Positive electrode active substance for nonaqueous electrolyte secondary cell, method for producing same, and nonaqueous electrolyte secondary cell using positive electrode active substance

Patent metadata

Field	Value
Publication number	US-10084188-B2
Application number	US-201314411192-A
Country	US
Kind code	B2
Filing date	Jul 1, 2013
Priority date	Jul 12, 2012
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

A positive electrode active material is provided that has a high capacity, a low irreversible capacity, an excellent initial charge/discharge efficiency, and excellent rate characteristics. This positive electrode active material comprises a hexagonal lithium nickel complex oxide having a layer structure and represented by the general formula Li x Ni 1−y−z Co y M z O 2 (0.98≤x≤1.04, 0.25≤y≤0.40, 0≤z≤0.07, and M is at least one element selected from Al, Ti, Mn, Ga, Mg, and Nb), wherein a lithium occupancy rate in a lithium main layer as obtained by Rietveld analysis from the x-ray diffraction pattern is at least 98.7%, and a crystallite diameter as calculated from the peak for the (003) plane in x-ray diffraction is 50 to 300 nm.

First claim

The invention claimed is:

1. A positive electrode active material for a nonaqueous electrolyte secondary battery,
the material comprising a hexagonal lithium nickel complex oxide having a layer structure and represented by the general formula Li x Ni 1−y−z Co y M z O 2 (0.98≤x≤1.04, 0.30<y≤0.40, 0≤z≤0.07, and M is at least one element selected from Al, Ti, Mn, Ga, Mg, and Nb),
wherein a lithium occupancy rate in a lithium main layer as obtained by Rietveld analysis from the x-ray diffraction pattern is at least 98.7%,
a crystallite diameter as calculated from the peak for the (003) plane in x-ray diffraction is 50 to 300 nm, and
an initial charge/discharge efficiency is at least 94%, and
wherein the initial charge/discharge efficiency is defined as in a 2032-type coin battery in which the material is used as a positive electrode and lithium metal is used as a negative electrode, when evaluated by carrying out charging to a cutoff voltage of 4.3 V using a current density relative to the positive electrode of 0.5 mA/cm 2 to provide an initial charging capacity, carrying out discharge to a cutoff voltage of 3.0 V to provide an initial discharging capacity, and obtaining the initial charge/discharge efficiency by calculating the initial discharge capacity ×100/initial charging capacity.

2. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein the crystallite diameter is 120 to 200 nm.

3. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein a specific surface area is 0.3 to 1.0 m 2 /g.

4. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein
an average particle diameter of the primary particles constituting the positive electrode active material is 0.1 to 1 μm,
secondary particles are formed by the aggregation of a plurality of the primary particles, and
the secondary particles have a spherical or oval shape.

5. A method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 ,
the method comprising:
a coprecipitation step of obtaining at least a cobalt-containing nickel complex hydroxide by carrying out a coprecipitation by adding an alkali solution to a mixed aqueous solution containing at least a nickel salt and a cobalt salt and stirring the same;
a heat treatment step of obtaining a nickel complex oxide by heat treating the obtained nickel complex hydroxide at a temperature of 450 to 750° C.;
a mixing step of obtaining a lithium mixture by mixing the obtained nickel complex oxide with a lithium compound according to the amount corresponding to the general formula; and
a calcination step of calcining the obtained lithium mixture at a temperature of 720 to 830° C. in an oxygen atmosphere thereby obtaining a lithium nickel complex oxide.

6. The method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery, according to claim 5 , wherein the nickel complex oxide and the lithium compound are mixed in the mixing step so that an atomic ratio (Li/Me) for the lithium (Li) in the lithium compound to the total (Me) for metal elements in the nickel complex oxide is 0.98 to 1.04.

7. The method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery, according to claim 5 , wherein lithium hydroxide or a hydrate thereof is used as the lithium compound.

8. The method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery, according to claim 5 , wherein calcination is carried out in the calcination step at a temperature of 735 to 820° C.

9. The method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery, according to claim 5 , wherein a preliminary calcination is carried out prior to the calcination in the calcination step, the preliminary calcination being performed at a temperature that is in a range from 450 to 800° C. and is lower than the calcination temperature.

10. A nonaqueous electrolyte secondary battery, which is provided with a positive electrode that uses the positive electrode active material according to claim 1 .

11. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein M is Al.

12. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein M is Ti.

13. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein M is Mn.

14. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein M is Mg.

15. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein M is Nb.

16. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein z=0.

17. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein z satisfies 0≤z≤0.03.

Assignees

• Sumitomo Metal Mining Co

Inventors

• Mori Kensaku
• Takagi Masanori
• Yamaji Koji
• Honma Takehide
• Ushio Ryozo

Classifications

• C01P2006/11

  Powder tap density · CPC title

• H01M10/052

  Li-accumulators · CPC title

• C01P2006/12

  Surface area · CPC title

• H01M4/525 Primary

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title

• C01G53/006

  Chemistry & Metallurgy · mapped topic