電場誘導有序排列之高導電度複合固態電解質

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题名:	電場誘導有序排列之高導電度複合固態電解質
作者:	王知行;WANG,CHIH-HSING
贡献者:	化學學系
关键词:	高分子;固態電解質;有機-無機複合材料;離子液體;電場排列
日期:	2016-07-22
上传时间:	2016-10-13 12:42:09 (UTC+8)
出版者:	國立中央大學
摘要:	固態高分子電解質具有非揮發性和良好的成膜性，在穿戴式電子產品的市場需求不斷增長的近代，其被認為是可以滿足下一代鋰電池條件的關鍵材料之一。而如何同時具有高離子導電性和適合操作的機械強度是高分子電解質一項技術上的挑戰。　　本研究選取具高介電性與結晶性的高分子材料PVDF-HFP搭配非親水性之離子液BMImTFSI，加入奈米層狀無機添加物──蒙脫土，在電場下製成具高導電度及安全性的高分子複合電解質。粘土（Clay）具有大表面積、高縱橫比的特質，其層間佈滿大量可置換之陽離子。本研究探討以外加電場方式誘導奈米蒙脫土，使其均勻分散在基材中並形成長程有序的排列。藉由有序排列的結構，將電解質中3D的離子傳導路徑轉換為2D，限制離子傳送路徑達到縮短鋰離子在電解質中穿梭的距離，使鋰離子能更順利、迅速的抵達電極的效果，進而增加高分子電解質的導電性。XRD和DSC的量測結果指出，添加蒙脫土可以增加高分子電解質結晶度，而在電場作用下高分子結晶會由α相轉為具高介電性、具鐵電性和極性之β相，其存在可提高鋰鹽解離度及離子導電度。以此材料製作方法能達到具有高離子傳導性(~10-2 S/cm)，搭配LFP應用於鈕扣型鋰電池以0.1C的充放速度可達約135 mAh/g的電容量，並在變速率充放電中能有良好的回覆力。 ;Solid polymer electrolytes is considered as the most critical components for next generation lithium battery to meet the growing demands in mobile electronic power industry. Preserving ionic conductivity and strong film forming property simultaneously is a technical challenge in developing polymer electrolyte for lithium battery. We report in this study a novel polymer electrolyte system by incorporating surface functionalized clay with the PVDF-HFP/IL/Li salt system under applied electric field. The application of electric field has effectively oriented clay layers with increased order parameter which were homogeneously dispersed in the base polymer to form an ordered and aligned nanostructure as confirmed by SEM. This super ionic feature is extremely favorable for delivering high ion conductivity in the solvent free electrolytes where long range ordered inorganic moiety served to establish rapid ion transport. X-ray diffraction and DSC measurements indicated that the α- PVdF crystalline form was decreased by the electric field, replaced with more polar β-crystalline form, which is essential for higher degree of salt dissociation and also contributes to higher ion conductivity. AC impedance spectroscopy revealed that the ionic conductivity of the electrolyte membrane containing MMT attains an order of 10−2 S cm−1 at room temperature and increase with temperature described by Arrhenius relationship. Coin cells assembled with the LFP cathode reversible discharge capacities of 135 mAh g−1 at 0.1C, accompanied with nearly 100% coulombic efficiency.
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