Cathode material for lithium-ion secondary battery, cathode for lithium-ion secondary battery, and lithium-ion secondary battery

A cathode material for a lithium-ion secondary battery comprising:

• active material particles including central particles represented by general formula LixAyDzPO4 (here, A represents at least one element selected from the group consisting of Co, Mn, Ni, Fe, Cu, and Cr, D represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, and Y, 0.9<x<1.1, 0<y≤1, 0≤z<1, and 0.9<y+z<1.1) and a carbonaceous film that coats surfaces of the central particles,
• wherein
• an average primary particle diameter of the cathode material is 10 nm or more and 400 nm or less,
• a BET specific surface area of the cathode material is 5 m2/g or more and 25 m2/g or less,
• an amount of carbon forming the carbonaceous film is 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the central particles,
• the cathode material is cracked particles which are formed by cracking agglomerates of primary particles,
• the cathode material has a peak of coarse particles and a peak of fine particles in a particle size distribution of the cathode material,
• a coarse particle ratio in the particle size distribution of the active material particles is 35% or more and 65% or less,
• a median diameter of the active material particles is 0.50 μm or more and 0.80 μm or less,
• a maximum value of fine particle area in the particle size distribution of the active material particles is 0.15 μm or more and 0.35 μm or less, and a maximum value of coarse particle area in the particle size distribution of the active material particles is 0.80 μm or more and 1.20 μm or less, and
• the cathode material has properties, wherein a viscosity of a cathode material paste is 5,000 mPa·s or less at a shear rate of 4.0 [1/s], wherein
• the cathode material paste is prepared by dissolving a mixture of the active material particles, a conductive auxiliary agent and a binder in which a mixing ratio thereof is 94:1:5 in terms of a mass ratio in a solvent so that the cathode material paste has a total solid content amount of 45% by mass,
• the shear rate is measured at a temperature of 25° C.,
• the binder is a polytetrafluoroethylene resin, a polyvinylidene fluoride resin or fluorine rubber, and
• the conductive auxiliary agent is at least one selected from the group consisting of particulate carbon, vapor-grown carbon fiber and fibrous carbon.