- Email: [email protected]
polyvinyl pyrrolidone polymer blend electrolytes
Accepted Manuscript Studies on sodium nitrate based polyethylene oxide / polyvinyl pyrrolidone polymer blend electrolytes K. Sundaramahalingam, N. Nallamuthu, A. Manikandan, D. Vanitha, M. Muthuvinayagam PII:
S0921-4526(18)30485-X
DOI:
10.1016/j.physb.2018.08.002
Reference:
PHYSB 310989
To appear in:
Physica B: Physics of Condensed Matter
Received Date: 8 July 2018 Revised Date:
31 July 2018
Accepted Date: 1 August 2018
Please cite this article as: K. Sundaramahalingam, N. Nallamuthu, A. Manikandan, D. Vanitha, M. Muthuvinayagam, Studies on sodium nitrate based polyethylene oxide / polyvinyl pyrrolidone polymer blend electrolytes, Physica B: Physics of Condensed Matter (2018), doi: 10.1016/j.physb.2018.08.002. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Studies on sodium nitrate based polyethylene oxide / polyvinyl pyrrolidone polymer blend electrolytes
M. Muthuvinayagama,*
Multi-functional Materials Laboratory/ Department of Physics/ International research centre,
SC
a
RI PT
K. Sundaramahalingama, N. Nallamuthua, A. Manikandanb, D. Vanithaa,*,
Kalasalingam Academy of Research and Education - 626 126, Tamil Nadu, India. Department of Chemistry, Bharath Institute of Higher Education and Research (BIHER),
M AN U
b
Bharath University, Chennai 600073, Tamil Nadu, India.
*Corresponding Author: [email protected] (D. Vanitha);
TE D
Phone number: +91 6381456553
[email protected] (M. Muthuvinayagam)
ABSTRACT
EP
Phone number: +91 9942066575
AC C
Solid polymer electrolytes (SPEs) consisting of polyethylene oxide (PEO) /Polyvinyl pyrrolidone (PVP) complexed with sodium nitrate have been synthesized by solution casting technique. Structural studies were carried out using X-ray diffraction (XRD) measurements. The complex formation between the bonding of polymers and the salt was confirmed by Fourier Transform Infrared (FT-IR) spectral data. The ionic conductivity and dielectric response of the SPE systems were studied within the frequency range of 42Hz - 1 MHz at the temperature range of 303-363 K. The maximum ionic conductivity was found to be
1
ACCEPTED MANUSCRIPT 6.157×10-7 S/cm at 303K for PEO (67wt %) /PVP (27wt %)/NaNO3 (6wt%). The dielectric properties were also studied using the complex dielectric permittivity spectra and complex electric modulus spectra of the SPE films. The higher dielectric permittivity was obtained due to accretion of ionic charges at lower frequencies. The surface morphology of the polymer
RI PT
blend electrolyte film complexed with sodium nitrate was studied using Scanning Electron Microscopy (SEM).
Key words: Ionic conductivity; SEM; Polymer blend Electrolyte; XRD; FTIR; Transference
SC
number.
M AN U
1. Introduction
The main objective in polymer research is preparation of higher ionic conducting polymer electrolyte for electrochemical applications. Solid polymer electrolytes are having the best parameters like electrical conductivity, electrochemical stability and energy density. So that,
TE D
it has applied for many devices such as electrochromic devices, fuel cells, electrochemical cells, solid state batteries, super capacitors, fibres, etc. [1-9]. Ionic conducting polymer electrolytes are produced by dissolving ionic salts into high molecular weight polymer
EP
matrix. The ions are using as a charge carrier to enhance the ionic conductivity [10,11].
AC C
Nowadays, the advanced lithium ion battery can be broadly utilized for energy storage framework because of its higher energy density [12-15]. In any case, the staggering expense, lessening of plenitude, environmental impact and
well being confinements worried to lithium materials obstruct their far reaching usage in future battery advancements [16]. In this manner, there is an urgent need for alternate energy storage system to compensate the lithium battery. Sodium (Na) ion batteries (SIB) has caught more consideration since it has lower cost, environmentally friendly, less - toxic and earth abundant materials. 2
ACCEPTED MANUSCRIPT Polyethylene oxide is one of the best polymer matrix in which ionic salts are dissolved to make ion conducting polymer electrolyte. Polyethylene oxide is exhibited as a crystalline polymer by close arrangement of monomers whereas amorphous nature has occurred after mixing salt in it. [17,18]. Sodium fluoride (NaF) salt mixed in Polyethylene
RI PT
oxide (PEO) has provided the ionic conductivity in the range of 10-7 Scm-1.
Polyvinyl-pyrrolidone has good accomplice with PEO to make high amorphous behaviour. Mechanical and thermal properties are enhanced in blend polymer system. The
SC
carbonyl assembly (C = O) in the side chain in PVP enables to form different complexes with metal salts. The C=O bond in PVP is more useful for the complexation of salt in the blend
M AN U
polymer system [19,20].
Polymer blending is one of the most feasible techniques to improve the conductivity of the polymer electrolytes. This technique has more advantages from other techniques because of its controlling physical parameters in the miscibility of blend polymer
TE D
composition [21,22].
In the present work, an attempt is made to prepare and characterize PEO-PVP based blend polymer electrolyte complexed with NaNO3. The structural characterization and dielectric
AC C
EP
properties of the polymer blend electrolytes are discussed.
2. Preparation
The polymers PEO (Mw of 5×106) and PVP (Mw of 3.6×105) and sodium nitrate were procured from Sigma - Aldrich for the utilization as precursor materials. The weight percentages of PEO/PVP/NaNO3 were taken in the ratios (69:29:2, 68:28:4, 67:27:6, 66:26:8, 65:25:10) to prepare the blend polymer electrolytes. The suitable weight percentage of PVP, PEO and NaNO3 were dissolved in water. They were continuously stirred with mechanical blending at room temperature for 24 hours to maintain consistency and miscibility of the 3
ACCEPTED MANUSCRIPT polymers. The formed viscous solutions were transferred to polypropylene dishes and the solvent was permitted to evaporate gradually at room temperature. Four days later, the prepared electrolytes were expelled from petri dish for further analysis. Figure 1 shows the schematic representation for preparation of blend polymer using solution casting method.
RI PT
The XRD pattern of the blend polymer electrolyte was recorded using Bruker make X-Ray diffractometer having CuKα radiation (λ=1.540 Aº) with scanning rate 5º per minute in the range of 10o-80o. FTIR transmittance spectra of the films were traced using
SC
"SHIMADZU IR Tracer 100" spectrometer in the wave number region between 4000 cm-1 and 400 cm-1. The scanning electron microscope instrument made by Carl ZEISS EVO 18
M AN U
was used to analyse the morphological structure of the polymer electrolytes. The impedance measurements were done by HIOKI 3532-50 LCR Hi-tester within the frequency region from 42Hz to 1MHz in the temperature range of 303K-363K.
3.1 XRD Analysis
TE D
3. Result and Discussion
Figure 2, shows the XRD pattern of pure and various composition of sodium nitrate mixed
EP
PEO-PVP blend polymer electrolyte. In the XRD graph, blend Polymer PEO-PVP has two
AC C
crystalline peaks at 18o and 23o, due to involvement of PEO. These peaks are appeared due to strong interaction between the molecules in the polyether side chain of PEO polymer [23, 24]. By increasing the salt concentration, the intensity of the peak decreases up to composition of 6 Wt% of NaNO3 which indicates the increasing amorphous nature in the polymer electrolytes. For the other higher concentrations, the peak intensity is increased and also a new peak is appeared at 28.9o in XRD pattern. The newly observed XRD peak is due to the presence of sodium nitrate which is confirmed by JCPDS (89-0310) data. This is the indication of incomplete distribution of salt in the polymer matrices. The maximum 4
ACCEPTED MANUSCRIPT amorphous nature is obtained for 6wt% sodium nitrate added to the blended system, leading to the maximum conductivity of the polymer electrolyte. The amorphous nature of the blend is improved due to the intermolecular interaction between polymer blend in C–O–C group of PEO and/or C=O group of PVP of polymer blend with salt. It is more helpful to reduce the
RI PT
continuous chain of the polymer and close packing arrangement. Hence, the crystalline pattern has decreased to improve the amorphous upto the composition of 6wt% sodium nitrate.
M AN U
SC
3.2 FTIR Analysis
The Fourier transform Infrared Spectroscopy is used to identify the functional group in the NaNO3 complexed polymer blend electrolyte. Figure 3 shows the FTIR spectrum of prepared blend polymers in different composition. The obtained broad band between the
TE D
regions of 2913 cm-1 - 2830 cm-1 is due to the asymmetric stretching of CH2 in PEO matrix.. The miscibility of PEO and PVP is confirmed through the appearance of carbonyl groups
EP
(C=O) of PVP and ether oxygen groups(C-O-O) of PEO in the blend polymer matrix [25]. The inclusion of the salt with the polymer blend is observed by means of decrease in
AC C
intensity, broadening, shifting of bands. This may be observed due to the formation of cross link between the cation and oxygen in PEO and PVP matrix. The vibrations modes of functional groups of PEO and PVP are tabulated in Table 1.
3.2.1 Confirmation of PEO The observed IR Peak at 2887 cm-1 is mainly due to the symmetric C-H stretching of PEO. A small band observed at 1334 cm-1 is attributed to the CH2 bending of PEO and the band observed at 940 cm-1 is assigned to the CH2 rocking vibrations of ethylene group of PEO [26, 5
ACCEPTED MANUSCRIPT 27]. A band observed at 838 cm-1 is due to the CH2 rocking in PVP and with some C–O stretching in PEO. A small band at 1450 cm-1 is assigned to the CH2 scissoring mode of PEO [28]
RI PT
3.2.2 PVP Confirmation
The vibrational band appeared at 2878 cm-1 is attributed to the CH stretching of PVP matrix. The band at 1272 cm-1 is assigned to the CH2 twisting or wagging of both PEO and PVP
SC
chains. A band at 1097 cm-1 present in the spectrum is appeared due to the stretching
M AN U
vibrations of C-N in PVP matrix [29, 30].
3.2.3 Complexation of PEO/PVP/NaNO3
A band observed at 1142 cm-1 is due to the complexation of ether oxygen with Na+ ion due to the addition of salt. The C-H bending vibration in both PEO and PVP appears at 1483cm-1
TE D
which is shifted to 1464 cm-1, indicates the inclusion of the salt with PEO/PVP [31]. A band appears at 1360 cm-1 is attributed to asymmetric vibration of C–H in CH2 group, which indicates the amorphous nature of PEO. There are some slight changes in the peaks due to the
AC C
EP
increase in the concentration of sodium nitrate salt in blend polymer matrices.
S0921-4526(18)30485-X
DOI:
10.1016/j.physb.2018.08.002
Reference:
PHYSB 310989
To appear in:
Physica B: Physics of Condensed Matter
Received Date: 8 July 2018 Revised Date:
31 July 2018
Accepted Date: 1 August 2018
Please cite this article as: K. Sundaramahalingam, N. Nallamuthu, A. Manikandan, D. Vanitha, M. Muthuvinayagam, Studies on sodium nitrate based polyethylene oxide / polyvinyl pyrrolidone polymer blend electrolytes, Physica B: Physics of Condensed Matter (2018), doi: 10.1016/j.physb.2018.08.002. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Studies on sodium nitrate based polyethylene oxide / polyvinyl pyrrolidone polymer blend electrolytes
M. Muthuvinayagama,*
Multi-functional Materials Laboratory/ Department of Physics/ International research centre,
SC
a
RI PT
K. Sundaramahalingama, N. Nallamuthua, A. Manikandanb, D. Vanithaa,*,
Kalasalingam Academy of Research and Education - 626 126, Tamil Nadu, India. Department of Chemistry, Bharath Institute of Higher Education and Research (BIHER),
M AN U
b
Bharath University, Chennai 600073, Tamil Nadu, India.
*Corresponding Author: [email protected] (D. Vanitha);
TE D
Phone number: +91 6381456553
[email protected] (M. Muthuvinayagam)
ABSTRACT
EP
Phone number: +91 9942066575
AC C
Solid polymer electrolytes (SPEs) consisting of polyethylene oxide (PEO) /Polyvinyl pyrrolidone (PVP) complexed with sodium nitrate have been synthesized by solution casting technique. Structural studies were carried out using X-ray diffraction (XRD) measurements. The complex formation between the bonding of polymers and the salt was confirmed by Fourier Transform Infrared (FT-IR) spectral data. The ionic conductivity and dielectric response of the SPE systems were studied within the frequency range of 42Hz - 1 MHz at the temperature range of 303-363 K. The maximum ionic conductivity was found to be
1
ACCEPTED MANUSCRIPT 6.157×10-7 S/cm at 303K for PEO (67wt %) /PVP (27wt %)/NaNO3 (6wt%). The dielectric properties were also studied using the complex dielectric permittivity spectra and complex electric modulus spectra of the SPE films. The higher dielectric permittivity was obtained due to accretion of ionic charges at lower frequencies. The surface morphology of the polymer
RI PT
blend electrolyte film complexed with sodium nitrate was studied using Scanning Electron Microscopy (SEM).
Key words: Ionic conductivity; SEM; Polymer blend Electrolyte; XRD; FTIR; Transference
SC
number.
M AN U
1. Introduction
The main objective in polymer research is preparation of higher ionic conducting polymer electrolyte for electrochemical applications. Solid polymer electrolytes are having the best parameters like electrical conductivity, electrochemical stability and energy density. So that,
TE D
it has applied for many devices such as electrochromic devices, fuel cells, electrochemical cells, solid state batteries, super capacitors, fibres, etc. [1-9]. Ionic conducting polymer electrolytes are produced by dissolving ionic salts into high molecular weight polymer
EP
matrix. The ions are using as a charge carrier to enhance the ionic conductivity [10,11].
AC C
Nowadays, the advanced lithium ion battery can be broadly utilized for energy storage framework because of its higher energy density [12-15]. In any case, the staggering expense, lessening of plenitude, environmental impact and
well being confinements worried to lithium materials obstruct their far reaching usage in future battery advancements [16]. In this manner, there is an urgent need for alternate energy storage system to compensate the lithium battery. Sodium (Na) ion batteries (SIB) has caught more consideration since it has lower cost, environmentally friendly, less - toxic and earth abundant materials. 2
ACCEPTED MANUSCRIPT Polyethylene oxide is one of the best polymer matrix in which ionic salts are dissolved to make ion conducting polymer electrolyte. Polyethylene oxide is exhibited as a crystalline polymer by close arrangement of monomers whereas amorphous nature has occurred after mixing salt in it. [17,18]. Sodium fluoride (NaF) salt mixed in Polyethylene
RI PT
oxide (PEO) has provided the ionic conductivity in the range of 10-7 Scm-1.
Polyvinyl-pyrrolidone has good accomplice with PEO to make high amorphous behaviour. Mechanical and thermal properties are enhanced in blend polymer system. The
SC
carbonyl assembly (C = O) in the side chain in PVP enables to form different complexes with metal salts. The C=O bond in PVP is more useful for the complexation of salt in the blend
M AN U
polymer system [19,20].
Polymer blending is one of the most feasible techniques to improve the conductivity of the polymer electrolytes. This technique has more advantages from other techniques because of its controlling physical parameters in the miscibility of blend polymer
TE D
composition [21,22].
In the present work, an attempt is made to prepare and characterize PEO-PVP based blend polymer electrolyte complexed with NaNO3. The structural characterization and dielectric
AC C
EP
properties of the polymer blend electrolytes are discussed.
2. Preparation
The polymers PEO (Mw of 5×106) and PVP (Mw of 3.6×105) and sodium nitrate were procured from Sigma - Aldrich for the utilization as precursor materials. The weight percentages of PEO/PVP/NaNO3 were taken in the ratios (69:29:2, 68:28:4, 67:27:6, 66:26:8, 65:25:10) to prepare the blend polymer electrolytes. The suitable weight percentage of PVP, PEO and NaNO3 were dissolved in water. They were continuously stirred with mechanical blending at room temperature for 24 hours to maintain consistency and miscibility of the 3
ACCEPTED MANUSCRIPT polymers. The formed viscous solutions were transferred to polypropylene dishes and the solvent was permitted to evaporate gradually at room temperature. Four days later, the prepared electrolytes were expelled from petri dish for further analysis. Figure 1 shows the schematic representation for preparation of blend polymer using solution casting method.
RI PT
The XRD pattern of the blend polymer electrolyte was recorded using Bruker make X-Ray diffractometer having CuKα radiation (λ=1.540 Aº) with scanning rate 5º per minute in the range of 10o-80o. FTIR transmittance spectra of the films were traced using
SC
"SHIMADZU IR Tracer 100" spectrometer in the wave number region between 4000 cm-1 and 400 cm-1. The scanning electron microscope instrument made by Carl ZEISS EVO 18
M AN U
was used to analyse the morphological structure of the polymer electrolytes. The impedance measurements were done by HIOKI 3532-50 LCR Hi-tester within the frequency region from 42Hz to 1MHz in the temperature range of 303K-363K.
3.1 XRD Analysis
TE D
3. Result and Discussion
Figure 2, shows the XRD pattern of pure and various composition of sodium nitrate mixed
EP
PEO-PVP blend polymer electrolyte. In the XRD graph, blend Polymer PEO-PVP has two
AC C
crystalline peaks at 18o and 23o, due to involvement of PEO. These peaks are appeared due to strong interaction between the molecules in the polyether side chain of PEO polymer [23, 24]. By increasing the salt concentration, the intensity of the peak decreases up to composition of 6 Wt% of NaNO3 which indicates the increasing amorphous nature in the polymer electrolytes. For the other higher concentrations, the peak intensity is increased and also a new peak is appeared at 28.9o in XRD pattern. The newly observed XRD peak is due to the presence of sodium nitrate which is confirmed by JCPDS (89-0310) data. This is the indication of incomplete distribution of salt in the polymer matrices. The maximum 4
ACCEPTED MANUSCRIPT amorphous nature is obtained for 6wt% sodium nitrate added to the blended system, leading to the maximum conductivity of the polymer electrolyte. The amorphous nature of the blend is improved due to the intermolecular interaction between polymer blend in C–O–C group of PEO and/or C=O group of PVP of polymer blend with salt. It is more helpful to reduce the
RI PT
continuous chain of the polymer and close packing arrangement. Hence, the crystalline pattern has decreased to improve the amorphous upto the composition of 6wt% sodium nitrate.
M AN U
SC
3.2 FTIR Analysis
The Fourier transform Infrared Spectroscopy is used to identify the functional group in the NaNO3 complexed polymer blend electrolyte. Figure 3 shows the FTIR spectrum of prepared blend polymers in different composition. The obtained broad band between the
TE D
regions of 2913 cm-1 - 2830 cm-1 is due to the asymmetric stretching of CH2 in PEO matrix.. The miscibility of PEO and PVP is confirmed through the appearance of carbonyl groups
EP
(C=O) of PVP and ether oxygen groups(C-O-O) of PEO in the blend polymer matrix [25]. The inclusion of the salt with the polymer blend is observed by means of decrease in
AC C
intensity, broadening, shifting of bands. This may be observed due to the formation of cross link between the cation and oxygen in PEO and PVP matrix. The vibrations modes of functional groups of PEO and PVP are tabulated in Table 1.
3.2.1 Confirmation of PEO The observed IR Peak at 2887 cm-1 is mainly due to the symmetric C-H stretching of PEO. A small band observed at 1334 cm-1 is attributed to the CH2 bending of PEO and the band observed at 940 cm-1 is assigned to the CH2 rocking vibrations of ethylene group of PEO [26, 5
ACCEPTED MANUSCRIPT 27]. A band observed at 838 cm-1 is due to the CH2 rocking in PVP and with some C–O stretching in PEO. A small band at 1450 cm-1 is assigned to the CH2 scissoring mode of PEO [28]
RI PT
3.2.2 PVP Confirmation
The vibrational band appeared at 2878 cm-1 is attributed to the CH stretching of PVP matrix. The band at 1272 cm-1 is assigned to the CH2 twisting or wagging of both PEO and PVP
SC
chains. A band at 1097 cm-1 present in the spectrum is appeared due to the stretching
M AN U
vibrations of C-N in PVP matrix [29, 30].
3.2.3 Complexation of PEO/PVP/NaNO3
A band observed at 1142 cm-1 is due to the complexation of ether oxygen with Na+ ion due to the addition of salt. The C-H bending vibration in both PEO and PVP appears at 1483cm-1
TE D
which is shifted to 1464 cm-1, indicates the inclusion of the salt with PEO/PVP [31]. A band appears at 1360 cm-1 is attributed to asymmetric vibration of C–H in CH2 group, which indicates the amorphous nature of PEO. There are some slight changes in the peaks due to the
AC C
EP
increase in the concentration of sodium nitrate salt in blend polymer matrices.