Lithium-ion secondary battery, anode for lithium-ion secondary battery, power tool, electric vehicle and energy storage system

1. A lithium-ion secondary battery comprising:

a cathode;

an anode; and

an electrolytic solution,

wherein,

the anode includes an anode active material layer including a plurality of anode active material particles,

each anode active material particle includes a core section and a coating section applied to a part or all of a surface of the core section, and

the core section includes a silicon-based material SiO x , where 0≦x<0.5, and the coating section includes an amorphous or low-crystalline silicon-based material SiO y , where 0.5≦y≦0.9.

2. The lithium-ion secondary battery according to claim 1 , wherein

in the silicon-based material included in the coating section, the amorphous silicon-based material includes only an amorphous region and the low-crystalline silicon-based material includes an amorphous region and crystal grains.

3. The lithium-ion secondary battery according to claim 2 , wherein

in the low-crystalline silicon-based material included in the coating section, an average area proportion of the crystal grains corresponding to (111) plane and (220) plane of silicon (Si) is 35% or less.

4. The lithium-ion secondary battery according to claim 2 , wherein

in the low-crystalline silicon-based material included in the coating section, an average particle diameter of the crystal grains corresponding to (111) plane and (220) plane of silicon is 55 nm or less.

5. The lithium-ion secondary battery according to claim 2 , wherein

in the low-crystalline silicon-based material included in the coating section, in the crystal grains corresponding to (111) plane and (220) plane of silicon, when the coating section is divided into two equal parts in a thickness direction, an average area proportion and an average particle diameter of the crystal grains in an inner part are equal to or larger than those in an outer part.

6. The lithium-ion secondary battery according to claim 2 , wherein

in the low-crystalline silicon-based material included in the coating section, the crystal grains are dotted in the amorphous region.

7. The lithium-ion secondary battery according to claim 1 , wherein

the coating section is configured of a plurality of layers.

8. The lithium-ion secondary battery according to claim 1 , wherein

in the core section, a half-width (2θ) of a diffraction peak corresponding to (111) crystal plane of silicon obtained by X-ray diffraction is 20° or less, and a crystallite size corresponding to the (111) crystal plane is 10 nm or over.

9. The lithium-ion secondary battery according to claim 1 , wherein

a median diameter of the core section is within a range of 0.5 μm to 20 μm both inclusive.

10. The lithium-ion secondary battery according to claim 1 , wherein

an average thickness of the coating section is within a range of 1 nm to 5000 nm both inclusive.

11. The lithium-ion secondary battery according to claim 1 , wherein

an average coverage of the coating section is 30% or over.

12. The lithium-ion secondary battery according to claim 1 , wherein

the core section includes a simple substance of silicon.

13. The lithium-ion secondary battery according to claim 1 , wherein

the core section includes iron (Fe) and the iron content is 0.01 wt % or over.

14. The lithium-ion secondary battery according to claim 1 , wherein

the anode includes the anode active material layer on an anode current collector, and the anode current collector includes carbon (C) and sulfur (S), and the contents of carbon and sulfur are 100 ppm or less.

15. The lithium-ion secondary battery according to claim 1 , wherein

the anode active material layer includes a carbon material.

16. The lithium-ion secondary battery according to claim 1 , wherein

the core section includes aluminum (Al) and the aluminum content, expressed as an atomic ratio excluding oxygen (O), is within a range of 0.1 at % to 50 at % both inclusive.

17. The lithium-ion secondary battery according to claim 16 , wherein

the core section includes one or more kinds of materials selected from the group consisting of chromium (Cr), iron (Fe), and nickel (Ni), and the content thereof, expressed as an atomic ratio excluding oxygen (O), is within a range of 1 at % to 50 at % both inclusive.

18. The lithium-ion secondary battery according to claim 17 , wherein

the core section includes one or more kinds of materials selected from the group consisting of boron (B), magnesium (Mg), calcium (Ca), titanium (Ti), vanadium (V), manganese (Mn), cobalt (Co), copper (Cu), germanium (Ge), yttrium (Y), zirconium (Zr), molybdenum (Mo), silver (Ag), indium (In), tin (Sn), antimony (Sb), tantalum (Ta), tungsten (W), lead (Pb), lanthanum (La), cerium (Ce), praseodymium (Pr) and neodymium (Nd), and the content thereof, expressed as an atomic ratio excluding oxygen (O), is within a range of 0.01 at % to 30 at % both inclusive.

19. The lithium-ion secondary battery according to claim 18 , wherein

the content of silicon, expressed as an atomic ratio excluding oxygen (O), in the core section is within a range of 20 at % to 80 at % both inclusive.

20. The lithium-ion secondary battery according to claim 16 , wherein

in the core section, a half-width (2θ) of a diffraction peak corresponding to (111) crystal plane of silicon obtained by X-ray diffraction is 0.6° or over, and a crystallite size corresponding to the (111) crystal plane is 90 nm or less.

21. The lithium-ion secondary battery according to claim 1 , wherein

a bonding state, expressed as a valence number, of silicon atoms to oxygen atoms in the amorphous silicon-based material included in the coating section is a mixed state of zero-valence (Si 0+ ), monovalence (Si 1+ ), divalence (Si 2+ ), trivalence (Si 3+ ) and tetravalence (Si 4+ ).

22. The lithium-ion secondary battery according to claim 21 , wherein

an abundance ratio, expressed as an atomic ratio, of the bonding state of silicon atoms satisfies a relationship of Si 0+ ≦Si 1+ +Si 2+ +Si 3+ +Si 4+ .

23. The lithium-ion secondary battery according to claim 22 , wherein

the abundance ratio of the bonding state of silicon atom satisfies relationships of Si 1+ ≦Si 3+ , Si 2+ −Si 3+ , Si 1+ ≦Si 4+ and Si 2+ ≦Si 4+ .

24. The lithium-ion secondary battery according to claim 22 , wherein

the abundance ratio of Si 4+ is 20 at % or over.

25. The lithium-ion secondary battery according to claim 24 , wherein

the abundance ratio of Si 4+ is 30 at % or over.

26. The lithium-ion secondary battery according to claim 1 , wherein

each anode active material particle includes an additional coating film applied to a part or all of the surface of the coating section and having a lower electrical resistance than the core section and the coating section.

27. A lithium-ion secondary battery anode comprising:

an anode active material layer including a plurality of anode active material particles,

wherein,

each anode active material particle includes a core section and a coating section applied to a part or all of a surface of the core section, and

the core section includes a silicon-based material SiO x , where 0≦x<0.5, and the coating section includes an amorphous or low-crystalline silicon-based material SiO y , where 0.5≦y≦0.9.

28. A power tool activated by a lithium-ion secondary battery as a power supply, the lithium-ion secondary battery including a cathode, an anode, and an electrolytic solution, the anode comprising:

an anode active material layer including a plurality of anode active material particles,

wherein,

each anode active material particle includes a core section and a coating section applied to a part or all of a surface of the core section, and

the core section includes a silicon-based material SiO x , where 0≦x<0.5, and the coating section includes an amorphous or low-crystalline silicon-based material SiO y , where 0.5≦y≦0.9.

29. An electric vehicle activated by a lithium-ion secondary battery as a power supply, the lithium-ion secondary battery including a cathode, an anode, and an electrolytic solution, the anode comprising:

an anode active material layer including a plurality of anode active material particles,

wherein,

each anode active material particle includes a core section and a coating section applied to a part or all of a surface of the core section, and

the core section includes a silicon-based material SiO x , where 0≦x<0.5, and the coating section includes an amorphous or low-crystalline silicon-based material SiO y , where 0.5≦y≦0.9.

30. An energy storage system using a lithium-ion secondary battery as a power storage source, the lithium-ion secondary battery including a cathode, an anode, and an electrolytic solution, the anode comprising:

an anode active material layer including a plurality of anode active material particles,

wherein,

each anode active material particle includes a core section and a coating section applied to a part or all of a surface of the core section, and

the core section includes a silicon-based material SiO x , where 0≦x<0.5, and the coating section includes an amorphous or low-crystalline silicon-based material SiO y , where 0.5≦y≦0.9.