"Ionic conductivity of zwitterionic system with various Li salt concentrations"

M. Kamataa, H. Aramakib, L. W. Gordona, A. L. Frischknechtc, R. A. Segalmana, G.H. Fredricksona

a University of California, Santa Barbara / b Mitsubishi Chemical America, Inc. / c Center for Integrated Nanotechnologies, Sandia National Laboratories

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Zwitterions are the organic salts which contain cation and anion that are covalently tethered; therefore, they have large dipole moments and zero net-charge. Owing to these characteristics, zwitterions have been applied as electrolyte materials of Li-ion batteries aiming high ionic conductivity and high transference numbers as large dipole moments dissociate Li salts into ions, which hinders salt aggregation, and zero net-charge suppresses transport of zwitterions, which enhances transportation of the target lithium ions.1, 2 It is generally favorable to increase Li salt concentration since theoretically total ionic conductivity proportionally increases with Li salt concentration, but the electrolytes with different salt concentrations show distinct structures and ionic transport mechanism becomes more complicated.

Here in this poster session, we focus on the zwitterion (Figure 1) which contains imidazole and TFSI moieties. This chemical structure has bulky cationic and anionic moieties which delocalize positive and negative charge and reduce the interaction with Li salt, leading to the higher Li ion conductivity. Utilizing this zwitterion, we discuss the relationship between salt concentration and ionic conductivity and transference number while elucidating the effect of the structures of zwitterion/LiTFSI mixtures.

References:

  1. Yoshizawa-Fujita, M. & Ohno, H. Applications of Zwitterions and Zwitterionic Polymers for Li-Ion Batteries. The Chemical Record 23, e202200287 (2023).
  2. Jones, S. D., Bamford, J., Fredrickson, G. H. & Segalman, R. A. Decoupling Ion Transport and Matrix Dynamics to Make High Performance Solid Polymer Electrolytes. ACS Polym Au 2, 430-448 (2022).