Polymer electrolytes (PEs) were first proposed in the early 1970s [1]. Since then, this class of materials has attracted the attention of many scientists, becoming one of the most prolific research field in solid-state electrochemistry [2, 3]. PEs, when used in Li-ion secondary batteries, are able to overcome many of the disadvantages of classic liquid organic electrolytes, which typically show: a) a high flammability and a high vapor pressure; b) a low thermal, chemical, and electrochemical stability; and c) dendrites formation. Nevertheless, classical PEs show low values of ionic conductivity (σ < 10-6 S cm-1) with respect to the typically requested conductivity values for practical applications. It has been shown that systems based on poly(vinyl alcohol) (PVA) are able to dissolve lithium salts, giving rise to ion conducting materials that present higher conductivity values with respect to any other solid and solvent-free polymer electrolyte [4]. Nonetheless, in classic PEs, the ionic conductivity is mainly attributed to the migration of anionic species. Indeed, in these materials the Li+ transference number is usally very low (< 0.3) [5]. Here, we present a new ion conducting polymer electrolyte based on a Li+ poly(vinyl alkoxide) macromolecular salt. In this material, Li+ ions are provided by PVA alkoxide groups (-RO-Li+) which are obtained by a direct lithiation of hydroxyl groups of pristine polymer. Thus, a PE is obtained with Li+ cations coordinated by the O- ligand functionalities directly bonded to the PVA backbone chains. The lithium assay is determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy. The thermal stability is gauged using High-Resolution Thermo Gravimetric Analysis and the thermal transitions are investigated by means of Modulated Differential Scanning Calorimetry measurements. The structure and the interactions in proposed electrolytes are studied by vibrational spectroscopies both in the mid- and far-infrared and Raman spectroscopy. The interplay between structure and conductivity is investigated by Broadband Electrical Spectroscopy. Insights on the long range charge migration phenomena in these materials are presented. Acknowledgements: The authors thank the strategic project MAESTRA of the University of Padova for funding these research activities and the “Centro studi di economia e tecnica dell’energia Giorgio Levi Cases” for PhD grant to G.P. References [1] D.E. Fenton, J.M. Parker, P.V. Wright, Polymer, 14 (1973) 589-. [2] V. Di Noto, S. Lavina, G.A. Giffin, E. Negro, B. Scrosati, Electrochim. Acta, 57 (2011) 4-13. [3] J. Muldoon, C.B. Bucur, N. Boaretto, T. Gregory, V. Di Noto, Polymer Reviews, 55 (2015) 208-246. [4] M. Forsyth, H.A. Every, F. Zhou, D.R. MacFarlane, Ionic Conductivity in Glassy PVOH-Lithium Salt Systems, ACS Symp. Ser., 1998, pp. 367-382. [5] F. Bertasi, K. Vezzù, E. Negro, S. Greenbaum, V. Di Noto, Int. J. Hydrogen Energy, 39 (2014) 2872-2883.

Poly(vinyl alcohol)-based Electrolyte for Lithium Batteries

Gioele Pagot;Federico Bertasi;Keti Vezzù;V. Di Noto
2017

Abstract

Polymer electrolytes (PEs) were first proposed in the early 1970s [1]. Since then, this class of materials has attracted the attention of many scientists, becoming one of the most prolific research field in solid-state electrochemistry [2, 3]. PEs, when used in Li-ion secondary batteries, are able to overcome many of the disadvantages of classic liquid organic electrolytes, which typically show: a) a high flammability and a high vapor pressure; b) a low thermal, chemical, and electrochemical stability; and c) dendrites formation. Nevertheless, classical PEs show low values of ionic conductivity (σ < 10-6 S cm-1) with respect to the typically requested conductivity values for practical applications. It has been shown that systems based on poly(vinyl alcohol) (PVA) are able to dissolve lithium salts, giving rise to ion conducting materials that present higher conductivity values with respect to any other solid and solvent-free polymer electrolyte [4]. Nonetheless, in classic PEs, the ionic conductivity is mainly attributed to the migration of anionic species. Indeed, in these materials the Li+ transference number is usally very low (< 0.3) [5]. Here, we present a new ion conducting polymer electrolyte based on a Li+ poly(vinyl alkoxide) macromolecular salt. In this material, Li+ ions are provided by PVA alkoxide groups (-RO-Li+) which are obtained by a direct lithiation of hydroxyl groups of pristine polymer. Thus, a PE is obtained with Li+ cations coordinated by the O- ligand functionalities directly bonded to the PVA backbone chains. The lithium assay is determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy. The thermal stability is gauged using High-Resolution Thermo Gravimetric Analysis and the thermal transitions are investigated by means of Modulated Differential Scanning Calorimetry measurements. The structure and the interactions in proposed electrolytes are studied by vibrational spectroscopies both in the mid- and far-infrared and Raman spectroscopy. The interplay between structure and conductivity is investigated by Broadband Electrical Spectroscopy. Insights on the long range charge migration phenomena in these materials are presented. Acknowledgements: The authors thank the strategic project MAESTRA of the University of Padova for funding these research activities and the “Centro studi di economia e tecnica dell’energia Giorgio Levi Cases” for PhD grant to G.P. References [1] D.E. Fenton, J.M. Parker, P.V. Wright, Polymer, 14 (1973) 589-. [2] V. Di Noto, S. Lavina, G.A. Giffin, E. Negro, B. Scrosati, Electrochim. Acta, 57 (2011) 4-13. [3] J. Muldoon, C.B. Bucur, N. Boaretto, T. Gregory, V. Di Noto, Polymer Reviews, 55 (2015) 208-246. [4] M. Forsyth, H.A. Every, F. Zhou, D.R. MacFarlane, Ionic Conductivity in Glassy PVOH-Lithium Salt Systems, ACS Symp. Ser., 1998, pp. 367-382. [5] F. Bertasi, K. Vezzù, E. Negro, S. Greenbaum, V. Di Noto, Int. J. Hydrogen Energy, 39 (2014) 2872-2883.
2017
21st International Conference on Solid State Ionics
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