Highly conformal and high-ionic conductivity thin-film electrolyte for 3D-structured micro batteries: Characterization of LiPON film deposited by MOCVD method

Abstract

This paper reports a lithium phosphorus oxynitride (LiPON) thin-film electrolyte deposited using a metalorganic-chemical vapor deposition (MOCVD) method for 3D-structured micro batteries. It is shown that the MOCVD-LiPON film has both highly-conformal step coverage on a patterned substrate with line/space=2μm/2μm and aspect ratio=1 (51±3 nm) and high-ionic conductivity for very thin films deposited at 4.7 nm/min (5.9×10-6 S/cm for 190 nm and 5.3×10-6 S/cm for 95 nm). Detailed material characterization attributes the enhancement in ionic conductivity to a decrease in nanocrystallite size and improvement in chemical-composition uniformity in the film. In addition, electrochemical characterization of an all-solid-state thin-film battery fabricated with the 190 nm-thick LiPON film (Si substrate/Ti/Pt/LiCoO2/LiPON/a-Si:H/Cu) demonstrates that the LiPON film can successfully act as the electrolyte for lithium-ion batteries. Therefore, the MOCVD-LiPON film is a promising candidate material to realize 3D-structured micro batteries in the near future.

Advances in 3D Thin‐Film Li‐Ion Batteries

“…Even though depositions of SSEs using physical vapor deposition (PVD) and CVD have been reported, these do not provide adequate results in high aspect ratio structures. [69][70][71][72] To achieve good conformality, a self-limiting technique is required. The most commonly used is atomic layer deposition (ALD).…”

Recent advancements in solid electrolytes integrated into all-solid-state 2D and 3D lithium-ion microbatteries

“…Furthermore, it was attempted to deposit the LiPON on Si 3D substrate with the line/space ¼ 2 mm/2 mm and the aspect ratio of 1 using metalorganic-chemical vapour deposition (MOCVD). 32 The resulting lm was uniform, having a relatively large ionic conductivity of $10 À6 S cm À1 . 32 The functionality of the MOCVD-produced LiPON was tested and conrmed in the thin-lm battery a-Si:H/LiPON/LCO.…”

“…32 The functionality of the MOCVD-produced LiPON was tested and conrmed in the thin-lm battery a-Si:H/LiPON/LCO. 32 All in all, the new methods that showed satisfactory results of LiIPON deposition are currently under development, and a few studies are available yet.…”

“…Among the most common techniques to obtain thin lms are radio-frequency (RF) magnetron sputtering (MS), Pulsed Laser Deposition (PLD), Atomic Layer Deposition (ALD), Chemical Vapor Deposition (CVD), Electrodeposition (ED), nitrogen Ion Beam Assisted Deposition (IBAD), thermal evaporation (TE), and others. 19,[29][30][31][32][33] In fact, when 'micro-sized' electrolytes are developed, the same problems as for 'bulk' electrolytes exist along with additional specic problems. The ionic conductivity is less of a concern in microbatteries due to the shorter path for lithium ions; 34 however, a lot of studies have been devoted to keeping it on a satisfying level or improving it.…”

Design, Synthesis, and Characterization of Polymer Precursors to LixPON and LixSiPON Glasses: Materials That Enable All-Solid-State Batteries (ASBs)

“…LiPON is one of the most commonly employed solid-state electrolytes owing to its broad electrochemical stability window (0–5 V vs Li + /Li), , high critical current density (>10 mA cm –2 ), − and negligible electronic conductivity (10 –7 μS cm –1 ). ,, However, due to its limited ionic conductivity (10 –6 S cm –1 ), ,,,,, its application is restricted to thin-film batteries with limited energy densities and capacities. ,,, …”