Electrochemical analysis of surface modified LiV3O8 cathode for a lithium metal battery with a lithium powder anode
- 주제(키워드) 리튬이차전지 , 리튬바나듐 산화물 양극 , 리튬분말 음극
- 발행기관 고려대학교 대학원
- 지도교수 윤우영
- 발행년도 2015
- 학위수여년월 2015. 2
- 학위구분 박사
- 학과 일반대학원 신소재공학과
- 세부전공 신소재공학전공 리튬이차전지
- 원문페이지 127 p
- 실제URI http://www.dcollection.net/handler/korea/000000057568
- 본문언어 영어
- 제출원본 000045827932
초록/요약
Rechargeable batteries, in particular Li secondary batteries, are widely used as power sources for electronic devices. Li metal is the most attractive candidate for anode materials, because it has the lowest weight and highest negative standard electrode potential, resulting in the highest theoretical specific energy density. However, to fully understand the effect of Li powder on Li metal batteries, the effect of Li powder size needs to be investigated quantitatively. Reducing the size of Li powder particles should increase the surface area, thus lowering the effective current density of the electrode. To enable the direct use of lithium metal in anodes, non-lithiated cathodes are required. One potential material for fabricating non-lithiated cathodes is lithium trivanadate (Li1+xV3O8). However, LVO also has several disadvantages. To solved problem, Researchers have suggested coated and composited LVO electrodes as possible methods for preventing these disadvantages. The main goal of this study was to determine the electrochemical properties of a battery that used a Diamond like carbon and chromium coated and PEDOT:PSS (as a conducting polymer) coated nonlithiated cathode and a Li-powder anode of optimal size. Consequentially, In case of Chromium coating, The initial discharge capacity of a cell with an LPE and a Cr-coated LVO cell was 252 mAh g−1 at a 0.2 C-rate and that of a cell with an LPE and an uncoated LVO cathode was 223 mAh g−1. After the 50th cycle, Cr-coated LVO cell exhibited higher capacity retention (about 89%) than LPE/bare LVO cell (about 78%). In case of Diamond like carbon coating, The initial discharge capacity of the DLC-coated LVO cell was 238 mAh g−1 at a C-rate of 0.5, while that of a LPE/bare LVO cell was 236 mAh g−1. Also, PEDOT:PSS coated, PEDOT:PSS-coated LVO cell displayed greater discharge capacity than the bare LVO cell. and, after 50 charge cycles, this value decreased by 10%. Changes in the surface morphology of the coated LVO cathode were observed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The change in the electrical conductivity of the cell was measured using the impedance analysis. The electrochemical properties of the cells were also evaluated based on the differential capacity curve, voltage profiles, and capacity versus number of cycles.
more목차
1. Introduction 1
2. Literature Review 6
1) Structure of lithium trivanadate 6
2) Electrochemical properties of lithium trivanadate 9
3) Lithium metal secondary battery 13
4) Impedance element 15
5) Equivalent Circuits 18
6) Motivation 20
3. Experimental Procedure 22
1) Effect of lithium powder size 22
1-1) Preparation of lithium powder 22
1-2) Preparation of cathode 26
1-3) Cell assembly and measurements 27
2) Diamond-Like-Carbon-Coated LiV3O8 Cathode 30
2-1) Preparation of the DLC-coated LVO cathode 30
2-2) Cell assembly and measurement 32
3) Chromium Coated LiV3O8 Cathode 34
3-1) Preparation of Cr Coated LVO Electrode 34
3-2) Cell assembly and measurements 35
4) PEDOT:PSS-coated LiV3O8 secondary cells 36
4-1) Preparation of PEDOT:PSS-coated cathode 36
4-2) Cell assembly and measurements 37
5) Cell's electrolyte 38
6) EIS measurement condition 39
7) Materials 40
4. Results and Discussion 41
1) Effect of lithium powder size 41
1-1) Particle size and electrode surface morphology 41
1-2) Estimating reactive surface area of electrodes 44
1-3) Influence of solid electrolyte interface 47
1-4) Symmetric LPE/LPE cells 49
1-5) LPE/LVO cells 52
1-6) Cycling stability of LPE/LVO cells 55
2) Diamond-Like-Carbon-Coated LiV3O8 Cathode 57
2-1) Results of the electron probe microanalysis of the DLC-coated LVO electrode 57
2-2) Raman spectra of the DLC-coated LVO electrode 59
2-3) SEM imaging and EDX analysis of the DLC-coated LVO electrode 61
2-4) Cycle performance of Li foil/bare-LVO, LPE/bare-LVO, and LPE/DLC-coated LVO cells 66
2-5) Electrochemical analysis of the LPE/bare-LVO and the LPE/DLC-coated LVO cells 69
3) Chromium Coated LiV3O8 Cathode 74
3-1) Characterization of Cr-Coated LVO Electrode 74
3-2) Impedance Analysis of Cells with LPE/Bare LVO Electrodes and LPE/Cr-Coated LVO Electrodes 84
3-3) Electrochemical behavior of Cells with LPE/Bare LVO Electrodes and LPE/Cr-Coated LVO Electrodes 87
3-4) differential capacity plot 86
4) PEDOT:PSS-coated LiV3O8 secondary cells 94
4-1) Characterization of PEDOT:PSS-coated LVO cathode
94
4-2) Electrochemical behavior of LPE/bare and LPE/PEDOT:PSS-coated LVO cells 99
4-3) \Impedance analysis for LPE/bare and LPE/PEDOT:PSS-coated LVO cells 104
5. Conclusions 108
6. referances 112
