鋰離子電池是廣泛使用在電子產品當中的電池，是重要的儲能裝置之一，在發展過程中為了改善安全性及耐用性，固態高分子電解質薄膜成為重要的議題之一。固態高分子電解質雖然有許多的優點，但在離子導電性以及與電極之間的界面相容性還是比傳統的液體電解質差，因此致力於提升離子導電度以及界面相容性就成為固態高分子電解質主要發展的目標。 在本實驗中，我們研究一款新穎的固態電解質，利用離子液體[EMIM]+[FSI]-和TiO2奈米顆粒添加到PVDF-HFP及PMMA混摻高分子薄膜中，並且在浸泡離子液體，在電場極化下，橢圓的TiO2奈米顆粒在高分子非結晶區有序地被誘導成順向，有利於離子更直接的在薄膜中傳導。此外高極性的TiO2奈米顆粒可以有效的減弱離子液體的鍵結，釋放出鋰離子提供更高的運輸程度。因此導電度在室溫下到達1.16×10-3 S/cm，在TiO2奈米顆粒添加至3%並且在80oC下導電度可到達4.52×10-3 S/cm。 儘管此在室溫下的導電度還是不高，但是在電場極化產生的有序排列以及來自TiO2奈米顆粒高介電常數下建立了有利於離子液體傳導離子的機制，結合了電極的PvDF/PMMA黏合性能，介面電阻有顯著的下降，發現使用包含離子液體和TiO2顆粒的固態高分子電解質的鋰電池半電池以及磷酸鋰鐵作為陰極，優異且穩定的循環容量在100圈充電和放電循環後在0.2C下仍然保持在140mAh/g。 ;Lithium-ion battery is an important energy storage device, widely used in electronic products. In order to improve the durability and safety, solvent free polymer electrolyte becomes one of the critical components to meet the growing challenge. Although with many promising material advantages, solid polymer electrolyte is far inferior to the liquid electrolyte in ion conductivity. A second drawback is the huge interface resistance between the electrolyte and the electrodes, due to the voids created by incomplete adhesion of the two solids. In this paper, we report a novel solid polymer electrolytes where ionic liquid [EMIM] + [FSI] - and TiO2 nanoparticles were impregnate with polymer blend of PVDF-HFP and PMMA. Under electric field poling, the oval shape TiO2 nano-particles is re-oriented with preferentially ordered arrangement in non-crystalline regions of the polymer blends which served to facilitate fluent ion migration induced in more straight forward manner. Furthermore, high dielectric constant of TiO2 nanoparticles weakens the ionic force within ionic liquid which liberates lithium ion for better transport. Both factors contribute to appreciable increase of ionic conductivity of 1.16 × 10 -3 S / cm at room temperature. In the composite electrolyte samples, ion conductivity of 4.52 × 10 -3 S / cm at 80 °C can be achieved with addition of 3% TiO2 nanoparticles. Although the mobility of the polymer is still not high at room temperature, the ordered arrangement created by E-F poling, and the high dielectric constants originated from the nano particles establishes favorable ionic liquid conduction mechanism. In combination with the superb PVDF/PMMA adhesion properties with the electrodes, the interface resistance is substantially reduced. Lithium battery half cells using the solid polymer electrolytes containing ionic liquids and TiO2 particles, with lithium iron phosphate as cathode, show stable cyclic capacity maintain at 140 mAh / g at 0.2 C discharge rate, after 100 charged and discharge cycle.
