- Nano Express
- Open Access
Lithium ion conductive behavior of TiO2 nanotube/ionic liquid matrices
© Vedarajan et al.; licensee Springer. 2014
Received: 16 July 2014
Accepted: 22 September 2014
Published: 1 October 2014
A series of TiO2 nanotube (TNT)/ionic liquid matrices were prepared, and their lithium ion conductive properties were studied. SEM images implied that ionic liquid was dispersed on the whole surface of TNT. Addition of TNT to ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMImTFSA)) resulted in significant increase of ionic conductivity. Furthermore, lithium transference number was also largely enhanced due to the interaction of anion with TNT. Vogel-Fulcher-Tammann parameter showed higher carrier ion number for TNT/BMImTFSA in comparison with BMImTFSA.
In the field of ionics, a number of researchers are in search for electrolytes showing both high ionic conductivity and high selectivity for target cation transport. Also, in view of battery safety, intense researches have been carried out on solid polymer electrolytes [1–3] and non-flammable ionic liquids [4–6]. As a most common electrolyte, polyether derivatives have been widely studied for a long time with respect to their ion conductive behavior. In spite of moderate ionic conductivity of polyethers, their lithium ion transference number is generally very low at ambient temperature due to strong binding of ether oxygen to lithium cation. Their lithium ion transference number ranges only from 0.1 to 0.2 at ambient temperature. Moreover, ionic liquids which are composed of cation and anion are also unsuitable for selective target cation transport, because such component ions also migrate under potential gradient.
As a common strategy for enhancement of lithium transference number, covalent immobilization of anion structure on polymer framework [7–11] has been examined. However, this approach always resulted in decrease of ionic conductivity, due to the decrease of carrier ion number. As an alternative approach, incorporation of anion receptor in ion conductive matrices [12–21] has also been widely investigated. Particularly, boron incorporation to electrolytes is a valuable approach in which Lewis acid strength is controllable by the choice of organoboron unit. So far, a variety of organoboron polymer electrolytes were prepared by hydroboration polymerization or dehydrocoupling polymerization, and their structure–property relationship has been reported in detail.
In the present paper, titanium oxide nanotube (TNT)/ionic liquid composites were prepared, and their ion conductive properties were studied. Addition of TiO2 to PEO was reported to be effective in enhancing tLi+. However, effect of TNT addition has not been reported so far. In the present work, addition of TNT to ionic liquid led to significant enhancement in both ionic conductivity and lithium ion transference number. As an interesting nanomaterial based on TiO2, synthesis of TNT was developed both by chemical method and electrochemical method (anodic oxidation) . Their applications as electrodes for various energy devices have also been studied [24–28]; however, it has not been examined as an additive for lithium ion conductive electrolytes to the best of our knowledge.
The ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMImTFSA) was synthesized by the reaction between 1-methylimidazole and 1-chlorobutane, followed by an ion-exchange reaction using lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) according to literature . Commercially available LiTFSA (Wako Pure Chemicals Industries Ltd., Richmond, VA, USA) was purchased and was used without further purification. Similarly, lithium sheets were purchased from Honjo Chemical Co. Ltd (Neyagawa City, Osaka, Japan). The ionic conductivity for the organic–inorganic hybrids was evaluated by complex impedance method on a Solartron 1260 impedance analyser (Solartron Analytical, Hampshire, UK) using an amplitude of 100 mV and in the frequency range of 0.1 Hz to 1 MHz. TNT was prepared by anodic oxidation method according to a literature . Each sample was prepared by mixing TNT (1 mol% of BMImTFSA), LiTFSA (equimolar to BMImTFSA) and BMImTFSA and stirring the mixture for 24 h. The sample was sandwiched between two blocks of stainless steel electrodes. All samples were thoroughly dried in vacuo before each measurement.
All the operations were carried out under an argon atmosphere using identical Li electrodes using potentiostat coupled with Frequency Response Analyser (Versastat-3; Princeton Applied Research Co. Ltd., Bangkok, Thailand). Scanning Electron Microscopy (SEM) analysis was carried out on a Hitachi H-7100 (Hitachi Ltd., Chiyoda-ku, Japan).
Results and discussion
VFT parameters for ion conductive matrices ( T o = 150 K)
σ at 51°C (Scm−1)
7.4 × 10−4
8.3 × 10−4
t Li + and related parameters for BMImTFSA and TNT/BMImTFSA
In summary, addition of TNT to ionic liquid was found to be a fruitful method to enhance both ionic conductivity and lithium transference number via anion-TiO2 interaction. When interaction between anion-anion receptor is strong, enhancement of lithium transference number results in generally decreased carrier ion number and lower ionic conductivity. On the other hand, when anion-anion receptor interaction is weak, only enhancement of ionic conductivity is observed with no enhancement in lithium transference number. In the present system, moderate TNT-TFSA anion interaction led to desirable enhancement of both ionic conductivity and lithium transference number at the same time.
We would like to thank Mr. Osamu Notoya at CNMT (Center for Nano Materials and Technology), JAIST for his assistance in the analysis of scanning electron microscopy.
- Fenton DE, Parker JM, Wright PV: Complexes of alkali metal ions with poly(ethylene oxide). Polymer 1973, 14: 589.View ArticleGoogle Scholar
- Wright PV: Electrical conductivity in ionic complexes of poly(ethylene oxide). Br Polym J 1975, 7: 319. 10.1002/pi.4980070505View ArticleGoogle Scholar
- Blonsky PM, Shriver DF, Allcock HR, Austin PE: Polyphosphazene solid electrolytes. J Am Chem Soc 1984, 106: 6854. 10.1021/ja00334a071View ArticleGoogle Scholar
- Welton T: Room-temperature ionic liquids: solvents for synthesis and catalysis. Chem Rev 1999, 99: 2071. 10.1021/cr980032tView ArticleGoogle Scholar
- Ohno H: Functional design of ionic liquids. Bull Chem Soc Jpn 2006, 79: 1665. 10.1246/bcsj.79.1665View ArticleGoogle Scholar
- Ueki T, Watanabe M: Macromolecules in ionic liquids: progress, challenges and opportunities. Macromolecules 2008, 41: 3739. 10.1021/ma800171kView ArticleGoogle Scholar
- Hardy LC, Shriver DF: Preparation and electrical response of solid polymer electrolytes with only one mobile species. J Am Chem Soc 1985, 107: 3823. 10.1021/ja00299a012View ArticleGoogle Scholar
- Tsuchida E, Ohno H, Kobayashi N: Single-ion conduction in poly[oligo(oxyethylene)methacrylate]-co-(alkali-metal methacrylates)]. Macromolecules 1988, 21: 96. 10.1021/ma00179a020View ArticleGoogle Scholar
- Xu W, Siow KS, Gao Z, Lee Y: Novel alternating comblike copolymer electrolytes with single lithium ionic conduction. Chem Mater 1998, 10: 1951. 10.1021/cm980109uView ArticleGoogle Scholar
- Doan KE, Ratner MA, Shriver DF: Synthesis and electrical response of single-ion conducting network polymers based on sodium poly(tetraalkoxyaluminates). Chem Mater 1991, 3: 418. 10.1021/cm00015a012View ArticleGoogle Scholar
- Fujinami T, Tokimune A, Metha MA, Shriver DF, Rawsky GC: Siloxyaluminate polymers with high Li + ion conductivity. Chem Mater 1997, 9: 2236. 10.1021/cm970399zView ArticleGoogle Scholar
- Mehta MA, Fujinami T: Li+ transference number enhancement in polymer electrolytes by incorporation of anion trapping boroxine rings into the polymer host. Chem Lett 1997, 915–916.Google Scholar
- Sun XG, Angell CA: “Acid-in-chain” versus “base-in-chain” anionic polymer electrolytes for electrochemical devices. Electrochim Acta 2001, 46: 1467. 10.1016/S0013-4686(00)00741-6View ArticleGoogle Scholar
- Hirakimoto T, Nishiura M, Watanabe M: Effects of addition of a boric acid ester monomer to electrolyte solutions and gel electrolytes on their ionic transport properties. Electrochim Acta 2001, 46: 1609. 10.1016/S0013-4686(00)00760-XView ArticleGoogle Scholar
- Nishihara Y, Miyazaki M, Tomita Y, Kadono Y, Takagi K: Synthesis and ion conductive characteristics of inorganic-organic hybrid polymers bearing a tetraarylpentaborate unit. J Polym Sci Part A 2008, 46: 7913. 10.1002/pola.23070View ArticleGoogle Scholar
- Matsumi N, Sugai K, Ohno H: Selective ion transport in organoboron polymer electrolytes bearing a mesitylboron unit. Macromolecules 2002, 35: 5731. 10.1021/ma0121666View ArticleGoogle Scholar
- Matsumi N, Mizumo T, Ohno H: Single ion conductive characteristics of poly(organoboron halide)-imidazole complex. Polym Bull 2004, 51: 389. 10.1007/s00289-004-0229-5View ArticleGoogle Scholar
- Matsumi N, Nakashiba M, Mizumo T, Ohno H: Novel polymer /salt hybrid composed of comblike organoboron polymer electrolyte and boron-stabilized imido anion. Macromolecules 2005, 38: 2040. 10.1021/ma047469pView ArticleGoogle Scholar
- Matsumi N, Sugai K, Sakamoto K, Mizumo T, Ohno H: Direct synthesis of poly(lithium organoborate)s and their ion conductive properties. Macromolecules 2005, 38: 4951. 10.1021/ma050026gView ArticleGoogle Scholar
- Matsumi N, Sugai K, Miyake M, Ohno H: Polymerized ionic liquid via hydroboration polymerization as single ion conductive polymer electrolytes. Macromolecules 2006, 39: 6924. 10.1021/ma060472jView ArticleGoogle Scholar
- Matsumi N, Nakamura Y, Aoi K, Watanabe T, Mizumo T, Ohno H: Enhanced ionic conduction in organoboron ion gels facilely designed via condensation of cellulose with boric acid in ionic liquids. Polym J 2009, 41: 437. 10.1295/polymj.PJ2008289View ArticleGoogle Scholar
- Chung SH, Wang Y, Persi L, Croce F, Greenbaum SG, Scrosati B, Plichta E: Enhancement of ion transport in polymer electrolytes by addition of nanoscale inorganic oxides. J Power Sources 2001, 97–98: 644.View ArticleGoogle Scholar
- Macak JM, Tsuchiya H, Ghicov A, Yasuda K, Hahn R, Bauer S, Schmuki P: TiO2 nanotubes: self-organized electrochemical formation, properties and applications. Curr Opin Solid State Mater Sci 2007, 11: 3–18. 10.1016/j.cossms.2007.08.004View ArticleGoogle Scholar
- Hyun Sik K, Seung-Ho Y, Yong-Hun C, Soon Hyung K, Yung-Eun S: TiO2-core/Sn-shell nanotube arrays based on monolithic negative electrode for Li-ion batteries. Electrochim Acta 2014, 130: 600.View ArticleGoogle Scholar
- Lifang H, Chundong W, Xiaolin Y, Ruguang M, Hongkang W, Peirong C, Kui Z: Synthesis of carbon nanotube/mesoporous TiO2 coaxial nanocables with enhanced lithium ion battery performance. Carbon 2014, 75: 345.View ArticleGoogle Scholar
- Jassen B, Julia K-L: Silicon on conductive self-organized TiO2 nanotubes - a high capacity anode material for Li-ion batteries. J Power Sources 2014, 258: 129.View ArticleGoogle Scholar
- Yiping T, Xiaoxu T, Guangya H, Guoqu Z: Nanocrystalline Li4Ti5O12-coated TiO2 nanotube arrays as three-dimensional anode for lithium-ion batteries. Electrochim Acta 2014, 117: 172.View ArticleGoogle Scholar
- Jie W, Ran R, Moses OT, Zongping S: Self-assembled mesoporous TiO2/carbon nanotube composite with a three-dimensional conducting nanonetwork as a high-rate anode material for lithium-ion battery. J Power Sources 2014, 254: 18.View ArticleGoogle Scholar
- Wilkes JS: Green Industrial Applications of Ionic Liquids. Edited by: Rogers RD, Seddon KR, Volkov S. Netherlands: Kluwer Academic Publishers; 2003:295.View ArticleGoogle Scholar
- Evans J, Vincent CA, Bruce PG: Electrochemical measurement of transference numbers in polymer electrolytes. Polymer 1987, 28: 2324. 10.1016/0032-3861(87)90394-6View ArticleGoogle Scholar
- Vogel H: The law of the relation between the viscosity of liquids and the temperature. Phys Z 1921, 22: 645.Google Scholar
- Fulcher GS: Analysis of recent measurements of the viscosity of glasses. J Am Ceram Soc 1925, 8: 339. 10.1111/j.1151-2916.1925.tb16731.xView ArticleGoogle Scholar
- Tamman G, Hesse WZ: Die abhängigkeit der viscosität von der temperatur die unterkühlten flüssigkeiten. Anorg Allg Chem 1926, 156: 245. 10.1002/zaac.19261560121View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.