Paper TF+PS-MoM4
Modular Rotating Cylinder Design for Spatial ALD on Porous Flexible Substrates

Monday, November 10, 2014, 9:20 am, Room 307

Li-ion batteries (LIBs) have a capacity that typically decays versus number of charge-discharge cycles. Surface coatings on LIB electrodes fabricated using atomic layer deposition (ALD) can dramatically improve the capacity stability. The commercialization of these ALD coatings requires the ability to perform ALD on porous battery electrodes on flexible metal webs. In this work, a new spatial ALD (S-ALD) reactor is developed that is based on a modular rotating cylinder design. The outer cylinder remains fixed and contains a series of slits. The slits can accept a wide range of modules that attach from the outside and accommodate precursor dosing, purging or pumping. The inner cylinder rotates (0-200 RPM) and passes underneath the various slits that are spatially separated. This new S-ALD reactor has been characterized using trimethyl aluminum (TMA) and ozone to grow Al₂O₃ ALD films at 40°C on metallized PET substrates. Spectroscopic ellipsometry measurements obtained Al₂O₃ ALD growth rates of 0.6 -1.1 Å/cycle depending on the O₂ pressure used to prepare the ozone. The Al₂O₃ ALD growth rate was also constant with changing rotation speeds from 60 to 150 RPM. Future experiments will deposit Al₂O₃ ALD films on porous electrodes on flexible metal webs. For these depositions, a “push-pull” design will be utilized where the pressure of the precursor dose will “push” the precursor and carrier gas into the evacuated porous electrode. The reaction products and carrier gas will then be “pulled” from the porous electrode by vacuum pumping. This new spatial ALD reactor has the potential to deposit uniform and conformal thin films on large area and flexible porous substrates at high deposition rates.