Positive electrode and lithium ion secondary battery

Patent metadata

Field	Value
Publication number	US-11539047-B2
Application number	US-201916295801-A
Country	US
Kind code	B2
Filing date	Mar 7, 2019
Priority date	Mar 12, 2018
Publication date	Dec 27, 2022
Grant date	Dec 27, 2022

Abstract

A positive electrode includes a positive electrode current collector, and a positive electrode active material layer that is provided on the positive electrode current collector and that includes a positive electrode active material, a conductive auxiliary agent, and a binder. A surface of the positive electrode active material layer has a reflectance Rc in a range of 2.0≤Rc≤12.0% at a wavelength of 550 nm. A lithium ion secondary battery includes: the positive electrode; a negative electrode including a negative electrode current collector and a negative electrode active material layer that is provided on the negative electrode current collector and that includes a negative electrode active material; a separator; and a nonaqueous electrolyte solution. A surface of the negative electrode active material layer has a reflectance Ra in a range of 7.5≤Ra≤16.0% at a wavelength of 550 nm.

First claim

What is claimed is:

1. A positive electrode comprising:
a positive electrode current collector; and
a positive electrode active material layer disposed on the positive electrode current collector and including:
a positive electrode active material;
a conductive auxiliary agent; and
a binder, wherein:
an electrolyte solution contacts a surface of the positive electrode active material layer;
the surface of the positive electrode active material, layer is a pressed surface that includes the positive electrode active material, the conductive auxiliary agent, and the binder, has a reflectance Rc in a range of 2.0≤Rc≤12.0% at a wavelength of 550 nm; and
the reflectance reflects a flatness of the pressed surface of the positive electrode active material layer.

2. The positive electrode according to claim 1 , wherein:
the positive electrode active material contains a compound expressed by the following formula (1) as a main component:
Li x Ni y M 1-y O z   (1)

where x, y, and z satisfy 0<x≤1.1, 0≤y<0.5, and 1.9≤z≤2.1, and M includes at least one kind selected from Co, Mn, Al, Fe, and Mg; and
the surface of the positive electrode active material layer has a reflectance Rc1 in a range of 8.0≤Rc1≤12.0% at a wavelength of 550 nm.

3. The positive electrode according to claim 2 , wherein the positive electrode active material layer has a density dc1 in a range of 3.1≤dc1≤4.1 g/cm 3 .

4. The positive electrode according to claim 2 , wherein the positive electrode active material layer has a supporting quantity Lc1 per unit area in a range of 13.0≤Lc1≤25.0 mg/cm 2 .

5. The positive electrode according to claim 1 , wherein:
the positive electrode active material contains a compound expressed by the following formula (2) as a main component:
Li x Ni y M 1-y O z   (2)

where x, y, and z satisfy 0<x≤1.1, 0.5≤y≤1, and 1.9≤z≤2.1, and M includes at least one kind selected from Co, Mn, Al, Fe, and Mg; and
the surface of the positive electrode active material layer has a reflectance Rc2 in a range of 3.5≤Rc2≤7.8% at a wavelength of 550 nm.

6. The positive electrode according to claim 5 , wherein the positive electrode active material layer has a density dc2 in a range of 3.0≤dc2≤3.8 g/cm 3 .

7. The positive electrode according to claim 5 , wherein the positive electrode active material layer has a supporting quantity Lc2 per unit area in a range of 12.0≤Lc2≤24.0 mg/cm 2 .

8. The positive electrode according to claim 1 , wherein:
the positive electrode active material contains a compound expressed by the following formula (3) as a main component:
Li x M y O z PO 4   (3)

where x, y, and z satisfy 0<x≤1.1, 0<y≤1.1, and 0≤z≤1.0, and M includes at least one kind selected from Ni, Co, Mn, Al, Fe, Mg, Ag, and V; and
the surface of the positive electrode active material layer has a reflectance Rc3 in a range of 2.0≤Rc3≤5.8% at a wavelength of 550 nm.

9. The positive electrode according to claim 8 , wherein the positive electrode active material layer has a density dc3 in a range of 1.8≤dc3≤2.5 g/cm 3 .

10. The positive electrode according to claim 8 , wherein the positive electrode active material layer has a supporting quantity Lc3 per unit area in a range of 8.0≤Lc3≤15.0 mg/cm 2 .

11. A lithium ion secondary battery comprising:
the positive electrode according to claim 1 ;
a negative electrode including;
a negative electrode current collector; and
a negative electrode active material layer disposed on the negative electrode current collector and including a negative electrode active material, a surface of the negative electrode active material layer having a reflectance Ra in a range of 7.5≤Ra≤16.0% at a wavelength of 550 nm;

a separator; and
wherein the electrolyte solution is a nonaqueous electrolyte solution.

12. A lithium ion secondary battery comprising:
the positive electrode according to claim 2 ;
a negative electrode including:
a negative electrode current collector; and
a negative electrode active material layer disposed on the negative electrode current collector and including a negative electrode active material, a surface of the negative electrode active material layer having a reflectance Ra in a range of 7.5≤Ra≤16.0% at a wavelength of 550 nm;

a separator; and
wherein the electrolyte solution is a nonaqueous electrolyte solution.

13. The lithium ion secondary battery according to claim 12 , wherein a ratio of the reflectance Rc1 to the reflectance Ra, Rc1/Ra, is in a range of 1.00<Rc1/Ra≤1.53.

14. A lithium ion secondary battery comprising:
the positive electrode according to claim 5 ;
a negative electrode including:
a negative electrode current collector; and
a negative electrode active material layer disposed on the negative electrode current collector and including a negative electrode active material, a surface of the negative electrode active material layer having a reflectance Ra in a range of 7.5≤Ra≤16.0% at a wavelength of 550 nm;

a separator; and
wherein the electrolyte solution is a nonaqueous electrolyte solution.

15. The lithium ion secondary battery according to claim 14 , wherein a ratio of the reflectance Rc2 to the reflectance Ra, Rc2/Ra, is in a range of 0.29≤Rc2/Ra<1.00.

16. A lithium ion secondary battery comprising:
the positive electrode according to claim 8 ;
a negative electrode including:
a negative electrode current collector; and
a negative electrode active material layer disposed on the negative electrode current collector and including a negative electrode active material, a surface of the negative electrode active material layer having a reflectance Ra in a range of 7.5≤Ra≤16.0% at a wavelength of 550 nm;

a separator; and
wherein the electrolyte solution is a nonaqueous electrolyte solution.

17. The lithium ion secondary battery according to claim 16 , wherein a ratio of the reflectance Rc3 to the reflectance Ra, Rc3/Ra, is in a range of 0.13≤Rc3/Ra≤0.75.

18. The lithium ion secondary battery according to claim 11 , wherein the negative electrode active material contains a carbon material with a graphite structure.

19. The lithium ion secondary battery according to claim 11 , wherein:
the nonaqueous electrolyte solution includes a nonaqueous solvent and an electrolyte;
the nonaqueous solvent contains ethylene carbonate; and
the ethylene carbonate is contained in a range of 10 to 30 vol. % in the entire nonaqueous solvent.

Assignees

• Tdk Corp

Inventors

• Otsuki Keitaro
• Sato Tetsu
• Saegusa Masahiro

Classifications

• H01M4/587

  for inserting or intercalating light metals · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M2004/027

  Negative electrodes · CPC title

• H01M2004/021

  Physical characteristics, e.g. porosity, surface area · CPC title

• H01M4/505

  of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy · CPC title