Short communication Vinyl sulfones as SEI-forming additives in propylene carbonate based electrolytes for lithium-ion batteries Ralf Wagner ⁎, Sebastian Brox, Johannes Kasnatscheew, Dennis Roman Gallus, Marius Amereller, Isidora Cekic-Laskovic, Martin Winter ⁎⁎ MEET Battery Research Center, Institute of Physical Chemistry, University of Münster, Corrensstrasse 46, 48149 Münster, Germany abstract article info Article history: Received 12 December 2013 Received in revised form 2 January 2014 Accepted 3 January 2014 Available online 10 January 2014 Keywords: Lithium-based batteries Solid electrolyte interphase Propylene carbonate Additive Methyl vinyl sulfone Ethyl vinyl sulfone The electrochemical performance of propylene carbonate (PC) based electrolytes with methyl vinyl sulfone (MVS) and ethyl vinyl sulfone (EVS) as film-forming additives on graphite electrode was studied. The results indicate that already small amount of these additives is able to form a stable SEI and thus successfully prevent exfoliation of the graphite. Moreover, the tested additives showed slight impact on the cathode performance as well as on the safety characteristics. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Lithium-ion batteries (LIBs) first appeared in the electronic consum- er market before they emerged to the more demanding automotive market several years later. However, to be implemented in automotive cells, performance requirements are more stringent, especially in terms of energy density, cycling life, and safety issues [1]. At present, mixtures of alkyl carbonates including ethylene carbon- ate (EC) with one or more linear carbonates, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), along with the conducting salt, lithium hexafluorophosphate (LiPF 6 ), are used as electrolytes for LIBs [2]. The EC-based electrolyte shows some benefits, especially in terms of film-forming ability on graphite, but it suffers from severe drawbacks: EC offers a poor low temperature performance, mainly caused by its high melting point (T m = 36.4 °C), making the use of linear carbonates inevitable [3]. However, the major drawback lies within the use of linear carbonates. Their low flash point and high volatility have a considerable impact on the battery safety (Table 1). Thus, the conventional state of the art electrolyte cannot meet the requirements in large-scale applica- tions like, for example, in automotive cells. Propylene carbonate (PC) based electrolytes are a promising alterna- tive. In comparison to EC, PC offers a wider temperature range of oper- ation, primarily related to its lower melting point (T m = – 48.8 °C), and, in comparison to linear carbonates, a much higher flash point (Table 1). However, electrolytes consisting of pure PC with LiPF 6 as an electrolyte salt, are not able to form a stable solid electrolyte interphase (SEI) and therefore are not compatible with graphite as anode material [4]. Highly graphitic anodes exfoliate in electrolytes based on PC, which co- intercalates into graphite, followed by reduction of the solvated intercalates and the formation of gaseous products [5–8]. In order to improve this system, there has been a lot of research on SEI forming additives in recent years [9–12]. Prior to electrochemical reduction of the bulk electrolyte, as well as the formation of ternary lithium- graphite intercalation compounds (GICs), these additives are preferably reduced to form an efficient SEI, which subsequently inhibits PC co- intercalation. Many of the already known and investigated SEI additives contain at least one carbon-carbon double bond, which can be polymer- ized by electrochemically induced reduction and thus rapid formation of the SEI is possible [13]. Well-known examples are vinylene carbonate (VC) [14], vinyl ethylene carbonate (VEC) [15], vinyl acetate (VA) [16] and 2-Cyanofuran [17]. In the present paper, we introduce two vinyl sulfones: methyl vinyl sulfone (MVS) and ethyl vinyl sulfone (EVS), as new SEI-forming addi- tives for LiPF 6 /PC based electrolytes. The electrolytes were characterized with respect to flash points, LUMO energies, electrochemical stability window (ESW) and cycling behavior on graphite anodes. The stability Electrochemistry Communications 40 (2014) 80–83 ⁎ Corresponding author. Tel.: +49 251 83 36774. ⁎⁎ Corresponding author. Tel.: +49 251 83 36031. E-mail addresses: ralf.wagner@uni-muenster.de (R. Wagner), martin.winter@uni-muenster.de (M. Winter). 1388-2481/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.elecom.2014.01.004 Contents lists available at ScienceDirect Electrochemistry Communications journal homepage: www.elsevier.com/locate/elecom