A Poly(ethylene carbonate)/Lithium Bis(fluorosulfonyl)imide/Titanium Oxide Composite Electrolyte Containing a Pyrrolidinium-based Ionic Liquid

Tuesday, 26 May 2015
Salon C (Hilton Chicago)
K. Kimura and Y. Tominaga (Tokyo University of Agriculture and Technology)

Solid polymer electrolytes (SPEs), formed by the combinations of flexible polymers and metal salts, can be battery electrolyte alternatives to the conventional liquid-based ones because they are not flammable and leakage-free. In the present work, poly(ethylene carbonate) (PEC) has been selected as a polymer matrix. Notably, poly(alkylene carbonate)s, such as PEC, are synthesized by alternating copolymerizations between carbon dioxide (CO2) and epoxides. Therefore, we initially focused on the CO2/epoxide copolymers as polymer hosts for the SPEs, being motivated by a concept of CO2 utilization as a raw carbon source [1,2]. We have already reported extraordinary ion-conductive behaviors of PEC, including high ionic conductivities at quite high Li salt concentration regions and extremely high Li transference number (tLi+) values [3,4]. For instance, an electrolyte containing 80wt% of LiTFSI showed a 120 times higher ionic conductivity than that of a sample containing 20wt% of the LiTFSI salt [3]. In addition, the tLi+ of a PEC-LiFSI (80wt%) electrolyte with TiO2 particles was estimated to exceed 0.7, according to an electrochemical measurement, as well as to a pulse-field-gradient NMR technique [4].

In the present work, we propose a quaternary PEC-LiTFSI mixture-based composite electrolyte membrane containing N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) ionic liquid (IL) as a plasticizing additive and a submicron-sized electrospun SiO2 fiber (SiF) as an inorganic filler, in view of creating more feasible battery materials. We demonstrate that the resulting mechanically stable membrane reinforced by SiF shows a conductivity of the order of 10-7 S cm-1 at 40 oC combined with a favorable tLi+ value of 0.36, which both are enhanced by the simultaneous presence of the IL and SiF. Furthermore, we demonstrate that the electrolyte works as a promising solid-state electrolyte in a galvanostatic cycling for a prototype battery having a LiFePO4-based cathode at an elevated temperature (75 oC). Further advancements can be achieved by the use of lithium bis(fluorosulfonyl)imide (LiFSI) as a salt and N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI) as an IL. We have confirmed that a quaternary PEC-LiFSI-Pyr13FSI-TiO2 electrolyte leads an ionic conductivity of the order of 10-5 S cm-1 at 40 oC which is more than an order of magnitude greater than that of the LiTFSI-based analogous sample mentioned above. Further detailed properties of the PEC-LiFSI mixture-based composite electrolytes, which are currently under investigation in our laboratory, will be presented.


[1]     Y. Tominaga, T. Shimomura, M Nakamura, Alternating Copolymers of Carbon Dioxide with Glycidyl Ethers for Novel Ion-Conductive Polymer Electrolytes, Polymer, 51, 4295 (2010).

[2]     M. Nakamura, Y. Tominaga, Utilization of Carbon Dioxide for Polymer Electrolytes II: Synthesis of Alternating Copolymers with Glycidyl Ethers as Novel Ion-Conductive Polymers, Electrochim. Acta, 57, 36 (2011).

[3]     Y. Tominaga, V. Nanthana, D. Tohyama, Ionic Conduction in Poly(ethylene carbonate)-Based Rubbery Electrolytes Including Lithium Salts, Polymer J., 44, 1155 (2012).

[4]     Y. Tominaga, K. Yamazaki, Fast Li-ion Conduction in Poly(ethylene carbonate)-Based Electrolytes and Composites Filled with TiO2 Nanoparticles, Chem. Commun., 50, 648 (2014).


This work was financially supported by a Grant-in-Aid for Scientific Research (B) of JSPS KAKENHI (25288095), Japan.