| AVS 61st International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF+EN+PS-TuA |
| Session: | ALD for Energy |
| Presenter: | Alexander Kozen, University of Maryland, College Park |
| Authors: | A.C. Kozen, University of Maryland, College Park A.J. Pearse, University of Maryland, College Park M.A. Schroeder, University of Maryland, College Park C. Liu, University of Maryland, College Park M. Noked, University of Maryland, College Park C.F. Lin, University of Maryland, College Park G.W. Rubloff, University of Maryland, College Park |
| Correspondent: | Click to Email |
Solid Li-based inorganic electrolytes offer profound advantages for energy storage in 3-D solid state batteries: (1) enhanced safety, since they are not flammable like organic liquid electrolytes; and (2) high power and energy density since the solid electrolyte can support interdigitated nanostructured electrodes, avoiding binders, separators, and much larger spacing (tens of mm’s) between fully separated electrodes. The quality of thin solid electrolytes – even in planar form – is currently a major obstacle to solid state batteries[1] restricting electrolyte thickness to >100 nm to control electronic leakage, consequently slowing ion transport across the electrolyte and impeding interdigitated 3-D nanostructure designs that offer high power and energy. Furthermore, the ion-conducting, electron-insulating properties of solid electrolytes are promising for their use as passivation or protective layers on metal anodes (Li, Na, Mg) and on cathodes in proposed “beyond-Li-ion” battery configurations such as Li-O2 and Li-S.
Atomic layer deposition (ALD) is well suited to the challenge of solid electrolytes, providing ultrathin, high quality films with exceptional 3-D conformality on the nanoscale. We have developed ALD processes for Li2O, Li3PO4, and LiPON from LiOtBu, H2O, and N2, exploiting spectroscopic ellipsometry, downstream mass spectrometry, and XPS surface analysis, all in-situ. Post-ALD XPS reveals for the first time carbon-free electrolytes and their intrinsic surface chemistry. E.g., ALD Li2O grown at 250C is reversibly transformed to LiOH upon exposure to H2O, but transforms back upon annealing. LiOH is completely and irreversibly converted to Li2CO3 by CO2 exposure. These kinds of observations are essential to developing process sequences for fabricating 3-D solid batteries.
We then demonstrate the impact of this solid electrolyte synthesis in several examples. For solid state batteries, we employ the electrolytes in planar and nanostructured battery configurations to determine their Li diffusivity and electrochemical performance. For beyond-Li-ion configurations with organic electrolytes, we show the use of ALD Li2O at controlled mass loading in high aspect ratio Li-O2 cathodes to elucidate the Li-O2 charging chemistry, and we demonstrate the use of the ALD solid electrolytes in passivating Li anodes in Li-S batteries.
[1] D. Ruzmetov, V. P. Oleshko, P. M. Haney, H. J. Lezec, K. Karki, K. H. Baloch, A. K. Agrawal, A. V. Davydov, S. Krylyuk, Y. Liu, J. Huang, M. Tanase, J. Cumings, and A. A. Talin, “Electrolyte Stability Determines Scaling Limits for Solid-State 3D Li Ion Batteries,” Nano Lett, vol. 12, no. 1, pp. 505–511, Jan. 2012.