在二次電池和其他離子化裝置中，奈米複合材料的高分子電解質是一種有效的處理方式，除了增加離子導電度、機械穩定性之外，與電極 (例如: 鋰金屬)之間能保持一良好的介面接觸。奈米二氧化鈦具有尺寸小且表面積大的優點 (鹼修飾過的奈米管二氧化鈦 > 奈米粒二氧化鈦)，能使得離子的傳導增加，同時藉著其具有的強Lewis base特性，不僅促進鹽類解離，同時間接與高分子鏈形成暫時性的物理交聯。 針對本研究所利用的二氧化鈦，使用XRD、TEM、XPS、TGA…鑑定所製備的奈米粒 ( Nano-particle ) 或經過鹼修飾的奈米管( Nano-tube ) 二氧化鈦。在PVDF / LiPF6 / TiO2複合的電解質系統中，藉著XPS光譜分析比較鋰離子與奈米粒/管二氧化鈦作用力的不同，探討其導電行為與導電度的改變。在SEM的表面型態探討上，鋰鹽含量的改變以及添加不同尺寸大小的二氧化鈦，均會影響PVDF結晶粒子的改變。當添加有機溶劑或電解質液時，由於離子轉移空間增加障礙能減少使得導電度皆提高。 經由DSC、FT-IR及AC-impedance研究顯示，奈米管二氧化鈦能有效的藉由交聯結構的產生，使的高分子重組作用降低，非結晶區域增加，提高離子導電度。此外亦探討當鋰離子結合在二氧化鈦表面形成錯合物之後，增加了鹽類的結離外，在奈米管表面的離子會藉著連續的hopping 方式來取代鄰近空的結合位置( Hole )來達到離子轉移。 Nano composite polymer electrolytes are one of the effective approaches to enhance ionic conductivity, mechanical stability and better interfacial contact with electrodes ( i.e., Li metal ) in secondary batteries and other ionic devices. Ion conduction enhancement is higher when filler nano particles in smaller dimensions with high specific surface area. The strong Lewis base characteristics of nano inorganic oxide particles facilitate salt disassociation and physical cross-link with polymer chain improves the mechanical strength. The formation of TiO2 nano-particle and nano-tube were confirmed with XRD、TEM、XPS、TGA. The XPS results are consistent with structure that the fluorine atoms in PVDF and oxygen atoms in inorganic oxide TiO2 are coordinate with the dissociated Li+ ions through acid-base reactions. As evident from SEM micrograph, contents of lithium salt and TiO2 with different scale will affect polymer crystallinity. When polymer electrolyte is swollen with organic solvent, the overall ion conductivity would be governed by the dissociation of salt, and ion mobility governed by the polymer and the plasticizer dielectric constant and the viscosity. On a separate studies of PEO, nano-tube TiO2 surface groups provide cross-link centers for the PEO segments and also for the anions, which reduces the polymer reorganization with higher degree of amorphous in composite electrolytes. Nano-tube TiO2 surface groups also facilitated more complete salt dissociation. Conduction path is established on the nano-tube TiO2 where the charge transport achieved by replacing the nearby vacancy ( the “hole” ) hopping in sequential manner.
