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Electrospun polymer membrane activated lith room temperature ionic liquid:   Novel polymer electrolytes for lithium batteries

 

Gouri Cheruvallya, Jae-Kwang Kimb, Jae-Won Choia, Jou-Hyeon Ahna,*, Yong-Jo Shina, Prasanth Raghavana, James Manuela, Ki-Won Kimb, Hyo-Jun Ahnb, Doo Seong Choic, Choong Eui Songc

 

 (a) Department of Chemical and Biological Engineering and ITRC for Energy Storage and Conversion, Gyeongsang National University, 900 Gajwa-dong, Jinju 660-701, Republic of Korea

(b) School of Nano and Advanced Materials Engineering and ITRC for Energy Storage and Conversion, Gyeongsang National University, 900 Gajwa-dong, Jinju 660-701, Republic of Korea

(c) Institute of Basic Science and Department of Chemistry, Sungkyunkwan University,300 Cheoncheon-dong, Jangan-gu, Gyeonggi-do, Suwon City, Republic of Korea

 

 Abstract

A new class of polymer electrolytes (PEs) based on an electrospun polymer membrane incorporating a room-temperature ionic liquid (RTIL) has been prepared and evaluated for suitability in lithium cells. The electrospun poly(vinylidene fluoride-co-hexafluoropropylene) P(VdF-HFP) membrane is activated with a 0.5Msolution of LiTFSI in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI) or a 0.5M solution of LiBF4 in 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4). The resulting PEs have an ionic conductivity of 2.3×10−3 S cm−1 at 25 ºC and anodic stability at >4.5V versus Li+/Li, making them suitable for practical applications in lithium cells. A Li/LiFePO4 cell with a PE based on BMITFSI delivers high discharge capacities when evaluated at 25 ºC at the 0.1C rate (149 mAh g−1) and the 0.5C rate (132 mAh g−1). A very stable cycle performance is also exhibited at these low current densities. The properties decrease at the higher, 1C rate, when operated at 25 ºC. Nevertheless, improved properties are obtained at a moderately elevated temperature of operation, i.e. 40 ºC. This is attributed to enhanced conductivity of the electrolyte and faster reaction kinetics at higher temperatures. At 40 ºC, a reversible capacity of 140 mAh g−1 is obtained at the 1C rate.

 

 Keywords: Polymer electrolyte; Electrospinning; Porous membrane; Room temperature ionic liquid; Lithium batteries

 

 © 2007 Elsevier B.V. All rights reserved.

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