Magnesium silicide-derived porous Sb-Si-C composite for stable lithium storage

Seo, Hyungeun,Kim, Han-Seul,Kim, Kyungbae,Choi, Hyunjoo,Kim, Jae-Hun Elsevier 2019 Journal of alloys and compounds Vol.782 No.-

<P><B>Abstract</B></P> <P>Porous Sb-Si-C composite materials were synthesized through two-step high-energy mechanical milling (HEMM) and chemical etching processes as an anode material for lithium secondary batteries. Sb<SUB>2</SUB>O<SUB>3</SUB> and Mg<SUB>2</SUB>Si as starting materials were transformed into Sb, Si, and MgO phases after the first step of HEMM. Activated carbon was then incorporated into the composites during the second step of the milling. Finally, porous composites were synthesized by removing MgO through chemical etching. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, electron microscopy, and Brunauer–Emmett–Teller (BET) surface area measurement. The electrochemical lithiation and delithiation mechanism of the porous Sb-Si-C nanocomposite electrode was examined by using ex situ XRD analysis. Electrochemical test results demonstrated that the reversible capacity of approximately 450 mAh g<SUP>−1</SUP> was maintained well after 200 cycles. This performance can be attributed to the porous structure and the amorphous carbon matrix for alleviation of volume changes during repeated Li<SUP>+</SUP> insertion and extraction cycling.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Porous Sb-Si-C composite materials were synthesized through a simple and cost-effective method. </LI> <LI> The reversible capacity of approximately 450 mAh g<SUP>−1</SUP> was maintained well after 200 cycles as Li battery anodes. </LI> <LI> The porous structure with a high surface area of 153.5 m<SUP>2</SUP> g<SUP>−1</SUP> was helpful for stable Li storage performance. </LI> <LI> The reaction mechanism with Li ions was examined by ex situ X-ray diffraction method. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Electrochemical Characteristics of Synthesized Nb₂O₅-Li₃VO₄ Composites as Li Storage Materials

( Youngmo Yang ),( Hyungeun Seo ),( Jae-hun Kim ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.4

The increasing demand for energy storage in mobile electronic devices and electric vehicles has emphasized the importance of electrochemical energy storage devices such as Li-ion batteries (LIBs) and supercapacitors. For reversible Li storage, alternative anode materials are actively being developed. In this study, we designed and fabricated an Nb₂O₅-Li₃VO₄ composite for use as an anode material in LIBs and hybrid supercapacitors. Nb₂O₅ powders were dissolved into a solution and the precursors were precipitated onto Li₃VO₄ through a simple, low-temperature hydrothermal reaction. The annealing process yielded an Nb₂O₅-Li₃VO₄ composite that was characterized by X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy. Electrochemical tests revealed that the Nb₂O₅-Li₃VO₄ composite electrode demonstrated increased capacities of approximately 350 and 140 mAh g^-1 at 0.1 and 5 C, respectively, were maintained up to 1000 cycles. The reversible capacity and rate capability of the composite electrode were enhanced compared to those of pure Nb₂O₅-based electrodes. These results can be attributed to the microstructure design of the synthesized composite material.

Facile synthesis and electrochemical properties of carbon-coated ZnO nanotubes for high-rate lithium storage

Kim, Han-Seul,Seo, Hyungeun,Kim, Kyungbae,Lee, Jaegab,Kim, Jae-Hun Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.15

<P><B>Abstract</B></P> <P>ZnO is an important functional material, and a nanotube structure is beneficial for various applications. Here, we report the facile synthesis and electrochemical properties of carbon-coated ZnO nanotube materials as Li rechargeable battery anodes. ZnO nanorod was first synthesized via a simple hydrothermal method. Subsequently, the material was annealed with a carbon precursor, forming free-standing, carbon-coated ZnO nanotubes. The carbon-coated nanotube structure is beneficial to alleviate volume changes of the ZnO active material during Li insertion and extraction processes as well as to improve the electrochemical reaction kinetics. Electrochemical test results demonstrate that the carbon-coated ZnO nanotube electrodes deliver improved the cycling performance compared with ZnO nanorod electrodes. Better rate performance than carbon-coated ZnO nanoparticle electrodes was also achieved.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Free-standing, carbon-coated ZnO nanotubes were prepared by a facile synthetic route. </LI> <LI> Carbon-coating process was simultaneously performed with morphology transformation from nanorods to nanotubes. </LI> <LI> The carbon-coated ZnO nanotubes exhibited enhanced rate performance compared to carbon-coated ZnO nanoparticles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Electrochemical and Thermal Property Enhancement of Natural Graphite Electrodes via a Phosphorus and Nitrogen Incorporating Surface Treatment

김경배,Han-Seul Kim,Hyungeun Seo,김재헌 한국부식방식학회 2020 Corrosion Science and Technology Vol.19 No.1

An efficient wet process approach to modifying natural graphite (NG) electrodes for Li-ion batteries is introducedin this paper. With homogeneous mixing and thermal decomposition of NG with diammonium phosphate((NH4)2HPO4), phosphorus and nitrogen were successfully incorporated into the surface layer of NG particles. Electron microscopy and X-ray photoelectron spectroscopy analyses demonstrated that the surface was wellmodified by this process. As a result, the treated NG electrodes exhibited much improved electrochemicalperformance over pristine NG at two different temperatures: 25 °C and 50 °C. Excellent capacity retentionof 95.6% was obtained after 100 cycles at 50 °C. These enhanced properties were confirmed in a morphologyanalysis on the cross-sections of the NG electrodes after galvanostatic cycling. The improved cycle andthermal stabilities can be attributed to the surface treatment with phosphorus and nitrogen; the treatmentformed a stable solid electrolyte interphase layer that performed well when undergoing Li insertion andextraction cycling.

Surface-controlled Nb2O5 nanoparticle networks for fast Li transport and storage

Kim, Kyungbae,Hwang, Junesun,Seo, Hyungeun,Kim, Han-Seul,Kim, Jae-Hun Springer-Verlag 2019 JOURNAL OF MATERIALS SCIENCE - Vol.54 No.3

Microstructure Design of Carbon-Coated Nb2O5–Si Composites as Reversible Li Storage Materials

Dahye Park,Kyungbae Kim,Han-Seul Kim,Hyungeun Seo,Hyun Seung Lee,Hyunjoo Choi,Jae-Hun Kim 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.4

We report on a rationally designed microsphere composite consisting of Nb2O5 and Si nanoparticles for application to secondary Li batteries as an anode material. The micron-sized spherical Nb2O5–Si composite was first prepared using a solvothermal method with appropriate surfactants. Heat treatment was performed to achieve both crystallization of Nb2O5 and pyrolysis of the carbon precursor, yielding a carbon-coated Nb2O5–Si microsphere composite. To characterize the synthesized material, X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy were employed. The electrochemical test results demonstrated that the composite electrode delivered a high capacity of approximately 900 mAh g−1 after 100 cycles. This improved cycling stability can be attributed to the microstructure. In the microsphere composite, Si nanoparticles play a role as the main active material for Li storage; however, they suffer large volume changes during Li insertion and extraction cycling. In our composite material, crystallized orthorhombic Nb2O5 buffers the volume change and facilitates rapid Li transport through its microspheres. Additionally, the carbon coating layer acts as a secondary buffering medium and propels fast electronic/ionic transport.

World Health Organization Integrated Care for Older People (ICOPE) and the Integrated Care of Older Patients with Frailty in Primary Care (ICOOP_Frail) Study in Korea

원장원,Eunmi Ha,Eunjin Jeong,김미지,Juhyun Park,Ja Euk Baek,Sungouk Kim,Sung Bae Kim,Jihun Roh,Jee Hye Choi,Seung Youn Jeon,Heeeun Jung,Daehyun Lee,Yuri Seo,Hyungeun Shin,Heesun Kim 대한노인병학회 2021 Annals of geriatric medicine and research Vol.25 No.1

The World Health Organization (WHO) recently endorsed the proposal for a Decade of Healthy Ageing (2020–2030). The WHO defines “healthy aging” as “the process of developing and maintaining the functional ability that enables wellbeing in older age.” Among the strategies for the Decade of Healthy Ageing, the WHO has suggested enhancing intrinsic capacity, promoting functional ability, and implementing the Integrated Care for Older People (ICOPE) package. The WHO has defined steps for ICOPE evaluation and scale-up and is performing a prospective study in 2–3 countries (low and middle income, high income) to test its feasibility in 2021–2022 and a multinational randomized study to validate its clinical efficacy and effectiveness in 2022–2024. Intrinsic capacity and frailty represent two faces of the same coin, with one indicating the reserves of the individual and the other indicating the deficits that accumulate with age. The Integrated Care of Older Patients with Frailty in Primary Care (ICOOP_Frail) study is the first integrated care program for frailty or functional decline in primary care in Korea. The results suggest that the ICOOP_Frail study can be utilized as a reference for ICOPE studies in Korea or at least to provide important findings for the forthcoming ICOPE implementation study in Korea.

COVID-19로 인한 비대면 수업에 따른 간호대학생의 수업공정성, 전공만족도, 간호윤리 가치관 및 간호전문직관의 관련성

서형은 ( Seo¸ Hyung-eun ),김혜진 ( Kim¸ Hye-jin ) 한국융합과학회 2021 한국융합과학회지 Vol.10 No.5

연구목적: 본 연구는 COVID-19로 인해 비대면 수업을 경험한 간호대학생의 수업공정성, 전공만족도, 간호윤리 가치관, 간호전문직관 간의 관련성을 규명하기 위한 것이다. 연구방법: 본 연구는 서술적 조사연구이며, 대상자는 자가보고식 설문지를 작성한 200명의 국내 간호대학생이었다. 2021년 2월 8일부터 2월 28일까지 자료를 수집하였으며, 수집된 자료는 SPSS 26.0 및 AMOS 21.0을 사용하여 분석하였다. 결과: 간호대학생의 수업공정성과 전공만족도는 간호윤리 가치관의 수준을 예측하는 중요한 변수였으며, 24.0%의 설명력을 나타냈다. 매개변수로서 간호윤리 가치관은 간호전문직관에 대한 수업공정성에 부분매개 효과가 있는 것으로 나타났으며, 73.4%를 설명하였다. 간호윤리 가치관은 간호전문직관의 수준을 예측하는 중요한 변수로 나타났다. 결론: 간호대학생의 간호전문직관 확립을 위해서는 긍정적이고 확고한 간호윤리 가치관을 형성하고, 수업공정성에 대한 인식 및 전공만족도를 높여야 할 필요가 있다. Purpose: The purpose of this study was to investigate the relationship between class fairness, satisfaction with the major, nursing ethical values, and nursing professionalism of nursing students who experienced non-face-to-face classes due to COVID-19. Methods: This study was a descriptive survey design, and participants were 200 domestic nursing students who completed the self-report questionnaire. Data were collected from February 8 to 28, 2021 and analyzed using SPSS 26.0 and AMOS 21.0. Result: Nursing students’ class fairness and satisfaction with the major were important variables predicting the level of nursing ethical values. Nursing ethical values as a mediator was found to have a partial mediating effect of class fairness of nursing students on nursing professionalism, accounted for 73.4% of the variance. Nursing ethical values were found to be an important variable predicting the level of nursing professionalism. Conclusion: In order to establish nursing professionalism among nursing students, it is necessary to establish positive and firm nursing ethical values, and to increase class fairness and satisfaction with the major.