JP6996262B2 - A method for producing lithium hydroxide for producing a lithium nickel composite oxide, a raw material for lithium hydroxide for producing a lithium nickel composite oxide, and a method for producing a lithium nickel composite oxide. - Google Patents

Description

The present invention relates to a method for producing lithium hydroxide for producing a lithium nickel composite oxide, a method for producing lithium hydroxide for producing a lithium nickel composite oxide, and a method for producing a lithium nickel composite oxide.

In recent years, with the rapid expansion of small electronic devices such as mobile phones and notebook computers, the demand for lithium secondary batteries as a chargeable and dischargeable power source has been rapidly increasing. As a positive electrode active material used for a positive electrode of a lithium secondary battery, a lithium nickel composite oxide is widely used together with a lithium cobalt composite oxide.

The lithium nickel composite oxide has an advantage that a high capacity battery can be obtained at a lower cost than the lithium cobalt composite oxide.

However, the lithium-nickel composite oxide is usually produced by mixing a lithium compound and a nickel compound and firing them. However, since the charge / discharge characteristics differ depending on the production conditions, these production conditions should be appropriately controlled. There is a problem that it is difficult to obtain sufficient charge / discharge characteristics.

Further, since the decomposition temperature of the lithium nickel composite oxide is lower than that of the lithium cobalt composite oxide, the temperature at the time of synthesis cannot be raised, and the firing time at the time of synthesis is longer than that of the lithium cobalt composite oxide. There is also the problem of poor productivity.

As the lithium compound and the nickel compound which are the raw materials for producing the lithium-nickel composite oxide, typically, lithium hydroxide and a nickel composite hydroxide or a nickel composite oxide to which various elements are added are used, respectively. Can be mentioned.

Many proposals have already been made regarding a method for synthesizing a lithium-nickel composite oxide by mixing and firing this lithium hydroxide with a nickel composite hydroxide or a nickel composite oxide.

For example, in Patent Document 1, an alkaline solution is added to a mixed aqueous solution of a cobalt salt and a nickel salt, and the hydroxide of cobalt and nickel is co-precipitated to obtain a composite hydroxide of cobalt and nickel. A method for producing a positive electrode active material for a lithium secondary battery, which comprises mixing with a lithium compound such as lithium hydroxide and firing the mixture, is disclosed.

Further, in Patent Document 2, Ni _{1-ab-c-d Coa} M _1b M _2c M _3d (OH) ₂ produced by the coprecipitation method and a Li compound are mixed and mixed in an atmosphere or an oxygen atmosphere. It is characterized by firing at 480-850 ° C or at 480-630 ° C for 15-40 hours and then crushing, and then firing at 700-850 ° C for 3-10 hours in the same atmosphere. A method for manufacturing a positive electrode material for a lithium secondary battery is disclosed.

Although these patent documents specify the raw material composition, the firing temperature range, the firing time, etc., they do not disclose the manufacturing conditions in consideration of mass production. There is a problem that stable charge / discharge characteristics cannot be obtained in the produced positive electrode active material.

On the other hand, Patent Document 3 describes a method in which a lithium salt and a nickel salt are mixed so as to have a Li / Ni molar ratio of at least 1 and then fired to obtain LiNiO ₂ for a positive electrode material. Disclosed is a method for producing a positive electrode material for a lithium secondary battery, which comprises firing the mixture of 1 in air and / or oxygen containing 1% or more of ozone at 500 ° C. to 1000 ° C. for 10 hours or more.

Further, Patent Document 3 also discloses an example in which an anhydride is used as lithium hydroxide. Specifically, an example is disclosed in which a mixture of nickel hydroxide and anhydrous lithium hydroxide is heated and fired in an atmosphere adjusting furnace to produce a positive electrode active material for a lithium secondary battery.

However, Patent Document 3 merely discloses an example in which anhydrous lithium hydroxide is used as a raw material, and no studies have been made on the specific characteristics of the anhydrous lithium hydroxide, the production method, and the like. Not done.

Further, as a method for anhydrousizing lithium hydroxide monohydrate, Patent Document 4 is characterized in that lithium hydroxide monohydrate is anhydrousized by heating it to a core tube temperature of 150 ° C. or higher using a rotary kiln. A method for anhydrousizing lithium hydroxide monohydrate is disclosed. In Patent Document 4, regarding the atmosphere at the time of heating, lithium hydroxide may not be converted to lithium carbonate, and examples thereof include the atmosphere and an inert gas such as nitrogen and argon.

However, in Patent Document 4, by using a rotary kiln, the charged lithium hydroxide monohydrate is gradually heated in part, so that a large amount of water is not temporarily generated, and it is in the form of powder or granules. It is an invention to obtain the lithium hydroxide anhydrous salt of. Therefore, the details of the conversion of lithium hydroxide to lithium carbonate have not been studied at all.

Patent Document 5 describes lithium hydroxide having a carbon content of 1% by mass or less and a mass reduction rate of 5% by mass or less when held in vacuum at 200 ° C. for 8 hours, and a nickel composite oxide. Discloses a method for producing a lithium-nickel composite oxide which is mixed and fired.

According to Patent Document 5, it is possible to stably obtain a lithium nickel composite oxide having excellent charge / discharge characteristics even in mass production on an industrial scale, but there is room for improvement in productivity and stability. ..

As described above, in actual mass production on an industrial scale, it has not yet been possible to stably produce a positive electrode active material for a lithium secondary battery having sufficient charge / discharge characteristics.

Japanese Unexamined Patent Publication No. 8-222220 JP-A-2002-170562 Japanese Unexamined Patent Publication No. 8-180863 Japanese Unexamined Patent Publication No. 2006-265023 Japanese Unexamined Patent Publication No. 2011-178584

Therefore, in view of the problems of the above-mentioned prior art, in one aspect of the present invention, it is used as a raw material for producing a lithium nickel composite oxide, and it is possible to suppress variations in the quality of the lithium nickel composite oxide even in mass production on an industrial scale. It is an object of the present invention to provide a possible method for producing lithium hydroxide for producing a lithium-nickel composite oxide.

According to one aspect of the present invention in order to solve the above problems.
It is a method for producing lithium hydroxide used when producing a lithium-nickel composite oxide by mixing lithium hydroxide and a nickel compound and firing them.
Lithium nickel having a drying step of obtaining anhydrous lithium hydroxide having a carbon content of 0.3% by mass or less by heating while flowing lithium hydroxide hydrate in an atmosphere where the partial pressure of carbon dioxide gas is 10 Pa or less. Provided is a method for producing lithium hydroxide for producing a composite oxide.

According to one aspect of the present invention, it is used as a raw material for producing a lithium nickel composite oxide, and it is possible to suppress variations in the quality of the lithium nickel composite oxide even in mass production on an industrial scale. A method for producing lithium hydroxide for use can be provided.

FIG. 3 is a schematic cross-sectional view of the rolling stirrer used in Example 1 according to the present invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments and does not deviate from the scope of the present invention. Can be modified and substituted in various ways.
[Manufacturing method of lithium hydroxide for manufacturing lithium nickel composite oxide]
First, a configuration example of a method for producing lithium hydroxide for producing a lithium-nickel composite oxide of the present embodiment (hereinafter, also simply referred to as “lithium hydroxide”) will be described.

The method for producing lithium hydroxide for producing a lithium-nickel composite oxide of the present embodiment is a method for producing lithium hydroxide used when producing a lithium-nickel composite oxide by mixing lithium hydroxide and a nickel compound and firing them. Regarding. The method for producing lithium hydroxide for producing a lithium-nickel composite oxide according to the present embodiment is to heat the lithium hydroxide hydrate while flowing it in an atmosphere where the partial pressure of carbon dioxide gas is 10 Pa or less to obtain a carbon content. Can have a drying step to obtain anhydrous lithium hydroxide in an amount of 0.3% by mass or less.

Lithium hydroxide has the property of combining with carbonic acid in the air (hereinafter, may be referred to as "carbonation") to form lithium carbonate.

According to the studies by the inventors of the present invention, carbon contained in lithium hydroxide exists as, for example, lithium carbonate, but depending on its content, lithium hydroxide and a nickel compound such as a nickel composite oxide may be used. Interferes with the reaction when producing a lithium-nickel composite oxide by mixing and firing. For example, when a nickel oxide is used as the nickel compound, a lithium nickel composite oxide is produced by the following reaction formula (1).

2NiO + 2LiOH + 1 / 2O ₂ → 2LiNiO ₂ + H ₂ O ・ ・ ・ (1)
The firing temperature of the lithium nickel composite oxide is generally lower than the firing temperature of the lithium cobalt composite oxide. Therefore, when lithium hydroxide contains lithium carbonate, which has a high reaction temperature with the nickel compound, lithium carbonate inhibits the synthetic reaction according to the reaction formula (1). Therefore, if the obtained positive electrode active material made of the lithium nickel composite oxide is used as the positive electrode material of the lithium secondary battery, the battery capacity of the lithium secondary battery will decrease.

Further, the inventors of the present invention have stated that carbon in lithium hydroxide is one of the factors that change the physical properties of the obtained lithium-nickel composite oxide, and the variation in the carbon content of lithium hydroxide is the final product. It has been found that it causes quality variation of the lithium-nickel composite oxide.

Therefore, in the method for producing lithium hydroxide of the present embodiment, the carbon content in the obtained lithium hydroxide is 0.3% by mass or less, preferably 0.27% by mass or less, which is that of the conventional lithium nickel composite oxide. It is reduced to more than lithium hydroxide used as a raw material. Therefore, it is possible to prevent the reaction during the production of the lithium nickel composite oxide from being hindered, and the lithium secondary battery using the lithium nickel composite oxide produced using the lithium hydroxide as the positive electrode material. Can stably obtain a high battery capacity.
In the method for producing lithium hydroxide of the present embodiment, the lower limit of the carbon content in the obtained lithium hydroxide is not particularly limited, and the carbon content of lithium hydroxide obtained by the method for producing lithium hydroxide of the present embodiment is not particularly limited. The amount can be, for example, 0 or more.

When evaluating the carbon content of lithium hydroxide, when sampling is performed at only one location, it is preferable that the carbon content of the sampled sample satisfies the above range. When sampling is performed at two or more locations, for example, three or more locations and 10 or less locations, the carbon content of each sampled sample is evaluated, and the average value of the sampled samples falls within the above range. It is preferable to satisfy.

Further, since the lithium hydroxide obtained by the method for producing lithium hydroxide of the present embodiment is suppressed to a low carbon content range, the variation in carbon content is inevitably small. Therefore, it is possible to suppress variations in the quality of the lithium-nickel composite oxide produced using the lithium hydroxide.

In order to further reduce the variation in the battery capacity of the lithium secondary battery using the lithium nickel composite oxide produced by using the lithium hydroxide obtained by the method for producing lithium hydroxide of the present embodiment as the positive electrode material, further. It is preferable to control the carbon content within a certain range. The term “carbon content within a certain range” as used herein means, for example, variation in carbon content between multiple sampling points in the same lot of manufactured lithium hydroxide, variation in carbon content among multiple lots, and the like. That is, it means that there is almost no variation and it is within a certain range.

The lithium hydroxide obtained by the method for producing lithium hydroxide of the present embodiment preferably has a carbon content variation of 0.10% by mass or less, and more preferably 0.05% by mass or less.
Since it is preferable that the variation in the carbon content of the lithium hydroxide obtained by the method for producing lithium hydroxide of the present embodiment is 0 or its vicinity, the variation in the carbon content of the lithium hydroxide is, for example, 0. The above can be done.

Specifically, for example, when one lot of lithium hydroxide produced at 2t / lot is sampled at any different arbitrary locations, for example, 3 or more and 10 or less, and evaluation is performed, the variation in carbon content is described above. It is preferably within the range. In addition, when the average value of the carbon content of each lot is compared between 2 lots or more and 5 lots or less, it is more preferable that the variation in carbon content is within the above range.

By controlling the carbon content of the produced lithium hydroxide within the range of, for example, 0.10% by mass or more and 0.20% by mass or less, that is, by setting the range of variation to within 0.10% by mass. It is possible to further reduce the variation in quality of the lithium nickel composite oxide produced by using lithium hydroxide.

As described above, when the carbon content of the produced lithium hydroxide is controlled to be in the range of, for example, 0.10% by mass or more and 0.20% by mass or less, the carbon content in the produced lithium hydroxide is, for example, In the case of about 0.01% by mass, it is preferable to promote carbonization to adjust the carbon content. The carbon content can be controlled, for example, by the atmosphere of the drying process.

Lithium hydroxide hydrate as a raw material, for example, lithium hydroxide monohydrate, generally contains about 0.01% by mass to 0.15% by mass of carbon. In order to convert anhydrous lithium hydroxide from lithium hydroxide monohydrate, if water contained in about 42% by mass is removed, the carbon content of anhydrous lithium hydroxide will be about 0.02% by mass to 0.26% by mass. .. In order to stabilize the quality of the lithium-nickel composite oxide, it is necessary to have a carbon content of 0.3% by mass or less for anhydrous lithium hydroxide, and the lithium hydroxide hydrate is dehydrated and dried. In the drying process, it is important to suppress carbonation.
The carbon content of the lithium hydroxide hydrate as a raw material is not particularly limited, but the carbon content is inevitably increased by removing water as described above, so that the carbon content is, for example, 0.2% by mass or less. It is preferable to use lithium hydroxide hydrate. In particular, it is more preferable to use 0.15% by mass or less of lithium hydroxide hydrate as a raw material.
Since the lithium hydroxide hydrate used as a raw material preferably does not contain carbon, lithium hydroxide hydrate having a carbon content of, for example, 0 or more can be used as the raw material.

Therefore, in the drying step of the method for producing lithium hydroxide of the present embodiment, the lithium hydroxide hydrate is heated while flowing. By flowing, it is possible to uniformly heat the lithium hydroxide hydrate in a short time, suppress carbonation, and dehydrate in a short time.

As described above, in the drying step of the method for producing lithium hydroxide of the present embodiment, since the lithium hydroxide hydrate is fluidized, the lithium hydroxide particles aggregate during heating and the coarse lithium hydroxide aggregates. The formation of powder can be suppressed.

Further, in the process of heating the lithium hydroxide hydrate, the water generated from the lithium hydroxide hydrate causes the lithium hydroxide to be placed in a water-rich environment, but in a water-rich environment. , Lithium hydroxide is easily carbonated. For this reason, in a heating method in which a part of the sample lithium hydroxide hydrate is sequentially heated and heated to generate a large temperature gradient in the lithium hydroxide hydrate, the lithium hydroxide has water content. Since it is left in a high temperature state for a long time, the suppression of carbonation becomes insufficient.

On the other hand, according to the method for producing lithium hydroxide of the present embodiment, the lithium hydroxide hydrate can be dehydrated in a short time in the drying step, so that the progress of carbonation can be particularly suppressed. can.

In the drying step of the method for producing lithium hydroxide of the present embodiment, the difference between the maximum temperature and the minimum temperature in the lithium hydroxide hydrate, that is, the temperature, in a steady state after heating is started and the set temperature is reached. The gradient is, for example, preferably 120 ° C. or lower, more preferably 100 ° C. or lower, and even more preferably 80 ° C. or lower. The lower limit of the temperature gradient in the lithium hydroxide hydrate in the steady state in the drying step is not particularly limited, but it can be set to 0 ° C. or higher because a smaller temperature gradient is preferable.

In the drying step of the method for producing lithium hydroxide of the present embodiment, the means for flowing the lithium hydroxide hydrate is not particularly limited, but various stirrers can be used, for example. In particular, a rolling stirrer can be preferably used. The rolling stirrer is provided with one or more stirring means, and the sample in the stirrer can be stirred by rotating the stirring means by the power applied by the rotating means such as a motor. Means a device. Then, by providing the rolling stirrer with a heating means, the sample can be heated while flowing.

The heating means may be any means that can heat the flowing lithium hydroxide hydrate, and is not particularly limited. For example, it has a jacket structure and is heated by supplying a heat medium such as steam into the jacket. The means to do so can be mentioned. When the heating means having the above-mentioned jacket structure is used, it is preferable to arrange the heating means so that the lithium hydroxide hydrate flowing by the heating means can be heated. For example, a part or all of a wall portion or the like that defines a region for stirring an object to be agitated in the stirrer can be formed by the heating means.

Examples of the means for flowing the lithium hydroxide hydrate include not only the method using a stirrer as described above, but also a means for drying the lithium hydroxide hydrate while flowing it by an air flow. In this case, by heating the air flow to be supplied, the flow of lithium hydroxide hydrate and the heating can be performed at the same time.

In the drying step, the atmosphere for flowing and heating lithium hydroxide is an atmosphere having a partial pressure of carbon dioxide gas of 10 Pa or less, preferably an atmosphere having a partial pressure of carbon dioxide gas of 5 Pa or less. Lithium hydroxide easily produces lithium carbonate by reacting with carbon dioxide gas. Therefore, in the drying step, the carbon dioxide concentration in the atmosphere is controlled so that the partial pressure of the carbon dioxide gas is 10 Pa or less, and carbonation is suppressed, so that the production of excess lithium carbonate can be suppressed.

However, as described above, for example, when the carbon content of lithium hydroxide is controlled within a certain range, that is, the variation in the carbon content between a plurality of lots of manufactured lithium hydroxide is controlled within a certain range. In this case, it is preferable to adjust the partial pressure of carbon dioxide gas within the above range to generate a small amount of lithium carbonate. For example, when the carbon content of lithium hydroxide hydrate is low and anhydrous lithium hydroxide is below the lower limit of the target carbon content range, a carbon dioxide gas-containing gas such as air is used as an atmosphere in the drying process. It is preferable to introduce a small amount.

The atmosphere in the drying step is not particularly limited as long as the partial pressure of carbon dioxide gas is 10 Pa or less, but for example, an atmosphere selected from an air atmosphere, a nitrogen atmosphere, and a vacuum atmosphere having a partial pressure of carbon dioxide gas of 10 Pa or less can be used. It can be preferably used. In particular, it is more preferable to use a vacuum atmosphere in which the partial pressure of carbon dioxide gas is 10 Pa or less.

An air or nitrogen atmosphere having a partial pressure of carbon dioxide gas of 10 Pa or less can be easily obtained by passing air or nitrogen through a carbon dioxide gas adsorbent such as calcium oxide.

When the atmosphere in the drying step is a vacuum atmosphere, the heating means for heating the flowing lithium hydroxide hydrate has a jacket structure as described above, and steam (heated steam) or the like is contained in the jacket. It is preferable to use a means for heating by supplying the heat medium of.

This is because, for example, by flowing the lithium hydroxide hydrate in the region surrounded by the heated jacket, the contact between the lithium hydroxide hydrate and the jacket constituting the heating means is increased, and the vacuum atmosphere is reached. This is because it is efficiently heated and can be dehydrated in a short time.

The jacket is preferably heated by supplying and circulating a heated heat medium in the jacket. By circulating the heat medium inside the jacket, the inside of the jacket can be heated more uniformly. Further, the heat medium is preferably water vapor. This is because steam is easier to handle than other heat media and can be heated to a temperature sufficient for drying.

Further, when the atmosphere in the drying step is a vacuum atmosphere as described above, for example, a rolling stirrer can be used as a method for flowing the lithium hydroxide hydrate as described above. That is, in the drying step, it is preferable to flow the lithium hydroxide hydrate in vacuum using a rolling stirrer. In particular, the rolling stirrer has a heating means provided with the above-mentioned jacket structure, and heating in the drying step can be performed by supplying and circulating a heat medium such as heated steam in the jacket. preferable. Therefore, when the atmosphere in the drying step is a vacuum atmosphere, the means for flowing and heating the lithium hydroxide hydrate, that is, the heating / drying device, is, for example, a rolling stirrer having a heating means having a jacket structure. Can be preferably used.

In the drying step, the lithium hydroxide hydrate is dehydrated and dried, that is, water of crystallization and adsorbed water are removed, and the heating temperature in the drying step is preferably in the range of 80 ° C. or higher and 250 ° C. or lower, more preferably. Is in the range of 100 ° C. or higher and 200 ° C. or lower.

As described above, when steam is used as a heat medium, it is preferable to heat the drying step at a temperature of 100 ° C. or higher and 150 ° C. or lower from the viewpoint of ease of operation and simplification of equipment.

In the drying step, the water of crystallization of lithium hydroxide hydrate is sufficiently dehydrated by heating and dehydrating in the above temperature range, and the time required for dehydration is shortened, so that the carbon of anhydrous lithium hydroxide obtained can be obtained. The content can be further reduced. In addition, since the cooling time after heating can be shortened, carbonation during cooling can be suppressed and productivity can be improved.
The heating time is not particularly limited. For example, considering the amount of lithium hydroxide hydrate to be used in the drying step, the state of lithium hydroxide hydrate, the heating temperature, etc., the lithium hydroxide hydrate is sufficiently converted to anhydrous lithium hydroxide. For example, a time can be selected in which the water content of anhydrous lithium hydroxide is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 3% by mass or less. If the state of lithium hydroxide hydrate is stable, the operating conditions such as the amount of lithium hydroxide hydrate and the heating temperature can be kept constant, and the drying time can be determined by a preliminary test.

When water is adsorbed on the anhydrous lithium hydroxide after drying, the production of lithium carbonate is promoted as described above. Therefore, it is preferable that the anhydrous lithium hydroxide after drying keeps a dry state. In an industrial scale mass production process, it is preferable to keep the lithium hydroxide dry by storing it under controlled moisture and carbon dioxide partial pressure.
[Lithium hydroxide for manufacturing lithium nickel composite oxide]
Next, a configuration example of lithium hydroxide for producing a lithium-nickel composite oxide of the present embodiment (hereinafter, also simply referred to as “lithium hydroxide”) will be described.

The lithium hydroxide of the present embodiment is lithium hydroxide used for producing a lithium-nickel composite oxide by mixing lithium hydroxide and a nickel compound and firing them, and has a carbon content of 0.3 mass. % Or less anhydrous lithium hydroxide.

Since the lithium hydroxide of the present embodiment can be produced by, for example, the above-mentioned method for producing lithium hydroxide, some overlapping description will be omitted.

As described above, the lithium hydroxide of the present embodiment can have a carbon content of 0.3% by mass or less, preferably 0.27% by mass or less. As described above in the method for producing lithium hydroxide, the lithium hydroxide of the present embodiment has a carbon content of 0.3% by mass or less in lithium hydroxide and is used as a raw material for a conventional lithium nickel composite oxide. The carbon content is reduced more than that of lithium hydroxide. Therefore, it is possible to prevent the reaction during the production of the lithium nickel composite oxide from being hindered, and the lithium secondary battery using the lithium nickel composite oxide produced using the lithium hydroxide as the positive electrode material. Can stably obtain a high battery capacity.
The lower limit of the carbon content in the lithium hydroxide of the present embodiment is not particularly limited, and the carbon content of the lithium hydroxide of the present embodiment can be, for example, 0 or more.

When evaluating the carbon content of lithium hydroxide, when sampling is performed at only one location, it is preferable that the carbon content of the sampled sample satisfies the above range. When sampling is performed at two or more locations, for example, three or more locations and 10 or less locations, the carbon content of each sampled sample is evaluated, and the average value of the sampled samples falls within the above range. It is preferable to satisfy.

Further, since the lithium hydroxide of the present embodiment is suppressed to a range where the carbon content is low, the variation in the carbon content is inevitably small. Therefore, it is possible to suppress variations in the quality of the lithium-nickel composite oxide produced using the lithium hydroxide.

Further, in order to further reduce the variation in the battery capacity of the lithium secondary battery using the lithium nickel composite oxide produced by using the lithium hydroxide of the present embodiment as the positive electrode, the carbon content should be kept within a certain range. It is preferable to control it. The term "carbon content within a certain range" as used herein means that, for example, the carbon content varies between a plurality of lots of produced lithium hydroxide, that is, there is almost no variation and the carbon content is within a certain range.

The lithium hydroxide of the present embodiment preferably has a variation in carbon content of 0.10% by mass or less, and more preferably 0.05% by mass or less.
Since the variation in the carbon content of the lithium hydroxide of the present embodiment is preferably 0 or its vicinity, the variation in the carbon content of the lithium hydroxide can be, for example, 0 or more.

Specifically, for example, when one lot of lithium hydroxide manufactured with 2 t / lot of manufactured lithium hydroxide is sampled at arbitrary multiple different locations, for example, 3 or more and 10 or less locations, and evaluated, the carbon content is contained. It is preferable that the amount of variation is within the above range. In addition, when the average value of the carbon content of each lot is compared between 2 lots or more and 5 lots or less, it is more preferable that the variation in carbon content is within the above range.
By controlling the carbon content of lithium hydroxide of the present embodiment within the range of, for example, 0.10% by mass or more and 0.20% by mass or less, the variation in the quality of the lithium nickel composite oxide can be further reduced. Can be done.

As described above, when the carbon content of lithium hydroxide is controlled in the range of, for example, 0.10% by mass or more and 0.20% by mass or less, the carbon content in the lithium hydroxide produced is, for example, 0. In the case of about 01% by mass, it is preferable to promote carbonization to adjust the carbon content. The carbon content can be controlled, for example, by the atmosphere of the drying step of the above-mentioned method for producing lithium hydroxide.

By the way, general anhydrous lithium hydroxide contains lithium hydroxide hydrate as an impurity, and contains water as water of crystallization or adsorbed water.

However, in the process of producing the lithium nickel composite oxide, the water present as water of crystallization or adsorbed water in the mixed raw material lithium hydroxide is released as water vapor at the time of firing. Then, the inside of the mixture becomes a positive pressure state, oxygen in the mixture is expelled, oxygen diffusion into the mixture is further inhibited, and the progress of the reaction formula (1) mentioned in the method for producing a lithium hydroxide is inhibited. .. Therefore, depending on the content of water such as the above-mentioned crystalline water of lithium hydroxide, when the obtained lithium nickel composite oxide is used in a lithium secondary battery, the battery capacity is further lowered and the battery performance is further deteriorated. ..

Therefore, the lithium hydroxide of the present embodiment preferably has a water content of 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. By reducing the water content, higher reactivity with the nickel compound can be obtained.

The lower limit of the water content is not particularly limited, but it is preferable that the water content is low, so that it can be, for example, 0% by mass or more.

In lithium hydroxide having a high water content, the carbon dioxide gas contained in the atmosphere is adsorbed on the lithium hydroxide, and lithium carbonate is easily generated. From this viewpoint as well, it is preferable to sufficiently reduce the water content of lithium hydroxide.

The lithium hydroxide of the present embodiment described above is anhydrous lithium hydroxide, and since the carbon content is suppressed, it has high reactivity with a nickel compound when producing a lithium nickel composite oxide. There is. Therefore, the lithium secondary battery using the lithium nickel composite oxide obtained by using the lithium hydroxide of the present embodiment as the positive electrode material can have a high battery capacity.
[Manufacturing method of lithium nickel composite oxide]
Next, a configuration example of the method for producing the lithium nickel composite oxide of the present embodiment will be described.

The composition of the lithium-nickel composite oxide finally obtained by the method for producing a lithium-nickel composite oxide of the present embodiment is not particularly limited and may be any composition.

However, the general formula: Li _x Ni _{(1-y-z) My} N _z O _{2 + α} (in the formula, M is at least one selected from Co and Mn, and N is at least selected from Al and Ti. 1 type, 0.95 ≦ x ≦ 1.15, 0.05 ≦ y ≦ 0.35, 0.005 ≦ z ≦ 0.8, −0.2 ≦ α ≦ 0.2). It is preferably a lithium nickel composite oxide represented.

As the lithium nickel composite oxide, composite oxides having various compositions have been proposed, but the lithium nickel composite oxide represented by the above general formula is preferable in that it has excellent battery characteristics, and further, the present embodiment. By applying the method for producing a lithium-nickel composite oxide according to the above, it is possible to obtain a positive electrode active material having excellent charge / discharge characteristics stably even in a mass production process on an industrial scale.

Here, the M element of the general formula is Co and / or Mn, and by setting y in the above range, cycle characteristics are suppressed while suppressing a decrease in battery capacity when used as a positive electrode material for a lithium secondary battery. Can be improved. It is particularly preferable that y is in the range of 0.1 or more and 0.2 or less.

Further, the N elements of the general formula are Al and / or Ti, and by setting z in the above range, thermal stability is suppressed while suppressing a decrease in battery capacity when used as a positive electrode material for a lithium secondary battery. Can be improved. It is particularly preferable that z is in the range of 0.02 or more and 0.05 or less.

The method for producing a lithium nickel composite oxide of the present embodiment can have the following steps.

A mixing step of forming a mixture of the above-mentioned lithium hydroxide for producing a lithium-nickel composite oxide and a nickel compound.

A firing step of firing a mixture at a temperature of 700 ° C. or higher and 780 ° C. or lower in an atmosphere having an oxygen content of 60% by volume or more and a carbon dioxide gas concentration of 5% by volume ppm or less.

Each process will be described below.
(Mixing process)
In the mixing step, a mixture of the above-mentioned lithium hydroxide and a nickel compound can be formed.

The nickel compound used in this case is not particularly limited, and a nickel compound which is a raw material of the lithium nickel composite oxide can be generally used.

As the nickel compound, it is particularly preferable to use one or more selected from the nickel composite hydroxide and the nickel composite oxide from the viewpoint of reducing contamination with impurities and controlling the particle size.

The nickel composite hydroxide may be obtained by an ordinary method and is not particularly limited, but since particles having a uniform composition and an appropriate particle size can be obtained, the nickel composite hydroxide obtained by the coprecipitation method can be obtained. A thing can be preferably used. Further, the nickel composite oxide is preferably obtained by oxidatively roasting a compound containing nickel and an additive element, and more preferably, for example, the one obtained by oxidatively roasting the nickel composite hydroxide.

When a nickel composite hydroxide and / or a nickel composite oxide is used as a raw material, the average particle size of the secondary particles of these raw materials is not particularly limited, but is preferably in the range of 5 μm or more and 20 μm or less. It is more preferably in the range of 8 μm or more and 15 μm or less. Since the average particle size of the raw material is inherited by the obtained lithium-nickel composite oxide, by setting the average particle size within the above range, the filling property is good and the reactivity with the electrolyte when used in a battery is high. It is possible to improve the battery characteristics.

The average particle size means the particle size at a volumetric integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method. As used herein, the average particle size has the same meaning.

The amount of lithium hydroxide to be mixed with the nickel compound is not particularly limited and can be selected according to the composition of the target lithium nickel composite oxide. For example, the mixing ratio can be set according to the composition of the above-mentioned lithium nickel composite oxide. Since the composition hardly changes before and after firing, the amount of lithium hydroxide to be mixed with the nickel composite oxide can be easily determined from the composition of the lithium nickel composite oxide to be obtained.

As the mixing method, a commonly used method may be used, a general mixer can be used, a shaker mixer, a Lady Gemixer, a Julia mixer, a V blender, etc. can be used, to the extent that the skeleton of the nickel compound is not destroyed. , Should be well mixed.
[Baking process]
In the firing step, a lithium nickel composite oxide can be produced by firing the mixture obtained in the mixing step.

As for the atmosphere at the time of firing, the oxygen concentration is set to 60% by volume or more, preferably 80% by volume or more in order to sufficiently supply oxygen.
Since the atmosphere at the time of firing can be an oxygen atmosphere, the oxygen concentration can be 100% by volume or less.

This is because water is produced in the synthetic reaction of the lithium nickel composite oxide as shown in the reaction formula (1) mentioned in the method for producing lithium hydroxide. When a large amount of water is generated, if sufficient oxygen is not supplied from the outside, the diffusion of oxygen to the reaction field is insufficient and the reaction of reaction formula (1) does not proceed, and the synthesis of lithium nickel composite oxide is performed. This is because there is a possibility that the positive electrode active material has deteriorated battery performance due to a shortage and a decrease in battery capacity.

At this time, oxygen is preferably mixed with nitrogen or an inert gas. If it is less than 60% by volume, the oxygen partial pressure is insufficient, and the above-mentioned oxygen deficiency state occurs, resulting in insufficient production of the lithium nickel composite oxide.

The firing temperature is in the range of 700 ° C. or higher and 780 ° C. or lower, preferably 700 ° C. or higher and 750 ° C. or lower. This is because if the temperature is lower than 700 ° C., the crystal growth of the obtained lithium nickel composite oxide is not sufficient, and good battery performance may not be obtained. Further, when the temperature exceeds 780 ° C., the obtained lithium nickel composite oxide starts to decompose, and during the battery reaction when used as a positive electrode active material, crystals that hinder the movement of lithium ions start to be mixed, resulting in deterioration of battery performance. Because there is a risk of inviting.

In the firing step, in the process of raising the temperature to the firing temperature, the nickel compound and lithium hydroxide are sufficiently maintained in a temperature range from the melting temperature of lithium hydroxide to the firing temperature, preferably in the range of 450 ° C. or higher and 650 ° C. or lower. It is preferable to react with.

As the furnace used for firing, various furnaces whose atmosphere can be controlled can be used, but it is preferable to use an electric furnace that does not generate exhaust gas, and in industrial production, especially a pusher furnace and a roller hearth furnace, etc. It is preferable to use a furnace capable of continuously firing.

Hereinafter, examples of the present invention will be described in more detail in comparison with comparative examples, but the present invention is not limited to these examples.

Here, the evaluation methods in the following Examples and Comparative Examples will be described.

Regarding the water content of the obtained lithium hydroxide, the water content in the sample is vaporized by heating to 300 ° C., the water content is introduced into the titration cell with a carrier gas, and then the water content is determined by the Karl Fischer titration method. rice field.

The carbon content of lithium hydroxide was analyzed by the high frequency combustion-infrared absorption method.
[Example 1]
As a means for flowing and heating the lithium hydroxide hydrate, a rolling stirrer 10 (manufactured by Nippon Coke Industries, Ltd., model: FM4000) equipped with a heating means having a jacket structure shown in FIG. 1 was prepared. Note that FIG. 1 schematically shows a cross-sectional view taken through the rotation axis of the stirring means of the rolling stirrer and in a plane parallel to the rotation axis.

As shown in FIG. 1, the rolling stirrer 10 has a jacket structure in which the side wall portion and the wall portion 11 constituting the bottom surface have a jacket structure, that is, a hollow structure in which a wall is further provided on the outer periphery of the wall constituting the sample chamber. , It is configured to be able to supply steam, which is a heat medium, to the inside of the wall portion 11. A stirring means 12 is provided at the bottom, and by rotating the stirring means 12 with a motor (not shown), the sample put in the rolling stirrer 10 can be flowed. Further, a lid can be arranged on the upper part of the inside of the container surrounded by the wall portion 11 of the rolling stirrer 10, so that the atmosphere around the sample can be controlled.

In this embodiment, lithium hydroxide monohydrate having a carbon content of 0.05% by mass is placed in a container 111 of the rolling stirrer 10 as a raw material, a lid (not shown) is arranged as described above, and rolling is performed. The atmosphere inside the container of the stirrer 10 was set to a vacuum atmosphere (-90 kPa) in which the pressure was reduced from the atmospheric pressure. At this time, the partial pressure of carbon dioxide gas in the container 111 was 4 Pa.

Then, water vapor is supplied into the jacket of the wall portion 11 at a gauge pressure of 0.19 MPa (equivalent to 130 ° C.), and the inside of the container is stirred by the stirring means 12 while maintaining the vacuum atmosphere as described above, whereby the sample is used. A certain lithium hydroxide monohydrate was heated to 130 ° C. while flowing (drying step). The temperature gradient in lithium hydroxide in the steady state was 50 ° C.

When the obtained lithium hydroxide was evaluated after the drying step, it was confirmed that the lithium hydroxide was anhydrous lithium hydroxide having a water content of 0.5% by mass. In addition, the average value of the carbon content sampled from any 10 locations of the obtained anhydrous lithium hydroxide was 0.09% by mass. The maximum value of the variation in carbon content between the samples of each sampled anhydrous lithium hydroxide was 0.02% by mass.

The obtained anhydrous lithium hydroxide and a nickel composite oxide having an average particle size of 12 μm (Ni _0.82 Co _0.15 Al _0.03 O ₂ ) are combined with the total amount of metal elements (Ni + Co + Al) in the nickel composite oxide. ), The atomic ratio of lithium (Li) to 1.02 was mixed to form a mixture (mixing step).

Next, the mixture was calcined at a temperature of 750 ° C. in an atmosphere having an oxygen content of 80% by volume or more and a carbon dioxide gas content of 5% by volume ppm or less to obtain a lithium nickel composite oxide (calcination step).

A coin-type lithium-ion battery was produced using the obtained lithium-nickel composite oxide as a positive electrode material and carbon as a negative electrode material, and the battery capacity was measured. The initial discharge capacity was 211 mAh / g.
[Example 2]
In the drying step, lithium hydroxide monohydrate having a carbon content of 0.15% by mass was used as a raw material, and the time of the drying step was extended to dry until the water content became 0.1% by mass. Anhydrous lithium hydroxide was obtained in the same manner as in Example 1 except for the above. The temperature gradient in lithium hydroxide in the steady state was 50 ° C. The average value of the carbon content sampled from any 10 locations of the obtained anhydrous lithium hydroxide was 0.26% by mass. The maximum value of the variation in carbon content between the samples of each sampled anhydrous lithium hydroxide was 0.05% by mass.

Using the obtained anhydrous lithium hydroxide, a lithium nickel composite oxide was obtained in the same manner as in Example 1, a coin-type lithium ion battery was produced, and the battery capacity was measured. The initial discharge capacity was 208 mAh / g.
[Example 3]
When the drying step was carried out, the lithium hydroxide hydrate was dried in the same manner as in Example 1 except that the atmosphere inside the container of the rolling stirrer 10 was reduced from atmospheric pressure to a vacuum atmosphere (-45 kPa). did. At this time, the partial pressure of carbon dioxide gas in the container 111 was 8 Pa. The temperature gradient in lithium hydroxide in the steady state was 50 ° C.
When the obtained lithium hydroxide was evaluated after the drying step, it was confirmed that the lithium hydroxide was anhydrous lithium hydroxide having a water content of 0.6% by mass. In addition, the average value of the carbon content sampled from any 10 locations of the obtained anhydrous lithium hydroxide was 0.22% by mass. The maximum value of the variation in carbon content between the samples of each sampled anhydrous lithium hydroxide was 0.05% by mass.
Using the obtained anhydrous lithium hydroxide, a lithium nickel composite oxide was obtained in the same manner as in Example 1, a coin-type lithium ion battery was produced, and the battery capacity was measured. The initial discharge capacity was 207 mAh / g.
[Example 4]
When carrying out the drying step, the lithium hydroxide hydrate was dried in the same manner as in Example 1 except that the lithium hydroxide hydrate was dried by an air flow dryer (manufactured by Seishin Enterprise Co., Ltd., continuous instantaneous air flow type dryer). It was dry.
As the raw material, lithium hydroxide monohydrate having the same carbon content as in Example 1 and having a carbon content of 0.05% by mass was used, and as the carrier gas for drying using an air flow dryer, the partial pressure of carbon dioxide gas was used. However, 4 Pa of nitrogen gas was used, and the inside of the air flow dryer was maintained in the same atmosphere as the carrier gas during the drying process. Further, the carrier gas was heated to 200 ° C., and the temperature gradient in the steady state was 0 ° C.
When the obtained lithium hydroxide was evaluated after the drying step, it was confirmed that the lithium hydroxide was anhydrous lithium hydroxide having a water content of 0.4% by mass. In addition, the average value of the carbon content sampled from any 10 locations of the obtained anhydrous lithium hydroxide was 0.13% by mass. The maximum value of the variation in carbon content between the samples of each sampled anhydrous lithium hydroxide was 0.03% by mass.
Using the obtained anhydrous lithium hydroxide, a lithium nickel composite oxide was obtained in the same manner as in Example 1, a coin-type lithium ion battery was produced, and the battery capacity was measured. The initial discharge capacity was 209 mAh / g.
[Comparative Example 1]
In the drying step, lithium hydroxide monohydrate having a carbon content of 0.3% by mass was used as a raw material, and the time of the drying step was shortened to dry until the water content reached 1% by mass. Anhydrous lithium hydroxide was obtained in the same manner as in Example 1 except for the above. The temperature gradient in lithium hydroxide in the steady state was 50 ° C. The average value of the carbon content sampled from any 10 locations of the obtained anhydrous lithium hydroxide was 0.51% by mass. The maximum value of the variation in carbon content between the samples of each sampled anhydrous lithium hydroxide was 0.05% by mass.

Using the obtained anhydrous lithium hydroxide, a lithium nickel composite oxide was obtained in the same manner as in Example 1, a coin-type lithium ion battery was produced, and the battery capacity was measured. The initial discharge capacity was 201 mAh / g.
[Comparative Example 2]
In the drying step, anhydrous lithium hydroxide was obtained in the same manner as in Example 1 except that the wall portion 11 was heated to 200 ° C. with a heater and dried while stirring in an air atmosphere until the water content became 1% by mass. Got The partial pressure of carbon dioxide in the atmosphere is 400 Pa.

The temperature gradient in lithium hydroxide in the steady state was 100 ° C. The average value of the carbon content sampled from any 10 locations of the obtained anhydrous lithium hydroxide was 0.6% by mass. The maximum value of the variation range of the carbon content between the samples of each sampled anhydrous lithium hydroxide was 0.07% by mass.

Using the obtained anhydrous lithium hydroxide, a lithium nickel composite oxide was obtained in the same manner as in Example 1, a coin-type lithium ion battery was produced, and the battery capacity was measured. The initial discharge capacity was 199 mAh / g.
[Comparative Example 3]
In the drying step, a static dryer is used instead of the rolling stirrer, the dryer is set to 130 ° C., and the water content becomes 1% by mass in a vacuum atmosphere (-90 kPa) depressurized from the air atmosphere. Anhydrous lithium hydroxide was obtained in the same manner as in Example 1 except that it was dried for 10 hours. At this time, the partial pressure of carbon dioxide gas in the dryer was 4 Pa.
In the drying step, lithium hydroxide was not flowed. The temperature gradient in lithium hydroxide in the steady state was 70 ° C. The average value of the carbon content sampled from any 10 locations of the obtained anhydrous lithium hydroxide was 0.7% by mass. The maximum value of the variation range of the carbon content between the samples of each sampled anhydrous lithium hydroxide was 0.20% by mass.

Using the obtained anhydrous lithium hydroxide, a lithium nickel composite oxide was obtained in the same manner as in Example 1, a coin-type lithium ion battery was produced, and the battery capacity was measured. The initial discharge capacity was 197 mAh / g.
[Comparative Example 4]
In the drying step, the lithium hydroxide hydrate was dried in the same manner as in Example 1 except that the atmosphere inside the container of the rolling stirrer 10 was reduced from atmospheric pressure to a vacuum atmosphere (-25 kPa). At this time, the partial pressure of carbon dioxide gas in the container 111 was 15 Pa. The temperature gradient in lithium hydroxide in the steady state was 50 ° C.
When the obtained lithium hydroxide was evaluated after the drying step, it was confirmed that the lithium hydroxide was anhydrous lithium hydroxide having a water content of 0.7% by mass. In addition, the average value of the carbon content sampled from any 10 locations of the obtained anhydrous lithium hydroxide was 0.35% by mass. The maximum value of the variation in carbon content between the samples of each sampled anhydrous lithium hydroxide was 0.08% by mass.
Using the obtained anhydrous lithium hydroxide, a lithium nickel composite oxide was obtained in the same manner as in Example 1, a coin-type lithium ion battery was produced, and the battery capacity was measured. The initial discharge capacity was 203 mAh / g.

Claims (11)

It is a method for producing lithium hydroxide used when producing a lithium-nickel composite oxide by mixing lithium hydroxide and a nickel compound and firing them.
Lithium nickel having a drying step of obtaining anhydrous lithium hydroxide having a carbon content of 0.3% by mass or less by heating while flowing lithium hydroxide hydrate in an atmosphere where the partial pressure of carbon dioxide gas is 10 Pa or less. A method for producing lithium hydroxide for producing a composite oxide. The method for producing lithium hydroxide for producing a lithium nickel composite oxide according to claim 1, wherein the heating is performed at a temperature of 80 ° C. or higher and 250 ° C. or lower. The method for producing lithium hydroxide for producing a lithium nickel composite oxide according to claim 1 or 2, wherein in the drying step, the lithium hydroxide hydrate is flowed in a vacuum using a rolling stirrer. The lithium nickel composite oxide according to claim 3, wherein the rolling stirrer has a heating means provided with a jacket structure, and heating is performed in the drying step by circulating a heated heat medium in the jacket. A method for producing lithium hydroxide for production. The method for producing lithium hydroxide for producing a lithium nickel composite oxide according to claim 4, wherein the heat medium is water vapor, and the heating is performed at a temperature of 100 ° C. or higher and 150 ° C. or lower. A lithium hydroxide raw material used for producing a lithium-nickel composite oxide by mixing lithium hydroxide and a nickel compound and firing them.
A lithium hydroxide raw material for producing a lithium nickel composite oxide, which is anhydrous lithium hydroxide having a carbon content of 0.3% by mass or less. The lithium hydroxide raw material for producing a lithium nickel composite oxide according to claim 6, wherein the water content is 10% by mass or less. The lithium hydroxide raw material for producing a lithium nickel composite oxide according to claim 6 or 7, wherein the average value of the carbon content is 0.09% by mass or more and 0.3% by mass or less. The lithium hydroxide raw material for producing a lithium nickel composite oxide according to any one of claims 6 to 8, wherein the variation in carbon content is within 0.10% by mass. A mixing step of forming a mixture of the lithium hydroxide raw material for producing a lithium nickel composite oxide according to any one of claims 6 to 9 and a nickel compound.
Lithium-nickel composite oxide having a firing step of firing the mixture at a temperature of 700 ° C. or higher and 780 ° C. or lower in an atmosphere having an oxygen content of 60% by volume or more and a carbon dioxide gas concentration of 5% by volume or less. Manufacturing method. The method for producing a lithium nickel composite oxide according to claim 10 , wherein the nickel compound is one or more selected from a nickel composite hydroxide and a nickel composite oxide.

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