Active material, battery, and method for manufacturing electrode

1. An active material for a nonaqueous electrolyte secondary battery comprising:

first particles; and

second particles scattered on the surfaces of the first particles,

wherein the circularity of the first particles with the second particles scattered thereon is 0.800 to 0.950; and

the ratio r1/r2 of the average particle diameter r1 of the second particles to the average particle diameter r2 of the first particles is 1/20 to 1/2.

2. The active material for a nonaqueous electrolyte secondary battery according to claim 1 ,

wherein the first particles and the second particles contain a lithium compound oxide having a mean composition represented by formula (1), (2), or (3):

Li p Ni (1-q-r) Mn q M1 r O (2-y) X z   (1)

wherein M1 represents at least one element selected from Groups II to XV in the periodic table excluding nickel (Ni) and manganese (Mn), X represents at least one element of Groups XVI and XVII in the periodic table excluding oxygen (O), p, q, r, y, and z are values within the ranges of 0≦p≦1.5, 0≦q≦1.0, 0≦r≦1.0, −0.10≦y≦0.20, and 0≦z≦0.2, respectively, a lithium composition depends on a state of charging and discharging, and a value of p indicates a value in a state of full discharging;

Li a Co (1-b) M2 b O (2-c)   (2)

wherein M2 represents at least one element selected from the group consisting of vanadium (V), copper (Cu), zirconium (Zr), zinc (Zn), magnesium (Mg), aluminum (Al), gallium (Ga), yttrium (Y), and iron (Fe), a, b, and c are values within the ranges of 0.9≦a≦1.1, 0≦b≦0.3, and −0.1≦c≦0.1, respectively, a lithium composition depends on a state of charging and discharging, and a value of a indicates a value in a state of full discharging;

Li w Ni x Co y Mn z M3 (1-x-y-z) O (2-v)   (3)

wherein M3 represents at least one element selected from the group consisting of vanadium (V), copper (Cu), zirconium (Zr), zinc (Zn), magnesium (Mg), aluminum (Al), gallium (Ga), yttrium (Y), and iron (Fe), v, w, x, y, and z are values within the ranges of −0.1≦v≦0.1, 0.9≦w≦1.1, 0<x<1, 0<y<1, 0<z<0.5, 0<1-x-y-z, respectively, a lithium composition depends on a state of charging and discharging, and a value of w indicates a value in a state of full discharging.

3. The active material for a nonaqueous electrolyte secondary battery according to claim 2 ,

wherein at least one element different from a main transition metal element contained in the first particles and the second particles is present on at least a portion of the surface of each of the first particles and the second particles.

4. The active material for a nonaqueous electrolyte secondary battery according to claim 3 ,

wherein the element different from the main transition metal contained in the first particles is at least one of nickel (Ni), manganese (Mn), magnesium (Mg), fluorine (F), and phosphorous (P).

5. The active material for a nonaqueous electrolyte secondary battery according to claim 1 ,

wherein a specific surface area of the first particles with the second particles scattered thereon is 0.1 m 2 /g to 0.5 m 2 /g.

6. The active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein a molar ratio of first particles to second particles ranges from 1:1 to 1:30.

7. The active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein the active material has a void ratio of 20% or less.

8. An electrode for a nonaqueous electrolyte secondary battery comprising:

a current collector; and

an active material layer formed on at least one surface of the current collector,

wherein the active material layer includes an active material comprising:

first particles; and

second particles scattered on the surfaces of the first particles,

wherein the circularity of the first particles with the second particles scattered thereon is 0.800 to 0.950; and

the ratio rl/r2 of the average particle diameter rl of the second particles to the average particle diameter r2 of the first particles is 1/20 to 1/2 .

9. The electrode for a nonaqueous electrolyte secondary battery according to claim 8 , wherein the electrode is a cathode.

10. The electrode for a nonaqueous electrolyte secondary battery according to claim 8 , wherein a specific surface area of the first particles with the second particles scattered thereon is 0.1 m 2 /g to 0.5 m 2 /g.

11. The electrode for a nonaqueous electrolyte secondary battery according to claim 8 , wherein a molar ratio of first particles to second particles ranges from 1:1to 1:30 .

12. A nonaqueous electrolyte secondary battery comprising:

a cathode;

an anode; and

a separator provided therebetween,

wherein at least one of the cathode and the anode includes a current collector and an active material layer formed on at least one surface of the current collector,

wherein the active material layer includes an active material comprising:

first particles; and

second particles scattered on the surfaces of the first particles,

wherein the circularity of the first particles with the second particles scattered thereon is 0.800 to 0.950; and

the ratio rl/r2 of the average particle diameter rl of the second particles to the average particle diameter r2 of the first particles is 1/20 to 1/2.

13. The electrode for a nonaqueous electrolyte secondary battery according to claim 12 , wherein a specific surface area of the first particles with the second particles scattered thereon is 0.1 m 2 /g to 0.5 m 2 /g.

14. The electrode for a nonaqueous electrolyte secondary battery according to claim 12 , wherein a molar ratio of first particles to second particles ranges from 1:1to 1:30.