JP2019033016A - Positive electrode active material for lithium ion secondary battery or positive electrode active material for sodium ion secondary battery, and production method thereof - Google Patents

Abstract

Disclosed is a lithium ion secondary battery or a sodium ion secondary battery, which can prepare a slurry having stable workability without causing a change in viscosity over time in a positive electrode manufacturing process. And a positive electrode active material for a lithium ion secondary battery or a positive electrode active material for a sodium ion secondary battery comprising a layered composite oxide that can ensure both safety and safety. A layered lithium composite oxide secondary particle comprising lithium composite oxide particles represented by the following formula (I) or the following formula (II): LiNiaCobMncM1xO2 (I) LiNidCoeAlfM2yO2 (II) In only a part of the surface of (A), the specific lithium-based polyanion particles (B) and the layered lithium composite oxide particles are combined, and the peak intensity ratio ((XPS) by X-ray photoelectron spectroscopy (XPS) (( A cathode active material for a lithium ion secondary battery having a peak intensity of Ni2p3 / 2 / (peak intensity of P2p + peak intensity of C1s) exceeding 0.05 and less than 0.4. [Selection figure] None

Description

  The present invention provides a positive electrode active material for a lithium ion secondary battery having a layered rock salt structure, which has excellent workability in the manufacturing process of the positive electrode and has both excellent discharge characteristics and safety when used as a secondary battery. The present invention relates to a material or a positive electrode active material for a sodium ion secondary battery, and a method for producing them.

  Layered lithium composite oxides such as layered lithium / nickel / cobalt / manganese composite oxide (NCM) and layered lithium / nickel / cobalt / aluminum composite oxide (NCA) include a lithium atomic layer and a transition metal atomic layer. However, it has a layered crystal structure in which oxygen atoms are alternately stacked and has a so-called layered rock salt structure in which one lithium atom is contained per one atom of the transition metal. Such a layered lithium composite oxide is used as a positive electrode active material capable of constituting a high-output and high-capacity lithium ion secondary battery.

  In a lithium ion secondary battery using such a layered lithium composite oxide as a positive electrode active material, charging and discharging are performed by lithium ions being desorbed and inserted into the layered lithium composite oxide. As the discharge cycle is repeated, the capacity decreases, and particularly when used for a long time, the capacity of the battery may be significantly decreased. This is considered to be caused by the fact that the transition metal component of the layered lithium composite oxide elutes into the electrolytic solution during charging, so that the crystal structure is likely to collapse. Further, the elution of the transition metal component into the electrolytic solution may reduce the thermal stability of the lithium ion secondary battery and impair the safety.

Therefore, when using a layered lithium composite oxide as a positive electrode active material, by mixing another lithium positive electrode active material excellent in safety with the layered lithium composite oxide and diluting the layered lithium composite oxide, Technology to ensure safety has been developed. For example, Patent Document 1 contains layered type lithium / nickel / manganese / cobalt composite oxide in an amount of 65% by mass or more of the total amount of the positive electrode mixture, and Li _{1 + x} MPO ₄ (0 ≦ x ≦ 1, M is Li, Fe , Ni, Co, Mn, Ti, Cu, Zn, Mg, and Zr), a positive electrode containing 10% by mass or more of a lithium composite oxide having an olivine structure represented by A technology for improving the safety of a lithium ion secondary battery is disclosed.

  On the other hand, since lithium is a rare valuable substance, it has a layered rock salt structure similar to the layered lithium composite oxide, and can be charged and discharged with sodium ions instead of lithium ions, useful as a positive electrode active material, A so-called layered sodium complex oxide has also been developed. For example, Patent Document 2 discloses a positive electrode active material made of a composite metal oxide containing sodium and two or more metal elements selected from the group consisting of Fe, Mn, Ni, Co, and Ti.

Japanese Patent Laid-Open No. 2006-76317 JP 2010-80424 A

  By the way, in order to produce a positive electrode of a lithium ion secondary battery or a sodium ion secondary battery using a positive electrode active material made of such a layered composite oxide, the positive electrode active material, a conductive aid such as carbon black, Add a solvent such as N-methyl-2-pyrrolidone to a binder (binder) such as polyvinylidene fluoride, and knead it thoroughly to prepare a positive electrode slurry, which is uniformly applied to a current collector such as an aluminum foil. After coating to a proper thickness, it is compacted by a roller press or the like and dried.

  The positive electrode slurry obtained by preparing as described above is required to have a flow characteristic such as viscosity that is less likely to change over time. A positive electrode slurry is prepared using the lithium composite oxide described in Patent Document 1. Then, the viscosity increases with the lapse of time after kneading, and there is a possibility that the coating thickness may be uneven on the current collector to the extent that it cannot be eliminated even by compacting. Therefore, there is a concern that the thickness of the positive electrode material on the current collector becomes a non-uniform positive electrode, and the discharge capacity of the obtained lithium ion secondary battery is reduced.

  Therefore, an object of the present invention is to prepare a slurry having stable workability (hereinafter referred to as “positive electrode slurry”) without causing a change in viscosity over time in the positive electrode manufacturing process, and to obtain lithium ions In a secondary battery or a sodium ion secondary battery, a positive electrode active material for a lithium ion secondary battery or a positive electrode for a sodium ion secondary battery comprising a layered composite oxide that can ensure both excellent discharge capacity and safety It is to provide an active material.

  Therefore, as a result of intensive studies, the present inventors have found that the specific polyanion particles and the composite oxide particles are composited only on a part of the surface of the layered composite oxide secondary particles composed of the specific composite oxide particles. By using a positive electrode active material having a specific peak intensity by XPS, it is possible to prepare a positive electrode slurry that is less likely to change in viscosity over time, and has a lithium ion secondary battery having excellent discharge characteristics and safety. It discovered that a secondary battery or a sodium ion secondary battery was obtained.

That is, the present invention provides the following formula (I):
LiNi _a Co _b Mn _c M ¹ _x O ₂ (I)
(In the formula (I), ^{M 1} is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, 1 or 2 or more elements selected from Bi and Ge are shown, a, b, c, and x are 0.3 ≦ a <1, 0 <b ≦ 0.7, 0 <c ≦ 0.7, (0 ≦ x ≦ 0.3 and 3a + 3b + 3c + (valence of M ¹ ) × x = 3)
Or the following formula (II):
LiNi _d Co _e Al _f M ² _y O ₂ (II)
(In the formula (II), ^{M 2} is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and One or more elements selected from Ge are shown, d, e, f, and y are 0.4 ≦ d <1, 0 <e ≦ 0.6, 0 <f ≦ 0.3, 0 ≦. (Y ≦ 0.3 and 3d + 3e + 3f + (valence of M ² ) × y = 3)
In only a part of the surface of the layered lithium composite oxide secondary particles (A) composed of lithium composite oxide particles represented by the following formula (V):
LiCo _g M ⁵ _i PO ₄ (V)
(In the formula (V), M ⁵ represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. G and i are 0 <g ≦ 1 , 0 ≦ i ≦ 0.3, and 2g + (the valence of M ⁵ ) × i = 2.)
Or the following formula (VI):
LiFe _m Mn _n M ⁶ _o PO ₄ (VI)
(In the formula (VI), M ⁶ represents Co, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. M, n, and o are 0 ≦ m ≦ 1 represents a number satisfying 0 ≦ n ≦ 1, 0 ≦ o ≦ 0.3, and m + n ≠ 0, and satisfying 2m + 2n + (valence of M ⁶ ) × o = 2.)
Lithium-based polyanion particles (B) formed by supporting carbon (c) on the surface and lithium composite oxide particles are combined,
Lithium ion secondary whose peak intensity ratio ((Ni2p _3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) by X-ray photoelectron spectroscopy (XPS) is more than 0.05 and less than 0.4 A positive electrode active material for a battery is provided.

The present invention also provides the following formula (III):
NaNi _{a ′} Co _{b ′} Mn _{c ′} M ³ _{x ′} O ₂ (III)
(In the formula (III), ^{M 3} is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, 1 or 2 or more elements selected from Bi and Ge, a ′, b ′, c ′ and x ′ are 0.3 ≦ a ′ <1, 0 <b ′ ≦ 0.7, 0 < (c ′ ≦ 0.7, 0 ≦ x ′ ≦ 0.3, and 3a ′ + 3b ′ + 3c ′ + (valence of M ³ ) × x ′ = 3).
Or the following formula (IV):
NaNi _{d ′} Co _{e ′} Al _{f ′} M ⁴ _{y ′} O ₂ (IV)
(In the formula (IV), M ⁴ is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and 1 or 2 or more elements selected from Ge, d ′, e ′, f ′, and y ′ are 0.4 ≦ d ′ <1, 0 <e ′ ≦ 0.6, and 0 <f ′. ≦ 0.3,0 ≦ y '≦ 0.3, and 3d' + 3e '+ 3f' + ( valence of ^{M 4)} shows a number satisfying × y '= 3.)
In only a part of the surface of the layered sodium composite oxide secondary particles (D) composed of the sodium composite oxide particles represented by the following formula (VII):
NaCo _{g ′} M ⁷ _{i ′} PO ₄ (VII)
(In the formula (VII), M ⁷ represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. G ′ and i ′ are 0 <g '≦ 1, 0 ≦ i' ≦ 0.3, and 2g ′ + (valence of M ⁷ ) × i ′ = 2).
Or the following formula (VIII):
NaFe _{m ′} Mn _{n ′} M ⁸ _{o ′} PO ₄ (VIII)
(In the formula (VIII), M ⁸ represents Co, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. M ′, n ′, and o ′ are 0. ≦ m ′ ≦ 1, 0 ≦ n ′ ≦ 1, 0 ≦ o ′ ≦ 0.3, and m ′ + n ′ ≠ 0, and 2m ′ + 2n ′ + (valence of M ⁸ ) × o ′ = 2 Indicates the number satisfying.)
The sodium-based polyanion particles (E) formed by supporting carbon (c) on the surface and sodium composite oxide particles are combined,
Sodium ion secondary whose peak intensity ratio ((Ni2p _3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) by X-ray photoelectron spectroscopy (XPS) is more than 0.05 and less than 0.4 A positive electrode active material for a battery is provided.

  Furthermore, the present invention mixes layered lithium composite oxide secondary particles (A) and lithium-based polyanion particles (B) having carbon (c) supported on the surface while applying compressive force and shearing force. The manufacturing method of the said positive electrode active material body for lithium ion secondary batteries provided with the process to combine is provided.

  In the present invention, layered sodium composite oxide secondary particles (D) and sodium-based polyanion particles (E) having carbon (c) supported on the surface are mixed while applying compressive force and shearing force. The manufacturing method of the said positive electrode active material body for lithium ion secondary batteries provided with the process to combine is provided.

  According to the positive electrode active material for a lithium ion secondary battery or the positive electrode active material for a sodium ion secondary battery of the present invention, while using a layered composite oxide, the increase in viscosity over time is suppressed, and stable workability is achieved. The provided positive electrode slurry can be prepared, and in the obtained lithium ion secondary battery or sodium ion secondary battery, both excellent discharge characteristics and safety can be achieved.

Hereinafter, the present invention will be described in detail.
The positive electrode active material for a lithium ion secondary battery of the present invention has the following formula (I):
LiNi _a Co _b Mn _c M ¹ _x O ₂ (I)
(In the formula (I), ^{M 1} is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, 1 or 2 or more elements selected from Bi and Ge are shown, a, b, c, and x are 0.3 ≦ a <1, 0 <b ≦ 0.7, 0 <c ≦ 0.7, (0 ≦ x ≦ 0.3 and 3a + 3b + 3c + (valence of M ¹ ) × x = 3)
Or the following formula (II):
LiNi _d Co _e Al _f M ² _y O ₂ (II)
(In the formula (II), ^{M 2} is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and One or more elements selected from Ge are shown, d, e, f, and y are 0.4 ≦ d <1, 0 <e ≦ 0.6, 0 <f ≦ 0.3, 0 ≦. (Y ≦ 0.3 and 3d + 3e + 3f + (valence of M ² ) × y = 3)
In only a part of the surface of the layered lithium composite oxide secondary particles (A) composed of lithium composite oxide particles represented by the following formula (V):
LiCo _g M ⁵ _i PO ₄ (V)
(In the formula (V), M ⁵ represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. G and i are 0 <g ≦ 1 , 0 ≦ i ≦ 0.3, and 2g + (the valence of M ⁵ ) × i = 2.)
Or the following formula (VI):
LiFe _m Mn _n M ⁶ _o PO ₄ (VI)
(In the formula (VI), M ⁶ represents Co, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. M, n, and o are 0 ≦ m ≦ 1 represents a number satisfying 0 ≦ n ≦ 1, 0 ≦ o ≦ 0.3, and m + n ≠ 0, and satisfying 2m + 2n + (valence of M ⁶ ) × o = 2.)
Lithium-based polyanion particles (B) formed by supporting carbon (c) on the surface and lithium composite oxide particles are combined,
The peak intensity ratio ((Ni2p _3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) by X-ray photoelectron spectroscopy (XPS) is more than 0.05 and less than 0.4.

Moreover, the positive electrode active material for sodium ion secondary batteries of the present invention has the following formula (III):
NaNi _{a ′} Co _{b ′} Mn _{c ′} M ³ _{x ′} O ₂ (III)
(In the formula (III), ^{M 3} is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, 1 or 2 or more elements selected from Bi and Ge, a ′, b ′, c ′ and x ′ are 0.3 ≦ a ′ <1, 0 <b ′ ≦ 0.7, 0 < (c ′ ≦ 0.7, 0 ≦ x ′ ≦ 0.3, and 3a ′ + 3b ′ + 3c ′ + (valence of M ³ ) × x ′ = 3).
Or the following formula (IV):
NaNi _{d ′} Co _{e ′} Al _{f ′} M ⁴ _{y ′} O ₂ (IV)
(In the formula (IV), M ⁴ is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and 1 or 2 or more elements selected from Ge, d ′, e ′, f ′, and y ′ are 0.4 ≦ d ′ <1, 0 <e ′ ≦ 0.6, and 0 <f ′. ≦ 0.3,0 ≦ y '≦ 0.3, and 3d' + 3e '+ 3f' + ( valence of ^{M 4)} shows a number satisfying × y '= 3.)
In only a part of the surface of the layered sodium composite oxide secondary particles (D) composed of the sodium composite oxide particles represented by the following formula (VII):
NaCo _{g ′} M ⁷ _{i ′} PO ₄ (VII)
(In the formula (VII), M ⁷ represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. G ′ and i ′ are 0 <g '≦ 1, 0 ≦ i' ≦ 0.3, and 2g ′ + (valence of M ⁷ ) × i ′ = 2).
Or the following formula (VIII):
NaFe _{m ′} Mn _{n ′} M ⁸ _{o ′} PO ₄ (VIII)
(In the formula (VIII), M ⁸ represents Co, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. M ′, n ′, and o ′ are 0. ≦ m ′ ≦ 1, 0 ≦ n ′ ≦ 1, 0 ≦ o ′ ≦ 0.3, and m ′ + n ′ ≠ 0, and 2m ′ + 2n ′ + (valence of M ⁸ ) × o ′ = 2 Indicates the number satisfying.)
The sodium-based polyanion particles (E) formed by supporting carbon (c) on the surface and sodium composite oxide particles are combined,
The peak intensity ratio ((Ni2p _3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) by X-ray photoelectron spectroscopy (XPS) is more than 0.05 and less than 0.4.

Layered lithium composite oxide composed of lithium composite oxide particles represented by the above formula (I) (so-called Li—Ni—Co—Mn oxide, hereinafter referred to as “Li—NCM composite oxide”) Layered-type sodium composite oxide (so-called Na-Ni-Co-Mn oxide, consisting of secondary particles (A) and sodium composite oxide particles represented by the above formula (III). In addition, Li-NCM composite oxide and Na-NCM composite oxide are collectively referred to as “NCM composite oxide.) Secondary particles (D) and the above formula (II) Layered lithium composite oxide (so-called Li-Ni-Co-Al oxide, hereinafter referred to as "Li-NCA composite oxide") secondary particles (A ), And the above formula (IV A layered sodium composite oxide (so-called Na—Ni—Co—Al oxide, hereinafter referred to as “Na—NCA composite oxide”). The composite oxide and the Na-NCA composite oxide are collectively referred to as “NCA composite oxide.”) The secondary particles (D) are all particles having a layered rock salt structure.

M ¹ in the above formula (I) or M ³ in the above formula (III) is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, respectively. One or more elements selected from Sn, Ta, W, La, Ce, Pb, Bi and Ge are shown.
In the above formula (I), a, b, c and x are 0.3 ≦ a <1, 0 <b ≦ 0.7, 0 <c ≦ 0.7, 0 ≦ x ≦ 0.3, And 3a + 3b + 3c + (valence of M ¹ ) × x = 3, and a ′, b ′, c ′, x ′ in the above formula (III) are 0.3 ≦ a ′ <1, 0 < b ′ ≦ 0.7, 0 <c ′ ≦ 0.7, 0 ≦ x ′ ≦ 0.3, and 3a ′ + 3b ′ + 3c ′ + (valence of M ³ ) × x ′ = 3 .

In the NCM-based composite oxide represented by the above formula (I) or formula (III), Ni, Co and Mn are known to have excellent electron conductivity and contribute to battery capacity and output characteristics. Further, from the viewpoint of cycle characteristics, it is preferable that a part of the transition element is substituted with another metal element M ¹ or M ³ . By substituting with these metal elements M ¹ or M ³ , the crystal structure of the NCM composite oxide represented by the formula (I) or the formula (III) is stabilized. It is considered that even if the discharge is repeated, the collapse of the crystal structure can be suppressed and a high discharge capacity can be secured.
Specific examples of the Li-NCM composite oxide represented by the above formula (I) include, for example, LiNi _0.33 Co _0.33 Mn _0.34 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O. ₂ , LiNi _0.2 Co _0.4 Mn _0.4 O ₂ , LiNi _0.33 Co _0.31 Mn _0.33 Mg _0.03 O ₂ , LiNi _0.33 Co _0.31 Mn _0.33 Zn _0.03 O _{2 and the} like. Among these, when the discharge capacity is more important, a composition with a large amount of Ni such as LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiNi _0.6 Co _0.2 Mn _0.2 O ₂ is preferable, and when the cycle characteristics are more important, A composition having a small amount of Ni, such as LiNi _0.33 Co _0.33 Mn _0.34 O ₂ and LiNi _0.33 Co _0.31 Mn _0.33 Mg _0.03 O _2, is preferable.
Specific examples of the Na-NCM composite oxide represented by the above formula (III) include NaNi _0.33 Co _0.33 Mn _0.34 O ₂ , NaNi _0.8 Co _0.1 Mn _0.1 O ₂ , NaNi _0.6 Co _0.2 Mn. Examples thereof include _0.2 O ₂ , NaNi _0.2 Co _0.4 Mn _0.4 O ₂ , NaNi _0.33 Co _0.31 Mn _0.33 Mg _0.03 O ₂ , and NaNi _0.33 Co _0.31 Mn _0.33 Zn _0.03 O ₂ . Among these, in the case where the discharge capacity is more important, a composition having a large amount of Ni such as NaNi _0.8 Co _0.1 Mn _0.1 O ₂ and NaNi _0.6 Co _0.2 Mn _0.2 O ₂ is preferable, and in the case where the cycle characteristics are more important, A composition with a small amount of Ni, such as NaNi _0.33 Co _0.33 Mn _0.34 O ₂ and NaNi _0.33 Co _0.31 Mn _0.33 Mg _0.03 O _2, is preferred.

The average particle size of the primary particles of the NCM composite oxide represented by the above formula (I) or formula (III) is preferably 500 nm or less, more preferably 300 nm or less. Thus, by setting the average particle size of the primary particles of the NCM composite oxide to at least 500 nm or less, it is possible to suppress the amount of expansion and contraction of the primary particles accompanying the insertion and desorption of lithium ions or sodium ions. , Particle breakage can be effectively prevented. The lower limit of the average particle size of the primary particles is not particularly limited, but is preferably 50 nm or more from the viewpoint of handling.
The average particle diameter of the NCM composite oxide secondary particles (A) or (D) formed by aggregation of the primary particles is preferably 25 μm or less, more preferably 20 μm or less. When the average particle size of the secondary particles is 25 μm or less, a positive electrode slurry with good uniformity of the coating thickness on the current collector can be easily prepared. The lower limit of the average particle size of the secondary particles is not particularly limited, but is preferably 1 μm or more and more preferably 5 μm or more from the viewpoint of handling.
Here, the average particle diameter means an average value of measured values of the particle diameter (length of major axis) of several tens of particles in observation with an SEM or TEM electron microscope.

  In the present specification, the NCM-based composite oxide secondary particles (A) or (D) include only the primary particles formed from the respective secondary particles, and are lithium-based polyanion particles (B) or sodium-based particles. Does not contain polyanion particles (E).

  Actually, the NCM composite oxide secondary particles (A) or (D) have voids formed between the primary particles, but the NCM composite oxide secondary particles (A) or (D) Since the interparticle voids are reduced in the production of NCM composite oxide secondary particles (A) or (D), the lithium polyanion particles (B) or sodium polyanion particles (E) It is not large enough to penetrate inside.

Next, the Li—NCA composite oxide represented by the formula (II) and the Na—NCA composite oxide represented by the formula (IV) will be described.
M ² in the above formula (II) or M ⁴ in the above formula (IV) is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, respectively. 1 element or 2 or more elements selected from Ta, W, La, Ce, Pb, Bi and Ge.
In the above formula (II), d, e, f, and y are 0.4 ≦ d <1, 0 <e ≦ 0.6, 0 <f ≦ 0.3, 0 ≦ y ≦ 0.3, And 3d + 3e + 3f + (valence of M ² ) × y = 3, and d ′, e ′, f ′, and y ′ in the above formula (IV) are 0.4 ≦ d ′ <1, 0 < e ′ ≦ 0.6, 0 <f ′ ≦ 0.3, 0 ≦ y ′ ≦ 0.3, and 3d ′ + 3e ′ + 3f ′ + (valence of M ⁴ ) × y ′ = 3 .

The NCA-based composite oxide represented by the formula (II) or the formula (IV) is more discharged than the NCM-based composite oxide represented by the formula (I) or the formula (III). Excellent capacity and output characteristics. In addition, due to the inclusion of Al, alteration due to moisture in the atmosphere hardly occurs, and the safety is excellent.
Specific examples of the Li-NCA composite oxide represented by the above formula (II) include LiNi _0.33 Co _0.33 Al _0.34 O ₂ , LiNi _0.8 Co _0.1 Al _0.1 O ₂ , LiNi _0.8 Co _0.15 Al _0.03 Mg _Examples include _0.03 O ₂ and LiNi _0.8 Co _0.15 Al _0.03 Zn _0.03 O ₂ . Of these, LiNi _0.8 Co _0.15 Al _0.03 Mg _0.03 O ₂ is preferable.
Further, specific examples of the Na-NCA based complex oxide represented by the above formula (IV) include, for example, NaNi _0.33 Co _0.33 Al _0.34 O ₂ , NaNi _0.8 Co _0.1 Al _0.1 O ₂ , NaNi _0.8 Co _0.15 Al _0.03 Mg _0.03 O ₂ , NaNi _0.8 Co _0.15 Al _0.03 Zn _0.03 O _{2 and the} like. Of these, NaiNi _0.8 Co _0.15 Al _0.03 Mg _0.03 O ₂ is preferable.

  The average particle diameter of the primary particles of the NCA-based composite oxide represented by the above formula (II) or formula (IV), and the NCA-based composite oxide secondary particles (A) formed by aggregation of the primary particles or The average particle diameter of (D) is the same as that of said NCM type complex oxide. That is, the average particle diameter of the primary particles of the NCA-based composite oxide represented by the above formula (II) or formula (IV) is preferably 500 nm or less, more preferably 300 nm or less, and the primary particles. The average particle diameter of the NCA-based composite oxide secondary particles (A) or (D) is preferably 25 μm or less, more preferably 20 μm or less.

  The layered lithium composite oxide secondary particles (A) in the present invention include a Li-NCM composite oxide represented by the above formula (I) and a Li-NCA composite oxide represented by the above formula (II). May be mixed. The mixed state is such that the primary particles of the Li—NCM composite oxide represented by the above formula (I) and the primary particles of the Li—NCA composite oxide represented by the above formula (II) coexist. Secondary particles may be formed, and only secondary particles composed only of the Li-NCM composite oxide represented by the above formula (I) and Li-NCA composite oxide represented by the above formula (II) Secondary particles composed of the above may be mixed, and further, primary particles of the Li-NCM composite oxide represented by the above formula (I) and Li-NCA composite oxide represented by the above formula (II) Secondary particles formed by the coexistence of primary particles of the product, secondary particles composed only of the Li-NCM composite oxide represented by the above formula (I), and the Li-NCA composite represented by the above formula (II) Secondary particles composed only of oxides may be mixed.

  In addition, the layered sodium composite oxide secondary particles (D) of the present invention include a Na—NCM composite oxide represented by the above formula (III) and a Na—NCA composite represented by the above formula (IV). An oxide may be mixed. The mixed state is such that the primary particles of the Na—NCM composite oxide represented by the above formula (III) and the primary particles of the Na—NCA composite oxide represented by the above formula (IV) coexist. Secondary particles may be formed, and only secondary particles composed only of the Na—NCM complex oxide represented by the above formula (III) and only the Na—NCA complex oxide represented by the above formula (IV). Secondary particles composed of the above may be mixed, and further, the primary particles of the Na-NCM composite oxide represented by the above formula (III) and the Na-NCA composite oxide represented by the above formula (IV) Secondary particles formed by the coexistence of primary particles of the product, secondary particles composed only of the Na-NCM composite oxide represented by the formula (III), and the Na-NCA composite represented by the formula (IV) Secondary particles composed only of oxides may be mixed.

  NCM composite in the case where the NCM composite oxide represented by the above formula (I) or the above formula (III) and the NCA composite oxide represented by the above formula (II) or the above formula (IV) coexist. What is necessary is just to adjust suitably the ratio (mass%) of an oxide and a NCA type complex oxide by the battery characteristic to request | require. For example, when the rate characteristic is more important, it is preferable to increase the proportion of the NCM composite oxide represented by the above formula (I) or the above formula (III). It is preferable that it is the mass ratio (NCM type complex oxide: NCA type complex oxide) = 99.9: 0.1-60: 40 of a product and an NCA type complex oxide. For example, when the discharge capacity is more important, it is preferable to increase the proportion of the NCA-based composite oxide represented by the above formula (II) or the above formula (IV). It is preferable that it is the mass ratio (NCM type complex oxide: NCA type complex oxide) = 40: 60-0.1: 99.9 of a system complex oxide and a NCA system complex oxide.

Next, the lithium polyanion particles (B) and the sodium polyanion particles (E) will be described.
The lithium-based polyanion particles (B), which are combined with the lithium composite oxide particles only on a part of the surface of the layered lithium composite oxide secondary particles (A), have the following formula (V):
LiCo _g M ⁵ _i PO ₄ (V)
(In the formula (V), M ⁵ represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. G and i are 0 <g ≦ 1 , 0 ≦ i ≦ 0.3, and 2g + (the valence of M ⁵ ) × i = 2.)
Or the following formula (VI):
LiFe _m Mn _n M ⁶ _o PO ₄ (VI)
(In the formula (VI), M ⁶ represents Co, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. M, n, and o are 0 ≦ m ≦ 1 represents a number satisfying 0 ≦ n ≦ 1, 0 ≦ o ≦ 0.3, and m + n ≠ 0, and satisfying 2m + 2n + (valence of M ⁶ ) × o = 2.)
And is a compound that can provide good lithium ion conductivity. Furthermore, the lithium-based polyanion particles (B) represented by the above formula (V) or formula (VI) have carbon (c) supported on the particle surface, and the carbon (c) is derived from cellulose nanofibers. Carbon (c1) or carbon (c2) derived from a water-soluble carbon material may be used.

Specific examples of the lithium-based polyanion particles (B) represented by the above formula (V) include LiCoPO ₄ and LiCo _0.25 Fe _0.25 PO ₄ .
In addition, the lithium-based polyanion particle (B) represented by the above formula (VI) is preferably 0.5 ≦ n ≦ 1 from the viewpoint of the average discharge voltage of the positive electrode active material for a lithium ion secondary battery. 6 ≦ n ≦ 1 is more preferable, and 0.65 ≦ n ≦ 1 is more preferable. Specifically, for example, LiMnPO ₄ , LiMn _0.9 Fe _0.1 PO ₄ , LiMn _0.8 Fe _0.2 PO ₄ , LiMn _0.75 Fe _0.15 Mg _0.1 PO ₄ , LiMn _0.75 Fe _0.19 Zr _0.03 PO ₄ , LiMn _0.7 Fe _0.3 PO ₄ , LiMn _0.6 Fe _0.4 PO ₄ , LiMn _0.5 Fe _0.5 PO _{4 and the} like can be mentioned, among which LiMn _0.8 Fe _0.2 PO ₄ is preferable.

  The average particle size of the lithium-based polyanion particles (B) represented by the above formula (V) or formula (VI) is close to that of the lithium composite oxide particles on the surface of the layered lithium composite oxide secondary particles (A). From the viewpoint of compounding, the thickness is preferably 20 to 200 nm. Specifically, when the lithium-based polyanion particle (B) is represented by the formula (V), it is more preferably 20 to 200 nm, further preferably 25 to 180 nm, and further preferably 30 to 170 nm. It is. Moreover, when lithium type polyanion particle | grains (B) are represented by Formula (VI), More preferably, it is 50-200 nm, More preferably, it is 70-150 nm.

The lithium ion conductivity of the lithium-based polyanion particle (B) represented by the above formula (V) or formula (VI) at 20 MPa pressurization at 25 ° C. is 1 × 10 ⁻⁷ S / cm or more. Preferably, it is 1 × 10 ⁻⁶ S / cm or more. The upper limit value of the lithium ion conductivity of the lithium-based polyanion particle (B) is not particularly limited.

  The lithium-based polyanion particles (B) represented by the above formula (V) or formula (VI) are combined with lithium composite oxide as primary particles constituting the layered lithium composite oxide secondary particles (A). Or may be directly combined with a part of the layered lithium composite oxide secondary particles (A) formed by aggregation of primary particles of the lithium composite oxide.

  The lithium-based polyanion particle (B) has carbon (c) supported on its surface. The amount of carbon (c) supported is preferably 0.1% by mass or more and less than 5% by mass in 100% by mass of the total amount of lithium-based polyanion particles (B) on which carbon (c) is supported. Specifically, when the lithium-based polyanion particles (B) are represented by the formula (V), the total amount of lithium-based polyanion particles (B) on which carbon (c) is supported is preferably 100% by mass. It is 0.5-5 mass%, More preferably, it is 1-5 mass%, More preferably, it is 1-4 mass%. When the lithium polyanion particles (B) are represented by the formula (VI), the total amount of lithium polyanion particles (B) on which carbon (c) is supported is preferably 0.1%. The content is not less than 4% by mass and more preferably 4% by mass, more preferably 0.1 to 3% by mass, and still more preferably 0.1 to 2% by mass.

  The content of the layered lithium composite oxide secondary particles (A), the content of lithium-based polyanion particles (B) having carbon (c) supported on the surface (including the amount of carbon (c) supported), and The mass ratio ((A) :( B)) is preferably 95: 5 to 50:50, more preferably 90:10 to 50:50, and still more preferably 90:10 to 60:40. is there.

  On the surface of the layered lithium composite oxide secondary particle (A) in the present invention, the lithium-based polyanion particle (B) is composited so as to cover only a part of the surface of the secondary particle. As a result, when the positive electrode slurry is made, the reason is not clear, but it is possible to effectively and efficiently suppress the increase in the viscosity of the slurry over time without covering the entire surface of the secondary particles. .

The state in which the lithium-based polyanion particles (B) cover only a part of the surface of the layered lithium composite oxide secondary particles (A) is the peak intensity ratio ((Ni2p ₃ ) by X-ray photoelectron spectroscopy (XPS). _{/ 2} peak intensity) / (P2p peak intensity + C1s peak intensity)), that is, Ni2p _3/2 peak intensity released from the layered lithium composite oxide secondary particles (A), and lithium-based polyanion particles ( It can be confirmed by the value of the ratio of the peak intensity of P2p and C1s released from B). Specifically, when the obtained positive electrode active material for a lithium ion secondary battery is irradiated with soft X-rays of several keV, the energy inherent in the element constituting the portion from the portion subjected to the soft X-ray irradiation. Since a photoelectron having a value is emitted, a peak intensity corresponding to trivalent Ni obtained by analyzing a peak of Ni2p _3/2 emitted from the layered lithium composite oxide secondary particles (A), lithium By comparing the sum of the peak intensities of P2p and C1s released from the polyanion particles (B), that is, the area ratio of the material serving as the surface of the positive electrode active material for the lithium ion secondary battery, that is, the lithium polyanion It can be seen that the particles (B) cover the layered lithium composite oxide secondary particles (A).

More specifically, the positive electrode active material for a lithium ion secondary battery in the present invention secures excellent discharge characteristics and safety in the viewpoint of suppressing the increase in viscosity of the positive electrode slurry over time, and in the obtained secondary battery. From this viewpoint, the peak intensity ratio ((Ni2p _3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) by XPS is more than 0.05 and less than 0.4, preferably 0. .05 and 0.37 or less, more preferably more than 0.05 and 0.35 or less.

The surface coverage of the layered lithium composite oxide secondary particles (A) by the lithium-based polyanion particles (B) can also be determined from the value of the peak intensity ratio. Specifically, the XPS peak intensity ratio when the entire surface of the layered lithium composite oxide secondary particles (A) is covered with the lithium-based polyanion particles (B) (surface coverage: 100 area%), The above-mentioned XPS peak intensity ratio with respect to the single type lithium composite oxide secondary particles (A) (surface coverage 0 area%) is determined, and the relational expression between the surface coverage and the XPS peak intensity ratio is determined so as to connect these two points. .
And the surface coverage (area%) by lithium type polyanion particle | grains (B) should just be calculated | required from the measurement result of the XPS peak intensity ratio regarding arbitrary positive electrode active materials for secondary batteries using the said relational expression.
An example of the above relational expression is shown in the following expression (1).
Surface coverage (area%) of the lithium secondary oxide (A) in the form of lithium-based polyanion particles (B) =
−208.3 × (XPS peak intensity ratio) +104.2 (1)

  For example, the surface coverage of the layered lithium composite oxide secondary particles (A) by the lithium-based polyanion particles (B) obtained by the above formula (1) is preferably a value corresponding to the above-described peak intensity ratio by XPS. More than 20 area% and less than 95 area%, more preferably more than 20 area% and not more than 90 area%, and still more preferably more than 20 area% and not more than 84 area%.

Further, sodium-based polyanion particles (E) formed by complexing with sodium composite oxide particles only on a part of the surface of the layered sodium composite oxide secondary particles (D) are represented by the following formula (VII):
NaCo _{g ′} M ⁷ _{i ′} PO ₄ (VII)
(In the formula (VII), M ⁷ represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. G ′ and i ′ are 0 <g '≦ 1, 0 ≦ i' ≦ 0.3, and 2g ′ + (valence of M ⁷ ) × i ′ = 2).
Or the following formula (VIII):
NaFe _{m ′} Mn _{n ′} M ⁸ _{o ′} PO ₄ (VIII)
(In the formula (VIII), M ⁸ represents Co, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. M ′, n ′, and o ′ are 0. ≦ m ′ ≦ 1, 0 ≦ n ′ ≦ 1, 0 ≦ o ′ ≦ 0.3, and m ′ + n ′ ≠ 0, and 2m ′ + 2n ′ + (valence of M ⁸ ) × o ′ = 2 Indicates the number satisfying.)
And is a compound that can provide good sodium ion conductivity. Furthermore, the sodium-based polyanion particle (E) represented by the above formula (VII) or formula (VIII) has carbon (c) supported on the particle surface, and the carbon (c) is derived from cellulose nanofibers. Carbon (c1) or carbon (c2) derived from a water-soluble carbon material may be used.

Specific examples of the sodium-based polyanion particles (E) represented by the above formula (VII) include NaCoPO ₄ and NaCo _0.25 Fe _0.25 PO ₄ .
Furthermore, specific examples of the sodium-based polyanion particles (E) represented by the above formula (VIII) include NaFe _0.2 Mn _0.8 PO ₄ , NaFe _0.9 Mn _0.1 PO ₄ , NaFe _0.15 Mn _0.75 Mg _0.1 PO ₄ , naFe _0.19 Mn _0.75 Zr _0.03 PO ₄ and the like, among naFe _0.2 Mn _0.8 PO ₄ are preferred.

  The average particle diameter of the sodium-based polyanion particles (E) represented by the above formula (VII) or formula (VIII) is complex with the sodium composite oxide particles on the surface of the sodium composite oxide secondary particles (D). From the viewpoint of conversion, the thickness is preferably 50 to 200 nm, and more preferably 70 to 150 nm.

The sodium ion anion conductivity of the sodium-based polyanion particles (E) represented by the above formula (VII) or formula (VIII) at a pressure of 20 MPa at 25 ° C. is 1 × 10 ⁻⁷ S / cm or more. Preferably, it is 1 × 10 ⁻⁶ S / cm or more. The upper limit value of the lithium ion conductivity of the sodium-based polyanion particles (E) is not particularly limited.

  The sodium-based polyanion particles (E) represented by the above formula (VII) or formula (VIII) are combined with the sodium composite oxide as the primary particles constituting the layered sodium composite oxide secondary particles (D). Or may be directly combined with a part of the sodium composite oxide secondary particles (D) formed by aggregation of the primary particles of the sodium composite oxide.

  The sodium-based polyanion particle (E) has carbon (c) supported on its surface. The amount of carbon (c) supported is preferably 0.1% by mass or more and less than 5% by mass, more preferably 100% by mass of sodium polyanion particles (E) in which carbon (c) is supported. Is 0.5-5 mass%, More preferably, it is 1-5 mass%.

  Mass of content of sodium composite oxide secondary particles (D) and content of sodium-based polyanion particles (E) having carbon (c) supported on the surface (including the supported amount of carbon (c)) The ratio ((D) :( E)) is preferably 95: 5 to 50:50, more preferably 90:10 to 50:50, and still more preferably 90:10 to 60:40.

  On the surface of the layered sodium composite oxide secondary particle (D) in the present invention, the sodium-based polyanion particle (E) is composited so as to cover only a part of the surface of the secondary particle. As a result, when the positive electrode slurry is made, the reason is not clear, but it is possible to effectively and efficiently suppress the increase in the viscosity of the slurry over time without covering the entire surface of the secondary particles. .

The state in which the sodium-based polyanion particles (E) cover only a part of the surface of the layered sodium composite oxide secondary particles (D) is the case where the lithium-based polyanion particles (B) are layered lithium composite oxide secondary As in the case where only a part of the surface of the particle (A) is coated, the peak intensity ratio ((peak intensity of Ni2p _3/2 ) / (peak intensity of P2p + C1s) by X-ray photoelectron spectroscopy (XPS) The peak intensity of Ni2p _3/2 released from the layered sodium composite oxide secondary particles (D) and the peak intensity of P2p and C1s released from the sodium-based polyanion particles (E) This can be confirmed by the ratio value.
Specifically, the positive electrode active material for sodium ion secondary battery in the present invention is from the viewpoint of suppressing the increase in the viscosity of the positive electrode slurry, and from the viewpoint of securing excellent discharge characteristics and safety in the obtained secondary battery. The peak intensity ratio by XPS ((Ni2p _3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) is more than 0.05 and less than 0.4, preferably more than 0.05. 0.37 or less, more preferably more than 0.05 and 0.35 or less.

The surface coverage of the layered sodium composite oxide secondary particles (D) by the sodium-based polyanion particles (E) is that of the layered lithium composite oxide secondary particles (A) by the lithium-based polyanion particles (B). It can be determined in the same manner as the surface coverage.
Specifically, for example, the surface coverage of the layered sodium composite oxide secondary particles (D) by the sodium-based polyanion particles (E) obtained by a method similar to the method using the formula (1) is preferably More than 20 area% and less than 95 area%, more preferably more than 20 area% and not more than 90 area%, and still more preferably more than 20 area% and not more than 84 area%.

  The said cellulose nanofiber used as the carbon source (c1) which may be carry | supported as carbon (c) on the surface of lithium type polyanion particle (B) or sodium type polyanion particle (E) is all plants. Carbon fiber (c1) derived from cellulose nanofibers, which is a skeletal component that occupies about 50% of the cell wall, and is a lightweight high-strength fiber that can be obtained by defibration of plant fibers constituting such cell walls to nano size. Has a periodic structure. The fiber diameter of the cellulose nanofiber is 1 nm to 100 nm, and has good dispersibility in water. In addition, since the cellulose molecular chain constituting the cellulose nanofiber has a periodic structure formed of carbon, the lithium-based polyanion particle (B) or the sodium-based polyanion particle (B) is combined with the polyanion particle while being carbonized. E) A solid positive electrode active material for lithium ion secondary batteries or a positive electrode active material for sodium ion secondary batteries having excellent cycle characteristics is imparted to the polyanion particles by being firmly supported on the surface. Can be obtained.

  The water-soluble carbon material as the carbon source (c2), which may be supported as carbon (c) on the surface of the lithium-based polyanion particles (B) or sodium-based polyanion particles (E), is 25 ° C. Means a carbon material that dissolves in 100 g of water in terms of carbon atom of the water-soluble carbon material in an amount of 0.4 g or more, preferably 1.0 g or more, and is carbonized to form the lithium-based polyanion particles (B) or It exists on the surface of the sodium-based polyanion particle (E). Examples of the water-soluble carbon material include one or more selected from saccharides, polyols, polyethers, and organic acids. More specifically, for example, monosaccharides such as glucose, fructose, galactose and mannose; disaccharides such as maltose, sucrose and cellobiose; polysaccharides such as starch and dextrin; ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol and butane Examples include polyols and polyethers such as diol, propanediol, polyvinyl alcohol, and glycerin; and organic acids such as citric acid, tartaric acid, and ascorbic acid. Among these, glucose, fructose, sucrose, and dextrin are preferable, and glucose is more preferable from the viewpoint of improving the solubility and dispersibility in a solvent and effectively functioning as a carbon material.

  In addition, atoms of carbon (c1) derived from cellulose nanofibers or carbon (c2) derived from a water-soluble carbon material present as carbon (c) on the surface of lithium-based polyanion particles (B) or sodium-based polyanion particles (E). The conversion amount (carbon loading amount) can be confirmed as the carbon amount measured using a carbon / sulfur analyzer for the lithium-based polyanion particles (B) or the sodium-based polyanion particles (E).

  The method for producing a positive electrode active material for a lithium ion secondary battery according to the present invention comprises layered lithium composite oxide secondary particles (A) and lithium-based polyanion particles (B) formed by supporting carbon (c) on the surface. It is only necessary to provide a step of mixing and adding them while applying compressive force and shearing force. The method for producing a positive electrode active material for a sodium ion secondary battery according to the present invention comprises a layered sodium composite oxide secondary particle (D) and sodium-based polyanion particles (E) having carbon (c) supported on the surface. ) May be mixed and combined while applying a compressive force and a shearing force.

  In the present invention, the layered lithium composite oxide secondary particles (A) and the lithium polyanion particles (B) are combined, or the layered sodium composite oxide secondary particles (D) and the sodium polyanion are combined. In the particle (E), a water-insoluble carbon powder (c3) other than carbon (c1) derived from cellulose nanofibers is simultaneously mixed as a carbon source, and the water-insoluble carbon powder (c3) is layered type lithium composite oxide secondary The particles (A) and lithium-based polyanion particles (B) may be combined, or the layered sodium composite oxide secondary particles (D) and the sodium-based polyanion particles (E) may be combined. The water-insoluble carbon powder (c3) is a carbon material different from the carbon (c2) derived from the water-soluble carbon material, and is water-insoluble (water at 25 ° C.) other than the carbon (c1) derived from cellulose nanofibers. The amount dissolved in 100 g is a carbon powder having conductivity of less than 0.4 g in terms of carbon atom of the water-insoluble carbon powder (c3). By combining this water-insoluble carbon powder (c3), the discharge characteristics when the positive electrode active material for lithium ion secondary batteries or the positive electrode active material for sodium ion secondary batteries of the present invention is used as a secondary battery are not degraded. In the positive electrode active material for a lithium ion secondary battery, a plurality of layers on the surface of the positive electrode active material for the lithium ion secondary battery or between the layered lithium composite oxide secondary particles (A) and the lithium-based polyanion particles (B) It exists so as to cover the lithium-based polyanion particles (B), or is interposed in the gap between the layered sodium composite oxide secondary particles (D) and the sodium-based polyanion particles (E) in the positive electrode active material for sodium ion secondary batteries, Or while existing so as to cover a plurality of sodium-based polyanion particles (E) on the surface of the positive electrode active material for sodium ion secondary battery, The degree of these composites is further strengthened, and the lithium-based polyanion particles (B) are separated from the layered lithium composite oxide secondary particles (A), or the layered sodium composite oxide secondary particles (D ) From the sodium-based polyanion particles (E) can be effectively suppressed.

  Examples of the water-insoluble carbon powder (c3) include graphite, amorphous carbon (Ketjen black, acetylene black, etc.), nanocarbon (graphene, fullerene, etc.), conductive polymer powder (polyaniline powder, polyacetylene powder, polythiophene powder). , Polypyrrole powder, etc.) and the like. Among them, the degree of complexation of layered lithium composite oxide secondary particles (A) and lithium-based polyanion particles (B) or layered sodium composite oxide secondary particles (D) to sodium-based polyanion particles (E) From the viewpoint of reinforcement, graphite, acetylene black, graphene, and polyaniline powder are preferable, and graphite is more preferable. The graphite may be any of artificial graphite (scaly, massive, earthy, graphene) or natural graphite.

  The average particle size of the water-insoluble carbon powder (c3) is preferably 0.5 to 20 μm, more preferably 1.0 to 15 μm, from the viewpoint of compositing.

  In the positive electrode active material for a lithium ion secondary battery of the present invention, water that is mixed and mixed at the same time when the layered lithium composite oxide secondary particles (A) and the lithium-based polyanion particles (B) are combined. The content of the insoluble carbon powder (c3) is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the layered lithium composite oxide secondary particles (A) and the lithium-based polyanion particles (B). Yes, more preferably 1 to 8 parts by mass, still more preferably 1 to 5 parts by mass.

  Further, the total amount of the lithium-based polyanion particles (B) on which the layered lithium composite oxide secondary particles (A) and carbon (c) are supported, and the carbon supported on the lithium-based polyanion particles (B). The mass ratio (((A) + (B)): ((c) + (c3))) to the total content of (c) and the water-insoluble carbon powder (c3) is preferably 99.5: 0. It is 5-90: 10, More preferably, it is 99: 1-92: 8, More preferably, it is 99: 1-95: 5.

  Further, in the positive electrode active material for the sodium ion secondary battery of the present invention, the layered sodium composite oxide secondary particles (D) and the sodium-based polyanion particles (E) are mixed and combined at the same time. The content of the water-insoluble carbon powder (c3) is preferably 0.5 to 24 mass with respect to 100 mass parts of the total amount of the layered sodium composite oxide secondary particles (D) and the sodium-based polyanion particles (E). Part, more preferably 1 to 16 parts by weight, still more preferably 1 to 10 parts by weight, and sodium on which the layered sodium composite oxide secondary particles (D) and carbon (c) are supported. Mass ratio of the total amount of the polyanion particles (E) and the total content of the carbon (c) and the water-insoluble carbon powder (c3) supported on the sodium polyanion particles (E) ((( ) + (E)): ((c) + (c3))) is preferably 99.5: 0.5 to 90:10, more preferably 99: 1 to 92: 8, even more preferably. Is 99: 1 to 95: 5.

  Next, the manufacturing method of the positive electrode active material for lithium ion secondary batteries or the positive electrode active material for sodium ion secondary batteries is demonstrated more concretely.

The manufacturing method of the positive electrode active material for lithium ion secondary batteries or the positive electrode active material for sodium ion secondary batteries includes the following steps (X) to (Z):
(X) A mixed powder containing a lithium compound or a sodium compound, a nickel compound, a cobalt compound, and a manganese compound is fired to obtain an NCM-based composite oxide secondary particle of formula (I) or formula (III) (A) Or get (D), or
A mixed powder containing a lithium compound or a sodium compound, a nickel compound, a cobalt compound, and an aluminum compound is fired, and the NCA-based composite oxide secondary particles (A) or (D) of formula (II) or formula (IV) )
(Y) Lithium compound or sodium compound, and phosphoric acid compound, further cobalt compound is subjected to a wet reaction to obtain lithium-based polyanion particles (B) or sodium-based polyanion particles (E), or
A step of obtaining a lithium-based polyanion particle (B) or a sodium-based polyanion particle (E) by subjecting a lithium compound or a sodium compound, and a phosphate compound, and further an iron compound and / or a manganese compound to a wet reaction;
(Z) The lithium-based polyanion particles obtained in step (Y) on the NCM-based composite oxide secondary particles or NCA-based composite oxide secondary particles (A) or (D) obtained in step (X) (B) or sodium-based polyanion particles (E) are added and mixed while applying compressive force and shearing force to form a composite, or the NCM-based composite oxide obtained in step (X) Secondary particles or NCA-based composite oxide secondary particles (A) or (D), lithium-based polyanion particles (B) or sodium-based polyanion particles (E) obtained in step (Y), and water-insoluble carbon powder ( a step of adding c3) and mixing to add a compressive force and a shearing force to form a composite.

In step (X), a mixed powder containing a lithium compound or sodium compound, a nickel compound, a cobalt compound, and a manganese compound is baked, and the NCM composite oxide secondary particles of formula (I) or formula (III) (A) or (D) is obtained, or a mixed powder containing a lithium compound or a sodium compound, a nickel compound, a cobalt compound, and an aluminum compound is fired to obtain an NCA system of the formula (II) or the formula (IV) In this step, the composite oxide secondary particles (A) or (D) are obtained.
In the description of the step (X), the positive electrode active material for a lithium ion secondary battery represented by the above formula (I) or the formula (II) will be specifically described in order to avoid complicated notation. Regarding the method for producing a positive electrode active material for a sodium ion secondary battery represented by the above formula (III) or formula (IV), the term “lithium” in the method for producing a positive electrode active material for a lithium ion secondary battery shown below is used. Replace with “sodium”. The lithium-based polyanion particles (B) or sodium-based polyanion particles (E) are also simply referred to as “polyanion particles”.

In step (X), the mixed powder containing a lithium compound, a nickel compound, a cobalt compound, and a manganese compound is fired to obtain the NCM-based composite oxide secondary particles (A) of the formula (I), or In this step, the mixed powder containing a lithium compound, a nickel compound, a cobalt compound, and an aluminum compound is fired to obtain the NCA-based composite oxide secondary particles (A) of the formula (II).

In order to obtain the NCM-based composite oxide secondary particles (A), a raw material compound, for example, a nickel compound, a cobalt compound, and a manganese compound is dissolved in water so as to have a desired composite oxide composition, and an aqueous solution A is obtained. Get. Examples of the nickel compound, cobalt compound, and manganese compound include sulfates, nitrates, carbonates, acetates, oxalates, oxides, hydroxides, and halides of the metal elements. Specific examples include nickel sulfate, cobalt sulfate, manganese sulfate, nickel acetate, cobalt acetate, and manganese acetate, but are not limited thereto.
In this process, as necessary, Mg, Ti, Nb are used as metal elements for substituting a part of the layered lithium metal composite oxide constituting the active material so as to obtain a desired composite oxide composition. Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi, and Ge are selected from one or more elements. It may be mixed.

  Next, an alkaline solution is added to the aqueous solution A to form an aqueous solution B, and the dissolved metal component is coprecipitated by a neutralization reaction to obtain a metal composite hydroxide. The alkaline solution is dropped in an amount sufficient to maintain the pH of the aqueous solution B at 10-14. As the alkaline solution, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia or the like can be used, but sodium hydroxide, sodium carbonate or a mixed solution thereof is preferably used.

  The aqueous solution B is stirred to produce a metal composite hydroxide, and the temperature of the aqueous solution B during the reaction is preferably 30 ° C. or higher, more preferably 30 to 60 ° C. Moreover, 30 minutes-120 minutes are preferable and, as for the stirring time of the aqueous solution B, 30-60 minutes are more preferable.

  After stirring, the aqueous solution B is filtered to recover the metal composite hydroxide. The recovered metal composite hydroxide is preferably washed with water and then dried.

  Next, the NCM composite oxide can be obtained by dry-mixing the metal composite hydroxide and the lithium compound so as to have a desired composite oxide composition and firing in an oxygen atmosphere. As the lithium compound, for example, lithium hydroxide or a hydrate thereof, lithium peroxide, lithium nitrate, lithium carbonate and the like can be preferably used. For the dry mixing of the metal composite hydroxide and the lithium compound, a normal dry mixer or a mixing granulator such as a ball mill or a V blender can be used, and it is more preferable to use a planetary ball mill capable of revolving.

  The firing of the mixture of the metal composite hydroxide and the lithium compound is preferably performed in two stages (temporary firing and main firing). By removing the thermal decomposition components such as water molecules and carbon dioxide from the hydroxide and carbonate in the mixture by preliminary calcination and then performing the main calcination, an NCM composite oxide can be obtained efficiently. Although it does not specifically limit as conditions for temporary baking, It is preferable that a temperature increase rate is 1-20 degrees C / min from room temperature. The atmosphere is preferably an air atmosphere or an oxygen atmosphere. Moreover, it is preferable that a calcination temperature is 700 to 1000 degreeC, and it is more preferable that it is 650 to 750 degreeC. Furthermore, the firing time is preferably 3 to 20 hours, more preferably 4 to 6 hours.

The conditions for the next main baking are not particularly limited, but after the temporary baking, the temporary baking products crushed in a mortar or the like are again heated from room temperature at a heating rate of 1 to 20 ° C./min. Is done. The atmosphere at this time is preferably an air atmosphere or an oxygen atmosphere. Moreover, it is preferable that it is 700 to 1200 degreeC, and, as for baking temperature, it is more preferable that it is 750 to 900 degreeC. Furthermore, the firing time is preferably 3 to 20 hours, and more preferably 8 to 10 hours.
For this two-stage firing, an electric furnace, a rotary kiln, a tubular furnace, a pusher furnace, etc. adjusted to a gas atmosphere with an oxygen concentration of 20% by mass or more such as an oxygen atmosphere, a dehumidified and decarboxylated dry air atmosphere, etc. are used. be able to.

  The average particle size of the primary particles of the NCM composite oxide can be controlled by adjusting the firing temperature of the main firing. In order to set the average particle size of the primary particles of the NCM composite oxide to 50 nm to 500 nm, the firing temperature is preferably 700 ° C. to 1000 ° C., more preferably 750 ° C. to 900 ° C.

  Finally, the obtained fired product is washed with water, filtered and dried to obtain NCM composite oxide secondary particles (A). Here, the drying is performed in two stages, and the first stage of drying is performed until the water content in the NCM-based composite oxide secondary particles (water content measured at a vaporization temperature of 300 ° C.) becomes 1% by mass or less. It is preferable to dry at a temperature of not higher than ° C., and then to perform the second stage drying at a temperature of 120 ° C. or higher. The moisture content may be measured using, for example, a Karl Fischer moisture meter.

Next, the case where the NCA-based composite oxide secondary particles (A) are obtained in the step (X) will be specifically described.
In order to obtain the NCA-based composite oxide secondary particles (A), a raw material compound such as a nickel compound, a cobalt compound, and an aluminum compound is dissolved in water so as to have a desired composite oxide composition, and an aqueous solution A is obtained. 'Get. Examples of such nickel compounds, cobalt compounds, and aluminum compounds include sulfates, nitrates, carbonates, acetates, oxalates, oxides, hydroxides, and halides of the metal elements. Specific examples include, but are not limited to, nickel sulfate, cobalt sulfate, aluminum sulfate, nickel acetate, cobalt acetate, and aluminum acetate. In this process, as necessary, Mg, Ti, Nb are used as metal elements for substituting a part of the layered lithium metal composite oxide constituting the active material so as to obtain a desired composite oxide composition. Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Ge are mixed in one or more elements. May be.

  Next, an alkaline solution is added to the aqueous solution A ′ to obtain an aqueous solution B ′, and the dissolved metal moisture is coprecipitated by a neutralization reaction to obtain a metal composite hydroxide. The alkaline solution is dropped in an amount sufficient to maintain the pH of the aqueous solution B ′ at 10-14. As the alkaline solution, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia or the like can be used, but it is preferable to use ammonia, sodium hydroxide, sodium carbonate or a mixed solution thereof.

  The aqueous solution B ′ is stirred to produce a metal composite hydroxide. The temperature of the aqueous solution B ′ during this reaction is preferably 40 ° C. or higher, more preferably 40 ° C. to 60 ° C. Further, the stirring time of the aqueous solution B ′ is preferably 30 to 120 minutes, and more preferably 30 to 60 minutes.

  In order to obtain a metal composite hydroxide having a high bulk density, an oxidizing agent such as sodium hypochlorite or hydrogen peroxide may be further added to the aqueous solution B ′ after the reaction.

After stirring, the aqueous solution B ′ is filtered to recover the metal composite hydroxide. The recovered metal composite hydroxide is preferably fired to form a metal composite oxide. By reacting with the lithium compound as the metal composite oxide, the quality of the obtained NCA-based composite oxide can be stabilized and can be reacted uniformly and sufficiently with lithium.
The firing conditions for obtaining the metal composite oxide are not particularly limited. For example, the firing may be performed in an air atmosphere at a temperature of preferably 500 ° C. to 1100 ° C., more preferably 600 to 900 ° C.

  Next, an NCA-based composite oxide can be obtained by dry-mixing the metal composite oxide and the lithium compound so as to obtain a desired composite oxide composition and firing in an oxygen atmosphere. The lithium compound is not particularly limited, and for example, lithium hydroxide or a hydrate thereof, lithium peroxide, lithium nitrate, lithium carbonate and the like can be preferably used. For the dry mixing of the metal composite oxide and the lithium compound, an ordinary dry mixer or a mixing granulator such as a ball mill or a V blender can be used. For firing, an oxygen atmosphere, dehumidification and decarboxylation are performed. An electric furnace, a rotary kiln, a tubular furnace, a pusher furnace, or the like adjusted to a gas atmosphere having an oxygen concentration of 20% by mass or more such as a dry air atmosphere can be used.

In the firing of the mixture of the metal composite oxide and the lithium compound, the firing temperature is preferably 650 ° C to 850 ° C, and more preferably 700 ° C to 800 ° C. At a firing temperature of less than 650 ° C., the resulting NCA-based complex oxide crystals are undeveloped and structurally unstable, and the structure is easily destroyed by charge / discharge. On the other hand, when the firing temperature exceeds 850 ° C., the layered structure of the NCA-based composite oxide collapses, making it difficult to insert and desorb lithium ions. The firing time is preferably 5 to 20 hours, and more preferably 6 to 10 hours.
Furthermore, in order to remove the crystal water or carbonic acid of the lithium compound, it is preferable to perform two-stage calcination as in the case of the NCM-based composite oxide. Subsequently, the second stage main firing may be performed at 650 ° C. to 850 ° C. for 5 hours or more.

Finally, the obtained fired product is washed with water, filtered and dried to obtain NCA-based composite oxide secondary particles (A). The slurry concentration when the fired product is washed with water is preferably 200 to 4000 g / L, and more preferably 500 to 2000 g / L. When the slurry concentration is less than 200 g / L, lithium is desorbed from the secondary particles of the NCA-based composite oxide.
In addition, when the water used for washing contains a large amount of carbon dioxide, lithium carbonate precipitates on the secondary particles of the NCA-based composite oxide, so the electrical conductivity of the water used for washing is less than 10 μS / cm. Preferably, water of 1 μS / cm or less is more preferable.

  In this invention, in this process (X), the drying performed after water washing and filtration needs to be performed in two steps. The first stage drying is performed at 90 ° C. or less until the moisture in the secondary particles (moisture ratio measured at a vaporization temperature of 300 ° C.) is 1% by mass or less, and then the second stage drying is performed at 120 ° C. This is done.

In the step (Y) following the step (X), a lithium compound or sodium compound, a phosphate compound, and further a cobalt compound are subjected to a wet reaction to form a lithium-based polyanion particle (B) or a sodium-based polyanion particle (E Or by subjecting a lithium compound or sodium compound, and a phosphate compound, and further an iron compound and / or a manganese compound to a wet reaction, to obtain a lithium-based polyanion particle (B) or a sodium-based polyanion particle (E). It is the process of obtaining.
Hereinafter, in order to avoid complicated notation, as an example of the step (Y), using an iron compound and a manganese compound, the lithium-based polyanion particles (B) represented by the above formula (VI) are obtained. This will be specifically described.
When obtaining the lithium-based polyanion particles (B) represented by the above formula (V), the term “iron compound and / or manganese compound” in the step (Y) may be replaced with “cobalt compound”. When obtaining the sodium-based polyanion particles (E) of the above formula (VII) or formula (VIII), the term “lithium” in the step (Y) is replaced with “sodium”, The term “compound and / or manganese compound” may be replaced with “cobalt compound”.

More specifically, the step (Y) includes the following (i) to (iii):
(I) a step of obtaining a composite (a-2) by mixing a phosphoric acid compound or a silicic acid compound with a mixture (a-1) containing a lithium compound;
(Ii) The composite (a-4) obtained by subjecting the obtained composite (a-2) and slurry water (a-3) containing a metal salt containing at least an iron compound or a manganese compound to a hydrothermal reaction And (iii) a step of firing the obtained composite (a-4) in a reducing atmosphere or an inert atmosphere.

Step (i) is a step of obtaining a composite (a-2) by mixing a phosphate compound with a mixture (a-1) containing a lithium compound.
Examples of the lithium compound that can be used include lithium hydroxide (for example, LiOH, LiOH.H ₂ O), lithium carbonate, lithium sulfate, and lithium acetate. Of these, lithium hydroxide is preferable.
The content of the lithium compound in the mixture (a-1) is preferably 5 to 50 parts by mass, more preferably 7 to 45 parts by mass with respect to 100 parts by mass of water. More specifically, the content of the lithium compound in the mixture (a-1) is preferably 5 to 50 parts by mass and more preferably 10 to 45 parts by mass with respect to 100 parts by mass of water.

  In order to obtain lithium-based polyanion particles in which carbon (c1) derived from cellulose nanofibers is supported, in the step (i), a lithium compound is contained instead of the mixture (a-1) and cellulose nanofibers are contained. A mixture (a-1) ′ containing may be used. The content of cellulose nanofibers in the mixture (a-1) ′ is preferably 0.5 to 15 parts by mass, and more preferably 0, for example, with respect to 100 parts by mass of water in the mixture (a-1) ′. 8 to 10 parts by mass.

  Here, when the carbon supported by the lithium-based polyanion particles is carbon (c2) derived from a water-soluble carbon material, both carbon (c1) derived from cellulose nanofibers and carbon (c2) derived from a water-soluble carbon material are combined. In order to obtain supported lithium-based polyanion particles, the term “cellulose nanofiber” in steps (i) to (iii) is replaced with “water-soluble carbon material” or “cellulose nanofiber and water-soluble carbon material”. ".

  It is preferable to stir the mixture (a-1) in advance before mixing the phosphoric acid compound with the mixture (a-1). The stirring time of the mixture (a-1) is preferably 1 to 15 minutes, more preferably 3 to 10 minutes. Moreover, the temperature of a mixture (a-1) becomes like this. Preferably it is 20-90 degreeC, More preferably, it is 20-70 degreeC.

Examples of the phosphoric acid compound used in the step (i) include orthophosphoric acid (H ₃ PO ₄ , phosphoric acid), metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, ammonium phosphate, and ammonium hydrogen phosphate. . Of these, phosphoric acid is preferably used, and is preferably used as an aqueous solution having a concentration of 70 to 90% by mass. In this process (i), when mixing phosphoric acid with the mixture (a-1), it is preferable to add phosphoric acid dropwise while stirring the mixture (a-1). By adding dropwise phosphoric acid dropwise to the mixture (a-1), the reaction proceeds well in the mixture (a-1), and the composite (a-2) is uniformly dispersed in the slurry. It is also possible to effectively prevent the complex (a-2) from being aggregated unnecessarily.

The dropping rate of phosphoric acid into the mixture (a-1) is preferably 15 to 50 mL / min, more preferably 20 to 45 mL / min, and further preferably 28 to 40 mL / min. Moreover, the stirring time of the mixture (a-1) while dropping phosphoric acid is preferably 0.5 to 24 hours, and more preferably 3 to 12 hours. Furthermore, the stirring speed of the mixture (a-1) while dropping phosphoric acid is preferably 200 to 700 rpm, more preferably 250 to 600 rpm, and further preferably 300 to 500 rpm.
In addition, when stirring a mixture (a-1), it is preferable to cool below to the boiling point temperature of a mixture (a-1). Specifically, cooling to 80 ° C. or lower is preferable, and cooling to 20 to 60 ° C. is more preferable.

  The mixture (a-1) after mixing the phosphoric acid compound preferably contains 2.7 to 3.3 mol of lithium per mol of phosphoric acid, and preferably contains 2.8 to 3.1 mol of lithium. Is more preferable.

By purging nitrogen to the mixture (a-1) after mixing the phosphoric acid compound, the reaction in the mixture is completed, and the complex (a-2) which is a precursor of the polyanion particles is obtained. Formed in the mixture. When nitrogen is purged, the reaction can proceed while the dissolved oxygen concentration in the mixture (a-1) is reduced, and the dissolved oxygen in the mixture containing the resulting complex (a-2) Since the concentration is also effectively reduced, oxidation of iron compounds, manganese compounds, etc. added in the next step can be suppressed. In the mixture containing the complex (a-2), the precursor of the polyanion particles exists as fine dispersed particles. Such a composite (a-2) is obtained as a composite of trilithium phosphate (Li ₃ PO ₄ ) and cellulose nanofibers.

The pressure for purging nitrogen is preferably 0.1 to 0.2 MPa, more preferably 0.1 to 0.15 MPa. Moreover, the temperature of the mixture (a-1) after mixing a phosphoric acid compound becomes like this. Preferably it is 20-80 degreeC, More preferably, it is 20-60 degreeC. Moreover, reaction time becomes like this. Preferably it is 5 to 60 minutes, More preferably, it is 15 to 45 minutes.
Moreover, when purging nitrogen, it is preferable to stir the mixture (a-1) after mixing a phosphoric acid compound from a viewpoint of making reaction progress favorable. The stirring speed at this time is preferably 200 to 700 rpm, more preferably 250 to 600 rpm.

  Further, from the viewpoint of more effectively suppressing the oxidation on the surface of the dispersed particles of the composite (a-2) and miniaturizing the dispersed particles, dissolution in the mixture (a-1) after mixing the phosphoric acid compound. The oxygen concentration is preferably 0.5 mg / L or less, more preferably 0.2 mg / L or less.

  In step (ii), the composite (a-2) obtained in step (i) and slurry water (a-3) containing a metal salt containing at least an iron compound or a manganese compound are subjected to a hydrothermal reaction. And obtaining the composite (a-4). The composite (a-2) obtained by the above step (i) is used as a precursor of polyanion particles in the form of a mixture, and a metal salt containing at least an iron compound or a manganese compound is added thereto, and slurry water ( It is preferable to use as a-3). As a result, the target polyanion particles become very fine particles while simplifying the process. Further, when the above mixture (a-1) ′ containing cellulose nanofibers is used in step (i), it becomes possible to efficiently carry carbon derived from cellulose nanofibers on such polyanion particles in the subsequent step, Useful polyanion particles can be obtained.

  Examples of iron compounds that can be used include iron acetate, iron nitrate, and iron sulfate. These may be used alone or in combination of two or more. Among these, iron sulfate is preferable from the viewpoint of improving the battery characteristics of the polyanion particles.

  Examples of manganese compounds that can be used include manganese acetate, manganese nitrate, and manganese sulfate. These may be used alone or in combination of two or more. Among these, manganese sulfate is preferable from the viewpoint of improving the battery characteristics of the polyanion particles.

When both an iron compound and a manganese compound are used as the metal salt, the use molar ratio of these manganese compound and iron compound (manganese compound: iron compound) is preferably 99: 1 to 1:99, more preferably 90. : 10 to 10:90. Moreover, the total addition amount of these iron compounds and manganese compounds is preferably 0.99 to 1.01 mol, more preferably 1 mol of Li ₃ PO ₄ contained in the slurry water (a-3). Is 0.995 to 1.005 mol.

Further, if necessary, as a metal salt, other than an iron compound and manganese compound metal (M ⁶⁾ salts may be used. M ⁶ in the metal salt has the same meaning as M ⁶ in formula (VI), as such a metal salt, can be used sulfates, halides, organic acid salts, and hydrates thereof. These may be used alone or in combination of two or more. Among them, it is more preferable to use a sulfate from the viewpoint of improving battery physical properties.
When these metal (M ⁶ ) salts are used, the total amount of iron compound, manganese compound, and metal (M ⁶ ) salt added is phosphoric acid in the complex (a-2) obtained in the step (i). The amount is preferably 0.99 to 1.01 mole, more preferably 0.995 to 1.005 mole relative to 1 mole.

  The amount of water used in the hydrothermal reaction is phosphoric acid contained in the slurry water (a-3) from the viewpoints of the solubility of the metal salt used, the ease of stirring, the efficiency of synthesis, and the like. Preferably it is 10-30 mol with respect to 1 mol of ion, More preferably, it is 12.5-25 mol.

In step (ii), the order of adding the iron compound, manganese compound and metal (M ⁶ ) salt is not particularly limited. Moreover, while adding these metal salts, you may add antioxidant as needed. As such an antioxidant, sodium sulfite (Na ₂ SO ₃ ), sodium hydrosulfite (Na ₂ S ₂ O ₄ ), aqueous ammonia and the like can be used. The addition amount of the antioxidant is 1 in total from the viewpoint of preventing the formation of polyanion particles by being excessively added and the iron compound, the manganese compound, and the metal (M ⁶ ) salt used as necessary. Preferably it is 0.01-1 mol with respect to mol, More preferably, it is 0.03-0.5 mol.

The content of the complex (a-4) in the slurry (a-3) obtained by adding an iron compound, a manganese compound, and a metal (M ⁶ ) salt or an antioxidant used as necessary is preferably It is 10-50 mass%, More preferably, it is 15-45 mass%, More preferably, it is 20-40 mass%.

The hydrothermal reaction in process (ii) should just be 100 degreeC or more, and 130-180 degreeC is preferable. The hydrothermal reaction is preferably carried out in a pressure vessel, and when the reaction is carried out at 130 to 180 ° C, the pressure at this time is preferably 0.3 to 0.9 MPa, and the reaction is carried out at 140 to 160 ° C. The pressure is preferably 0.3 to 0.6 MPa. The hydrothermal reaction time is preferably 0.1 to 48 hours, more preferably 0.2 to 24 hours.
The obtained composite (a-4) is a composite containing polyanion particles represented by the above formula (VI), or, when cellulose nanofibers are used, contains such polyanion grains and cellulose nanofibers. It is a composite and can be isolated as composite particles (primary particles) containing cellulose nanofibers by filtration, washing with water, and drying. As the drying means, freeze drying or vacuum drying is used.

The BET specific surface area of the obtained composite (a-4) is preferably 5 to 40 m ² / g, more preferably 5 to ²⁰ m ² / g, from the viewpoint of effectively reducing the amount of adsorbed moisture. If the BET specific surface area of the composite (a-4) is less than 5 m ² / g, the polyanion particles may become too large. On the other hand, if the BET specific surface area exceeds 40 m ² / g, the amount of adsorbed moisture of the positive electrode active material for secondary batteries may increase and affect battery characteristics.

  In the next step (iii), the complex (a-4) obtained in step (ii) is baked in a reducing atmosphere or an inert atmosphere, and a lithium-based polyanion containing carbon (c1) derived from cellulose nanofibers. This is a step of obtaining particles (B). Further, when the cellulose nanofiber is used, the lithium-based polyanion particle (B) in which the carbon (c1) derived from the cellulose nanofiber is firmly supported on the surface is obtained through this step (III). Can be obtained.

  The firing temperature is preferably 500 to 800 ° C, more preferably 600 to 770 ° C, and even more preferably 650 to 750 ° C, from the viewpoint of effectively carbonizing the cellulose nanofibers. The firing time is preferably 10 minutes to 3 hours, more preferably 30 minutes to 1.5 hours.

  In the step (Z), the lithium obtained in the step (Y) is added to the NCM composite oxide secondary particles or the NCA composite oxide secondary particles (A) or (D) obtained in the step (X). In the process of adding a polyanion particle (B) or a sodium polyanion particle (E) and, if necessary, a water-insoluble carbon powder (c3) and mixing them while adding compressive force and shear force to form a composite is there.

  In the step (Z), before the composite treatment, the layered composite oxide secondary particles (A) or (D) and the lithium-based polyanion particles (B) or the sodium-based polyanion particles (E) are further necessary. The mixture of the water-insoluble carbon powder (c3) added accordingly is preferably thoroughly dry-mixed. As a dry mixing method, mixing by a normal dry mixer such as a ball mill or a V blender is preferable, and mixing by a planetary ball mill capable of revolving is more preferable.

  Next, the layered composite oxide secondary particles (A) or (D), the lithium-based polyanion particles (B), or the sodium-based polyanion particles (E), which are dry-mixed, are added as necessary. The mixture of the water-insoluble carbon powder (c3) is a composite that is effectively combined with the composite oxide particles only on a part of the surface of the layered composite oxide secondary particles (A) or (D). From the viewpoint of obtaining, it is preferable to mix while applying compressive force and shearing force. The process of mixing while applying a compressive force and a shearing force is preferably performed in a closed container equipped with an impeller, a rotor tool, and the like.

For example, when using Nobilta (manufactured by Hosokawa Micron Corporation), which is a dry particle composite apparatus equipped with an impeller for the above-mentioned composite treatment, the rotational speed of the impeller is such that the layered composite oxide secondary particles (A) or ( From the viewpoint of obtaining a composite of D) and the polyanion particles (B) or (E), and further the water-insoluble carbon powder (c3), it is preferably 2000 to 6000 rpm, and more preferably 4000 to 6000 rpm. The mixing time is preferably 1 to 10 minutes, more preferably 5 to 10 minutes.
In addition, when using an Eirich intensive mixer (manufactured by Eirich Japan), which is a high-speed stirring mixer equipped with a rotor tool for such complexing, the rotational speed of the rotor tool is preferably 2000 to 8000 rpm, and more Preferably it is 4000-8000 rpm. Further, the mixing time is preferably 1 to 10 minutes, more preferably 3 to 10 minutes.

In the step (Z), the processing time and / or the rotational speed of the impeller and the like when performing the mixing process while applying the compression force and the shearing force are determined as follows. Or it is necessary to adjust suitably according to the quantity of the mixture of (D), polyanion particle (B) or (E), and also water-insoluble carbon powder (c3). Then, by operating the container, it becomes possible to perform a process of compounding the mixture while applying a compressive force and a shearing force to the mixture between the impeller and the inner wall of the container. A positive electrode active material for a lithium ion secondary battery or a positive electrode active material for a sodium ion secondary battery in which the polyanion particle and the water-insoluble carbon powder (c3) are combined only on a part of the surface of the secondary particle is obtained. be able to.
For example, when the complexing process is performed for 1 to 10 minutes in an airtight container equipped with an impeller rotating at a rotational speed of 2000 to 6000 rpm, the amount of the mixture to be charged into the container is an effective container (of the airtight container equipped with an impeller). , A container corresponding to a part capable of accommodating the above mixture) per cm ³ , preferably 0.1 to 0.7 g, more preferably 0.15 to 0.4 g.

Examples of the apparatus including a sealed container that can easily perform the composite treatment while applying the compressive force and the shear force include a high-speed shear mill, a blade-type kneader, and a high-speed mixer. Is, for example, particle design device COMPOSI, mechanohybrid, high-performance fluidized mixer FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.), fine particle composite device mechanofusion, nobilta (manufactured by Hosokawa Micron), surface reformer miraro, hybridization system (Manufactured by Nara Machinery Co., Ltd.) and Eirich Intensive Mixer (made by Nihon Eirich) can be suitably used.
As processing conditions for the above complexing treatment, the treatment temperature is preferably 5 to 80 ° C, more preferably 10 to 50 ° C. The treatment atmosphere is not particularly limited, but is preferably an inert gas atmosphere or a reducing gas atmosphere.

  In addition, the lithium-containing polyanion particles (B) or the sodium-based polyanion particles (E) are added as necessary only in part of the surface of the layered composite oxide secondary particles (A) or (D). The degree to which the water-insoluble carbon powder (c3) is combined can be evaluated by X-ray photoelectron spectroscopy (XPS).

  As a secondary battery which is a lithium ion secondary battery or a sodium ion secondary battery to which the positive electrode for a secondary battery containing the positive electrode active material for a secondary battery of the present invention can be applied, a positive electrode, a negative electrode, an electrolyte and a separator are essential. If it is set as a structure, it will not specifically limit.

  The positive electrode of the lithium ion secondary battery or the sodium ion secondary battery is composed of a positive electrode active material for a secondary battery of the present invention, a conductive aid such as carbon black, and a binder (binder) such as polyvinylidene fluoride, N- A solvent such as methyl-2-pyrrolidone is added and sufficiently kneaded to obtain a positive electrode slurry, which is then applied onto a current collector such as an aluminum foil, and then consolidated by a roller press or the like and dried. Since the positive electrode active material for a secondary battery according to the present invention can effectively suppress the viscosity increase with time of the positive electrode slurry obtained by adjustment, the current collector is several days after the adjustment of the positive electrode slurry. Even when applied to the top, the thickness can be easily made uniform.

  The negative electrode of the lithium ion secondary battery or the sodium ion secondary battery is not particularly limited by the material configuration as long as it can occlude lithium ions or sodium ions during charging and can be released during discharging. A material structure can be used. For example, a carbon material such as lithium metal, sodium metal, graphite, or amorphous carbon. It is preferable to use an electrode formed of an intercalating material capable of electrochemically inserting and extracting lithium ions or sodium ions, particularly a carbon material.

  The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte solution of a lithium ion secondary battery or a sodium ion secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones Nitriles, lactones, oxolane compounds and the like can be used.

The type of the supporting salt is not particularly limited, but in the case of a lithium ion secondary battery, an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , an organic material selected from LiC (SO ₃ CF ₃ ) ₂ and LiN (SO ₃ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ and LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) It is preferably at least one of a salt and a derivative of the organic salt. In the case of a sodium ion secondary battery, an inorganic salt selected from NaPF ₆ , NaBF ₄ , NaClO ₄ and NaAsF ₆ , a derivative of the inorganic salt, NaSO ₃ CF ₃ , NaC (SO ₃ CF ₃ ) ₂ and NaN (SO ₃ CF ₃ ) ₂ , NaN (SO ₂ C ₂ F ₅ ) ₂ and NaN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and at least one of derivatives of the organic salt It is preferable.

  The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.

The solid electrolyte electrically insulates the positive electrode and the negative electrode and exhibits high lithium ion conductivity. For example, La _0.51 Li _0.34 TiO _2.94 , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , 50Li ₄ SiO ₄ .50Li ₃ BO ₃ , Li _2.9 PO _3.3 N _0.46 , Li _3.6 Si _0.6 P _0.4 O ₄ , Li _1.07 Al _0.69 Ti _1.46 (PO ₄ ) ₃ , Li _{1 .5 Al 0.5 Ge 1.5 (PO 4} ) 3, Li 10 GeP 2 S 12, Li 3.25 Ge 0.25 P 0.75 S 4, 30Li 2 S · 26B 2 S 3 · 44LiI, 63Li _{2 S · 36SiS 2 · 1Li 3} PO 4, 57Li 2 S · 38SiS 2 · 5Li 4 SiO 4, 70Li 2 S · 30P 2 S 5, 50Li 2 S · 50GeS 2, Li 7 P 3 S 11, Li _3.25 P _0.95 S ₄ may be used.

  The shape of the lithium ion secondary battery or sodium ion secondary battery having the above configuration is not particularly limited, and various shapes such as a coin shape, a cylindrical shape, and a square shape, and an indeterminate sealed in a laminate outer package. It may be a shape.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Production Example A: Production of Secondary Particles of Li-NCM Complex Oxide (Li-NCM-A)]
After mixing 263 g of nickel sulfate hexahydrate, 281 g of cobalt sulfate heptahydrate, 241 g of manganese sulfate pentahydrate, and 3 L of water so that the molar ratio of Ni: Co: Mn is 1: 1: 1 Then, 25% aqueous ammonia was added dropwise to the mixture at a dropping rate of 300 ml / min to obtain a slurry A1 containing a metal composite hydroxide having a pH of 11.
Next, the slurry A1 was filtered and dried to obtain a metal composite hydroxide mixture B1, and then 37 g of lithium carbonate was mixed with the mixture B1 by a ball mill to obtain a powder mixture C1.
The obtained powder mixture C1 was calcined at 800 ° C. for 5 hours in an air atmosphere and pulverized, and then fired at 800 ° C. for 10 hours in an air atmosphere as main firing, to obtain a Li-NCM composite oxide (LiNi Secondary particles A of _0.33 Co _0.33 Mn _0.34 O ₂ ) were obtained. (Average particle size of secondary particles: 10 μm)
Hereinafter, the Li-NCM composite oxide A is referred to as Li-NCM-A.

[Production Example 001: Production of lithium-based polyanion particles (LMP-A)]
1272 g of LiOH.H ₂ O and 4 L of water were mixed to obtain slurry A001. Subsequently, 1153 g of 85% phosphoric acid aqueous solution was dropped at 35 mL / min while stirring the obtained slurry A001 for 3 minutes while maintaining the temperature at 25 ° C., followed by cellulose nanofiber (Cerish KY-100G, Daicel Finechem). (Manufactured, fiber diameter: 4 to 100 nm) was added and stirred at a speed of 400 rpm for 12 hours to obtain a slurry B001 containing Li ₃ PO ₄ .
The obtained slurry B001 was purged with nitrogen so that the dissolved oxygen concentration of the slurry B001 was 0.5 mg / L, and then 1688 g of MnSO ₄ · 5H ₂ O and 834 g of FeSO ₄ · 7H ₂ O were added to the total amount of the slurry B001. As a result, slurry C001 was obtained. The molar ratio of MnSO ₄ and FeSO ₄ added (manganese compound: iron compound) was 70:30.
Next, the obtained slurry C001 was put into an autoclave and subjected to a hydrothermal reaction at 170 ° C. for 1 hour. The pressure in the autoclave was 0.8 MPa. After the hydrothermal reaction, the produced crystal was filtered, and then washed with 12 parts by mass of water with respect to 1 part by mass of the crystal. The washed crystal was lyophilized at −50 ° C. for 12 hours to obtain a complex D001.
1000 g of the obtained composite D001 was collected, and 1 L of water was added thereto to obtain a slurry E001. The obtained slurry E001 was subjected to a dispersion treatment for 1 minute with an ultrasonic stirrer (T25, manufactured by IKA) to uniformly color the whole, and then a spray dryer (MDL-050M, manufactured by Fujisaki Electric Co., Ltd.) was used. Then, it was subjected to spray drying to obtain a granulated body F001.
The obtained granule F001 was calcined at 700 ° C. for 1 hour in an argon hydrogen atmosphere (hydrogen concentration: 3%), and lithium manganese phosphate containing 2.0% by mass of cellulose nanofiber-derived carbon was supported. A (LiMn _0.7 Fe _0.3 PO ₄ , amount of carbon = 2.0 mass%, average particle size: 100 nm) was obtained.
Hereinafter, the lithium iron manganese phosphate A is referred to as LMP-A.

[Production Example 002: Production of lithium-based polyanion particles (LMP-B)]
The whole amount of slurry B001 obtained in Production Example 001 was purged with nitrogen to make the dissolved oxygen concentration of slurry B001 0.5 mg / L, and then 2108 g of CoSO ₄ .7H ₂ O was added to obtain slurry C002.
Next, the obtained slurry C002 was charged into an autoclave and subjected to a hydrothermal reaction at 170 ° C. for 1 hour. The pressure in the autoclave was 0.8 MPa. After the hydrothermal reaction, the produced crystal was filtered, and then washed with 12 parts by mass of water with respect to 1 part by mass of the crystal. The washed crystal was lyophilized at −50 ° C. for 12 hours to obtain a complex D002.
The obtained composite D002 was calcined at 700 ° C. for 1 hour in an argon hydrogen atmosphere (hydrogen concentration: 3%), and cobalt lithium phosphate B carrying carbon of 2.0 mass% derived from cellulose nanofibers ( LiCoPO ₄ / C, amount of carbon = 2.0% by mass).
Hereinafter, the lithium cobalt phosphate B is referred to as LMP-B.

[Production Example 003: Production of lithium-based polyanion particles (LMP-C)]
In the production of lithium-based polyanion particles in Production Example 001, 2.0 mass% of carbon derived from glucose was produced in the same manner as in Production Example 001 except that the addition of 5892 g of cellulose nanofibers to slurry A was changed to 125 g of glucose. A supported lithium manganese iron phosphate C (LiMn _0.7 Fe _0.3 PO ₄ , amount of carbon = 2.0 mass%, average particle size: 100 nm) was obtained.
Hereinafter, the lithium iron manganese phosphate C is referred to as LMP-C.

[Production Example 004: Production of lithium-based polyanion particles (LMP-D)]
In the production of lithium-based polyanion particles of Production Example 001, 0.1 mass% of carbon derived from cellulose nanofibers was produced in the same manner as Production Example 001, except that the amount of cellulose nanofiber added to slurry A001 was changed to 5892 g. Was obtained. Lithium manganese iron phosphate D (LiMn _0.7 Fe _0.3 PO ₄ , amount of carbon = 0.1 mass%, average particle size: 100 nm) was obtained.
Hereinafter, the lithium iron manganese phosphate B is referred to as LMP-D.

[Example 1: (Li-NCM-A 70% + LMP-A 30%) complex]
350 g of Li-NCM-A obtained in Production Example A and 150 g of LMP-A obtained in Production Example 001 were subjected to a composite treatment at 2000 rpm for 5 minutes using Nobilta (manufactured by Hosokawa Micron Corporation, NOB130). A positive electrode composite active material for a lithium ion secondary battery obtained by combining Li-NCM-A and LMP-A was obtained.

[Example 2: (Li-NCM-A 70% + LMP-B 30%) complex]
A positive electrode composite active material for a lithium ion secondary battery was obtained in the same manner as in Example 1, except that LMP-A was changed to LMP-B obtained in Production Example 002.

[Example 3: (Li-NCM-A 70% + LMP-A 30%) complex]
A positive electrode composite active material for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that the composite treatment was performed using an Eirich intensive mixer (EL1 manufactured by Japan Eirich Co., Ltd.) for 5 minutes at 4800 rpm.

[Example 4: (Li-NCM-A 70% + LMP-A 30%) complex]
A positive electrode composite active material for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that the composite treatment was performed using an Eirich intensive mixer (EL1 manufactured by Nihon Eirich Co., Ltd.) at 7200 rpm for 3 minutes.

[Example 5: (Li-NCM-A 90% + LMP-A 10%) complex]
Li-NCM-A was changed to 450 g, LMP-A was changed to 50 g, and the compounding treatment condition by Nobilta (manufactured by Hosokawa Micron Corporation, NOB130) was changed to 4000 rpm for 1 minute. A positive electrode composite active material for an ion secondary battery was obtained.

[Example 6: (Li-NCM-A 70% + LMP-C 30%) complex]
A positive electrode composite active material for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that LMP-A was changed to LMP-C obtained in Production Example 003.

[Example 7: (Li-NCM-A 70% + LMP-D 30%) complex]
A positive electrode composite active material for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that LMP-A was changed to LMP-D obtained in Production Example 004 and 5 g of graphite was further added.

[Comparative Example 1: (Li-NCM-A 70% + LMP-A 30%) mixture]
Li-NCM-A and LMP-A 350 g obtained in Production Example A and LMP-A 150 g obtained in Production Example 001 were mixed for 5 minutes using a mortar. Thus, a positive electrode mixture active material for a lithium ion secondary battery, which was simply mixed without being combined, was obtained.

[Comparative Example 2: (Li-NCM-A 70% + LMP-B 30%) mixture]
A positive electrode mixture active material for a lithium ion secondary battery was obtained in the same manner as in Comparative Example 1 except that LMP-A was changed to LMP-B obtained in Production Example 004.

[Comparative Example 3: (Li-NCM-A 50% + LMP-A 50%) mixture]
A positive electrode mixture active material for a lithium ion secondary battery was obtained in the same manner as in Comparative Example 1 except that Li-NCM-A was changed to 250 g and LMP-A was changed to 250 g.

[Comparative Example 4: (Li-NCM-A 90% + LMP-A 10%) mixture]
A positive electrode mixture active material for a lithium ion secondary battery was obtained in the same manner as in Comparative Example 1 except that Li-NCM-A was changed to 450 g and LMP-A was changed to 50 g.

[Comparative Example 5: (Li-NCM-A 90% + LMP-A 10%) complex]
Li-NCM-A was changed to 450 g, LMP-A was changed to 50 g, and the compounding treatment conditions by Nobilta (manufactured by Hosokawa Micron Corporation, NOB130) were changed to 2000 rpm for 1 minute. A positive electrode composite active material for an ion secondary battery was obtained.

≪Measurement of peak intensity ratio by X-ray photoelectron spectroscopy≫
X-ray photoelectron spectroscopy was measured for the active materials of all Examples and Comparative Example 5, and the peak intensity ratio a / b and the surface coverage (area%) were determined. Specifically, with a micron separator (MS manufactured by Hosokawa Micron Co., Ltd.), a Li-NCM composite oxide particle group obtained by removing lithium-based polyanion particles present alone without being complexed with a Li-NCM composite oxide was obtained. The peak intensity a of Ni2p _3/2 derived from Li-NCM-A in the obtained X-ray photoelectron spectroscopy spectrum (device used: JPS9010MX manufactured by JEOL Ltd.) is expressed as LMP-A, LMP-B, LMP-C or LMP-D. The peak intensity ratio a / b divided by the derived (P2p + C1s) peak intensity b was calculated. Further, from the obtained peak intensity ratio a / b, the surface coverage (area%) of the composite oxide secondary particles by the polyanion particles was obtained from the above formula (1).
The results are shown in Table 1.

≪Evaluation of change in viscosity of positive electrode slurry over time≫
A positive electrode slurry was prepared using the active materials of all the examples and comparative examples described above, and the viscosity of the positive electrode slurry was measured when 5 days passed immediately after the preparation. Specifically, the obtained active materials of Examples or Comparative Examples, ketjen black, and polyvinylidene fluoride were mixed at a mass ratio of 90: 5: 5, and N-methyl-2-pyrrolidone was added thereto. Were sufficiently kneaded to prepare a positive electrode slurry. After the preparation, the positive electrode slurry was immediately sealed in a sealed container, and the positive electrode slurry left to stand in a constant temperature environment of 20 ° C. for 5 days, using a B-type viscometer (Brookfield Digital Viscometer DV-E), The viscosity at a rotation speed of 100 rpm was determined. The viscosity immediately after preparation of all the positive electrode slurries was around 3500 (mPa · s).
The results are shown in Table 2.

<< Elution amount of transition metal to electrolyte >>
The positive electrode slurry immediately after preparation obtained by evaluating the change in viscosity of the positive electrode slurry with time is applied to a current collector made of an aluminum foil having a thickness of 20 μm using a coating machine, and vacuum dried at 80 ° C. for 12 hours. It was. Thereafter, it was punched into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode.
Next, a coin-type secondary battery was constructed using the positive electrode. A lithium foil (in the case of a lithium ion secondary battery) punched to φ15 mm was used for the negative electrode. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was used. As the separator, a known one such as a polymer porous film such as polypropylene was used. These battery components were assembled and accommodated in a conventional manner in an atmosphere having a dew point of −50 ° C. or lower to obtain a coin-type secondary battery (CR-2032).

The obtained secondary battery was charged. Specifically, constant current charging with a current of 170 mA / g and a voltage of 4.5 V was performed.
Thereafter, the secondary battery was disassembled, and the taken out positive electrode was washed with dimethyl carbonate and then immersed in an electrolytic solution. As the electrolytic solution at this time, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 1 was used. The electrolyte solution in which the positive electrode was immersed was placed in a sealed container and allowed to stand at 70 ° C. for 1 week.
After standing, the electrolyte solution from which the positive electrode was taken out was filtered through a 0.45 μm discic filter and acid-decomposed with nitric acid. Mn, Co, and Ni derived from the Li-NCM composite oxide contained in the acid-decomposed electrolytic solution were quantified using ICP emission spectroscopy (use apparatus: ULTIMA2 manufactured by Horiba, Ltd.).
The results are shown in Table 2.

≪Evaluation of discharge characteristics≫
Using the secondary battery produced by the evaluation of the amount of transition metal elution into the above electrolyte, 0.2C (34 mAh) at a temperature of 30 ° C. using a discharge capacity measuring device (HJ-1001SD8, manufactured by Hokuto Denko). / G) and 3C (510 mAh / g) initial discharge capacities were measured.
The results are shown in Table 2.

As is clear from Table 2, the positive electrode slurry using the active material obtained in the examples as the positive electrode active material is more viscous than the positive electrode slurry using the active material obtained in the comparative example as the positive electrode active material. It can be seen that the change is small and the workability is excellent.
Moreover, the lithium ion secondary battery using the active material obtained in the example as the positive electrode active material is a transition metal component compared to the lithium ion secondary battery using the active material obtained in the comparative example as the positive electrode active material. It can be seen that it has a good discharge capacity while effectively suppressing elution into the electrolyte solution and ensuring equivalent safety or higher.

Claims (16)

The following formula (I):
LiNi _a Co _b Mn _c M ¹ _x O ₂ (I)
(In the formula (I), ^{M 1} is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, 1 or 2 or more elements selected from Bi and Ge are shown, a, b, c, and x are 0.3 ≦ a <1, 0 <b ≦ 0.7, 0 <c ≦ 0.7, (0 ≦ x ≦ 0.3 and 3a + 3b + 3c + (valence of M ¹ ) × x = 3)
Or the following formula (II):
LiNi _d Co _e Al _f M ² _y O ₂ (II)
(In the formula (II), ^{M 2} is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and One or more elements selected from Ge are shown, d, e, f, and y are 0.4 ≦ d <1, 0 <e ≦ 0.6, 0 <f ≦ 0.3, 0 ≦. (Y ≦ 0.3 and 3d + 3e + 3f + (valence of M ² ) × y = 3)
In only a part of the surface of the layered lithium composite oxide secondary particles (A) composed of lithium composite oxide particles represented by the following formula (V):
LiCo _g M ⁵ _i PO ₄ (V)
(In the formula (V), M ⁵ represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. G and i are 0 <g ≦ 1 , 0 ≦ i ≦ 0.3, and 2g + (the valence of M ⁵ ) × i = 2.)
Or the following formula (VI):
LiFe _m Mn _n M ⁶ _o PO ₄ (VI)
(In the formula (VI), M ⁶ represents Co, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. M, n, and o are 0 ≦ m ≦ 1 represents a number satisfying 0 ≦ n ≦ 1, 0 ≦ o ≦ 0.3, and m + n ≠ 0, and satisfying 2m + 2n + (valence of M ⁶ ) × o = 2.)
Lithium-based polyanion particles (B) formed by supporting carbon (c) on the surface and lithium composite oxide particles are combined,
Lithium ion secondary whose peak intensity ratio ((Ni2p _3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) by X-ray photoelectron spectroscopy (XPS) is more than 0.05 and less than 0.4 Positive electrode active material for batteries.   2. The lithium according to claim 1, wherein the supported amount of carbon (c) on the surface of the lithium-based polyanion particle (B) is 0.1% by mass or more and less than 5% by mass in 100% by mass of the lithium-based polyanion particle (B). Positive electrode active material for ion secondary battery.   The mass ratio ((A) :( B)) between the content of the layered lithium composite oxide secondary particles (A) and the content of the lithium-based polyanion particles (B) is 95: 5 to 50:50. The positive electrode active material for lithium ion secondary batteries according to claim 1 or 2   The positive electrode active material for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the lithium-based polyanion particle (B) has an average particle size of 20 to 200 nm.   Carbon (c) carried on the surface of the lithium-based polyanion particle (B) is carbon (c1) derived from cellulose nanofibers or carbon (c2) derived from a water-soluble carbon material. 2. The positive electrode active material for lithium ion secondary batteries according to item 1. The water-insoluble carbon powder (c3) other than the carbon (c1) derived from cellulose nanofibers is compounded only with a part of the surface of the layered lithium composite oxide secondary particles (A) together with the lithium-based polyanion particles (B). And
Content of water-insoluble carbon powder (c3) is 100 parts by mass with respect to the total amount of lithium composite oxide secondary particles (A) and lithium-based polyanion particles (B) formed by supporting carbon (c) on the surface. It is 0.5-10 mass parts, The positive electrode active material for lithium ion secondary batteries of any one of Claims 1-5.   Step of mixing and laminating layered lithium composite oxide secondary particles (A) and lithium polyanion particles (B) having carbon (c) supported on the surface while applying compressive force and shear force The manufacturing method of the positive electrode active material body for lithium ion secondary batteries of any one of Claims 1-5 provided with these.   Water-insoluble carbon powder (c3) other than layered lithium composite oxide secondary particles (A), lithium-based polyanion particles (B) having carbon (c) supported on the surface, and carbon (c1) derived from cellulose nanofibers The method of producing a positive electrode active material body for a lithium ion secondary battery according to claim 6, further comprising a step of mixing and adding a compressive force and a shearing force. Formula (III) below
NaNi _{a ′} Co _{b ′} Mn _{c ′} M ³ _{x ′} O ₂ (III)
(In the formula (III), ^{M 3} is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, 1 or 2 or more elements selected from Bi and Ge, a ′, b ′, c ′ and x ′ are 0.3 ≦ a ′ <1, 0 <b ′ ≦ 0.7, 0 < (c ′ ≦ 0.7, 0 ≦ x ′ ≦ 0.3, and 3a ′ + 3b ′ + 3c ′ + (valence of M ³ ) × x ′ = 3).
Or the following formula (IV):
NaNi _{d ′} Co _{e ′} Al _{f ′} M ⁴ _{y ′} O ₂ (IV)
(In the formula (IV), M ⁴ is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and 1 or 2 or more elements selected from Ge, d ′, e ′, f ′, and y ′ are 0.4 ≦ d ′ <1, 0 <e ′ ≦ 0.6, and 0 <f ′. ≦ 0.3,0 ≦ y '≦ 0.3, and 3d' + 3e '+ 3f' + ( valence of ^{M 4)} shows a number satisfying × y '= 3.)
In only a part of the surface of the layered sodium composite oxide secondary particles (D) composed of the sodium composite oxide particles represented by the following formula (VII):
NaCo _{g ′} M ⁷ _{i ′} PO ₄ (VII)
(In the formula (VII), M ⁷ represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. G ′ and i ′ are 0 <g '≦ 1, 0 ≦ i' ≦ 0.3, and 2g ′ + (valence of M ⁷ ) × i ′ = 2).
Or the following formula (VIII):
NaFe _{m ′} Mn _{n ′} M ⁸ _{o ′} PO ₄ (VIII)
(In the formula (VIII), M ⁸ represents Co, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. M ′, n ′, and o ′ are 0. ≦ m ′ ≦ 1, 0 ≦ n ′ ≦ 1, 0 ≦ o ′ ≦ 0.3, and m ′ + n ′ ≠ 0, and 2m ′ + 2n ′ + (valence of M ⁸ ) × o ′ = 2 Indicates the number satisfying.)
The sodium-based polyanion particles (E) formed by supporting carbon (c) on the surface and sodium composite oxide particles are combined,
Sodium ion secondary whose peak intensity ratio ((Ni2p _3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) by X-ray photoelectron spectroscopy (XPS) is more than 0.05 and less than 0.4 Positive electrode active material for batteries.   10. The sodium according to claim 9, wherein the supported amount of carbon (c) on the surface of the sodium-based polyanion particle (E) is 0.1% by mass or more and less than 5% by mass in 100% by mass of the sodium-based polyanion particle (E). Positive electrode active material for ion secondary battery.   The mass ratio ((D) :( E)) between the content of the layered sodium composite oxide secondary particles (D) and the content of the sodium-based polyanion particles (E) is 95: 5 to 50:50. The positive electrode active material for sodium ion secondary batteries according to claim 9 or 10.   12. The positive electrode active material for a sodium ion secondary battery according to claim 9, wherein the average particle diameter of the sodium-based polyanion particles (E) is 50 to 200 nm.   The carbon (c) supported on the surface of the sodium-based polyanion particle (E) is carbon (c1) derived from cellulose nanofibers or carbon (c2) derived from a water-soluble carbon material. The positive electrode active material for sodium ion secondary batteries according to item 1. Water-insoluble carbon powder (c3) other than carbon (c1) derived from cellulose nanofibers is combined with sodium-based polyanion particles (E) only on part of the surface of the layered lithium composite oxide secondary particles (D). And
The content of the water-insoluble carbon powder (c3) is 100 parts by mass of the total amount of the sodium composite oxide secondary particles (D) and the sodium-based polyanion particles (E) formed by supporting carbon (c) on the surface. It is 0.5-24 mass parts, The positive electrode active material for sodium ion secondary batteries of any one of Claims 9-13.   A step of mixing and compounding layered sodium composite oxide secondary particles (D) and sodium-based polyanion particles (E) having carbon (c) supported on the surface while applying compressive force and shearing force. The manufacturing method of the positive electrode active material body for sodium ion secondary batteries of any one of Claims 9-13 provided with these.   Water-insoluble carbon powder (c3) other than layered sodium composite oxide secondary particles (D), sodium-based polyanion particles (E) having carbon (c) supported on the surface, and carbon (c1) derived from cellulose nanofibers The method for producing a positive electrode active material body for a sodium ion secondary battery according to claim 14, further comprising a step of mixing and adding a compression force and a shearing force to form a composite.