(502c) Organic Inorganic Hybrids as Electrolytes

Secondary batteries containing Li metal as anode provide one of the highest known energy densities. They are therefore desirable candidates for electric and hybrid electric vehicles. However, current liquid electrolytes cannot be employed with lithium metal anode because they allow dangerous lithium dendrite growth during the charge discharge cycles. Solid polymer electrolytes, on the other hand, are known to be effective in reducing dendrite growth and hence, spurred lot of interest in the development of polymer and composite polymer electrolytes for use in lithium batteries. The well-known solid ionic conductor, poly ethylene oxide (PEO), is crystalline and exhibits poor ionic conductivities at room temperature. Several alternatives are currently being investigated to improve the ionic conductivity and mechanical properties of PEO. Alternatively, Ionic liquids (IL's) are emerging as novel electrolytes for energy storage devices due to their attractive properties such as, ultralow vapor pressure, high thermal stability, high ionic conductivity and wide redox stability. But, IL's suffer from the low lithium transference numbers and also problems pertaining to dendrite growth. Tethering IL's to nano particles may mitigate the above problems. Recently, we have created organic-inorganic nano composite materials by covalently tethering a PEO to a variety of nano particles [1-3]. Liu et al. [4] synthesized luminescent ZnO nanocrystals stabilized by ammonium based IL. The IL modified ZnO nano crystals showed tunable photoluminescence properties. Nevertheless, none of the reported work were investigated the solvent free IL nano particle composites as electrolytes. Herein, we report IL tethered nano particle hybrid materials (NILs) synthesis and characterization as electrolytes for Li batteries. NILs exhibit reasonably high ionic conductivities, when doped with lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) salt, and manifest yield stress fluid type mechanical properties with wide redox stability window.

[1] A. B. Bourlinos, R. Herrera, N. Chalkias, D. D. Jiang, Q. Zhang, L. A. Archer, E. P. Giannelis, Advanced Materials, 17, 234, 2005. [2] P. Agrawal, H. Qi, L. A. Archer, Nano Letters, 10, 111, 2010. [3] J. L. Nugent, S. S. Moganty, L. A. Archer, Advanced Materials, In Press. [4] D. P. Liu, G. D. Li, Y. Su, J. S. Chen, Angew. Chem. Int. Ed, 45, 7370, 2006.