Negative electrode for secondary cell and secondary cell using the same
Since a first layer (a carbon layer 2 a ) whose chief ingredient is carbon and a second layer (Li absorbing layer 3 a ) containing particles having a theoretical capacity greater than that of graphite are formed on anode collector 1 a , high capacity and high operation voltage can be realized. Since a element having a theoretical capacity equal to or less than that of graphite is added to the particles constituting this second layer, expansion and contraction of volume according to the charge and discharge are suppressed. This enables capacity deterioration to be suppressed even though cycles go on.
1. An anode for a secondary battery comprising:
an anode active material layer which absorbs and discharges lithium ions, said anode active material layer comprising:
a first layer comprising carbon as a chief ingredient; and
a second layer comprising:
at least one first element having a theoretical capacity greater than a theoretical capacity of graphite; and
at least one second element which has a theoretical capacity equal to or less than the theoretical capacity of graphite,
wherein said second layer includes particles, and said particles include said first element and said second element.
2. The anode for the secondary battery according to claim 1 , wherein surfaces of said particles including said first element are coated with said second element.
3. The anode for the secondary battery according to claim 1 , wherein surfaces of said particles including said second element are coated with said first element.
4. The anode for the secondary battery according to claim 1 , wherein said particles are formed by any of a CVD method, a deposition method, a sputtering method, a mechanical milling method and a mechanical alloy method.
5. The anode for the secondary battery according to claim 1 , wherein said second element comprises at least one element selected from the group consisting of C, Fe and Cu.
6. The anode for the secondary battery according to claim 1 , wherein said first element comprises at least one element selected from the group consisting of Si, Ge, Sn, Al, Pb, Pd, Ag, In and Cd.
7. The anode for the secondary battery according to claim 1 , further comprising:
a layer comprising Li or a Li compound.
8. The anode for the secondary battery according to claim 7 , wherein said Li compound includes LiF or Li 2 O.
9. The anode for the secondary battery according to claim 5 , wherein said first element comprises at least one element selected from the group consisting of Si, Ge, Sn, Al, Pb, Pd, Ag, In and Cd.
10. The anode for the secondary battery according to claim 9 , further comprising:
a layer comprising Li or a Li compound.
11. The anode for the secondary battery according to claim 10 , wherein said Li compound includes LiF or Li 2 O.
12. The anode for the secondary battery according to claim 1 , further comprising a third layer comprising Li or Li compound.
13. The anode for the secondary battery according to claim 12 , wherein said Li compound comprises LiF or Li 2 O.
14. The anode for the secondary battery according to claim 12 , further comprising a fourth layer comprising a lithium ion conductive property.
15. The anode for the secondary battery according to claim 14 , wherein said fourth layer is formed between said first layer and said third layer.
16. The anode for the secondary battery according to claim 14 , wherein said fourth layer comprises materials selected from the group consisting of Si, Sn, DLC, a Li 2 O—SiO 2 based compound, a Li 2 O—B 2 O 3 —SiO 2 based compound, a Li 2 O—B 2 O 3 —P 2 O 5 based compound, a Li 2 O—WO 3 based compound, Li 2 O—P 2 O 5 —SiO 2 based compound, and a Li 2 O—B 2 O 3 based compound.
17. The anode for the secondary battery according to claim 1 , wherein a volume A of said at least one first element and a volume B of said at least one second element satisfy 0.001≦B/(A+B)≦0.5.
18. The anode for the secondary battery according to claim 1 , further comprising a collector placed adjacent to said first layer.
19. The anode for the secondary battery according to claim 1 , further comprising a collector placed adjacent to said second layer.