電場排列電極材料於高能鋰離子電池之研究;Using electric field arrange electrode materials for lithium ion batteries

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题名:	電場排列電極材料於高能鋰離子電池之研究;Using electric field arrange electrode materials for lithium ion batteries
作者:	王騰輝;Wang, Teng-Hui
贡献者:	化學學系
关键词:	尖晶石;LTO;Li4Ti5O12;電場誘導;Spinel;LTO;Li4Ti5O12;Electric field induction
日期:	2018-07-03
上传时间:	2018-08-31 11:31:48 (UTC+8)
出版者:	國立中央大學
摘要:	隨著3C產品的使用以及電動車的發展，下一代鋰離子電池需要高的能量密度以及高的功率密度，新的正極材料開發以及負極材料的包覆是近幾年來可以增加能量密度的方式。製造低曲折率(Tortuosity)、高孔洞性(Pores)、高電解液滲透率(Permeability)、低阻抗值(Impedance)的極片將是下一代鋰離子電池開發高能量密度以及高功率密度的新方向。在此篇研究中，使用電場施加極片的方式來製造出低曲折率的極片。當鋰離子在極片中移動的路徑減小，則鋰離子移動的速度增加，電阻抗就會降低，這是一種可以提升功率密度又不會降低能量密度的做法。本研究使用穩定的尖晶石(Spinel)結構鋰鈦氧(Li4Ti5O12 [LTO])來做活性材料，並使用外加電場可以排列無機物的概念誘導陰極漿料(LTO、導電碳黑[Super-P]、黏著劑[PVdF])排列。由表面AFM、表面SEM、還有斷面SEM結果可以表明電極材料形成孔隙結構、低的曲折率、以及高的孔洞半徑。由離子導電度測試可以發現導電度有增加(由1.32×10-3 S cm-1 提升到4.45×10-3 S cm-1 )，交流阻抗測試可以發現電荷轉移阻抗(Charge transfer Resistant [Rct])有降低的情形(由 164.0Ω 降低到 80.1Ω )，這些數據可以表明使用電場施加的極片是可以提升電解液的穿透率以及降低極片的阻抗值。最後，以不同電壓範圍以及不同速率充放電測試並且使用拉格圖(Ragone Plot)來找能量密度以及功率密度的關係圖譜。發現到經過電場施加的極片可以有效提升能量密度以及功率密度。功率密度從545.3增加至660.4 W kg-1，而能量密度從57.1增加至105.3 Wh kg-1。而高的孔隙結構也可以增加極片的比電容數值(specific capacity)而展現擬電容器(Pseudocapacitance)的現象。 ;New materials are being developed for next generation of lithium battery with higher energy and power density. Making low tortuosity and more porosity electrode has the potential to deliver high permeability of electrolytes and lower ion transport resistance. These features are essential to raise the power and energy density for next generation lithium ion batteries. In present work, we report a novel approach by architecting lower tortuosity electrode structure with the use of electric field poling technique. The straightforward ion transfer path established fluent electrolyte permeation and faster ion transport with the voids in electrode, and maintains high power density without sacrificing energy density. This approach is demonstrated with the stable spinel structure Li4Ti5O12 (LTO) as an active material. The external electric force induced instantaneous dipole interaction which served to arrange the anode components (carbon black, binder) containing LTO with preferentially ordered alignment. Surface AFM, surface SEM and cross-section SEM results shows the electrode developed a pore structure with lower degree of tortuosity, and larger pore size. Ion conductivity is found to be increased (from 1.32×10-3 to 4.45×10-3 S/cm) and AC-impedance analysis shows the Rct, is reduced (from 164.0 to 80.1Ω). This confirms that E-F poling has developed benign electrode pore structure for better electrolyte permeation which shows lower ion transport resistance. Finally, different voltage range and variable charge-discharge rate test revealed the relationship of power and energy density with Ragone Plot which suggested that the electric field-induced inorganic alignment is able to elevated both power and energy densities. On average, power density is increased from 545.3 to 660.4 W/kg, and energy density from 57.1 to 105.3 Wh/kg. The larger pore structure also allows for more complete access to active electrode materials, thus improves the specific capacitance, as well.
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