Precipitated silica as filler for polymer electrolyte based on poly(acrylonitrile)/sulfolane

Journal of Solid State Electrochemistry, Jul 2014

The aim of the present work was to perform a preliminary study of the physicochemical properties of hybrid organic–inorganic gel electrolytes for Li-ion batteries based on the PAN/TMS - poly(acrylonitrile)/sulfolane - polymeric matrix and surface-modified precipitated silicas. Modifications were done by means of the so-called dry method using silane U-511 3-methacryloxypropyltrimetoxysilane. Scanning electron microscopy (SEM), noninvasive back scattering method (NIBS), specific surface area (BET), the degree of modification of the silica fillers—Fourier-transform infrared spectroscopy (FT-IR), impedance analysis, and charging/discharging were carried out. It is found that the silica fillers were homogeneously dispersed in the polymeric matrix, which enhanced conductivity and electrochemical stability of porous polymer electrolytes. Applicability of the prepared gel electrolytes for the Li-ion technology was estimated on the basis of specific conductivity measurements. It was shown that modification of the silica surface by the silane causes an increase in the gel-specific conductivity by about 2 orders of magnitude as compared to gel with unmodified silica.

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Precipitated silica as filler for polymer electrolyte based on poly(acrylonitrile)/sulfolane

Beata Kurc 0 ) Faculty of Chemical Technology, Pozna University of Technology , 60 965 Pozna, Poland The aim of the present work was to perform a preliminary study of the physicochemical properties of hybrid organic-inorganic gel electrolytes for Li-ion batteries based on the PAN/TMS - poly(acrylonitrile)/sulfolane - polymeric matrix and surface-modified precipitated silicas. Modifications were done by means of the so-called dry method using silane U-511 3-methacryloxypropyltrimetoxysilane. Scanning electron microscopy (SEM), noninvasive back scattering method (NIBS), specific surface area (BET), the degree of modification of the silica fillersFourier-transform infrared spectroscopy (FT-IR), impedance analysis, and charging/ discharging were carried out. It is found that the silica fillers were homogeneously dispersed in the polymeric matrix, which enhanced conductivity and electrochemical stability of porous polymer electrolytes. Applicability of the prepared gel electrolytes for the Li-ion technology was estimated on the basis of specific conductivity measurements. It was shown that modification of the silica surface by the silane causes an increase in the gel-specific conductivity by about 2 orders of magnitude as compared to gel with unmodified silica. - In recent years, much attention has been focused on the development of new inorganicorganic composite materials of prospective use in many areas [14]. Among the inorganic substances, silicon dioxide has become greatly important as an active filler of polymers [57]. Its importance follows from the possibility of controlling its physical properties (by method of synthesis) [8, 9] and chemical properties (by surface modification) [10]. Gel-type electrolytes are regarded as a prospective alternative for traditional liquid electrolytes as far as lithium-ion (Liion) batteries are considered. Gel electrolytes are obtained by placing some amount of liquid plasticizer and/or solvent in a polymer matrix. This idea was first demonstrated in 1975 by Feuillade and Perche [11] who studied the process of plasticizing a polymer (host matrix) with an aprotic solution containing an alkali metal salt. Since then, many different polymers were examined as possible gel matrices, including poly(vinylidene fluoride) (PVdF) [12], poly(acrylonitrile) (PAN) [13, 14], poly(methyl methacrylate) (PMMA) [15], and others. The advantage of gel electrolytes over liquid electrolytes lies in the fact that the risk of leakages in the battery systems containing gels is reduced, since in principle, no free liquid is present in such systems. In addition to that, their specific conductivities are close to those exhibited by purely liquid electrolytes. As was demonstrated in the works of Gozdz and Tarascon [16, 17], some gel electrolytes can have processing properties that enable successful application in large-scale production processes. One of the important findings of Gozdz and Tarascon was that the addition of highly dispersed silica to the PVdFHFP matrix significantly enhances the solvent absorption ability, thus leading to a considerable increase in the measured conductivities. The positive effect of various ceramic particles (also Al2O3, TiO2, and others) on the conductivities of dry polymer electrolytes is also well-documented in the literature [1823]. The key factors responsible for the performance of these ceramic additives are believed to be particle size and surface chemistry. Caillon-Caravanier et al. [24] found that the addition of unmodified silica provided better mechanical stability and improved the solvent absorption ability of membranes, thus enhancing the conductivities. In more recent works, Lee et al. studied the possibility of generating in situ fine silica particles dispersed in the PEO matrix [21] as well as of functionalization of silica surface with glycol chains [25]. Application of crosslinkable silicas modified with certain methacrylate monomers was also reported [26]. Currently, the most widely used separators in lithium-ion batteries are manufactured from polyolefins, predominantly polyethylene (PE) or polypropylene (PP), due to their suitable chemical stability, thickness, and mechanical strength [27]. However, several intrinsic factors such as low porosity, poor thermal stability, and insufficient electrolyte wettability and large difference of polarity between the highly polar liquid electrolyte and the nonpolar polyolefin separator lead to high cell resistance, low rate capability, and even internal short circuits of LIBs [2830], which severely restricts the electrochemical performance of the LIBs, especially affects the safety performance of the LIBs. Therefore, the development of new separators possessing high porosity, good thermal stability, and high ionic conductivity is strongly demanded, especially in the thermal stability which seriously influences the practical application of LIBs. In many studies, the fluorinated polymer poly(vinylidene flu (...truncated)


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Beata Kurc. Precipitated silica as filler for polymer electrolyte based on poly(acrylonitrile)/sulfolane, Journal of Solid State Electrochemistry, 2014, pp. 2035-2046, Volume 18, Issue 7, DOI: 10.1007/s10008-014-2451-x