| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Monday Sessions |
| Session TF+EM-MoM |
| Session: | ALD for Energy Conversion, Storage, and Electrochemical Processes |
| Presenter: | Ryan Sheil, University of California at Los Angeles |
| Authors: | R. Sheil, University of California at Los Angeles J. Lau, University of California at Los Angeles P. Moni, MIT C. Choi, University of California at Los Angeles K. Jungjohann, Sandia National Laboratories J. Yoo, Los Alamos National Laboratory K. Gleason, MIT B. Dunn, University of California at Los Angeles J.P. Chang, University of California at Los Angeles |
| Correspondent: | Click to Email |
3D battery architectures have the potential to meet the power and energy density demands of next generation microelectronic devices. One requirement in the utilization of 3D based electrodes is the incorporation of a solid electrolyte that can be coated pinhole free and conformally on high aspect ratio structures. Lithium aluminosilicate (LixAlySizO, LASO), a solid oxide Li-ion conductor, synthesized by atomic layer deposition (ALD) is a promising electrolyte material for 3D battery applications due to its adequate ionic conductivity (8.2×10-8 S/cm) in thin film applications as well as its ability to improve electrode stability. The self-limiting nature of ALD allows precise thickness and composition control when applied to complex metal oxides. Lithium tert-butoxide (LTB), trimethylaluminum (TMA), and tris(tert-butoxy)silanol (TTBS), were precursors used to synthesize LASO by ALD.
In order to further explore potential material properties, ALD deposited LASO was combined with a polymer electrolyte, poly-(tetravinyltetramethylcyclotetrasiloxane) (PV4D4) deposited via initiated chemical vapor deposition (iCVD). The LASO solid electrolyte offers high electrical resistance and chemical stability at the electrochemically active interface, while the pV4D4 solid electrolyte offers improvements in the mechanical integrity of the electrode. A hybrid film consisting of 5 nm LASO and 400 nm PV4D4 demonstrated a room temperature ionic conductivity of 3.4 x 10-7 S/cm, showing no significant increase in interfacial resistance. Integration with both 2D and 3D electrodes has shown substantial improvements in cycling and increased coulombic efficiency.
Current research on Li-ion batteries is directed at creating next generation electrode materials. One of the most viable 3D designs is through the use of nanowire electrodes, in which Si and Ge can offer much larger charge capacities (8444 A h L-1 for Li15Si4 and 7366 A h L-1 for Li15Ge4, respectively) than traditional carbon based anode materials, but suffer large volume expansion upon lithiation. Using an in-situ TEM electrochemical characterization technique, dynamic processes and structural changes are able to be observed during the lithiation/delithiation of a SiGe nanobattery in real time. Preliminary results show that ALD LixAlySizO-coated Si0.4Ge0.6 alloy nanowire demonstrates lithiation and delithiation with an intact solid state electrolyte layer with ~39% radial expansion observed upon lithiation.