DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | Kwon, Hyuk Sang | - |
dc.contributor.advisor | 권혁상 | - |
dc.contributor.author | Sohn, DongRak | - |
dc.date.accessioned | 2019-08-25T02:40:57Z | - |
dc.date.available | 2019-08-25T02:40:57Z | - |
dc.date.issued | 2018 | - |
dc.identifier.uri | http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=734493&flag=dissertation | en_US |
dc.identifier.uri | http://hdl.handle.net/10203/264958 | - |
dc.description | 학위논문(박사) - 한국과학기술원 : 신소재공학과, 2018.2,[vii, 101 p. :] | - |
dc.description.abstract | Recently, Na-ion batteries have been considered as alternatives for Li-ion batteries due to the crustal abundance and low cost of Na. Therefore, it is necessary to develop electrode materials with high electrochemical performances to commercialize the Na-ion batteries. Especially, development of high-performance cathode materials is necessary which occupy the most part of the manufacturing cost. Cathode materials which have been extensively studied for Na-ion batteries are classified into layered oxides and polyanionic compounds according to their crystal structure. Among the various layered oxides, sodium manganese oxide $(Na_{0.7}MnO_2)$ has been considered potential cathode material due to its high capacity and cost-effective synthetic process. Among the polyanionic compounds, sodium vanadium phosphate (Na₃ V₂(PO₄)₃) have received attention owing to the excellent thermal and structural stability. However, the promising candidates of cathode materials for Na-ion batteries also have problems as follows: (1) sluggish kinetic properties of $Na_{0.7}MnO_2$, (2) poor electronic conductivity and (3) low energy density of Na₃ V₂(PO₄)₃. Herein, three individual studies are performed to solve these problems. In the first part, $Na_{0.7}MnO_2/C$ composite cathode material is fabricated by simple heat treatment for high-power Na-ion batteries. Compared to only 28.07% retention of pristine $Na_{0.7}MnO_2$, 64.55% of the discharge capacity of $Na_{0.7}MnO_2/C$ at a current density of 20 mA $g^-1$ is retained at $400 mA g^{-1}$. The second part covers fabrication of high-power Na₃ V₂(PO₄)₃/C composite cathode materials by synergetic effects of sucrose coating and cellulose template. The improved rate performance of Na₃ V₂(PO₄)₃/C, $77.58 mAh g^{-1}$ at 20-C rate, is acquired from the cost-effective synthetic process with the relatively low amount of carbon, 5 wt.%. In the third chapter, Mg-substituted Na₃ V₂(PO₄)₃/C is synthesized to improve the energy density of Na₃ V₂(PO₄)₃ by utilization of $V^{4+/5+}$ redox reaction. The high-voltage $V^{4+/5+}$ redox reaction in Mg-substituted Na₃ V₂(PO₄)₃/C electrode leads to 3.5% increase of energy density compared with Na₃ V₂(PO₄)₃/C electrode. | - |
dc.language | eng | - |
dc.publisher | 한국과학기술원 | - |
dc.subject | Na-ion batteries▼acathode materials▼a$Na_{0.7}MnO_2$▼aNa₃ V₂(PO₄)₃▼acarbon composite▼ametal-ion substitution▼arate capability▼avoltage control | - |
dc.subject | 나트륨 이온 전지▼a양극소재▼a나트륨 망간 산화물▼a나트륨 바나듐 인산염▼a탄소 복합체▼a금속이온 치환▼a출력 특성▼a작동 전압 조절 | - |
dc.title | Effects of carbon composite and metal-ion substation on the electrochemical performance of cathode materials ($Na_3V_2(PO_4)_3$ and $Na_{0.7}MnO_2$) for Na-ion batteries | - |
dc.title.alternative | 나트륨 이온 전지용 양극소재에 ($Na_3V_2(PO_4)_3$ and $Na_{0.7}MnO_2$) 적용되는 탄소 복합체 및 금속이온 치환이 소재의 전기화학적 특성에 미치는 영향 | - |
dc.type | Thesis(Ph.D) | - |
dc.identifier.CNRN | 325007 | - |
dc.description.department | 한국과학기술원 :신소재공학과, | - |
dc.contributor.alternativeauthor | 손동락 | - |
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