UCLA UCLA Electronic Theses and Dissertations Title Engineering Lithium Ion Conducting Thin Film Solid Electrolytes by Atomic Layer Deposition Permalink https://escholarship.org/uc/item/2vr3z5pd Author Cho, Jea Lyen Publication Date 2015 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA Los Angeles Engineering Lithium Ion Conducting Thin Film Solid Electrolytes by Atomic Layer Deposition A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Chemical Engineering by Jea Lyen Cho 2015 ABSTRACT OF THE DISSERTATION Engineering Lithium Ion Conducting Thin Film Solid Electrolytes by Atomic Layer Deposition by Jea Lyen Cho Doctor of Philosophy in Chemical Engineering University of California, Los Angeles 2015 Professor Jane P. Chang, Chair A viable solid state inorganic Li-ion conductor, lithium aluminosilicate (LixAlySizO, LASO), was synthesized by atomic layer deposition (ALD). Investigations of the reaction mechanisms during ALD depositions of the constituent oxides of LASO, Al2O3, LiOH, and SiO2, were first conducted via in-situ Fourier transform infrared spectroscopy (FTIR). The deposition rate of ALD Al2O3 and LiOH were 1.1 and 1.2 Å /cycle respectively while it was not possible to deposit SiO2 by ALD at the conditions studied. The growth of three tertiary oxides, AlxSiyO, LixAlyO, and LixSiyO were confirmed by ALD, demonstrating that functionalization through hydroxylated LiOH and Al2O3 surfaces enabled the incorporation of ALD SiO2 at low temperatures. The in-situ FTIR study revealed that presence of electropositive metal atom in vicinity of surface Si-OCH2CH3* specie is essential for the incorporation of ALD SiO2 at low temperatures. No presence of incubation times were found for ALD deposition of each constituent oxide on the other, allowing ALD deposition LASO as a solid solution based on its constituent oxides. The growth rate of ALD LiAlSiO4 was found to be 20.6 Å /global cycle. ii The as-deposited ALD LASO films were amorphous with desired physiochemical properties viable for solid electrolyte applications. The calculated values of ionic conductivity were in the range of 1.75 × 10-9 to 7.22 × 10-8 S/cm, which were tunable by adjusting the number of ALD sub-cycles of the constituent oxides. The activation energy of Li-ion conduction was found to be between 0.46-0.89 eV, which was comparable to that reported in literature. An epitaxial crystallization of the as-deposited amorphous films into β-LiAlSiO4 was achieved for selected compositions of LASO upon post-deposition rapid thermal annealing, with a relationship of LiAlSiO4 1210 || Si (100) and β-LiAlSiO4 1010 || Si (001) to Si substrate. An exceptional conformality of ALD LASO coating was demonstrated on prospective 3D architectures for electrodes, including high aspect ratio trenches and nanowires. Integration of ALD LixAlySizO films with electrode materials including carbon electrode (both 2D and 3D), SnO2, and SiGe nanowires were investigated. ALD LixAlySizO coating on 2D carbon electrode improved the coulombic efficiency from 91% to 98%. Integration of 3D carbon array electrodes demonstrated a high areal capacity of 7.36 mAh/cm2, which was 6.75 times higher than the maximum areal capacity obtained from 2D carbon electrodes. In-situ HRTEM study on ALD coated SnO2 and Si0.6Ge0.4 nanowires demonstrated promising prospects of ALD LASO not only as a solid electrolyte but also as a stable artificial solid electrolyte interface layer which can improve both physiochemical and mechanical stability of electrode materials. iii The dissertation of Jea Lyen Cho is approved. Bruce Dunn Harold Monbouquette Jane P. Chang, Committee Chair University of California, Los Angeles 2015 iv TABLE OF CONTENTS CHAPTER 1: INTRODUCTION ................................................................................................... 1 1.1 Motivation ........................................................................................................................... 2 1.2 Li-ion Battery ...................................................................................................................... 3 1.3 Need for Solid Electrolyte ................................................................................................ 17 1.4 Atomic Layer Deposition for Li-ion Battery Applications ............................................... 31 1.5 Scope and Organization .................................................................................................... 43 CHAPTER 2: EXPERIMENTAL SETUP ................................................................................... 44 2.1 Thin-Film Deposition Reactors......................................................................................... 44 2.2 Material Characterization Techniques .............................................................................. 54 CHAPTER 3: MECHANISTIC STUDY OF ALD LIXALYSIZO ................................................ 93 3.1 Mechanistic Study on ALD of Al2O3 by TMA/H2O Chemistry ....................................... 94 3.2 Mechanistic Study on ALD of LiOH by LTB/H2O Chemistry ........................................ 99 3.3 Mechanistic Study on ALD SiO2 by TEOS/H2O Chemistry .......................................... 103 3.4 Mechanistic Study on ALD of AlxSiyO by TMA/H2O/TEOS/H2O Chemistry .............. 108 3.5 Mechanistic Study on ALD of LixAlyO by TMA/H2O/LTB/H2O Chemistry ................ 118 3.6 Mechanistic Study on ALD of LixSiyO by LTB/H2O/TEOS/H2O Chemistry ................ 126 3.7 Investigation on Incubation Times in ALD of LixAlySizO ............................................. 131 3.8 In-situ FTIR Study of ALD of LixAlySizO ...................................................................... 134 3.9 Summary ......................................................................................................................... 136 CHAPTER 4: SYNTHESIS OF LIXALYSIZO THIN FILMS BY ALD .................................... 138 4.1 ALD of LiAlSiO4 ............................................................................................................ 139 4.2 Electrochemical Characterization of LixAlySizO ............................................................ 141 4.3 Ionic Conductivity of LixAlySizO ................................................................................... 142 4.4 Controlled Crystallization of LiAlSiO4 .......................................................................... 145 4.5 Conformality of ALD LASO on complex 3D structures ................................................ 148 4.6 Summary ......................................................................................................................... 150 CHAPTER 5: INTEGRATION OF ALD LIXALYSIZO TO ELECTRODE MATERIALS ...... 152 5.1 ALD LixAlySizO coating on 2D carbon slurry electrode ................................................ 153 5.2 ALD LixAlySizO coating on 3D carbon array electrodes ................................................ 158 5.3 ALD LixAlySizO coating on SnO2 nanowire ................................................................... 159 5.4 ALD LixAlySizO coating on SiGe nanowire ................................................................... 163 5.5 Synthesis of an organic-inorganic hybrid thin film solid electrolyte .............................. 167 5.6 Summary ......................................................................................................................... 170 CHAPTER 6: SUMMARY......................................................................................................... 172 APPENDICES ............................................................................................................................ 175 BIBLIOGRAPHY ....................................................................................................................... 246 v LIST OF FIGURES Figure 1.1 Comparison of the increased power required for mobile electronic devices and the actual increase of battery power, showing diverging power gap between estimated power consumption versus Li-ion battery (Jeong et al. 2011) ................................................................... 2 Figure 1.2 Comparison of different battery technologies in terms of volumetric and gravimetric energy density (Tarascon et al. 2001) ............................................................................................. 3 Figure 1.3 Schematic of Li-ion secondary rechargeable battery. The cell consists of two electrodes (cathode/anode) separated by an electrolyte. (Adapted from (Choi et al. 2011)) .......... 4 Figure 1.4 Comparison of energy density and recharge between conventional and miniaturized batteries, highlighting the need of higher density batteries in the future (Serrano et al. 2009) .... 11 Figure 1.5 Schematic illustrations of 2-D planar and 3-D interdigitated array electrode architectures both under the same footprint denoted as ‗A‘. ........................................................ 12 Figure 1.6 Theoretical areal capacity of LiCoO2 and graphite half-cells as a function of aspect ratio (AR) for various pitch values, with anode specifications of d=15 nm, h=400 nm, and t=15 nm. Filled symbols denote LiCoO2 and the empty ones denote graphite. .................................... 14 Figure 1.7 A schematic representation of alternative three-dimensional, integrated, solid-state lithium-ion