Cathode material for lithium-ion secondary battery, method for manufacturing same, electrode for lithium-ion secondary battery, and lithium-ion secondary battery

1. A cathode material for a lithium-ion secondary battery made of agglomerated particles formed by agglomeration of a plurality of primary particles of a cathode active material represented by General Formula (1) below which are coated with a carbonaceous film,

wherein a particle diameter (D90) at a cumulative percentage of 90% in a cumulative particle size distribution of the cathode material is 3.0 μm or more and 15 μm or less,

Li x A y D z PO 4   (1)

 wherein

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;

wherein a film thickness change percentage of the cathode mixture layer before and after a pressing according to the following measuring method is 30% or less,

wherein in the measuring method,

(A) the cathode material, a conductive auxiliary agent, and a binding agent in a weight ratio of cathode material/conductive auxiliary agent/binding agent=90:5:5 are mixed to produce a slurry, then

(B) the slurry is applied on a 30 μm-thick aluminum current collector and dried to obtain a cathode mixture layer having an application width of 40 mm, then

(C) the film thickness change percentage is calculated from the thickness of the cathode excluding the thickness of the current collector after drying and the thickness of the current collector when being pressed at a total applied pressure of 5 t/250 mm using the following expression:

Film thickness change percentage (%)=100×(thickness of the cathode after drying−thickness of the cathode when being pressed at a total applied pressure of 5 t/250 mm)/the thickness of the cathode after drying.

2. The cathode material for a lithium-ion secondary battery according to claim 1 ,

wherein an oil absorption amount for which N-methyl-2-pyrrolidone is used is 50 ml/100 g or less.

3. The cathode material for a lithium-ion secondary battery according to claim 1 ,

wherein a specific surface area of the cathode material is 10 m 2 /g or more and 25 m 2 /g or less, and a powder resistance value is 500 Ω·cm or less.

4. A method for manufacturing the cathode material for a lithium-ion secondary battery according to claim 1 , the method comprising:

a manufacturing step of a cathode active material represented by General Formula (1) and a cathode active material precursor;

a slurry preparation step of preparing a slurry by mixing at least one cathode active material raw material selected from the group consisting of the cathode active material and the cathode active material precursor obtained in the above-described step and water;

a granulation step of obtaining a granulated body by adding an agglomeration-maintaining agent to the slurry obtained in the above-described step; and

a calcination step of mixing an organic compound which is a carbonaceous film precursor into the granulated body obtained in the above-described step in a dry manner and calcinating the obtained mixture in a non-oxidative atmosphere.

5. An electrode for a lithium-ion secondary battery, comprising:

an aluminum current collector; and

a cathode mixture layer formed on the aluminum current collector,

wherein the cathode mixture layer includes the cathode material for a lithium-ion secondary battery according to claim 1 .

6. The electrode for a lithium-ion secondary battery according to claim 5 ,

wherein an electrode density of the cathode mixture layer after drying is 1.0 g/cm 3 or more.

7. A lithium-ion secondary battery, comprising:

a cathode;

an anode; and

an electrolyte,

wherein the cathode includes the electrode for a lithium-ion secondary battery according to claim 5 .