JP4608690B2 - Method for producing composite oxide - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improved positive electrode active material for a non-aqueous lithium secondary battery and a method for producing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, electronic devices have become smaller, higher performance, and cordless, and secondary batteries have attracted interest as their drive power sources. In particular, lithium ion secondary batteries are highly expected as batteries having high voltage and high energy density.
As the positive electrode active material of such a battery, a layered compound capable of intercalating and deintercalating lithium, for example, a composite oxide mainly composed of lithium and a transition metal, such as LiCoO ₂ and LiNiO ₇ (hereinafter, referred to as a lithium oxide). Lithium composite oxide).
Among such lithium composite oxides, there is LiCoO ₂ as a positive electrode active material for lithium secondary batteries that has already been put into practical use, but it is cheaper because it uses rare and expensive cobalt in terms of resources. LiNiO ₂ -based materials have been vigorously developed as lithium composite oxides capable of high energy density.
[0003]
The preparation method of LiNiO _2, were uniformly mixed lithium material and a nickel material, it is necessary calcining it. In this raw material mixing process, if the mixing ratio of lithium and nickel varies, problems such as deterioration of the powder characteristics of the fired powder and lack of reproducibility of battery characteristics occur.
In view of this, the present applicant previously disclosed in Japanese Patent Application Laid-Open No. 11-135118, by forming a mixed powder of raw materials to obtain a lithium-transition metal composite oxide active material that is homogeneous and excellent in battery characteristics. A method for firing by increasing the density by performing forced aeration using an oxidizing gas is disclosed.
[0004]
[Problems to be solved by the invention]
However, the above method is an advantageous method for obtaining a lithium composite oxide excellent in battery characteristics on an industrial scale, but is mixed and molded on an industrial mass production scale using a lithium raw material and a nickel raw material, for example. When obtaining a baked powder through each step of calcination, a composition shift in the mixed powder occurs between the mixing and molding steps, and as a result, a non-uniform baked powder may be obtained.
That is, (1) when dry molding is performed, segregation occurs due to particle size difference, density difference, and shape difference between the lithium raw material powder and the nickel raw material powder, and the mixing ratio becomes non-uniform before firing, In some cases, non-uniform fired powder was obtained.
(2) When the mixture molding is performed by a wet method in which powders are dispersed and mixed in a solution, the surface of the molded body or the granulated body in the drying process for removing moisture of the obtained molded body or the granulated body. Lithium segregated in some cases, and when this was fired, non-uniform fired powder could be obtained. Further, even if the molded body or the granulated body is fired as it is, lithium moves to the surface when moisture evaporates by aeration firing, so that it may be similarly non-uniform fired powder.
(3) In addition, as a known technique, a method of adding an organic binder solution such as PVA to the raw material mixed powder and obtaining a molded body by the rolling granulation method is a firing reaction because the density of the obtained molded body is relatively low. In the case of LiNiO ₂ , there is a problem that the electrochemical characteristics are remarkably deteriorated because the organic binder decomposes and acts as a reducing agent during firing.
[0005]
In view of such circumstances, the object of the present invention is to provide a method for producing LiNiO _{2 comprising} the steps of mixing raw material powder, forming, and aeration firing, and the mixing composition ratio of lithium and nickel changes in the mixing and forming step. In addition, an object is to provide a method that is advantageous on an industrial mass production scale, does not become a heterogeneous calcined powder, and has high quality reproducibility, and a product to be obtained.
[0006]
[Means for Solving the Problems]
In order to improve the solid-phase reactivity at the time of firing, the present inventors used a water-soluble lithium compound as a lithium raw material and a water-insoluble nickel compound mainly composed of nickel as a nickel raw material. In this case, after the dry mixing, it is possible to perform aeration firing without changing the mixed composition ratio of the lithium and nickel compounds by increasing the binding property by a humidifying and mixing means in which water is added by spraying and continuously granulating and forming. According to the method, it has been found that the characteristic reproducibility in terms of quality is high, and that it is advantageous in industrial mass production scale. In particular, the amount of water to be added by spraying is 5 to 30 wt% with respect to the mixed powder, and the molding density of the obtained granulated molded body is 1.0 to 2.5 g / cm ³ . It has been found that desirable results can be obtained.
[0007]
That is, in the present invention, firstly, the lithium compound powder and the hydroxide powder of the main nickel and a transition metal other than nickel are dry mixed, and then 5 to 30 wt% of the obtained mixed powder. A method for producing a composite oxide, characterized in that water is sprayed and subjected to humidification and mixing, followed by granulation and molding, and the resulting granulation and molding is subjected to aeration firing in oxygen gas. Then, after dry-mixing the water-soluble lithium compound powder and the hydroxide powder of the main nickel and a transition metal other than nickel, 5 to 30 wt% of water is sprayed and added to the resulting mixed powder for humidification It is a method for producing a composite oxide, characterized in that it is continuously granulated after performing the mixing treatment, and the obtained granulated compact is subjected to aeration firing in oxygen gas. Third, the granulation molding density of the molded body is 1.0 to 2.5 g / cm ³ The method for producing a composite oxide according to 1 or 2, wherein the transition metal other than nickel is cobalt. A non-aqueous system characterized in that the fifth main component is a composite oxide of nickel, a transition metal other than nickel, and lithium obtained by the production method according to any one of the first to fourth aspects. It is a positive electrode active material for secondary batteries.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The raw material lithium compound powder used in the present invention is water-soluble and includes lithium hydroxide / hydrate or anhydride, lithium nitrate / hydrate or anhydride, and the like. Nickel compound powder, which is the main ingredient of nickel raw material, is composed of transition metals other than nickel and nickel, and examples thereof include oxides and hydroxides. In view of the high reactivity during synthesis, hydroxides are considered. Is desirable.
[0009]
These lithium compound powder and nickel-based compound powder have a molar ratio of lithium to nickel + M (where M is a transition metal other than nickel), 0.900 ≦ Li / (Ni + M) ≦ 1.100. Weigh until it becomes and dry-mix. In the humidifying and mixing step, the obtained dry mixture is added by spraying water as a binder while mixing and stirring. As the mixer, a paddle type horizontal axis rotary mixer, a high-speed flow type vertical axis rotary mixer, or the like can be used.
[0010]
As water for the binder, it is desirable to use pure water in consideration of reaction with other components during firing, contamination of the fired powder, and the like. That is, when a certain amount of water is uniformly sprayed as a binder during dry mixing, the particle surface is dissolved by the deliquescence property of the water-soluble lithium compound, and the nickel compound is uniformly contacted with the surface to enhance the binding property. In the granulation molding process, the molding density can be increased. The amount of spray water is preferably 5 to 30 wt% of the amount of the mixed powder. If the amount is less than 5 wt%, the amount of moisture adsorbed on the surface of the raw material powder is insufficient and the binding property does not increase, so that molding is difficult. On the other hand, if it exceeds 30 wt%, the molding density does not increase so much. Starts to elute and moves to the surface of the molded body as the water evaporates, so the uniformity of the composition begins to deteriorate. Accordingly, a suitable amount of water is 5 to 30 wt%, more preferably 10 to 30 wt% of the mixed powder amount.
[0011]
Regarding the granulation molding process, it is advantageous to granulate and mold the mixed powder continuously from the industrial mass production scale. In addition, the size of the granulated molded body is 2 to 10 cm spherical, rod-shaped, lens-shaped, plate-shaped, etc. without operations such as sizing and sizing, and each molded body is uniformly molded. It is necessary. In addition, the density of the granulated molded body is 1.0 to 2.5 g / cm ³ , preferably 1.5 to 5 so that the molded body does not break during aeration firing and promotes solid-phase reactivity during firing. 2.5 g / cm ³ is required. If it is less than 1.0 g / cm ³ , molding cannot be performed, and if it exceeds 2.5 g / cm ³ , molding becomes difficult. As the granulating machine, a disk-type extrusion granulator, a ring-type extrusion granulator, a briquetting compression granulator, a tableting compression granulator, or the like can be used.
[0012]
When the Li / (Ni + M) molar ratio of each granulated molded body obtained in the above granulation molding process was confirmed by analysis, there was no difference from the prepared Li / (Ni + M) molar ratio, and there was little variation. In addition, the characteristics of the lithium composite oxide after aeration firing are the same, and there is no variation in characteristics even when the above-mentioned raw material powder is subjected to mixing-granulation molding-aeration firing several times, and the results are highly reproducible. was gotten. That is, it has been clarified that the use of this production method is industrially advantageous and the quality reproducibility is high.
Moreover, it became clear that the lithium composite oxide in this invention shows the outstanding battery characteristic which hold | maintains high energy under a high voltage as an active material of a lithium ion secondary battery.
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the scope of the present invention is not limited by these.
[0013]
【Example】
[Example 1]
Lithium hydroxide hydrate (LiOH.H ₂ O) is used as the lithium compound, and Ni: Co: Al = 80: 15: 5 co-precipitated hydroxide powder is used as the molar component. Weighed so that the ratio Li / (Ni + Co + Al) = 1.05, and after performing a dry mixing treatment for 10 minutes with a paddle type horizontal shaft rotary mixer, mixed powder was further mixed while mixing with the mixer An amount of 15 wt% pure water was added by spraying, and a humidified mixing treatment was performed for a total of 30 minutes. Next, this humidified mixed powder was put into a disk-type extrusion granulator, and granulated and formed continuously. A rod-shaped molded body of about 5φ × 10 mm was obtained.
[0014]
The molding density of the granulated molded body obtained in the granulation molding process was 2.1 g / cm ³ . About this granulated compact, 20 points were sampled at random, and the Li / (Ni + M) molar ratio was confirmed by composition analysis. The charged Li / (Ni + M) molar ratio was 1.050, whereas The average value of the molar ratio of the 20 samples was 1.0497, the standard deviation was 0.0012, and the variation was small.
[0015]
Further, the granulated molded body was subjected to aeration firing for 10 hours in oxygen gas at 750 ° C., and the obtained fired powder was randomly sampled at 20 points to confirm the Li / (Ni + M) molar ratio by composition analysis. The average molar ratio of the 20 samples is 1.0502, and the standard deviation is 0.0015. The molar ratio of the granulated molded body and the molar ratio of the calcined powder with respect to the charged Li / (Ni + M) molar ratio. Were equivalent.
[0016]
Furthermore, as a result of repeating the manufacturing process of the calcined powder from powder mixing to aeration firing for the above raw material compound 10 times, the mother average value of the fired body was 1.0498, and its standard deviation was 0.0008, The variation was very small.
[0017]
[Example 2]
Except that the amount of pure water added was 10 wt% of the amount of mixed powder in the granulation and molding step, the same raw material as in Example 1 was subjected to the same mixing, granulation and firing treatment to obtain a fired powder. In addition, the density of the obtained granulated compact was 1.8 g / cm ³ . Moreover, about the obtained baked powder, 20 points | pieces were sampled similarly, As a result of checking a composition by molar ratio, the average value was 1.0513, the standard deviation was 0.0031, and the dispersion | variation was small.
[0018]
[Example 3]
Except that the amount of pure water added was 30 wt% of the amount of the mixed powder in the granulation and molding step, the same raw material as in Example 1 was subjected to the same mixing, granulation and firing treatment to obtain a fired powder. In addition, the density of the obtained granulated molded body was 2.3 g / cm ³ . Moreover, about the obtained baked powder, 20 points | pieces were sampled similarly, As a result of checking a composition by molar ratio, the average value was 1.0513, the standard deviation was 0.0031, and the dispersion | variation was small.
[0019]
[Comparative Example 1]
Using the same raw material powder as in Example 1, mixing with a V-type mixer for 30 minutes without the addition of pure water, and forming a lens-shaped molded product of 5φ × 5 mm with a tablet compression granulator, The same baking treatment as in Example 1 was performed to obtain a baked powder. The density of the obtained molded body was 1.8 g / cm ³ . Similarly, 20 points of the obtained baked powder were sampled, and the composition was confirmed by molar ratio. As a result, the average value of the molar ratio was slightly low at 1.0489 and the standard deviation was 0.0118, which showed considerable variation. It was.
[0020]
[Comparative Example 2]
The same raw material powder as in Example 1 was used, the amount of pure water added was 40 wt% of the amount of mixed powder, premixing was performed for 10 minutes with a V-type mixer, and further mixed for 20 minutes with a kneader. It was set as the spaghetti-shaped granulated molded object of diameter 5mm with the granulator. The granulated compact was dried at 100 ° C. for 10 hours to form a 5φ × 5 mm rod, and then fired in the same manner as in Example 1 to obtain a fired powder. The density of the molded body after the drying treatment was 1.9 g / cm ³ . Further, the obtained fired powder was similarly sampled at 20 points, and the composition was confirmed by the molar ratio. As a result, the average value of the molar ratio was 1.0415, the compositional deviation was large, and the standard deviation was also large at 0.0087. . Incidentally, the surface layer of the molded body after drying was precipitated Li ₂ CO _3.
[0021]
From the results of Examples 1 to 3 and Comparative Examples 1 and 2, the granulated molded body and the calcined powder obtained by the production method of the present invention were continuously granulated by adding water by spraying to enhance the binding property. It turns out that the mixing ratio of lithium and a nickel compound does not change by shaping | molding. Further, it can be seen that a homogeneous reaction can be achieved by subjecting the granulated molded body to aeration firing, and that the reproducibility of characteristics in terms of quality is high, and that it is industrially advantageous.
[0022]
【The invention's effect】
As explained above, the composite oxide of the present invention obtained by the production method including the step of performing spray addition of water to the mixed raw material powder and subsequent granulation molding does not change the mixing ratio of lithium and nickel, and This is advantageous in terms of industrial advantage and high reproducibility of characteristics in terms of quality. In addition, the positive electrode active material for a non-aqueous secondary battery using the composite oxide as a main material has an effect of having excellent battery characteristics capable of maintaining high voltage and high energy.
When the amount of water added in the above production method is 5 to 30 wt% of the mixed powder and the molding density of the granulated molded body is 1.0 to 2.5 g / cm ³ , the component mixing ratio is steadily set to a predetermined value. The effect that it can maintain is produced.

Claims (4)

  Lithium compound powder and hydroxide powder of nickel and transition metal other than nickel are dry-mixed, and then 5-30 wt% water is sprayed and added to the resulting mixed powder for humidification mixing treatment. A method for producing a composite oxide, comprising: granulating and forming the resultant granulated product, and subjecting the resulting granulated product to air firing in oxygen gas.   Water-soluble lithium compound powder and hydroxide powder of main nickel and transition metal other than nickel are dry-mixed, and then 5-30 wt% water is sprayed and added to the resulting mixed powder for humidification mixing A process for producing a composite oxide, characterized by continuously granulating and forming the treated product, and subjecting the resulting granulated compact to aeration firing in oxygen gas. ^{3. The} method for producing a composite oxide according to claim 1, wherein a molding density of the granulated compact is 1.0 to 2.5 g / cm ³ .   The method for producing a composite oxide according to claim 1, wherein the transition metal other than nickel is cobalt.