Atomic Layer Deposition of LiOH and Li₂CO₃ Using Lithium t-Butoxide as the Lithium Source

Abstract

Atomic layer deposition (ALD) was utilized to grow LiOH and Li2CO3 films using lithium tert-butoxide, H2O and CO2. Film growth was monitored with a quartz crystal microbalance at 225 °C. LiOH ALD had a growth rate of 12.7 ng•cm-2•cycle-1 before displaying evidence for hygroscopic behavior. Li2CO3 ALD had a growth rate of 17.1 ng•cm-2•cycle-1. The film identities were confirmed using Fourier transform infrared and X-ray photoelectron spectroscopies. Lithium-containing films are present in the solid-electrolyte interphase (SEI) on graphite anodes of Li-ion batteries. The ALD of an artificial SEI layer may limit lithium loss and improve the capacity stability during charge-discharge cycles.

Plasma-assisted and thermal atomic layer deposition of electrochemically active Li2CO3

“…The previously reported growth per cycle of 0.8Å for thermal ALD of Li 2 CO 3 , 16 differs from our values. The reason for this difference is unclear, yet it is noted that the main difference with our process is a higher reactor pressure.…”

“…The increased growth per cycle can be explained by the fact that LiOH is hygroscopic and easily absorbs H 2 O and forms a hydrate. 16,23,28 It is reported for thermal ALD of LiOH at 225 C that long purge times of 2 hours lead to a stable mass measured by QCM as a result of H 2 O desorption. 16 To further investigate the lm instability for growth temperatures above 250 C, 50 nm thick lms were fabricated at different deposition temperatures.…”

“…16,23,28 It is reported for thermal ALD of LiOH at 225 C that long purge times of 2 hours lead to a stable mass measured by QCM as a result of H 2 O desorption. 16 To further investigate the lm instability for growth temperatures above 250 C, 50 nm thick lms were fabricated at different deposition temperatures. These were then subsequently exposed to CO 2 and H 2 O pulses inside the ALD reactor.…”

“…Li 2 O and LiOH oen develop simultaneously during processing due to the reversible reaction with H 2 O and CO 2 and are being deposited by ALD as well. [16][17][18][19][20]22,23 These materials are also widely used as building block for the fabrication of various other Li-ion battery active materials. [24][25][26]…”

Remote Plasma Atomic Layer Deposition of Thin Films of Electrochemically Active LiCoO2

“…Due to the surface chemistry controlled deposition process, ALD is chosen in this work and provides an excellent conformality and thickness control at the atomic level, even in challenging high-aspectratio structures. Several lithium compounds have recently been deposited using ALD in the form of LiOH, Li 2 CO 3 and lithium lanthanum titanate [(Li, La) x Ti y O z (LLT)] films (13,14), however no reports of electrochemical analysis of ALD deposited lithium containing materials are available to date. An overview of Li-based materials deposited by ALD as reported in the literature is shown in Table I.…”