Positive electrode active substance for secondary cell and method for producing same

Patent metadata

Field	Value
Publication number	US-11646405-B2
Application number	US-201515556936-A
Country	US
Kind code	B2
Filing date	Sep 17, 2015
Priority date	Mar 9, 2015
Publication date	May 9, 2023
Grant date	May 9, 2023

Abstract

A positive electrode active substance for a secondary cell, where the positive electrode active substance is capable of suppressing adsorption of water effectively in order to obtain a high-performance lithium ion secondary cell or sodium ion secondary cell. The positive electrode active substance contains 0.3 to 5 mass % of graphite, 0.1 to 4 mass % of carbon obtained by carbonizing a water-soluble carbon material, or 0.1 to 5 mass % of a metal fluoride is supported on a composite containing a compound which contains at least iron or manganese, where the compound is represented by formula (A) LiFe a Mn b M c PO 4 , formula (B) Li 2 Fe d Mn e N f SiO 4 , or formula (C) NaFe g Mn h Q i PO 4 , and carbon obtained by carbonizing a cellulose nanofiber.

First claim

The invention claimed is:

1. A positive electrode active substance, comprising:
a pyrolyzed composite of a compound of formula (A), (B), or (C);
carbon obtained by carbonizing a cellulose nanofiber; and
one material selected from the group consisting of 0.3 to 5 mass % of graphite, 0.1 to 4 mass % of carbon obtained by carbonizing a water-soluble carbon material, and 0.1 to 5 mass % of a metal fluoride:
LiFe a Mn b M 1 c PO 4   (A)

wherein M 1 represents Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd, and a, b, and c each represent a number satisfying 0.1≤a≤0.9, 0.1≤b≤0.9, 0<c≤0.1, 2a+2b+(valence of M 1 )×c=2;
Li 2 Fe d Mn e M 2 f SiO 4   (B)

wherein M 2 represents Al, Zn, V, or Zr, and d, e, and f each represent a number satisfying 0.1≤d≤0.6, 0.1≤e≤0.6, 0.05≤f≤0.4, 2d+2e+(valence of M 2 )×f=2; and
NaFe g Mn h Q i PO 4   (C)

wherein Q represents Mg, Ca, Co, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd, and g, h, and i each represent a number satisfying 0<g≤1, 0.5≤h<1, 0<i≤0.3, 2g+2h+(valence of Q)×i=2;
wherein
the compound of formula (A), (B) or (C) has an olivine-type structure, and
a surface of the compound of formula (A), (B), or (C) is completely covered by the carbon obtained by carbonizing a cellulose nanofiber and the graphite, carbonized product of the water-soluble carbon material or metal fluoride.

2. The positive electrode active substance according to claim 1 , wherein an amount of the carbon obtained by carbonizing a cellulose nanofiber is 0.5 to 15 mass % expressed in terms of carbon atoms.

3. The positive electrode active substance according to claim 1 , which comprises 0.3 to 5 mass % of graphite and is obtained by adding the graphite to the compound of formula (A), (B), or (C); and carbon obtained by carbonizing a cellulose nanofiber and conducting mixing treatment for 6 to 90 minutes while applying compressive force and shear force, wherein a mass ratio of an amount of the graphite added to an amount of the cellulose nanofiber expressed in terms of carbon atoms, (graphite/cellulose nanofiber), is 0.08 to 6.

4. The positive electrode active substance according to claim 1 , which comprises 0.1 to 4 mass % of carbon obtained by carbonizing a water-soluble carbon material and the water-soluble carbon material is supported on the composite as carbon obtained by subjecting the water-soluble carbon material and the compound of formula (A), (B), or (C); and carbon obtained by carbonizing a cellulose nanofiber to wet mixing and then carbonizing the resulting mixture.

5. The positive electrode active substance according to claim 4 , wherein the water-soluble carbon material is at least one selected from the group consisting of saccharides, polyols, polyethers, and organic acids.

6. The positive electrode active substance according to claim 1 , which comprises 0.1 to 5 mass % of a metal fluoride and the metal fluoride is supported on the composite by subjecting the compound of formula (A), (B), or (C); and carbon obtained by carbonizing a cellulose nanofiber and a precursor of the metal fluoride to wet mixing.

7. The positive electrode active substance according to claim 6 , wherein:
a metal of the metal fluoride is selected from the group consisting of lithium, sodium, magnesium, calcium, and aluminum; and
a precursor of the metal fluoride comprises: a fluorine compound selected from the group consisting of ammonium fluoride, hydrofluoric acid, and hypofluorous acid; and a metal compound selected from the group consisting of metal acetates, metal nitrates, metal lactates, metal oxalates, metal hydroxides, metal ethoxides, metal isopropoxides, and metal butoxides.

8. The positive electrode active substance according to claim 1 , wherein the composite comprising the compound and the carbon obtained by carbonizing a cellulose nanofiber is obtained by subjecting a slurry comprising:
a lithium compound or a sodium compound;
a compound comprising M 1 , M 2 or Q i ;
a phosphoric acid compound or a silicic acid compound;
an iron compound and a manganese compound; and
a cellulose nanofiber to hydrothermal reaction.

9. A method for producing a positive electrode active substance, the positive electrode active substance comprising 0.3 to 5 mass % of graphite supported on a composite comprising: a compound of formula (A), (B), or (C):
LiFe a Mn b M 1 c PO 4   (A)

wherein M 1 represents Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd, and a, b, c each represent a number satisfying 0.1≤a<0.9, 0.1≤b≤0.9, 0<c≤0.1, 2a+2b+(valence of M 1 )×c=2;
Li 2 Fe d Mn e M 2 f SiO 4   (B)

wherein M 2 represents Al, Zn, V, or Zr, and d, e, and f each represent a number satisfying 0.1≤d≤0.6, 0.1≤e≤0.6, 0.05≤f≤0.4, 2d+2e+(valence of M 2 )×f=2; and
NaFe g Mn h Q i PO 4   (C)

wherein Q represents Mg, Ca, Co, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd, and g, h, and i each represent a number satisfying 0<g≤1, 0.5≤h<1, 0<i≤0.3, 2g+2h+(valence of Q)×i=2;
wherein the compound of formula (A), (B) or (C) has an olivine-type structure; and

carbon obtained by carbonizing a cellulose nanofiber,
the method comprising:
(I-1) mixing a phosphoric acid compound or a silicic acid compound with a mixture (X-1) comprising: a lithium compound or a sodium compound; a compound comprising M 1 , M 2 or Q i and a cellulose nanofiber, thereby obtaining a composite (X-1);
(II-1) subjecting slurry (Y-1) comprising: the obtained composite (X-1); and a metal salt comprising an iron compound and a manganese compound to hydrothermal reaction, thereby obtaining a composite (Y-1);
(III-1) adding the graphite to the obtained composite (Y-1) to conduct mixing for 6 to 90 minutes while applying compressive force and shear force, thereby obtaining a composite (Z-1); and
(IV-1) pyrolyzing the obtained composite (Z-1) in a reducing atmosphere or an inert atmosphere.

10. A method for producing a positive electrode active substance, the positive electrode active substance comprising 0.1 to 4 mass % of carbon obtained by carbonizing a water-soluble carbon material, or 0.1 to 5 mass % of a metal fluoride supported on a composite comprising
a compound of formula (A), (B), or (C):
LiFe a Mn b M 1 c PO 4   (A)

wherein M 1 represents Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd, and a, b, c each represent a number satisfying 0.1≤a<0.9, 0.1≤b≤0.9, 0<c≤0.1, 2a+2b+(valence of M 1 )×c=2;
Li 2 Fe d Mn e M 2 f SiO 4   (B)

wherein M 2 represents Al, Zn, V, or Zr, and d, e, and f each represent a number satisfying 0.1≤d≤0.6, 0.1≤e≤0.6, 0.05≤f≤0.4, 2d+2e+(valence of M 2 )×2; and
NaFe g Mn h Q i PO 4   (C)

wherein Q represents Mg, Ca, Co, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd, and g, h, and i each represent a number satisfying 0<g≤1, 0.5≤h<1, 0<i≤0.3, 2g+2h+(valence of Q)×i=2;
wherein the compound of formula (A), (B) or (C) has an olivine-type structure; and

carbon obtained by carbonizing a cellulose nanofiber,
the method comprising:
(I-2) mixing a phosphoric acid compound or a silicic acid compound with a mixture (X-2) comprising: a lithium compound or a sodium compound; a compound comprising M 1 , M 2 or Q i and a cellulose nanofiber, thereby obtaining a composite (X-2);
(II-2) subjecting slurry (Y-2) comprising: the obtained composite (X-2); and a metal salt comprising an iron compound and a manganese compound to hydrothermal reaction, thereby obtaining a composite (Y-2); and
(III-2) adding 0.1 to 16 mass parts of a water-soluble organic compound to the obtained composite (Y-2) based on 100 mass parts of the composite (Y-2) or adding 0.1 to 40 mass parts of a precursor of the metal fluoride to the obtained composite (Y-2) based on 100 mass parts of the

Assignees

• Taiheiyo Cement Corp

Inventors

• Yamashita Hiroki
• Hatsumori Tomoki
• Nakamura Atsushi
• Ogami Takaaki

Classifications

• C01P2006/40

  Electric properties · CPC title

• C01P2004/80

  Particles consisting of a mixture of two or more inorganic phases · CPC title

• H01M10/054

  Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/625

  Carbon or graphite · CPC title