In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2016-02, No. 4 ( 2016-09-01), p. 628-628
Abstract:
Rechargeable Li-air (Li-O 2 ) batteries have recently attracted enormous attention due to their prospective high energy density. To realize reversible and stable operation of Li-air batteries, however, many serious problems, such as volatilization of electrolyte, high charge overpotential and electrolyte decomposition by O 2 - radical, have to be solved [1]. We previously reported that equimolar mixtures of glymes and Li salts behave as ionic liquids (ILs) rather than as ordinary concentrated electrolyte solutions [2] . For instance, triglyme (G3) can coordinate to a Li + ion, forming a 1:1 solvate cation of [Li(G3)] + , which behaves as an independent cation similar to the cation of typical ionic liquids. Thus, the glyme-Li salt complex has been categorized as a new subclass of ionic liquids called “solvate ILs” [3]. Solvate ILs show negligible volatility and high oxidative stability which are important for stable operation of the Li-air battery system [4] . The concentration of Li salt in glyme-Li salt solvate ionic liquids are extremely high ~ 3 mol dm −3 . In this extremely concentrated electrolyte, almost all the solvents (glyme) coordinate to Li + cation and almost no free (uncoordinated) solvent exists, which is an unique nature of the “concentrated electrolyte” [5]. These days, highly concentrated electrolytes, including solvate ionic liquids, have been attracted much attention owing to their unique properties [6] . In this study, we investigated the relationship between solubility of the intermediate and reversibility of Li-air battery performance as a function of Li + concentration by RRDE method. Although it has been already reported that solubility of the intermediate depends on donor number of the solvent species and affects morphology of the discharge compounds [7], our results revealed that high Li + concentration suppresses the intermediate solubility even in high donor number solvents such as DMSO ( Figure ). This low intermediate solubility originates from the absence of free solvent molecules. For the dissolution of LiO 2 , LiO 2 should be solvated. The absence of free solvent in the highly concentrated electrolytes results in insolubility of LiO 2 . Interestingly, reversibility of the disk electrode reaction in highly intermediate soluble electrolyte (0.1 mol dm -3 Li[TFSA]/DMSO) is much lower than that of the intermediate insoluble electrolyte (3 mol dm -3 Li[TFSA]/DMSO) ( Figure ) because of dissolution of the intermediate species into the electrolyte solution. Further discussion such as relationship between solubility of LiO 2 and battery performance will also be discussed. Acknowledgement This study was partly supported by RISING program from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References [1] P. G. Bruce et al. Nat. Mater . 11 , 19 (2012). [2] T. Tamura et al. , Chem. Lett. , 39 , 753 (2010); K. Yoshida et al., J. Am. Chem. Soc. , 133 , 13121 (2011). [3] C. A. Angell et al. Faraday Discuss., 154 , 9 (2012); T. Mandai et al. , Phys. Chem. Chem. Phys. , 16 , 8761 (2014). [4] R. Tatara et al., Chem. Lett. , 42 , 1053 (2013). [5] K. Ueno et al., J. Phys. Chem. B , 116 , 11323 (2012); C. Zhang et al., J. Phys. Chem. B , 118 , 5144 (2014); K. Ueno et al., Phys. Chem. Chem. Phys. , 17 , 8248 (2015). [6] H. Moon et al. , J. Phys. Chem. C , 118 , 20246 (2014); Yamada et al. , J. Electrochem, Soc. , 162 , A2409 (2015). [7] L. Johnson et al., Nat. Chem. , 6 , 1091 (2014). Figure 1
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2016-02/4/628
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2016
detail.hit.zdb_id:
2438749-6
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