National Science Foundation Synthesis of Solid Electrolyte (Li x Al y Si z O) via ALD Jane P. Chang, University of California-Los Angeles, DMR Outcome: Researchers at UCLA have synthesized an ultra-thin ionic conductive film via Atomic Layer Deposition (ALD) as an electrolyte in Li-ion microbatteries Impact: An ultra-thin film electrolyte (Li x Al y Si z O) will provide unique opportunities in the development of a fully functional all-solid-state 3D Li-ion microbattery Explanation: Despite significant developments in electrode materials for potential 3D Li-ion microbattery, very little efforts have been devoted in developing a suitable solid electrolyte to enable a functional 3D Li-ion microbattery. Prof. Chang’s group has successfully synthesized an ultra-thin electrolyte (Li x Al y Si z O) that is conformal over complex, high-aspect ratio structures with an excellent thickness control. This technology will enable an innovative miniaturizations of the Li-ion batteries. Current Load Li + Li x Al y Si z O Anode Cathode 1-2 mm Proposed design of a 3D Li-ion micro-battery

National Science Foundation A viable solid electrolyte material for 3D Li-ion microbattery applications needs to be conformal over complex 3D structures. The conformality of Li x Al y Si z O thin film deposited via Atomic Layer Deposition (ALD) over a high-aspect ratio (AR) Si trench (W: 0.6 μm, L: 6 μm, AR: 10) was studied by HRTEM. A conformal coating of Li x Al y Si z O film was observed by EDX with Al Kα and O Kα emissions, confirming a successful ALD deposition. (a) SEM and (TEM) of a high AR Si trench of a high AR Si trench showing a conformal coating of Li x Al y Si z O along the sidewall of the trench (c) EDX spectra across Li x Al y Si z O confirming the presence of the deposited film Si Trench ALD Film 0.6 μm 6 μm Conformal Coating of Solid Electrolyte over Si Trenches Jane P. Chang, University of California- Los Angeles, DMR EDX Line Scan (a) (b) (c)

National Science Foundation An ultra thin film of Li x Al y Si z O has been deposited via ALD over a potential 3D anode material (a porous SiNW) to study the film conformality. HRTEM study of Li x Al y Si z O coated porous SiNW (vs. bare porous SiNW) shows a conformal deposition over the entire nanowire while maintaining the porous morphology of the NW. This HRTEM study demonstrated ALD’s superior thickness and composition control, which will likely play a key role in fabricating a well-tailored nanostructured electrode-electrolyte nanocomposite for 3D Li-ion microbatteries. Conformal Coating of Solid Electrolyte over Porous SiNW Jane P. Chang, University of California-Los Angeles, DMR (a)(b) HRTEM of (a) uncoated porous SiNW and (b) Li x Al y Si z O coated porous SiNW. A conformal coating of Li x Al y Si z O with a thickness of ~11nm has been observed over the entire wire, while maintaining the porous morphology of SiNW