Mixture of ionic liquid and sulfone electrolyte for silicon anodes of lithium-ion batteries

碩士 === 國立中央大學 === 材料科學與工程研究所 === 107 === At the first part, we find FSI-based ionic liquid has better electrochemical stability than conventional organic electrolyte in silicon anode; and it is non-flammable, but FSI- anion will corrode aluminum foil, so it can not be used for the cathode material w...

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Bibliographic Details
Main Authors: En-Sin-Ye, 葉恩信
Other Authors: 張仍奎
Format: Others
Language:zh-TW
Published: 2019
Online Access:http://ndltd.ncl.edu.tw/handle/q49mh5
Description
Summary:碩士 === 國立中央大學 === 材料科學與工程研究所 === 107 === At the first part, we find FSI-based ionic liquid has better electrochemical stability than conventional organic electrolyte in silicon anode; and it is non-flammable, but FSI- anion will corrode aluminum foil, so it can not be used for the cathode material which working potential is over than 4.0 V. The sulfone-based electrolyte has a very wide electrochemical window, but the formation of the SEI layer in the anode need the help of LiFSI salt. Moreover, even if the LiFSI concentration is increased, the silicon electrode still cannot be stabilized. Second part, we add sulfone solvent into FSI-based ionic liquids and increase the concentration of lithium salts. The result effectively improved the performance of ionic liquid in LiNi0.8Mn0.1Co0.1O2 cathode materials. In the LiFSI series mixed electrolyte, the high-current retention and the specific capacity of 3 m LiFSI/50% EiPS is 56% @ 2 A/g, 1277 mAh/g for silicon anode, on the other hand, the performance for cathode is 66%, 134 mAh/g. The retention of 200 cycle life for the anode at the rate of 1 A/g exhibits 63.1%, which is higher than pure FSI-based ionic liquid that only have 48.6% high rate retention. Due to the corrosion issue and costing down, in the last part, the lithium salt is replaced with a larger anoin, LiTFSI. Compared to LiFSI hybrid system, LiTFSI exhibits lower ionic conductivity, higher viscosity, and exhibits the best performance of the salt at a concentration of 2 m in this salt. 2 m LiTFSI/50% EiPS exhibits a high-rate retention of 59% and a high-rate capacitance of 121 mAh/g on the cathode, and a high-rate retention of 45%, high-rate capacity of 951 mAh/g on the anode. Although the performance of this part is lower than previous, the coulombic efficiency in different current rate is slightly higher than that using LiFSI salt.