Studies of sodiation behaviors in Sn anodes using in situ electron microscopy

변영운 Graduate School, Korea University 2020 국내박사

Studies of sodiation behaviors in Sn anodes using in situ electron microscopy Young-Woon Byeon Department of Materials Science and Engineering, Korea University Supervised by Prof. Jae-Chul Lee Abstract In this thesis, we investigate the sodiation behaviors by using in situ diffusion experiments and TEM based microstructural analyses. This is made up of five chapters. The first chapter consists of the general theories of the battery and the recent research trends of in situ experiments in anode materials. Chapter II addresses the phase transitions of sodiated Sn (NaxSn) phases and their electrical properties. Chapter III and IV address fundamental issues on diffusion, such as isotropic and self-limiting behaviors of sodiation reaction in c-Sn. At last, chapter V addresses the overall conclusion and prospects of this study. Chapter II is a study of the origin of high Coulombic loss during sodiation in Na–Sn battery. In this work, we measured the electrical properties of the sodiated Sn (NaxSn) phases during the in situ sodiation experiments. We observe that sodiation causes an increase in the Sn anode resistivity by six orders of magnitude. Ab initio molecular dynamics simulations of the Na–Sn alloy system demonstrate that the increased resistivity of the anode is caused by the formation of an electrically resistive amorphous NaSn phase (a-NaSn) with a pseudogap. It is also observed that the formation of a-NaSn is always accompanied by a large volume expansion of ~200%, causing the development of residual tensile stress. The residual stress in turn alters the electronic structure of the a-NaSn phase, further increasing the resistivity of a-NaSn and thus decreasing the energy efficiency of the Na–Sn battery. Chapter III is the study of the isotropic sodiation behavior of ultrafast-chargeable tin crystals. We demonstrate that both the high rate performance and mechanical stability of the anode can be achieved with the Na-Sn battery system. In situ experiments show that the rate of sodiation in crystalline Sn (c-Sn) is 2-3 orders of magnitude faster than that reported for the Li-Si system. Furthermore, this extraordinary rate is nearly the same regardless of the orientation of c-Sn, which can improve the cycle life by retarding the pulverization of c-Sn. Two main microstructural features responsible for the observed characteristics are identified: 1) a crystalline-to-amorphous phase transformation at thin layers of c-Sn near the propagating interface and 2) pipe diffusion of Na through sodiation-induced dislocations. Chapter IV is the study of the diffusion along dislocations mitigates self-limiting Na diffusion in crystalline Sn. We perform a comparative study of Li-Si and Na-Sn systems to elucidate how the differing diffusion kinetics displayed by the two systems can influence SLD behaviors and the rate performance of batteries. Experiments show that the diffusion of Na+ ions into soft Sn crystals induces stresses near the propagating interface, promoting the nucleation of high-density dislocations. Dislocations thus formed provide pathways for dislocation pipe diffusion and lower the Gibbs energy in the system. These behaviors, observed from the Na-Sn system, facilitate Na diffusion at ultrafast rates and mitigate SLD behaviors, making crystalline Sn suitable for fast-charging anode material with high energy density. This study offers some design criteria that can be used as basic guidelines for the appropriate choice of potential anode materials with superior rate performance and energy capacity suitable for future electric vehicles. The outcomes of the present thesis, we provide experimental methodologies to investigate the diffusion behavior of carrier ion in electrode material and its effect on battery properties. Our long-term goal is to develop the design-rule of electrode materials for ultrafast charging batteries. Advanced batteries in the near future need high-level safety with ultrafast charging systems, which will accelerate the development of electrode materials. Our results based on in situ characterization technique contributes to propose the best directionalities for the research and development for future batteries. The success of implementing the ultrafast charging technology will provide various light energy storage devices.

Relations among different topologies on a locally convex topological vector space : Yong-sung Byeon

Byeon, Yong-sung Korea University 1972 국내석사

PCR-Free DNA detection by cycling TMSD

Byeon, Gyeongyeon Sungkyunkwan University 2023 국내석사

In this study, the detection of extremely low concentrations of DNA was demonstrated using UV-visible Spectrophotometer without PCR. The Cycling TMSD method is based on the TMSD method of exchanging DNA strands by changing complementary nucleotide sequences without enzymes and can amplify signals by cycling the target DNA. In addition, gold nanoparticles that have excellent optical effects and are easy to bind to DNA as probe materials, and magnetic particles that have good extraction ability and can increase concentration are used. DNA was attached to each nanoparticle, and Cycling TMSD was verified by SEM, UV-visible, and electrophoresis. Low concentration DNA detection was verified through UV-visible in a probe material. Finally, DNA was quantitatively detected up to the aM level. We propose an ultrasensitive DNA detection analysis method. 본 연구에서는 PCR에 의존하지 않고 UV-visible 분광광도계를 사용하여 매우 낮은 농도의 DNA 검출이 입증되었습니다. Cycling TMSD 방법은 효소 없이 상보적인 염기서열을 바꾸어 DNA 가닥을 교환하는 TMSD 방법을 기반으로 하며 Target DNA를 순환시켜 신호를 증폭할 수 있습니다. 각각의 나노 입자에 DNA를 부착하고, Cycling TMSD에 대한 반응의 결과를 SEM, UV-visible spectrum, 전기 영동 등으로 확인하였습니다. 극 저농도의 DNA 검출은 프로브 물질인 금 나노 입자에 부착된 Probe DNA에의해 UV-visible을 통해 검증되었습니다. 최종적으로 DNA는 aM 수준까지 검출할 수 있으며 1개의 염기서열이 불일치한 DNA를 검출 하였을 때 Target과 확연한 차이를 보았습니다. 이는 민감하고 선택성이 좋은 초고감도의 DNA 검출 분석법을 제안합니다.

Involvement of microRNAs in the pathogenesis of carbamazepine-induced liver injury

Byeon, Jiyeong Sungkyunkwan university 2017 국내박사

Application of silicon photonic microring resonators to the study of surface bioconjugation and protein capture agent binding kinetics

Byeon, Ji-yeon UMI Dissertation Services 2011 국내박사

(The) Role of P21-activated kinase 2 (PAK2) on the IFN-β-induced senescence and autophagy in vascular smooth muscle cells

Byeon, Hyeeun Sungkyunkwan University 2014 국내박사

Preparation and evaluation of target-specific drug delivery systems for treating cancer and arthritis

Byeon, Hyeongjun Sungkyunkwan university 2016 국내박사

Molecular response and biotransformation of arsenic compounds in aquatic invertebrates

Byeon, Eunjin Sungkyunkwan University 2023 국내박사

비소는 환경에 널리 분포하는 준금속으로 잔류성과 축적이 잘 되는 특성 때문에 독성물질로 여겨진다. 현재까지 수생환경에서 비소의 발생, 분포 및 생물학적 영향에 대해 광범위하게 연구되어 왔으며, 비소에 대한 급성 및 만성 독성은 개체에서 분자 수준까지 치명적인 영향과 관련이 있다고 알려져있다. 수생생물에서 비소의 독성은 비소의 종류와 농도에 따라 달라진다. 수생환경에서 무기비소는 가장 지배적인 형태이며 3가 비소는 5가 비소에 비해 더 큰 독성을 가지고 있다. 무기비소는 수생생물에서 생체 내 변환을 통해 다양한 형태로 나타날 수 있다. 생체 내 변환 기작과 비소의 종 분화는 광범위하게 연구되어 왔지만, 생물 내에서의 화학적 종 분화, 독성 및 생물 이용성 사이의 관계를 다루는 연구는 아직 부족하다. 따라서 본 연구에서는 수생생물에서 생체 내 변환 기작과 비소 독성의 작용방식을 이해하기 위해 해양 및 담수 무척추동물에서 비소에 대한 반응기작을 중심으로 연구를 진행하였다. (1) 해양 윤충류 (Brachionus plicatilis) 및 요각류 (Paracyclopina nana)에서 비소 화합물의 종간 생체 내 변환 및 해독 기작 연구, (2) 미소 및 미세 플라스틱과 결합된 비소 노출이 윤충류 B. plicatilis에 미치는 영향 연구, (3) Glutathione S-tranferase omega 2 (GST-O2) 유전자 표적 담수 물벼룩 Daphnia magna 돌연변이에서 비소에 대한 차등 감수성 연구. 본 연구에서, 두 종의 동물플랑크톤 사이에서 비소에 대한 종 의존적인 민감도가 나타났다. 두 유기체 모두에서 3가 비소 (AsIII)는 5가 비소 (AsV)보다 독성이 더 강하게 나타났으며, 윤충류 B. plicatilis는 요각류 P. nana보다 더 강한 내성을 보였다. 또한 비소 노출 시 생물 특이적인 생체 내 변환과 항산화 반응이 관찰되었다. 게다가, 윤충류 B. plicatilis에서 플라스틱 입자의 크기에 따라 비소 독성 및 생물 내 축적이 다르게 나타날 수 있음이 관찰되었다. 미소 플라스틱 (nanoplastic)과 비소의 결합 노출 시, 다중 생체이물 내성 (MXR)의 억제로 인한 비소의 생체 농도 증가로 인해 더욱 높은 독성을 유도한 반면, 미세 플라스틱 (microplastic)은 생물에 미치는 비소 독성을 완화시켰다. 마지막으로, CRISPR/Cas9 시스템에 의해 생산된 야생형 및 GST-O2 표적 돌연변이 물벼룩을 이용하여 D. magna의 비소 생체변환 및 해독과 관련된 GST-O2 유전자의 역할을 조사하였다. GST-O2 유전자의 부재는 비소해독 능력과, AsV를 AsIII로의 환원율을 감소시켰으며, GST-O2가 D. magna의 비소 대사 기능에 중요한 역할을 한다는 것을 시사했다. 본 연구는 수생 유기체에 미치는 비소 독성 및 종간 해독 기작에 대한 이해와, 비소 및 환경 오염물질의 작용방식에 대한 심층적인 이해에 도움을 줄 것이다. Arsenic is a toxic metalloid that is widely distributed in the aquatic environment. Acute and chronic arsenic intoxications are associated with fatal effects at the individual and molecular levels. The toxicity of arsenic to aquatic organisms depends on its speciation and concentration. In aquatic environments, inorganic arsenic is the dominant form, and can assume a variety of forms through biotransformation in aquatic organisms. Biotransformation mechanisms and speciation of arsenic have been studied extensively, but only a few reports have addressed the relationships among speciation, toxicity, and bioavailability in biological systems. Therefore, to understand the modes of action of arsenic toxicity along with its mechanism of biotransformation in aquatic organisms, I have focused on studying the response to arsenic in aquatic invertebrates through: (1) interspecific biotransformation and detoxification of arsenic compounds in marine rotifer and copepod; (2) arsenic exposure combined with nano- or microplastic induces different effects in the marine rotifer Brachionus plicatilis; (3) differential susceptibility to arsenic in glutathione S-transferase omega 2 (GST-O2)-targeted freshwater water flea Daphnia magna mutants. In my studies, species-specific sensitivity to arsenic was found between Brachionus plicatilis and Paracyclopina nana. The rotifer B. plicatilis exhibited stronger tolerance to arsenic, compared to the P. nana. Lineage-specific biotransformation and antioxidant responses upon arsenic exposure were shown. Moreover, I observed that arsenic toxicity and bioaccumulation could be different depending on the size of plastic particles in the rotifer B. plicatilis. Exposure to arsenic combined with nanoplastic (NP) induced higher toxicity due to the increased bioconcentration of arsenic that is possibly associated with multixenobiotic resistance (MXR) inhibition, while microplastic (MP) alleviated arsenic toxicity. Finally, using the GST-O2-targeted mutant fleas D. magna produced by CRISPR/Cas9, the role of GST-O2 genes was investigated in the biotransformation and detoxification. The absence of the GST-O2 gene decreased the ability of detoxification and pentavalent arsenic reduction rate, suggesting that GST-O2 plays an important role in arsenic metabolic functions in D. magna. Overall, these findings will be helpful for a better understanding of arsenic toxicity and interspecific-detoxification mechanisms in aquatic invertebrates, as well as an in-depth insight into the effects of arsenic and environmental pollutants.

Development of dibenzofuran type host materials for blue phosphorescent and TADF organic light-emitting diodes for improved device operational lifetime

Byeon, Sungyong Sungkyunkwan university 2019 국내박사

The dibenzofuran type host materials were designed and synthesized to improve device operational lifetime in blue phosphorescent and thermally activated delayed fluorescent (TADF) organic light-emitting diodes (OLEDs). The dibenzofuran moiety was chosen as building block of the host materials, because it has high triplet energy above 3.0 eV and moderate charge transport property and energy levels, thus can be widely utilized as necessary. The new host materials in this paper were synthesized to suppress exciton-exciton annihilation and exciton-polaron annihilation processes, which are main degradation processes of OLEDs. At first, the bulky and non-conjugated triphenylsilyl substituent was introduced to the blue phosphorescent host and revealed that the triphenylsilyl group suppressed trplet exciton quenching of the blue phosphorescent emitters. The external quantum efficiency (EQE) and device lifetime were improved through substitution of triphenylsilyl group. Secondly, dibenzofuran type host materials were applied to the electron transport type (ET) host material for blue TADF emitter to extend device operational lifetime. The mixed host system was used at different composition of hole and electron transport type host materials. The larger amount of ET host leaded improved device lifetime through broadened recombination zone and carrier balance. Thirdly, cyano (CN) group substituted dibenzofuran host were synthesized to figure out the relationship between the device lifetime and the lowest unoccupied molecular orbital (LUMO) energy levels by CN substituents. The improved electron transport property and deepened LUMO energy level alleviated polaron induced annihilation process and resulted in improved device lifetime. Finally, the LUMO distributions of the ET host were modified with different positions of the CN substituents. The two CN units were introduced in the ET host that the one had one CN units in the phenyl linker and one CN unit in the carbazole, and another host had two CN units in the carbazole moiety. The two host materials showed significant difference in LUMO distributions and energy levels. The host with one CN unit in the phenyl core showed higher EQE above 20% and also extended device lifetime in blue TADF OLEDs. The extended device lifetime was due the reduced electron trapping effect by deep LUMO energy level and widened recombination zone by small electron injection barrier relieved exciton quencing processes.

Dielectric properties and structural distortion of BaTiO3

Byeon, Sanggyun Sungkyunkwan university 2019 국내석사

Barium titanate (BaTiO3) is a ferroelectric material used in many applications. In addition, since it has a simple crystal structure, it has an advantage that an artificial ceramic can be easily produced. However, Barium titanate (BaTiO3) has dielectric properties sensitive to thickness. It is known that as the thickness of BaTiO3 becomes thin, the ferroelectric polarization disappears due to its influence on the surface. The surface of BaTiO3 with perovskite structure generates an electric field opposite to the direction of dielectric polarization by the surface effect. This electric field makes it difficult to maintain the dielectric polarization and the ferroelectricity disappears. We adapted BaTiO3 slab structure with different thickness for the first principles calculation. Two termination of the surfaces (i.e. TiO2 and BaO surface) were considered. As the thickness of BaTiO3 decreased down to a few unit cell thickness, dielectric constant decrease rapidly. The surface structure of the thin BaTiO3 were analyzed and the decrease in the dielectric constant was attributed to surface structure. 티탄산바륨(BaTiO3)은 많은 응용분야에서 사용되고 있는 강유전체이다. 또한, 간단한 결정구조를 가지고 있기 때문에 인공적인 세라믹을 쉽게 만들 수 있다는 장점을 가지고 있다. 그러나, 티탄산바륨(BaTiO3)은 두께에 민감한 유전 특성을 가지고 있습니다. BaTiO3의 두께가 얇아지면 강유전체 분극이 표면에 미치는 영향으로 강유전성 분극이 사라지는 것이 알려져 있다. 페로브스카이트 구조(perovskite)를 갖는 BaTiO3의 표면은 표면 효과에 의해 유전 분극 방향과 반대 방향의 전기장(depolarization field)을 발생시킨다. 이 전기장은 유전 분극량을 유지하기 어렵게 하여 강유전성이 사라집니다. 우리는 제 1 원리 계산을 위해 두께가 다른 BaTiO3 슬래브 구조를 채택했습니다. 표면의 2개의 Termination (즉, TiO2 및 BaO 표면)을 고려되었다. BaTiO3의 두께가 단위 셀 두께의 몇 배로 감소함에 따라 유전율은 급격히 감소한다. 얇은 BaTiO3의 표면 구조가 분석되었고 유전율의 감소는 표면 구조에 의해 영향을 받았다.