Electrode material, paste for electrodes, and lithium ion battery
An electrode material includes an electrode active material having a carbonaceous film formed on a surface is used and which is capable of suppressing voltage drop when high-speed charge and discharge is carried out in a low-temperature environment. The electrode material has a particulate shape and is formed a carbonaceous film on surfaces of electrode active material particles. An average of discharge capacity ratios between a 35C discharge capacity at −10° C. of a single particle of the electrode material and a 1C discharge capacity at −10° C. of a single particle of the electrode material is 0.50 or more.
1. An electrode material, comprising:
electrode active material particles and a carbonaceous film provided on surfaces of the electrode active material particles, wherein the electrode active material particles having the carbonaceous film provided thereon form an electrode material having a particulate shape;
wherein an average of discharge capacity ratios between a 3C discharge capacity at −10° C. of a single particle of the electrode material and a 1C discharge capacity at −10° C. of a single particle of the electrode material is 0.50 or more,
an XRD (CuKα ray source) peak of the (002) plane derived from graphene layers in the carbonaceous film is 2Θ=25.7° or less, and
an average of plane intervals between (002) planes in the graphene layers is 0.3466 nm or more.
2. The electrode material according to claim 1 ,
wherein an inflection ratio of a lithium ion migration path in the carbonaceous film is in a range of 1.1 to 100.
3. The electrode material according to claim 1 ,
wherein the electrode active material particles have an olivine-type crystal structure.
4. The electrode material according to claim 1 ,
wherein a content rate of the carbonaceous film with respect to a total mass of the electrode material is in a range of 0.5% by mass to 5.0% by mass.
5. The electrode material according to claim 1 ,
wherein a powder resistance value of the electrode material is 300 Ω·cm or less.
6. The electrode material according to claim 1 ,
wherein a ratio between a powder resistance value (Ω·cm) of the electrode active material particles and a content rate (% by mass) of the carbonaceous film is 300 or less.
7. The electrode material according to claim 1 ,
wherein the electrode material is produced by the following steps (1) and (2),
(1) a slurry preparation step of preparing a slurry including the electrode active material particles and/or a precursor of the electrode active material particles, an organic compound i, and an organic compound ii, and
(2) a step of drying the slurry so as to generate a granulated body having a film including the organic compounds i and ii on a surface, firing the granulated body in a non-oxidative atmosphere so as to remove the organic compound ii from the film and carbonize the organic compound i, thereby forming a carbonaceous film made of a carbonaceous material coming from the organic compound i on the surface of the granulated body.
8. The electrode material according to claim 1 ,
wherein the XRD (CuKα ray source) peak of the (002) plane derived from graphene layers in the carbonaceous film is 2Θ=25.4° to 24.0°.
9. The electrode material according to claim 1 ,
wherein the average of the plane intervals between (002) planes in the graphene layers is 0.350 nm to 0.370 nm.
10. The electrode material according to claim 1 ,
wherein an average thickness of the carbonaceous film is 0.5 nm to 20 nm.
11. The electrode material according to claim 1 ,
wherein the average of discharge capacity ratios between a 3C discharge capacity at −10° C. of a single particle of the electrode material and a 1C discharge capacity at −10° C. of a single particle of the electrode material is 0.60 or more.
12. The electrode material according to claim 1 ,
wherein the average of discharge capacity ratios between a 3C discharge capacity at −10° C. of a single particle of the electrode material and a 1C discharge capacity at −10° C. of a single particle of the electrode material is in a range of 0.65 to 0.90.
13. The electrode material according to claim 1 ,
wherein an inflection ratio of a lithium ion migration path in the carbonaceous film is in a range of 1.3 to 50.
14. The electrode material according to claim 1 ,
wherein an inflection ratio of a lithium ion migration path in the carbonaceous film is in a range of 1.5 to 10.
15. The electrode material according to claim 1 ,
wherein an average thickness of the carbonaceous film is 1 nm to 10 nm.
16. The electrode material according to claim 1 ,
wherein an average thickness of the carbonaceous film is 1 nm to 5 nm.
17. The electrode material according to claim 1 ,
wherein a coating proportion of the surface of the electrode material particles with the carbonaceous film is at least 50%.
18. The electrode material according to claim 1 ,
wherein a coating proportion of the surface of the electrode material particles with the carbonaceous film is at least 80%.
19. Paste for electrodes comprising: the electrode material according to claim 1 and a binding agent.
20. A lithium ion battery comprising:
a positive electrode collector having an electrode material layer formed of the paste for electrodes according to claim 19 on a metal foil.