(571e) Custom Fluidized Bed Reactor for Atomic Layer Deposition on Li-Ion Battery Cathode Powder

The first fluidized bed reactor for atomic layer deposition (ALD) on particles was developed almost two decades ago, which helped the ALD technology expand beyond the semiconductor industry to catalysis and energy storage. In particular, particle ALD can be applied to energy storage materials like nickel-rich cathode active materials like LiNi_xMn_yCo_1-x-yO₂ (NMC) to stabilize the surface and improve electrochemical performance for Li-ion battery applications. With sufficient cycles the ALD process deposits conformal, pin-hole free films with Angstrom-level precision. However, nickel-rich NMC such as LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) is an air-sensitive material that requires handling under inert conditions to prevent growth of surface contaminants like hydroxides and carbonates. Here, we show a unique fluidized bed reactor design that allows inert (un)loading of material and real-time quantification of vapor species evolved from the ALD reactions. NMC811 was coated using the trimethylaluminum (TMA)/water chemistry. The fluidization behavior of NMC811 powder was characterized and the minimum fluidization velocity calculated. Furthermore, the quality of the film deposited by the system was assessed using inductively coupled plasma optical emission spectroscopy (ICP-OES), Brunauer-Emmett-Teller (BET) analysis, and low energy ion scattering (LEIS). Controlled delivery of calibration gas to an on-line mass spectrometer allowed subsequent quantification gaseous species evolving from the NMC811 powder during the TMA and water doses. Our present work showcases a fluidized bed reactor capable of performing ALD on air-sensitive particles, in addition to quantifying the vapor species evolving from the powder. This reactor design can help inform construction of future fluidized bed reactors that coat air-sensitive material.