소듐 이온 전지 고용량 음극 물질로서 황도핑된 그래핀과 황화주석에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 화학생물공학부, 2018. 8. 성영은.Lithium ion batteries (LIBs) have been regarded as the most widely used power sources for many aspects such as portable electronics and electric vehicles, due to the demands for clean energy for the past few decades. However, the lithium resources are limited and non-uniformly distributed globally, so the cost of materials increased by the demands of LIBs. Thus the alternatives should be considered for substituting LIBs. Among many kinds of batteries, sodium ion batteries (NIBs) have been gaining great attention by the natural abundance and low cost of sodium resources. Na share similar chemical properties with Li, that the fundamental principle of the LIBs and NIBs are identical. The enormous previous researches of LIBs provide great guidance for NIB anode materials. However, it still needs to explore appropriate anode materials for NIBs. Therefore, a major focus has been to search for high capacity anode materials that will satisfy increasing demands. The overview of NIBs are introduced in chapter 1 including the benefits of NIBs. In addition, electrode materials currently being investigated as cathode and anode materials in NIBs are also introduced. The structure of the cathode can be divided into three categories while anode, although having a variety of different structures, all generally follow one of three reaction mechanisms. In chapter 2, the electrochemical properties of heteroatom-doped graphene is discussed. In this chapter the heteroatom-doped graphene with high doping levels and disordered structures were prepared through a simple and economical thermal process. These solvothermal-derived graphene showed excellent performance as an anode material for SIBs. It exhibited a high reversible capacity of 380 mAh g-1 after 300 cycles at 100 mA g-1, excellent rate performance 217 mAh g-1 at 3200 mA g-1 and superior cycling performance at 2.0 A g-1 during 1000 cycles with negligible capacity fade. The main reasons for the excellent cycle performance of SG are likely due to the large interlayer distances, highly disordered structures and greater number of active sites for Na ion storage than others. In addition, by doping with sulfur, as well as lowering the oxygen content, the capacity and cycle performance were significantly enhanced. In chapter 3, novel tin (II) sulfide/carbon (SnS/C) composites were prepared, through a ball-milling method, as anode materials for sodium ion batteries. Their electrochemical performance has been significantly improved when com-pared to bare SnS, especially in cycling stability and rate capabilities. SnS/C composites exhibit excellent capacity retention, at various current rates, and deliver capacities as high as 400 mAh g-1 even at the high current density of 800 mA g-1 (2C). Ex-situ transmission electron microscopy, X-ray diffraction and operando X-ray absorption near edge structure studies have been performed in order to better understand the reaction mechanism of SnS/C composites. Keywords: sodium ion batteries, anodes, sulfur doped graphene, tin sulfides, reaction mechanism Student number: 2014-30254 Abstract i List of Figure v Chapter 1. Introduction 1 1.1 Lithium ion batteries 1 1.1.1 General introduction 1 1.1.3 Anode materials in lithium ion batteries 4 1.2.1 General introduction 10 1.2.2 Cathode materials in sodium ion battery 15 1.2.3 Anode materials in sodium ion battery 18 Chapter 2. Solvothermal-Derived S-doped Graphene as an Anode Material for Sodium-Ion Batteries 31 2.1. Introduction 31 2.2. Experimental section 33 2.2.1. Reagents 33 2.2.2. Synthesis method of S-SG 33 2.2.3. Synthesis method of pristine SG 34 2.2.4. Materials characterization 34 2.2.5 Electrochemical characterization of materials 35 2.3.2 Electrochemical performance of of S-SG and SG 50 2.4. Conclusions 64 2.5. References 65 Chapter 3. SnS/C Nanocomposites as Sodium Ion Battery Anode Materials with high Capacity and superior Rate Capability 68 3.1 Introduction 68 3.2. Experimental section 70 3.2.1 Preparation method of tin (II) sulfide/carbon composites 70 3.2.2 Materials characterization 70 3.2.3 Electrochemical Characterization 70 3.3 Results and discussion 72 3.3.1 Materials characterization of bare SnS and SnS/C nanocomposites 72 3.3.2 Electrochemical properties of bare SnS and SnS/C nanocomposites 76 3.3.3 Reaction mechanism of bare SnS and SnS/C nanocomposites 88 3.4 Conclusions 98 3.5 References 99 국문 초록 (Abstract in Korean).……………………………………103   Docto

Improved Performance of Mn3O4 Nanoparticles on Nitrogen-doped Graphene for Lithium Ion Battery Anodes

학위논문 (석사)-- 서울대학교 대학원 : 화학생물공학부, 2014. 2. 성영은.Lithium ion batteries (LIBs) have been widely applied as major power sources for electronic devices. To utilize lithium ion battery to electric vehicles, plenty of research is going on. Developing new electrode materials with high specific capacity for excellent lithium ion storage properties is very desirable. In this research, a simple hydrothermal method for the growth of Mn3O4 nanoparticles onto nitrogen-doped graphene (N-doped graphene) for high-performance lithium ion battery (LIB) anodes is introduced. Hydrazine plays a fundamental role in the formation of such nanostructures as it can act both as a reducing agent and as a nitrogen source. In the synthesized composite, highly crystalline Mn3O4 nanoparticles with average sizes of 20–50 nm are homogeneously dispersed on both sides of the N-doped graphene. The nitrogen content in the doped graphene is confirmed by elemental analyzer, and 2 wt% of the sample is found to be composed of nitrogen element. The as-prepared Mn3O4/N-doped graphene composites exhibit remarkable electrochemical performance, including high reversible specific capacity, outstanding cycling stability, and excellent rate capability (approximately 400 mA h g-1 at 2.0 A g-1) when used as the anode material for LIBs. The improvement in the electrochemical properties of the material can be attributed to graphene, which acts as both an electron conductor and a volume buffer layer, and nitrogen doping allows for fast electron and ion transfer by decreasing the energy barrier. This type of metal oxide/N-doped graphene composites can be promising candidates for high-performance anode materials for LIBs.Chapter 1. Introduction .................................................... 1 Chapter 2. Background ....................................................... 6 2.1 The mechanisms of LIBs ....................................................... 6 2.2 Components in LIBs ..............................................................8 2.2.1 Cathode ........................................................................8 2.2.2 Anode .........................................................................12 2.2.3 Electrolyte ..................................................................18 Chapter 3. Experimental .................................................20 3.1 Preparation of materials ......................................................20 3.2 Preparation of composite electrode .....................................21 3.3 Preparation of half cell ........................................................22 3.4 Characterization ..................................................................22 3.5 Electrochemical measurement ............................................23 Chapter 4 Results and discussion ...................................24 4.1 The analysis of powder .......................................................24 4.2 The electrochemical analysis ...............................................37 Chapter 5 Conclusions .....................................................50 References .........................................................................51 국문초록.............................................................................58Maste

췌장암 관련 신규 유전자의 발굴

Dept. of Medical Science/석사[한글] 췌장암은 1년 생존율이 10%에 불과하고 5년 생존율이 1%에 불과하여 인체에 발생하는 다양한 암들 중에서 예후가 가장 불량한 암중 하나이다. 서양에서는 암환자 사망률의 4위를 차지하고 한국에서도 최근 10년간 2배의 발생율 급증을 보이고 있다. 암세포의 경우 세포의 유전자 중 일부에 이상이 발생하여 이들 유전자의 산물인 단백질의 특성이 바뀌고, 그 결과로 세포 성장 조절에 이상이 발생한다. 따라서 암의 원인, 성장 및 전이에 관여하는 주된 요인의 분자 생물학적 특성을 규명하는 것이 중요한데, EST를 통한 신규 유전자 발굴을 통해 새로운 표적 분자를 발견할 가능성이 높을 것으로 생각된다. 본 연구는 췌장암 환자들의 유전자 발현패턴을 microarray 분석자료를 바탕으로, 췌장암에서 높게 발현되는 미지의 유전자 조각(EST)을 선별, cloning하여 췌장암 관련 신규 유전자를 규명하는 것이다. 본 연구에서 수술로 절제된 정상조직과 암조직의 RNA와 Affymetrix GeneChip을 이용하여 oligonucleotide microarray를 시행하였다. Chip data를 MatLab 통계프로그램으로 p-value와 fold change 등을 계산하여, 유전자 발현 양상을 분석하였다. 532개의 EST 조각(p-value 1.2) 이 정상 췌장조직에 비해 췌장암에서 과발현 되였다. 이들 중 p-value가 0.01 이하이고, fold change가 2.0 이상, 6.0 이하인 EST 조각 101개를 선별하였다. 101개 EST 조각을 Affymetrix, Human Genome DataBase 와 NCBI database 의 검증을 거쳐, 현재까지 기능이 알려지지 않은 64개 EST를 최종 선택하였고, 이들의 full length cDNA cloning을 실시하였다. Human Placenta cDNA Library로부터 각각의 gene-specific primer을 이용하여 타겟 EST 클론을 찾았고, 시퀀싱하였다. 그 결과, 전체 cDNA length가 6875bp 되는, AT-32라 명명한 신규 유전자를 확보하였다. 여러 가지 public database와 생물정보학을 이용하여 후보 유전자 AT-32의 염기서열 분석 및 단백질 서열을 분석하여 그들의 예상 기능을 일차적으로 도출하였다. AT-32는 1161bp (from bp 72 to bp 1232) 크기의 open reading frame 을 갖고 있으며, 이는 387-amino acid 의 예상 단백질을 coding한다.특히 췌장암의 경우, 현재까지 이들 질환을 조기에 진단하거나 효과적으로 치료하기 위한 뚜렷한 방법이 없기 때문에 보다 효과적인 조기진단법 및 치료법의 개발이 요망되고 있다. 본 연구에서 발굴한 신규 유전자 AT-32는 향후 다양한 기능 관련 연구가 진행될 것이고, 종양발생과 발전의 mechanism의 규명에 중요한 정보를 제공할 것이라 생각된다. 또한 췌장암 조기진단 marker나 췌장암 치료 target 개발에도 정보를 제공할 것이다. [영문] To identify novel genes highly expressed in pancreatic cancer, we used bioinformatic analysis of expressed sequence tags (ESTs). ESTs are an excellent source of data for such studies using bioinformatic approaches because of the rich libraries and tremendous amount of data now available in the public domain. Sixty four ESTs were selected depending on fold change and p-value that were highly expressed in pancreatic cancer tissues compared to normal tissues from analysis of Affymetrix Human Genome U133 GeneChip set. Eight ESTs were tried to construct their full-length cDNAs using full-length cDNA library. As a result, one EST was successful for cloning, and then was sequenced to construct the full-length cDNA. In this way, a putative novel gene AT-32 highly expressed in pancreatic cancer was identified. The cDNA sequence was searched in several public databases to predict the open reading frame (ORF) and possible protein related information.In this study, in silico screening and experimental expression analysis were combined to select ESTs that are highly expressed in pancreatic cancer and identified one putative novel gene through cloning EST.ope