KR20190062432A - Method for producing positive electrode active material for lithium secondary battery - Google Patents

Abstract

The present invention relates to a process for producing 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 firing step of firing the mixture using a rotary kiln, Wherein the content of the lithium compound contained in the rotary kiln is greater than 0 and less than or equal to 50 mass%, and the furnace inner wall of the rotary kiln is made of a non-metallic material.

Description

Method for producing positive electrode active material for lithium secondary battery

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

The present application claims priority based on Japanese Patent Application No. 2016-201566, filed on October 13, 2016, the contents of which are incorporated herein by reference.

A lithium composite oxide is used as a positive electrode active material for a lithium secondary battery. Lithium secondary batteries have already been put to practical use not only for small-sized power sources such as portable telephone applications and notebook PC applications, but also for medium-sized or large-sized power sources such as automobile applications and power storage applications.

A method of producing a positive electrode active material for a lithium secondary battery generally includes a step of firing a lithium compound and a precursor which is a metal complex oxide.

Attempts have been made to attempt to equalize the composition of the positive electrode active material for a lithium secondary battery and to reduce the amount of unreacted materials to improve the performance of the lithium secondary battery such as cycle characteristics.

For example, Patent Document 1 discloses that a positive electrode material with a small variation in oxidation can be produced with good productivity by performing a firing step using a roller washer kiln.

Japanese Patent Application Laid-Open No. 2006-4724

 In the field of application of lithium secondary batteries, the positive electrode active material for lithium secondary batteries is required to have high crystallinity in order to improve various battery characteristics.

However, as described in Patent Document 1, when a roller washer kiln is used, a long time is required for firing, and further, the crystallinity is not sufficient.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for producing a positive electrode active material for a lithium secondary battery excellent in crystallinity.

That is, the present invention includes the following inventions [1] to [8].

[1] A process for producing 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 firing step of firing the mixture using a rotary kiln, Wherein the content of the lithium compound is greater than 0 and less than 50 mass% with respect to the total mass of the mixture, and the furnace inner wall of the rotary kiln is made of a non-metallic 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 carried out at a temperature of 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 comprises a lithium metal composite oxide represented by the following general formula (I).

_{Li [Li x (Ni (1} -yzw) Co y Mn z M w) 1-x] O 2 ... (I)

(In the formula (I), -0.1? X? 0.2, 0 <y? 0.5, 0? Z? 0.8, 0? W? 0.1, y + z + And at least one element selected from the group consisting of Al, W, B, Mo, Nb, Zn, Sn, Zr,

[4] The method for producing a lithium secondary battery according to any one of [1] to [3], wherein the prebaking step is performed after the mixing step and before the main firing step, A method for producing a positive electrode active material.

[5] A method as described in any one of [1] to [4], wherein at least one of the main firing step and the preliminary firing step is carried out by flowing an oxygen-containing gas at a flow rate of 15 Nm ³ / h / A method for producing a positive electrode active material for a lithium secondary battery.

[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-containing gas is 21% by volume or more based on the total volume of the oxygen-containing gas.

[7] The positive electrode active material for a lithium secondary battery according to any one of [1] to [6], wherein the content of chromium contained in the positive electrode active material for lithium secondary batteries is 50 ppm or less relative to the total mass of the positive electrode active material for lithium secondary batteries Gt;

[8] The lithium secondary battery according to any one of [1] to [7], wherein the content of lithium carbonate contained in the positive electrode active material for lithium secondary batteries is 1.0% by mass or less based on the total mass of the positive electrode active material for lithium secondary batteries. A method for producing an active material.

According to the present invention, it is possible to provide a method for producing a positive electrode active material for a lithium secondary battery excellent in crystallinity.

1A is a schematic structural view showing an example of a lithium ion secondary battery.
1B is a schematic configuration diagram showing an example of a lithium ion secondary battery.
2 is a schematic view showing an example of a rotary kiln.
3 is a schematic sectional view in the direction perpendicular to the longitudinal direction of the rotary kiln.
4 is a schematic sectional view of the rotary kiln in the longitudinal direction.

&Lt; Method for producing positive electrode active material for lithium secondary battery &

A method for producing a positive electrode active material for a lithium secondary battery of the present invention (hereinafter also referred to as a "positive electrode active material") comprises mixing a lithium compound and a positive electrode active material precursor (hereinafter also referred to as "precursor"), And a firing step of firing the mixture using a rotary kiln, wherein the content of the lithium compound contained in the mixture is more than 0 and less than 50 Mass% or less, and the furnace inner wall of the rotary kiln is formed of a non-metallic material.

For the firing step of the lithium compound and the precursor, facilities such as a roller hearth kiln and a rotary kiln are conventionally used as tunnels.

Tunnel furnaces or roller hearth kilns have a problem that the firing efficiency is low and the firing is required for a long time because the mixture is fired and filled in the tofu.

In addition, if the inner wall of the furnace is made of metal, the rotary kiln has a problem that when the furnace is fired at a high temperature, the metal elutes from the member and the cathode active material is contaminated by the eluted metal component.

The present invention is carried out by using a rotary kiln formed of a nonmetallic material as a furnace inner wall, which is a portion where a mixture is brought into contact with a firing step of a mixture of a lithium compound and a precursor. For this reason, when firing at a high temperature, the metal does not elute from the inner wall of the furnace, and the positive electrode active material is not contaminated. Further, since the content of the lithium compound is 50% by mass or less based on the total mass of the mixture, the mixture can be fired without excessively adhering the mixture and the fired product to the rotary kiln even if the mixture is fired at a high temperature .

Hereinafter, a method for producing the positive electrode active material for a lithium secondary battery of the present invention will be described.

[Mixing Process]

This step is a step of mixing a lithium compound and a precursor to obtain a mixture.

In this step, the lithium compound is mixed so that the content of the lithium compound in the mixture of the lithium compound and the precursor is greater than 0 and less than 50 mass% with respect to the total mass of the mixture.

The lower limit of the content of the lithium compound with respect to the total mass of the mixture is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more.

The upper limit of the content of the lithium compound with respect to the total mass of the mixture is preferably 49 mass% or less, more preferably 48 mass% or less, and particularly preferably 47 mass% or less.

The upper limit value and the lower limit value may be arbitrarily combined.

For example, the content of the lithium compound relative to the total mass of the mixture is preferably from 10 mass% to 49 mass%, more preferably from 15 mass% to 48 mass%, still more preferably from 20 mass% to 47 mass% Or less.

In the present invention, by setting the content of the lithium compound to the total mass of the mixture in the mixture to the above specified content, adhesion of the mixture and the calcined product to the furnace inner wall of the rotary kiln can be reduced. Therefore, in the firing step to be described later, firing can be performed at a high temperature, and a high-crystalline positive electrode active material can be obtained.

· Lithium compound

The lithium compound used in the present invention will be described.

The lithium compound to be used in the present invention is not particularly limited and any one or more of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate and lithium oxide may be used in combination. Of these, either or both of lithium hydroxide and lithium carbonate is preferable.

· Precursor

The precursor is preferably a transition metal compound. The precursor is selected from the group consisting of a metal other than lithium, that is, Ni, which is an essential metal, and Co, Mn, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, And is preferably a transition metal compound containing at least one arbitrary element. The transition metal compound is preferably a transition metal hydroxide or a transition metal oxide, and specifically, a nickel cobalt manganese composite hydroxide or a 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 the above-mentioned specific mixing conditions, it is possible to carry out calcination at a high temperature in the baking step, and the development of the crystal can be progressed well.

In the main firing step, the inner wall of the furnace, which is the contact area with the mixture, is carried out by a rotary kiln formed of a non-metallic material.

The rotary kiln used in the present embodiment will be described with reference to Figs. 2 to 4. Fig.

The rotary kiln 40 includes a cylindrical core tube 42, a rotating device (not shown) for rotating the core tube 42, and a heat insulating material (not shown) covering the core tube 42 (Not shown) for heating the core pipe 42, a raw material charging device (not shown) for charging the raw material for firing into the core pipe 42, and a discharge unit Omitted). As shown in Fig. 4, the core pipe 42 is provided so as to be inclined so that the outlet side is lower than the inlet side into which the firing raw material is injected. As the core tube 42 rotates, the firing material is mixed and sent from the inlet side to the outlet side of the core tube 42, and firing is performed. Further, the oxygen-containing gas is normally vented from the outlet side to the inlet side as indicated by the broken arrow in Fig.

Specifically, the mixture is supplied to a rotary kiln 40 and the core tube 42 constituting the rotary kiln 40 is rotated. While the mixture is being mixed, the mixture is heated to a predetermined temperature By heating the rotary kiln as much as possible. In the present invention, the furnace inner wall 41 means the inner wall of the core tube 42. [

Examples of the non-metallic material 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) ), And it is particularly preferable that the ceramic material contains 50 mass% or more of aluminum oxide with respect to the total mass of the non-metallic material.

The filling amount of the mixture with respect to the total volume of the rotary kiln is preferably 1% by volume to 50% by volume, more preferably 3% by volume to 30% by volume, further preferably 5% by volume to 20% by volume .

The firing step is preferably carried out at 750 ° C or higher and 1000 ° C or lower.

By setting the firing temperature to a high temperature range of 750 ° C or more and 1000 ° C or less, a highly crystalline positive electrode active material can be produced.

In the present embodiment, the temperature of the firing step means the temperature of the mixture to be fired.

[Preliminary firing process]

In the present invention, it is preferable that the pre-firing step is performed after the mixing step and before the main firing step, the firing is performed at a temperature lower than the firing temperature of the main firing. The preliminary firing may be lower in temperature than the main firing, preferably 80 to 200 ° C lower than the firing temperature of the firing, and preferably 100 to 150 ° C lower.

By performing the preliminary firing, a positive electrode active material containing a lithium metal composite oxide having a high crystallinity can be obtained, and unreacted materials can be reduced.

The firing furnace of the preliminary firing process is not particularly limited, but it is preferable to use a rotary kiln. The firing step and the preliminary firing step may be the same rotary kiln or may be different rotary kilns, and it is preferable to use the same rotary kiln from the viewpoint of continuous firing process.

The contact portion of the firing furnace used in the preliminary firing step may be a metallic material such as inconel or a nonmetal material such as silicon nitride (Si ₃ N ₄ ) or aluminum oxide (Al ₂ O ₃ ; alumina) .

It is preferable that either or both of the main firing step and the preliminary firing step is carried out by passing an oxygen-containing gas at a flow rate of 15 Nm ³ / h / m ³ or more, more preferably 16 Nm ³ / h / m ³ or more . The upper limit is not particularly limited, and an example would be 150 Nm ³ / h / ㎥ or less, 130 Nm ³ / h / ㎥ or less, 120 Nm ³ / h / ㎥ below.

The upper limit value and the lower limit value may be arbitrarily combined.

For example, the flow rate is, 15 Nm ³ / h / ㎥ more than 150 Nm ³ / h / ㎥ than that is preferred, more preferably 16 Nm ³ / h / ㎥ or less than ^{130 Nm 3 / h / ㎥,} 16 it Nm ³ / h / ㎥ more than 120 Nm ³ / h / ㎥ or less is more preferred.

In another aspect of this embodiment is that the flow rate is, 40 Nm ³ / h / ㎥ more than 200 Nm ³ / h / ㎥ is preferred, more than ^{80 Nm 3 / h / ㎥ 180} Nm 3 / h / ㎥ or less than is more preferred, and, 130 Nm ³ / h / ㎥ more than 160 Nm ³ / h / ㎥ or less is more preferred.

It is preferable that either or both of the main firing step and the preliminary firing step is performed so that the oxygen concentration in the oxygen gas is 21% by volume or more based on the total volume of the oxygen-containing gas. The oxygen-containing gas having the oxygen concentration can be obtained by mixing a gas other than oxygen and oxygen gas at a predetermined ratio. The flow rates of gases other than oxygen and oxygen gas can be controlled by a known flow meter. Alternatively, the air may be used as it is.

In the present invention, it is preferable that the present firing step is carried out under the above-described aeration conditions.

The firing time is preferably from 1 hour to 10 hours, more preferably from 1 hour to 8 hours, even more preferably from 1 hour to 5 hours Particularly preferred.

In the present invention, when the preliminary firing is carried out, the time from the start of the temperature rise in the preliminary firing step to the end of the main firing step is performed within the above-mentioned period.

More specifically, the preliminary firing step is preferably performed for 30 minutes to 3 hours, more preferably for 1 hour to 2.5 hours.

The firing step is preferably performed for 30 minutes to 3 hours, more preferably for 1 hour to 2.5 hours.

In another aspect of the present invention, the holding time after reaching the target temperature in the firing step is preferably 1 hour or more and 10 hours or less, more preferably 1 hour or more and 8 hours or less, More preferably not more than 6 hours. The rate of temperature rise to the target temperature is preferably 20 ° C / hour to 2000 ° C / hour, more preferably 50 ° C / hour to 1000 ° C / hour, more preferably 100 ° C / Deg.] C / hour or less.

In the present invention, the inner wall of the furnace, which is a portion where the mixture is brought into contact with the main firing step, is carried out using a rotary kiln made of a non-metallic material.

The metal rotary kiln needs to be fired at a temperature at which the elution of the metal does not occur. However, when a rotary kiln formed of a non-metallic material is used as the inner wall of the furnace, The firing temperature can be set to a high temperature. Therefore, in the case of using a rotary kiln in which the furnace inner wall is made of a non-metallic material, the firing process can be performed at a higher temperature than in the case where the furnace inner wall is made of a metal rotary kiln. For this reason, a positive electrode active material containing a lithium metal composite oxide having high crystallinity can be obtained by a short time firing process.

The lithium metal composite oxide obtained by firing is appropriately classified after the pulverization and becomes a positive electrode active material for a lithium secondary battery applicable to a lithium secondary battery. By the classification process, the positive electrode active material for a lithium secondary battery is usually classified into 200 to 400 meshes.

One aspect of the present invention is a method for producing a positive electrode active material for a lithium secondary battery, which further comprises a pulverizing and classifying step in addition to the mixing step and the main firing step described above.

&Lt; Positive electrode active material for lithium secondary battery &

A positive electrode active material for a lithium secondary battery produced by the method for producing a positive electrode active material for a lithium secondary battery of the present invention will be described below.

In order to increase the energy density of the lithium secondary battery, the positive electrode active material for a lithium secondary battery preferably includes a lithium metal composite oxide represented by the following formula (I).

_{Li [Li x (Ni (1} -yzw) Co y Mn z M w) 1-x] O 2 ... (I)

(In the formula (I), -0.1? X? 0.2, 0 <y? 0.5, 0? Z? 0.8, 0? W? 0.1, y + z + And at least one element selected from the group consisting of Al, W, B, Mo, Nb, Zn, Sn, Zr,

In the context of obtaining a lithium secondary battery having a high cycle characteristic, x in the above formula (I) is preferably 0 or more, more preferably 0.01 or more, and still more preferably 0.02 or more. Also, in view of obtaining a lithium secondary battery having higher initial Coulomb efficiency, x in the above composition formula (I) is preferably 0.18 or less, more preferably 0.15 or less, and further preferably 0.1 or less.

The upper limit value and the lower limit value of x can be arbitrarily combined.

For example, x is preferably 0 or more and 0.18 or less, more preferably 0.01 or more and 0.15 or less, still more preferably 0.02 or more and 0.1 or less.

In the present specification, "high cycle characteristics" means high discharge capacity retention rate.

In order to obtain a lithium secondary battery having a high cycle characteristic, y in the above composition formula (I) is preferably 0.13 or more, more preferably 0.14 or more. In order to obtain a lithium secondary battery having a high thermal stability, y in the above composition formula (I) is preferably 0.35 or less, more preferably 0.3 or less, still more preferably 0.25 or less.

The upper limit value and the lower limit value of y can be arbitrarily combined.

For example, y is preferably 0.13 or more and 0.35 or less, more preferably 0.14 or more and 0.3 or less, and still more preferably 0.14 or more and 0.25 or less.

In order to obtain a lithium secondary battery having a high cycle characteristic, z in the above formula (I) is preferably 0.1 or more, more preferably 0.15 or more, and more preferably 0.2 or more. Further, z is preferably 0.35 or less, more preferably 0.32 or less, and most preferably 0.30 or less in terms of obtaining a lithium secondary battery having high storage characteristics at a high temperature (for example, at 60 캜 environment) Or less.

The upper limit value and the lower limit value of z can be arbitrarily combined.

For example, z is preferably 0.1 or more and 0.35 or less, more preferably 0.15 or more and 0.32 or less, still more preferably 0.2 or more and 0.30 or less.

In view of increasing the handling properties of the positive electrode active material for a lithium secondary battery, w in the composition formula (I) is preferably more than 0, more preferably 0.001 or more, and still more preferably 0.005 or more. In view of obtaining a lithium secondary battery having a high discharge capacity at a high current rate, w in the above composition formula (I) is preferably 0.04 or less, more preferably 0.03 or less, and still more preferably 0.02 or less.

The upper limit value and the lower limit value of w can be arbitrarily combined.

For example, the value is preferably more than 0 and 0.04 or less, more preferably 0.001 or more and 0.03 or less, still more preferably 0.005 or more and 0.02 or less.

M in the composition formula (I) is at least one element selected from the group consisting of Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr,

In the present invention, the lithium compound and the positive electrode active material precursor may be mixed so that the produced positive electrode active material for the lithium secondary battery includes the lithium metal composite oxide having the desired composition represented by the composition formula (I).

(Layered structure)

It is more preferable that the crystal structure of the positive electrode active material is a layered structure and a hexagonal crystal structure or a monoclinic crystal structure.

The crystal structure of the hexagonal crystal is P3, P3 ₁ , P3 ₂ , R3, P3, R3, P312, P321, P3 ₁ 12, P3 ₁ 21, P3 ₂ 12, P3 ₂ 21, R32, P3m1, , P3c1, P31c, R3m, R3c , P-31m, P31c, P-3m1, P3c1, R3m, R3c, P6, P6 1, P6 5, P6 2, P6 4, P6 3, _{P6, P6 / m, P6 3} / m, P622, P6 1 22, P6 5 22, P6 2 22, P6 4 22, P6 3 22, P6mm, P6cc, P6 3 cm, P6 3 mc, P-6m2 , P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P6 ₃ / mcm and P6 ₃ / mmc.

In addition, a crystal structure of monoclinic shaping is, P2, P2 _1, C2, Pm, Pc, Cm, Cc, P2 / m, P2 ₁ / m, C2 / m, P2 / c, P2 ₁ / c, C2 / c And is assigned to any space group selected from the group consisting of

Of these, in the sense of obtaining a lithium secondary battery having a high discharge capacity, it is particularly preferable that the crystal structure is a hexagonal crystal structure attributed to the space group R-3m or a monoclinic crystal structure attributed to C2 / m .

In the present embodiment, the crystallinity of the positive electrode active material is determined by the full width at half maximum (FWHM) of the diffraction peak within 2θ = 18.7 ± 1 ° of the X-ray diffraction pattern obtained by X- ), And the half width of the diffraction peak within the range of 2? = 44.4 占 占.

The range of the half width of the diffraction peak within the range of 2? = 18.7 占 is preferably 0.01 to 0.20, more preferably 0.02 to 0.19, and still more preferably 0.03 to 0.18.

The half-width of the diffraction peak within the range of 2? = 44.4 占 is preferably 0.01 to 0.25, more preferably 0.02 to 0.22, still more preferably 0.03 to 0.20.

In the present invention, since the furnace inner wall, which is the portion where the mixture is in contact with the mixture, is subjected to the firing process using a rotary kiln made of a nonmetallic material, even if calcination is performed at a high temperature of 750 ° C to 1000 ° C to increase the crystallinity of the positive electrode active material, The elution of the metal from the material of the firing furnace can be reduced. Therefore, when attention is focused on chromium, which is a kind of metal impurity, a positive electrode active material having a reduced chromium content can be produced.

The content of chromium relative to the total mass of the positive electrode active material for a lithium secondary battery contained in the positive electrode active material for a lithium secondary battery produced by the present invention is preferably 50 ppm or less, more preferably 45 ppm or less, desirable.

The content of chromium in relation to the total mass of the positive electrode active material for a lithium secondary battery contained in the positive electrode active material for a lithium secondary battery is measured by bringing the powder of the positive electrode active material for lithium secondary battery into contact with hydrochloric acid to dissolve, As shown in FIG.

In the method for producing a positive electrode active material for a lithium secondary battery according to the present invention, since the furnace inner wall, which is a portion where the mixture contacts, is fired using a rotary kiln made of a non-metallic material, firing can be performed at a high temperature. Therefore, decomposition of lithium carbonate in the raw material is promoted, and the amount of lithium carbonate remaining in the produced positive electrode active material is reduced.

The content of lithium carbonate is preferably 1.0% by mass or less, more preferably 0.99% by mass or less, and particularly preferably 0.95% by mass or less, relative to the total mass of the positive electrode active material contained in the positive electrode active material for a lithium secondary battery produced by the present invention, desirable. The lower limit of the content of lithium carbonate with respect to the total mass of the positive electrode active material is not particularly limited, but may be, for example, 0.05 mass% or more, 0.10 mass% or more, and 0.2 mass% or more.

The upper limit value and the lower limit value may be arbitrarily combined.

For example, the content of lithium carbonate relative to the total mass of the positive electrode active material is preferably 0.05 mass% or more and 1.0 mass% or less, more preferably 0.10 mass% or more and 0.99 mass% or less, more preferably 0.2 mass% or more and 0.95 mass % Or less.

The content of the lithium carbonate component contained in the positive electrode active material for a lithium secondary battery can be determined by neutralization titration with an acidic solution. Specifically, the positive electrode active material for a lithium secondary battery is contact-treated with pure water, and the lithium carbonate component is eluted into pure water. The content of the lithium carbonate component can be determined by neutralizing the eluate with an acidic solution such as hydrochloric acid. A more specific operation and a calculation method of the content of the lithium carbonate component and the like are described in Examples.

Contrary to the present invention, when the mixture is sintered by charging the mixture to a toe cap, such as a roller harsh kiln, the oxygen-containing gas does not spread sufficiently to the mixture filled in the bottom of the toe shell, There is a tendency that a large amount of lithium carbonate is present in the positive electrode active material to be produced.

<Lithium secondary battery>

Next, the positive electrode using the positive electrode active material for a lithium secondary battery produced by the method for producing the positive electrode active material for a lithium secondary battery of the present invention, and the lithium secondary battery having the positive electrode will be described while explaining the structure of the lithium secondary battery.

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.

1A and 1B are schematic diagrams showing an example of a lithium secondary battery of the present embodiment. The cylindrical lithium secondary battery 10 of the present embodiment is manufactured as follows.

First, as shown in Fig. 1A, a pair of separators 1 each having a strip shape, a strip-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a strip-shaped electrode having a negative electrode lead 31 at one end The negative electrode 3 of the separator 1 is laminated in the order of the separator 1, the positive electrode 2, the separator 1 and the negative electrode 3 and wound to form an electrode group 4.

Subsequently, as shown in Fig. 1B, the electrode group 4 and an insulator (not shown) are housed in the battery can 5, the can bottom is sealed, the electrode group 4 is impregnated with the electrolyte solution 6, An electrolyte is disposed between the positive electrode (2) and the negative electrode (3). Further, 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, when the electrode group 4 is cut in a direction perpendicular to the winding axis, the cross-sectional shape of the electrode group 4 is a circle, an ellipse, a rectangle, Shaped shape.

The shape of the lithium secondary battery having such an electrode group 4 may adopt a shape defined by IEC60086 or JIS C 8500, which is a standard for a battery defined by the International Electrotechnical Commission (IEC). For example, a cylindrical shape, a square shape, or the like.

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

Hereinafter, each configuration will be described in order.

(Positive electrode)

The positive electrode of the present embodiment can be produced by first adjusting the positive electrode mixture containing the positive electrode active material, the conductive material and the binder, and then carrying the positive electrode mixture onto the positive electrode collector.

(Conductive material)

As the conductive material of the positive electrode of the present embodiment, a carbon material can be used. Examples of the carbon material include graphite powder, carbon black (e.g., acetylene black), fibrous carbon material, and the like. Carbon black is fine and has a large surface area. Therefore, it is possible to increase the conductivity inside the positive electrode by adding a small amount to the positive electrode mixture to improve the charging / discharging efficiency and the output characteristic. However, if the amount is too large, Both the binding force and the binding force inside the positive electrode mixture are lowered, which causes the internal resistance to increase.

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 based on 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.

(bookbinder)

As the binder of 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 may be referred to as PTFE), tetrafluoroethylene, propylene hexafluoride, vinylidene fluoride Fluorinated resins such as propylene hexafluoride-vinylidene fluoride copolymer, tetrafluoroethylene-perfluoro vinyl ether copolymer, and the like; Polyolefin resins such as polyethylene and polypropylene; .

These thermoplastic resins may be used in combination of two or more kinds. By using a fluororesin and a polyolefin resin as the binder and setting the ratio of the fluororesin to the total mass of the positive electrode mixture mixture to 1 mass% to 10 mass% and the proportion of the polyolefin resin to 0.1 mass% to 2 mass% It is possible to obtain a positive electrode mixture having high adhesion to the whole and high bonding force inside the positive electrode mixture.

(Positive electrode collector)

As the positive electrode collector of the positive electrode of the present embodiment, a strip-shaped member made of a metal material such as Al, Ni, or stainless steel can be used. Among them, it is preferable to use Al as a forming material and to process it into a thin film form because it is easy to process and is inexpensive.

As a method for supporting the positive electrode mixture on the positive electrode collector, there is a method of press-molding the positive electrode mixture on the positive electrode collector. Alternatively, the positive electrode mixture may be supported on the positive electrode collector by pasting the positive electrode mixture using an organic solvent, applying the paste of the obtained positive electrode mixture onto at least one surface of the positive electrode collector, drying and pressing and fixing.

When the positive electrode material mixture is pasted, examples of the organic solvent that can be used include amine type solvents such as N, N-dimethylaminopropylamine and diethylene triamine; Ether solvents such as tetrahydrofuran; Ketone solvents such as methyl ethyl ketone; Ester solvents such as methyl acetate; Amide-based solvents such as dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter, may be referred to as NMP), and the like.

Examples of the method of applying the paste of the positive electrode material mixture 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 spraying method.

The positive electrode can be produced by the method exemplified above.

(Negative electrode)

The negative electrode included in the lithium secondary battery of the present embodiment is an electrode in which lithium ions can be doped and deodoped to a potential lower than the positive electrode and a negative electrode material mixture containing the negative electrode active material is carried on the negative electrode collector, And the like.

(Negative electrode active material)

Examples of the negative electrode active material of the negative electrode include a carbon material, a chalcogen compound (oxide, sulfide, etc.), a nitride, a metal or an alloy, and a material capable of doping and dedoping lithium ions at a potential lower than that of the positive electrode.

Examples of the carbon material usable as the negative electrode active material include graphite such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbon materials, carbon fibers, and sintered bodies of organic polymers.

Examples of oxides that can be used as the negative electrode active material include oxides of silicon represented _{by the} formula SiO _x (where x is a positive real number) such as SiO ₂ and SiO; An oxide of titanium represented _{by the} formula TiO _x (where x is a positive real number) such as TiO ₂ and TiO; V ₂ O ₅ , VO ₂ oxides of vanadium expressed _{by the} formula VO _x (where x is a positive real number); An oxide of iron represented _{by the} formula FeO _x (where x is a positive real number) such as Fe ₃ O ₄ , Fe ₂ O ₃ , and FeO; An oxide of tin represented _{by the} formula SnO _x (where x is a positive real number) such as SnO ₂ and SnO; Oxides of tungsten represented _{by the} general formula WO _x (where x is a positive real number) such as WO ₃ and WO ₂ ; Composite metal oxides containing lithium and titanium or vanadium such as Li ₄ Ti ₅ O ₁₂ and LiVO ₂ ; .

Examples of the sulfide that can be used as the negative electrode active material include sulfides of titanium 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 Sulfide of vanadium expressed _{by the} formula VS _x (where x is a positive real number); Fe ₃ S ₄ , FeS ₂ , and FeS; iron sulfides represented _{by the} formula FeS _x (where x is a positive real number); Mo ₂ S ₃ , MoS ₂ Sulfide of molybdenum expressed _{by the} formula MoS _x (where x is a positive real number); Tin sulfide represented _{by the} formula SnS _x (where x is a positive real number) such as SnS ₂ and SnS; WS ₂ Sulfide of tungsten represented _{by the} formula WS _x (where x is a positive real number); Sb ₂ S ₃ Sulfide of antimony represented _{by the} formula SbS _x (where x is a positive real number); Se ₅ S ₃ , SeS ₂ , SeS sulfide of selenium represented _{by the} formula SeS _x (where x is a positive real number); .

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

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

Examples of the metal usable as the negative electrode active material include lithium metal, silicon metal and tin metal.

Examples of the alloys usable 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; Tin alloys such as Sn-Mn, Sn-Co, Sn-Ni, Sn-Cu, and Sn-La; Cu ₂ Sb, and La ₃ Ni ₂ Sn ₇ ; .

Such a metal or an alloy is used mainly as an electrode mainly after it is processed into, for example, foil.

Among the above-mentioned negative electrode active materials, the negative electrode potential is hardly changed (the potential flatness is good), the average discharge potential is low, and the capacity retention ratio is high when the battery is repeatedly charged and discharged Carbon material having graphite as a main component such as natural graphite and artificial graphite is preferably used for the reasons such as good cycle characteristics. The shape of the carbon material may be, for example, a thin flake such as natural graphite, a spherical shape such as meso carbon micro bead, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.

The negative electrode material mixture may contain a binder if necessary. Examples of the binder include thermoplastic resins, and specifically, PVdF, thermoplastic polyimide, carboxymethylcellulose, polyethylene and polypropylene can be mentioned.

(Anode collector)

As the negative electrode collector of the negative electrode, a strip-shaped member made of a metal material such as Cu, Ni, or stainless steel can be mentioned. Among them, it is preferable that Cu is used as a forming material and it is processed into a thin film in that it is difficult to produce lithium and an alloy and is easy to process.

As a method for supporting the negative electrode mixture on the negative electrode collector, a method of making the paste by using a method of press molding, a solvent or the like and applying it on the negative electrode collector, drying, pressing, .

(Separator)

The separator included in the lithium secondary battery of the present embodiment may be a separator made of a material such as a polyolefin resin such as polyethylene or polypropylene, a fluororesin or a nitrogen-containing aromatic polymer, a porous film having a shape of a nonwoven fabric, Materials can be used. In addition, a separator may be formed using two or more of these materials, or a separator may be formed by laminating such materials.

In the present embodiment, the separator has a durability of 50 sec / 100 cc or more, 300 (cc / sec) or more, preferably 300 cc / sec or more, in order to allow the electrolyte to pass through well Sec / 100 cc or less, more preferably 50 sec / 100 cc or more and 200 sec / 100 cc or less.

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 based on the total volume of the separator. The separator may be a laminate of separators having different porosity.

(Electrolytic solution)

The electrolyte solution of the lithium secondary battery of the present embodiment contains an electrolyte and an organic solvent.

The electrolyte contained in the _{electrolyte, 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 ( wherein, BOB is, bis (oxalato) a borate) , Lithium salt such as LiFSI (wherein FSI is bis (fluorosulfonyl) imide), lower aliphatic carboxylic acid lithium salt, LiAlCl ₄ , or the like, or a mixture of two or more thereof may be used. Among them, the electrolyte is preferably selected from the group consisting of LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) ₃ containing fluorine It is preferable to use at least one species.

Examples of the organic solvent contained in the electrolytic solution include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan- Carbonates such as 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethylether, 2,2,3,3-tetrafluoropropyldifluoromethylether, tetrahydrofuran, 2-methyltetrahydro Ethers such as furan; Esters such as methyl formate, methyl acetate and? -Butyrolactone; Nitriles such as acetonitrile and butyronitrile; Amides such as N, N-dimethylformamide and N, N-dimethylacetamide; Carbamates such as 3-methyl-2-oxazolidone; Sulfur compounds such as sulfolane, dimethylsulfoxide and 1,3-propanesultone, or those obtained by introducing a fluorine group into these organic solvents (one in which at least one hydrogen atom of the organic solvent is substituted with a fluorine atom) Can be used.

As the organic solvent, it is preferable to use a mixture of two or more of them. Among them, mixed solvents containing carbonates are preferable, and mixed solvents of cyclic carbonates and acyclic carbonates and mixed solvents of cyclic carbonates and ethers are more preferable. As the mixed solvent of the cyclic carbonate and the non-cyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethylmethyl carbonate is preferable. The electrolytic solution using such a mixed solvent has a wide operating temperature range and does not deteriorate even when charged and discharged at a high current rate and does not deteriorate well even if it is used for a long period of time and also contains natural graphite, The graphite material of the present invention has many features of being resistant to decomposition.

As the electrolytic solution, it is preferable to use an electrolytic solution containing a fluorine-containing lithium compound such as LiPF ₆ and an organic solvent having a fluorine-substituted group, because the obtained lithium secondary battery has high safety. A mixed solvent containing an ether having a fluorine-substituted group such as pentafluoropropylmethyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether and dimethyl carbonate has a high charge / Is more preferable because the capacity retention rate is high.

A solid electrolyte may be used instead of the electrolyte solution. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide-based polymer compound, a polyorganosiloxane chain, or a polymer compound containing at least one of polyoxyalkylene chains can be used. A so-called gel type in which a non-aqueous electrolyte solution is held in a polymer compound may also be used. Li ₂ S-SiS ₂ , Li ₂ S-GeS ₂ , Li ₂ SP ₂ S ₅ , Li ₂ SB ₂ S ₃ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li ₂ SO ₄ and Li ₂ S-GeS ₂ -P ₂ S _5, and mixtures of two or more of these may be used. By using such a solid electrolyte, the safety of the lithium secondary battery may be enhanced.

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

Since the positive electrode active material having the above-described constitution uses the lithium-containing composite metal oxide of the present embodiment described above, it is possible to suppress the side reaction occurring in the inside of the lithium secondary battery using the positive electrode active material.

In addition, since the positive electrode having the above-described structure has the positive electrode active material for a lithium secondary battery of the present embodiment described above, it is possible to suppress the side reaction occurring in the inside of the lithium secondary battery.

In addition, the lithium secondary battery having the above-described structure has the above-described positive electrode, and thus a lithium secondary battery suppressing side reactions generated in the battery in comparison with the conventional lithium secondary battery.

Example

Next, embodiments of the present invention will be described in more detail with reference to Examples.

In this example, the firing raw materials and the positive electrode active material for a lithium secondary battery were evaluated as follows.

(1) Composition analysis in positive electrode active material for lithium secondary battery (ICP emission analysis)

The composition of the positive electrode active material for a lithium secondary battery was analyzed by dissolving the metal oxide powder in hydrochloric acid and then using an inductively coupled plasma emission spectrometer (manufactured by Perkin Almer, Optima 7300DV). The chromium content as an impurity was calculated from the amount of chromium obtained above. The amount of lithium derived from lithium carbonate measured by the method described later was subtracted from the amount of lithium obtained as described above to obtain a lithium amount of the lithium metal composite oxide. Values of x, y, z and w in the general formula (I) were obtained from the amount of nickel, the amount of cobalt, the amount of manganese, the amount of M and the lithium amount of the lithium metal composite oxide obtained above.

(2) Determination of residual lithium carbonate in the positive electrode active material for lithium secondary battery (neutralization titration)

20 g of the positive electrode active material for a lithium secondary battery and 100 g of pure water were placed in a 100 ml beaker and stirred for 5 minutes. After stirring, the positive electrode active material for lithium secondary battery was filtered, 0.1 g / 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. The concentration of lithium carbonate remaining in the positive electrode active material for a lithium secondary battery was calculated from the following calculation based on an amount of hydrochloric acid of A ml when the pH was 8.3 ± 0.1 and an appropriate amount of hydrochloric acid when the pH was 4.5 ± 0.1 . In the following formula, the molecular weight of lithium carbonate is represented by the following formula: Li, 6.941, C; 12, O; 16.

Lithium carbonate concentration (%) = 0.1 x (B - A) / 1000 x 73.882 / (20 x 60/100) x 100

(3) Powder X-ray diffraction measurement of positive electrode active material for lithium secondary battery

Powder X-ray diffraction measurement of the positive electrode active material for a lithium secondary battery was carried out using a powder X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation, sample-horizontal type). A powdery X-ray diffraction pattern was obtained by filling the obtained positive electrode active material for a lithium secondary battery into a dedicated substrate and measuring it in the range of diffraction angle 2? = 10 to 90 using a Cu-K? Source. A peak within a range of 2? = 18.7 占 占 (hereinafter sometimes referred to as a peak A), a peak within a range of 2? = 44.6 占 (sometimes referred to as a peak B hereinafter) from the powder X-ray diffraction pattern, .

(Example 1)

[Mixing Process]

(Li ₂ CO ₃ ) and nickel cobalt manganese composite metal hydroxide (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) were weighed so that the molar ratio of Li: Ni: Co: Mn was 1.05: 0.55: 0.21: , And these were dry mixed to obtain a mixture. The content of lithium carbonate contained in the mixture was 29.7 mass% from the mixing ratio.

[Preliminary firing process]

Then, the mixture was placed in a rotary kiln in which the inner wall of the furnace was made of alumina, and fired at 790 DEG C for 2 hours.

[Main firing process]

Subsequently, the fired product obtained in the preliminary firing step was placed in the rotary kiln and fired at 900 ° C for 2 hours while introducing gas containing 21% by volume of oxygen into the furnace at a rate of 108.7 Nm ³ / h per 1 m ³ of furnace inner volume.

Thereafter, the mixture was cooled to room temperature, and the mixture was disintegrated to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 2 ppm. As a result of neutralization titration, the content of lithium carbonate was 0.25 mass%. In the general formula (I), x was 0.03, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.129 and 0.152, respectively.

(Example 2)

[Mixing Process]

(Li ₂ CO ₃ ) and nickel cobalt manganese composite metal hydroxide (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) were weighed so that the molar ratio of Li: Ni: Co: Mn was 2.20: 0.55: 0.21: , And these were dry mixed to obtain a mixture. The content of lithium carbonate contained in the mixture is 46.6 mass% from the mixing ratio.

[Preliminary firing process]

Then, the mixture was placed in a rotary kiln in which the inner wall of the furnace was made of alumina, and fired at 790 DEG 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 introducing gas containing 100% by volume of oxygen into the furnace at a rate of 150.1 Nm ³ / h per 1 m ³ of the furnace interior. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 4 ppm. As a result of neutralization titration, the lithium carbonate content was 0.92 mass%. In the general formula (I), x was 0.37, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.160 and 0.208, respectively.

(Example 3)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln in which the inner wall of the furnace was made of alumina, and fired at 850 ° C for 2 hours while introducing gas containing 21% by volume of oxygen into the furnace at a rate of 107.2 Nm ³ / h per 1 m ³ of furnace interior. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 10 ppm. As a result of neutralization titration, the content of lithium carbonate was 0.16% by mass. In the general formula (I), x was 0.03, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.152 and 0.185, respectively.

(Example 4)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln in which the inner wall of the furnace was made of alumina, and fired at 850 ° C for 2 hours while introducing gas containing 60% by volume of oxygen into the furnace at a rate of 107.2 Nm ³ / h per 1 m ³ of furnace interior. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 31 ppm. As a result of neutralization titration, the content of lithium carbonate was 0.19% by mass. In the general formula (I), x was 0.04, y was 0.21, z was 0.24, and w was 0. As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.153 and 0.194, respectively.

(Example 5)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln in which the inner wall of the furnace was made of alumina, and fired at 850 ° C for 2 hours while introducing gas containing 100% by volume of oxygen into the furnace at a flow rate of 46.5 Nm ³ / h per 1 m ³ of furnace interior. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 49 ppm. As a result of neutralization titration, the content of lithium carbonate was 0.15% by mass. In the general formula (I), x was 0.04, y was 0.22, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.152 and 0.178, respectively.

(Example 6)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln where the inner wall of the furnace was made of alumina, and fired at 850 ° C for 2 hours while introducing gas containing 21% by volume of oxygen into the furnace at a rate of 46.5 Nm ³ / h per 1 m ³ of furnace interior. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 20 ppm. As a result of neutralization titration, the content of lithium carbonate was 0.51% by mass. In the general formula (I), x was 0.04, y was 0.21, z was 0.24, and w was 0. As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.149 and 0.182, respectively.

(Example 7)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln in which the inner wall of the furnace was made of alumina, and fired at 850 ° C for 2 hours while passing a gas containing 21% by volume of oxygen at 17.9 Nm ³ / h per 1 m ³ of furnace inner volume. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 19 ppm. As a result of neutralization titration, the content of lithium carbonate was 0.90 mass%. In the general formula (I), x was 0.03, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.161 and 0.200, respectively.

(Example 8)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln in which the inner wall of the furnace was made of alumina, and fired at 850 ° C for 2 hours while passing a gas containing 100% by volume of oxygen at 17.9 Nm ³ / h per 1 m ³ of furnace inner volume. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 45 ppm. As a result of neutralization titration, the content of lithium carbonate was 0.53% by mass. In the general formula (I), x was 0.03, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.151 and 0.184, respectively.

(Comparative Example 1)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln in which the inner wall of the furnace was Inconel, and fired at 730 ° C for 2 hours while passing a gas containing 21% by volume of oxygen through 22.6 Nm ³ / h per 1 m ³ of furnace inner volume. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 55 ppm. As a result of neutralization titration, the content of lithium carbonate was 5.31 mass%. In the general formula (I), x was 0.02, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and 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 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln in which the inner wall of the furnace was Inconel, and fired at 730 ° C for 4 hours while passing a gas containing 21% by volume of oxygen through 22.6 Nm ³ / h per 1 m ³ of furnace interior. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 60 ppm. As a result of neutralization titration, the content of lithium carbonate was 3.43 mass%. In the general formula (I), x, y, and z were 0.03, 0.22, 0.24, and 0, respectively. As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.415 and 0.578, respectively.

(Comparative Example 3)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, into the fired product in a rotary kiln furnace the inner wall of SUS310, while a gas containing 21% by volume oxygen furnace internal volume 1 ㎥ aeration 22.6 Nm ³ / h per, it was carried out for 5 hours and baked at 730 ℃. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 320 ppm. As a result of neutralization titration, the content of lithium carbonate was 1.13% by mass. In the general formula (I), x was 0.02, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.214 and 0.261, respectively.

(Comparative Example 4)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was charged in a toe box whose inner wall was alumina, and a gas containing 21% by volume of oxygen was passed through the roller hearth kiln at a rate of 29.7 Nm ³ / h per 1 m ³ of the inner volume, Respectively. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 10 ppm. As a result of neutralization titration, the content of lithium carbonate was 1.01% by mass. In the general formula (I), x was 0.04, y was 0.21, z was 0.24, and w was 0. As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.225 and 0.278, respectively.

(Comparative Example 5)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was filled in a toe box whose inner wall was made of alumina, and a gas containing 21% by volume of oxygen was passed through a roller hearth kiln at a rate of 29.7 Nm ³ / h per 1 m ³ of the inner volume, Respectively. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. The positive electrode active material for a lithium secondary battery was subjected to neutralization titration, and as a result, the lithium carbonate content was 0.67 mass%. In the general formula (I), x was 0.02, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.129 and 0.150, respectively.

(Comparative Example 6)

[Mixing Process]

(Li ₂ CO ₃ ) and nickel cobalt manganese composite metal hydroxide (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) were weighed so that the molar ratio of Li: Ni: Co: Mn was 3.00: 0.55: 0.21: , And these were dry mixed to obtain a mixture. The content of lithium carbonate contained in the mixture was 54.3 mass% from the mixing ratio. In the general formula (I), x was 0.50, y was 0.21, z was 0.24, and w was 0. [ The mixture was fired at 850 ° C for 2 hours while passing a gas containing 21% by volume of oxygen in a rotary kiln having an inner wall of alumina at a rate of 17.9 Nm ³ / h per 1 m ³ of the furnace interior. However, the mixture and the sintered material adhered to the wall of the core tube, so that it was impossible to discharge it.

(Reference example)

[Mixing Process]

A mixture was obtained in the same manner as in Example 1 above.

[Preliminary firing process]

The mixture described in Example 1 was placed in a rotary kiln where the inner wall of the furnace was Inconel, and firing was performed at 730 占 폚 for 2 hours.

[Main firing process]

Subsequently, the fired product was placed in a rotary kiln in which the inner wall of the furnace was made of alumina, and fired at 850 ° C for 4 hours while passing a gas containing 21% by volume of oxygen at 17.9 Nm ³ / h per 1 m ³ of furnace inner volume. Thereafter, the mixture was cooled to room temperature, and the mixture was pulverized to obtain a positive electrode active material for a lithium secondary battery. As a result of ICP emission analysis for the positive electrode active material for a lithium secondary battery, the chromium content was 13 ppm. As a result of neutralization titration, the content of lithium carbonate was 0.10% by mass. In the general formula (I), x was 0.02, y was 0.21, z was 0.24, and w was 0. [ As a result of powder X-ray diffraction, the half widths of peaks A and B were 0.149 and 0.183, respectively.

Tables 1 to 3 below summarize the conditions and results of the examples, the comparative examples and the reference examples. In the table, RK denotes a rotary kiln, and RHK denotes a roller haul kiln.

As in the results shown in Tables 1 to 3, Examples 1 to 8 to which the present invention was applied can produce a positive active material having a small peak half width, that is, a high crystallinity at a short firing time. Further, in Examples 1 to 8 to which the present invention was applied, the content of chromium was low.

On the other hand, in Comparative Examples 1 to 3 in which the present firing step was carried out in a rotary kiln made of metal, the content of chromium was large and the peak half width was large. In Comparative Example 5, the peak half width was large in Comparative Example 4 in which the roller was used in the firing process and in the firing time of 2 hours in the firing process, but 10 hours in the firing time was required in Comparative Example 5 .

Reference Example 1 was carried out for 4 hours using a rotary kiln made of a nonmetallic material as the inner wall of the furnace, which is the portion where the mixture was contacted with the mixture. Comparing Reference Example 1 and Example 1, the peak half width was about the same. In other words, a positive active material with high crystallinity could be produced with a short firing time (2 hours).

1: Separator,
2: positive electrode,
3: Negative electrode,
4: electrode group,
5: Battery can,
6: electrolyte,
7: Top insulator,
8: Bee Sphere,
10: lithium secondary battery,
21: positive lead,
31: negative electrode lead,
40: rotary kiln,
41: the inner wall of the furnace,
42: Core tube,
50: Fired raw material

Claims (8)

A mixing step of mixing a lithium compound and a positive electrode active material precursor to obtain a mixture,
And a main firing step of firing the mixture using a rotary kiln, the method comprising:
The content of the lithium compound contained in the mixture is more than 0 and 50 mass% or less with respect to the total mass of the mixture,
Wherein the furnace inner wall of the rotary kiln is made of a non-metallic material. The method according to claim 1,
Wherein the main firing step is performed at a temperature of 750 ° C or more and 1000 ° C or less. 3. The method according to claim 1 or 2,
Wherein the positive electrode active material for a lithium secondary battery comprises a lithium metal composite oxide represented by the following general formula (I).
_{Li [Li x (Ni (1} -yzw) Co y Mn z M w) 1-x] O 2 ... (I)
(In the formula (I), -0.1? X? 0.2, 0 <y? 0.5, 0? Z? 0.8, 0? W? 0.1, y + z + And at least one element selected from the group consisting of Al, W, B, Mo, Nb, Zn, Sn, Zr, 4. The method according to any one of claims 1 to 3,
Wherein the preliminary firing step is performed after the mixing step and before the main firing step, the firing is performed at a temperature lower than the firing temperature of the main firing. 5. The method according to any one of claims 1 to 4,
Wherein either one or both of the main firing step and the preliminary firing step is carried out by passing an oxygen-containing gas at a flow rate of 15 Nm ³ / h / m ³ or more. 6. The method of claim 5,
Wherein the oxygen concentration in the oxygen-containing gas is 21 vol% or more based on the total volume of the oxygen-containing gas. 7. The method according to any one of claims 1 to 6,
Wherein the content of chromium in the positive electrode active material for a lithium secondary battery is 50 ppm or less based on the total mass of the positive electrode active material for the lithium secondary battery. 8. The method according to any one of claims 1 to 7,
Wherein a content of lithium carbonate contained in the positive electrode active material for a lithium secondary battery is 1.0 mass% or less based on the total mass of the positive electrode active material for a lithium secondary battery.

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