JP2018063853A - Method for manufacturing positive electrode active material for lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a positive electrode active material for a lithium secondary battery, which is superior in crystallinity.SOLUTION: A method for manufacturing a positive electrode active material for a lithium secondary battery comprises: a mixing step of mixing a lithium compound with a positive electrode active material precursor into a mixture; and a primary baking step of baking the mixture by a rotary kiln. In the mixture, the content of the lithium compound is over 0 up to 50 mass%. The rotary kiln has a furnace inner wall comprising a non-metal material.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a positive electrode active material for a lithium secondary battery.

  Lithium composite oxide is used for the positive electrode active material for lithium secondary batteries. Lithium secondary batteries have already been put into practical use not only for small power sources for mobile phones and laptop computers, but also for medium and large power sources for automobiles and power storage.

A method for producing a positive electrode active material for a lithium secondary battery generally includes a step of firing a lithium compound and a precursor that is a metal composite oxide.
In order to improve the performance of the lithium secondary battery such as cycle characteristics, attempts have been made to make the composition of the positive electrode active material for the lithium secondary battery uniform and to reduce the remaining amount of unreacted substances.
For example, Patent Document 1 describes that a positive electrode material with little variation in oxidation could be manufactured with high productivity by performing the firing process using a roller hearth kiln.

JP 2006-4724 A

As the application field of lithium secondary batteries is expanding, positive electrode active materials for lithium secondary batteries are required to have high crystallinity in order to improve various battery characteristics.
However, as described in Patent Document 1, when a roller hearth kiln is used, firing takes a long time and the crystallinity is not sufficient.
This invention is made | formed in view of the said situation, Comprising: It aims at providing the manufacturing method of the positive electrode active material for lithium secondary batteries which is excellent in crystallinity.

That is, the present invention includes the following [1] to [8].
[1] Production of a positive electrode active material for a lithium secondary battery, comprising: a mixing step of mixing a lithium compound and a positive electrode active material precursor to obtain a mixture; and a main baking step of baking the mixture using a rotary kiln. A positive electrode for a lithium secondary battery, characterized in that the content of the lithium compound contained in the mixture is more than 0 and 50% by mass or less, and the inner wall of the rotary kiln is made of a non-metallic material. A method for producing an active material.
[2] The method for producing a positive electrode active material for a lithium secondary battery according to [1], wherein the main firing step is performed at 750 ° C. or higher and 1000 ° C. or lower.
[3] The method for producing a positive electrode active material for a lithium secondary battery according to [1] or [2], wherein the positive electrode active material for a lithium secondary battery is represented by the following general formula (I).
_{Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 ··· (I)
(In the general formula (I), −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.5, 0 <z ≦ 0.8, 0 ≦ w ≦ 0.1, y + z + w <1, M is (It represents one or more metals selected from the group consisting of Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, and V.)
[4] Any one of [1] to [3] including a pre-baking step after the mixing step and before the main baking step, including baking at a temperature lower than the heating temperature of the main baking. The manufacturing method of the positive electrode active material for lithium secondary batteries as described in an item.
[5] Any one or both of the main firing step and the preliminary firing step are performed by ventilating an oxygen-containing gas at a flow rate of 15 Nm ³ / h / m ³ or more. 2. A method for producing a positive electrode active material for a lithium secondary battery according to item 1.
[6] The method for producing a positive electrode active material for a lithium secondary battery according to [5], wherein the oxygen concentration in the oxygen gas is 21% by volume or more.
[7] The positive electrode active material for a lithium secondary battery according to any one of [1] to [6], wherein a content of chromium contained in the positive electrode active material for a lithium secondary battery is 50 ppm or less. Production method.
[8] The lithium secondary battery according to any one of [1] to [7], wherein a content of lithium carbonate contained in the positive electrode active material for a lithium secondary battery is 1.0% by mass or less. For producing a positive electrode active material for use.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the positive electrode active material for lithium secondary batteries which is excellent in crystallinity can be provided.

It is a schematic block diagram which shows an example of a lithium ion secondary battery.

<Method for producing positive electrode active material for lithium secondary battery>
The manufacturing method of the positive electrode active material for lithium secondary batteries of the present invention (hereinafter referred to as “positive electrode active material”) includes a lithium compound and a positive electrode active material precursor (hereinafter referred to as “precursor”). And a main firing step in which the mixture is fired using a rotary kiln, and a method for producing a positive electrode active material for a lithium secondary battery, comprising: a lithium compound contained in the mixture The content of is more than 0 and 50% by mass or less, and the inner wall of the rotary kiln is made of a non-metallic material.

Conventionally, facilities such as a tunnel furnace, a roller hearth kiln, and a rotary kiln are used for the firing process of the lithium compound and the precursor.
Tunnel furnaces and roller hearth kilns have a problem that the mixture is filled in the sheath and fired, so that the firing efficiency is low and further firing takes a long time.
Further, the rotary kiln has a problem that the inner wall of the furnace is made of metal, and the metal is eluted from the member when fired at a high temperature, and the positive electrode active material is contaminated by the eluted metal component.

In the present invention, the firing step of the mixture of the lithium compound and the precursor is carried out using a rotary kiln in which the furnace inner wall, which is the part in contact with the mixture, is a non-metallic material. For this reason, even if it is a case where it bakes at high temperature, a metal does not elute from a furnace inner wall and a positive electrode active material is not contaminated. Moreover, since this invention bakes the mixture whose content of a lithium compound is 50 mass% or less, even if it bakes at high temperature, it can bake, without a mixture and baking products adhering too much to a rotary kiln.
Hereinafter, the manufacturing method of the positive electrode active material for lithium secondary batteries of this invention is demonstrated.

[Mixing process]
This step is a step of mixing the lithium compound and the precursor to obtain a mixture.
In this step, mixing is performed so that the content of the lithium compound in the mixture of the lithium compound and the precursor is more than 0 and 50% by mass or less.
10 mass% or more is preferable, as for the lower limit of content of a lithium compound, 15 mass% or more is more preferable, and 20 mass% or more is especially preferable.
The upper limit of the lithium compound content is preferably 49% by mass or less, more preferably 48% by mass or less, and particularly preferably 47% by mass or less.
The upper limit value and the lower limit value can be arbitrarily combined.

  In the present invention, by setting the content of the lithium compound in the mixture to the specific content described above, adhesion of the mixture and the fired product to the inner wall of the rotary kiln can be reduced. For this reason, in the baking process mentioned later, it can bake at high temperature and can obtain the positive electrode active material with high crystallinity.

-Lithium compound The lithium compound used for this invention is demonstrated.
The lithium compound used in the present invention is not particularly limited, and any one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, or a mixture of two or more thereof. Can be used. In these, any one or both of lithium hydroxide and lithium carbonate are preferable.

-Precursor The precursor is preferably a transition metal compound. The precursor is a group consisting of metals other than lithium, that is, essential metals Ni, Co, Mn, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, and V. It is preferable that it is a transition metal compound containing 1 or more types of arbitrary metals chosen from these. The transition metal compound is preferably a transition metal hydroxide or a transition metal oxide, and specifically, nickel cobalt manganese composite hydroxide or nickel cobalt manganese composite oxide is preferable.
The precursor can be produced by a generally known batch method or coprecipitation method.

[Main firing process]
In the present invention, by using the above specific mixing conditions, firing can be performed at a high temperature in the firing step, and the development of crystals can be favorably progressed.
The main firing step is performed by a rotary kiln in which the furnace inner wall which is a contact portion with the mixture is a non-metallic material.
Non-metallic materials include silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ; also referred to as alumina), silicon dioxide (SiO ₂ ), zirconium dioxide (ZrO ₂ ), magnesium oxide (MgO), silicon carbide. A ceramic material such as (SiC) is preferred, and aluminum oxide is particularly preferably contained in an amount of 50% by weight or more.

It is preferable to perform this baking process at 750 degreeC or more and 1000 degrees C or less.
By setting the firing temperature to a high temperature range of 750 ° C. or higher and 1000 ° C. or lower, a positive electrode active material with high crystallinity can be produced.

[Pre-baking step]
In the present invention, it is preferable to include a pre-baking step of baking at a temperature lower than the heating temperature of the main baking after the mixing step and before the main baking step. The pre-firing may be performed at a temperature lower than that of the main calcination, and is preferably a temperature lower by 80 ° C. to 200 ° C. than the calcination temperature of the main calcination, and is preferably a temperature lower by 100 ° C. to 150 ° C.
By performing preliminary firing, a positive electrode active material having high crystallinity can be obtained, and unreacted materials can be reduced.
The firing furnace in the preliminary firing step is not particularly limited, but it is preferable to use a rotary kiln. The main firing step and the preliminary firing step may be the same rotary kiln or different rotary kilns, but are preferably performed using the same rotary kiln from the viewpoint of performing the firing step continuously.
The contact part with the said mixture of the baking furnace used for a preliminary baking process may be metal materials, such as Inconel, such as silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ; also referred to as alumina), etc. A non-metallic material may be used.

Wherein one or both of the sintering step and the calcination step is preferably conducted by passing an oxygen-containing gas at 15Nm ³ / h / ^{m 3} or more ^flow, is 16Nm ³ / h / ^m 3 or more More preferred. The upper limit value is not particularly limited, for example, 150Nm ³ / h / ^{m 3} or less, 130Nm ³ / h / ^{m 3} or less include 120Nm ³ / h / ^{m 3} or less.
The upper limit value and the lower limit value can be arbitrarily combined.
It is preferable that one or both of the main baking step and the preliminary baking step be performed with an oxygen concentration in the oxygen gas of 21% by volume or more.
In this invention, it is preferable to implement this baking process on said ventilation | gas_flowing conditions.

The firing time is preferably 1 hour or more and 10 hours or less, preferably 1 hour or more and 8 hours or less, preferably 1 hour or more and 5 hours or less. Particularly preferred.
More specifically, the pre-baking step is preferably 30 minutes to 3 hours, more preferably 1 hour to 2.5 hours.
Moreover, it is preferable to make this baking process into 30 minutes or more and 3 hours or less, and it is more preferable to set it as 1 to 2.5 hours.
In this invention, this baking process is implemented using a nonmetallic rotary kiln.
The metal rotary kiln needs to be fired at a temperature at which metal elution does not occur. However, when a non-metal rotary kiln is used, the firing temperature can be set to a high temperature without considering metal elution. Therefore, the firing process can be performed at a higher temperature when a non-metallic rotary kiln is used than when a metallic rotary kiln is used. For this reason, a positive electrode active material with high crystallinity can be obtained in a short baking process.
In the present invention, when pre-baking is performed, the time from the start of temperature increase in the pre-baking step to the end of the main baking step is performed within the above time.

  The lithium nickel composite oxide obtained by firing is appropriately classified after pulverization, and used as a positive electrode active material for a lithium secondary battery applicable to a lithium secondary battery.

<Positive electrode active material for lithium secondary battery>
The positive electrode active material for lithium secondary batteries produced by the method for producing a positive electrode active material for lithium secondary batteries of the present invention will be described.

In order to increase the energy density of the lithium secondary battery, the positive electrode active material for the lithium secondary battery is preferably represented by the following composition formula (I).
_{Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 ··· (I)
(In the general formula (I), -0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.5, 0 <z ≦ 0.8, 0 ≦ w ≦ 0.1, y + z + w <1, M is (It represents one or more metals selected from the group consisting of Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, and V.)

In the sense of obtaining a lithium secondary battery having high cycle characteristics, x in the composition formula (I) is preferably 0 or more, more preferably 0.01 or more, and further preferably 0.02 or more. preferable. In the sense of obtaining a lithium secondary battery with higher initial Coulomb efficiency, x in the composition formula (I) is preferably 0.18 or less, more preferably 0.15 or less, More preferably, it is as follows.
The upper limit value and the lower limit value of x can be arbitrarily combined.
In the present specification, “high cycle characteristics” means that the discharge capacity retention ratio is high.

In order to obtain a lithium secondary battery having high cycle characteristics, y in the composition formula (I) is preferably 0.13 or more, and more preferably 0.14 or more. In order to obtain a lithium secondary battery having high thermal stability, y in the composition formula (I) is preferably 0.35 or less, more preferably 0.3 or less, and 0.25. More preferably, it is as follows.
The upper limit value and the lower limit value of y can be arbitrarily combined.

In the sense of obtaining a lithium secondary battery having high cycle characteristics, z in the composition formula (I) is preferably 0.1 or more, more preferably 0.15 or more, and 0.2 or more. More preferably. In addition, z in the composition formula (I) is preferably 0.35 or less, and preferably 0.32 or less in order to obtain a lithium secondary battery having high storage characteristics at a high temperature (for example, in an environment of 60 ° C.). Is more preferable, and it is further more preferable that it is 0.30 or less.
The upper limit value and lower limit value of z can be arbitrarily combined.

In the sense of enhancing the handling properties of the positive electrode active material for lithium secondary batteries, w in the composition formula (I) is preferably more than 0, more preferably 0.001 or more, and 0.005 or more. Is more preferable. In the sense of obtaining a lithium secondary battery having a high discharge capacity at a high current rate, w in the composition formula (I) is preferably 0.04 or less, more preferably 0.03 or less, More preferably, it is 0.02 or less.
The upper limit value and lower limit value of s can be arbitrarily combined.

  M in the composition formula (I) is one or more metals selected from the group consisting of Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, and V.

  In this invention, what is necessary is just to mix a lithium compound and a positive electrode active material precursor so that the positive electrode active material for lithium secondary batteries manufactured may become a desired composition represented by the said compositional formula (I).

(Layered structure)
The crystal structure of the positive electrode active material is a layered structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

The hexagonal crystal structures are P3, P3 ₁ , P3 ₂ , R3, P-3, R-3, P312, P321, P3 ₁ 12, P3 ₁ 21, P3 ₂ 12, P3 ₂ 21, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6 ₁ , P6 ₅ , P6 ₂ , P6 ₄ , P6 ₃ , P-6, P6 / m, P6 ₃ / m, P622, P6 ₁ 22, P6 ₅ 22, P6 ₂ 22, P6 ₄ 22, P6 ₃ 22, P6 mm, P6 cc, P6 ₃ cm, P6 ₃ mc, P- It belongs to any one space group selected from the group consisting of 6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P6 ₃ / mcm, and P6 ₃ / mmc.

The monoclinic crystal structure is P2, P2 ₁ , C2, Pm, Pc, Cm, Cc, P2 / m, P2 ₁ / m, C2 / m, P2 / c, P2 ₁ / c, C2 / It belongs to any one space group selected from the group consisting of c.

  Among these, in order to obtain a lithium secondary battery having a high discharge capacity, the crystal structure is a hexagonal crystal structure belonging to the space group R-3m or a monoclinic crystal belonging to C2 / m. A crystal structure is particularly preferred.

Since this invention implements this baking process using a non-metallic rotary kiln, the elution of the metal from the material of a baking furnace can be reduced. For this reason, when attention is paid to chromium which is a kind of metal impurity, a positive electrode active material in which the chromium content is reduced can be manufactured.
The content of chromium contained in the positive electrode active material for a lithium secondary battery produced according to the present invention is preferably 50 ppm or less, more preferably 45 ppm or less, and particularly preferably 40 ppm or less.

Since the manufacturing method of the positive electrode active material for lithium secondary batteries of this invention is implemented using a nonmetallic rotary kiln, it can be baked at high temperature. For this reason, decomposition | disassembly of the lithium carbonate in a raw material is accelerated | stimulated, and the residual amount of lithium carbonate in the positive electrode active material manufactured is reduced.
The content of lithium carbonate contained in the positive electrode active material for a lithium secondary battery produced according to the present invention is preferably 1.0% by mass or less, more preferably 0.99% by mass or less, and 0.95% by mass or less. Is particularly preferred. Although the lower limit of content of lithium carbonate is not specifically limited, For example, 0.05 mass% or more, 0.10 mass% or more, 0.2 mass% or more is mentioned.
The upper limit value and the lower limit value can be arbitrarily combined.

  In contrast to the present invention, when the main firing is performed by filling a sheath such as a roller hearth kiln with a mixture, the decomposition of lithium carbonate does not proceed uniformly, so that lithium carbonate is included in the produced positive electrode active material. Tend to remain.

<Lithium secondary battery>
Next, while explaining the configuration of the lithium secondary battery, the positive electrode using the positive electrode active material for lithium secondary battery manufactured by the method for manufacturing the positive electrode active material for lithium secondary battery of the present invention, and lithium having this positive electrode The secondary battery will be described.

  An example of the lithium secondary battery of the present embodiment includes a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolyte solution disposed between the positive electrode and the negative electrode.

  FIG. 1 is a schematic diagram showing an example of the lithium secondary battery of the present embodiment. The cylindrical lithium secondary battery 10 of this embodiment is manufactured as follows.

  First, as shown in FIG. 1 (a), a pair of separators 1 having a strip shape, a strip-like positive electrode 2 having a positive electrode lead 21 at one end, and a strip-like negative electrode 3 having a negative electrode lead 31 at one end, 2, separator 1, and negative electrode 3 are laminated in this order and wound to form electrode group 4.

  Next, as shown in FIG. 1B, after the electrode group 4 and an insulator (not shown) are accommodated in the battery can 5, the bottom of the can is sealed, and the electrode group 4 is impregnated with the electrolytic solution 6, An electrolyte is disposed between the negative electrode 3 and the negative electrode 3. Furthermore, the lithium secondary battery 10 can be manufactured by sealing the upper part of the battery can 5 with the top insulator 7 and the sealing body 8.

  As the shape of the electrode group 4, for example, a columnar shape in which the cross-sectional shape when the electrode group 4 is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners. Can be mentioned.

  Moreover, as a shape of the lithium secondary battery having such an electrode group 4, a shape defined by IEC 60086 or JIS C 8500, which is a standard for a battery defined by the International Electrotechnical Commission (IEC), can be adopted. . For example, cylindrical shape, square shape, etc. can be mentioned.

  Furthermore, the lithium secondary battery is not limited to the above-described wound type configuration, and may have a stacked type configuration in which a stacked structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. Examples of the stacked lithium secondary battery include so-called coin-type batteries, button-type batteries, and paper-type (or sheet-type) batteries.

Hereafter, each structure is demonstrated in order.
(Positive electrode)
The positive electrode of the present embodiment can be produced by first adjusting a positive electrode mixture containing a positive electrode active material, a conductive material and a binder, and supporting the positive electrode mixture on a positive electrode current collector.

(Conductive material)
As the conductive material included in the positive electrode of the present embodiment, a carbon material can be used. Examples of the carbon material include graphite powder, carbon black (for example, acetylene black), and a fibrous carbon material. Since carbon black is fine and has a large surface area, adding a small amount to the positive electrode mixture can improve the conductivity inside the positive electrode and improve the charge / discharge efficiency and output characteristics. Both the binding force between the positive electrode mixture and the positive electrode current collector and the binding force inside the positive electrode mixture are reduced, which causes an increase in internal resistance.

  The proportion of the conductive material in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, this ratio can be lowered.

(binder)
As the binder included in the positive electrode of the present embodiment, a thermoplastic resin can be used. Examples of the thermoplastic resin include polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. And fluororesins such as copolymers, propylene hexafluoride / vinylidene fluoride copolymers, tetrafluoroethylene / perfluorovinyl ether copolymers; polyolefin resins such as polyethylene and polypropylene.

  These thermoplastic resins may be used as a mixture of two or more. By using a fluororesin and a polyolefin resin as a binder, the ratio of the fluororesin to the whole positive electrode mixture is 1% by mass or more and 10% by mass or less, and the ratio of the polyolefin resin is 0.1% by mass or more and 2% by mass or less. A positive electrode mixture having both high adhesion to the current collector and high bonding strength inside the positive electrode mixture can be obtained.

(Positive electrode current collector)
As the positive electrode current collector included in the positive electrode of the present embodiment, a band-shaped member made of a metal material such as Al, Ni, and stainless steel can be used. Among these, a material that is made of Al and formed into a thin film is preferable because it is easy to process and inexpensive.

  Examples of the method of supporting the positive electrode mixture on the positive electrode current collector include a method of pressure-molding the positive electrode mixture on the positive electrode current collector. Also, the positive electrode mixture is made into a paste using an organic solvent, and the resulting positive electrode mixture paste is applied to at least one surface side of the positive electrode current collector, dried, pressed and fixed, whereby the positive electrode current collector is bonded to the positive electrode current collector. A mixture may be supported.

  When the positive electrode mixture is made into a paste, usable organic solvents include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; methyl acetate And amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP).

  Examples of the method of applying the positive electrode mixture paste to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method.

A positive electrode can be manufactured by the method mentioned above.
(Negative electrode)
The negative electrode included in the lithium secondary battery of this embodiment is only required to be able to dope and dedope lithium ions at a lower potential than the positive electrode, and the negative electrode mixture containing the negative electrode active material is supported on the negative electrode current collector. And an electrode made of a negative electrode active material alone.

(Negative electrode active material)
Examples of the negative electrode active material possessed by the negative electrode include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, and alloys that can be doped and dedoped with lithium ions at a lower potential than the positive electrode. It is done.

  Examples of carbon materials that can be used as the negative electrode active material include graphites such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and organic polymer compound fired bodies.

The oxide can be used as an anode active _material, (wherein, x represents a positive real number) SiO 2, SiO, etc. formula SiO _x oxides of silicon represented _by; TiO 2, TiO, etc. formula TiO _x (wherein , X is a positive real number); oxide of titanium represented by formula VO _x (where x is a positive real number) such as V ₂ O ₅ and VO ₂ ; Fe ₃ O ₄ , Fe ₂ O ₃ , FeO, etc. Iron oxide represented by the formula FeO _x (where x is a positive real number); SnO ₂ , SnO, etc. represented by the formula SnO _x (where x is a positive real number) Oxide of tin; tungsten oxide represented by general formula WO _x (where x is a positive real number) such as WO ₃ and WO ₂ ; lithium and titanium such as Li ₄ Ti ₅ O ₁₂ and LiVO ₂ Or a composite metal oxide containing vanadium; It is possible.

Examples of sulfides that can be used as the negative electrode active material include titanium sulfides represented by the formula TiS _x (where x is a positive real number) such as Ti ₂ S ₃ , TiS ₂ , and TiS; V ₃ S ₄ , VS _2, VS and other vanadium sulfides represented by the formula VS _x (where x is a positive real number); Fe ₃ S ₄ , FeS ₂ , FeS and other formulas FeS _x (where x is a positive real number) Iron sulfide represented; Mo ₂ S ₃ , MoS _{2 and the} like MoS _x (where x is a positive real number) Molybdenum sulfide; SnS _2, SnS and other formula SnS _x (where, a sulfide of tin represented by x is a positive real number; a sulfide of tungsten represented by a formula WS _x (where x is a positive real number) such as WS ₂ ; a formula SbS _x such as Sb ₂ S ₃ (here And x is a positive real number) antimony sulfide; Se ₅ S ₃ , selenium sulfide represented by the formula SeS _x (where x is a positive real number) such as SeS ₂ and SeS.

Examples of the nitride that can be used as the negative electrode active material include Li ₃ N and Li _3-x A _x N (where A is one or both of Ni and Co, and 0 <x <3). And lithium-containing nitrides.

  These carbon materials, oxides, sulfides and nitrides may be used alone or in combination of two or more. These carbon materials, oxides, sulfides and nitrides may be crystalline or amorphous.

  Examples of the metal that can be used as the negative electrode active material include lithium metal, silicon metal, and tin metal.

Examples of alloys that can be used as the negative electrode active material include lithium alloys such as Li—Al, Li—Ni, Li—Si, Li—Sn, and Li—Sn—Ni; silicon alloys such as Si—Zn; Sn—Mn and Sn. It can also be mentioned; -Co, Sn-Ni, Sn -Cu, tin alloys such as _Sn-La; Cu 2 _Sb, alloys such as La 3 _Ni 2 Sn _7.

  These metals and alloys are mainly used alone as electrodes after being processed into a foil shape, for example.

  Among the negative electrode active materials, the potential of the negative electrode hardly changes from the uncharged state to the fully charged state at the time of charging (potential flatness is good), the average discharge potential is low, and the capacity retention rate when repeatedly charged and discharged is For reasons such as high (good cycle characteristics), carbon materials containing graphite as a main component, such as natural graphite and artificial graphite, are preferably used. The shape of the carbon material may be any of a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.

  The negative electrode mixture may contain a binder as necessary. Examples of the binder include thermoplastic resins, and specific examples include PVdF, thermoplastic polyimide, carboxymethyl cellulose, polyethylene, and polypropylene.

(Negative electrode current collector)
Examples of the negative electrode current collector of the negative electrode include a band-shaped member made of a metal material such as Cu, Ni, and stainless steel. In particular, it is preferable to use Cu as a forming material and process it into a thin film from the viewpoint that it is difficult to make an alloy with lithium and it is easy to process.

  As a method of supporting the negative electrode mixture on such a negative electrode current collector, as in the case of the positive electrode, a method using pressure molding, pasting with a solvent, etc., applying to the negative electrode current collector, drying and pressing. The method of crimping is mentioned.

(Separator)
Examples of the separator included in the lithium secondary battery of the present embodiment include a porous film, a nonwoven fabric, a woven fabric, and the like made of a material such as a polyolefin resin such as polyethylene and polypropylene, a fluororesin, and a nitrogen-containing aromatic polymer. A material having the following can be used. Moreover, a separator may be formed by using two or more of these materials, or a separator may be formed by laminating these materials.

  In the present embodiment, the separator allows the electrolyte to permeate well when the battery is used (during charging / discharging). Therefore, the air resistance according to the Gurley method defined in JIS P 8117 is 50 seconds / 100 cc or more, 300 seconds / 100 cc. Or less, more preferably 50 seconds / 100 cc or more and 200 seconds / 100 cc or less.

  Moreover, the porosity of the separator is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less. The separator may be a laminate of separators having different porosity.

(Electrolyte)
The electrolyte solution included in the lithium secondary battery of this embodiment contains an electrolyte and an organic solvent.

The electrolyte contained in the electrolyte includes LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (COCF ₃ ), Li (C ₄ F ₉ SO ₃ ), LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (where BOB is bis (oxalato) borate LiFSI (here, FSI is bis (fluorosulfonyl) imide), lithium salt such as lower aliphatic carboxylic acid lithium salt, LiAlCl _4, and a mixture of two or more of these May be used. Among them, the electrolyte is at least selected from the group consisting of LiPF ₆ containing fluorine, LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) _3. It is preferable to use one containing one kind.

  Examples of the organic solvent contained in the electrolyte include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, and 1,2-di- Carbonates such as (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2- Ethers such as methyltetrahydrofuran; Esters such as methyl formate, methyl acetate and γ-butyrolactone; Nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethylacetate Amides such as amides; carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone, or those obtained by further introducing a fluoro group into these organic solvents ( One obtained by substituting one or more hydrogen atoms in the organic solvent with fluorine atoms can be used.

  As the organic solvent, it is preferable to use a mixture of two or more of these. Among them, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate and a mixed solvent of cyclic carbonate and ether are more preferable. As a mixed solvent of cyclic carbonate and acyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable. The electrolyte using such a mixed solvent has a wide operating temperature range, hardly deteriorates even when charged and discharged at a high current rate, hardly deteriorates even when used for a long time, and natural graphite as an active material of the negative electrode. Even when a graphite material such as artificial graphite is used, it has many features that it is hardly decomposable.

Further, as the electrolytic solution, it is preferable to use an electrolytic solution containing a lithium salt containing fluorine such as LiPF ₆ and an organic solvent having a fluorine substituent because the safety of the obtained lithium secondary battery is increased. A mixed solvent containing dimethyl carbonate and ethers having fluorine substituents such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether is capable of capacity even when charging / discharging at a high current rate. Since the maintenance rate is high, it is more preferable.

A solid electrolyte may be used instead of the above electrolytic solution. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide polymer compound, a polymer compound containing at least one of a polyorganosiloxane chain or a polyoxyalkylene chain can be used. Moreover, what is called a gel type which hold | maintained the non-aqueous electrolyte in the high molecular compound can also be used. The _{Li 2 S-SiS 2, Li} 2 S-GeS 2, Li 2 S-P 2 S 5, Li 2 S-B 2 S 3, Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S-SiS _{2 -Li 2 SO 4, Li 2} S-GeS 2 -P 2 S 5 inorganic solid electrolytes containing a sulfide, and the like, may be used a mixture of two or more thereof. By using these solid electrolytes, the safety of the lithium secondary battery may be further improved.

  In the lithium secondary battery of the present embodiment, when a solid electrolyte is used, the solid electrolyte may serve as a separator, and in that case, the separator may not be required.

  Since the positive electrode active material having the above-described configuration uses the above-described lithium-containing composite metal oxide of the present embodiment, the lithium secondary battery using the positive electrode active material suppresses side reactions occurring inside the battery. be able to.

  Moreover, since the positive electrode having the above-described configuration has the above-described positive electrode active material for a lithium secondary battery according to the present embodiment, the lithium secondary battery can suppress side reactions occurring inside the battery.

  Furthermore, since the lithium secondary battery having the above-described configuration has the above-described positive electrode, it becomes a lithium secondary battery in which side reactions occurring inside the battery are suppressed more than ever.

Next, the present invention will be described in more detail with reference to examples.
In this example, the firing raw material and the lithium-containing composite metal oxide (positive electrode active material) were evaluated as follows.

(1) Determination of chromium in lithium-containing composite metal oxide (ICP emission analysis)
The metal oxide composition analysis was performed using an inductively coupled plasma issuance analyzer (Optima 7300 DV, manufactured by Perkin Elmer) after dissolving the metal oxide powder in hydrochloric acid.

(2) Determination of residual lithium carbonate in lithium-containing composite metal oxide (neutralization titration)
20 g of lithium-containing composite metal oxide and 100 g of pure water were placed in a 100 mL beaker and stirred for 5 minutes. After stirring, the lithium-containing composite metal oxide was filtered, 0.1 mol / L hydrochloric acid was added dropwise to 60 g of the remaining filtrate, and the pH of the filtrate was measured with a pH meter. In the lithium-containing composite metal oxide, the titration amount of hydrochloric acid at pH = 8.3 ± 0.1 hour is AmL, and the titration amount of hydrochloric acid at pH = 4.5 ± 0.1 hour is BmL. The remaining lithium carbonate concentration was calculated. In the following formula, the molecular weight of lithium carbonate was calculated by setting each atomic weight as Li; 6.941, C; 12, O;
Lithium carbonate concentration (%) = 0.1 × (BA) /1000×73.882/ (20 × 60/100) × 100

(3) Powder X-ray diffraction measurement of lithium composite metal oxide Powder X-ray diffraction measurement of lithium composite metal oxide was performed using a powder X-ray diffractometer (manufactured by Rigaku Corporation, Ultimate IV, sample horizontal type). . The obtained lithium composite metal oxide is filled in a dedicated substrate, and a powder X-ray diffraction pattern is obtained by measuring in a diffraction angle range of 2θ = 10 ° to 90 ° using a Cu—Kα ray source. Obtained. From the powder X-ray diffraction pattern, a peak in the range of 2θ = 18.7 ± 1 ° (hereinafter also referred to as peak A), a peak in the range of 2θ = 44.6 ± 1 ° (hereinafter, peak B) Half-width) was calculated.

Example 1
[Mixing process]
Lithium carbonate (Li ₂ CO ₃ ) and nickel cobalt manganese composite metal hydroxide (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) have a molar ratio of Li: Ni: Co: Mn of 1 .05: 0.55: 0.21: 0.24 and they were dry mixed to obtain a mixture. In addition, lithium carbonate content contained in this mixture is 29.7 mass% from a mixing ratio.
[Pre-baking step]
Next, the mixture was placed in a rotary kiln having an inner wall made of alumina and baked at 790 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product obtained in the preliminary firing step is placed in the rotary kiln and fired at 900 ° C. for 2 hours while a gas containing 21% by volume of oxygen is vented at 108.7 Nm ³ / h per 1 m ³ of the furnace volume. It was.
Thereafter, the mixture was cooled to room temperature and crushed to obtain a lithium composite metal oxide (a positive electrode active material for a lithium secondary battery). As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 2 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.25 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.129 and 0.152, respectively.

(Example 2)
[Mixing process]
Lithium carbonate (Li ₂ CO ₃ ) and nickel cobalt manganese composite metal hydroxide (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) have a molar ratio of Li: Ni: Co: Mn of 2 20: 0.55: 0.21: 0.24, and they were dry mixed to obtain a mixture. In addition, lithium carbonate content contained in this mixture is 46.6 mass% from a mixing ratio.
[Pre-baking step]
Next, the mixture was placed in a rotary kiln having an inner wall made of alumina and baked at 790 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in the rotary kiln and fired at 850 ° C. for 2 hours while a gas containing 100% by volume of oxygen was vented by 150.1 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 4 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.92 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.160 and 0.208, respectively.

(Example 3)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in a rotary kiln whose inner wall is alumina, and baked at 850 ° C. for 2 hours while a gas containing 21% by volume of oxygen was passed through 107.2 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 10 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.16 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.152 and 0.185, respectively.

Example 4
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in a rotary kiln having an inner wall made of alumina, and baked at 850 ° C. for 2 hours while a gas containing 60% by volume of oxygen was vented by 107.2 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 31 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.19 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.153 and 0.194, respectively.

(Example 5)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in a rotary kiln having an inner wall made of alumina, and baked at 850 ° C. for 2 hours while a gas containing 100% by volume of oxygen was passed through 46.5 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 49 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.15 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.152 and 0.178, respectively.

(Example 6)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in a rotary kiln having an inner wall made of alumina, and baked at 850 ° C. for 2 hours while a gas containing 21% by volume of oxygen was vented at 46.5 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of performing ICP emission analysis on the lithium composite metal oxide, the chromium content was 20 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.51 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.149 and 0.182, respectively.

(Example 7)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in a rotary kiln having an inner wall made of alumina, and baked at 850 ° C. for 2 hours while a gas containing 21% by volume of oxygen was passed through 17.9 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 19 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.90 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.161 and 0.200, respectively.

(Example 8)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was put into a rotary kiln whose inner wall of the furnace was alumina, and baked at 850 ° C. for 2 hours while a gas containing 100% by volume of oxygen was passed through 17.9 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 45 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.53 mass%. Moreover, as a result of performing powder X-ray diffraction, the half width of the peak A and the peak B was 0.151 and 0.184, respectively.

(Comparative Example 1)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in a rotary kiln whose inner wall of the furnace was Inconel, and fired at 730 ° C. for 2 hours while a gas containing 21% by volume of oxygen was passed through 22.6 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 55 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 5.31 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.458 and 0.639, respectively.

(Comparative Example 2)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in a rotary kiln whose inner wall of the furnace was Inconel, and fired at 730 ° C. for 4 hours while a gas containing 21% by volume of oxygen was passed through 22.6 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 60 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 3.43 mass%. Moreover, as a result of performing powder X-ray diffraction, the half width of the peak A and the peak B was 0.415 and 0.578, respectively.

(Comparative Example 3)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was placed in a rotary kiln having an inner wall of SUS310, and fired at 730 ° C. for 5 hours while a gas containing 21% by volume of oxygen was passed through 22.6 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of performing ICP emission analysis on the lithium composite metal oxide, the chromium content was 320 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 1.13 mass%. Moreover, as a result of performing powder X-ray diffraction, the half width of the peak A and the peak B was 0.214 and 0.261, respectively.

(Comparative Example 4)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was filled in a sheath whose inner wall of the furnace was alumina, and was 2 at 850 ° C. while a roller hearth kiln was ventilated with 29.7 Nm ³ / h of gas containing 21% by volume of oxygen per 1 m ³ of the furnace volume. Time firing was performed. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 10 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 1.01 mass%. Moreover, as a result of performing powder X-ray diffraction, the half width of the peak A and the peak B was 0.225 and 0.278, respectively.

(Comparative Example 5)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product is filled in a sheath whose inner wall is made of alumina, and is heated at 850 ° C. with a roller hearth kiln, while a gas containing 21% by volume of oxygen is passed through 29.7 Nm ³ / h per 1 m ³ of the furnace volume. Time firing was performed. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of performing neutralization titration on the lithium composite metal oxide, the lithium carbonate content was 0.67% by mass. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.129 and 0.150, respectively.

(Comparative Example 6)
[Mixing process]
Lithium carbonate (Li ₂ CO ₃ ) and nickel cobalt manganese composite metal hydroxide (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) are mixed with a molar ratio of Li: Ni: Co: Mn of 3 0.000: 0.55: 0.21: 0.24, and these were dry mixed to obtain a mixture. In addition, lithium carbonate content contained in this mixture is 54.3 mass% from mixing ratio. While the mixture is oven inner wall to the rotary kiln oxygen 21 vol% including 17.9Nm ³ / h aeration per furnace volume 1 m ³ of gas in alumina, it was carried out for 2 hours calcination at 850 ° C.. However, the mixture and the fired product adhered to the wall of the furnace core tube and could not be discharged.

(Reference example)
[Mixing process]
A mixture was obtained in the same manner as in Example 1.
[Pre-baking step]
The mixture described in Example 1 was placed in a rotary kiln having an inner wall of Inconel and baked at 730 ° C. for 2 hours.
[Main firing process]
Subsequently, the fired product was put into a rotary kiln whose inner wall of the furnace was alumina, and baked at 850 ° C. for 4 hours while a gas containing 21% by volume of oxygen was vented at 17.9 Nm ³ / h per 1 m ³ of the furnace volume. Then, it cooled to room temperature and this was crushed and the lithium composite metal oxide was obtained. As a result of ICP emission analysis of the lithium composite metal oxide, the chromium content was 13 ppm. Moreover, as a result of performing neutralization titration, lithium carbonate content was 0.10 mass%. Further, as a result of powder X-ray diffraction, the half widths of peak A and peak B were 0.149 and 0.183, respectively.

  Hereinafter, Tables 1 to 3 collectively describe the conditions and results of Examples, Comparative Examples, and Reference Examples. In the table, RK indicates a rotary kiln, and RHK indicates a roller hearth kiln.

As shown in the following Tables 1 to 3, Examples 1 to 8 to which the present invention is applied can produce a positive active material having a small peak half-value width, that is, high crystallinity, in a short baking time. did it. Furthermore, in Examples 1 to 8 to which the present invention was applied, the chromium content was low.
On the other hand, Comparative Examples 1-3 which implemented this baking process with the metal rotary kiln had much chromium content, and the peak half value width was also large. Moreover, although the comparative example 4 which used the roller hearth kiln for the main baking process and made the baking time of 2 hours has a large peak half value width and the comparative example 5 has a small peak half value width, the main baking time required 10 hours.
In Reference Example 1, the main firing was performed for 4 hours using a non-metallic rotary kiln. When Reference Example 1 and Example 1 were compared, the peak half-value widths were comparable. That is, a positive electrode active material with high crystallinity could be produced in a short (2 hours) firing time.

  DESCRIPTION OF SYMBOLS 1 ... Separator, 2 ... Positive electrode, 3 ... Negative electrode, 4 ... Electrode group, 5 ... Battery can, 6 ... Electrolyte solution, 7 ... Top insulator, 8 ... Sealing body, 10 ... Lithium secondary battery, 21 ... Positive electrode lead, 31 ... Negative electrode lead

Claims (8)

A mixing step of mixing a lithium compound and a positive electrode active material precursor to obtain a mixture;
A main baking step of baking the mixture using a rotary kiln;
A method for producing a positive electrode active material for a lithium secondary battery, comprising:
The content of the lithium compound contained in the mixture is more than 0 and 50% by mass or less,
A method for producing a positive electrode active material for a lithium secondary battery, wherein a furnace inner wall of the rotary kiln is made of a non-metallic material.   The manufacturing method of the positive electrode active material for lithium secondary batteries of Claim 1 which performs the said main baking process at 750 to 1000 degreeC. The manufacturing method of the positive electrode active material for lithium secondary batteries of Claim 1 or 2 with which the said positive electrode active material for lithium secondary batteries is represented by the following general formula (I).
_{Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 ··· (I)
(In the general formula (I), −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.5, 0 <z ≦ 0.8, 0 ≦ w ≦ 0.1, y + z + w <1, M is (It represents one or more metals selected from the group consisting of Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, and V.)   The lithium according to any one of claims 1 to 3, further comprising a pre-baking step of baking at a temperature lower than a heating temperature of the main baking after the mixing step and before the main baking step. A method for producing a positive electrode active material for secondary batteries 5. The method according to claim 1, wherein one or both of the main baking step and the preliminary baking step is performed by ventilating an oxygen-containing gas at a flow rate of 15 Nm ³ / h / m ³ or more. A method for producing a positive electrode active material for a lithium secondary battery.   The manufacturing method of the positive electrode active material for lithium secondary batteries of Claim 5 whose oxygen concentration in the said oxygen gas is 21 volume% or more.   The manufacturing method of the positive electrode active material for lithium secondary batteries of any one of Claims 1-6 whose content of chromium contained in the said positive electrode active material for lithium secondary batteries is 50 ppm or less.   The positive electrode active material for a lithium secondary battery according to any one of claims 1 to 7, wherein a content of lithium carbonate contained in the positive electrode active material for the lithium secondary battery is 1.0 mass% or less. Production method.

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