A Low Cost and Scalable Approach for Coating Cathode Materials

Abstract

High voltage (e.g., LNMO) and high capacity (e.g., NMC) cathode materials are highly desirable for achieving high energy density batteries. However, most of these cathode materials participate in parasitic reactions with electrolyte components. These reactions decrease the cyclic stability and capacity of these cathode materials, and thus lower their attractiveness. These parasitic reactions can be minimized by applying a thin coating of oxide materials such as silica or zirconia. Silica coating on cathode materials is highly desirable because of its low cost and high electrochemical stability. Several methods including ball milling of silica particles with cathode powder, sol-gel deposition of silica using protic solvents (e.g., ethanol and ammonium hydroxide) has been explored. However these methods have their own limitations, for example, ball milling based method provides incomplete coating formation, and the use of protic solvents such as ethanol and ammonium hydroxide in sol-gel silica deposition results in leaching of Li+ ions out of the cathode materials. Leaching of Li+ out of cathode particles results in lowered capacity of coated cathode materials. Therefore obtained coated cathode materials generally have a lower capacity than the uncoated cathode materials. Therefore, there is a need of a low cost method that provides a uniform coating but without leaching out the Li+ ions or compromising with the mechanical integrity of the cathode particles.In the present work, we demonstrate a low cost and scalable method that provides very thin coatings of oxide materials but without compromising with the capacity and mechanical properties of the cathode material. Coating presence was confirmed by using transmission electron microscope (TEM), energy dispersive X-rays (EDX), and X-ray photoelectron spectroscopy (XPS). Preliminary, results showed that the cells having coated cathodes have better cyclic stability when compared to the cells made of uncoated cathode materials.This research is funded by DOE’s Vehicle Technologies Office by Program Manager Dr. Changwon Suh.