Positive active material for lithium secondary battery, method for producing precursor of positive active material, method for producing positive active material, positive electrode for lithium secondary battery, and lithium secondary battery

Patent metadata

Field	Value
Publication number	US-2018366773-A1
Application number	US-201616061953-A
Country	US
Kind code	A1
Filing date	Dec 14, 2016
Priority date	Dec 15, 2015
Publication date	Dec 20, 2018
Grant date	—

Abstract

The positive active material for a lithium secondary battery includes a lithium transition metal composite oxide having an α-NaFeO 2 structure, and having a diffraction peak at 2 θ=44±1° and a diffraction peak at 2 θ=18.6±1° in a powder X-ray diffraction diagram using a CuKα ray. In a ratio FWHM (003)/FWHM (104) of a full width at half maximum FWHM (003) for the diffraction peak at 2 θ=18.6±1° to a full width at half maximum FWHM (104) for the diffraction peak at 20 θ=44±1°, a ratio of FWHM (003)/FWHM (104) in a charge state immediately after a discharge state to FWHM (003)/FWHM (104) in the discharge state is 0.72 or more.

First claim

1 . A positive active material for a lithium secondary battery which comprises a lithium transition metal composite oxide,
wherein the lithium transition metal composite oxide has an α-NaFeO 2 structure, and has a diffraction peak at 2 θ=44±1° and a diffraction peak at 2 θ=18.6±1° in a powder X-ray diffraction diagram using a CuKα ray, and in a ratio FWHM (003)/FWHM (104) of a full width at half maximum FWHM (003) for the diffraction peak at 18.6±1° to a full width at half maximum FWHM (104) for the diffraction peak at 44±1°, a ratio of FWHM (003)/FWHM (104) in a charge state immediately after a discharge state to FWHM (003)/FWHM (104) in the discharge state is 0.72 or more.

2 . A positive active material for a lithium secondary battery which comprises a lithium transition metal composite oxide,
wherein the lithium transition metal composite oxide has an α-NaFeO 2 structure, a full width at half maximum for a diffraction peak at 2 θ=44±1° in a powder X-ray diffraction diagram using a CuKα ray is 0.125 to 0.145°, and the lithium transition metal composite oxide has a porosity is 1.5 to 3.5%.

3 . A positive active material for a lithium secondary battery which comprises a lithium transition metal composite oxide,
wherein the lithium transition metal composite oxide has an α-NaFeO 2 structure, and in a crystallite size determined from a powder X-ray diffraction diagram using a CuKα ray, a reduction amount of the crystalline size in a charge state immediately after a discharge state with respect to the crystalline size in the discharge state is 20 nm or less.

4 . The positive active material for a lithium secondary battery according to claim 1 , wherein the lithium transition metal composite oxide contains Ni and Mn or Ni, Co and Mn as a transition metal element (Me).

5 . The positive active material for a lithium secondary battery according to claim 4 , wherein the lithium transition metal composite oxide is represented by the composition formula: Li 1+x Me 1−x O 2 (Me is a transition metal element containing Ni and Mn, or Ni, Co and Mn), and a molar ratio Li/Me of Li to Me, i.e. (1+x)/(1−x) is 1.0 or more and 1.1 or less.

6 . The positive active material for a lithium secondary battery according to claim 1 , wherein the lithium transition metal composite oxide contains at least one selected from the group consisting of F, S and P on surfaces of particles of the lithium transition metal composite oxide.

7 . A method for producing a precursor to be used in production of a positive active material for a lithium secondary battery which includes a lithium transition metal composite oxide,
the method comprising precipitating a transition metal compound in a fluorine ion-containing solution to produce a precursor of a lithium transition metal composite oxide having an α-NaFeO 2 structure.

8 . The method for producing a precursor according to claim 7 , wherein the fluorine ion-containing solution contains ammonium ions.

9 . The method for producing a precursor according to claim 7 , wherein the lithium transition metal composite oxide is an oxide containing Ni and Mn or Ni, Co and Mn as a transition metal element, and the transition metal compound contains Ni and Mn or Ni, Co and Mn as transition metals.

10 . A method for producing a positive active material for a lithium secondary battery which includes a lithium transition metal composite oxide, the method comprising adding a lithium compound and a sintering aid in a precursor produced by the method for producing a precursor according to claim 7 , and firing the mixture to produce a lithium transition metal composite oxide having an α-NaFeO 2 structure.

11 . The method for producing a positive active material for a lithium secondary battery according to claim 10 , wherein the sintering aid is lithium fluoride, lithium sulfate or lithium phosphate.

12 . The method for producing a positive active material for a lithium secondary battery according to claim 10 , wherein a temperature for firing the precursor is 900 to 1000° C.

13 . A positive electrode for a lithium secondary battery which comprises the positive active material for a lithium secondary battery according to claim 1 .

14 . A lithium secondary battery comprising a positive electrode, a negative electrode and a nonaqueous electrolyte, the positive electrode including the positive electrode according to claim 13 .

15 . The lithium secondary battery according to claim 14 , wherein the nonaqueous electrolyte contains propylene carbonate.

Assignees

• Gs Yuasa Int Ltd

Inventors

• Endo Daisuke
• Shimizu Takashi

Classifications

• H01M10/0525 Primary

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

• H01M10/0431

  Cells with wound or folded electrodes (H01M10/045 takes precedence) · CPC title

• H01M10/056

  characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes · CPC title

• H01M4/52

  of nickel, cobalt or iron · CPC title

• H01M4/382

  Lithium (H01M4/405 takes precedence) · CPC title