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研究生： 曾怡仁
Tzeng, Yi-Ren
論文名稱： BaZrO3添加對La0.57Li0.3TiO3晶體結構與導電性質的影響
The effect of the addition of BaZrO3 on the structure and the conductivity for La0.57Li0.3TiO3
指導教授： 方冠榮
Fung, K. Z.
學位類別： 碩士
Master
系所名稱： 工學院 - 材料科學及工程學系
Department of Materials Science and Engineering
論文出版年： 2003
畢業學年度： 91
語文別： 中文
論文頁數： 92
中文關鍵詞： 鋰離子導體 、電解質
外文關鍵詞： electrolyte, perovskite
相關次數： 點閱：75  下載：3 
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    • 自1988 年開發出鋰二次電池，由於高能量密度的優勢，成為目前最重要的可攜式電源之一。在資訊化的時代中，所用的電源也往小型化、輕量化及高容量化發展，因而鋰/鋰離子二次電池的輕、薄化成為一重要的發展方向。其中的關鍵則在於電解質材料的研發，於目前市面上所使用的液狀電解質要加以薄化是不可行的；而高分子材料則薄化的程度有限，且室溫導電性質不佳，因此全固態之無機電解質成為各研發單位所積極發展之材料。鑭鋰鈦氧化物在室溫下導電度最高可達10-3S/cm，可惜當以鋰金屬為陽極時，鈦離子會被鋰金屬由正四價還原成正三價（Ti4+變為Ti3+會使試片由鵝黃色變為黑色），且在短時間內整個試片會完全變為n-type導體，失去電解質的功能。本研究則提出以較穩定的BaZrO3化合物和鑭鋰鈦氧化物中導電度最佳之成分La0.57Li0.3□0.13TiO3以不同比例混合，探討其結構、電性及和鋰金屬接觸時抗還原性之變化。本實驗可分為兩大部分：

    1. (BaZrO3)y(La0.57Li0.3TiO3)1-y當0≦y≦0.2時：
    由WDS分析顯示，BaZrO3在La0.57Li0.3□0.13TiO3的溶解度很低，約只有3mol%而已，所以當y=0.05時，具有Ba6-δLa8+2/3δTi18O54結構的第二相析出，且隨著BaZrO3添加量增加Ba6-δLa8+2/3δTi18O54之比例也逐漸增加，當y=0.2 （BaZrO3達20mol%），La0.57Li0.3□0.13TiO3的結構已完全轉變為Ba3.6La8.5Li3.3Ti15.2Zr2.8O54。雖然僅少量的Ba溶入A-site使得[V]．[Li]值下降，但低導電度差的第二相析出，使得導電度隨著BaZrO3的添加而顯著下降，且在y=0.2時，導電度迅速下降且活化能明顯大於La0.57Li0.3□0.13TiO3。抗還原性的部分，也因為Zr部分取代B-site及第二相析出有明顯的提升，當y=0.15（15mol%BaZrO3），其離子導性由純的La0.57Li0.3□0.13TiO3約 10-5S/cm 降低為 10-8S/cm（DC method），而和鋰金屬接觸被還原至完全成為n-type導體的時間由250秒增長為300000秒。

    2. (BaZrO3)y(La0.57Li0.3TiO3)1-y當0.4≦y≦0.9時：
    在此範圍內是以BaZrO3的結構為主相，La0.57Li0.3□0.13TiO3會溶入BaZrO3晶格內，La的溶解度在20mol% La0.57Li0.3□0.13TiO3（y=0.8）達到飽和，以Ba6-δLa8+2/3δTi18O54結構的化合物析出；而當La0.57Li0.3□0.13TiO3含量達40mol%（y=0.6）時，Ti的溶解度達到飽和，多餘的Ti離子以BaTiO3形式析出。電性測試方面：在200℃下，由於PTCR效應的影響，其導電度隨溫度上升而下降；在200℃以上，以離子導性為主，所以導電度隨溫度上升而上升。若選擇導電度最好的成分，y=0.4（40mol%BaZrO3），以外插法來計算，其在室溫下之離子導性約為10-14S/cm，這是因為三價La離子在BaZrO3晶格中A-site溶解度最高僅10mol%，若以理論計算，當Li離子濃度約5mol%而空缺濃度也只有5mol%(in A-site)，且還有其它雜相生成，故離子導電性很低並不適合做為鋰離子電解質。由於Ti在主相鈣鈦礦結構B-site的溶解度約30mol%，大部分仍為Zr離子，惰性的鋯離子可以有效的增加材料的抗還原性，故當0.4≦y≦0.9的試片已不會變色。

    Since 1980s, lithium/lithium ion batteries have emerged as one of the most important power sources for portable electronics due to their high energy density. In order to reduce the weight for portable electronics, the demand for lighter and thinner batteries is increasing. To reduce the battery size to micrometer range, using inorganic solid electrolyte is inevitable. In search for Li ion conducting solid electrolyte, cation-deficient perovskite, La2/3-2xLi3xTiO3 with the addition of lithium ions has received considerable attention due to its high ionic conductivity.
    Although La2/3-xLi3xTiO3 exhibits high ionic conductivity, it is easy to react with Li metal when used as a solid state electrolyte. The objective of this work is to study the effect of BaZrO3 addition on the phase change, conductivity and electrochemical property of La0.57Li0.3TiO3 which exhibits the highest ionic conductivity among La2/3-2xLi3xTiO3 system. This research was divided into two parts based on the chemical composition：

    1. (BaZrO3)y(La0.57Li0.3TiO3)1-y when 0≦y≦0.2
    From the WDS analysis,the solubility of BaZrO3 in La0.57Li0.3TiO3 is about 3mol% and it formed La0.56Li0.32Ba0.03(Ti0.97Zr0.03)O3. When the addition of BaZrO3 reached 5mol%, the second phase, Ba6-δLa8+2/3δTi18O54,was observed. The amount of Ba6-δLa8+2/3δTi18O54 increased with the increasing amount of BaZrO3. When 20mol% of BaZrO3 was added, the perovskite structure completely changed to Ba3.6La8.5Li3.3Ti15.2Zr2.8O54. The low solubility of Ba ion in A-site results in the low value of [V]．[Li] product, and with the insulated second phase increasing, the conductivity is lower and lower. The stability of La0.57Li0.3TiO3 against lithium metal was enhanced by the addition of BaZrO3. Without the addition of BaZrO3, La0.57Li0.3TiO3 became an n-type conduction after reacted with Li metal for 250 sec. After the addition of 15 mol%BaZrO3 into La0.57Li0.3TiO3, pure ionic conductivity decreased to 10-8S/cm. However the full reduction of (BaZrO3)0.15(La0.57Li0.3TiO3)0.85 by Li was observed after reacted with Li metal for 300000 seconds.

    2. (BaZrO3)y(La0.57Li0.3TiO3)1-y when 0.4≦y≦0.9
    In this composition range, the major phase belongs to BaZrO3 perovskite structure. It was found that the solubility of La ion in the A-site of BaZrO3 was about 9.5mol%. The excess La ions resulted in the formation of Ba6-δLa8+2/3δTi18O54. For the conductivity measurement between room temperature and 200℃, the conductivity decreased with the increasing temperature. The suppression of conductivity was due to PTCR effect from La and Ti containing BaZrO3 phase. At temperatures>200℃, the ionic conduction was predominant. The conductivity increased with the increasing temperature in this composition range. Due to the solubility of La, the maximum concentrations of Li ion and vacancy were estimated to be about 5mol%. The ionic conductivity was too low to be an effective lithium ion electrolyte at room temperature. For the samples with composition of (BaZrO3)y(La0.57Li0.3TiO3)1-y,（0.4≦y≦0.9）,no reaction with Li metal was observed.

    中文摘要.....................................................Ⅰ 英文摘要.....................................................Ⅲ 總目錄.......................................................Ⅴ 圖目錄.......................................................Ⅶ 表目錄.......................................................Ⅹ 第一章 緒論..................................................1 第二章 原理及文獻回顧........................................3 2-1 鋰二次電池的簡介.........................................3 2-2 鋰二次電池的電解質材料種類...............................5 2-2-1 有機溶液...............................................5 2-2-2高分子電解質...........................................10 2-2-3 無機固態電解質........................................16 2-3 電解質必需的特性........................................19 2-4 鑭鋰鈦氧化物之缺陷結構..................................19 2-5 離子移動活化能理論......................................20 2-6 離子導電度(歐姆定律)....................................22 2-7 Perovskite 結構特性－Tolerance factor...................22 2-8 鋰金屬為陽極電解質之穩定性..............................23 2-9 具高穩定性陽離子缺陷鋯酸鹽Ba1-3x/2Lax□x/2ZrO3..........26 2-10 La0.57Li0.3□0.13TiO3/ BaZrO3..........................27 第三章、實驗方法及步驟......................................28 3-1 試片的製備..............................................29 3-1-1 La0.57Li0.3□0.13TiO3.................................29 3-1-2 （BaZrO3）y(La0.57Li0.3□0.13TiO3)1-y.................29 3-2 性質測試................................................30 3-2-1 試片之結構性質分析....................................30 3-2-2 導電性質測試..........................................31 3-2-3 與金屬鋰反應測試......................................31 第四章、(BaZrO3)y(La0.57Li0.3TiO3)1-y不同BaZrO3含量下之結構 與電性的關係................................................35 4-1 La0.57Li0.3□0.13TiO3晶體結構分析.......................35 4-1-1 缺陷的產生............................................35 4-1-2 超晶格的產生..........................................36 4-2 BaZrO3之晶體結構分析....................................39 4-3 La0.57Li0.3□0.13TiO3/BaZrO3 之晶體結構分析.............39 4-3-1 (BaZrO3)y(La0.57Li0.3TiO3)1-y當0≦y≦0.2晶體結構之變化............................................................39 4-3-2當0.4≦y≦0.9晶體結構之變化............................45 4-4 結構對導電性質的影響....................................55 4-4-1 La0.57Li0.3□0.13TiO3為主相...........................55 4-4-2 BaZrO3為主相之導電度研究..............................59 4-5 與鋰金屬之接觸反應......................................68 4-5-1 反應機構之探討........................................70 4-6 以鋰金屬為陽極之全固態電池..............................80 第五章、結論................................................85 參考文獻....................................................88 致謝........................................................91

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