Polyethylene Oxide (PEO)-Based Electrolyte for Lithium Sulfur Polymer Battery

Recently, innovations in the field of energy storage, requiring high capacity and efficiency triggered large number of studies on new systems such as batteries lithium-air and lithium sulfur. These new technologies may lead to significant advances and application as power sources in hybrid electric vehicles (HEVs), plugged-in hybrid vehicles (PHEVs), full electric vehicles (EVs) [1]. Lithium sulfur battery represents the most suitable candidate due to its promising characteristics in terms of specific capacity (1675 mAh g^-1) and energy density (3500 Wh kg^-1).

However, the Li-S electrochemical process leads to the formation of various polysulfide, i.e. species soluble in the common electrolytes, thus causing parasitic reaction and shuttle effects [2]. Furthermore, electrolytes such as carbonate have low thermal stability and flammability issues [3]. Hence, the study of electrolytes capable of supporting the high performance of the new electrode materials and the associated problems is necessary to optimize the cell performances. In this scenario, the ideal candidate for the use in the new generation of batteries is the polyethylene oxide-based electrolyte [4]. Herein, we report the characterization of a PEO-based membrane using LiCF₃SO₃ as the lithium-ion salt. The electrolyte, considered as suitable media for lithium-sulfur battery and characterized by high safety level, has been studied in terms of thermal properties (TGA, DSC), lithium ion conductivity, lithium interface stability, lithium transference number and cyclic voltammetry. Finally, a lithium-sulfur cell using the selected electrolyte has been efficiently investigated, by galvanostatic charge-discharge test, evidencing promising results in terms of delivered capacity and stability (see figure below reporting a typical charge discharge cycling profile of the studied lithium-sulfur polymer cell).

(Figure reports typical charge discharge cycling profile of the studied lithium-sulfur polymer cell)

Acknowledgements

This work was supported by Sapienza University-Volkswagen AG joint project

References

[1] R. Bernhard, A.Latini, S. Panero, B.Scrosati, J. Hassoun.   Journal of Power Sources 226 (2013) 329-333

[2] Sheng S. Zhang Journal of Power Sources 231 (2013) 153e162

 [3] Nagasubramanian, G. , Fenton, K. 101 (2013) 3-10

[4] F. Croce, R. Curini, A. Martinelli , L Persi , F. Ronci e B. Scrosati J. Phys. Chem. B 1999, 103, 10632-10638