National Science Foundation Thin Film Electrolytes for Energy Devices Jane P. Chang, University of California, Los Angeles, DMR Outcome: Researchers at UCLA have synthesized ultra-thin ionic conductive films as solid state electrolytes for miniaturized energy storage devices. Impact: Conformal thin-film electrolytes enable the miniaturization of lithium (Li)- ion batteries based on nanowire (NW) electrodes for on-chip power integration or lowering the operating temperature of solid oxide fuel cells (SOFC). The solid electrolyte coating on an electrode surface can also modify the electrochemical reaction kinetics by suppressing undesired reactions. Explanation: A number of 3D battery designs have been proposed, which involves a non-planar electrode structure and requires a conformal solid electrolyte grown over the electrode. The ALD LiAlSiO 4 over SnO 2 NWs was conformal and demonstrated the capability on suppressing the formation of Sn NPs during lithiation process, which impedes the application of SnO 2 as the electrode. On the other hand, the ultrathin yttria stablized zirconia (YSZ) reduces resistive losses within the cell, allowing efficient cell performance even at reduced operating temperatures. Operation of a 3D Li-ion  -battery

National Science Foundation Ionic Conductivity Elevated by Temperature Jane P. Chang, University of California, Los Angeles, DMR To confirm the measured ionic conductivity was from Li transport, ionic conductivity as a function of temperature was measured on amorphous LiAlSiO 4 and Li x Al y O (LAO) films with thicknesses of 10 nm. The activation energy of LiAlSiO 4 and LAO were found to be 0.89 and 0.46 eV, respectively, in good agreement with values reported in literature for bulk LiAlSiO 4 and bulk Li-β- Al 2 O 3, confirming that transport in the ALD films arises from Li + conduction. LiAlSiO 4 possesses a higher activation energy compared to LAO, showing the cation compositions, which affect the bonding environment of each atom in the material, plays an important role in Li transport. Ion conductivity of LiAlSiO 4 and LAO films, as a function of temperature in comparison with data reported in literature of single crystal  -LiAlSiO 4 ( ┴ c) (-∆-),  -LiAlSiO 4 (//c) (◊), LiAlSiO 4 (- ▼ -) and Li 4.4 Al 0.4 Si 0.6 O 4 (-□-)

National Science Foundation LiAlSiO 4 coating on SnO 2 nanowire batteries Jane P. Chang, University of California, Los Angeles, DMR To assess the performance of ALD LiAlSiO 4 as a solid electrolyte in integration with nanowires (NW) based electrodes, SnO 2 NWs were chosen as SnO 2 is a viable anode material. However, one issue for using SnO 2 NW as the negative electrode in Li-ion battery is the formation of metallic Sn nanoparticles (NP) during battery cycling, resulting in short-circuit failure and Sn-catalyzed electrolyte decomposition. In order to prevent the formation of large Sn NPs, faster Li transport is required. LiAlSiO 4 was applied over SnO 2 NWs and demonstrated the capability to suppress the formation of Sn NPs. In-situ HRTEM imaging and corresponding SEAD patterns showing that the formation of Sn NPs during SnO 2 lithiation (top) was suppressed after a 6nm amorphous LiAlSiO 4 was coated on the SnO 2 NW (bottom). Li 13 Sn 5

National Science Foundation Synthesis of Ultrathin Yttria-Stabilized-Zirconia Jane P. Chang, University of California, Los Angeles, DMR Ultrathin yttria stabilized zirconia (Y 2 O 3 -ZrO 2 ) was synthesized by radical enhanced atomic layer deposition (REALD), after the charactering the growth rate of each constituent oxide, Y 2 O 3 and ZrO 2. The growth rates were found to be 0.47 Å/cycle and 0.62 Å/cycle for Y 2 O 3 and ZrO 2, respectively. The cationic ratio of deposited YSZ film, prepared as a solid solution, was found to be correlated to the number of constituent oxide cycles. REALD YSZ film with 1:9 (Y-O)-(Zr-O) cycle ratio had a composition of 8.3 mol% of Y 2 O 3, within the target stoichiometry of 8-9 mol% YSZ, a composition that has the highest oxygen conductivity. (a) Growth rate of Y 2 O 3 and ZrO 2 synthesized by REALD. (b) Atomic composition of ALD YSZ films as a function of (Y-O): (Zr-O) cycle ratios. It demonstrates the controllability of the YSZ composition by adjusting the ALD cycle ratios.