Preparation and Electrochemical Properties of Semi-Perfluoroalkyl Compounds in a Li-Ion Electrolyte Solution

Abstract

IntroductionOrganogels formed by a low moleculr weight organic gelators (LMOG) are of great attentions for their application to organic gel electrolytes of lithium ion battery, dye-sensitized solar cells and so on [1]. Several studies on organogel electrolytes based on LMOGs show that the conductivity is practically identical in the gel and in the corresponding solution [2]. In our previous papers, LMOG having perfluoroalkyl groups in the molecules can gelate aprotic polar solvents such as PC, GBL and so on [3]. Here we report preparation and electrochemical properties of semi-perfluoroalkylated compounds 1 and 2.ExperimentalCyclic voltammmetry was carried out in a potential range of 0-3 V at a rate of 1.0 mV s–1, where natural spheroidal graphite purchased from Hosen Co. Ltd. was used as a carbon anode, and lithium metal was used as a counter and reference electrode. The oxidation potential measurements using linear sweep voltammmetry was carried out in a potential range of 3-7 V at a rate of 1.0 mV s–1, where a platinum was used as a working electrode. The electrolyte solution was a 1M LiPF6/ethylene carbonate and ethyl methyl carbonate (EC:EMC=1:2).Results and discussionFor compound 1, in the first sweep of the untreated carbonaceous thin-film electrode, irreversible cathodic currents were observed at ca. 0.5 V. The peak significantly reduced after the second cycle and therefore should be attributed to irreversible reactions such as electrolyte decomposition followed by formation of a surface film [4]. The CVs results indicate that the presence of compound 1 in the electrolyte solution is similar to the solution on cycling behavior. The oxidation potential of compound 1 is in accordance with that of the EC-EMC electrolyte without additive, expressing high resistance properties against oxidative decomposition.In this presentation, the electrochemical properties of the other compounds having a semi-perfluoroalkyl unit in the molecules will be discussed in terms of the molecular structeres.Reference[1] M. Miura et al ., ECS Transactions, 50, 89-94 (2013). L. Tao, et al., J. Mater. Chem. A, 3, 2344-2352 (2015).[2] A. Iuchi, et al., ECS Transactions, 16(24), 65-70 (2009). T. Yoshida, et al., ECS Transactions, 50, 95-102 (2013).[3] t. yoshida, et al., Chem. Lett., 44 (4), 512-514 (2015), T. Yoshida, et al., Bull. Chem. Soc. Jpn, 88, 1447-1452 (2015).[4] T. Doi, et al., J. Phys. Chem., 116, 12422 (2012) Figure 1