Lithium-ion conduction in elastomeric binder in Li-ion batteries |
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Authors: | Mayumi Kaneko Masanobu Nakayama Masataka Wakihara |
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Institution: | (1) Zeon Corporation, R&D Center, 1-2-1, Yako, Kawasaki, Kanagawa 210-9507, Japan;(2) Department of Applied Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japan |
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Abstract: | This paper describes two kinds of elastomeric binders which are styrene–butadiene (ST–BD) copolymer and 2-ethylhexyl acrylate–acrylonitrile
(2EHA–AN) copolymer for electrode materials of rechargeable Li-ion batteries. These elastomeric binders were swollen by electrolyte
solution (EC/DEC=1/2, 1 M LiPF6), and 2EHA–AN copolymer retained larger amount of electrolyte solution than ST–BD copolymer. The Li-ionic conduction behavior
was investigated for both copolymer films swollen by electrolyte solution. The Li-ion conductivity of ST–BD copolymer was
9.45 × 10−8 S·cm−1 and that of 2EHA–AN copolymer was 1.25 × 10−5 S·cm−1 at room temperature, and the corresponding amounts of activation energy were 0.31 and 0.26 eV, respectively. Because the
observed activation energy in elastomeric binder was different from that in the bulk of electrolyte solution (0.09 eV), Li-ion
conduction of the bulk of elastomeric binder swollen by electrolyte was affected by the polymer structure of binders. Electrochemical
performance of cathode material, LiCoO2, was investigated with three kinds of binders: ST–BD copolymer, 2EHA–AN copolymer, and poly(vinylidene fluoride). The initial
charge–discharge capacity of the LiCoO2 electrode with 2EHA–AN copolymer showed highest capacity, suggesting that Li+-ion conduction inside of the elastomeric binder contributes to the enhancement of charging and discharging capacity. This
result indicates that elastomeric binder with sufficient Li-ionic conductivity can be an attractive candidate for improving
cathode of lithium-ion battery. |
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