Current collector, negative electrode and battery

1. A battery comprising:

a positive electrode, and

a negative electrode,

wherein,

the positive electrode and the negative electrode are spirally wound to form a wound body,

the negative electrode comprises (1) an active material layer having an active material including at least Si or Sn, and (2) a negative electrode current collector having (a) a first principal plane facing outward and corresponding to an outer face of the wound body and (b) a second principal plane facing inward and corresponding to an inner face of the wound body,

the first principal plane has a first surface roughness in a range of 0.2 μm to 3.0 μm, both inclusive,

the negative electrode current collector has a thickness in a range of 5 μm to 30 μm, both inclusive,

a difference between the first surface roughness of the first principal plane of the negative current collector and a second surface roughness of the second principal plane of the negative electrode current collector is greater than 0.05 μm, and

each of the first surface roughness and the second surface roughness is an arithmetic mean surface roughness R a .

2. A battery according to claim 1 , wherein the first surface roughness of the first principal plane of the negative electrode current collector is higher than the second surface roughness of the second principal plane of the negative electrode current collector.

3. A battery according to claim 1 , wherein at least one of the active material layer on the first principal plane of the negative electrode current collector or the active material layer on the second principal plane of the negative electrode current collector has a thickness of 70 μm or more at full discharge.

4. A battery according to claim 1 , wherein the active material layer of the negative electrode comprises a graphite material.

5. A battery according to claim 1 , wherein the positive electrode comprises a lithium transition metal composite oxide including a metal element selected from the group consisting of cobalt, nickel, and manganese.

6. A battery according to claim 1 , wherein the active material layer of the negative electrode has a peak in a diffraction pattern obtained by X-ray diffraction analysis using CuKα of 30° to 60°, and half the width of the peak is 0.5° or more at 2θ.

7. A battery according to claim 1 , wherein the active material has particles with diameters in the range of 0.1 μm to 25 μm, both inclusive.

8. A battery according to claim 1 further comprises an electrolyte comprising one or more of propylene carbonate, ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, .gamma.-butyrolactone, tetrahydrofuran, 2-methyl tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propylnitrile, anisole, acetic ester, or propionic acid ester.

9. A battery according to claim 1 further comprises an electrolyte salt, wherein the electrolyte salt comprises at least one of LiPF 6 or LiBF 4 .

10. An electronic apparatus comprising the battery according to claim 1 .

11. A negative electrode spirally wound to form a wound body and comprising:

an active material layer having an active material with at least Si or Sn, and

a negative electrode current collector having (a) a first principal plane facing outward and corresponding to an outer face of the wound body and (b) a second principal plane facing inward and corresponding to an inner face of the wound body,

wherein,

the first principal plane has a first surface roughness in a range of 0.2 μm to 3.0 μm, both inclusive,

the negative electrode current collector has a thickness in a range of 5 μm to 30 μm, both inclusive,

a difference between a first surface roughness of the first principal plane of the negative current collector and a second surface roughness of the second principal plane of the negative electrode current collector is greater than 0.05 μm, and

each of the first surface roughness and the second surface roughness is an arithmetic mean surface roughness R a .