Understanding Li-ion Diffusion Through Artificial SEI Coating Layers

Li-ion batteries show promise for storing large amounts of energy, yet, they are limited by the capacity of the graphite anode. High capacity alternatives, such as Li or Si, pose additional issues due to volume expansion and dendrite growth. In both Si and Li, Al₂O₃ coatings can be used as a protective layer on the anode [1,2]. We apply a combined theoretical and experimental study to both predict and confirm the structure of this interface, a combination which has been applied numerous times in this field [3]. Using Al K-edge X-Ray absorption spectroscopy calculated with DFT, we have shown how individual layers of Al₂O₃ grow via atomic layer deposition, and how the structure of the layers is dependent on the number of layers. This result was confirmed experimentally, and suggests that the performance of this coating layer is dependent on the number of layers grown. Finally, we calculate the Li⁺ diffusivity across the interface, and show how the interface changes during ion diffusion. These results provide both a computational and experimental explanation for the enhanced performance of Al₂O₃ coated high-capacity anodes.
1. He Y, et al. Adv Mater, 23, 43 (2011)
2. Chen, L, et al. J Mater Chem A, 5 (24), pp.12297-12309 (2017)
3. Harper, AF et al. JM Tech Rev (Under review Oct 2019)