A polymer electrolyte based on poly(vinylidene fluoride-hexafluoropylene)/hydroxypropyl methyl cellulose blending for li
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ORIGINAL PAPER
A polymer electrolyte based on poly(vinylidene fluoride-hexafluoropylene)/hydroxypropyl methyl cellulose blending for lithium-ion battery Ying Ran & Zhoulan Yin & Zhiying Ding & Huajun Guo & Jing Yang
Received: 6 August 2012 / Revised: 4 September 2012 / Accepted: 14 September 2012 / Published online: 26 September 2012 # Springer-Verlag Berlin Heidelberg 2012
Abstract A polymer electrolyte based on the blending of poly(vinylidene fluoride-hexafluoropylene) (PVDF-HFP) and hydroxypropyl methyl cellulose (HPMC) was prepared for the first time. The structure and performance of the gel polymer electrolyte were characterized and measured by X-ray diffraction, Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, electrochemical impedance spectroscopy, linear sweep voltammetry, and by a charge/discharge test. The results show that the gel polymer electrolyte has the best performance when PVDF-HFP/ HPMC ratio (w/w) is 4:1. At room temperature, the ionic conductivity can reach 0.38×10−3 S cm−1, the electrochemical stable window is up to 5.0 V (vs. Li/Li+), and the half cell of Li/GPE/LiMn2O4 shows high-discharge-specific capacity and good cycling performance. Keywords PVDF-HFP . HPMC . Gel polymer electrolyte . Lithium-ion battery
Introduction In recent years, gel polymer electrolyte for lithium battery has been well developed. The matrix of polymer electrolytes are mostly related to polyethylene oxide (PEO) [1], polyacrylonitrile [2], polymethyl methacrylate [3, 4], polyvinylidene fluoride (PVDF) [5, 6], or its copolymer poly(vinylidene fluoride-hexafluoropylene) (PVDF-HFP) [7, 8], especially the last one. PVDF-HFP, as the matrix, cannot fully match the requirements of lithium batteries, such as the ionic Y. Ran : Z. Yin (*) : Z. Ding : H. Guo : J. Yang College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083, People’s Republic of China e-mail: [email protected]
conductivity and mechanical properties, so various modifications were proposed. One method is to use mixed matrix. PVDF-HFP and polyethylene terephthalate (PET) were mixed to obtain a composite nonwoven separator [9], in which PVDF-HFP is a pore-size controller and PET is as a mechanical supporter. The potential application to high-voltage and high-power lithium-ion batteries was studied [10]. The other method is to use foaming agent. Salicylic acid [11] and urea [12] were commonly considered as the foaming agent in the foaming process. Excellent performance in optimizing the ionic conductivity and mechanical properties and affinity with the electrolyte can be obtained by both methods. Natural cellulose, the most abundant renewable material, is more environmentally friendly than any industrially synthesized polymer [13] and is used widely because of its lower cost. The cellulose can be used not only as a single matrix for gel polymer electrolytes [14] but also as the one composite of the mixed matrix with PVDF-HFP [15] and PEO [16]. Hydroxypropyl methyl cellulose (HPMC), one of
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