JP2015056275A - Process of manufacturing positive electrode active material for lithium ion secondary battery and process of manufacturing positive electrode for lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of manufacturing a positive electrode active material for a lithium ion secondary battery that improves initial charge and discharge efficiencies (initial efficiencies) of the lithium ion secondary battery.SOLUTION: The process of manufacturing a positive electrode active material for a lithium ion secondary battery includes a step of obtaining a lithium-containing complex oxide (II) by bringing a lithium-containing complex oxide (I) containing Li and a transition metal element into contact with a dispersion liquid containing a cation exchange resin, and decoupling the cation exchange resin after the contact.

Description

  The present invention relates to a method for producing a positive electrode active material for a lithium ion secondary battery, and a method for producing a positive electrode for a lithium ion secondary battery using the same.

Lithium ion secondary batteries are widely used in portable electronic devices such as mobile phones and notebook computers. The positive electrode active material for a lithium ion secondary battery includes a composite oxide of lithium and a transition metal such as LiCoO ₂ , LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ , LiMnO ₄ (hereinafter referred to as a lithium-containing composite). Oxide) is also used.
In recent years, miniaturization and weight reduction have been demanded for portable electronic devices and in-vehicle lithium ion secondary batteries, and further improvement in charge / discharge efficiency and maintenance of discharge capacity during long-term use is desired.

  Patent Document 1 discloses an aqueous solution containing a specific cation M, an aqueous solution containing an anion A that reacts with the cation M to form a hardly soluble salt, and a lithium-containing composite oxidation containing Li and a transition metal element. It describes a method for improving the retention rate (cycle retention rate) of the discharge capacity after repeating the discharge cycle by providing a coating layer on the lithium-containing composite oxide by heating after contacting the product. .

  Further, in Patent Document 2, when a lithium-containing composite oxide powder containing Li and a transition metal element is treated with nitric acid and treated with ammonia gas, and then heat-treated, the charge / discharge efficiency (initial efficiency) at the start of use is It is described that it has improved.

International Publication No. 2012/176904 US Pat. No. 7,314,682

However, in the conventional technology, the charge / discharge efficiency in the lithium ion secondary battery is not necessarily sufficient, and improvement is desired.
In order to improve the charge / discharge efficiency, it is preferable to improve the initial efficiency. Furthermore, it is more preferable that both the initial efficiency and the cycle maintenance ratio can be improved.
This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of the positive electrode active material for lithium ion secondary batteries which can improve the initial efficiency of a lithium ion secondary battery.
Preferably, it aims at providing the manufacturing method of the positive electrode active material for lithium ion secondary batteries which can improve the initial stage efficiency and cycle maintenance factor of a lithium ion secondary battery.
Moreover, an object of this invention is to provide the manufacturing method of the positive electrode for lithium ion secondary batteries using the manufacturing method of this positive electrode active material for lithium ion secondary batteries, and the manufacturing method of a lithium ion secondary battery.

The present invention includes the following [1] to [9].
[1] Lithium-containing composite oxide (I) containing Li and a transition metal element is brought into contact with a dispersion containing a cation exchange resin, and after the contact, the cation exchange resin is separated to obtain a lithium-containing composite oxide (II The manufacturing method of the positive electrode active material for lithium ion secondary batteries which has the process of obtaining.

[2] The lithium ion according to [1], wherein the relative amount (Xi) of the ion exchange capacity obtained by the lower formula (5) of the dispersion containing the cation exchange resin is 0.003 to 0.20. A method for producing a positive electrode active material for a secondary battery.
Relative amount of ion exchange capacity (Xi) = f1 × f2 / f0 (5)
However, f0-f2 in Formula (5) is as follows.
f0: Total amount of lithium element contained in the lithium-containing composite oxide (I) (unit: mole)
f1: Total ion exchange capacity of the cation exchange resin in a water wet state (unit: milliequivalent / mL)
f2: Amount of cation exchange resin contained in the dispersion (unit: mL)

[3] The step of bringing the lithium-containing composite oxide (II) into contact with at least one of the following composition (1) and composition (2), and heating the lithium-containing composite oxide (II) after the contact The manufacturing method of the positive electrode active material for lithium ion secondary batteries as described in [1] or [2] which has a process.
Composition (1): An aqueous solution containing an anion (A) containing at least one element (a) selected from the group consisting of S, P, F, and B.
Composition (2): Li, Mg, Ca, Sr, Ba, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Al, An aqueous solution containing a cation (M) of at least one metal element (m) selected from the group consisting of Ga, In, Sn, Sb, Bi, La, Ce, Pr, Nd, Gd, Dy, Er, and Yb .

[4] The lithium-containing composite oxide (II) is in contact with the composition (1), and the relative amount (Xa) of the anion (A) represented by the formula (6) is 0.001 to 0.15. A method for producing a positive electrode active material for a lithium ion secondary battery according to [3].
Relative amount of anion (A) (Xa) = Σ (f4 × f5) / f3 (6)
However, f3-f5 in Formula (6) are as follows.
f3: Total amount of transition metal element contained in lithium-containing composite oxide (I) (unit: mole)
f4: amount of each anion (A) contained in the composition (1) (unit: mole)
f5: Valence of each anion (A) [5] The lithium-containing composite oxide (II) is in contact with the composition (2), and the relative amount of the metal element (m) represented by the formula (7) ( Xm) is 0.001-0.15, The manufacturing method of the positive electrode active material for lithium ion secondary batteries as described in [4].
Relative amount of metal element (m) (Xm) = Σ (f6 × f7) / f3 (7)
However, f3, f6, and f7 in Formula (7) are as follows.
f3: Total amount of transition metal element contained in lithium-containing composite oxide (I) (unit: mole)
f6: amount of each cation (M) contained in the composition (2) (unit: mole)
f7: Valency of each anion (M) [6] The heating temperature in the step of heating the lithium-containing composite oxide (II) after contact with at least one of the composition (1) and the composition (2) is 250 to The manufacturing method of the positive electrode active material for lithium ion secondary batteries in any one of [3]-[5] which is 700 degreeC.

[7] The lithium-containing composite oxide (I) includes at least one transition metal element selected from the group consisting of Ni, Co, and Mn and Li, and the molar amount of Li is the total of the transition metal elements. The manufacturing method of the positive electrode active material for lithium ion secondary batteries in any one of [1]-[6] which is more than 1.2 times with respect to molar amount.
[8] The method for producing a positive electrode active material for a lithium ion secondary battery according to [7], wherein the lithium-containing composite oxide (I) is a compound represented by the following formula (1).
Li (Li _x1 Mn _y1 Me _z1 ) Me ′ _α O _p F _q (1)
However, Me is at least one element selected from the group consisting of Co and Ni, and Me ′ is at least one element selected from the group consisting of Al, Cr, Mg, Mo, Ru, Ti, Zr, and Fe. 0.1 <x1 <0.25, 0.5 ≦ y1 / (y1 + z1) ≦ 0.8, 0 ≦ α ≦ 0.1, x1 + y1 + z1 = 1, 1.9 <p <2.1, 0 ≦ q ≦ 0.1.

[9] A step of producing a positive electrode active material for a lithium ion secondary battery by the production method according to any one of [1] to [8], the positive electrode active material for a lithium ion secondary battery, a binder, and a conductive material. The manufacturing method of the positive electrode for lithium ion secondary batteries which has the process of forming the positive electrode active material layer containing a material on a positive electrode electrical power collector.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material for lithium ion secondary batteries which can improve the initial efficiency of a lithium ion secondary battery is obtained. Preferably, a positive electrode active material for a lithium ion secondary battery that can simultaneously improve the initial efficiency and cycle retention of the lithium ion secondary battery is obtained.

  Embodiments of the present invention will be described below. In this specification, an element symbol (for example, “Li”) indicates an element, and does not indicate a single substance (for example, metal) of the element unless otherwise specified.

<Method for producing positive electrode active material for lithium ion secondary battery>
The method for producing a positive electrode active material for a lithium ion secondary battery of the present invention (hereinafter referred to as this production method) contains a lithium-containing composite oxide (I) containing Li and a transition metal element, and a cation exchange resin. The step of contacting with the dispersion and separating the cation exchange resin after the contact to obtain the lithium-containing composite oxide (II) (hereinafter referred to as step (I)) is included.
Furthermore, the step of bringing the lithium-containing composite oxide (II) obtained in step (I) into contact with at least one of the following composition (1) or composition (2) (hereinafter referred to as step (II)). And a step of heating the lithium-containing composite oxide (II) after contact (hereinafter referred to as step (III)). Lithium-containing composite oxide (III) having a coating layer on a part of the surface of lithium-containing composite oxide (II) is obtained by passing through steps (II) and (III) after step (I).
When performing the steps (I), (II) and (III), other steps may be included between the respective steps as long as the steps (I) to (III) are performed in this order. From the viewpoint of production efficiency, it is preferable to perform steps (I) to (III) successively in this order.
The lithium-containing composite oxide (II) obtained in step (I) may be used as a positive electrode active material for a lithium ion secondary battery, and contains lithium obtained through steps (I), (II) and (III). The composite oxide (III) may be used as a positive electrode active material for a lithium ion secondary battery.

The composition (1) and the composition (2) are the following aqueous solutions, respectively.
Composition (1): An aqueous solution containing an anion (A) containing at least one element (a) selected from the group consisting of S, P, F, and B.
Composition (2): Li, Mg, Ca, Sr, Ba, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Al, An aqueous solution containing a cation (M) of at least one metal element (m) selected from the group consisting of Ga, In, Sn, Sb, Bi, La, Ce, Pr, Nd, Gd, Dy, Er, and Yb .

[Lithium-containing composite oxide]
The lithium-containing composite oxide (I) used in this production method contains Li and a transition metal element. In step (I) of this production method, the lithium-containing composite oxide before being brought into contact with the dispersion containing the cation exchange resin is referred to as lithium-containing composite oxide (I).
The lithium-containing composite oxide (I) is at least one selected from the group consisting of Ni, Co, Mn, Fe, Cr, V, Mo, Ru, Ti, Nb, Zn, Zr, and Cu as a transition metal element. It is preferable to contain.
As the lithium-containing composite oxide, a known lithium-containing composite oxide can be used as an active material for a lithium ion secondary battery. A lithium containing complex oxide may be used individually by 1 type, and may use 2 or more types together.
As the lithium-containing composite oxide (I), for example, the following compound (i), (ii), (iii), or (iv) is preferable.
Compound (i): containing at least one transition metal element selected from the group consisting of Ni, Co, and Mn and Li, wherein the molar amount of Li is 1.2 times the total molar amount of the transition metal element A compound that is super. Compound (i) is preferably a compound represented by the following formula (1).
Compound (ii): Compound represented by the following formula (2).
Compound (iii): A compound represented by the following formula (3) or a complex thereof, which is an olivine-type metal lithium salt.
Compound (iv): A compound represented by the following formula (4).
Among these, the compound (i) is more preferable in that a high capacity in a lithium ion secondary battery can be obtained.

[Compound (i)]
Li (Li _x1 Mn _y1 Me _z1 ) Me ′ _α O _p F _q (1)
In formula (1), Me is at least one element selected from the group consisting of Co and Ni, and Me ′ is selected from the group consisting of Al, Cr, Mg, Mo, Ru, Ti, Zr, and Fe. At least one kind. 0.1 <x1 <0.25, 0.5 ≦ y1 / (y1 + z1) ≦ 0.8, 0 ≦ α ≦ 0.1, x1 + y1 + z1 = 1, 1.9 <p <2.1, 0 ≦ q ≦ 0.1.
As the compound (i), Li (Li _0.16 Ni _0.17 Co _0.08 Mn _0.59 ) O ₂ , Li (Li _0.17 Ni _0.17 Co _0.17 Mn _0.49 ) O ₂ , Li (Li _0.17 Ni _0.21 Co _0.08 Mn _0.54 ) O ₂ , Li (Li _0.17 Ni _0.14 Co _0.14 Mn _0.55 ) O ₂ , Li (Li _{0. 18} Ni _0.12 Co _0.12 Mn _0.58 ) O ₂ , Li (Li _0.18 Ni _0.16 Co _0.12 Mn _0.54 ) O ₂ , Li (Li _0.20 Ni _0.12 Co _0.08 Mn _0.60 ) O ₂ , Li (Li _0.20 Ni _0.16 Co _0.08 Mn _0.56 ) O ₂ , Li (Li _0.20 Ni _0.13 Co _0.13 Mn _{0. 54} ) O ₂ is particularly preferred.

The compound represented by the above formula (1) preferably has a peak attributed to the layered rock salt type crystal structure (space group R-3m) in XRD (X-ray source: CuKα) measurement. Furthermore, since the ratio of Li to the transition metal element is high, it is more preferable to have a peak attributed to the crystal structure of the layered Li ₂ MnO ₃ . The peak attributed to the layered Li ₂ MnO ₃ is observed in the range of 2θ = 20 to 25 ° in the XRD spectrum.

[Compound (ii)]
Li _a (Ni _x2 Mn _y2 Co _z2 ) Me '' _b O ₂ (2)
In the formula (2), 0.95 ≦ a ≦ 1.1, 0 ≦ x2 ≦ 1, 0 ≦ y2 ≦ 1, 0 ≦ z2 ≦ 1, 0 ≦ b ≦ 0.3, 0.90 ≦ x2 + y2 + z2 + b ≦ 1. 05, Me ″ is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Al, Ti, Zr, Fe, Sn, and Cr.
Examples of the compound (ii) represented by the formula (2) include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn _0.5 Ni _0.5 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O. ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ .

[Compound (iii)]
The olivine-type metal lithium salt (compound (iii)) is a compound represented by the following formula (3) or a complex thereof.
_{Li L X x3 Y y3 O z3} F g ··· (3)
In formula (3), X represents Fe, Co, Mn, Ni, V, or Cu, Y represents P or Si, and 0 <L ≦ 3, 1 ≦ x3 ≦ 2, 1 ≦ y3 ≦ 3, 4 ≦ z3 ≦ 12 and 0 ≦ g ≦ 1.
As the compound (iii), LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , LiFeP ₂ O ₇ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₂ FePO ₄ F, Li ₂ MnPO ₄ F, Li ₂ NiPO _{4 F, Li 2 CoPO 4 F,} Li 2 FeSiO 4, Li 2 MnSiO 4, Li 2 NiSiO 4, Li 2 CoSiO 4 can be cited.

[Compound (iv)]
Li (Mn _2-x4-y4 Me ′ ″ _x4 Li _y4 ) O _4-h F _h (4)
However, in formula (4), 0 ≦ x4 <2, 0 ≦ y4 ≦ 0.33, 0 ≦ h ≦ 0.1, and Me ′ ″ is Co, Ni, Fe, Ti, Cr, Mg, Ba , Nb, Ag, Cu, Sn, Zn, Ga, and Al.
As the compound (iv) represented by the formula (4), LiMn ₂ O ₄ , LiMn _1.5 Ni _0.5 O ₄ , LiMn _1.0 Co _1.0 O ₄ , LiMn _1.85 Al _0.15 O ₄ , LiMn _1.9 Mg _0.1 O ₄ may be mentioned.

The lithium-containing composite oxide (I) is preferably particulate. Moreover, as for the average particle diameter (D50) of lithium containing complex oxide (I), 0.03-30 micrometers is preferable. When the lithium-containing composite oxide (I) is the compound (i), the compound (ii) or the compound (iv), D50 is preferably 3 to 30 μm, more preferably 4 to 25 μm, and particularly preferably 5 to 20 μm. When the lithium composite oxide (I) is the compound (iii), D50 is preferably 0.03 to 5 μm, more preferably 0.04 to 1 μm, and particularly preferably 0.05 to 0.5 μm.
In the present specification, D50 is a volume-based cumulative 50% diameter which is a particle diameter at a point where the cumulative curve is 50% in a cumulative curve where the particle size distribution is obtained on a volume basis and the total volume is 100%. means. The particle size distribution is obtained from a frequency distribution and a cumulative volume distribution curve measured with a laser scattering particle size distribution measuring apparatus. The particle size is measured by sufficiently dispersing the powder in an aqueous medium by ultrasonic treatment or the like to measure the particle size distribution (for example, a laser diffraction / scattering particle size distribution measuring device Partica LA-950VII manufactured by HORIBA, etc.). Used).

[Method for producing lithium-containing composite oxide]
The lithium-containing composite oxide (I) can be produced by mixing a coprecipitate containing a transition metal obtained by a coprecipitation method with a lithium compound and baking, hydrothermal synthesis method, sol-gel method, dry mixing A method (solid phase method), an ion exchange method, or a glass crystallization method can be appropriately used.
In particular, a method in which a coprecipitate and a lithium compound are mixed and fired is preferable because a high discharge capacity is easily obtained. As the coprecipitation method, an alkali coprecipitation method and a carbonate coprecipitation method are preferable.
When the lithium composite oxide (I) is a compound selected from the compound (i), a carbonate coprecipitation method is preferable because a high discharge capacity is easily obtained.
Each of these production methods can be performed using a known method.

[Alkaline coprecipitation]
The alkali coprecipitation method is a method in which an aqueous solution of a metal salt containing a transition metal element and a pH adjusting solution containing a strong alkali are continuously mixed to maintain a constant pH in the reaction solution. This is a method of depositing a hydroxide containing a metal element. In the alkali coprecipitation method, a coprecipitate having a high powder density is obtained. When the coprecipitate is used, a positive electrode active material having excellent filling properties in the positive electrode active material layer can be obtained.

  Examples of the metal salt containing a transition metal element include nitrates, acetates, chlorides, and sulfates of transition metal elements. Since the material cost is relatively low and excellent battery characteristics are obtained, a transition metal element sulfate is preferable, and a sulfate composed of Ni sulfate, Co sulfate and Mn sulfate is more preferable.

Examples of the sulfate of Ni include nickel (II) sulfate hexahydrate, nickel (II) sulfate heptahydrate, nickel sulfate (II) ammonium hexahydrate, and the like.
Examples of Co sulfate include cobalt (II) sulfate heptahydrate and cobalt (II) ammonium sulfate hexahydrate.
Examples of the sulfate of Mn include manganese sulfate (II) pentahydrate, manganese sulfate (II) ammonium hexahydrate, and the like.

The pH of the solution during the reaction in the alkali coprecipitation method is preferably 10-12.
The pH adjusting solution containing a strong alkali is preferably an aqueous solution containing at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide. Among these, an aqueous sodium hydroxide solution is more preferable.
In order to adjust the solubility of the transition metal element, an aqueous ammonia solution or an aqueous ammonium sulfate solution may be added to the reaction solution in the alkali coprecipitation method.

[Carbonate coprecipitation]
The carbonate coprecipitation method is a method in which a metal salt aqueous solution containing a transition metal element and an aqueous solution containing a carbonate ion source are continuously mixed to precipitate a carbonate containing a transition metal element in the reaction solution. . In the carbonate coprecipitation method, a porous coprecipitate having a high specific surface area can be obtained. When the coprecipitate is used, a positive electrode active material exhibiting a high discharge capacity can be obtained.
Examples of the metal salt containing a transition metal element used in the carbonate coprecipitation method include the same transition metal salts as those exemplified in the alkali coprecipitation method.

The pH of the solution during the reaction in the carbonate coprecipitation method is preferably 7-9.
The carbonate ion source is preferably at least one selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.
An aqueous ammonia solution or an aqueous ammonium sulfate solution may be added to the reaction solution in the carbonate coprecipitation method for the same reason as in the alkali coprecipitation method.

  For the reaction solution containing the coprecipitate deposited by the alkali coprecipitation method or the carbonate coprecipitation method, it is preferable to carry out a step of removing the aqueous solution by filtration, sedimentation separation, or centrifugation. For filtration or centrifugation, a pressure filter, a vacuum filter, a centrifugal classifier, a filter press, a screw press, a rotary dehydrator, or the like can be used.

  It is preferable to carry out a step of washing the obtained coprecipitate. By washing, impurity ions such as sodium attached to the coprecipitate can be removed. Examples of the method for washing the coprecipitate include a method of repeating filtration and dispersion in ion-exchanged water.

A lithium-containing composite oxide is obtained by mixing and calcining a coprecipitate obtained by the coprecipitation method and a lithium compound. As the lithium compound, for example, lithium carbonate, lithium hydroxide, or lithium nitrate is preferable, and lithium carbonate is more preferable because it is inexpensive.
The firing temperature is preferably 500 to 1000 ° C. When the firing temperature is within the above range, a lithium-containing composite oxide having high crystallinity is easily obtained. The firing temperature is more preferably 600 to 1000 ° C, particularly preferably 800 to 950 ° C.
The firing time is preferably 4 to 40 hours, and more preferably 4 to 20 hours.
Firing is preferably performed in an oxygen-containing atmosphere, for example, while supplying air.
By firing in an oxygen-containing atmosphere, the transition metal element in the coprecipitate is sufficiently oxidized, and the crystallinity tends to be high.

[Step (I)]
In this production method, the lithium-containing composite oxide (I) is brought into contact with a dispersion containing a cation exchange resin, and after the contact, the cation exchange resin is separated to obtain a lithium-containing composite oxide (II).
The lithium-containing composite oxide (I) includes Li that does not form the crystal structure of the lithium-containing composite oxide as an impurity. Further, the lithium-containing composite oxide (I) may contain alkaline components such as Li, Na, and K derived from production raw materials (coprecipitates, lithium compounds, etc.). These alkali components are hereinafter referred to as free alkalis. If a lithium-containing composite oxide containing free alkali is used as the positive electrode active material of the lithium ion secondary battery, battery characteristics such as charge / discharge efficiency of the lithium ion secondary battery may be deteriorated.
In the present invention, free alkali can be removed from the lithium-containing composite oxide (I) by bringing the lithium-containing composite oxide (I) into contact with a dispersion containing a cation exchange resin. As a result, the battery characteristics of the lithium ion secondary battery using the lithium-containing composite oxide (II) as the positive electrode active material can be improved.
The present invention is easier to process than a method of removing free alkali from a lithium-containing composite oxide using, for example, a cleaning solution capable of dissolving free alkali, and the amount of waste liquid is reduced in the process of removing free alkali. it can. Therefore, the present invention can be said to be a method that can reduce the environmental load.

  In this production method, the cation exchange resin can remove alkaline components such as Li, Na, and K. Examples of the cation exchange resin include strong acid cation exchange resins and weak acid cation exchange resins. The cation exchange resin preferably has a sulfonic acid group or a carboxylic acid group as an ion exchange group.

  The cation exchange resin preferably has a total ion exchange capacity of 0.5 (milli equivalent / mL-water wet resin) or more per mL of water wet resin, 1.0 (milli equivalent / mL-water wet resin) or more. Are more preferred. The total ion exchange capacity is the total number of ion exchange groups involved in ion exchange per unit resin amount in a wet state. The water wet resin means a resin obtained by wetting a cation exchange resin with water.

The cation exchange resin is preferably used in an H-type ion exchange resin, that is, in a state having H ⁺ as a counter ion of the ion exchange group. The ion exchange group can be converted to the H type by a treatment (hereinafter referred to as a regeneration treatment) in which the cation exchange resin is brought into contact with a strongly acidic aqueous solution such as HCl. For example, when a commercially available product is used as the cation exchange resin, it is preferable to use it after regeneration before use if the ion exchange group is bonded to an alkali metal such as Na. Further, the cation exchange resin used in the step (I) of the present invention can be repeatedly used by performing a regeneration treatment.

The shape and size of the cation exchange resin are not particularly limited as long as it can be dispersed in a dispersion medium and can be separated from the lithium-containing composite oxide (II) by solid-liquid separation operation.
The cation exchange resin is preferably particulate from the viewpoint of ease of separation from the lithium-containing composite oxide (II), and is preferably a crosslinked type from the viewpoint of shape stability.
It is preferable to use particles having a particle size in the range of 0.05 mm to 3.0 mm in terms of improvement in handleability, ion exchange reaction speed, safety of ion exchange resin, and the like. A range of 15 mm to 1.5 mm is more preferable.
The cation exchange resin may be a gel type without macropores, a porous type having macropores, or a highly porous high porous type.
As such a cation exchange resin, for example, Diaion SK1BH (trade name, manufactured by Mitsubishi Chemical Co., Ltd., strong acid cation exchange resin, total ion exchange capacity 2.0 meq / mL-water wet resin, particle size 0 .3 mm to 1.18 mm), Diaion WK40L (trade name, manufactured by Mitsubishi Chemical Corporation, weakly acidic cation exchange resin, total ion exchange capacity 4.4 meq / mL-water wet resin, particle size 0.3 mm to 1 .18 mm).

As a dispersion medium of the dispersion liquid containing a cation exchange resin, water or a mixed solvent of a water-soluble organic solvent and water can be used. Examples of the water-soluble organic solvent include methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, butanediol, glycerin, acetone, dimethylformamide, N-methylpyrrolidone and the like. It is done. Water is preferable because it is excellent in safety, the rate of ion exchange reaction, and the stability of the ion exchange resin.
The content of the cation exchange resin in the dispersion containing the cation exchange resin is preferably 5 to 100 mL, more preferably 10 to 50 mL, with respect to 100 mL of the dispersion medium. If the content of the cation exchange resin is within the above range, the ion exchange reaction is sufficient, and the separation of the ion exchange resin after the contact between the dispersion and the lithium-containing composite oxide is easy.

As a method of bringing the lithium-containing composite oxide (I) and the dispersion into contact with each other, for example, a method of adding the lithium-containing composite oxide (I) to the dispersion and stirring and mixing can be used. The contact with the dispersion may be performed a plurality of times.
The temperature of the dispersion to be brought into contact with the lithium-containing composite oxide (I) is preferably from 10 to 90 ° C, more preferably from 20 to 60 ° C, from the viewpoint of improving workability and charge / discharge efficiency.
The time for which the lithium-containing composite oxide (I) is brought into contact with the dispersion is not particularly limited, but is preferably 0.5 hours or more and preferably 1 hour or more in terms of obtaining high charge / discharge efficiency and high discharge capacity. The upper limit of the contact time is preferably 48 hours or less, more preferably 24 hours or less from the viewpoint of productivity.

The dispersion containing the ion exchange resin preferably has a relative amount (Xi) of the ion exchange capacity obtained by the following formula (5) of 0.003 to 0.2, more preferably 0.01 to 0.15. Preferably, 0.02 to 0.1 is particularly preferable. If the relative amount (Xi) of the ion exchange capacity is not less than the lower limit of the above range, the charge / discharge efficiency and discharge capacity of the lithium ion secondary battery having the obtained lithium ion-containing composite oxide can be increased. If the step (I) is carried out below the upper limit, elution of the transition metal component can be reduced and the yield is increased.
The relative amount (Xi) of the ion exchange capacity is the total ion exchange capacity of the cation exchange resin in the dispersion with respect to the molar amount of Li contained in the lithium-containing composite oxide (I). expressed.
Relative amount of ion exchange capacity (Xi) = f1 × f2 / f0 (5)
However, f0-f2 in Formula (5) is as follows.
f0: Total amount of lithium element contained in the lithium-containing composite oxide (I) (unit: mole)
f1: Ion exchange capacity of cation exchange resin in water wet state (unit: milliequivalent / mL)
f2: Amount of cation exchange resin contained in the dispersion (unit: mL)

After bringing the lithium-containing composite oxide (I) and the dispersion into contact with each other, the cation exchange resin is separated to obtain the lithium-containing composite oxide (II). As a separation method, a general solid-liquid separation method for separating two or more kinds of particles having different particle sizes from the dispersion can be used. Specific examples include filtration, sieving, sedimentation separation, or centrifugation.
By the solid-liquid separation, a slurry containing lithium-containing composite oxide (II) and a dispersion medium is obtained. Furthermore, in order to remove a part or all of the dispersion medium, it is preferable to heat dry. By removing part or all of the dispersion medium, the lithium-containing composite oxide (II) can be easily handled. Moreover, when performing process (II), the process efficiency of process (II) can be improved. The heating temperature is preferably 40 to 300 ° C, more preferably 60 to 200 ° C. A heating time is not specifically limited, For example, 0.5 to 30 hours are preferable, and 1 to 20 hours are more preferable.
When the heating temperature is within the above range, it can be efficiently dried.

[Step (II)]
In step (II) of this production method, the lithium-containing composite oxide (II) obtained in step (I) is brought into contact with at least one of composition (1) and composition (2).
If the positive electrode active material obtained through this step is used, at least one of the charge / discharge efficiency or the cycle characteristics of the lithium ion secondary battery can be further improved. The anion (A) contained in the composition (1) extracts Li from the lithium-containing composite oxide (II) and improves the charge / discharge efficiency of the lithium ion secondary battery. If the metal element (m) contained in the composition (2) is present on the surface, elution of the transition metal from the lithium-containing composite oxide can be suppressed, and the cycle characteristics of the lithium ion secondary battery are improved.

In the step (II), when both the composition (1) and the composition (2) are brought into contact with the lithium-containing composite oxide (II), the composition (1) and the composition (2) are simultaneously or successively What is necessary is just to make it contact, and the order to contact is not limited. As a mode of continuous contact, a mode of contacting the composition (2) after contacting the composition (1) with the lithium-containing composite oxide (II), and a mode of contacting the composition (2) Examples include an aspect in which (1) is contacted, and an aspect in which one composition and the other composition are alternately contacted a plurality of times. As an aspect to contact simultaneously, after making the composition (1) and the composition (2) contact the lithium-containing composite oxide (II) simultaneously, the composition (1) and the composition (2) are mixed in advance, The aspect etc. which a mixture is made to contact are mentioned.
In particular, since it is considered that the reaction between the cation (M) and the anion (A) is likely to proceed, the composition (1) is brought into contact with the lithium-containing composite oxide (II) after contacting the composition (2). It is particularly preferable to set the order of contact.

In the step (II), the contact method between the lithium-containing composite oxide (II) and at least one of the composition (1) and the composition (2) is preferably a spray coating method. The spray coating method is a method in which at least one of the composition (1) and the composition (2) is sprayed on the lithium-containing composite oxide (II), and the process is simple and the surface of the lithium-containing composite oxide is coated. This is preferable because the layer can be formed uniformly.
Specifically, in the spray coating method, at least one of the composition (1) and the composition (2) is sprayed on the lithium-containing composite oxide (II) under stirring to form the lithium-containing composite oxide (II). It is preferable to mix. As a stirring device, a low shearing stirrer such as a drum mixer or solid air can be used.

[Composition (1)]
Composition (1): An aqueous solution containing at least one anion (A) containing at least one element (a) selected from the group consisting of S, P, F, and B.
The anion (A) includes both an anion composed of a single atom of the element (a) and an anion composed of a polyatom including the element (a). Moreover, anion (A) may use any 1 type individually, and may use multiple types.
The anion (A) is SO ₄ ²⁻ , SO ₃ ²⁻ , S ₂ O ₃ ²⁻ , SO ₆ ²⁻ , SO ₈ ²⁻ , PO ₄ ³⁻ , P ₂ O ₇ ⁴⁻ , PO ₃ ^3−. , PO ₂ ³⁻ , F ⁻ , BO ₃ ³⁻ , BO ₂ ⁻ , B ₄ O ₇ ²⁻ , or B ₅ O ₈ ⁻ are preferable. Among these, SO ₄ ²⁻ , PO ₄ ³⁻ , or F ⁻ is more preferable from the viewpoint of stability and handleability. In particular, the anion (A) is more preferably F ^{− in} that a high discharge capacity can be obtained.

The composition (1) preferably contains the element (a) and dissolves the water-soluble compound (1) that is dissociated in an aqueous solution to form the anion (A). In this specification, the solubility in distilled water at 25 ° C. (the mass [g] of the solute dissolved in 100 g of the saturated solution) is more than 2 and is said to be water-soluble, and the solubility is 0 to 2. Slightly soluble.
Preferable examples of the water-soluble compound (1) having a solubility exceeding ₂ include H ₂ SO ₄ , H ₂ SO ₃ , H ₂ S ₂ O ₃ , H ₂ SO ₆ , H ₂ SO ₈ , and H ₃ PO _4. , H ₄ P ₂ O ₇ , H ₃ PO ₃ , H ₃ PO ₂ , HF, H ₃ BO ₃ , HBO ₂ , H ₂ B ₄ O ₇ , HB ₅ O ₈ , or ammonium salts, amine salts, lithium thereof Salt, sodium salt, potassium salt and the like. Among these, it is preferable to use a salt rather than an acid in terms of handleability and safety. An ammonium salt is particularly preferable in that it is decomposed and removed when heated. Specifically, (NH ₄ ) ₂ SO ₄ , (NH ₄ ) HSO ₄ , (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , (NH ₄ ) H ₂ PO ₄ , NH ₄ F and the like are preferable. .

The solvent of the composition (1) may contain one or both of a water-soluble alcohol and a polyol as long as the solubility of the water-soluble compound (1) is not impaired.
Examples of the water-soluble alcohol include methanol, ethanol, 1-propanol, and 2-propanol. Examples of the polyol include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, butanediol, and glycerin.
In the composition (1), the total content of the water-soluble alcohol and the polyol contained in the solvent is preferably 0 to 20%, more preferably 0 to 10% with respect to the total mass of the solvent. In view of safety, environment, handling, and cost, the solvent is particularly preferably water only.

  The composition (1) may contain a pH adjuster in order to adjust the solubility of the water-soluble compound (1). As the pH adjuster, those that volatilize or decompose when heated in a later step are preferable. For example, an organic acid such as acetic acid, citric acid, lactic acid, formic acid, maleic acid, oxalic acid, or ammonia is preferable. As described above, when a pH adjuster that volatilizes or decomposes is used, it is difficult for impurities to remain, and thus good battery characteristics are easily obtained.

The content of the water-soluble compound (1) is preferably 0.5 to 30% and particularly preferably 2 to 20% in terms of anion (A) with respect to the total mass of the composition (1).
If the water-soluble compound (1) is 0.5% or more, it is preferable because the solvent is easily removed by heating in the subsequent step. Moreover, if it is 30% or less, the viscosity of a composition (1) will become an appropriate range, and it is preferable at the point which is easy to make lithium containing complex oxide (II) and a composition (1) contact uniformly.

When the composition (1) is brought into contact with the lithium-containing composite oxide (II), the relative amount (Xa) of the anion (A) in the composition (1) is within the range of 0.001 to 0.15. Preferably there is. When the relative amount (Xa) of the anion (A) is 0.001 or more, the charge / discharge efficiency is easily improved, and when it is 0.15 or less, capacity reduction due to impurity generation hardly occurs. The value of the relative amount (Xa) of the anion (A) is more preferably within the range of 0.003 to 0.12, and particularly preferably within the range of 0.005 to 0.09.
The relative amount (Xa) of the anion (A) is based on the molar amount of the anion (A) contained in the composition (1) with respect to the total amount of transition metal elements contained in the lithium-containing composite oxide (I). It is a value obtained by multiplying the absolute value of the valence of (A).
In addition, when two or more types of anions (A1), (A2)... Are included in the composition (1), the relative amount (Xa) of the anions (A) is included in the composition (1). The sum of all anions. That is, the product of the molar amount of the anion (A1) and the valence of the anion (A1), the product of the molar amount of the anion (A2) and the valence of the anion (A2), and the sum of these are obtained. A value obtained by dividing the total amount of transition metal elements contained in the contained composite oxide (I).
The relative amount (Xa) of the anion (A) in the composition (1) is represented by the formula (6).
Relative amount of anion (A) (Xa) = Σ (f4 × f5) / f3 (6)
However, f3-f5 in Formula (6) are as follows.
f3: Total amount of transition metal element contained in lithium-containing composite oxide (I) (unit: mole)
f4: amount of each anion (A) contained in the composition (1) (unit: mole)
f5: Valence of each anion (A)

[Composition (2)]
The composition (2) in the present invention includes Li, Mg, Ca, Sr, Ba, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Cations of at least one metal element (m) selected from the group consisting of Zn, Al, Ga, In, Sn, Sb, Bi, La, Ce, Pr, Nd, Gd, Dy, Er, and Yb (M ).
The cation (M) of the metal element (m) includes both a single atom of each metal element (m) or a complex containing each metal element (m). In terms of reactivity with the anion (A) of the composition (1), the cation (M) is preferably a monoatomic ion of the metal element (m).
Any one of the metal elements (m) may be used alone, or a plurality of them may be used. As the metal element (m), Al, Nb, or Zr is preferable. As the cation (M), Al ³⁺ , Nb ⁵⁺ , Nb ³⁺ , or Zr ⁴⁺ is preferable. In particular, from the viewpoint of improving cycle characteristics, the metal element (m) is preferably Al, and the cation (M) is preferably Al ³⁺ .

The composition (2) preferably has a metal element (m) and is obtained by dissolving a water-soluble compound (2) that generates a cation (M) in an aqueous solution in a solvent.
Examples of the water-soluble compounds (2) include inorganic salts such as nitrates, sulfates and chlorides of metal elements (m), acetates, citrates, maleates, formates, lactates, lactates, sulphate Examples thereof include organic salts such as acid salts, organic complexes, and ammine complexes. Among these, nitrates, organic acid salts, organic complexes, and ammine complexes are particularly preferable because they are easily decomposed by heat and have high solubility in a solvent.
Preferred examples of the water-soluble compound (2) include ammonium zirconium carbonate, ammonium zirconium halide, zirconium acetate, zirconium nitrate, aluminum nitrate, aluminum acetate, aluminum oxalate, aluminum citrate, aluminum lactate, basic aluminum lactate, malein Examples thereof include aluminum oxide, niobium nitrate, niobium acetate, niobium citrate, niobium maleate, niobium formate, niobium lactate, niobium oxalate, and ammonium niobium oxalate.

  As the solvent of the composition (2), one or both of a water-soluble alcohol and a polyol similar to those of the composition (1) may be added as long as the solubility of the water-soluble compound (2) is not impaired. Moreover, the content is the same as that of the composition (1). Furthermore, in order to adjust the solubility of the water-soluble compound (2), the composition (2) may contain the same pH adjuster as that of the composition (1).

The content of the aqueous solution compound (2) is preferably 0.5 to 30% and particularly preferably 2 to 20% in terms of the metal element (m) with respect to the total mass of (2) of the composition.
If the water-soluble compound (2) is 0.5% or more, it is preferable because the solvent can be easily removed by heating in a later step. Moreover, if it is 30% or less, the viscosity of a composition (2) will become an appropriate range, and it is preferable at the point which is easy to make lithium containing complex oxide (II) and a composition (2) contact uniformly.

When the composition (2) is brought into contact with the lithium-containing composite oxide (II), the relative amount (Xm) of the metal element (m) in the composition (2) is within the range of 0.001 to 0.15. Preferably there is. When the value of the relative amount (Xm) of the metal element (m) is 0.001 or more, the effect of improving the cycle characteristics is increased, and when the value is 0.15 or less, the capacity is not easily reduced due to impurity generation. The value of the relative amount (Xm) of the metal element (m) is more preferably in the range of 0.003 to 0.12, and particularly preferably in the range of 0.005 to 0.09.
The relative amount (Xm) of the metal element (m) is the cation (M) of the metal element (m) contained in the composition (2) with respect to the total amount of the transition metal element contained in the lithium-containing composite oxide (I). Is a value obtained by multiplying the molar amount of the valence of the cation (M) by the absolute value.
In addition, when 2 or more types of metal elements (m1), (m2)... Are included in the composition (1), the relative amount (Xm) of the metal element (m) is included in the composition (2). It is the total value of all metal elements. That is, the product of the molar amount of the cation (M1) containing the metal element (m1) and the valence of the cation (M1), the molar amount of the cation (M2) containing the metal element (m2) and the cation (M2) Are obtained by dividing the sum of these by the total amount of transition metal elements contained in the lithium-containing composite oxide (I).
The relative amount (Xm) of the cation (M) in the composition (1) is represented by the formula (7).
Relative amount of metal element (m) (Xm) = Σ (f6 × f7) / f3 (7)
However, f3 in Formula (7) is the same as Formula (6), and f6 and f7 are as follows.
f6: amount of each cation (M) contained in the composition (2) (unit: mole)
f7: Valence of each cation (M)

  Furthermore, the amount of the composition (1) and the amount of the composition (2) that are brought into contact with the lithium-containing composite oxide (II) are the relative amount of the metal element (m) (Xm) / the relative amount of the anion (A). It is preferable that ratio (Xm / Xa) of both represented by (Xa) is 0.1-10. The ratio (Xm / Xa) of the two is more preferably 0.2 to 5, and further preferably 0.3 to 3. When the ratio (Xm / Xa) of the two is within the above range, a positive electrode active material having a high discharge capacity and high cycle characteristics is easily obtained.

[Step (III)]
In this production method, the lithium-containing composite oxide (II) after contacting with at least one of the composition (1) and the composition (2) in the step (II) is heated. This heating removes volatile impurities such as water and organic components contained in at least one of the lithium-containing composite oxide (II), the composition (1) and the composition (2), and covers a part of the surface. A lithium-containing composite oxide (III) having a layer is obtained.

The heating in step (III) is preferably performed in an oxygen-containing atmosphere. The heating temperature is preferably 250 to 700 ° C, and more preferably 350 to 600 ° C. A coating layer can be favorably formed as heating temperature is 250 degreeC or more. Further, since volatile impurities such as residual moisture are reduced, a decrease in cycle maintenance rate can be suppressed.
On the other hand, when the heating temperature is 700 ° C. or lower, the metal element (m) is difficult to diffuse inside the positive electrode active material, and the battery capacity can be prevented from decreasing due to the diffusion of the metal element (m).
When the coating layer is amorphous, the heating temperature is preferably 250 ° C to 550 ° C, more preferably 350 to 500 ° C. When the heating temperature is 550 ° C. or lower, the coating layer is difficult to crystallize.

The heating time is preferably 0.1 to 24 hours, more preferably 0.5 to 18 hours, and particularly preferably 1 to 12 hours. When the heating time is in the above range, the coating layer is easily formed satisfactorily.
The pressure at the time of heating is not specifically limited, Normal pressure or pressurization is preferable, and normal pressure is particularly preferable.

The coating layer is made of a compound containing the element (a), a compound containing the metal element (m), a compound containing the element (a) and the metal element (m), or a mixture thereof. The coating layer preferably contains at least a hardly soluble compound containing the element (a) and the metal element (m).
Examples of the compound containing the element (a) include a salt composed of the element (a) and an alkali metal. Examples of the salt include LiF, Li ₃ PO ₄ , Li ₂ SO ₄ , NaF, and KF.
Examples of the compound containing the metal element (m) include an oxide or hydroxide of the metal element (m). Examples of the oxide include Al ₂ O ₃ and ZrO ₂ . Examples of the hydroxide include Al (OH) ₃ and Zr (OH) ₄ .
Specific examples of the compound containing the element (a) and the metal element (m) include BaSO ₄ , CaSO ₄ , SrSO ₄ , Al ₂ (SO ₄ ) ₃ , Zr (SO ₄ ) ₂ , CePO ₄ , and BiPO _4. , AlPO ₄ , LaPO ₄ , Ce ₃ (PO ₄ ) ₄ , Mg ₃ (PO ₄ ) ₂ , Ba ₃ (PO ₄ ) ₂ , Ca ₃ (PO ₄ ) ₂ , Zr ₃ (PO ₄ ) ₂ , Li ₃ PO ₄ , Nb ₃ (PO ₄ ) ₅ , LiF, SrF ₂ , BaF ₂ , CaF ₂ , MgF ₂ , LaF ₃ , AlF ₃ , CeF ₃ , InF ₃ , ZrF ₄ , NbF _{5 and the} like. Among these, Al ₂ (SO ₄ ) ₃ , AlPO ₄ , AlF ₃ , Zr (SO ₄ ) ₂ , or ZrF ₄ is preferable, Al ₂ (SO ₄ ) ₃ or AlF ₃ is more preferable, and AlF ₃ Is particularly preferred.

<Method for producing positive electrode for lithium ion secondary battery>
The method for producing a positive electrode for a lithium ion secondary battery in the present invention (hereinafter referred to as the method for producing the present positive electrode) comprises the above-described production method and a positive electrode active material layer containing the obtained positive electrode active material, binder and conductive material. Forming on the positive electrode current collector.
The step of forming the positive electrode active material layer can be performed using a known method. For example, first, a positive electrode active material, a conductive material, and a binder are dissolved or dispersed in a medium to obtain a slurry, or a positive electrode active material, a conductive material, and a binder are kneaded with a medium to obtain a kneaded product. Next, the positive electrode active material layer can be formed by coating the obtained slurry on the positive electrode current collector (positive electrode surface) or rolling the kneaded product on the positive electrode current collector (positive electrode surface).

Examples of the conductive material include carbon black such as acetylene black, graphite, and ketjen black. One type of conductive material may be used, or two or more types may be used.
Examples of the binder include a fluorine resin, a polyolefin, a polymer having an unsaturated bond, and an acrylic acid polymer. Examples of the fluororesin include polyvinylidene fluoride and polytetrafluoroethylene. Examples of the polyolefin include polyethylene and polypropylene. Examples of the polymer having an unsaturated bond include styrene / butadiene rubber, isoprene rubber, and butadiene rubber.
Examples of the positive electrode current collector include an aluminum foil or an aluminum alloy foil.

<Method for producing lithium ion secondary battery>
The method for producing a lithium ion secondary battery in the present invention comprises a lithium ion secondary battery using the above-described method for producing the positive electrode and the obtained positive electrode for a lithium ion secondary battery, a negative electrode, a nonaqueous electrolyte, and a separator. The process of carrying out.
The process which comprises a lithium ion secondary battery can be performed using a well-known method.

[Negative electrode]
The negative electrode is obtained by forming a negative electrode active material layer containing a negative electrode active material on a negative electrode current collector. For example, a slurry can be prepared by kneading a negative electrode active material with an organic solvent, and the prepared slurry can be applied to a negative electrode current collector, dried, and pressed.
As the negative electrode current collector, for example, nickel foil, copper foil or the like can be used.
The negative electrode active material may be any material that can occlude and release lithium ions at a relatively low potential. For example, a lithium metal, a lithium alloy, a carbon material, an oxide mainly composed of a metal of periodic table 14 or 15, Carbon compounds, silicon carbide compounds, silicon oxide compounds, titanium sulfide, boron carbide compounds, and the like can be used.

Carbon materials used for the negative electrode active material include non-graphitizable carbon, artificial graphite, natural graphite, pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon And carbon blacks. Examples of the cokes include pitch coke, needle coke, and petroleum coke. Examples of the fired organic polymer compound include those obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature.
Examples of the metal of Group 14 of the periodic table include Si and Sn. Among these, Si is preferable as the metal of Group 14 of the periodic table.

  Examples of the nonaqueous electrolyte include a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in an organic solvent, an inorganic solid electrolyte, and a solid or gel polymer electrolyte in which an electrolyte salt is mixed or dissolved.

  As the organic solvent, those known as organic solvents for non-aqueous electrolytes can be employed. For example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, acetate ester, butyrate ester, propion Acid ester etc. are mentioned. Among these, from the viewpoint of voltage stability, the organic solvent is preferably a cyclic carbonate such as propylene carbonate, or a chain carbonate such as dimethyl carbonate or diethyl carbonate. One organic solvent may be used, or two or more organic solvents may be used.

Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide.
Examples of the polymer compound used in the solid polymer electrolyte in which the electrolyte salt is mixed or dissolved include polyethylene oxide, polypropylene oxide, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, polyhexafluoropropylene, And their derivatives, mixtures, and complexes.
Examples of the polymer compound used in the gel polymer electrolyte in which the electrolyte salt is mixed or dissolved include a fluorine polymer compound, polyacrylonitrile, a copolymer of polyacrylonitrile, polyethylene oxide, a copolymer of polyethylene oxide, and the like. Can be mentioned. Examples of the fluorine-based polymer compound include poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene).
The matrix of the gel electrolyte is preferably a fluorine-based polymer compound from the viewpoint of stability against redox reaction.

As the electrolyte salt, known ones used in lithium ion secondary batteries can be used, and examples thereof include LiClO ₄ , LiPF ₆ , LiBF ₄ , CF ₃ SO ₃ Li, and the like.
Examples of the separator include a film made of a microporous polyolefin film typified by polyethylene and polypropylene, polyvinylidene fluoride, and a hexafluoropropylene copolymer.

  The shape of the lithium ion secondary battery is not particularly limited, and shapes such as a coin shape, a sheet shape (film shape), a folded shape, a wound type bottomed cylindrical shape, and a button shape can be appropriately selected according to the application.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to an Example.
Examples 1 to 5 are examples of the present invention, and examples 6 and 7 are comparative examples.
(Synthesis of lithium-containing composite oxide)
In Examples 1 to 7, lithium-containing composite oxides were produced by the carbonate coprecipitation method.
1152 g of distilled water was added to a mixture of 122 g of nickel (II) sulfate hexahydrate, 130 g of cobalt (II) sulfate heptahydrate, and 446 g of manganese (II) sulfate pentahydrate, and the metal in which these compounds were uniformly dissolved An aqueous salt solution was obtained. Distilled water (401 g) was added to 99 g of ammonium sulfate and dissolved uniformly to obtain an aqueous ammonium sulfate solution. Distilled water (1850 g) was added to sodium carbonate (350 g) and dissolved uniformly to obtain a carbonate aqueous solution. 1900 g of distilled water was added to 1 g of sodium carbonate and dissolved uniformly to obtain a mother liquor.
Next, the mother liquor was placed in a 2 L baffled glass reaction vessel and heated to 50 ° C. with a mantle heater, and the aqueous solution of metal salt was added to the reaction vessel while stirring the solution in the reaction vessel with a two-stage inclined paddle type stirring blade. An aqueous ammonium sulfate solution was added at a rate of 0 g / min at a rate of 0.5 g / min over 6 hours to obtain a coprecipitate containing Ni, Co, and Mn.
During the addition of the aqueous metal salt solution, the aqueous carbonate solution was added so as to keep the pH in the reaction vessel at 8.0. Further, nitrogen gas was flowed into the reaction vessel at a flow rate of 0.5 L / min so that the deposited transition metal carbonate was not oxidized.
The obtained coprecipitate was repeatedly subjected to pressure filtration and dispersion in distilled water to remove impurity ions. When the electrical conductivity of the filtrate became less than 100 μS / cm, the washing was finished and dried at 120 ° C. for 15 hours.
When the total content of transition metals contained in the coprecipitate after washing and drying was determined by back titration with a ZINCON indicator, EDTA and an aqueous zinc chloride solution, it was 8.36 mol / kg.

Next, 300 g of the coprecipitate and 139.5 g of lithium carbonate having a lithium content of 26.96 mol / kg are mixed and fired at 880 ° C. for 16 hours in an oxygen-containing atmosphere to obtain a lithium-containing composite oxide (I ) Was obtained.
The amounts of Li, Ni, Co, and Mn contained in the lithium-containing composite oxide (I) were measured by inductively coupled plasma spectroscopy (ICP). The molar ratio of Li: Ni: Co: Mn was 1.5: 0.16: 0.17: 0.67. The composition of the lithium-containing composite oxide (I) can be expressed as Li (Li _0.20 Ni _0.128 Co _0.136 Mn _0.536 ) O ₂ . The average particle diameter D50 of this lithium-containing composite oxide (I) was 10.8 μm.
XRD measurement using CuKα rays as an X-ray source was performed on the lithium-containing composite oxide (I). From the XRD measurement, it was confirmed that the lithium-containing composite oxide (I) has a layered rock salt type crystal structure (space group R-3m), and the peak of the layered Li ₂ MnO ₃ is in the range of 2θ = 20 to 25 °. Observed.
For the XRD measurement, the product name RINT-TTR-III manufactured by Rigaku Corporation was used. The measurement conditions were as follows: voltage 50 kV, tube current 300 mA, scan axis 2θ / θ, measurement range θ = 10 to 90 °, sampling width 0.04 °, scan speed 1 ° / min.

(Example 1)
[Step (I)]
A strongly acidic cation exchange resin (product name: Diaion SK1BH, manufactured by Mitsubishi Chemical Co., Ltd., total ion exchange capacity 2.0 meq / mL-water wet resin, particle diameter 0.3 to 1.18 mm) 25 mL was added and dispersed to obtain a dispersion. Further, 50 g of the lithium-containing composite oxide (I) was added to the dispersion and stirred for 3 minutes using a stirring blade. Next, the stirring blade was taken out, the plastic container was covered, and the mixture was mixed for 24 hours at a rotation speed of 20 rpm using a roller mixer. Mixing was performed at room temperature (25 ° C.).
The relative amount (Xi) of the ion exchange capacity of the ion exchange resin calculated by the formula (5) was 0.07.
Next, the ion-exchange resin is separated with a coarse sieve having an opening width of 300 μm, the remaining slurry containing the lithium-containing composite oxide is dried at 80 ° C. for 15 hours, and the lithium-containing composite treated with the cation exchange resin is obtained. Oxide (II) was obtained.

[Step (II)]
To 4.2 g of basic aluminum lactate aqueous solution whose Al content relative to the aqueous solution is 8.8% by mass ratio in terms of Al ₂ O ₃ , 5.8 g of distilled water is added and mixed, and the aqueous solution of aluminum lactate (composition (2 )) Was prepared. The metal element (m) content (Al equivalent concentration) relative to the mass of the aluminum lactate aqueous solution (composition (2)) was 3.7%.
8.38 g of distilled water was added to 1.62 g of ammonium fluoride (NH ₄ F) and mixed to prepare an aqueous ammonium fluoride solution (composition (1)). The F content relative to the aqueous ammonium fluoride solution (composition (1)) was 8.3% in terms of mass ratio in terms of anion (A).
While stirring 8 g of the lithium-containing composite oxide (II) obtained in the step (I), 0.64 g of the aqueous aluminum lactate solution (composition (2)) was sprayed by a spray coating method to obtain a lithium-containing composite oxide. (II) and the aqueous aluminum lactate solution were brought into contact with mixing. Next, 0.64 g of an ammonium fluoride aqueous solution (composition (1)) is sprayed by a spray coating method, and the lithium-containing composite oxide (II), the aluminum lactate aqueous solution and the ammonium fluoride aqueous solution are mixed and brought into contact with each other. Got.
In this step, the amount of the composition (1) brought into contact with the lithium-containing composite oxide (II) is such that the relative amount (Xa) of the anion (A) obtained by the formula (6) is 0.038. It is.
The amount of the composition (2) brought into contact with the lithium-containing composite oxide (II) is such that the relative amount (Xm) of the metal element (m) obtained by the formula (7) is 0.019. The valence of the metal element Al used in this example is +3.

[Step (III)]
The obtained mixture is dried at 80 ° C. for 4 hours and then heated at 450 ° C. for 5 hours in an oxygen-containing atmosphere, and consists of particles having a coating layer containing Al and F on a part of the surface of the lithium-containing composite oxide particles. A positive electrode active material was obtained.

(Example 2)
In Example 1, the spray amount of the aqueous ammonium fluoride solution was changed to 1.28 g, and the relative amount (Xa) of the anion (A) was set to 0.057. Otherwise, in the same manner as in Example 1, a positive electrode active material composed of particles having a coating layer containing Al and F on a part of the surface of the lithium-containing composite oxide particles was obtained.

(Example 3)
In Example 1, the aqueous ammonium fluoride solution was not sprayed. Otherwise, in the same manner as in Example 1, a positive electrode active material composed of particles having a coating layer containing Al on a part of the surface of the lithium-containing composite oxide particles was obtained.

(Example 4)
In Example 1, step (II) and step (III) were not performed. Otherwise, in the same manner as in Example 1, a positive electrode active material having no coating layer on the surface of the lithium-containing composite oxide was obtained.

(Example 5)
[Step (I)]
Weakly acidic cation exchange resin (product name: Diaion WK40L, manufactured by Mitsubishi Chemical Co., Ltd., total ion exchange capacity 4.4 meq / mL-water wet resin, particle size 0.3 to 35 mL in 50 mL distilled water in a 50 mL plastic container 1.18 mm) 5 mL was added and dispersed to obtain a dispersion. Further, 10 g of the lithium-containing composite oxide (I) was added to the dispersion and stirred for 3 minutes using a stirrer. Next, the stirrer chip was taken out, the plastic container was covered, and mixed for 24 hours at a rotation speed of 20 rpm using a roller mixer. Mixing was performed at room temperature (25 ° C.).
The relative amount (Xi) of the ion exchange capacity of the ion exchange resin calculated by the formula (5) was 0.16.
Next, the ion exchange resin is separated with a coarse sieve having an opening width of 300 μm, and the slurry containing the remaining lithium-containing composite oxide is dried at 80 ° C. for 15 hours, and the lithium-containing composite oxidation treated with the cation exchange resin is performed. The product (II) was obtained.
Process (II) and process (III) were carried out similarly to Example 1, and obtained the positive electrode active material which consists of particle | grains which have a coating layer containing Al and F in a part of surface of lithium containing complex oxide particle.

(Example 6)
In Example 1, the step (I) was not performed, and the lithium-containing composite oxide (I) was used in the step (II). Process (II) and process (III) were carried out similarly to Example 1, and obtained the positive electrode active material which consists of particle | grains which have a coating layer containing Al and F in a part of surface of lithium containing complex oxide particle.
(Example 7)
In Example 1, the step (I) was not performed, and the aqueous ammonium fluoride solution (composition (1)) was not spray-coated in the step (II). Otherwise, in the same manner as in Example 1, a positive electrode active material composed of particles having a coating layer containing Al on a part of the surface of the lithium-containing composite oxide particles was obtained.

  The main conditions of the process (I) in the said Examples 1-7 are shown in Table 1, and the main conditions of the process (II) are shown in Table 2.

[Production of positive electrode sheet]
The positive electrode active materials obtained in Examples 1 to 7, acetylene black (conductive material), and a solution containing 12.0% by mass of polyvinylidene fluoride (binder) (solvent N-methylpyrrolidone) were mixed, and further, N -Methylpyrrolidone was added to prepare a slurry. At this time, the positive electrode active material, acetylene black, and polyvinylidene fluoride were in a mass ratio of 80:10:10.
Subsequently, this slurry was applied on one side to a 20 μm thick aluminum foil (positive electrode current collector) using a doctor blade. The gap of the doctor blade was adjusted so that the sheet thickness after rolling was 30 μm. After drying this at 120 degreeC, roll press rolling was performed twice and the positive electrode body sheet | seat was produced.

  As Reference Example 1, a lithium-containing composite oxide (I) was used as a positive electrode active material, and a positive electrode sheet was produced in the same manner as described above.

[Manufacture of lithium secondary batteries]
Using the positive electrode sheet obtained above as a positive electrode, a stainless steel simple sealed cell type lithium secondary battery was assembled in an argon glove box.
A metal lithium foil having a thickness of 500 μm was used for the negative electrode, a stainless steel plate having a thickness of 1 mm was used for the negative electrode current collector, and a porous polypropylene having a thickness of 25 μm was used for the separator. Furthermore, a LiPF ₆ solution having a concentration of 1 mol / dm ³ was used as the electrolytic solution. As a solvent for the electrolytic solution, a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1 was used.

[Evaluation of lithium secondary battery]
The following evaluation was performed about the lithium secondary battery manufactured above. The evaluation results are shown in Table 3.
(Initial efficiency)
The positive electrode active material was charged to 4.6 V with a load current of 20 mA per 1 g of the positive electrode active material, and discharged to 2.0 V with a load current of 20 mA per 1 g of the positive electrode active material. The charge capacity, discharge capacity, and charge / discharge efficiency at this time were defined as initial charge capacity, initial discharge capacity, and initial efficiency, respectively.

(Cycle characteristics)
Next, a charge / discharge cycle of charging to 4.6 V with a load current of 200 mA per 1 g of the positive electrode active material and discharging at a high rate to 2.0 V with a load current of 200 mA per 1 g of the positive electrode active material was repeated 50 times. At this time, the discharge capacity at the second cycle was defined as the cycle initial capacity, and the value obtained by dividing the discharge capacity at the 50th cycle by the cycle initial capacity was calculated, and this value was defined as the cycle maintenance ratio.

  From the results of Table 3, Example 4 in which the contact with the dispersion (step (I)) was performed and the coating (steps (II) and (III)) was not carried out was performed in both the contact with the dispersion and the coating. Compared to Reference Example 1 that was not performed, initial charge / discharge efficiency (initial efficiency), initial discharge capacity, and cycle initial capacity were improved. This shows that the initial efficiency, the initial discharge capacity, and the cycle initial capacity can be improved by bringing the lithium-containing composite oxide (I) into contact with a dispersion containing a cation exchange resin.

In addition to contact with the dispersion (step (I)), Examples 1 to 3 and 5 in which coating (steps (II) and (III)) was performed had an initial efficiency, an initial discharge capacity, And the cycle maintenance rate improved.
In Example 3, in which only the composition (2) was used in the step (II), the initial efficiency was almost the same as the example 4 in which only the step (I) was performed, and the cycle retention rate was improved. From this, it can be seen that the coating with the composition (2) contributes to the improvement of the cycle retention rate.

Example 1 and Example 3 in which coating (steps (II) and (III)) was performed in addition to contact with the dispersion (step (I)) did not perform contact with the dispersion (step (I)). The initial efficiency, the initial discharge capacity, and the cycle initial capacity were improved as compared with Examples 6 and 7 in which coating (steps (II) and (III)) was performed.
In addition to the contact with the dispersion (step (I)), coating (steps (II) and (III)) is performed, and in step (II), the lithium-containing composite oxide is converted into the composition (1) and the composition. In Example 1 and Example 5 that are in contact with both of (2), the cycle retention rate is particularly high.

Claims (9)

  Lithium-containing composite oxide (I) containing Li and a transition metal element is brought into contact with a dispersion containing a cation exchange resin, and after the contact, the cation exchange resin is separated to obtain lithium-containing composite oxide (II). The manufacturing method of the positive electrode active material for lithium ion secondary batteries which has a process. 2. The lithium ion secondary according to claim 1, wherein the relative amount (Xi) of the ion exchange capacity determined by the lower formula (5) of the dispersion containing the cation exchange resin is 0.003 to 0.20. A method for producing a positive electrode active material for a battery.
Relative amount of ion exchange capacity (Xi) = f1 × f2 / f0 (5)
However, f0-f2 in Formula (5) is as follows.
f0: Total amount of lithium element contained in the lithium-containing composite oxide (I) (unit: mole)
f1: Total ion exchange capacity of the cation exchange resin in a water wet state (unit: milliequivalent / mL)
f2: Amount of cation exchange resin contained in the dispersion (unit: mL) A step of bringing the lithium-containing composite oxide (II) into contact with at least one of the following composition (1) and composition (2); and a step of heating the lithium-containing composite oxide (II) after the contact The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 1 or 2.
Composition (1): An aqueous solution containing an anion (A) containing at least one element (a) selected from the group consisting of S, P, F, and B.
Composition (2): Li, Mg, Ca, Sr, Ba, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Al, An aqueous solution containing a cation (M) of at least one metal element (m) selected from the group consisting of Ga, In, Sn, Sb, Bi, La, Ce, Pr, Nd, Gd, Dy, Er, and Yb . The lithium-containing composite oxide (II) is in contact with the composition (1), and the relative amount (Xa) of the anion (A) obtained by the following formula (6) in the composition (1) is 0.001. It is -0.15. The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 3.
Relative amount of anion (A) (Xa) = Σ (f4 × f5) / f3 (6)
However, f3-f5 in Formula (6) are as follows.
f3: Total amount of transition metal element contained in lithium-containing composite oxide (I) (unit: mole)
f4: amount of each anion (A) contained in the composition (1) (unit: mole)
f5: Valence of each anion (A) The lithium-containing composite oxide (II) is in contact with the composition (2), and the relative amount (Xm) of the cation (M) obtained by the following formula (7) in the composition (2) is 0.001 to 0.001. It is 0.15, The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 3 or 4.
Relative amount of metal element (m) (Xm) = Σ (f6 × f7) / f3 (7)
However, f3, f6, and f7 in Formula (7) are as follows.
f3: Total amount of transition metal element contained in lithium-containing composite oxide (I) (unit: mole)
f6: amount of each cation (M) contained in the composition (2) (unit: mole)
f7: Valence of each cation (M)   The heating temperature in the step of heating the lithium-containing composite oxide (II) after contact with at least one of the composition (1) and the composition (2) is 250 to 700 ° C. The manufacturing method of the positive electrode active material for lithium ion secondary batteries of 1 item | term.   The lithium-containing composite oxide (I) contains at least one transition metal element selected from the group consisting of Ni, Co, and Mn, and Li, and the molar amount of Li is the total molar amount of the transition metal elements. The manufacturing method of the positive electrode active material for lithium ion secondary batteries of any one of Claims 1-6 which is more than 1.2 times with respect to. The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 7 whose lithium containing complex oxide (I) is a compound represented by the following Formula (1).
Li (Li _x1 Mn _y1 Me _z1 ) Me ′ _α O _p F _q (1)
However, Me is at least one element selected from the group consisting of Co and Ni, and Me ′ is at least one element selected from the group consisting of Al, Cr, Mg, Mo, Ru, Ti, Zr, and Fe. 0.1 <x1 <0.25, 0.5 ≦ y1 / (y1 + z1) ≦ 0.8, 0 ≦ α ≦ 0.1, x1 + y1 + z1 = 1, 1.9 <p <2.1, 0 ≦ q ≦ 0.1.   A process for producing a positive electrode active material for a lithium ion secondary battery by the production method according to claim 1, and a positive electrode active material comprising the positive electrode active material for a lithium ion secondary battery, a binder, and a conductive material. The manufacturing method of the positive electrode for lithium ion secondary batteries which has the process of forming a substance layer on a positive electrode electrical power collector.