Non-aqueous electrolyte secondary battery-use cathode material, production method therefor, non-aqueous electrolyte secondary battery-use cathode and non-aqueous electrolyte secondary battery using the cathode material

1. A nonaqueous electrolyte secondary battery negative electrode material, characterized by comprising:

graphite particles, each having a structure where a plurality of flat graphite fine particulate assembles or bonds non-parallel with each other, each of the graphite particles having an aspect ratio of 5 or less and a volume of fine pores in the range of 10 to 10 5 nm in a volume of 400 to 2000 cm 3 /kg, and each of the graphite particles having a surface; and

a layer of carbon formed on the surface of each of the graphite particles,

wherein a ratio (by weight ratio) of the layer of carbon to a respective graphite particle is in the range of 0.003 to 0.01, and

wherein an average particle diameter (50% D) is 10 μm or more and 50 μm or less, the true specific gravity is 2.22 or more, the bulk density is 780 kg/m 3 or more and 1000 kg/m 3 or less, the specific surface area measured by a BET method is 2.0 m 2 /g or more and 5.0 m 2 /g or less, and, in a Raman spectrum analysis with argon laser light of a wavelength of 5145 Å, an R value expressed by R=I1350/I1580 (in Raman spectrum, I1580 denotes an intensity of a peak P1 in the range of 1580 to 1620 cm −1 and I1350 denotes an intensity of a peak P2 in the range of 1350 to 1370 cm4) is less than 0.2.

2. The nonaqueous electrolyte secondary battery negative electrode material of claim 1 , characterized in that the viscosity of slurry measured under the conditions below is 0.5 Pa·s or more and 4.0 Pa·s or less;

1) Slurry Preparation Conditions

binder/(binder+negative electrode material)=0.10 (by weight ratio)

(binder+negative electrode material)/(binder+negative electrode material+solvent)=0.45 (by weight ratio)

binder: polyvinylidene fluoride (intrinsic viscosity: 1.1 dl/g) and

solvent: N-methyl-2-pyrohlidone

2) Viscosity Measurement Conditions

shearing speed: 4.0 sec −1 at 25° C.

3. The nonaqueous electrolyte secondary battery negative electrode material of claim 1 , characterized in that the bulk density (D1) under pressure of 33 MPa is 1850 kg/m 3 or more and a rate of variation of the bulk density when the pressure is released, which is represented by an equation below, is 0.3 or less;

Rate of variation of the bulk density when the pressure is released={ D 2− D 3}/ D 2

D2: bulk density under the pressure of 97 MPa, and

D3: bulk density when the pressure is released.

4. A nonaqueous electrolyte secondary battery negative electrode, which includes the negative electrode material of claim 1 .

5. A nonaqueous electrolyte secondary battery, having, as the negative electrode thereof, the nonaqueous electrolyte secondary battery negative electrode of claim 4 .

6. The nonaqueous electrolyte secondary battery negative electrode material of claim 1 , wherein said layer consists essentially of carbon.

7. The nonaqueous electrolyte secondary battery negative electrode material of claim 1 , wherein said layer consists of carbon.

8. The nonaqueous electrolyte secondary battery negative electrode material of claim 1 , wherein the layer of carbon covers the respective graphite particle.