sex. Changes in trends in treatment methods and number of treatments were analyzed for each cerebrovascular disease using the Korean Classification of Diseases procedure codes. Results : In 2016, the total number of newly diagnosed adult patients with HS was 24169, showing a decrease by 7.0% since 2008; the age-standardized incidence of HS was 46.2 per 100000 person-years. The age-standardized incidence of unruptured IA (UIA) in adults was 71.4 per 100000 person-years-increased by 2.6-fold since 2008-while that of ruptured IA (RIA) was 12.6 per 100000 person-years, which had decreased at a rate of 20.3% since 2008. The number of coil embolization (CE) for UIA increased by 3.4-fold over 9 years and exceeded that of clipping since 2008. With respect to RIA, CE increased by 2.0-fold over 9 years and exceeded that of clipping from 2014. As for spontaneous ICH in adults, the age-standardized incidence was 31.3 per 100000 person-years in 2016-decreased by 34.7% since 2008-and 14.6% of patients diagnosed with ICH were treated in 2016, which was not significantly different from the proportion of patients treated since 2008. The age-standardized incidence of unruptured AVM (UAVM) was 2.0 per 100000 person-year in 2016, while that of ruptured AVM (RAVM) was 2.4 per 100000 person-years in 2016, showing a decreasing rate of 17.2% from 2008. The total number of treated patients with AVM declined since 2014. Conclusion : In Korea, age-related cerebral vascular diseases, such as RIA, ICH, and RAVM, demonstrated a declining trend in age-standardized incidence; meanwhile, UIA and UAVM demonstrated an increased trend in both crude incidence and age-standardized incidence for 9 years. The increase in the elderly population, management of hypertension, and development of diagnostic and endovascular techniques appear to have influenced this trend.

마이크로프로세서 기반의 실내 주차정보 제공 시스템 설계 및 구현

유시온(Si-On Yoo),오형진(Hyoung-Jin Oh),오갑석(Kab-Suk Oh) 한국컴퓨터정보학회 2010 韓國컴퓨터情報學會論文誌 Vol.15 No.1

아파트단지, 대형 빌딩, 마트 또는 백화점에는 많은 차량을 수용할 수 있는 실내 주차장이 구비되어 있으나, 운전자는 혼잡한 주차장에서 빈 주차구역을 찾기 위해 상당한 시간을 낭비하고 있다. 본 연구에서는 운전자가 혼잡한 주차장에서 현황모니터를 통해 빈 주차공간을 찾기 위해 배회하는 시간을 줄이고, 주차된 차량의 위치를 찾기 쉽도록 SMS(Short Message Service)를제공하는마이크로프로세서기반의실내주차정보제공시스템을제안한다. 제안시스템은 차량 출입 검출용 RFID(Radio-Frequency IDentification) 시스템, 주차면의 차량유무 관련 정보처리 및 서버와의 통신 등의 기능을 갖춘 마이크로프로세서 시스템, 진출입 차량의 정보처리와 운전자에게 빈 주차공간 및 주차정보를 안내하는 서버 시스템으로 구성하였다. 수작업으로 제작한 8대 규모의 모형주차장에 제안 시스템을 구현하였으며, 주차 현황 모니터와 유료 문자메시지 서비스로 운전자에게 정보를 제공함으로써 실용성을 확인하였다. Apartment complex, buildings, markets and department stores have inner parking lots which can accept many cars but drivers waste lots of times to find the empty parking spaces in crowding parking lots. In this paper, we proposed the inner parking information support system based on microprocessor which can decrease roaming times to find vacant parking spot in confusing parking lots through notice monitor and provide SMS to make it easy to find parked place. Proposed system consist with RFID system for detecting access of cars, microprocessor system for processing data of checking existence of cars on parking spots and communicating with server, and server system which processes information of cars' in and out, guides empty parking spots and parked location to drivers. Suggested system is realized by handmade model parking lot size of 8 cars, and we confirmed practicality by providing information using parking notice monitor and single message service.

The effect of vanadium precursors on the electrochemical performance of Li1.1V0.9O2 as an anode material for Li-ion batteries

Ahn, Juhyeon,Oh, Si Hyoung,Kim, Jong Hak,Cho, Byung Won,Kim, Hyung Sun Springer-Verlag 2014 Journal of electroceramics Vol.32 No.4

An open-framework iron fluoride and reduced graphene oxide nanocomposite as a high-capacity cathode material for Na-ion batteries

Ali, Ghulam,Oh, Si Hyoung,Kim, Se Young,Kim, Ji Young,Cho, Byung Won,Chung, Kyung Yoon The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.19

<▼1><P>Cathode materials with high capacity and good stability for rechargeable Na-ion batteries (NIBs) are few in number.</P></▼1><▼2><P>Cathode materials with high capacity and good stability for rechargeable Na-ion batteries (NIBs) are few in number. Here, we report a composite of electrochemically active iron fluoride hydrate and reduced graphene oxide (rGO) as a promising cathode material for NIBs. Phase-pure FeF3·0.5H2O is synthesized by a non-aqueous precipitation method and a composite with rGO is prepared to enhance the electrical conductivity. The encapsulation of FeF3·0.5H2O nanoparticles between the rGO layers results in a lightweight and stable electrode with a three-dimensional network. The composite material delivers a substantially enhanced discharge capacity of 266 mA h g<SUP>−1</SUP> compared to 158 mA h g<SUP>−1</SUP> of the bare FeF3·0.5H2O at a current density of 0.05 C. This composite also shows a stable cycle performance with a high capacity retention of >86% after 100 cycles, demonstrating its potential as a cathode material for NIBs.</P></▼2>

Screening for SuperoxideReactivity in Li-O₂ Batteries: Effect on Li₂O₂/LiOH Crystallization

Black, Robert,Oh, Si Hyoung,Lee, Jin-Hyon,Yim, Taeeun,Adams, Brian,Nazar, Linda F. American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.6

<P>Unraveling the fundamentals of Li-O<SUB>2</SUB> batterychemistryis crucial to develop practical cells with energy densities that couldapproach their high theoretical values. We report here a straightforwardchemical approach that probes the outcome of the superoxide O<SUB>2</SUB><SUP>–</SUP>, thought to initiate the electrochemicalprocesses in the cell. We show that this serves as a good measureof electrolyte and binder stability. Superoxide readily dehydrofluorinatespolyvinylidene to give byproducts that react with catalysts to produceLiOH. The Li<SUB>2</SUB>O<SUB>2</SUB> product morphology is a functionof these factors and can affect Li-O<SUB>2</SUB> cell performance.This methodology is widely applicable as a probe of other potentialcell components.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-6/ja2111543/production/images/medium/ja-2011-111543_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja2111543'>ACS Electronic Supporting Info</A></P>