PVDF/PAN/SiO2 polymer
electrolyte
membrane
prepared
by
combination of phase inversion and chemical reaction method for
lithium ion batteries
Liping Liu，Zhan Wang , Zongkui Zhao，Yujuan Zhao, Fan Li, Libin Yang
Beijing Key Laboratory for Green Catalysis and Separation, Department of Chemistry and
Chemical Engineering, Beijing University of Technology, Beijing 100124 P.R. China
FT-IR spectroscopy
FT-IR spectra of the PVDF/PAN membranes with different blend weight ratios
prepared using combination of phase inversion and chemical reaction method are
presented in Fig. 1. The assignment of FTIR spectra of the samples have been
explained as follows: FT-IR spectrum of the pure PVDF membrane (MPC0 in Fig. 3)
shows characteristic absorption peaks at 1400 cm-1 (CF2 bending), 1116 cm-1 (CF2
stretching) [1], 1653 cm-1 (asymmetrical –CH stretching)，841 cm-1 (CH out-of-plane
deformation and CH2 rocking)，881 cm-1 (CF2 symmetric stretching) [2]. FT-IR spectra
of the PVDF/PAN blend membrane (MPC15, MPC35 in Figure 3) also show bands
corresponding to CF2 vibrations at 1400 cm-1. In addition, FT-IR spectra (MPC15,
MPC35 and MPC100 in Fig. 3) show bands around 2240 cm-1 which correspond to the
symmetrical–CN of PAN, respectively. It is to be noted that the band of –CN
stretching was observed at around 2242 cm-1 in the case of PAN [3]. It can be clearly
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observed that there are no molecular level interactions between the two polymers in
the PVDF/PAN blend membrane as presented in these observations. So these spectral
signatures give a hint for probable phase mixing between PVDF and PAN.
Fig. 1 FT-IR spectra of PVDF/PAN membranes with different weight ratios (100/0,
85/15, 65/35 and 0/100, w/w) prepared using combination of phase inversion and
chemical reaction method.
The role of nanoparticles content in the casting solution
It can be observed that the porosity of PVDF/PAN membranes initially increases
to maximum and then falls back to a lower value with respect to weight ratios of
PVDF/PAN (Fig. 2). A highest porosity can be obtained when 1 wt.% nano-SiO2
added into the casting solution at the weight ratio of PVDF/PAN is 70/30. This can be
explained by the fact that when the concentration of nanoparticles reaches a certain
value，excess SiO2 aggregates may be filled in the holes of the porous membranes and
agglomerated nanoparticles may impede the Li-ion transport [4].
Fig. 2 Impact of weight percentages of nano-SiO2 on the porosity of PVDF/PAN
membranes with different weight ratios.
Fig. 3 Cross-section SEM micrographs different PVDF/PAN/SiO2 membrane samples
prepared by L-S phase inversion or combination of phase inversion and chemical
reaction methods.
References
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SiO2 (Li+) Electrochimica Acta 112:183–190
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