| dc.description.abstract | 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.
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