Journal of Power Sources 199 (2012) 239–246 Contents lists available at SciVerse ScienceDirect Journal of Power Sources jo ur nal homep age: www.elsevier.com/locate/jpowsour Development of ionic liquid-based lithium battery prototypes G.-T. Kim a , S.S. Jeong a , M.-Z. Xue a , A. Balducci a , M. Winter a , S. Passerini a,∗ , F. Alessandrini b , G.B. Appetecchi b,∗∗ a University of Muenster, Institute of Physical Chemistry, Corrensstr. 28/30, D48149 Münster, Germany b ENEA, Agency for New Technologies, Energy and Sustainable Economic Development, UTRINN-IFC, Via Anguillarese 301, Rome 00123, Italy a r t i c l e i n f o Article history: Received 14 July 2011 Received in revised form 4 October 2011 Accepted 11 October 2011 Available online 17 October 2011 Keywords: Ionic liquid Solvent-free electrolyte Sodium carboxymethylcellulose Lithium polymer battery prototype a b s t r a c t The lab-scale manufacturing of Li/LiFePO 4 and Li 4 Ti 5 O 12 /LiFePO 4 stacked battery prototypes and their performance characterization are described here. The prototypes were realized in the frame of an European Project devoted to the development of greener and safer lithium batteries, based on ionic liquid electrolytes, for integration with photovoltaic panels. N-Butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 14 TFSI) and N-butyl-N-methylpyrrolidinium bis(fluoro- methanesulfonyl)imide (PYR 14 FSI), selected as the ionic liquids (ILs), were used to formulate the poly(ethylene oxide)-LiN(SO 2 CF 3 ) 2 -PYR 14 TFSI (PEO-LiTFSI-PYR 14 TFSI) polymer electrolyte and the LiTFSI-PYR 14 FSI liquid electrolyte, which were employed to produce lithium metal and lithium-ion prototypes, respectively. The composite electrodes for the lithium metal and lithium-ion prototypes were prepared through, respectively, a solvent-free and a water-based procedure route. The performance of the lithium battery prototypes was evaluated in terms of specific capacity, energy, cycle life and coulombic efficiency at different current densities. The results have indicated high reproducibility and the feasibility of scaling-up solvent-free, lithium batteries based on ionic liquids for low and mid rate applications such as renewable energy storage. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Ionic liquids (ILs), organic/inorganic salts generally molten at room temperature, represent a very interesting new class of room temperature fluids since their non-flammability, negligible vapor pressure in conjunction with remarkable ionic conductivity, high thermal, chemical and electrochemical stability, high heat capac- ity and, in some cases, hydrophobicity [1]. Because of these unique properties ILs are excellent candidates as electrolytes and/or elec- trolyte components to replace volatile and hazardous organic solvents (alkyl carbonates) in lithium batteries. Ionic liquids based on saturated, cyclic, quaternary ammonium cations as N-alkyl-N-methyl-pyrrolidinium (PYR 1A where the sub- scripts indicates the number of carbons in the alkyl side chains, alkyl = n-propyl, n-butyl), and bis(trifluoromethanesulfonyl)imide (TFSI) or bis(fluoromethanesulfonyl)imide (FSI) as the anion have been successfully proposed for use in lithium batteries since their sub-ambient melting temperature, high room temperature conductivity, suitable electrochemical stability [2–5]. The last ∗ Corresponding author. Tel.: +49 251 8336026; fax: +49 251 8336032. ∗∗ Corresponding author. Tel.: +39 06 3048 3924; fax: +39 6 3048 6357. E-mail addresses: stefano.passerini@uni-muenster.de (S. Passerini), gianni.appetecchi@enea.it (G.B. Appetecchi). characteristic originates from the absence of acidic protons and double bounds that would strongly deplete the electrochemical stability and compatibility with the lithium metal anode [2,6,7]. Therefore, LiX-PYR 1A X (X = FSI or TFSI, A = propyl, n-butyl) mix- tures have been extensively investigated, showing very good cycling reversibility into lithium [8] and graphite [9–12] anodes, and LiCoO 2 cathodes [13]. Particularly, PYR 14 FSI-LiTFSI mixtures have been recently employed as electrolytes in Li 4 Ti 5 O 12 /LiFePO 4 lithium-ion cells, which have displayed very good cycling perfor- mance [14,15]. Moreover, it was successfully demonstrated [16–19] that the incorporation of PYR 1A TFSI ionic liquids (mainly PYR 14 TFSI) into solid polymer electrolytes (SPEs) largely enhances the room tem- perature ionic conductivity (above 10 -4 S cm -1 at 20 ◦ C) while maintaining wide electrochemical stability and good compatibil- ity towards the lithium metal anode even after prolonged storage times. The addition of ionic liquids allowed reducing the operative temperature of lithium metal polymer batteries (LMPBs) without depleting their performance [20–22]. Recently, it was shown that UV cross-linking allows incorporating higher ionic liquid amounts into the polymer electrolyte, thus further enhancing the ionic con- ductivity (e.g., 3.7 × 10 -4 S cm -1 at 20 ◦ C) without depleting its electrochemical and mechanical properties [23]. In this scenario, we decided to investigate the scale-up of lithium cells based on two different chemistries: (i) Li/LiFePO 4 (high energy) 0378-7753/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2011.10.036