Enabling a High-Throughput Characterization of Microscale Interfaces within Coated Cathode Particles

Lithium ion batteries represent an emerging field. The development of battery materials could benefit from quick techniques that enable atomic-level diagnostics. High performance cathodes, such as high-voltage spinel, often require coatings to protect against the destructive electrochemical environments at the particle-to-electrolyte interface. The preparations of these coating are still in the early phases of development, and their analytical inspection by high resolution scanning and transmission electron microscopy (HR-S/TEM) techniques presents a significant challenge due to the microscale dimensions of cathode particles. In this work, a high throughput ultramicrotome technique was assessed for the characterization of the particle to coating interface. The ultramicrotome technique enabled the rapid preparation of cross-sections with a thickness of 126 ± 66 nm as determined by electron energy loss spectroscopy (EELS) measurements. Cathode particles composed of high-voltage spinel, LiNi0.5Mn1.5O4 (LNMO), coated with lithium niobate (LiNbO3) were synthesized and cross-sections were inspected using HR-S/TEM techniques. These ultra-thin cross-sections enabled the ability to obtain nanoscale information regarding the composition and crystallinity of the particle-to-coating interface over lateral areas of >1 µm. Accessible correlations between the electrochemical performance of the LiNbO3 coated LNMO particles and the HR-S/TEM results were enabled by the high-throughput method. Discharge capacity measurements were acquired over a series of 100 electrochemical cycles for both the LiNbO3 coated and the as-prepared LNMO particles. The limitations of the ultramicrotome technique are also discussed herein with respect to the coating morphology and the procedure for guidance toward technique optimization. The rapid preparation of ultra-thin cross-sections can assist the advancement of protective coatings on the surfaces of cathode particles for an efficient characterization of bulk-to-surface interfaces.