School of Material， Beijing Institute of Technology
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DOI:
10.7502/j.issn.1674-3962.2016.06.08
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Abstract:
As a key component of a battery, electrolyte has a potent influence on its safety, operating temperature, charge/discharge performance and cycle life. Novel electrolytes were prepared based on (NmethoxyethylNmethylpyrrolidinium bis (trifluoromethanesulfonyl)imide, Pyr1,2O1TFSI) and sulfites as cosolvents with lithium difluoro (oxalate) borate (LiODFB) as lithium salt, exhibiting good ion transport, electrode compatibility and wide operating temperature range. The conductivity and Li+ transference number of the LiODFBPyr1,2O1TFSI/ DMS electrolyte was 8.163×10-3 S·cm-1 and 0.28, respectively. The Li/MCMB and Li/ LiFePO4 cells containing this electrolyte had good cycle performance and normal charge curve in the temperature of-40 ℃ to 60 ℃. Moreover, a series of electrolytes for Li/S battery were prepared based on Pyr1,2O1TFSI) with tris(ethylene glycol) dimethyl ether (TEGDME) as cosolvents in different proportions. LiTFSI was used as lithium salt. Li/S cells with LiTFSI(70wt%)Pyr1,2O1TFSI/ (30wt%)TEGDME electrolyte exhibited excellent cycle and rate performance, whose capacity was 1 212.8 mAh·g-1 in the first cycle and 693.5 mAh·g-1 after 100 cycles at current density of 0.1 C, and 827.3 mAh·g-1 with the coulombic efficiency of above 99% at current density of 1 C. In addition, the cells showed good high temperature performance which could operate at 80 ℃ with the initial cycle capacity of 1 005.3 mAh·g-1. A summary of representative electrolyte systems of ionic liquid with organic cosolvent for lithium battery and the corresponding characteristics and properties based on the investigations above and the previous studies are illustrated for the first time. It might be proposed to offer a useful starting point to design the mixed electrolyte in lithium batteries.