Lithium dope-undope reactions of a tin thin film electrode were investigated in a room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing 1 M LiTFSA with and without glyme as an additive. Lithium dope-undope was possible in 1 M LiTFSA/BMPTFSA with glymes. The resistance of the electrode-electrolyte interface with glyme was smaller than that without glyme, indicating the solvation environment of Li + affects the interfacial resistance in the ionic liquid electrolyte. IntroductionVarious organic solvent-based solutions have been widely used as rechargeable lithium battery electrolytes. However, these electrolytes may cause combustion and/or explosion in case of accidents due to their flammability and volatility. Since roomtemperature ionic liquids are regarded as nonflammable and nonvolatile, ionic liquid electrolytes are expected to improve safety of rechargeable lithium battery. Among many kinds of ionic liquids, 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing LiTFSA has been investigated as a promising electrolyte because of acceptable cathodic stability and conductivity [1][2][3][4][5].Poly(ethylene glycol)dialkyl ethers are generally known as glyme , and have the chemical structure of CH 3 O (CH 2 CH 2 O) n CH 3 . Glymes have more than two oxygen atoms per molecule. These oxygen atoms exhibit the nucleophilic ability, resulting in high solvation with regard to lithium cations. The coordination and solvation states of lithium ions in glyme have been discussed [6][7][8][9][10][11][12][13] and the electrode reaction of lithium has been studied in the mixtures of ionic liquids and glymes [14][15][16][17]. ECS Transactions, 25 (36) 169-176 (2010) 10.1149/1.3393853 © The Electrochemical Society 169 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.236.-224.35 Downloaded on 2015-06-26 to IPLithium is able to form alloy with tin at room temperature. The equilibrium phase diagram of Li-Sn system has been investigated [18] and the coulometric titration curve of Li-Sn have been measured [19,20]. The theoretical specific capacity of Li-Sn alloy (Li 4.4 Sn, 994 mAhg [21]) is higher than that of lithiated graphites (LiC 6 , 372 mAhg ). Thus, tin has been found considerable interest for use as anode materials in rechargeable lithium batteries and many reports on tin anodes have appeared in the literature [21][22][23][24][25][26][27][28][29].A tin anode reaction has been studied in a chloroaluminate ionic liquid (1-methyl-3-ethylimidazolium chloride (MEICl):AlCl 3 :LiCl =1:1.2:0.2) [30]. However, the tin anode reaction has not been studied extensively in non-chloroaluminate ionic liquids. In this study, the influence of addition of glymes on lithium dope / undope reactions for a tin film electrode was investigated in BMPTFSA containing LiTFSA. ExperimentalBMPTFSA was purchased from Kanto Kagaku. A tin film electrode was prepared by electroplating (Me...