JP6590973B2 - Positive electrode active material composite for lithium ion secondary battery and method for producing the same - Google Patents

Description

  The present invention relates to a positive electrode active material composite for a lithium ion secondary battery capable of obtaining a lithium ion secondary battery having both excellent discharge characteristics and safety, and a method for producing the same.

  A secondary battery such as a lithium ion secondary battery is a kind of non-aqueous electrolyte battery, and is used in a wide range of fields such as mobile phones, digital cameras, notebook PCs, hybrid cars, and electric cars. Lithium ion secondary batteries mainly use lithium metal oxide as a positive electrode material and a carbon material such as graphite as a negative electrode material.

Examples of the positive electrode material include a layered rock salt structure Li—Ni—Co—Mn (NCM system) compound, a Li—Ni—Co—Al (NCA system) compound, a spinel structure Li (Mn, Ni) ₂ O ₄ , and olivine. Many things such as Li (Fe, Mn) PO ₄ having a mold structure are known. In particular, olivine-type lithium phosphate compounds are not greatly affected by resource constraints and can exhibit high safety, so that a lithium ion secondary battery with excellent battery properties can be obtained. Useful cathode material. Even if such a compound is miniaturized and used as a positive electrode active material, the performance of the resulting battery can be improved, but the tap density decreases, so the proportion of the positive electrode active material in the electrode mixture is also The volume energy density of the positive electrode may be reduced. For this reason, various developments have been made in the past in order to suppress a decrease in volume energy density in the electrode.

  For example, Patent Document 1 discloses a composite powder for electrodes in which electrode active materials are bonded to each other through a conductive material and have a specific bonding strength, or a composite for electrodes formed by binding by mechanofusion treatment. A powder is disclosed.

JP 2005-135723 A

  However, even with the lithium iron phosphate / acetylene black mixed powder obtained by the method of the above-mentioned patent document, it is still difficult to produce an electrode in which the decrease in volume energy density is sufficiently suppressed, and further improvement is required. It is in.

  Therefore, the subject of this invention is providing the positive electrode active material composite for lithium ion secondary batteries which can produce the positive electrode which has the outstanding volume energy density, and its manufacturing method.

  Accordingly, as a result of intensive studies to solve the above-mentioned problems, the present inventors have formed a composite of specific lithium-based polyanion particles (A) having carbon (c) supported on the surface under predetermined conditions. The positive electrode active material composite for lithium ion secondary batteries in which the specific layered rock salt structure type lithium composite oxide particles (B) are encapsulated inside the secondary particles is excellent in safety and has a volume energy density. It has been found that it is possible to fabricate a positive electrode having excellent resistance.

That is, the present invention provides the following formula (1):
Li _a Mn _b Fe _c M ¹ _d PO ₄ (1)
(In the formula (1), M ¹ represents Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. A, b, c, and d are 0.8 ≦ a ≦ 1.2, 0 ≦ b ≦ 1.2, 0 ≦ c ≦ 1.2, 0 ≦ d ≦ 0.3, and b + c ≠ 0, and a + 2b + 2c + (valence of M ¹ ) X indicates a number satisfying d = 3.)
Or the following formula (2):
^{_{Li e Co f Ni g M 2}} h PO 4 ··· (2)
(In Formula (2), M ² represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. E, f, g, and h are 0.8 ≦ e ≦ 1.2, 0 ≦ f ≦ 1.2, 0 ≦ g ≦ 1.2, 0 ≦ h ≦ 0.3, and f + g ≠ 0, and e + 2f + 2g + (valence of M ² ) X indicates a number satisfying h = 3.)
In the secondary particles formed by complexing the lithium-based polyanion particles (A) represented by and having carbon (c) supported on the surface,
Following formula (3):
^{_{LiNi i Co j Mn k M 3}} l O 2 ··· (3)
(In the formula (3), 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 are shown, i, j, k, and l are 0.3 ≦ i <1, 0 <j ≦ 0.7, 0 <k ≦ 0.7, (0 ≦ l ≦ 0.3 and 3i + 3j + 3k + (M ³ valence) × l = 3)
Or following formula (4):
^{_{LiNi m Co n Al o M 4}} p O 2 ··· (4)
(In the formula (4), 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, where m, n, o, and p are 0.4 ≦ m <1, 0 <n ≦ 0.6, 0 <o ≦ 0.3, 0 ≦ p ≦ 0.3 and 3m + 3n + 3o + (the valence of M ⁴ ) × p = 3)
1 or more types of layered rock salt structure type lithium composite oxide particles (B) represented by
The average particle size of the lithium-based polyanion particles (A) is 50 nm to 300 nm,
The average particle size of the layered rock salt structure type lithium composite oxide particles (B) is 500 nm to 20 μm,
The amount of carbon (c) supported on the surface of the lithium-based polyanion particle (A) is 0.1% by mass or more and less than 18% by mass in 100% by mass of the lithium-based polyanion particle (A),
The mass ratio ((A) :( B)) of the content of the lithium-based polyanion particles (A) and the content of the layered rock salt structure type lithium composite oxide particles (B) is 95: 5 to 70:30. A positive electrode active material composite for a certain lithium ion secondary battery is provided.

  According to the positive electrode active material composite for a lithium ion secondary battery of the present invention, the layered rock salt structure type lithium has a specific quantitative relationship and the like inside the secondary particles formed by the lithium-based polyanion particles. Since it exhibits a unique form in which complex oxide particles are encapsulated, it is possible to realize a positive electrode having an excellent volume energy density as an electrode while being a main constituent phase of an olivine type lithium phosphate compound. In a lithium ion secondary battery obtained by using as a positive electrode material, excellent safety and discharge characteristics can be exhibited.

2 is a Raman spectrum diagram of Example 1. FIG. The vertical axis represents intensity (au), and the horizontal axis represents Raman shift (cm ^-1 ). 6 is a Raman spectrum diagram of Comparative Example 3. FIG. The vertical axis represents intensity (au), and the horizontal axis represents Raman shift (cm ^-1 ).

Hereinafter, the present invention will be described in detail.
The positive electrode active material composite for a lithium ion secondary battery of the present invention has the following formula (1):
Li _a Mn _b Fe _c M ¹ _d PO ₄ (1)
(In the formula (1), M ¹ represents Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. A, b, c, and d are 0.8 ≦ a ≦ 1.2, 0 ≦ b ≦ 1.2, 0 ≦ c ≦ 1.2, 0 ≦ d ≦ 0.3, and b + c ≠ 0, and a + 2b + 2c + (valence of M ¹ ) X indicates a number satisfying d = 3).
Or the following formula (2):
^{_{Li e Co f Ni g M 2}} h PO 4 ··· (2)
(In Formula (2), M ² represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. E, f, g, and h are 0.8 ≦ e ≦ 1.2, 0 ≦ f ≦ 1.2, 0 ≦ g ≦ 1.2, 0 ≦ h ≦ 0.3, and f + g ≠ 0, and e + 2f + 2g + (valence of M ² ) X indicates a number satisfying h = 3.)
In the secondary particles formed by complexing the lithium-based polyanion particles (A) represented by and having carbon (c) supported on the surface,
Following formula (3):
^{_{LiNi i Co j Mn k M 3}} l O 2 ··· (3)
(In the formula (3), 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 are shown, i, j, k, and l are 0.3 ≦ i <1, 0 <j ≦ 0.7, 0 <k ≦ 0.7, (0 ≦ l ≦ 0.3 and 3i + 3j + 3k + (M ³ valence) × l = 3)
Or following formula (4):
^{_{LiNi m Co n Al o M 4}} p O 2 ··· (4)
(In the formula (4), 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, where m, n, o, and p are 0.4 ≦ m <1, 0 <n ≦ 0.6, 0 <o ≦ 0.3, 0 ≦ p ≦ 0.3 and 3m + 3n + 3o + (the valence of M ⁴ ) × p = 3)
One or more layered rock salt structure type lithium composite oxide particles (B) represented by:
The average particle size of the lithium-based polyanion particles (A) is 50 nm to 300 nm,
The average particle size of the layered rock salt structure type lithium composite oxide particles (B) is 500 nm to 20 μm,
The amount of carbon (c) supported on the surface of the lithium-based polyanion particle (A) is 0.1% by mass or more and less than 18% by mass in 100% by mass of the lithium-based polyanion particle (A),
The mass ratio ((A) :( B)) of the content of the lithium-based polyanion particles (A) and the content of the layered rock salt structure type lithium composite oxide particles (B) is 95: 5 to 70:30. is there.

  Thus, the positive electrode active material composite for a lithium ion secondary battery of the present invention has a specific quantitative relationship with the particles (A) inside the secondary particles formed by the lithium-based polyanion particles (A). It is a composite exhibiting a peculiar form formed by encapsulating layered rock salt structure type lithium composite oxide particles (B). The surface of layered rock salt structure type lithium composite oxide particles (B) is covered with lithium-based polyanion particles (A). The lithium-based polyanion particle (A) itself is a composite formed by forming secondary particles while being composited so as to be coated. Therefore, while effectively suppressing the elution of the metal element contained in the layered rock salt structure type lithium composite oxide particles (B), the olivine type lithium phosphate compound has an excellent volume energy density while being the main constituent phase. The positive electrode which has can be obtained.

M ¹ in the above formula (1) represents Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. In the above formula (1), a, b, c, and d are 0.8 ≦ a ≦ 1.2, 0 ≦ b ≦ 1.2, 0 ≦ c ≦ 1.2, and 0 ≦ d ≦ 0. .3 and b + c ≠ 0 and a number satisfying a + 2b + 2c + (valence of M ¹ ) × d = 3.
As the lithium-based polyanion particles (A) represented by the above formula (1), 0.5 ≦ b ≦ 1.2 is preferable from the viewpoint of the average discharge voltage of the positive electrode active material composite for lithium ion secondary batteries, 0.6 ≦ b ≦ 1.1 is more preferable, and 0.65 ≦ b ≦ 1.05 is even 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 Examples thereof include particles composed of Fe _0.4 PO ₄ , LiMn _0.5 Fe _0.5 PO ₄ , Li _1.2 Mn _0.63 Fe _0.27 PO ₄ , Li _0.8 Mn _0.79 Fe _0.31 PO _{4 and the} like. Of _{these, LiMn 0.8 Fe 0.2 PO 4,} Li 1.2 Mn 0.63 Fe 0.27 PO 4, or Li _0.8 Mn _0.79 Fe _0.31 consisting PO ₄ particles are preferred.

M ² in the above formula (2) represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. In the above formula (2), e, f, g, and h are 0.8 ≦ e ≦ 1.2, 0 ≦ f ≦ 1.2, 0 ≦ g ≦ 1.2, and 0 ≦ h ≦ 0. 3 and f + g ≠ 0, and a number satisfying e + 2f + 2g + (valence of M ² ) × h = 3.
As the lithium-based polyanion particles (A) represented by the above formula (2), in the same manner as the above formula (1), from the viewpoint of the average discharge voltage of the positive electrode active material composite for lithium ion secondary batteries, 0.5 ≦ f ≦ 1.2 is preferable, 0.6 ≦ f ≦ 1.1 is more preferable, and 0.65 ≦ f ≦ 1.05 is more preferable. Specifically, for example, LiCoPO ₄ , LiCo _0.25 Ni _0.25 PO ₄ , LiCo _0.2 Ni _0.2 Mn _0.1 PO ₄ , LiCo _0.2 Ni _0.2 Fe _0.1 PO ₄ , Li _1.2 Co _0.63 Ni _0.27 PO ₄ , Li _0.8 Co _0.79 Ni _0.31 PO ₄ particles and the like. Among them, LiCoPO _4, or particles consisting of LiCo _0.2 Ni _0.2 Mn _0.1 PO ₄ are preferred.

Further, two or more different lithium-based polyanion particles represented by the above formulas (1) and (2) have a core-shell structure lithium system having a core part (inside) and a shell part (surface layer part). Polyanion particles (A) may be formed.
By using the lithium-based polyanion particles (A) formed with this core-shell structure, a lithium-based polyanion having a high Mn content that is easily eluted from the lithium-based polyanion particles (A) into the electrolyte solution is disposed in the core portion. The shell part in contact with the electrolyte solution is arranged with a lithium polyanion having a low Mn content in the shell part, or a lithium type polyanion having a high Co content that is highly toxic to the human body and the environment. For example, a lithium-based polyanion having a low Co content may be disposed to further suppress the deterioration of the cycle characteristics due to the lithium-based polyanion particles and ensure safety. At this time, the core part may be a single phase or may be composed of two or more phases having different compositions. As an aspect in which the core part is composed of two or more phases, a structure in which a plurality of phases are concentrically stacked and laminated, or a structure in which the composition changes transitionally from the surface of the core part toward the center part may be used. Good.
Furthermore, the shell part should just be formed in the outer side of a core part, may be 1 phase like a core part, and may be comprised by 2 or more phases from which a composition differs.

As the lithium-based polyanion particles (A) formed with such a core-shell structure, specifically, (core part)-(shell part) is, for example, (LiMnPO ₄ )-(LiFePO ₄ ), (LiCoPO ₄ ). )-(LiNiPO ₄ ), (LiMnPO ₄ ) — (LiNiPO ₄ ), (LiCoPO ₄ ) — (LiFePO ₄ ), or (LiMn _0.5 Co _0.5 PO ₄ ) — (LiFePO ₄ ) Can be mentioned.

The average particle diameter of the lithium-based polyanion particles (A) represented by the above formula (1) or formula (2) forms secondary particles enclosing the layered rock salt structure type lithium composite oxide particles (B) inside. Therefore, it is an average particle size as so-called primary particles, and the particles are complexed well with the layered rock-salt structure type lithium composite oxide particles (B) described later while the particles are densely complexed to form secondary particles. However, from the viewpoint of satisfactorily enclosing this in the secondary particles, it is 50 nm to 300 nm, preferably 50 nm to 250 nm, and particularly preferably 50 nm to 200 nm.
Here, the average particle size means an average value of measured values of the particle size (length of major axis) of several tens of particles in observation using an SEM or TEM electron microscope.

The electric conductivity of the lithium-based polyanion particles (A) represented by the above formula (1) or formula (2) at a pressure of 20 MPa at 25 ° C. is preferably 1 × 10 ⁻⁷ S / cm or more. More preferably, it is 1 × 10 ⁻⁶ S / cm or more. The lower limit value of the electrical conductivity of the lithium-based polyanion particle (A) is not particularly limited.

  The lithium-based polyanion particle (A) has carbon (c) supported on its surface. The supported amount of carbon (c) is 0.1% by mass or more and less than 18% by mass in 100% by mass of the total amount of lithium-based polyanion particles (A) formed by supporting carbon (c), preferably 1 It is from mass% to 11 mass%, more preferably from 1 mass% to 8 mass%.

  In addition, as carbon (c) carry | supported by the surface of the lithium type polyanion particle (A) represented by the said Formula (1) or Formula (2), carbon (c1) derived from the cellulose nanofiber mentioned later or water-soluble Carbon (c2) derived from a functional carbon material is preferred. In this case, the supported amount of carbon (c) in the lithium-based polyanion particles (A) is the total supported amount of carbon (c1) derived from cellulose nanofibers and carbon (c2) derived from a water-soluble carbon material. It corresponds to the carbon atom equivalent amount of the cellulose nanofiber or water-soluble carbon material as the carbon source.

  The cellulose nanofibers to be the carbon source (c1) supported on the surface of the lithium-based polyanion particles (A) are skeletal components that occupy about 50% of all plant cell walls and constitute such cell walls. It is a lightweight high-strength fiber that can be obtained by defibrating plant fibers to nano size, and carbon derived from cellulose nanofibers 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 by carbon, it is carbonized and coupled with the polyanion particle, so that it is firmly supported on the surface of the lithium polyanion particle (A). By doing so, it is possible to obtain a useful positive electrode active material composite for a lithium ion secondary battery that imparts electronic conductivity to these polyanion particles and is excellent in cycle characteristics.

  The water-soluble carbon material as the carbon source (c2) supported on the surface of the lithium-based polyanion particle (A) is 0.4 g in terms of carbon atoms of the water-soluble carbon material in 100 g of water at 25 ° C. As mentioned above, it means a carbon material that dissolves preferably in an amount of 1.0 g or more. When carbonized, carbon is present on the surface of the lithium-based polyanion particle (A) as carbon. 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.

  The amount of carbon (c) supported on the surface of the lithium-based polyanion particles (A) (when carbon (c) is carbon (c1) derived from cellulose nanofibers or carbon (c2) derived from a water-soluble carbon material) These carbon atom equivalent amounts) can be confirmed as the carbon amount measured for the lithium-based polyanion particles (A) using a carbon / sulfur analyzer.

  The layered rock salt structure type lithium composite oxide particles (B) represented by the above formula (3) are so-called Li—Ni—Co—Mn oxide particles, and are hereinafter referred to as “NCM composite oxide particles”. The layered rock salt structure type lithium nickel composite oxide particles (B) represented by the above formula (4) are so-called Li—Ni—Co—Al oxide particles, and are hereinafter referred to as “NCA composite oxide particles”. Called.

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

In the NCM composite oxide particles represented by the above formula (3), it is known that Ni, Co and Mn are excellent in 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 ³ . By substituting with these metal elements M ^3, the crystal structure of the NCM composite oxide particles represented by the formula (3) is stabilized, so that the collapse of the crystal structure can be suppressed even after repeated charge and discharge, It is considered that excellent cycle characteristics can be realized.
Specific examples of the NCM composite oxide particles represented by the above formula (3) include 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 them, when importance is attached to the discharge capacity, particles having 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 , are preferable. Particles having a composition with 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, are preferable.

Further, two or more different NCM-based composite oxide particles represented by the above formula (3) are core-shell structure layered rock salt type lithium having a core part (inside) and a shell part (surface part). Composite oxide particles (B) may be formed.
By forming the layered rock salt structure type lithium composite oxide particles (B) formed with this core-shell structure, it is easy to elute into the electrolyte solution and easily release oxygen which adversely affects safety, or a solid electrolyte. NCM composite oxide particles having a high Ni concentration that easily react with a solid electrolyte in the core portion, and NCM composite oxide particles having a low Ni concentration can be placed in the shell portion in contact with the electrolyte solution. Suppression of deterioration of cycle characteristics and securing of safety can be further improved. At this time, the core part may be a single phase or may be composed of two or more phases having different compositions. As an aspect in which the core part is composed of two or more phases, a structure in which a plurality of phases are concentrically stacked and laminated, or a structure in which the composition changes transitionally from the surface of the core part toward the center part may be used. Good.
Furthermore, the shell part should just be formed in the outer side of a core part, may be 1 phase like a core part, and may be comprised by 2 or more phases from which a composition differs.

As the layered rock salt structure type lithium composite oxide particles (B) formed by forming a core-shell structure with two or more kinds of NCM composite oxide particles having different compositions, specifically, (core part)-( Shell part) is, for example, (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ )-(LiNi _0.2 Co _0.4 Mn _0.4 O ₂ ), (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ )-(LiNi _1/3 Co _1/3 Mn _{1 / 3} O ₂ ), or (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ )-(LiNi _0.33 Co _0.31 Mn _0.33 Mg _0.03 O ₂ ) or the like.

M ⁴ in the above formula (4) 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.
In the above formula (4), m, n, o and p are 0.4 ≦ m <1, 0 <n ≦ 0.6, 0 <o ≦ 0.3, 0 ≦ p ≦ 0.3, And 3m + 3n + 3o + (valence of M ² ) × p = 3.

The NCA-based composite oxide particles represented by the above formula (4) are more excellent in battery capacity and output characteristics than the NCM-based complex oxide particles represented by the formula (3). 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 NCA-based composite oxide particles represented by the above formula (4) 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 _0.03 Examples thereof include particles made of O ₂ , LiNi _0.8 Co _0.15 Al _0.03 Zn _0.03 O ₂ or the like. Among these, particles made of LiNi _0.8 Co _0.15 Al _0.03 Mg _0.03 O ₂ are preferable.

  The layered rock salt structure type lithium composite oxide particles (B) of the present invention are a mixture of NCM composite oxide particles represented by the above formula (3) and NCA composite oxide particles represented by the above formula (4). You may do it. The mixed state is a secondary particle in which the primary particles of the NCM composite oxide particles represented by the above formula (3) and the primary particles of the NCA composite oxide particles represented by the above formula (4) coexist. And a secondary particle composed only of the NCM-based composite oxide particles represented by the above formula (3) and a secondary particle composed only of the NCA-based composite oxide particles represented by the above formula (4). The primary particles of the NCM composite oxide particles represented by the above formula (3) and the primary particles of the NCA composite oxide particles represented by the above formula (4) may coexist. Secondary particles composed only of NCM-based composite oxide particles represented by the above formula (3) and secondary particles composed only of NCA-based composite oxide particles represented by the above formula (4). May be mixed. Furthermore, in the case of secondary particles consisting only of NCM composite oxide particles represented by the above formula (3), a core-shell structure is formed by two or more types of NCM composite oxide particles having different compositions. It may be.

  NCM composite oxide particles and NCA composite oxide particles when the NCM composite oxide particles represented by the above formula (3) and the NCA composite oxide particles represented by the above formula (4) coexist. The proportion (mass%) of the material may be appropriately adjusted according to the required battery characteristics. For example, when importance is attached to the rate characteristics, it is preferable to increase the proportion of the NCM composite oxide particles represented by the above formula (4). Specifically, the NCM composite oxide particles and the NCA system are used. The mass ratio of the composite oxide particles (NCM composite oxide particles: NCA composite oxide) is preferably 99.9: 0.1-60: 40. In addition, for example, when importance is attached to battery capacity, it is preferable to increase the proportion of the NCA-based composite oxide particles represented by the above formula (4). Specifically, for example, NCM-based composite oxide particles The mass ratio of NCA-based composite oxide particles (NCM-based composite oxide particles: NCA-based composite oxide) is preferably 40:60 to 0.1: 99.9.

  The surface of the NCM composite oxide particles represented by the above formula (3) and / or the NCA composite oxide particles (B) represented by the above formula (4) is covered with the lithium polyanion particles (A). In this way, secondary particles are formed while encapsulating the particles (B), so that elution of metal elements contained in the NCM-based composite oxide particles or NCA-based composite oxide particles can be suppressed. it can.

The average particle size as the primary particles of the layered rock salt structure type lithium composite oxide particles (B) represented by the above formula (3) or formula (4) is preferably 500 nm or less, more preferably 300 nm or less. . Thus, by making the average particle size as the primary particles of the layered rock salt structure type lithium composite oxide particles (B) at least 500 nm or less, the expansion and contraction amount of the primary particles accompanying the insertion and desorption of lithium ions can be reduced. It can be suppressed and particle cracking can be effectively prevented. The lower limit of the average particle diameter as the primary particles is not particularly limited, but is preferably 50 nm or more from the viewpoint of handling.
The average particle size of the layered rock salt structure type lithium composite oxide particles (B) formed by aggregation of the primary particles is preferably 500 nm to 20 μm, more preferably 500 nm to 18 μm, and particularly preferably 500 nm. ~ 15 μm. By setting the average particle size of the layered rock salt structure type lithium composite oxide particles (B) within the above range, a lithium ion secondary battery having excellent discharge capacity can be obtained.
In this specification, the layered rock salt structure type lithium composite oxide particles (B) include only primary particles formed of secondary particles, and include lithium-based polyanion particles (A) and carbon derived from cellulose nanofibers. It does not contain other components such as (c1) or carbon (c2) derived from a water-soluble carbon material.

When the NCM composite oxide particles represented by the above formula (3) form a core-shell structure in the layered rock salt structure type lithium composite oxide particles (B), the primary particles forming the core portion The average particle size of is preferably 50 nm to 500 nm, more preferably 50 nm to 300 nm. And the average particle diameter of the core part which aggregates and forms the said primary particle becomes like this. Preferably they are 100 nm-15 micrometers, More preferably, they are 400 nm-12.5 micrometers.
Further, the average particle size as the primary particles of the NCM composite oxide particles constituting the shell portion covering the surface of the core portion is preferably 50 nm to 500 nm, more preferably 50 nm to 300 nm. The layer thickness of the shell part formed by aggregation of the primary particles is preferably 100 nm to 5 μm, more preferably 100 nm to 2.5 μm.

  The internal porosity of the layered rock salt structure type lithium composite oxide particles (B) represented by the above formula (3) or formula (4) is the layered rock salt structure type lithium composite oxide particles (B) accompanying the insertion of lithium ions. From the viewpoint of allowing expansion of the primary particles in the internal voids of the secondary particles and improving the energy density of the positive electrode active material obtained, in 100% by volume of the layered rock salt structure type lithium composite oxide particles (B) 3 volume%-10 volume% are preferable, and 3 volume%-8 volume% are more preferable.

  In the positive electrode active material composite for a lithium ion secondary battery of the present invention, the content of the lithium-based polyanion particles (A) formed of secondary particles and carrying carbon (c) on the surface (carbon ( c)) and the content of the layered rock-salt structure type lithium composite oxide particles (B) is preferably 95: 5 to 70:30. Yes, more preferably 90:10 to 75:30.

In the positive electrode active material composite for a lithium ion secondary battery of the present invention, the layered rock salt structure type lithium composite oxide particles (B) are encapsulated in the secondary particles formed by complexing the lithium-based polyanion particles (A). It becomes. That is, on the surface of the positive electrode active material composite for a lithium ion secondary battery of the present invention, the layered rock salt structure type lithium composite oxide particles (B) are not present, and carbon (c) is supported on the surface. Only lithium-based polyanion particles (A) formed of secondary particles are present, and the layered rock-salt structure type lithium composite oxide particles (B) are not exposed on the surface of the positive electrode active material composite for lithium ion secondary batteries. It is completely contained.
Thus, the degree of inclusion of the layered rock salt structure type lithium composite oxide particles (B) can be evaluated by Raman spectroscopy. Specifically, it is a surface layer of the positive electrode active material composite for a lithium ion secondary battery of the present invention, and is a carbon layer (A) supported on the surface of lithium-based polyanion particles (A) formed with secondary particles ( c) is in the Raman spectrum obtained by Raman spectroscopy, D band (peak position: 1350 cm ^-1 vicinity) and G band (peak position: it can be confirmed as 1590cm around ^-1). On the other hand, the layered rock salt structure type lithium composite oxide particles (B) can be confirmed as a peak near 530 cm ⁻¹ in the Raman spectrum obtained by Raman spectroscopy. Therefore, as in the positive electrode active material composite for a lithium ion secondary battery of the present invention, the layered rock salt structure type lithium composite oxide particles (B) are secondary particles formed of lithium-based polyanion particles (A). If they are completely included therein, in the Raman spectrum of the positive active material composite for a lithium ion secondary battery, peak at 530 cm ^-1 ± 5 cm ^-1 is not observed, D band and G with carbon (c) A band is observed.

The method for producing a positive electrode active material composite for a lithium ion secondary battery of the present invention includes the following steps (I) to (II):
(I) Hydrothermal reaction product of lithium compound, metal compound containing at least iron compound or manganese compound, and phosphoric acid compound, or hydrothermal reaction product of lithium compound, metal compound containing at least cobalt compound or nickel compound, and phosphoric acid compound From the lithium-based polyanion particles (A) having a porosity of 45% to 80% by volume and carrying carbon (c) on the surface by spray drying using the reactant and the carbon source (C). A step of obtaining a granulated body (D) formed, and (II) the lithium-based polyanion particles (A) obtained in step (I), and the layered rock-salt structure type lithium composite oxide particles (B), A step of mixing and combining while applying a compressive force and a shearing force is provided.

In the method for producing a positive electrode active material composite for a lithium ion secondary battery of the present invention,
Prior to the step (II), a step (III) of separately producing the layered rock salt structure type lithium composite oxide particles (B) can be provided.

Step (I) includes a lithium compound, a metal compound containing at least an iron compound or a manganese compound, and a hydrothermal reaction product of a phosphate compound, or a lithium compound, a metal compound containing at least a cobalt compound or a nickel compound, and a phosphate compound. Lithium-based polyanion particles having a porosity of 45% by volume to 80% by volume and carrying carbon (c) on the surface by spray drying using the hydrothermal reaction product of and a carbon source (C) ( This is a step of obtaining a granulated body (D) formed from A).
That is, the hydrothermal reactant used in step (I) is a lithium compound, a metal compound containing at least an iron compound or a manganese compound, and a phosphoric acid compound subjected to a hydrothermal reaction, or a lithium compound, at least a cobalt compound or a nickel compound. Primary particles of lithium-based polyanion particles (A) obtained by hydrothermal reaction of a metal compound containing phosphine and a phosphoric acid compound. In the step (I), the slurry containing the primary particles and the carbon source (C) is spray dried and granulated, and then calcined to adjust the porosity to 45 vol% to 80 vol%, A granulated body (D) comprising lithium-based polyanion particles (A) having carbon (c) supported on the surface is obtained.
More specifically, step (I) includes the following (i) to (iv):
(I) a step of obtaining a composite (I-2) by mixing a phosphate compound with a mixture (I-1) containing a lithium compound;
(Ii) After obtaining the slurry (I-3) containing the obtained composite (I-2) and a metal compound containing at least an iron compound or a manganese compound, or a metal compound containing at least a cobalt compound or a nickel compound A slurry (I-3 ′) containing, and then subjecting the slurry (I-3) or the slurry (I-3 ′) to a hydrothermal reaction to obtain a composite (I-4),
(Iii) After preparing the obtained composite (I-4) and the slurry (I-5) containing the carbon source (C), the slurry (I-5) is spray-dried to obtain lithium-based polyanion particles ( A step of obtaining a pre-granulated product (I-6) comprising A) and a carbon source (C);
(Iv) The obtained pre-granulated product (I-6) is fired in a reducing atmosphere or an inert atmosphere, and formed from lithium-based polyanion particles (A) having carbon (c) supported on the surface. The process of obtaining the granulated body (D) which becomes.

The said process (i) is a process of mixing a phosphoric acid compound with the mixture (I-1) containing a lithium compound, and obtaining a composite_body | complex (I-2).
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 (I-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.

  It is preferable to stir the mixture (I-1) in advance before mixing the phosphoric acid compound with the mixture (I-1). The stirring time of the mixture (I-1) is preferably 1 minute to 15 minutes, more preferably 3 minutes to 10 minutes. Moreover, the temperature of mixture (I-1) becomes like this. Preferably it is 20 to 90 degreeC, More preferably, it is 20 to 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% by mass to 90% by mass. When phosphoric acid is used as the phosphoric acid compound, it is preferable to add phosphoric acid dropwise while stirring the mixture (I-1). By adding phosphoric acid dropwise to the mixture (I-1) little by little, the reaction proceeds well in the mixture (I-1), and the composite (I-2) is uniformly dispersed in the slurry. It is possible to effectively prevent the complex (I-2) from being aggregated unnecessarily.

The dropping rate of phosphoric acid into the mixture (I-1) is preferably 15 mL / min to 50 mL / min, more preferably 20 mL / min, with respect to 100 mol of the lithium compound contained in the mixture (I-1). Min to 45 mL / min, more preferably 28 mL / min to 40 mL / min. Moreover, the stirring time of the mixture (I-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 (I-1) while dropping phosphoric acid is preferably 200 rpm to 700 rpm, more preferably 250 rpm to 600 rpm, and further preferably 300 rpm to 500 rpm.
In addition, when stirring mixture (I-1), it is preferable to cool below the boiling point temperature of mixture (I-1). Specifically, cooling to 80 ° C. or lower is preferable, and cooling to 20 ° C. to 60 ° C. is more preferable.

  The mixture (I-1) after mixing the phosphoric acid compound preferably contains 2.7 mol to 3.3 mol of lithium with respect to 1 mol of phosphoric acid, and contains 2.8 mol to 3.1 mol. More preferably.

Further, by purging the mixture (I-1) after mixing the phosphoric acid compound with nitrogen, the reaction in the mixture is completed, and the complex (I -2) can be produced in the mixture. When nitrogen is purged, the reaction can proceed in a state where the dissolved oxygen concentration in the mixture (I-1) is reduced, and the dissolved oxygen in the mixture containing the resulting complex (I-2). Since the concentration is also effectively reduced, oxidation of the iron compound, manganese compound, etc. added in the next step (ii) can be effectively suppressed. In the mixture containing the composite (I-2), the precursor of the lithium-based polyanion particles exists as fine dispersed particles. Such a complex (I-2) is obtained as trilithium phosphate (Li ₃ PO ₄ ).

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

  Further, from the viewpoint of more effectively suppressing the oxidation on the surface of the dispersed particles of the composite (I-2) and miniaturizing the dispersed particles, the dissolved in the mixture (I-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.

  The step (ii) is obtained after obtaining the slurry (I-3) containing the composite (I-2) obtained in the step (i) and a metal compound containing at least an iron compound or a manganese compound, or at least After obtaining a slurry (I-3 ′) containing a metal compound containing a cobalt compound or a nickel compound, the slurry (I-3) or the slurry (I-3 ′) is subjected to a hydrothermal reaction to form a composite (I -4). Whether the composite (I-2) obtained by the above step (i) is used as a mixture as a precursor of the lithium-based polyanion particles (A), and a metal compound containing at least an iron compound or a manganese compound is added thereto. Or at least a cobalt compound or a nickel compound is preferably used as the slurry (I-3) or the slurry (I-3 ′). Thereby, the target lithium polyanion particle (A) for forming the granulated body (D) can be obtained as extremely fine particles while simplifying the process.

  Examples of iron compounds, manganese compounds, cobalt compounds, and nickel compounds that can be used include sulfates, nitrates, carbonates, acetates, oxalates, oxides, hydroxides, halides, and the like of these metal elements. It is done. Specific examples include iron sulfate, manganese sulfate, cobalt sulfate, nickel sulfate, iron acetate, manganese acetate, cobalt acetate, and nickel acetate. These may be used alone or in combination of two or more. May be. Especially, a sulfate is preferable from a viewpoint of improving the battery characteristic of lithium type polyanion particle | grains (A).

Furthermore, as necessary, a metal (M ¹ or M ² ) compound may be used as the metal compound. As the metal (M ¹ or M ² ) compound, sulfates, halogen compounds, organic acid salts, and hydrates thereof can be used. These may be used alone or in combination of two or more. Among these, it is more preferable to use a sulfate from the viewpoint of improving battery characteristics.
When these metal (M ³ ) compounds are used, the total addition amount of (iron compound, manganese compound, and metal (M ¹ ) compound) or the total addition of (cobalt compound, nickel compound, and metal (M ² ) compound) The amount is preferably from 0.99 mol to 1.01 mol, more preferably from 0.995 mol to 1 mol of phosphoric acid in the complex (I-2) obtained in the step (i). 1.005 mol.

  The amount of water used for the hydrothermal reaction is the slurry (I-3) or slurry (I-3 ′) from the viewpoint of the solubility of the metal compound used, the ease of stirring, the efficiency of synthesis, and the like. Preferably it is 10 mol-30 mol with respect to 1 mol of phosphate ions contained in it, More preferably, it is 12.5 mol-25 mol.

In the step (ii), the order of addition of the iron compound, manganese compound and metal (M ¹ ) compound, or the order of addition of the cobalt compound, nickel compound and metal (M ² ) compound is not particularly limited. Further, the addition of these metals (M ¹ or M ²⁾ compound may be added an 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 an iron compound, a manganese compound, and a metal used as necessary (M ¹ ) from the viewpoint of preventing the formation of the lithium-based polyanion particles (A) by being excessively added. ) Compound, or a total of 1 mol of the cobalt compound, nickel compound and metal (M ² ) compound used as necessary, it is preferably 0.01 mol to 1 mol, more preferably 0.03 mol to 0.00 mol. 5 moles.

  The content of the composite (I-4) in the slurry (I-3) or the slurry (I-3 ′) is preferably 10% by mass to 50% by mass, more preferably 15% by mass to 45% by mass. More preferably, it is 20 mass%-40 mass%.

The hydrothermal reaction in process (ii) should just be 100 degreeC or more, and 130 to 180 degreeC is preferable. The hydrothermal reaction is preferably performed in a pressure vessel. When the reaction is performed at 130 ° C to 180 ° C, the pressure at this time is preferably 0.3 MPa to 0.9 MPa, and the reaction is performed at 140 ° C to 160 ° C. The pressure in carrying out is preferably 0.3 MPa to 0.6 MPa. The hydrothermal reaction time is preferably 0.1 to 48 hours, more preferably 0.2 to 24 hours.
The obtained complex (I-4) can be recovered as a cake having a water content of 10% by mass to 50% by mass by filtering, washing with water, and filtering again. The filtration means may be vacuum filtration, pressure filtration, centrifugal filtration or the like, but pressure filtration such as a filter press is preferred from the viewpoint of simplicity of operation.

  The amount of washing water used for washing is 10 parts by mass or more, preferably 12 parts by mass or more with respect to 1 part by mass of the complex (I-4) in the filtration residue.

BET specific surface area of the composite obtained by drying the cake (I-4), from the viewpoint of effectively reducing the amount of adsorbed water is preferably ^{5m 2} / ^g~40m 2 / g, more preferably is 5m ² / g~30m ² / g. If the BET specific surface area of the composite (I-4) is less than 5 m ² / g, the lithium-based polyanion particles (A) may be enlarged. 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.

The average particle size of the composite (I-4) is such that the obtained lithium-based polyanion particles (A) are combined with the layered rock salt structure type lithium composite oxide particles (B), and the surface of the particles (B) is Lithium ion secondary battery that is excellent in durability and the like, in which particles (A) themselves are complexed with each other to form secondary particles while encapsulating well, and particles (B) are encapsulated well inside the secondary particles. From the viewpoint of obtaining a positive electrode active material composite for use, the thickness is preferably 50 nm to 300 nm, more preferably 50 nm to 250 nm, and particularly preferably 50 nm to 200 nm.
Here, the average particle diameter of the composite (I-4) means an average value of values obtained by the same measurement as the average particle diameter of the particles.

  In the step (iii), the composite (I-4) obtained in the step (ii) and the slurry (I-5) containing the carbon source (C) are prepared, and then the slurry (I-5) is sprayed. This is a step of drying to obtain a pre-granulated product (I-6) comprising lithium-based polyanion particles (A) and a carbon source (C).

  The carbon source (C) constituting the preliminary granulated body (I-6) is a raw material that becomes carbon (c) supported on the surfaces of the lithium-based polyanion particles (A) as carbon derived from the carbon source (C). is there. As this carbon source (C), the said cellulose nanofiber (d1) or the said water-soluble carbon material (d2) is mentioned.

  The content of the composite (I-4) in the slurry (I-5) is preferably 10 to 30 parts by mass, more preferably 15 to 30 parts by mass with respect to 100 parts by mass of water. is there. What is necessary is just to use the cake containing said composite_body | complex (I-4) so that it may become this content.

  When carbon (c) derived from the cellulose nanofiber (d1) is supported on the surface of the lithium-based polyanion particle (A) by a subsequent process, the cellulose nanofiber (d1) in the slurry (I-5) is supported. The content is 0.3 mass% to 6 mass% with respect to 100 mass% of the total amount of carbon (c) supported on the surface of the lithium-based polyanion particles (A) and the particles. It is desirable that the amount be such that Specifically, for example, it is preferably 0.1 part by mass to 20 parts by mass, and more preferably 1 part by mass to 10 parts by mass with respect to 100 parts by mass of water in the slurry (I-5).

  When the carbon (c) derived from the water-soluble carbon material (d2) is supported on the surface of the lithium-based polyanion particles (A) by a subsequent process, the water-soluble carbon material (d2) in the slurry (I-5) ) In terms of carbon atoms is 0.3 mass% to 6 mass with respect to 100 mass% of the total amount of carbon (c) supported on the lithium-based polyanion particles (A) and the particle surfaces. It is desirable that the amount be%. Specifically, for example, with respect to 100 parts by mass of water in the slurry (I-5), it is preferably 0.1 parts by mass to 18 parts by mass, and more preferably 1 part by mass to 10 parts by mass.

  The slurry (I-5) comprises lithium-based polyanion particles (A) and a carbon source (C), that is, lithium-based polyanion particles (A) and cellulose nanofibers (d1), or lithium-based polyanion particles (A) and water. From the viewpoint of uniformly dispersing the carbonaceous material (d2), it is preferable to perform a treatment using a disperser (homogenizer). Examples of such a disperser include a disaggregator, a beater, a low pressure homogenizer, a high pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short shaft extruder, a twin screw extruder, an ultrasonic stirrer, a household juicer mixer, and the like. Can be mentioned. Among these, an ultrasonic stirrer is preferable from the viewpoint of dispersion efficiency. The degree of dispersion uniformity of the slurry (I-5) can be quantitatively evaluated by, for example, light transmittance using a UV / visible light spectrometer or viscosity using an E-type viscometer. By simply confirming that the white turbidity is uniform, it is possible to simply evaluate. The processing time with the disperser is preferably 1 minute to 30 minutes, more preferably 2 minutes to 15 minutes. Since the slurry (I-5) thus treated can maintain a good mixed state for several days, it can be prepared and stored in advance.

  When cellulose nanofibers (d1) are used as the carbon source (C), the slurry (I-5) is preferably further subjected to wet classification from the viewpoint of effectively removing cellulose nanofibers that are still in an aggregated state. A sieve or a commercially available wet classifier can be used for wet classification. The opening of the sieve may vary depending on the fiber length of the cellulose nanofiber to be used, but is preferably about 150 μm from the viewpoint of work efficiency.

  Therefore, the solid content concentration of the slurry (I-5) used for the next step (iii) is preferably 9% by mass to 35% by mass, and more preferably 13% by mass to 30% by mass.

  Next, in the said process (iii), the obtained slurry (I-5) is spray-dried and a preliminary granulated body (I-6) is obtained. Such a pre-granulated product (I-6) includes a granulated product (D) formed by lithium-based polyanion particles (A) formed by supporting carbon (c) on the surface through a later step. Become. As a result, it is possible to avoid the formation of solid secondary particles formed by firmly agglomerating primary particles of the lithium-based polyanion (A), and to easily disintegrate without excessive load. Lithium layered rock salt structure type lithium composite oxide particles (A) comprising the granule (D) and lithium-based polyanion particles (A) comprising the granule (D) with carbon supported on the surface are used. It is possible to encapsulate the particles (B) inside the secondary particles formed by the particles (A) while satisfactorily covering the surface of B).

  The hot air temperature during spray drying is preferably 110 ° C to 160 ° C, and more preferably 120 ° C to 140 ° C. The ratio G / S of the supply amount G (L / min) of the hot air and the supply amount S (L / min) of the slurry (I-5) is preferably 500 ≦ G / S ≦ 10000, and 1000 ≦ G / S. ≦ 9000 is more preferable.

The particle size of the pre-granulated product (I-6) obtained in step (iii) is a D ₅₀ value in the particle size distribution based on the laser diffraction / scattering method, preferably 5 μm to 14 μm, more preferably 5 μm to 12 μm. It is.
Here, the D ₅₀ value in the particle size distribution measurement is a value obtained by a volume-based particle size distribution based on the laser diffraction / scattering method, and the D ₅₀ value means a particle size (median diameter) at a cumulative 50%. .

  In the step (iv), the pre-granulated product (I-6) obtained in the step (iii) is fired in a reducing atmosphere or an inert atmosphere, and a lithium-based material having carbon (c) supported on the surface. This is a step of obtaining a granulated body (D) composed of polyanion particles (A). By passing through the step (iv), the granule having an appropriate disintegration property while carbon (c) is more firmly supported on the surface of the lithium polyanion particle (A) constituting the granule (D). (D) can be formed.

  The firing temperature is preferably 600 ° C to 800 ° C, more preferably 700 ° C to 800 ° C from the viewpoint of effectively carbonizing the carbon source (C) and imparting appropriate disintegration to the granulated body (D). 800 ° C. The firing time is preferably 30 minutes to 3 hours, more preferably 1 hour to 2 hours.

  The porosity of the granulated body (D) composed of lithium-based polyanion particles (A) having carbon (c) supported on the surface is a porosity based on a mercury intrusion method, and is 45 vol% to 80 vol%. It is preferably 50% by volume to 80% by volume.

Further, the tap density of the granulated body (D) comprising the lithium-based polyanion particles (A) having carbon (c) supported on the surface is preferably less than 1.1 g / cm ³ , more preferably 0.00. it is a ^{6g / cm 3 ~1.0g / cm 3} .

Further, the average particle diameter of the granulated body (D) comprising the lithium-based polyanion particles (A) having carbon (c) supported on the surface is preferably a D ₅₀ value in the particle size distribution based on the laser diffraction / scattering method. Is 5 μm to 15 μm, more preferably 5 μm to 12 μm.

The collapse strength of the granulated body (D) composed of lithium-based polyanion particles (A) having carbon (c) supported on the surface is preferably 1.8 KN / mm or less, more preferably 1.75 KN / mm. It is as follows. Such disintegration strength indicates the ease of disintegration due to compression of the granule (D) composed of lithium-based polyanion particles (A) having carbon (c) supported on the surface. Means the desired value.
Collapse strength (KN / mm) of granulated body (D) = 10 / (t ₀ -t ₁₀ ) (X)
T ₀ in the formula (X) is 3 g of a granulated body (D) made of lithium-based polyanion particles (A) having carbon supported on a surface of a cylindrical container having a diameter of 20 mm, and dropped from a height of 1 cm. It shows the layer thickness (mm) of the granules (D) in the packed state after repeated 10 times tapping by, t ₁₀ is the granulation of such densely packed state (D), a load of 10KN from above The layer thickness (mm) of the granulated body (D) is shown.

  In addition, the amount in terms of atoms of carbon derived from cellulose nanofiber (d1) or carbon derived from water-soluble carbon material (d2) existing as carbon (c) on the surface of lithium-based polyanion particles (A) (carbon loading) Can be confirmed as the amount of carbon measured for the lithium-based polyanion particles (A) using a carbon / sulfur analyzer.

  In the subsequent step (II), the granulated body (D) obtained in the step (I) and the layered rock salt structure type lithium composite oxide particles (B) are mixed while applying compressive force and shearing force. It is a process of compounding. Through this process, the lithium-based polyanion particles (A) and the layered rock-salt structure-type lithium composite oxide particles (B) are combined, and the lithium-based polyanion particles (A) are also combined with each other to form particles (B). Secondary particles encapsulating can be formed.

  Before mixing while applying compressive force and shearing force, the granule (D) composed of lithium-based polyanion particles (A) having carbon (c) supported on the surface may be separately prepared in advance. It is preferable to thoroughly dry mix the mixture with the good layered rock salt structure type lithium composite oxide particles (B). 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.

  The process of mixing and compounding while applying compressive force and shearing force is preferably performed in an airtight container equipped with an impeller, a rotor tool, and the like. Examples of the apparatus equipped with such a closed container include a high-speed shear mill, a blade-type kneader, a high-speed mixer, and the like. Coke Kogyo Co., Ltd.) Microparticle composite device Mechanofusion, Nobilta (Hosokawa Micron Corp.), Surface Modification Device Miraro, Hybridization System (Nara Machinery Co., Ltd.), Eirich Intensive Mixer (Eirich Japan Co., Ltd.) are preferably used. be able to. As conditions for the above-mentioned compounding treatment, the temperature is preferably 5 ° C to 80 ° C, more preferably 10 ° C to 50 ° C. The atmosphere is not particularly limited, but is preferably an inert gas atmosphere or a reducing gas atmosphere.

More specifically, for example, when Novirta (made by Hosokawa Micron), which is a dry particle composite device equipped with an impeller, is used as the composite device, the rotational speed of the impeller is determined by the layered rock salt structure type lithium composite oxidation. From the viewpoint of obtaining a composite oxide in which the lithium-based polyanion particles (A) having carbon supported on the surface of the product particles (B) are satisfactorily coated, the number is preferably 2000 rpm to 6000 rpm, and more preferably 2000 rpm to 4000 rpm. Further, the complexing time is preferably 0.5 minutes to 30 minutes, more preferably 0.5 minutes to 15 minutes.
Further, when an Eirich intensive mixer (manufactured by Nihon Eirich Co., Ltd.), which is a high-speed stirring mixer equipped with a rotor tool, is used as an apparatus for performing such compounding, the rotational speed of the rotor tool is preferably 2000 rpm to 6000 rpm. More preferably, it is 2000 rpm to 5000 rpm. Further, the complexing time is preferably 0.5 minutes to 30 minutes, more preferably 0.5 minutes to 20 minutes.

In the step (II), the complexing time and / or the rotational speed of the impeller, etc. are determined based on the lithium-based polyanion particles (A) in which carbon is supported on the surface to be charged into the sealed container and the layered rock salt structure type lithium composite oxide particles. It is necessary to adjust suitably according to the quantity of the mixture of (B). Then, by operating the sealed container, it becomes possible to perform a process of combining these while adding compressive force and shearing force to the mixture between the impeller and the inner wall of the sealed container, and the layered rock salt structure described above -Type lithium composite oxide particles (B), and a positive electrode active material composite for a lithium ion secondary battery in which the above-described lithium-based polyanion particles (A) on which carbon is supported are well composited and coated Can be obtained.
For example, when the compounding process is performed in a sealed container equipped with an impeller rotating at a rotational speed of 2000 rpm to 5000 rpm for 0.5 to 6 minutes, the amount of the mixture put into the sealed container is the effective container (impeller Among the sealed containers provided, the container corresponding to a part capable of accommodating the above mixture) is preferably 0.1 g to 0.7 g, more preferably 0.15 g to 0.4 g per 1 cm ³ .

  The mass ratio (particle (A): particle (B)) of the lithium-based polyanion particles (A) to be compounded in the step (II) and the layered rock salt type lithium composite oxide particles (B) is a layered rock salt type lithium. From the viewpoint of encapsulating the lithium oxide polyanion particles (A) on the surface of the composite oxide particles (B) and encapsulating the particles (B) in the secondary particles of the particles (A), preferably 96: 4. It is -70: 30, More preferably, it is 96: 4-75:25, More preferably, it is 96: 4-80:20.

In addition, on the surface of the layered rock salt structure type lithium composite oxide particles (B), the extent to which the lithium-based polyanion particles (A) on which carbon is supported is combined and coated on the surface is 530 cm of Raman spectroscopy. It can be evaluated by the presence or absence of a peak near ^-1 . Specifically, when the layered rock salt structure type lithium composite oxide particles (B) are present on the surface of the positive electrode active material composite for a lithium ion secondary battery of the present invention, 530 cm ⁻¹ ± 5 cm of Raman spectroscopy. ^-1 peak is observed, and on the other hand, when the layered rock salt structure type lithium composite oxide particles (B) are completely encapsulated in the positive electrode active material composite for lithium ion secondary battery, Raman spectroscopy of 530 cm ^No peak is observed at ^-1 ± 5 cm ^-1 .

  Next, in the method for producing a positive electrode active material composite for a lithium ion secondary battery of the present invention, the layered rock salt structure type lithium composite oxide particles (B) that may be carried out prior to the step (II) ) Will be described.

In order to obtain the NCM composite oxide particles represented by the formula (3), a raw material compound, for example, a nickel compound, a cobalt compound, and a manganese compound, is mixed with water so as to have a desired composition of the NCM composite oxide particles. To obtain an aqueous solution A. 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, if necessary, a metal element (M ³⁾ that substitutes a part of the layered NCM composite oxide particles constituting the active material so as to have a desired composition of the NCM composite oxide particles. 1) selected from Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Ge You may mix a seed or 2 or more types of elements.

  Next, an alkaline agent 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 agent acts as a pH adjuster for maintaining the pH of the aqueous solution B at 10 to 14, and is dripped in an amount sufficient to bring about the effect. As the alkali agent, 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 ° C. to 60 ° C. Further, the stirring time of the aqueous solution B is preferably 30 minutes to 120 minutes, and more preferably 30 minutes to 60 minutes.

  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 metal composite hydroxide and the lithium compound are dry-mixed so as to have the desired composition of the NCM composite oxide particles, and calcined in an oxygen atmosphere to obtain NCM composite oxide particles. it can. 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 above mixture by pre-baking and then performing main baking, NCM composite oxide particles 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 degreeC / min-20 degreeC / 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 hours to 20 hours, and more preferably 4 hours to 6 hours.

The conditions for the next main baking are not particularly limited, but the temporary baking after calcination and then crushed with a mortar or the like is performed again from room temperature to a heating rate of 1 ° C./min to 20 ° C. / Min. 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 hours to 20 hours, more preferably 8 hours 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 particles 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 particles to 500 nm or less, the firing temperature is preferably 700 ° C. to 1000 ° C., more preferably 750 ° C. to 900 ° C.

  Furthermore, the internal porosity of the layered rock salt structure type lithium composite oxide particles (B) can be controlled by adjusting the firing time of the main firing. In order to set the internal porosity of the layered rock salt structure type lithium composite oxide particles (B) composed of primary particles of the NCM-based composite oxide particles to 3 volume% to 10 volume%, the firing time is preferably 6 hours to 12 hours. Time, more preferably 8 hours to 10 hours.

  Finally, the fired product obtained is washed with water, filtered and dried to obtain layered rock salt structure type lithium composite oxide particles (B) represented by the formula (3). Here, the drying is performed in two stages, and the moisture in the layered rock salt structure type lithium composite oxide particles (B) (water content measured at a vaporization temperature of 300 ° C.) is 1% by mass or less. It is preferable to dry at 90 ° C. or lower until it is, and then perform the second stage drying at 120 ° C. or higher. The moisture content may be measured using, for example, a Karl Fischer moisture meter.

  In the case of producing NCM composite oxide particles having a core-shell structure, secondary particles composed of the NCM composite oxide particles obtained by the main firing in the above step (III) are used as the core portion, and the core portion is configured. Step (III) may be repeated so that NCM composite oxide particles having different compositions are formed on the surface of the NCM composite oxide particles. The process for generating the shell portion is referred to as process (III ').

  In step (III ′), in order to obtain NCM-based composite oxide particles serving as a shell part, the composition of the desired NCM-based composite oxide particles is handled in the same manner as in the method for producing aqueous solution A in step (III). After obtaining the aqueous solution a to be obtained, the aqueous solution b containing the metal composite hydroxide is obtained in the same manner as in the method for producing the aqueous solution B in the step (III).

  Next, the aqueous solution b is mixed and stirred with the secondary particles of the NCM-based composite oxide particles constituting the core part obtained by the main calcination in the step (III), and from room temperature to 1 ° C./min to 20 ° C. / The mixture is heated to 100 ° C. to 110 ° C. at a temperature rising rate of minutes, and stirred in the air or in an oxygen atmosphere while heating in such a heating temperature range to evaporate water by 90% or more. Thereby, the raw material of the NCM type complex oxide particles constituting the shell part can be co-precipitated on the surface of the secondary particles of the NCM type complex oxide particles constituting the core part. In addition, the thickness of a shell part is controllable by adjusting heating temperature.

  The particles obtained through the above steps are subjected to two-stage firing and two-stage drying in the same manner as in the step (III), then washed with water, then filtered, and dried to form a layered structure having a core-shell structure. Rock salt structure type lithium composite oxide particles (B) are obtained.

Next, the case where the layered rock salt structure type lithium composite oxide particle (B) represented by the formula (4) is obtained in the step (III) will be specifically described.
In order to obtain the NCA-based composite oxide particles represented by the formula (4), raw material compounds such as a nickel compound, a cobalt compound, and an aluminum compound are mixed with water so as to have a desired composition of the NCA-based composite oxide particles. To obtain an aqueous solution A ′. 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, if necessary, a metal element (M ⁴⁾ for substituting a part of the layered NCA-based composite oxide particles constituting the active material so as to have a desired composition of the NCA-based composite oxide particles. ), Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Ge Two or more elements may be mixed.

  Next, an alkaline agent 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 agent is dropped in an amount sufficient to maintain the pH of the aqueous solution B ′ at 10-14. As the alkaline agent, 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 minutes to 120 minutes, and more preferably 30 minutes to 60 minutes.

  In order to obtain NCA-based composite oxide particles 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 ° C to 900 ° C.

  Next, the NCA composite oxide particles can be obtained by dry-mixing the metal composite hydroxide and the lithium compound so as to have the desired composition of the NCA composite oxide particles and firing in an oxygen atmosphere. it can. 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 crystals of the obtained NCA-based composite oxide particles 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 particles collapses, making it difficult to insert and desorb lithium ions. The firing time is preferably 5 hours to 20 hours, and more preferably 6 hours 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 in the same manner as the NCM-based composite oxide particles. The second baking is then performed at 650 ° C. to 850 ° C. for 5 hours or longer.

Finally, the obtained fired product is washed with water, filtered and dried to obtain layered rock salt structure type lithium composite oxide particles (B) represented by the formula (4). The slurry concentration when washing the fired product with water is preferably 200 g / L to 4000 g / L, and more preferably 500 g / L 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 particles.
In addition, when the water used for washing contains a large amount of carbon dioxide, lithium carbonate precipitates on the layered rock salt structure type lithium composite oxide particles (B), so that the electric conductivity of the water used for washing is 10 μS / Less than cm is preferable, and water of 1 μS / cm or less is more preferable.

  In the present invention, in this step (III '), the drying performed after washing with water and filtering needs to be performed in two stages. The drying in the first stage 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 drying in the second stage is performed at 120 ° C. This is done.

  The positive electrode active material composite for a lithium ion secondary battery of the present invention is applied as a positive electrode material, and as a lithium ion secondary battery including the same, a positive electrode, a negative electrode, an electrolytic solution, a separator, or a positive electrode, a negative electrode, and a solid electrolyte are essential. If it is set as a structure, it will not specifically limit.

Here, as long as lithium ions can be occluded at the time of charging and released at the time of discharging, the material configuration is not particularly limited, and a known material configuration can be used. For example, a carbon material such as lithium metal, graphite, silicon-based (Si, SiO _x ), lithium titanate, or amorphous carbon can be used. It is preferable to use an electrode formed of an intercalating material capable of electrochemically occluding and releasing lithium ions, particularly a carbon material. Furthermore, two or more kinds of the above negative electrode materials may be used in combination, and for example, a combination of graphite and silicon can be used.

  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 usually used for an electrolyte solution of a lithium ion secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones An oxolane compound or the like can be used.

The type of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , 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 ), organic salts, and derivatives of the organic salts It is preferable that it is at least 1 type of these.

  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 having the above configuration is not particularly limited, and may be various shapes such as a coin shape, a cylindrical shape, a square shape, and an indefinite shape sealed in a laminate outer package. .

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

[Production Example 1: Production of lithium-based polyanion particles (LMFP)]
A slurry A1 was obtained by mixing 4071 g of LiOH.H ₂ O and 9.657 L of water. Next, while the obtained slurry A1 was stirred for 3 minutes while maintaining the temperature at 25 ° C., 4204 g of a 75% aqueous phosphoric acid solution was added dropwise at 40 mL / min to obtain a slurry A2 containing Li ₃ PO ₄ .
The obtained slurry A2 was purged with nitrogen so that the dissolved oxygen concentration of the slurry A2 was 0.1 mg / L, and then 3807 g of MnSO ₄ · 5H ₂ O and 2684 g of FeSO ₄ · 7H ₂ O were added to the total amount of the slurry A2. Thus, slurry A3 was obtained. The molar ratio of MnSO ₄ and FeSO ₄ added (manganese compound: iron compound) was 70:30.
Next, the obtained slurry A3 was charged into an autoclave and subjected to a hydrothermal reaction at 170 ° C. for 0.5 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. Thereafter, it was dehydrated with a filter press device to obtain a dehydrated cake A4.
The average particle size of the lithium-based polyanion particles in the dehydrated cake A4 was 100 nm.
8000 g of the obtained dehydrated cake A4 was collected, 1200 g of cellulose nanofiber (KY100G, manufactured by Daicel Finechem) and 8.5 L of water were added to obtain slurry A5 having a solid content concentration of 30% by mass. The obtained slurry A5 was dispersed with an ultrasonic stirrer (T25, manufactured by IKA) for 10 minutes to uniformly color the whole, and then spray-dried (MDL-050M, manufactured by Fujisaki Electric Co., Ltd.). Spray drying was performed at a drying temperature of 130 ° C. to obtain a pre-granulated product A6.
The obtained pre-granulated product A6 was calcined at 700 ° C. for 1 hour in an argon hydrogen atmosphere (hydrogen concentration 3%), and phosphoric acid having 2.0% by mass of cellulose nanofiber-derived carbon supported on the surface. Granules made of lithium manganese iron secondary particles (LiMn _0.7 Fe _0.3 PO ₄ , amount of carbon = 2.0 mass%, average particle diameter: 11 μm, porosity 51 volume%, tap density 0.8 g / cm ³ ) Got.
Hereinafter, the granulated body composed of the lithium iron manganese phosphate secondary particles is referred to as LMFP.

Commercially available products having the following qualities were used for the layered rock salt structure type lithium composite oxide particles (B). Hereinafter, it is referred to as NCM.
Composition: LiNi _0.5 Co _0.2 Mn _0.3 O ₂
Average particle size: 10 μm
Tap density: 2.4 g / cm ³

[Example 1: (LMFP 70% + NCM 30%) composite a1]
LMFM 350g obtained in Production Example 1 and NCM 150g were combined with Nobilta (manufactured by Hosokawa Micron Corporation, NOB-130) for 10 minutes at a load of 2 kW at 20 m / s (2600 rpm). And a positive electrode active material composite a1 for a lithium ion secondary battery obtained by combining NCM.

[Example 2: (LMFP 80% + NCM 20%) composite a2]
A positive electrode active material composite a2 for a lithium ion secondary battery obtained by combining LMFP and NCM was obtained in the same manner as in Example 1 except that LLM was changed to 400 g and NCM was changed to 100 g.

[Example 3: (LMFP 90% + NCM 10%) composite a3]
A positive electrode active material composite a3 for a lithium ion secondary battery obtained by combining LMFP and NCM was obtained in the same manner as in Example 1 except that LLM was changed to 450 g and NCM was changed to 50 g.

[Example 4: (LMFP 95% + NCM 5%) composite a4]
A positive electrode active material composite a4 for a lithium ion secondary battery obtained by combining LMFP and NCM was obtained in the same manner as in Example 1 except that LMFP was changed to 475 g and NCM was changed to 25 g.

[Comparative Example 1: (LMFP 50% + NCM 50%) composite b1]
A positive electrode active material composite b1 for a lithium ion secondary battery obtained by combining LMFP and NCM was obtained in the same manner as in Example 1 except that LLM was changed to 250 g and NCM was changed to 250 g.

[Comparative Example 2: (LMFP 0% + NCM 100%) composite b2]
A positive electrode active material composite b2 for a lithium ion secondary battery obtained by combining only NCM was obtained in the same manner as in Example 1 except that LMFP was changed to 0 g and NCM was changed to 500 g.

[Comparative Example 3: (LMFP 90% + NCM 10%) mixture b3]
LMFP450g and NCM50g obtained in Production Example 1 are placed in a bag of 200 mm × 280 mm and mixed for 10 minutes, and LMF and NCM are simply mixed without being compounded. A substance mixture b3 was obtained.

≪Evaluation of the degree of NCM inclusion by LFP in composites by Raman spectroscopy≫
For all examples and for a lithium ion secondary battery obtained in Comparative Example positive active material composite or a lithium ion secondary battery positive electrode active material mixture, the presence or absence of a peak of 530 cm ^-1 ± 5 cm ^-1 by Raman spectroscopy It was confirmed. The peak was not observed in all of the examples, and it was confirmed that LMFP completely contained NCM, while the peak was observed in all of the comparative examples.
Table 1 shows the result when the LFP completely includes the NCM as “Yes” and when the LMFP does not include the NCM as “No”.
As a reference, the Raman spectrum for the positive electrode active material mixture b3 for lithium ion secondary battery obtained with the positive electrode active material composite a1 for lithium ion secondary battery obtained in Example 1 is shown in FIG. The Raman spectrum regarding the obtained positive electrode active material mixture b3 for lithium ion secondary batteries is shown in FIG.

≪Measurement of tap density≫
The positive electrode active material composite for lithium ion secondary batteries or the positive electrode active material mixture for lithium ion secondary batteries obtained in all Examples and Comparative Examples is defined in JIS R 1628 “Method for measuring bulk density of fine ceramic powder”. The tap density was measured in accordance with the tap bulk density measurement method.
The results are shown in Table 1.

≪Evaluation of volume energy density≫
A positive electrode slurry was prepared using the positive electrode active material composite for lithium ion secondary batteries or the positive electrode active material mixture for lithium ion secondary batteries obtained in all Examples and Comparative Examples as the positive electrode active material for secondary batteries. Specifically, a positive electrode active material for a secondary battery, acetylene black, and polyvinylidene fluoride are mixed at a mixing ratio of 90: 5: 5, and N-methyl-2 with respect to 100 parts by mass of the obtained mixture. -1 part by mass of pyrrolidone was added and kneaded sufficiently to prepare a positive electrode slurry.
Next, the positive electrode slurry was 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. 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.
Under the present circumstances, the electrode density was calculated | required by the following formula | equation (Y) from the thickness of the said positive electrode and the mass of the positive electrode active material for secondary batteries in a positive electrode.
The results are shown in Table 1.
Electrode density (g / cm ³ ) =
Active material mass (mg) in the positive electrode / electrode volume (φ14 mm × thickness (μm)) (Y)

Next, a coin-type secondary battery was constructed using the positive electrode. A lithium foil 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. Polypropylene was used for the separator. 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).

Using the obtained secondary battery, a discharge capacity of 0.1 C (17 mAh / g) in a temperature of 30 ° C. environment was measured with a discharge capacity measuring device (HJ-1001SD8, manufactured by Hokuto Denko). Furthermore, the capacity | capacitance retention by following formula (Z) by 10 times of charging / discharging in 1C was calculated | required. All charge / discharge tests were conducted at 45 ° C.
The results are shown in Table 1.
Capacity retention (%) = (discharge capacity after 10 cycles) / (discharge capacity after 1 cycle)
× 100 (Z)

Using the following formula (Q), the positive electrode volume energy density of secondary batteries using the positive electrode active materials for lithium ion secondary batteries of all Examples and Comparative Examples was determined.
The results are shown in Table 1.
Positive electrode volume energy density (mAh / cm ³ ) =
0.1 C discharge capacity (mAh / g) × electrode density (g / cm ³ ) (Q)

  From the result of Table 1, the positive electrode active material composite for lithium ion secondary batteries obtained by the present invention can obtain a positive electrode excellent in volume energy density, and the charge / discharge characteristics excellent in the secondary battery using this. It can also be seen that a high capacity retention rate is exhibited.

Claims (7)

The following formula (1):
Li _a Mn _b Fe _c M ¹ _d PO ₄ (1)
(In the formula (1), M ¹ represents Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. A, b, c, and d are 0.8 ≦ a ≦ 1.2, 0 ≦ b ≦ 1.2, 0 ≦ c ≦ 1.2, 0 ≦ d ≦ 0.3, and b + c ≠ 0, and a + 2b + 2c + (valence of M ¹ ) X indicates a number satisfying d = 3.)
Or the following formula (2):
^{_{Li e Co f Ni g M 2}} h PO 4 ··· (2)
(In Formula (2), M ² represents Fe, Mn, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. E, f, g, and h are 0.8 ≦ e ≦ 1.2, 0 ≦ f ≦ 1.2, 0 ≦ g ≦ 1.2, 0 ≦ h ≦ 0.3, and f + g ≠ 0, and e + 2f + 2g + (valence of M ² ) X indicates a number satisfying h = 3.)
In the secondary particles formed by complexing the lithium-based polyanion particles (A) represented by and having carbon (c) supported on the surface,
Following formula (3):
^{_{LiNi i Co j Mn k M 3}} l O 2 ··· (3)
(In the formula (3), 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 are shown, i, j, k, and l are 0.3 ≦ i <1, 0 <j ≦ 0.7, 0 <k ≦ 0.7, (0 ≦ l ≦ 0.3 and 3i + 3j + 3k + (M ³ valence) × l = 3)
Or following formula (4):
^{_{LiNi m Co n Al o M 4}} p O 2 ··· (4)
(In the formula (4), 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, where m, n, o, and p are 0.4 ≦ m <1, 0 <n ≦ 0.6, 0 <o ≦ 0.3, 0 ≦ p ≦ 0.3 and 3m + 3n + 3o + (the valence of M ⁴ ) × p = 3)
1 or more types of layered rock salt structure type lithium composite oxide particles (B) represented by
The average particle size of the lithium-based polyanion particles (A) is 50 nm to 300 nm,
The average particle size of the layered rock salt structure type lithium composite oxide particles (B) is 500 nm to 20 μm,
The amount of carbon (c) supported on the surface of the lithium-based polyanion particle (A) is 0.1% by mass or more and less than 18% by mass in 100% by mass of the lithium-based polyanion particle (A),
The mass ratio ((A) :( B)) of the content of the lithium-based polyanion particles (A) and the content of the layered rock salt structure type lithium composite oxide particles (B) is 95: 5 to 70:30. A positive electrode active material composite for a lithium ion secondary battery.   The lithium ion according to claim 1, wherein the carbon (c) supported on the surface of the lithium-based polyanion particle (A) is carbon (c1) derived from cellulose nanofibers or carbon (c2) derived from a water-soluble carbon material. Positive electrode active material composite for secondary battery. The electrical conductivity of the lithium-based polyanion particles (A) formed by supporting carbon (c) on the surface at a pressure of 20 MPa at 25 ° C. is 1 × 10 ⁻⁷ S / cm or more. The positive electrode active material composite for lithium ion secondary batteries according to 1 or 2. 4. The positive electrode active material composite for a lithium ion secondary battery according to claim 1, wherein no peak is present at 530 cm ⁻¹ ± 5 cm ⁻¹ in a Raman spectrum obtained by Raman spectroscopy.   The lithium ion secondary battery which contains the positive electrode active material composite for lithium ion secondary batteries of any one of Claims 1-4 as a positive electrode material. Next steps (I) to (II):
(I) Hydrothermal reaction product of lithium compound, metal compound containing at least iron compound or manganese compound, and phosphoric acid compound, or hydrothermal reaction product of lithium compound, metal compound containing at least cobalt compound or nickel compound, and phosphoric acid compound From the lithium-based polyanion particles (A) having a porosity of 45% to 80% by volume and carrying carbon (c) on the surface by spray drying using the reactant and the carbon source (C). A step of obtaining a formed granule (D),
(II) The granulated body (D) and the layered rock-salt structure type lithium composite oxide particles (B) are mixed while adding a compressive force and a shearing force to be combined to form a composite. The manufacturing method of the positive electrode active material composite for lithium ion secondary batteries of any one.   The compounding process in the step (II) is a process using an apparatus equipped with an impeller or a rotor tool, the rotation speed of the impeller or the rotor tool is 2000 rpm to 6000 rpm, and the mixing time is 0.5 minutes to 30 minutes. The method for producing a positive electrode active material composite for a lithium ion secondary battery according to claim 6, which is a treatment.

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