lithium iron phosphate (CAS# 15365-14-7). The product is described as a powder mixture of lithium phosphate and iron phosphate used in the domestic manufacture of battery cells and systems targeted primarily for use in electric and hybrid vehicles and in various electric grid storage applications. In your submission, you suggest classifying this product under 3824.90.3900, Harmonized Tariff Schedule of the United States (HTSUS). However, lithium iron phosphate (CAS# 15365-14-7), is a separately defined inorganic compound and a double salt of an inorganic acid, which is provided for within heading 2842.
[1] Please importantly note that only the relevant portion of the related is displayed above. You may refer to the said customs ruling for the entire ruling explanation.
[1]. https://rulings.cbp.gov/ruling/N188896