(306g) Engineered Ionic Diffusion Layers to Increase Rate Capability of NCA Cathode in Lithium-Ion Cells

High energy and long cycle life are the key technical attributes required for widespread implementation of high-performance electric vehicles (EVs). High rate capability is the key to battery performance for many other applications including stationary grid connected applications and Hybrid Electric Vehicles (HEV’s). Despite significant strides made to-date, the current high energy density solutions suffer from degradation and limited cycle life limiting the widespread implementation of NCA cathode materials in Li-Ion batteries. There is growing evidence that several degradation mechanisms influencing these limitations take place at the cathode surface, motivating the use of larger particle sizes to minimize surface area and mitigate degradation. Larger particle sizes, however, decrease the overall rate of diffusion of lithium ions, causing a loss of activation of Li-rich phases and an increased loss of capacity at higher rates. In this paper, we show that Al₂O₃, TiO₂, and other similar ALD coatings applied to NCA powder, continuously covering active material particle surfaces, create an engineered SEI layer which facilitates an improved Li-ion diffusion pathway, increasing the rate capability of NCA cathodes even with larger particle sizes. Electrochemical analyses showed increased rate capability in 95x64 mm pouch cells (~2.5Ah) with coated NCA compared to uncoated, and XRD and TEM were used to characterize the underlying favorable interactions of coatings with the cathode surface. XALT Energy’s integrated cell design and manufacturing makes 95x64 mm cell performance representative of large format (216x216 mm) production EV cells, demonstrating the validity and scalability of this approach.