Abstract: The present disclosure relates to a lithium-ion secondary battery, a battery apparatus, an electrical apparatus, and preparation methods for a positive electrode active material and a positive electrode plate. The battery includes a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate comprises a current collector and a film layer disposed on at least one side of the collector. The film layer comprises a positive electrode active material including lithium-containing transition metal phosphate particles, at least part of the surfaces of which are coated with a carbon material. In a cross-section along the electrode plate thickness direction, the DA90 of the particles ranges from 1400 nm to 2100 nm, and the particle size concentration ratio (DA90?DA10)/DA50 ranges from 1.855 to 2.375, wherein DA90, DA50, and DA10 respectively denote the particle sizes corresponding to 90%, 50%, and 10% of the area cumulative distribution.