- Email: [email protected]
Novel Na3Zr2Si2PO12–polymer hybrid composites with high ionic conductivity for solid-state ionic devices
Journal Pre-proofs Novel Na3Zr2Si2PO12-polymer hybrid composites with high ionic conductivity for solid-state ionic devices M. Dinachandra Singh, Anshuman Dalvi, D.M. Phase PII: DOI: Reference:
S0167-577X(19)31654-4 https://doi.org/10.1016/j.matlet.2019.127022 MLBLUE 127022
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
4 October 2019 5 November 2019 13 November 2019
Please cite this article as: M. Dinachandra Singh, A. Dalvi, D.M. Phase, Novel Na3Zr2Si2PO12-polymer hybrid composites with high ionic conductivity for solid-state ionic devices, Materials Letters (2019), doi: https://doi.org/ 10.1016/j.matlet.2019.127022
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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.
© 2019 Published by Elsevier B.V.
Novel Na3Zr2Si2PO12-polymer hybrid composites with high ionic conductivity for solidstate ionic devices M. Dinachandra Singha, Anshuman Dalvia*, D M Phaseb aDepartment bUGC-DAE
of Physics, BITS Pilani-Pilani Campus (RJ-333031), India Consortium for Scientific Research, Indore 452017, India
*Corresponding author email: [email protected]
Abstract Incorporation of PEO based Na+ ion polymer electrolyte in Na3Zr2Si2PO12 (NZSP) NASICON results into novel hybrid composite formation with high ionic conductivity of ~ 10-4 Ω-1cm-1 at room temperature. Thus compositions 63NZSP-37(PEO1-xNaIx) for x = 0.03-0.13 have been prepared. The ionic transport mechanism investigated using impedance and X-ray absorption near edge structure spectroscopy suggests decoupling of Na+ ions from the polymer matrix, and significant role of NASICON crystallites in providing pathways for ionic conduction. Compositions with large salt content exhibit reversible conductivity-temperature cycles at least upto 100oC. The best conducting composite (x = 0.13) exhibits appreciable electrochemical stability window of 4.64 V vs Na/Na+. Keywords: Nanocomposites; Na3Zr2Si2PO12; XANES; Electrical properties; LSV; CV
1. Introduction Sodium ion conductivity in solid polymer electrolytes (SPEs) has been a subject of interest for last three decades. Due to similar chemical insertion properties with those of Li+ ions, Na+ ionSPEs have been widely studied as an alternative for all-solid-state devices [1][2]. However, these SPEs reported so far of the type PEO-NaX (where X = ClO4-, I-) exhibit inadequate ionic 1
conductivity of the order of 10-6-10-8 Ω-1cm-1 [3]. Recently dispersion of fast ionic ceramic crystallites in polymer matrix has generated significant interest. Therefore various systems have been revisited with NASICON [4][5] and garnet [6][7] structured crystallites dispersed in polymer matrix. Mostly NASICONs have been dispersed in the polymer matrix with a restricted content up to 30-40%. In our recent work [8] on hybrid polymer NASICON composites, a maximum ionic conductivity of 2 x 10-5 Ω-1cm-1 was reported for 63 wt% of NaTi2(PO4)3 in PEO-NaI. In the present work, we report a novel fast ionic system based on Na+ ion salt, PEO and a NASICON viz. Na3Zr2Si2PO12. In such a composite, the polymer electrolyte occupies space between the NASICON grains. Thus the electrical and electrochemical properties of the composites have been examined in view of their applications in energy storage devices. A correlation between the conductivity and hybrid structure synthesized using “polymer in ceramic” approach has been attempted. 2. Experimental The Na3Zr2Si2PO12 crystallites were prepared by solid state reaction route as describe elsewhere [9]. Their nanoparticles [6] of approximate size of ~ 30 nm were prepared using planetary ball mill (Fritsch Pulverisette P6). The hybrid polymer composites of 63NZSP-37(PEO1-xNaIx) where x = 0.03, 0.7, 0.11 and 0.13, were prepared by mixing these nanocrystallites in an appropriate weight ratio with Na+ ion rich polymer matrix prepared by solution casting. The obtained hybrid polymer-NASICON slurry was dried in vacuum, pelletized and annealed at 40oC prior to characterization.
2
X-ray diffraction, FESEM, XANES, impedance spectroscopy, DSC and cyclic voltammetry were performed to investigate structural and electrical properties of the composites. 3. Results and Discussion Nyquist plots and corresponding fitted spectrum using combination of resistances (R) and constant phase elements (CPE) for composite with x = 0.03 (inset) and 0.13 are shown in Fig.1a. As evident, the plots exhibit dissimilar nature for these low and high salt content samples. For composite with x = 0.03, a single depressed semicircle is observed followed by a spike at lower frequencies. No separate contribution of the phases is evident here, thus R1 is attributed to total resistance of composite. However, for sample with x = 0.13, the semicircle appears to be shifted away from origin. This readily suggests two different electrical transport mechanisms represented by two models (inset). Resistance R1, thus, can be attributed to bulk transport (Rb) whereas, R2 to a relatively poor conducting region, may be the grain-grain interface, where polymer’s presence is likely. Thus, R2 may be assigned to polymer-grain boundary interfacial properties (RPGB). Similarly, Nyquist plots for the composites with x = 0.07 and 0.11 are given in supplementary figures (Fig.S1a and b). Exact determination of conductivities of different phases (corresponding to Rb and RPGB) and their temperature dependence is rather tricky due to limited frequency range. However, safely the total conductivity is obtained from low frequency intercept with the inclined line. Fig.1b shows the temperature dependence of total conductivity obtained from Nyquist plots. Apparently, for higher salt content the conductivity almost increases linearly with temperature. It exhibits a value of 10-4 Ω-1cm-1 at room temperature for x = 0.13, comparable to bulk conductivity of NZSP [10]. The activation energy for highest conducting composition (0.33eV) is also found to be comparable to NASICONs reported earlier ( 0.34eV) [10]. Such a rise must 3
be attributed to significant alteration of conductivity at grain-grain interface. The interface, where Na+ ion rich polymer is incorporated, possibly facilitates smooth inter-grain transport. On heating at a controlled rate (Fig.1b inset), conductivity shows a rapid increase near polymer melting temperature for x= 0.03. For x = 0.07-0.11, polymer is largely substituted by the salt, therefore PEO melting (Tm) event is not evident in the -T behavior. This may also be due to a significant change in the O/Na ratio from 30:1 (for x= 0.03) to 6:1 (x= 0.13) that leads to a decrease in PEO crystallinity. Thus composites with x = 0.07-0.13 exhibit reproducible Arrhenius behavior of -T cycles at least upto 100o C, also complimented by suppressed melting event in DSC thermograms (Fig.S2; supplementary). Fig.2a shows XRD patterns for Na3Zr2Si2PO12 [9-11] and hybrids. No precipitation is evident even for high salt content samples. Since salt is in dissolved state, a large mobile ion concentration is therefore expected in the polymer existing at inter-grain voids and grain boundaries. To understand the role of polymer matrix in enhancing the ionic conductivity, local structure around ether Oxygen of backbone chains (-CH2-CH2-O-)n was studied using synchrotron radiation. Fig.2b shows normalized XANES spectra for oxygen K-edge. The main edge/white line energy (Eo) values corresponding to 1s→ continuum state (i.e. 1s → 2σ*transition) were obtained from the peak derivative [8]. Such a transition is known to be sensitive to chemical charge state of the element. The inset of Fig.2b also shows an interesting trend of the K-edge energy (Eo) values with salt content. As the salt content increases, the Eo initially shows a jump followed by an apparent saturation. It may be emphasized here that salt addition leads to a gradual decrease in O/Na ratio. Since more Na+ ions are available for oxygen, thus it was also
4
expected [8] that their accumulation about ether oxygen would be leading to gradual increase in Eo. Instead one observes no variation Eo value in a wide composition range. This trend of Eo may be associated with a tendency of decoupling of Na+ ions from the ether oxygen of PEO matrix. Such decoupling may enhance the mobile Na+ ion concentration near the polymer-NZSP interface. Decoupled ions, in presence of electric field may find pathways either from (i)NZSP nanocrystallites, or (ii) from the surface states of NZSP through polymer-NZSP interface. FESEM images of composites with x = 0.03 and 0.13 are shown in Fig. 2c and d. As apparent for lower salt content, polymer is apparently seen surrounding the nano-grains of NZSP. For large salt content when the polymer is in small amount, grains are more closely packed. In both the cases composites appear homogeneous. Fig.S3 (supplementary) shows EDS image that suggests an even distribution of various elements viz. Na, C, Si, P and Zr with no agglomeration or phase separation. Ionic transport number for the composite with x = 0.13, obtained using Hebb-Wagner polarization was found to be 0.94 (Fig.S4, supplementary). The CV studies on symmetric cells of type SS|63NZSP_37(PEO0.87NaI0.13)|SS are also shown in the inset of Fig.3 that exhibits electrochemical stability of ~ ± 2V. Further, the performance considerably
improves
for
a
configuration
with
reversible
electrodes,
viz.
Na|63NZSP_37(PEO0.87NaI0.13)|Na. For this, LSV of the cell is shown in Fig.3 and noticeably, composite electrolyte possesses an electrochemical stability window of 4.64V. Conclusions High ionic conductivity at room temperature of 10-4 Ω-1cm-1 in a novel hybrid solid polymerNASICON composite has been achieved for a composition 63 wt% of Na3Zr2Si2PO12. The hybrid composites were found to be predominately ionic in nature. Most conducting composition 5
(x = 0.13) found to be exhibiting least activation energy, comparable to that of NZSP bulk. The decoupling of Na+ ions from polymer matrix possibly play important role in conductivity enhancement. Moreover, the composite electrolyte exhibits an electrochemical stability window of 4.64 V vs Na/Na+. This composite could be a potential electrolyte for sodium based all-solidstate devices. Acknowledgements This work is supported by UGC-DAE-CSR, Indore, India under project (CSRIC-BL-52/CRS169/2016-17/833) and DST-SERB grant (EMR/2015/000275), Govt. of India. MDS would like to thank CSIR-JRF for research fellowship and Prof. Mukul Gupta, Scientist F, UGC-DAE-CSR Indore, India for fruitful discussions. The authors are grateful to RRCAT, Indore, India for SXAS characterization at Indus II beamline-I. Special thanks are also due to Mr Rakesh Kumar Sah, Scientific Assistant D, RRCAT, Indore for technical support. References [1]
J.S. Moreno, M. Armand, M.B. Berman, S.G. Greenbaum, B. Scrosati, S. Panero, Composite PEOn:NaTFSI polymer electrolyte: Preparation, thermal and electrochemical characterization, J. Power Sources. 248 (2014) 695–702. doi:10.1016/j.jpowsour.2013.09.137.
[2]
C. Zhao, L. Liu, X. Qi, Y. Lu, F. Wu, J. Zhao, Y. Yu, Y.-S. Hu, L. Chen, Solid-State Sodium Batteries, Adv. Energy Mater. (2018) 1703012. doi:10.1002/aenm.201703012.
[3]
Y. Wang, S. Song, C. Xu, N. Hu, J. Molenda, L. Lu, Development of solid-state electrolytes for sodium-ion battery–A short review, Nano Mater. Sci. 1 (2019) 91–100. doi:10.1016/j.nanoms.2019.02.007.
[4]
Z. Zhang, K. Xu, X. Rong, Y.S. Hu, H. Li, X. Huang, L. Chen, Na3.4Zr1.8Mg0.2Si2PO12 filled poly(ethylene oxide)/Na(CF3SO2)2N as flexible composite polymer electrolyte for solid-state sodium batteries, J. Power Sources. 372 (2017) 270–275. doi:10.1016/j.jpowsour.2017.10.083.
[5]
Z. Zhang, Q. Zhang, C. Ren, F. Luo, Q. Ma, Y.S. Hu, Z. Zhou, H. Li, X. Huang, L. Chen, A ceramic/polymer composite solid electrolyte for sodium batteries, J. Mater. Chem. A. 4 (2016) 15823–15828. doi:10.1039/c6ta07590h. 6
[6]
L. Chen, Y. Li, S.P. Li, L.Z. Fan, C.W. Nan, J.B. Goodenough, PEO/garnet composite electrolytes for solid-state lithium batteries: From “ceramic-in-polymer” to “polymer-inceramic,” Nano Energy. 46 (2018) 176–184. doi:10.1016/j.nanoen.2017.12.037.
[7]
F. Chen, D. Yang, W. Zha, B. Zhu, Y. Zhang, J. Li, Y. Gu, Q. Shen, L. Zhang, D.R. Sadoway, Solid polymer electrolytes incorporating cubic Li7La3Zr2O12 for all-solid-state lithium rechargeable batteries, Electrochim. Acta. 258 (2017) 1106-1114. doi:10.1016/j.electacta.2017.11.164.
[8]
M. D. Singh, A. Dalvi, D.M. Phase, Electrical Transport in PEO-NaI-NASICON nanocomposites: An Assessment using Impedance and X-Ray Absorption Spectroscopy, Mater. Res. Bull. 118 (2019) 110485. doi:10.1016/j.materresbull.2019.05.010.
[9]
A.G. Jolley, G. Cohn, G.T. Hitz, E.D. Wachsman, Improving the ionic conductivity of NASICON through aliovalent cation substitution of Na3Zr2Si2PO12, Ionics (Kiel). 21 (2015) 3031–3038. doi:10.1007/s11581-015-1498-8.
[10]
M. Samiee, B. Radhakrishnan, Z. Rice, Z. Deng, Y.S. Meng, S.P. Ong, J. Luo, Divalentdoped Na3Zr2Si2PO12 natrium superionic conductor: Improving the ionic conductivity via simultaneously optimizing the phase and chemistry of the primary and secondary phases, J. Power Sources. 347 (2017) 229-237. doi:10.1016/j.jpowsour.2017.02.042.
[11]
D. Chen, F. Luo, W. Zhou, D. Zhu, Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics, Mater. Lett. 221 (2018) 172-174. doi:10.1016/j.matlet.2018.03.128.
Figure captions Fig.1 (a) Nyquist plots for composites with x = 0.13 and 0.03 (inset). Dotted lines represent corresponding fitted models. (b) Temperature dependence of total conductivity obtained from Nyquist plots for all composites. Inset: -T cycles (1kHz) at a heating rate of 1oC-min-1 to observe effect of polymer melting on electrical transport. Fig.2 (a) XRD patterns for composites with x = 0.03-0.13. (b) Normalized XANES spectra processed using ATHENA software. Inset: O-K edge energy (Eo) variation with salt addition. (c) and (d) FESEM images for composite with x = 0.03 and 0.13, respectively. Fig.3 LSV scans for composite with x = 0.13 with different cell configurations at a scan rate of 10mV-s-1. Inset: CV scan (10mV-s-1) for composite with x = 0.13 with cell configuration of SS|Sample|SS.
7
Declaration of interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
8
Highlights
Na3Zr2Si2PO12 (NZSP) - polymer nanocomposite hybrids have been synthesized. High ionic conductivity of 10-4 Ω-1cm-1 and stability window of 4.64V have been reported. Conductivity mechanism has been proposed. Composites exhibit reversible σ-T cycles at least upto 100oC.
9
S0167-577X(19)31654-4 https://doi.org/10.1016/j.matlet.2019.127022 MLBLUE 127022
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
4 October 2019 5 November 2019 13 November 2019
Please cite this article as: M. Dinachandra Singh, A. Dalvi, D.M. Phase, Novel Na3Zr2Si2PO12-polymer hybrid composites with high ionic conductivity for solid-state ionic devices, Materials Letters (2019), doi: https://doi.org/ 10.1016/j.matlet.2019.127022
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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.
© 2019 Published by Elsevier B.V.
Novel Na3Zr2Si2PO12-polymer hybrid composites with high ionic conductivity for solidstate ionic devices M. Dinachandra Singha, Anshuman Dalvia*, D M Phaseb aDepartment bUGC-DAE
of Physics, BITS Pilani-Pilani Campus (RJ-333031), India Consortium for Scientific Research, Indore 452017, India
*Corresponding author email: [email protected]
Abstract Incorporation of PEO based Na+ ion polymer electrolyte in Na3Zr2Si2PO12 (NZSP) NASICON results into novel hybrid composite formation with high ionic conductivity of ~ 10-4 Ω-1cm-1 at room temperature. Thus compositions 63NZSP-37(PEO1-xNaIx) for x = 0.03-0.13 have been prepared. The ionic transport mechanism investigated using impedance and X-ray absorption near edge structure spectroscopy suggests decoupling of Na+ ions from the polymer matrix, and significant role of NASICON crystallites in providing pathways for ionic conduction. Compositions with large salt content exhibit reversible conductivity-temperature cycles at least upto 100oC. The best conducting composite (x = 0.13) exhibits appreciable electrochemical stability window of 4.64 V vs Na/Na+. Keywords: Nanocomposites; Na3Zr2Si2PO12; XANES; Electrical properties; LSV; CV
1. Introduction Sodium ion conductivity in solid polymer electrolytes (SPEs) has been a subject of interest for last three decades. Due to similar chemical insertion properties with those of Li+ ions, Na+ ionSPEs have been widely studied as an alternative for all-solid-state devices [1][2]. However, these SPEs reported so far of the type PEO-NaX (where X = ClO4-, I-) exhibit inadequate ionic 1
conductivity of the order of 10-6-10-8 Ω-1cm-1 [3]. Recently dispersion of fast ionic ceramic crystallites in polymer matrix has generated significant interest. Therefore various systems have been revisited with NASICON [4][5] and garnet [6][7] structured crystallites dispersed in polymer matrix. Mostly NASICONs have been dispersed in the polymer matrix with a restricted content up to 30-40%. In our recent work [8] on hybrid polymer NASICON composites, a maximum ionic conductivity of 2 x 10-5 Ω-1cm-1 was reported for 63 wt% of NaTi2(PO4)3 in PEO-NaI. In the present work, we report a novel fast ionic system based on Na+ ion salt, PEO and a NASICON viz. Na3Zr2Si2PO12. In such a composite, the polymer electrolyte occupies space between the NASICON grains. Thus the electrical and electrochemical properties of the composites have been examined in view of their applications in energy storage devices. A correlation between the conductivity and hybrid structure synthesized using “polymer in ceramic” approach has been attempted. 2. Experimental The Na3Zr2Si2PO12 crystallites were prepared by solid state reaction route as describe elsewhere [9]. Their nanoparticles [6] of approximate size of ~ 30 nm were prepared using planetary ball mill (Fritsch Pulverisette P6). The hybrid polymer composites of 63NZSP-37(PEO1-xNaIx) where x = 0.03, 0.7, 0.11 and 0.13, were prepared by mixing these nanocrystallites in an appropriate weight ratio with Na+ ion rich polymer matrix prepared by solution casting. The obtained hybrid polymer-NASICON slurry was dried in vacuum, pelletized and annealed at 40oC prior to characterization.
2
X-ray diffraction, FESEM, XANES, impedance spectroscopy, DSC and cyclic voltammetry were performed to investigate structural and electrical properties of the composites. 3. Results and Discussion Nyquist plots and corresponding fitted spectrum using combination of resistances (R) and constant phase elements (CPE) for composite with x = 0.03 (inset) and 0.13 are shown in Fig.1a. As evident, the plots exhibit dissimilar nature for these low and high salt content samples. For composite with x = 0.03, a single depressed semicircle is observed followed by a spike at lower frequencies. No separate contribution of the phases is evident here, thus R1 is attributed to total resistance of composite. However, for sample with x = 0.13, the semicircle appears to be shifted away from origin. This readily suggests two different electrical transport mechanisms represented by two models (inset). Resistance R1, thus, can be attributed to bulk transport (Rb) whereas, R2 to a relatively poor conducting region, may be the grain-grain interface, where polymer’s presence is likely. Thus, R2 may be assigned to polymer-grain boundary interfacial properties (RPGB). Similarly, Nyquist plots for the composites with x = 0.07 and 0.11 are given in supplementary figures (Fig.S1a and b). Exact determination of conductivities of different phases (corresponding to Rb and RPGB) and their temperature dependence is rather tricky due to limited frequency range. However, safely the total conductivity is obtained from low frequency intercept with the inclined line. Fig.1b shows the temperature dependence of total conductivity obtained from Nyquist plots. Apparently, for higher salt content the conductivity almost increases linearly with temperature. It exhibits a value of 10-4 Ω-1cm-1 at room temperature for x = 0.13, comparable to bulk conductivity of NZSP [10]. The activation energy for highest conducting composition (0.33eV) is also found to be comparable to NASICONs reported earlier ( 0.34eV) [10]. Such a rise must 3
be attributed to significant alteration of conductivity at grain-grain interface. The interface, where Na+ ion rich polymer is incorporated, possibly facilitates smooth inter-grain transport. On heating at a controlled rate (Fig.1b inset), conductivity shows a rapid increase near polymer melting temperature for x= 0.03. For x = 0.07-0.11, polymer is largely substituted by the salt, therefore PEO melting (Tm) event is not evident in the -T behavior. This may also be due to a significant change in the O/Na ratio from 30:1 (for x= 0.03) to 6:1 (x= 0.13) that leads to a decrease in PEO crystallinity. Thus composites with x = 0.07-0.13 exhibit reproducible Arrhenius behavior of -T cycles at least upto 100o C, also complimented by suppressed melting event in DSC thermograms (Fig.S2; supplementary). Fig.2a shows XRD patterns for Na3Zr2Si2PO12 [9-11] and hybrids. No precipitation is evident even for high salt content samples. Since salt is in dissolved state, a large mobile ion concentration is therefore expected in the polymer existing at inter-grain voids and grain boundaries. To understand the role of polymer matrix in enhancing the ionic conductivity, local structure around ether Oxygen of backbone chains (-CH2-CH2-O-)n was studied using synchrotron radiation. Fig.2b shows normalized XANES spectra for oxygen K-edge. The main edge/white line energy (Eo) values corresponding to 1s→ continuum state (i.e. 1s → 2σ*transition) were obtained from the peak derivative [8]. Such a transition is known to be sensitive to chemical charge state of the element. The inset of Fig.2b also shows an interesting trend of the K-edge energy (Eo) values with salt content. As the salt content increases, the Eo initially shows a jump followed by an apparent saturation. It may be emphasized here that salt addition leads to a gradual decrease in O/Na ratio. Since more Na+ ions are available for oxygen, thus it was also
4
expected [8] that their accumulation about ether oxygen would be leading to gradual increase in Eo. Instead one observes no variation Eo value in a wide composition range. This trend of Eo may be associated with a tendency of decoupling of Na+ ions from the ether oxygen of PEO matrix. Such decoupling may enhance the mobile Na+ ion concentration near the polymer-NZSP interface. Decoupled ions, in presence of electric field may find pathways either from (i)NZSP nanocrystallites, or (ii) from the surface states of NZSP through polymer-NZSP interface. FESEM images of composites with x = 0.03 and 0.13 are shown in Fig. 2c and d. As apparent for lower salt content, polymer is apparently seen surrounding the nano-grains of NZSP. For large salt content when the polymer is in small amount, grains are more closely packed. In both the cases composites appear homogeneous. Fig.S3 (supplementary) shows EDS image that suggests an even distribution of various elements viz. Na, C, Si, P and Zr with no agglomeration or phase separation. Ionic transport number for the composite with x = 0.13, obtained using Hebb-Wagner polarization was found to be 0.94 (Fig.S4, supplementary). The CV studies on symmetric cells of type SS|63NZSP_37(PEO0.87NaI0.13)|SS are also shown in the inset of Fig.3 that exhibits electrochemical stability of ~ ± 2V. Further, the performance considerably
improves
for
a
configuration
with
reversible
electrodes,
viz.
Na|63NZSP_37(PEO0.87NaI0.13)|Na. For this, LSV of the cell is shown in Fig.3 and noticeably, composite electrolyte possesses an electrochemical stability window of 4.64V. Conclusions High ionic conductivity at room temperature of 10-4 Ω-1cm-1 in a novel hybrid solid polymerNASICON composite has been achieved for a composition 63 wt% of Na3Zr2Si2PO12. The hybrid composites were found to be predominately ionic in nature. Most conducting composition 5
(x = 0.13) found to be exhibiting least activation energy, comparable to that of NZSP bulk. The decoupling of Na+ ions from polymer matrix possibly play important role in conductivity enhancement. Moreover, the composite electrolyte exhibits an electrochemical stability window of 4.64 V vs Na/Na+. This composite could be a potential electrolyte for sodium based all-solidstate devices. Acknowledgements This work is supported by UGC-DAE-CSR, Indore, India under project (CSRIC-BL-52/CRS169/2016-17/833) and DST-SERB grant (EMR/2015/000275), Govt. of India. MDS would like to thank CSIR-JRF for research fellowship and Prof. Mukul Gupta, Scientist F, UGC-DAE-CSR Indore, India for fruitful discussions. The authors are grateful to RRCAT, Indore, India for SXAS characterization at Indus II beamline-I. Special thanks are also due to Mr Rakesh Kumar Sah, Scientific Assistant D, RRCAT, Indore for technical support. References [1]
J.S. Moreno, M. Armand, M.B. Berman, S.G. Greenbaum, B. Scrosati, S. Panero, Composite PEOn:NaTFSI polymer electrolyte: Preparation, thermal and electrochemical characterization, J. Power Sources. 248 (2014) 695–702. doi:10.1016/j.jpowsour.2013.09.137.
[2]
C. Zhao, L. Liu, X. Qi, Y. Lu, F. Wu, J. Zhao, Y. Yu, Y.-S. Hu, L. Chen, Solid-State Sodium Batteries, Adv. Energy Mater. (2018) 1703012. doi:10.1002/aenm.201703012.
[3]
Y. Wang, S. Song, C. Xu, N. Hu, J. Molenda, L. Lu, Development of solid-state electrolytes for sodium-ion battery–A short review, Nano Mater. Sci. 1 (2019) 91–100. doi:10.1016/j.nanoms.2019.02.007.
[4]
Z. Zhang, K. Xu, X. Rong, Y.S. Hu, H. Li, X. Huang, L. Chen, Na3.4Zr1.8Mg0.2Si2PO12 filled poly(ethylene oxide)/Na(CF3SO2)2N as flexible composite polymer electrolyte for solid-state sodium batteries, J. Power Sources. 372 (2017) 270–275. doi:10.1016/j.jpowsour.2017.10.083.
[5]
Z. Zhang, Q. Zhang, C. Ren, F. Luo, Q. Ma, Y.S. Hu, Z. Zhou, H. Li, X. Huang, L. Chen, A ceramic/polymer composite solid electrolyte for sodium batteries, J. Mater. Chem. A. 4 (2016) 15823–15828. doi:10.1039/c6ta07590h. 6
[6]
L. Chen, Y. Li, S.P. Li, L.Z. Fan, C.W. Nan, J.B. Goodenough, PEO/garnet composite electrolytes for solid-state lithium batteries: From “ceramic-in-polymer” to “polymer-inceramic,” Nano Energy. 46 (2018) 176–184. doi:10.1016/j.nanoen.2017.12.037.
[7]
F. Chen, D. Yang, W. Zha, B. Zhu, Y. Zhang, J. Li, Y. Gu, Q. Shen, L. Zhang, D.R. Sadoway, Solid polymer electrolytes incorporating cubic Li7La3Zr2O12 for all-solid-state lithium rechargeable batteries, Electrochim. Acta. 258 (2017) 1106-1114. doi:10.1016/j.electacta.2017.11.164.
[8]
M. D. Singh, A. Dalvi, D.M. Phase, Electrical Transport in PEO-NaI-NASICON nanocomposites: An Assessment using Impedance and X-Ray Absorption Spectroscopy, Mater. Res. Bull. 118 (2019) 110485. doi:10.1016/j.materresbull.2019.05.010.
[9]
A.G. Jolley, G. Cohn, G.T. Hitz, E.D. Wachsman, Improving the ionic conductivity of NASICON through aliovalent cation substitution of Na3Zr2Si2PO12, Ionics (Kiel). 21 (2015) 3031–3038. doi:10.1007/s11581-015-1498-8.
[10]
M. Samiee, B. Radhakrishnan, Z. Rice, Z. Deng, Y.S. Meng, S.P. Ong, J. Luo, Divalentdoped Na3Zr2Si2PO12 natrium superionic conductor: Improving the ionic conductivity via simultaneously optimizing the phase and chemistry of the primary and secondary phases, J. Power Sources. 347 (2017) 229-237. doi:10.1016/j.jpowsour.2017.02.042.
[11]
D. Chen, F. Luo, W. Zhou, D. Zhu, Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics, Mater. Lett. 221 (2018) 172-174. doi:10.1016/j.matlet.2018.03.128.
Figure captions Fig.1 (a) Nyquist plots for composites with x = 0.13 and 0.03 (inset). Dotted lines represent corresponding fitted models. (b) Temperature dependence of total conductivity obtained from Nyquist plots for all composites. Inset: -T cycles (1kHz) at a heating rate of 1oC-min-1 to observe effect of polymer melting on electrical transport. Fig.2 (a) XRD patterns for composites with x = 0.03-0.13. (b) Normalized XANES spectra processed using ATHENA software. Inset: O-K edge energy (Eo) variation with salt addition. (c) and (d) FESEM images for composite with x = 0.03 and 0.13, respectively. Fig.3 LSV scans for composite with x = 0.13 with different cell configurations at a scan rate of 10mV-s-1. Inset: CV scan (10mV-s-1) for composite with x = 0.13 with cell configuration of SS|Sample|SS.
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Declaration of interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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Highlights
Na3Zr2Si2PO12 (NZSP) - polymer nanocomposite hybrids have been synthesized. High ionic conductivity of 10-4 Ω-1cm-1 and stability window of 4.64V have been reported. Conductivity mechanism has been proposed. Composites exhibit reversible σ-T cycles at least upto 100oC.
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