Electrode material and method for producing the same
The present invention provides an electrode material in which unevenness in a supporting amount of a carbonaceous film is less when using an electrode-active material having a carbonaceous film on a surface thereof as the electrode material, and which is capable of improving conductivity, and a method for producing the electrode material. The electrode material includes an aggregate formed by aggregating an electrode-active material in which a carbonaceous film is formed on a surface. In the electrode material, an average particle size of the aggregate is 0.5 to 100 μm, a volume density of the aggregate is 50 to 80 vol % of a volume density in a case in which the aggregate is a solid, and 80% or more of the surface of the electrode-active material is covered with the carbonaceous film. Alternatively, the electrode material includes an aggregate formed by aggregating electrode-active material particles in which a carbonaceous film is formed on a surface. In the electrode material, an average particle size of the aggregate is 0.5 to 100 μm, a pore size (D50) when an accumulated volume percentage of a pore size distribution of the aggregate is 50% is 0.1 to 0.2 μm, and porosity of the aggregate is 15 to 50 vol % with respect to a volume in a case in which the aggregate is a solid.
1. A positive electrode material, comprising:
an aggregate formed by aggregating electrode-active material particles having a carbonaceous film formed on a surface,
wherein an average particle size of the aggregate is 0.5 to 100 μm,
a pore size (D50) when an accumulated volume percentage of a pore size distribution of the aggregate is 50% is 0.1 to 0.2 μm,
porosity of the aggregate is 15 to 50 vol % with respect to a volume of an aggregate in which a void is not present,
the aggregate has a plurality of voids at the inside, including a shell-like aggregate having a void at the inside, and a ratio of an average film thickness of the carbonaceous film in an outer peripheral portion and an inner peripheral portion of an outer shell of the shell-like aggregate (a thickness of the carbonaceous film in the inner peripheral portion/a thickness of the carbonaceous film in the outer peripheral portion) is 0.7 to 1.3,
a tap density of the aggregate is 1.0 to 1.5 g/cm 3 ,
the electrode-active material comprises Li x A y D z PO 4 as a main component, wherein A is one or more selected from the group consisting of Co, Mn, Ni, Fe, Cu, and Cr; D is one or more selected from the group consisting of Mg, Ca, S, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare-earth elements; 0<x<2; 0<y<1.5; and 0<z<1.5,
an amount of carbon in the carbonaceous film is 0.8 to 2.5 parts by mass on the basis of 100 parts by mass of the electrode-active material,
80% or more of the surface of the electrode-active material is covered with the carbonaceous film, and
an average particle size of primary particles of the electrode-active material particles is 0.02 to 5 μm.
2. The positive electrode material according to claim 1 , wherein the aggregate has a structure in which the electrode-active materials having the carbonaceous film formed on a surface thereof are aggregated in a point contact state, and thus a contact portion of the electrode-active materials forms a neck shape, whereby channel-shaped voids inside the aggregate have a three-dimensionally expanded structure.
3. The positive electrode material according to claim 1 , wherein the aggregate is a shell-like aggregate and the size of the void that is formed inside the aggregate is 80% or less of a diameter of aggregate particles.
4. The positive electrode material according to claim 1 , wherein the electrode active material has a spherical shape.
5. A method for producing a positive electrode material according to claim 1 , comprising:
spraying and drying slurry which contains an electrode-active material or a precursor of the electrode-active material, and an organic compound, and in which a ratio (D90/D10) of a particle size (D90) when an accumulated volume percentage of a particle size distribution of the electrode-active material or the precursor of the electrode-active material is 90% to a particle size (D10) when the accumulated volume percentage is 10% is 5 to 30; and
baking the resultant dried product that is obtained at 500° C. to 1,000° C. in a non-oxidizing atmosphere to obtain the electrode material;
wherein the electrode-active material comprises Li x A y D z PO 4 as a main component, wherein A is one or more selected from the group consisting of Co, Mn, Ni, Fe, Cu, and Cr; D is one or more selected from the group consisting of Mg, Ca, S, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare-earth elements; 0<x<2; 0<y<1.5; and 0<z<1.5.
6. The method for producing a positive electrode material according to claim 5 , wherein the ratio (D90/D10) of D90 to D10 of a particle size distribution of the electrode-active material or the precursor of the electrode-active material is 7 to 25.