Atomic Layer Deposition of Aluminum Sulfide: Growth Mechanism and Electrochemical Evaluation in Lithium-Ion Batteries

This study describes the synthesis of aluminum sulfide (AlS x ) thin films by atomic layer deposition (ALD) using tris(dimethylamido)aluminum and hydrogen sulfide. We employed a suite of in situ measurement techniques to explore the ALD AlS x growth mechanism, including quartz crystal microbalance, quadrupole mass spectrometry, and Fourier transform infrared spectroscopy. A variety of ex situ characterization techniques were used to determine the growth characteristics, morphology, elemental composition, and crystallinity of the resultant AlS x films. This study revealed that the AlS x growth was self-limiting in the temperature range 100–250 °C, and the growth per cycle decreased linearly with increasing temperature from ∼0.45 Å/cycle at 100 °C to ∼0.1 Å/cycle at 250 °C. The AlS x films were amorphous in this temperature range. We conducted electrochemical testing to evaluate the ALD AlS x as a potential anode material for lithium-ion batteries (LIBs). The ALD AlS x exhibited reliable cyclability over 60 discharge–charge cycles with a sustainable discharge capacity of 640 mAh/g at a current density of 100 mA/g in the voltage window of 0.6–3.5 V.