Tangent gradient concentration material for battery, digital gradient concentration material for battery
The invention provides a cathode active material having a discrete change in concentrations of a first base region and a second pulse region. Also provided is a method for preparing a cathode active material, the method having the steps: supplying chelating agent, aqueous basic solution and a first aqueous metal salt solution to a reactor to create a base region; supplying a second aqueous metal-salt solution to a reactor to form a pulse region, wherein the second aqueous metal-salt solution is intermittently or continuously added during or after the creation of the base region; thermally treating the base region and the pulse region to create active metal precursors; mixing the precursors with lithium salt to produce a mixture; and thermally treating the mixture.
1. A cathode active material comprising secondary particles made up of primary particles wherein each of the primary particles exhibit a concentration change in constituents such that the cathode active material has a non-linear change in concentrations of constituents of a first base region and a second pulse region of the cathode active material wherein nickel is one of the constituents of the cathode active material and overall nickel content of the cathode active material is about 80 weight percent or more wherein the base region has the formula Li a1 Ni x1 Co y1 Mn z1 M w1 O 2+δ1 and M is a metal selected from the group consisting of B, C, Na, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Zr, Nb, Mo, Ag, Sn, Ba or a combination thereof, and 0.75≤a1≤2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤1, 0≤δ1≤1, 0≤x1+y1+z1≤1and the pulse region has the formula Li a2 Ni x2 Co y2 Mn z2 M w2 O 2+62 and M is a metal selected from the group consisting of B, C, Na, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Zr, Nb, Mo, Ag, Sn, Ba or a combination thereof, and 0≤a2≤2, 0≤x2≤1, 0≤y2≤1, 0≤z2≤1, 0≤w2≤1, 0≤δ2≤1, 0≤x2+y2+z2≤1, wherein each of the primary particles has a primary particle base region and a primary particle pulse region and wherein the concentration of constituents of the primary particle base region changes in a radial and circumferential direction as the composition of the primary particle pulse region increases.
2. The cathode active material as recited in claim 1 wherein the primary particles are between 0.1 μm and 1 μm in diameter.
3. The cathode active material as recited in claim 1 wherein the change in concentrations of constituents of the primary particles_exhibits a shape selected from the group consisting of a sine wave, a square, step, triangle, sawtooth, an exponential curve, and combinations thereof.
4. The cathode active material as recited in claim 1 wherein the base region comprises between 50 and 95 weight percent of the cathode active_material and the pulse region comprises between 5 and 50 weight percent of the cathode active material.
5. The cathode active material as recited in claim 1 wherein the secondary particles each have a center and a surface and the concentration of the constituents of the pulse region increases from the center to the surface while the concentration of the constituents of the base region decreases from the center to the surface.
6. The cathode active material as recited in claim 1 comprising particles having a shape selected from the group consisting of spherical, nonspherical, elliptical, oval, convex, concave, and combinations thereof.
7. The cathode active material as recited in claim 2 wherein the pulse region surrounds the base region formed by an agglomeration of non-spherical primary particles, the concentration of the base region decreases in a radial and circumferential direction as the composition of the pulse region increases, and the composition of the pulse region changes in the circumferential direction at the same particle radius.
8. The cathode active material particle as recited in claim 5 wherein the shape of the secondary particles are spherical, non-spherical, elliptical, elliptical, convex, concave, clustered, or a combination thereof and have different sizes.
9. The cathode active material_as recited in claim 5 , wherein the secondary particles have an average particle size of 4 to 20 μm and a particle size distribution of (D90−D10)/D50 of 0.2 to 3.
10. The cathode active material as recited in claim 2 wherein the primary particle has an average particle size less than 1 micron and a particle size distribution of (D90−D10)/D50 of 0.2 to 2.
11. The cathode active material as recited in claim 2 wherein the primary particle has a particle size between 200 nm and 600 nm.
12. The cathode active material as recited in claim 1 wherein a first lithium concentration in the pulse region is equal to or smaller than a second_lithium concentration in the base region.
13. The cathode active material as recited in claim 1 comprising particles each having a center and a surface, wherein each particle includes the second pulse region defining multiple pulse subregions.
14. The cathode active material as recited in claim 13 wherein the pulse subregions have the same, decreasing, increasing, or a combination of thicknesses from the center of the particle toward the surface of the particle.
15. The cathode active material as recited in claim 2 wherein the primary particle defines a shape selected from the group consisting of a leaf, needle, plate, polyhedron, sloped polyhedron, slanted polyhedron, curved polyhedron, ellipse, and combinations thereof.