Secondary battery, battery pack, electronic apparatus, electric tool, electric vehicle, and power storage system

1. A secondary battery comprising:

a spirally wound electrode body in which a positive electrode and a negative electrode are laminated via a separator and spirally wound with a coil opening portion of the spirally wound electrode body as a center so that the positive electrode is arranged more to an inner circumference side than the negative electrode,

wherein the positive electrode includes:

an inner circumference side positive electrode active material layer formed on an inner circumference side of a positive electrode current collector;

an outer circumference side positive electrode active material layer formed on an outer circumference side of the positive electrode current collector; and

a single side active material layer formation region in which only the outer circumference side positive electrode active material layer is formed on the positive electrode collector,

wherein the single side active material layer formation region is formed on an end portion of the positive electrode current collector,

wherein a ratio A/(A+B) of an area density A (mg/cm 2 ) of the inner circumference side positive electrode active material layer and an area density B (mg/cm 2 ) of the outer circumference side positive electrode active material layer, an inner diameter C (mm) of the coil opening portion, and a ratio D/E of a thickness D (μm) of the positive electrode and a thickness E (μm) of the positive electrode collector satisfy a relationship expressed in Formula 1 below, and

a length F (mm) of the single side active material layer formation region satisfies a relationship expressed in Formula 2 below:

0.380 ≦A /( A+B )≦[0.593−0.007×( D/E )]×(0.03× C+ 0.87)  (Formula 1)

wherein C is 2.5≦C≦4 and D/E is 13.333≦D/E≦20

[0.3×( D/E ) 2 −7×( D/E )+45]≦F≦50   (Formula 2).

2. The secondary battery according to claim 1 , which satisfies a relationship expressed by Formula 3 below

0.428 ≦A /( A+B )≦[0.593−0.007×( D/E )]×(0.03× C+ 0.87)  (Formula 3).

3. The secondary battery according to claim 1 , wherein the negative electrode includes a negative electrode active material that is able to absorb and discharge an electrode reactant and the negative electrode active material is a material that includes at least one of silicon (Si) and tin (Sn) as a constituent element.

4. The secondary battery according to claim 1 ,

wherein the negative electrode includes a negative electrode active material that is able to absorb and discharge an electrode reactant, and

the negative electrode active material includes tin, cobalt (Co), and carbon (C) as constituent elements, and is a material in which a content of the carbon is equal to or greater than 9.9 mass % and equal to or less than 29.7 mass %, a proportion of the cobalt to the total of the tin and the cobalt is equal to or greater than 20 mass % and equal to or less than 70 mass %, and a half-value width of a diffraction peak that is obtained by X-ray diffraction is equal to or greater than 1°, wherein diffraction angle 2 θ is equal to or greater than 20° and equal to or less than 50°.

5. The secondary battery according to claim 1 , which is a lithium ion secondary battery.

6. A battery pack comprising:

the secondary battery according to claim 1 ;

a control section that controls the secondary battery; and

an outer packaging that contains the secondary battery.

7. An electronic apparatus that is moveable with the secondary battery according to claim 1 as a power source.

8. An electric tool that is moveable with the secondary battery according to claim 1 as a power source.

9. An electric vehicle that operates with the secondary battery according to claim 1 as a power source.

10. A power storage system that uses the secondary battery according to claim 1 as a power storage source.

11. The secondary battery according to claim 1 , wherein the area density A of the inner circumference side positive electrode active material layer ranges from 26 to 51 mg/cm 2 and the area density B of the outer circumference side positive electrode active material layer ranges from 26 to 72 mg/cm 2 .