Characterization of Electrolytic V2O5 coating on Pt for Lithium-Ion Battery

Abstract

本實驗是在VOSO4水溶液中利用電化學方法，以定電流方式直接陰極沉積五氧化二釩(V2O5)薄膜於鉑基材上，並利用TGA/DSC、SEM、XRD、恆定位儀，分析沉積膜的物理特性及電化學特性。 由陰極化極化曲線實驗推論在VOSO4水溶液中陰極反應可分為三階段： O2+4H++4e-→2H2O (1) 2H++2e-→H2 (2) VO(H2O)22++2e-→VO(OH)2+2H2 (3) 在TaTb的燒結條件下，可發現V2O5薄膜具有良好的結晶性與均一性，其粒徑尺寸大約為0.25μm。 在CV電性與充放電實驗中，可看出V2O5在2.8V與3.8V區間 具有良好的可逆性，分別在3.4V與3.2V顯示出放電平台，其放電電容量約為140mAh/g. 經由XRD分析在此區間進行充放電晶格常數並無改變。 當鋰離子嵌入V2O5晶格時產生相變化(α→ε→δ')分別從x=0至0.2和0.6，δ'是一個擁有斜方晶系結構的相，晶格常數a=11.4388 Å b=8.8374 Å c=3.5793 Å，以前並末被發現。Cathodic V2O5 deposition on Pt was conducted in VOSO4 aqueous solution. Compared with cathodic polarization curves in Na2SO4,H2SO4, and HCl, reaction in VOSO4 could be divided into 3 stage : O2+4H++4e-→2H2O (1) 2H++2e-→H2 (2) VO(H2O)22++2e-→VO(OH)2+H2 (3) A uniform film of V2O5 film was conducted at Ta for tb and its particle sizes was about 0.25μm. CV and charge-discharge tests revealed that the reaction were reversible between 2.8 V and 3.8 V versus Li/Li+ for x≦1 . Two discharging plateaus were found at 3.2 V and 3.4 V, respectively and its discharge capacity is about 140 mAh/g. Results of XRD verified that the lattice parameters of orthorhombicαphase did not change after charge-discharge cycle tests. However, the phase structure changed from α to ε and δ' as x increased from o to 0.2 and to 0.6, respectively. The δ'( a=11.4388 Å b=8.8374 Å c=3.5793 Å )was a new orthorhombic phase with a=11.4388 Å b=8.8374 Å c=3.5793 Å, which was different from δ and not found before.摘要 I Abstract II 總目錄 III 表目錄 V 圖目錄 VI 第一章 緒論 1 1-1 前言 1 1-2 研究動機與目的 1 第二章 文獻回顧 3 2-1二次薄膜電池發展史 3 2-2 五氧化二釩(V2O5)的製備 6 2-2-1 脈衝雷射沉積(pulsed laser deposition) 7 2-2-2 磁控濺鍍((magnetron sputtering) 7 2-2-3 溶膠-凝膠技術(sol-gel techniques) 7 2-2-4 電化學陽極合成(electrochemically anodic synthesis) 8 2-2-4-1 陽極氧化法 8 2-2-4-2 電化學陽極合成法 8 2-3 五氧化二釩(V2O5)的結構 9 2-4 五氧化二釩性質 9 2-4-1 導電度 9 2-4-2 循環伏安(cyclic voltammogram)與充放電(charge-discharge) 10 2-4-3鋰離子嵌入產生之相變化 11 2-4-4 臨場X光繞射技術觀察 11 第三章 實驗方法 13 3-1試片的前處理 13 3-2陰極極化 13 3-3電解沉積 13 3-4熱分析TGA&DSC 13 3-5燒結 14 3-6 X光繞射(XRD)分析 14 3-6-1 V2O5之結構分析 14 3-6-2 進行充放電之結構變化分析 14 3-7掃瞄式電子顯微鏡(SEM)表面形態觀察 14 3-8原子力顯微鏡(AFM)表面形態觀察 15 3-9循環伏安分析(CV) 15 3-10電池充放電測試 15 第四章 結果與討論 16 4-1 陰極極化 16 4-2 熱分析(TGA&DSC) 17 4-3 X光繞射XRD分析 18 4-4 掃瞄式電子顯微鏡(SEM)與原子力顯微鏡(AFM)分析 18 4-5 膜厚的計算 18 4-6 V2O5理論電容量的計算 18 4-7 電化學量測分析 19 4-7-1 鍍膜在Tb tb條件之循環伏安(CV)、充放電、XRD測試 19 4-7-2 鍍膜在Ta tb條件之循環伏安(CV)、充放電、XRD測試 20 4-7-2-1 電位在2.00 V與3.80 V間 20 4-7-3 鍍膜在Ta tb條件各階段充放電XRD比較 22 4-7-4 充放電速率對電容量影響與循環效率之評估 23 第五章 結論 25 參考資料 26 Table 1-1 Comparison of deposition rates and thickness for balding, 2 electrolytic and vapor methods. 2 Table 2-1 Comparison of electrical conductivity at room temperature 10 and c (V4+/V+5+V4+) value. 10 Table 4-1 Reactive stages of cathodic polarization curve 16 Table 4-2 Lattice parameters of V2O5 film at annealed Tb for tb and 20 after charge-discharge between 2.80 V and 3.80 V 20 Table 4-3 Lattice parameters of V2O5 film at annealed Ta for tb and 21 after charge-discharge between 2.00 V and 3.80 V 21 Table 4-4 Lattice parameters of V2O5 film at annealed Ta for tb and 22 after charge-discharge between 2.80 V and 3.80 V. 22 Table 4-5 Comparison of lattice parameters at various discharge stages 23 Table 4-6 Comparison of lattice parameters at various charge stages 23 Figure 1-1 Schematic cross-section of a thin film lithium battery[2] 30 Figure 2-1 Perspective representation of the V2O5 structure assuming square-pyramidal V5+ coordination. The V-O bond distances are show on the right[27] 31 Figure 2-2 An idealized representation of the structure of V2O5 based on octahedral coordination.[27] 31 Figure 2-3 Cyclic voltammetric curves of V2O5 in PC/EC/DME 1M LiAsF6 between 3.8V and 2.8V (---) and between 3.8V and 2 V (－)[29] 32 Figure 2-4 First discharge (D0) charge (C1)；second (D1) and third (D2) discharge of an Li/V2O5 battery.[29] 32 Figure 2-5 Cyclic voltammetric curves of a SGC-V2O5 film in 1M 33 LiClO4 solution in propylene carbonate(ν=10Vs-1)[31] 33 Figure 2-6 Influence of current density on the discharge curve of SGC-V2O5 films at 20℃[31] 33 Figure 2-7 Influence of the current density on the discharge curve of 34 SGC-V2O5 film at 50℃[31] 34 Figure 2-8 Stability diagram for δ- and ε-LixV2O5[27] 34 Figure 2-9 Phase diagram of LixV2O5 for electrochemical cycling between 3.8 and 2 V for first discharge；(D0) charge；(C1) and fourth (D5) discharges.[29] 35 Figure 2-10 Evolution of the (001) reflection upon intercalation from 35 x=0.0 (top) to x=0.8 (bottom).[34] 35 Figure 2-11 Evolution of (301) and reflection upon intercalation from x=0.0 (top) to x=0.8 (bottom).[34] 36 Figure 2-12 In-situ XRD patterns of o-V2O5 at various states of 36 discharge.[33] 36 Figure 3-1 The equipment of experiment 37 Figure 3-2 Sintering flow chart of V2O5 38 Figure 3-3 The configuration of three-electrode cell 39 Figure 3-4 The configuration of two-electrode cell 39 Figure 4-1 Cathodic polarization curve of ClVOSO4 solution 40 Figure 4-2 Cathodic polarization of different solution 41 Figure 4-3 TGA and DSC diagrams of gel of deposited film[35] 42 Figure 4-4 XRD Diagrams of V2O5 coated specimens (a) annealed at Ta℃for tb (b) annealed at Tb℃for tb 43 Figure 4-5 SEM observations of V2O5 coated film annealed at Ta ℃for tb 44 Figure 4-6 SEM observations of V2O5 coated film annealed at Tb ℃for tb 45 Figure 4-7 AFM observations of V2O5 coated film annealed at Ta ℃for tb 46 Figure 4-8 Cyclic votlammograms of V2O5 film annealed at Tb ℃for tb at scanning rate of 0.05 mV/sec for 2 cycles. 47 Figure 4-9 First charge-discharge curves of V2O5 film annealed at Tb ℃for tb at 10μA. 48 Figure 4-10 XRD Diagrams of V2O5 coated film (a) annealed at Tb℃for tb (b) after the first charge-discharge cycle test between 2.80 V and 3.80 V 49 Figure 4-11 Cyclic votlammograms of V2O5 film annealed at Ta℃ for tb at scanning rate of 0.05 mV/sec for 2 cycles. 50 Figure 4-12 First charge-discharge curves of V2O5 film annealed at Ta for tb at 10μA. 51 Figure 4-13 XRD Diagrams of V2O5 coated film (a) at annealed Ta℃for tb (b) after the first charge-discharge cycle test between 2.00 V and 3.80 V 52 Figure 4-14 Cyclic voltammogram of V2O5 film annealed at Ta ℃for tb at scanning rate of 0.5mV /sec for 20 cycles 53 Figure 4-15 Cyclic voltammogram of V2O5 film annealed at Ta℃ for tb at scanning rate of 0.05mV /sec for 2 cycles 54 Figure 4-16 First charge-discharge curves of V2O5 film annealed at Ta℃ for tb at 10μA. 55 Figure 4-17 XRD Diagrams of V2O5 coated film (a) annealed at Ta℃for tb (b) after the first charge-discharge cycle test between 2.80 V and 3.80 V 56 Figure 4-18 E. VS. LixV2O5 diagrams of first charge-discharge curves of V2O5 film annealed at Ta℃for tb at 10μA. 57 Figure4-19 XRD diagrams of LixV2O5 for x=0,0.14,0.43,0.65,0.93,repectivily during discharge 58 Figure4-20 XRD diagrams of LixV2O5 for x=0.67,0.47,0.31,0.08,0,repectivity during charge. 59 Figure 4-21 Lattice parameters of V2O5 versus x in LixV2O5 for (A) discharge and (B) charge 60 Figure 4-22 Discharge curves at various discharge rates. 61 Figure 4-23 Cyclic efficiency at various charge-discharge rates. 6