| 摘要: | 本研究中分為三部分探討離子液體電解質運用於鈉離子電池的電化學行為。第一部份使用1-Butylmethylpyrrolidinium bis(trifluoromet hanesulfonyl)imide (BMP-TFSI)離子液體分別溶解含1 M Sodium tetrafluoroborate (NaBF4)、Sodium perchlorate (NaClO4)、Sodium trifluoromethanesulfonimide (NaTFSI)及Sodium hexafluorophosphate (NaPF6)的四種離子液體電解質，並對Na0.44MnO2/Na進行電化學測試。其中NaTFSI/BMP-TFSI 因為有最小的介面阻抗，因此充放電的特性優於其他三者。而此離子液體系統也表現出優異的熱穩定性。測時於75 ℃時Na0.44MnO2/Na的電容值為115 mAh g-1 (0.05 C)十分接近121 mAh g-1的理論值，提升至1 C仍可保有85 %的電容值。
第二部分除了延續使用第一部分的NaClO4/BMP-TFSI離子液體電解質外，另外增加了由N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PMP-FSI)溶解含1 M Sodium(I) bis(fluorosulfonyl)imide ( NFaFSI )及N-Propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PMP-TFSI)溶解含1 M NaTFSI所配製而成的離子液體電解質，其中NaFSI/PMP-FSI有最佳的性質，推測因FSI能在硬碳表面形成較佳SEI幫助鈉離子嵌入結構中。測試於90 ℃時，Hard carbon/Na 有332 mAh g-1的電容值，5 A g-1時則為32 mAh g-1顯示出良好的熱定性。
第三部分則使用Na0.44MnO2及硬碳(Hard Carbon)作為鈉離子電池的正負極材料，在組成Na0.44MnO2- Hard Carbon全電池前，先對Na0.44MnO2/Na Cell及Hard Carbon/Na Cell分別在Ethylene carbonate/diethyl carbonate (EC/DEC) 溶入1 M NaClO4的有機溶劑電解液及第二部分實驗使用的NaFSI/PMP-FSI離子液體電解質進行充放電測試，在離子液體電解液中Na0.44MnO2/Na Cell的電容值為115 mAh g-1，在Hard Carbon/Na Cell的電容值則為280 mAh g-1。Na0.44MnO2/Hard Carbon Full Cell以離子液體作為電解液時，在高速充放電下比起有機電解液具有較高電容值。綜合三部分的研究得知離子液體電解質具有良好熱穩定性及對鈉離子正負極的獨特性，因此研究中使用的離子液體電解質有潛力應用於實際鈉離子電池上。
;In this work, we investigate the electrochemical performance of ionic liquid electrolyte for sodium ion battery. In the first part, 1-Butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMP-TFSI) ionic liquid (IL) with various Na solutes, namely NaBF4, NaClO4, NaTFSI, and NaPF6, is used as an electrolyte for rechargeable Na/Na0.44MnO2 cells. The cell with NaClO4-incorporated IL electrolyte exhibits superior chargeedischarge performance due to it having the lowest solid electrolyte-interface resistance and charge transfer resistance at both the Na and Na0.44MnO2 electrodes. The IL electrolyte shows high thermal stability and is suitable for use at an elevated temperature. At 75 ℃, the measured capacity of Na0.44MnO2 in the IL electrolyte with NaClO4 is as high as 115 mAh g-1 (at 0.05 C), which is close to the theoretical value (121 mAh g-1). Moreover, 85% of this capacity can be retained when the chargeedischarge rate is increased to 1 C. These properties are superior to those of a conventional organic electrolyte.
At second part, Hard carbon/Na cell were investigate in NaClO4/BMP-TFSI ion liquid electrolyte, N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with 1 M sodium bis(fluorosulfonyl)imide (NaFSI) ionic liquid electrolyte and N-Propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PMP-TFSI) with 1 M NaTFSI (NaTFSI) ionic liquid electrolye, respectly. The result shows NaFSI/PMP-FSI has better electrochemical performance than NaClO4/BMP-TFSI and NaTFSI/PMP-TFSI ionic liquid electrolyte due to FSI anion could established a well SEI film to protect electrode surface. At high temperature test (90 ℃), Hard carbon/Na shows a reserveable capacity of 332 mAh g-1(30 mA g-1) and 32 mAh g-1(5 A g-1) while incorporate with NaFSI/PMP-FSI ionic liquid electrolyte. The result indicate NaFSI/PMP-FSI has good thermal properties and suitable for Hard carbon for storage sodium ion.
The third part, Na0.44MnO2 and Hard carbon were used as the cathode and the anode, respectively, in a sodium-ion battery. At first, the NaMnO2/Na half cell and the hard carbon/Na half cell are studied both in conventional ethylene carbonate/diethyl carbonate mixed electrolyte containing 1 M NaClO4 and in. In the ionic liquid electrolyte, the Na0.44MnO2 and Hard carbon electrodes can show reversible capacities of 115 mAh g-1 and 280 mAh g-1, respectively. Based on the obtained electrochemical properties, a Na0.44MnO2/Hard carbon full cell with the ionic liquid electrolyte is constructed. A satisfactory high-rate capability is recognized. Because the high thermal stability, low volatility, and low flammability of the ionic liquid electrolyte, high safety and good durability of the cell are warranted. The proposed cell could have great potential for practical applications. |
