Lithium-ion secondary battery, battery apparatus, electric apparatus, preparation method for positive electrode active material, and preparation method for positive electrode plate

A lithium-ion secondary battery, comprising a positive electrode plate, a negative electrode plate, and an electrolyte, wherein,

• the positive electrode plate comprises a positive electrode current collector, a positive electrode film layer arranged on at least one side of the positive electrode current collector, and a base coating layer arranged between the positive electrode film layer and the positive electrode current collector, the base coating layer comprises carbon-based particles, and a distribution density of the carbon-based particles having a particle size greater than 100 nm in the base coating layer is less than or equal to 10 pcs/10 μm;
• the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises lithium-containing transition metal phosphate particles with a surface at least partially provided with a carbon coating material;
• in a section of the positive electrode film layer in a thickness direction of the electrode plate, an area proportion of particles having a particle size of 1.5 μm to 5 μm is 9.0% to 20.0%, an area proportion of particles having a particle size greater than or equal to 1 μm and less than 1.5 μm is greater than or equal to 16.0% and less than or equal to 20.0%,
• in a cumulative distribution curve of a C value of a graphitization degree obtained in a mapping mode by a laser confocal microscope Raman spectrometer for the positive electrode film layer, a median C50 of the graphitization degree is 0.97 to 1.13, wherein the C value of the graphitization degree is IG/ID, IG represents a G-band intensity of a Raman spectrum at 1580±100 cm−1, and ID represents a D-band intensity of the Raman spectrum at 1350±100 cm−1, a concentration degree (C90−C10)/C50 of the C value is 0.01 to 0.04;
• and
• when the lithium-ion secondary battery is in a fully discharged state, a compaction density of the positive electrode film layer is 2.51 g/cm3 to 2.73 g/cm3.