JP6733287B2 - Method for producing nickel-manganese composite - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention is suitable as a raw material for a positive electrode material having nickel and manganese, such as a lithium-nickel-manganese-based composite oxide suitable as a positive electrode material for a lithium secondary battery, and a lithium-nickel-cobalt-manganese-based composite oxide. It relates to a method for producing a nickel-manganese composite in which nickel and manganese are evenly distributed.

In recent years, lithium-nickel-manganese-based composite oxides and lithium-nickel-cobalt-manganese-based composite oxides have attracted attention as high energy materials as positive electrode active materials for lithium secondary batteries.

These composite oxides are preferably produced using a nickel-manganese composite raw material in which nickel and manganese are uniformly distributed. For example, an oxidizing agent was used as a precursor of the lithium-nickel-manganese composite oxide. Nickel-manganese composite oxyhydroxide having a chemical composition formula represented by Ni _0.25+α Mn _0.75-α OOH (provided that -0.025≦α≦0.025), obtained by a coprecipitation method. The thing was disclosed (patent document 1). The nickel-manganese composite oxyhydroxide is composed of a single crystal phase having a cadmium hydroxide structure, is stable in the atmosphere, and is excellent in not causing segregation of manganese components in general steps such as coprecipitation, washing, and drying. It is disclosed that it is a precursor.

On the other hand, lithium-nickel-cobalt-manganese-based composite oxides as positive electrode active materials for lithium secondary batteries have been studied for a wide range of compositions with a nickel-manganese ratio of 1:1 to 5:3. However, a nickel-manganese composite raw material in which the ratio of nickel and manganese can be freely set has been desired.

WO2015/0088863

It is an object of the present invention to provide a method for producing a nickel-manganese composite in which the ratio of nickel and manganese can be freely set and nickel and manganese are evenly distributed.

As a result of diligent studies on the method for producing a nickel-manganese composite raw material, the inventors have crystallized the nickel-manganese composite in an atmosphere in which Ni is divalent and Mn is trivalent, whereby the ratio The inventors have found that a nickel-manganese composite in which nickel and manganese are evenly distributed can be obtained, and the present invention has been completed. That is, the present invention is a metal salt aqueous solution containing nickel, a metal salt aqueous solution containing manganese, a caustic soda aqueous solution and an oxidizing agent, or a metal salt aqueous solution containing nickel and manganese, a caustic soda aqueous solution and an oxidizing agent are mixed, and Ni is divalent. in, and, in an atmosphere which Mn is trivalent, nickel - it is characterized by crystallizing a manganese complex, chemical composition formula _{Ni x Mn 1-x O a} (OH) 2-a ( where 0.225≦x≦0.775 and 0.5≦a≦0.9).

Hereinafter, the present invention will be described in detail.

In the method for producing a nickel-manganese composite of the present invention, a chemical composition formula is Ni _x Mn _1-x O _a by mixing a metal salt aqueous solution containing nickel, a metal salt aqueous solution containing manganese, a caustic soda aqueous solution and an oxidizing agent. The nickel-manganese composite represented by (OH) _2-a crystallizes.

In the method for producing a nickel-manganese composite of the present invention, a nickel-manganese composite slurry is obtained by mixing a nickel-containing metal salt aqueous solution, a manganese-containing metal salt aqueous solution, a caustic soda aqueous solution and an oxidizing agent. The nickel-manganese composite slurry is filtered, washed with water and dried to obtain a nickel-manganese composite.

The method for producing a nickel-manganese composite of the present invention includes, for example, supplying a metal salt aqueous solution containing nickel, a metal salt aqueous solution containing manganese, a caustic soda aqueous solution and an oxidizing agent to a reaction vessel having a constant volume, and mixing them. Then, a method of obtaining the nickel-manganese composite, for example, stopping the supply when the liquid amount in the reaction container reaches a desired value, and extracting the total amount of the nickel-manganese composite after a certain period of time is applicable. ..

However, the continuous method of continuously supplying and continuously extracting the produced nickel-manganese composite is an economically preferable method because the equipment cost is low.

Hereinafter, the present invention will be described in detail with reference to a continuous method as an example.

In the method for producing a nickel-manganese composite according to the present invention, it is preferable to continuously supply a metal salt aqueous solution containing nickel and a metal salt aqueous solution containing manganese. Further, the ratio X of nickel and manganese: X can be controlled by the supply ratio of the metal salt aqueous solution containing nickel and the metal salt aqueous solution containing manganese.

The method for supplying the metal salt aqueous solution containing nickel and the metal salt aqueous solution containing manganese is not particularly limited, and a metal salt aqueous solution in which a nickel salt is dissolved and a metal salt aqueous solution in which a manganese salt is dissolved are produced, and each metal salt aqueous solution is prepared. Can be charged to the reaction vessel at a constant ratio. At this time, each aqueous solution of the metal salt may be put in a separate place in the reaction vessel, but it is preferable to put them in the same place, and particularly preferably, the aqueous solution of the metal salt containing nickel and the metal containing manganese before the reaction vessel is put. Mix the brine solution.

The method of mixing the metal salt aqueous solution containing nickel and the metal salt aqueous solution containing manganese is performed by putting the metal salt aqueous solution containing nickel and the metal salt aqueous solution containing manganese in a container for mixing and stirring by a stirrer or the like to homogenize the mixture. However, it is also preferable to use a line mixer to mix and homogenize.

The concentrations of the nickel-containing metal salt aqueous solution and the manganese-containing metal salt aqueous solution are not particularly limited, but it is economically preferable that the obtained nickel-manganese composite slurry concentration is high, and therefore it is preferable that the concentration is as high as possible. .. Since the solubilities of nickel and manganese are both 2 to 3 mol/L, the solubility is usually set to 1.9 to 2.1 mol/L. For example, a metal salt aqueous solution containing 2.0 mol/L of nickel and a metal salt aqueous solution containing 2.0 mol/L of manganese are produced, and the volume ratio of nickel metal salt aqueous solution:manganese metal salt aqueous solution=X:1-X. Just supply it.

The type of salt of the metal salt aqueous solution containing nickel and the metal salt aqueous solution containing manganese used in the present invention is not particularly limited, but considering the raw material cost, corrosiveness and stability, nickel sulfate aqueous solution and manganese sulfate aqueous solution are used. It is preferable to use.

Another method for producing a nickel-manganese composite of the present invention is to mix an aqueous metal salt solution containing nickel and manganese, an aqueous solution of caustic soda, and an oxidizer to obtain a chemical composition formula of Ni _x Mn _1-x O _a (OH). _The nickel-manganese composite represented by _2-a crystallizes. You may manufacture the mixed aqueous solution of the nickel salt and manganese salt which melt|dissolved nickel salt and manganese salt by a fixed ratio, and may supply the mixed aqueous solution of this nickel salt and manganese salt to a reaction container. In this case, the total concentration of nickel and manganese may be 1.9 to 2.1 mol/L, and the molar ratio of nickel and manganese may be X:1-X.

In the method for producing the nickel-manganese composite of the present invention, it is essential to supply the caustic soda aqueous solution to the reaction vessel. Examples of the caustic soda aqueous solution include aqueous solutions of sodium hydroxide, lithium hydroxide, potassium hydroxide and the like. There is no particular limitation on the concentration of the caustic soda aqueous solution, but the resulting nickel-manganese composite slurry can be maintained at a high concentration to improve the production efficiency, reduce the load on the filtration step, and further reduce the caustic supply rate tolerance. Since it can be made wider and stable manufacturing and manufacturing cost are improved, it is preferably 1 to 48 wt%, and more preferably 10 to 30 wt%. As the caustic soda aqueous solution, it is possible to use, for example, one in which solid sodium hydroxide is dissolved in water, one in which the concentration of sodium hydroxide aqueous solution generated from salt electrolysis is adjusted, or the like.

In the method for producing the nickel-manganese composite of the present invention, it is essential to supply the oxidizing agent to the reaction vessel. The oxidizing agent is used to form an atmosphere in which the valence of Ni in the aqueous solution of the metal salt is divalent and the valence of Mn is trivalent and stable. The oxidizing agent used in the present invention is not particularly limited as long as it has a valence of Ni of 2 and a valence of Mn of 3 and can form a stable atmosphere. From an economical standpoint, usually, an oxygen-containing gas, a hydrogen peroxide solution, or the like is preferably used. Examples of the oxygen-containing gas include air, pure oxygen, a mixture of oxygen and an inert gas (for example, nitrogen), and the like. To be Of these, air is particularly preferable. Air may be supplied to the reaction vessel using a compressor or the like.

The reaction vessel used in the present invention can supply a metal salt aqueous solution containing nickel, a metal salt aqueous solution containing manganese, a caustic soda aqueous solution and an oxidizing agent, or a metal salt aqueous solution containing nickel and manganese, a caustic soda aqueous solution and an oxidizing agent. It suffices that they can be mixed uniformly. Mixing may be performed with a stirrer at a constant rotation speed.

The obtained nickel-manganese composite slurry of the present invention is continuously extracted. The method of withdrawing is not particularly limited, but it is preferable to withdraw so that the liquid amount in the reaction vessel is maintained at a constant amount. For example, when the liquid level exceeds a certain height, the so-called overflow type in which the liquid exceeding the liquid level is discharged by its own weight is simple and particularly preferable. Of course, it is also preferably applicable to constantly measure the liquid surface and extract the slurry with a pump or the like so that the liquid surface becomes constant.

The present invention neutralizes a metal salt aqueous solution containing nickel and a metal salt aqueous solution containing manganese, or a metal salt aqueous solution containing nickel and manganese, and imparts an appropriate oxidizing power to Ni and Mn. Nickel-manganese composites are produced.

Giving an appropriate oxidizing power to Ni and Mn means that the atmosphere is stable in which Ni is divalent and Mn is trivalent. The stable valence of the metal depends on the pH of the aqueous solution and the redox potential (hereinafter referred to as ORP). Therefore, for example, by controlling ORP to a predetermined value under the conditions of desired temperature and pH, Ni It is possible to form an atmosphere in which M is divalent and Mn is trivalent and stable.

The stable valence of the metal in the aqueous solution can be calculated from the relationship between the temperature and pH of the aqueous solution and the standard electrode potential. This is known as a potential-pH diagram, and is described, for example, in "Basic Course for Chemists 11 Electron Transfer Chemistry, Tadashi Watanabe, Seiichiro Nakabayashi, Asakura Shoten, 4th edition, September 10, 199". The structure of the potential-pH diagram is described on pages 72 to 73.

As a preferable method of crystallizing the nickel-manganese composite in an atmosphere in which Ni is divalent and Mn is trivalent, a metal salt aqueous solution containing nickel, a metal salt aqueous solution containing manganese, and a caustic soda aqueous solution are preferable. And a oxidant, or a metal salt aqueous solution containing nickel and manganese, a caustic soda aqueous solution and an oxidant are mixed, and the slurry liquid has a temperature of 60 to 80° C., a pH of 8.5 to 10.0, and an ORP. Of 0.15 to 0.21 V vs. SHE can crystallize the nickel-manganese composite.

In the method for producing a nickel-manganese composite of the present invention, the composition of nickel and manganese in the nickel-manganese composite can be adjusted by the supply ratio of the aqueous metal salt solution containing nickel and the aqueous metal salt solution containing manganese. When using a metal salt aqueous solution containing nickel and manganese, the mixing ratio of nickel and manganese may be adjusted.

The pH can be controlled by the ratio between the supply amount of the metal salt aqueous solution containing nickel and the metal salt aqueous solution containing manganese, or the supply flow rate of the metal salt aqueous solution containing nickel and manganese and the supply flow rate of the caustic soda aqueous solution. Since the supply amount of the metal salt aqueous solution containing nickel, the metal salt aqueous solution containing manganese, and the metal salt aqueous solution containing nickel and manganese is directly connected to the production amount of the nickel-manganese composite of the present invention, the metal salt containing nickel is usually used. The supply amount of the aqueous solution and the aqueous solution of metal salt containing manganese is supplied at a desired flow rate, and the supply flow rate of the aqueous solution of caustic soda is adjusted so that the pH of the nickel-manganese composite slurry becomes a predetermined value.

The ORP is controlled by the supply amount of the oxidizing agent. The ORP of the nickel-manganese composite slurry is measured, and the supply amount of the oxidizing agent is adjusted so that the ORP has a predetermined value.

The particularly preferred oxidizing agent of the present invention is air, which can be controlled by the supply amount of the oxidizing agent, but the present inventors have found that the present invention cannot be achieved by merely setting the supply amount of air. For example, it has been found that when the stirring rotation speed of the stirrer for stirring the reaction container changes, the ORP changes even under other conditions, and the effect of the present invention may not be exhibited. Therefore, in the present invention, it is preferable to keep the stirring state constant.

It is not always clear why the ORP changes depending on the stirring rotation speed even if the supply amount of the air as the oxidant is constant, but the inventors consider the following.

Oxygen gas in the air dissolves in the nickel-manganese composite slurry, and dissolved oxygen oxidizes Ni and Mn. On the other hand, the dissolved rate of oxygen gas is affected by temperature, pressure, bubble surface area, dissolved oxygen transfer rate, etc., in addition to the amount of air supplied to the slurry. For example, it is assumed that when the stirring rotation speed changes, the bubble diameter and the like change, so the oxygen dissolution rate changes, and as a result, the ORP changes as the oxygen activity in the liquid changes.

By applying the above-described method for producing a nickel-manganese composite, the chemical composition formula is Ni _x Mn _1-x O _a (OH) _2-a (however, 0.225≦X≦0.775, 0.5 A nickel-manganese composite represented by ≦a≦0.9 is obtained.

The resulting nickel-manganese composite has a crystal structure of cadmium hydroxide type. On the other hand, in the α-type nickel hydroxide type structure, since the transition metal layers are relatively wide, it is easy to take in anions that may be impurities such as SO ₄ . With the cadmium hydroxide type structure, no anion is incorporated between the transition metal layers. The cadmium hydroxide type structure is a hexagonal cadmium iodide type structure having hydroxide ions arranged at the positions of iodide ions. The hydroxide ions are arranged in a nearly hexagonal close-packed structure, and the metal ions are located in the octahedral hexacoordinated space in every other layer in the c-axis direction. In addition, the obtained nickel-manganese composite may not have all the atoms arranged regularly, and may have a portion in which the order of surface overlap is disordered, that is, a so-called stacking fault.

In addition, the obtained nickel-manganese composite may have a mixture of a cadmium hydroxide structure having a stacking fault and a hydrotalcite-like structure. The hydrotalcite-like structure is composed of divalent Ni and trivalent Mn, and has a chemical composition formula: Ni _y Mn _(1-y) (OH) ₂ (SO ₄ ) _(1-y)/2 (however, 0 <y<1).

As a preferred production method of the present invention, a nickel-manganese composite can be produced by bringing the nickel-manganese composite obtained by the above-mentioned production method into contact with an aqueous solution of caustic soda, followed by filtration and washing with water. By using this manufacturing method, the amount of SO ₄ in the nickel-manganese composite is particularly reduced, so that a particularly preferable raw material of the positive electrode active material for a lithium secondary battery can be manufactured.

When not contacted with the caustic soda aqueous solution, the amount of SO ₄ in the nickel-manganese composite is usually 0.6 wt% or more. Further, the SO ₄ amount increases as the nickel ratio in the nickel-manganese composite increases.

On the other hand, for example, in the XRD pattern of the nickel-manganese composite obtained in Example 3 shown in FIG. 3, in addition to the peak attributed to the nickel-manganese composite, the peak of the hydrotalcite-like structure (in the figure, The peak indicated by the arrow) is observed. The hydrotalcite-like structure is composed of divalent Ni and trivalent Mn, and is represented by the chemical composition formula: Ni _Y Mn _(1-Y) (OH) ₂ (SO ₄ ) _(1-Y)/2 . The inventors speculate that the higher the nickel ratio, the more the hydrotalcite-like structure increases, resulting in an increase in the amount of SO ₄ .

When this nickel-manganese composite having a hydrotalcite-like crystal phase is brought into contact with a caustic soda aqueous solution, and then filtered and washed with water, SO ₄ becomes less than 0.5 wt %. Furthermore, after contacting with an aqueous solution of caustic soda, followed by filtration and washing with water, the peak due to the hydrotalcite-like structure was observed as in the XRD pattern of the nickel-manganese composite obtained in Example 8 shown in FIG. It was not observed, and showed a single phase of nickel-manganese composite having a cadmium hydroxide structure.

The reason why the amount of SO ₄ can be reduced by bringing the nickel-manganese composite into contact with a caustic soda aqueous solution is not always clear, but from the above, the inventors consider the following.

SO ₄ ²⁻ increases in the nickel-manganese composite due to the mixture of the hydrotalcite-like crystal phase, but when contacting with caustic soda, SO ₄ ²⁻ is promptly replaced with OH ⁻ , and the SO ₄ amount decreases. At the same time, the hydrotalcite-like crystal phase disappears.

Separately from this, since a large amount of sodium sulfate is present in the nickel-manganese composite slurry obtained in the present invention, the main anion in the slurry is SO ₄ . Therefore, part of OH ⁻ , which is an anion of the nickel-manganese composite, is replaced with SO ₄ ²⁻ , and the SO ₄ amount becomes 0.6 wt% or more.

However, by removing SO ₄ around the nickel-manganese complex by normal filtration and washing with water, and then contacting with caustic soda, SO ₄ ²⁻ is replaced with OH ⁻ , and the SO ₄ amount is less than 0.6 wt %. It is estimated that it will be possible.

In any case, a nickel-manganese composite excellent in purity can be produced by bringing the nickel-manganese composite provided by the present invention into contact with an aqueous solution of caustic soda, and then filtering and washing with water.

Next, a preferred method of contacting the nickel-manganese composite with the aqueous sodium hydroxide solution will be described in detail.

The nickel-manganese complex to be contacted with the caustic soda aqueous solution is an aqueous metal salt solution containing nickel sulfate, an aqueous metal salt solution containing manganese sulfate, an aqueous caustic soda solution and an oxidizing agent, or an aqueous metal salt solution containing nickel and manganese, an aqueous caustic soda solution and an oxidizing agent. It is preferable to use a wet cake of the nickel-manganese composite obtained by filtering and washing the nickel-manganese composite slurry obtained by mixing If the nickel-manganese composite slurry or the unwashed nickel-manganese composite cake is used, the effect of the present invention becomes insufficient.

Further, it is also possible to use a nickel-manganese composite that has been filtered, washed with water, and dried, but it is necessary to dry again after contacting with caustic soda, and drying before contacting with caustic soda wastes drying energy, which is preferable. Absent.

The aqueous caustic soda solution to be brought into contact with the nickel-manganese composite is not particularly limited and may be the same as the aqueous caustic soda solution used for crystallization of the nickel-manganese composite.

The method of contacting the nickel-manganese composite with the caustic soda aqueous solution is not particularly limited, and any method can be preferably applied as long as the surface of the nickel-manganese composite particles is contacted with the caustic soda aqueous solution. Usually, the nickel-manganese composite can be brought into contact with an aqueous solution of caustic soda by using an apparatus used for filtration and washing.

For example, for filtration of slurry and washing with water, a filter press type filtration device, a suction filtration device, etc. are used, but after performing filtration and washing with these devices, change to a washing liquid for washing, supply caustic soda, nickel -A caustic soda solution may be passed through the manganese composite cake, filtered, and then washed with a washing solution.

The amount of the caustic soda aqueous solution may be 0.8 to 2 times the amount of the nickel-manganese composite to be treated, because the effect of the present invention is sufficient and the economy is excellent.

Other manufacturing conditions are not particularly limited, and a conventionally known method may be appropriately used, for example, the following can be adopted.

The total concentration (metal concentration) of all metals of nickel and manganese in the aqueous metal salt solution is arbitrary, but the metal concentration affects productivity, so 1.0 mol/L or more is preferable, and 2.0 mol/L or more Is more preferable. Usually, it is set to 2 mol/L.

The caustic soda aqueous solution is an aqueous sodium hydroxide solution, and for example, an aqueous solution of solid sodium hydroxide, an aqueous solution of sodium hydroxide produced from salt electrolysis, or the like can be used.

The mixing temperature at the time of mixing the metal salt aqueous solution and the oxidizing agent is not particularly limited, but the oxidation reaction of the metal salt aqueous solution is likely to proceed, and the nickel-manganese composite is more likely to be deposited, so that the temperature is 50° C. or higher. It is preferably 60° C. or higher and more preferably 60° C. or higher.

The nickel-manganese composite slurry liquid obtained in the present invention is subsequently filtered, washed and dried. There is no particular limitation on these methods, and the following methods are applicable, for example.

The nickel-manganese composite slurry is filtered to remove water, and then washed and dried.

As a device used for filtration and its conditions, a conventionally known method can be appropriately adopted. For example, pressure filtration may be performed using a filter press type filter, or reduced pressure filtration may be performed using a Buchner funnel or belt filter.

In the cleaning, impurities adhering to and adsorbing the nickel-manganese composite are removed. Examples of the washing method include a method in which the nickel-manganese composite cake is filtered and washed while pouring water (for example, pure water, tap water, river water, etc.). Usually, it is possible to carry out the washing using the same device after the filtration.

Drying removes the water content of the nickel-manganese composite. Examples of the drying method include drying the nickel-manganese composite at 110 to 150° C. for 2 to 15 hours.

By applying the present invention, the ratio of nickel and manganese can be freely set, and nickel and manganese are uniformly distributed, suitable for the raw material of the positive electrode active material for a lithium secondary battery, a nickel-manganese composite. Can be manufactured.

Further, the nickel-manganese composite obtained by the production method of the present invention has excellent purity such as low SO ₄ content.

9 is an XRD pattern of nickel-manganese composites of Example 1 and Example 8. 3 is an XRD pattern of the nickel-manganese composite of Example 2. It is an XRD pattern of the nickel-manganese composites of Example 3 and Example 9 (the arrow in the figure indicates the peak of the hydrotalcite-like structure). 4 is an XRD pattern of the nickel-manganese composite of Example 4 (the arrow in the figure indicates the peak of hydrotalcite-like structure). It is an XRD pattern of the nickel-manganese composite of Example 5 and Example 10 (the arrow in a figure shows the peak of a hydrotalcite-like structure). 3 is an XRD pattern of the nickel-manganese composite of Example 6 (the arrow in the figure indicates the peak of hydrotalcite-like structure). 4 is an XRD pattern of the nickel-manganese composite of Example 7 (the arrow in the figure indicates the peak of hydrotalcite-like structure). 5 is an XRD pattern of the nickel-manganese composite of Comparative Example 1. 9 is an XRD pattern of the nickel-manganese composite of Comparative Example 2. 9 is an XRD pattern of the nickel-manganese composite of Comparative Example 3.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the invention is not limited thereto.

<Powder X-ray diffraction measurement>
Using an X-ray diffractometer (sample horizontal multipurpose X-ray diffractometer, trade name: Ultima IV, manufactured by Rigaku), powder X-ray diffraction measurement of the sample was performed. CuKα ray (λ=1.5405Å) is used as the radiation source, the measurement mode is step scan, the scanning condition is 0.04° per second, the measurement time is 8 seconds, and the measurement range is 2θ of 5 to 90°. It was measured at.

<Identification of crystalline phase>
In the XRD pattern obtained by the XRD measurement under the above conditions, having a sharp peak at 2θ=19.0±0.5° and having a broad XRD peak at 36.9±1.5°, It is assumed to have a cadmium hydroxide structure. The broad peak shapes other than the lowest angle are due to stacking faults.

Further, a relatively sharp peak at 10 to 12° and a broad peak at 21 to 24° were assumed to have a hydrotalcite-like structure.

<Measurement of chemical composition>
The chemical composition in the nickel-manganese composite is measured by dissolving it in a mixed solution of hydrochloric acid and hydrogen peroxide, nickel is quantified by a nickel concentration meter (Ni-5Z, manufactured by Kasahari Chemical Industry Co., Ltd.), and manganese is a potential difference. Quantification is performed by an automatic titrator (AT-610, manufactured by Kyoto Electronics Manufacturing Co., Ltd.), and the amounts of S and Na are determined by using an inductively coupled plasma emission spectrometer (trade name: OPTIMA5300DV, manufactured by PERKIN ELMER). The ratio of Ni and Mn in the nickel-manganese composite oxyhydroxide, and the amount of S and the amount of Na were calculated. The SO ₄ amount was converted from the S amount.

Example 1
Nickel sulphate and manganese sulphate were dissolved in pure water to obtain an aqueous solution containing 0.5 mol/L nickel sulphate and 1.5 mol/L manganese sulphate, which was used as the metal salt aqueous solution. The total metal concentration is 2.0 mol/L, nickel:manganese=1:3 mol ratio).

After deionized water was charged to an overflow level in a reaction vessel having an internal volume of 10 L, the temperature was raised to and maintained at 70°C while stirring with a stirrer at a stirring speed of 800 rpm. The reaction container has a structure in which the liquid is discharged by overflow when the liquid amount exceeds 6 L.

The metal salt aqueous solution was added to the reaction vessel at 0.45 L/H, and at the same time, air as an oxidant was bubbled into the reaction vessel at a supply rate of 1.8 NL/min. At the time of supplying the metal salt aqueous solution and the air, a 20 wt% sodium hydroxide aqueous solution (caustic soda aqueous solution) is intermittently added so as to have a pH of 9.25, to produce a nickel-manganese composite slurry, which is prepared by an overflow method. It was continuously discharged from the reaction vessel.

The ORP of the nickel-manganese composite slurry in the reactor remained stable at 0.20V. At a temperature of 70° C., pH: 9.25, and ORP: 0.20 V, Ni was divalent and Mn was trivalent.

About 50 hours after the start of the reaction, the nickel-manganese composite slurry discharged from the reaction vessel was collected, filtered, and washed to obtain a nickel-manganese composite wet cake.

The obtained nickel-manganese composite wet cake was dried at 115° C. for 5 hours to obtain a nickel-manganese composite (Ni _0.25 Mn _0.75 OOH).

Since the XRD pattern of the obtained nickel-manganese composite has a sharp peak at 2θ=19.0° and a broad peak after 2θ=40°, its crystal structure is water having a stacking fault. It had a cadmium oxide structure.

Further, SO ₄ of the obtained nickel-manganese composite was 0.6 wt% and Na was 930 ppm.

Example 2
A nickel-manganese composite slurry was produced in the same manner as in Example 1 except that a 20 wt% sodium hydroxide aqueous solution (caustic soda aqueous solution) was intermittently added so that the pH became 9.5.

The ORP of the nickel-manganese composite slurry in the reactor was stable at 0.18 V after 4 hours from the start of the reaction. The temperature was 70° C., pH was 9.5, and ORP was 0.18 V was an atmosphere in which Ni was divalent and Mn was trivalent.

About 50 hours after the start of the reaction, the XRD pattern of the nickel-manganese composite obtained by collecting, filtering, washing and drying the nickel-manganese composite slurry discharged from the reaction vessel was 2θ=19.0°. Since it has a sharp peak and a broad peak after 2θ=40°, its crystal structure was a cadmium hydroxide structure having a stacking fault.

Further, SO ₄ of the obtained nickel-manganese composite was 0.2 wt% and Na was 2,400 ppm.

Example 3
Nickel sulphate and manganese sulphate were dissolved in pure water to obtain an aqueous solution containing 1.0 mol/L nickel sulphate and 1.0 mol/L manganese sulphate, which was used as the metal salt aqueous solution. A nickel-manganese composite slurry was produced in the same manner as in Example 1 except that the total metal concentration was 2.0 mol/L and the ratio of nickel:manganese was 1:1.

The ORP of the nickel-manganese composite slurry in the reactor remained stable at 0.19 V after 4 hours from the start of the reaction. The temperature was 70° C., pH was 9.25, and ORP was 0.19 V was an atmosphere in which Ni was divalent and Mn was trivalent.

About 50 hours after the start of the reaction, the XRD pattern of the nickel-manganese composite obtained by collecting, filtering, washing, and drying the nickel-manganese composite slurry discharged from the reaction vessel is a hydroxide having a stacking fault. It was a mixture of cadmium structure and hydrotalcite-like structure.

Furthermore, SO ₄ of the obtained nickel-manganese composite was 4.6 wt% and Na was 320 ppm.

Example 4
A nickel-manganese composite slurry was produced in the same manner as in Example 3 except that a 20 wt% sodium hydroxide aqueous solution (caustic soda aqueous solution) was intermittently added so that the pH became 9.5.

The ORP of the nickel-manganese composite slurry in the reactor was stable at 0.18 V after 4 hours from the start of the reaction. The temperature was 70° C., pH was 9.5, and ORP was 0.18 V was an atmosphere in which Ni was divalent and Mn was trivalent.

About 50 hours after the start of the reaction, the XRD pattern of the nickel-manganese composite obtained by collecting, filtering, washing, and drying the nickel-manganese composite slurry discharged from the reaction vessel is a hydroxide having a stacking fault. It was a mixture of cadmium structure and hydrotalcite-like structure.

Further, the obtained nickel-manganese composite had SO ₄ of 3.9 wt% and Na of 460 ppm.

Example 5
Nickel sulphate and manganese sulphate were dissolved in pure water to obtain an aqueous solution containing 1.25 mol/L nickel sulphate and 0.75 mol/L manganese sulphate, which was used as the metal salt aqueous solution. A nickel-manganese composite slurry was produced in the same manner as in Example 1 except that the total metal concentration was 2.0 mol/L and the nickel:manganese ratio was 5:3 mol.

The ORP of the nickel-manganese composite slurry in the reactor remained stable at 0.19 V after 4 hours from the start of the reaction. The temperature was 70° C., pH was 9.25, and ORP was 0.19 V was an atmosphere in which Ni was divalent and Mn was trivalent.

About 50 hours after the start of the reaction, the XRD pattern of the nickel-manganese composite obtained by collecting, filtering, washing, and drying the nickel-manganese composite slurry discharged from the reaction vessel is a hydroxide having a stacking fault. It was a mixture of cadmium structure and hydrotalcite-like structure.

Further, the obtained nickel-manganese composite had SO ₄ of 7.4 wt% and Na of 40 ppm.

Example 6
A nickel-manganese composite slurry was produced in the same manner as in Example 5 except that a 20 wt% sodium hydroxide aqueous solution (caustic soda aqueous solution) was intermittently added so that the pH was 9.0.

The ORP of the nickel-manganese composite slurry in the reactor remained stable at 0.19 V after 4 hours from the start of the reaction. The temperature was 70° C., pH was 9.0, and ORP was 0.19 V was an atmosphere in which Ni was divalent and Mn was trivalent.

About 50 hours after the start of the reaction, the XRD pattern of the nickel-manganese composite obtained by collecting, filtering, washing, and drying the nickel-manganese composite slurry discharged from the reaction vessel is a hydroxide having a stacking fault. It was a mixture of cadmium structure and hydrotalcite-like structure.

Further, the obtained nickel-manganese composite had SO ₄ of 7.4 wt% and Na of 140 ppm.

Example 7
A nickel-manganese composite slurry was produced in the same manner as in Example 5 except that a 20 wt% sodium hydroxide aqueous solution (caustic soda aqueous solution) was intermittently added so that the pH was 8.75 .

The ORP of the nickel-manganese composite slurry in the reactor remained stable at 0.19 V after 4 hours from the start of the reaction. The temperature was 70° C., pH was 8.75 , and ORP was 0.19 V was an atmosphere in which Ni was divalent and Mn was trivalent.

About 50 hours after the start of the reaction, the XRD pattern of the nickel-manganese composite obtained by collecting, filtering, washing, and drying the nickel-manganese composite slurry discharged from the reaction vessel is a hydroxide having a stacking fault. It was a mixture of cadmium structure and hydrotalcite-like structure.

Further, the obtained nickel-manganese composite had SO ₄ of 7.4 wt% and Na of 140 ppm.

Comparative Example 1
A nickel-manganese composite slurry was produced by the same operation as in Example 1, and after about 72 hours had elapsed from the start of production, the air supply rate was changed to 13.0 NL/min.

After changing the air supply rate, the ORP increased to 0.22V. About 24 hours after the air supply rate was changed, the XRD pattern of the nickel-manganese composite obtained by collecting, filtering, washing and drying the nickel-manganese composite slurry discharged from the reaction vessel was a cadmium hydroxide structure, It was a mixture with a nickel-manganese composite having a structure different from the cadmium hydroxide structure and the hydrotalcite-like structure. At a temperature of 70° C., a pH of 9.25, and an ORP of 0.22 V, Ni was divalent and Mn was deviated from the atmosphere.

Furthermore, SO ₄ of the obtained nickel-manganese composite was 1.3 wt% and Na was 950 ppm.

Comparative example 2
By the same operation as in Example 1, a nickel-manganese composite slurry was produced, and after about 72 hours from the start of production, the stirring rotation speed was reduced to 400 rpm.

The ORP decreased to 0.12V after the stirring rotation speed decreased. After a lapse of about 24 hours from the decrease of the stirring rotation speed, the XRD pattern of the nickel-manganese composite obtained by collecting, filtering, washing and drying the nickel-manganese composite slurry discharged from the reaction vessel was a cadmium hydroxide structure, It was a mixture with a nickel-manganese composite having a structure different from the cadmium hydroxide structure and the hydrotalcite-like structure. At a temperature of 70° C., pH: 9.25, and ORP: 0.12 V, Ni was divalent, and Mn was out of the atmosphere in which trivalent.

Furthermore, SO ₄ of the obtained nickel-manganese composite was 1.8 wt% and Na was 1,080 ppm.

Comparative Example 3
A nickel-manganese composite was obtained in the same manner as in Example 1 except that the pH was set to 8.3.

The ORP at this time was 0.16V. At a temperature of 70° C., a pH of 8.3, and an ORP of 0.16 V, Ni was divalent and Mn was deviated from the atmosphere in which it was trivalent.

The XRD pattern of the obtained nickel-manganese composite was a mixture of a cadmium hydroxide structure and a nickel-manganese composite having a structure different from the cadmium hydroxide structure and the hydrotalcite-like structure.

Further, the obtained nickel-manganese composite had SO ₄ of 2.7 wt% and Na of 690 ppm.

Example 8
A wet cake of the nickel-manganese composite obtained in Example 1 was poured on a Buchner funnel from above with 10 wt% caustic soda having the same weight as the solid content in the wet cake.

After the poured caustic soda was filtered, it was washed with water and then dried at 115° C. for 5 hours to obtain a nickel-manganese composite.

The XRD pattern of the obtained nickel-manganese composite is a cadmium hydroxide structure having a sharp peak at 2θ=19.0°, a broad peak after 2θ=40°, and a stacking fault, SO ₄ of the obtained nickel-manganese composite was 0.2 wt %, Na was 680 ppm, and SO ₄ amount and Na amount were decreased.

Example 9
The wet cake of the nickel-manganese composite obtained in Example 3 was poured on a Buchner funnel from above with 10 wt% caustic soda having the same weight as the solid content in the wet cake.

After the poured caustic soda was filtered, it was washed with water and then dried at 115° C. for 5 hours to obtain a nickel-manganese composite.

The XRD pattern of the obtained nickel-manganese composite is a cadmium hydroxide structure having a sharp peak at 2θ=19.0°, a broad peak after 2θ=40°, and a stacking fault, The peak of hydrotalcite-like structure disappeared.

Furthermore, SO ₄ of the obtained nickel-manganese composite was 0.2 wt %, Na was 280 ppm, and especially the amount of SO ₄ was greatly reduced.

Example 10
The wet cake of the nickel-manganese composite obtained in Example 3 was poured on a Buchner funnel from above with 10 wt% caustic soda having the same weight as the solid content in the wet cake.

After the poured caustic soda was filtered, it was washed with water and then dried at 115° C. for 5 hours to obtain a nickel-manganese composite.

The XRD pattern of the obtained nickel-manganese composite is a cadmium hydroxide structure having a sharp peak at 2θ=19.0°, a broad peak after 2θ=40°, and a stacking fault, The peak of hydrotalcite-like structure disappeared.

Further, SO ₄ of the obtained nickel-manganese composite was 0.3 wt %, Na was 80 ppm, and the SO ₄ amount was significantly reduced.

The results of Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 1.

表１、及び、図１〜１０から、本発明の製造方法で製造するニッケル−マンガン複合物は、水酸化カドミウム構造、又は、水酸化カドミウム構造とハイドロタルサイト様構造からなるが、本発明の製造方法を逸脱すると、水酸化カドミウム構造及びハイドロタルサイト様構造とは異なる構造をもつニッケル−マンガン複合物が混在する。さらに、実施例８、９、１０の結果より、本発明が提供する製造方法を適用することにより、ＳＯ_４、及び、Ｎａの含有量が少ないニッケル−マンガン複合物を得ることができる。

From Table 1 and FIGS. 1 to 10, the nickel-manganese composite produced by the production method of the present invention comprises a cadmium hydroxide structure, or a cadmium hydroxide structure and a hydrotalcite-like structure. If the manufacturing method is deviated, a nickel-manganese composite having a structure different from the cadmium hydroxide structure and the hydrotalcite-like structure is mixed. Furthermore, from the results of Examples 8, 9 and 10, by applying the production method provided by the present invention, it is possible to obtain a nickel-manganese composite having a low content of SO ₄ and Na.

The nickel-manganese composite obtained by the method for producing a nickel-manganese composite of the present invention is most suitable as a raw material of a lithium-nickel-manganese-based composite oxide used as a positive electrode active material of a lithium secondary battery, It becomes possible to configure a high-performance lithium secondary battery using the lithium-nickel-manganese-based composite oxide as a battery positive electrode.

Claims (5)

A metal salt aqueous solution containing nickel, a metal salt aqueous solution containing manganese, a caustic soda aqueous solution and an oxidizing agent, or a metal salt aqueous solution containing nickel and manganese, a caustic soda aqueous solution and an oxidizing agent are mixed, and the slurry liquid after mixing has a temperature of 60. -80[deg.] C., pH 9 to 11, ORP 0.15 to 0.20 V vs SHE, Ni divalent, and Mn trivalent in an atmosphere in which nickel-manganese composite is present. characterized by crystallization things, the chemical composition formula _{Ni x Mn 1-x O a} (OH) 2-a ( where, 0.225 ≦ x ≦ 0.775,0.5 ≦ a ≦ 0. The method for producing a nickel-manganese composite represented by 9). The method for producing a nickel-manganese composite according to claim 1, wherein the nickel-manganese composite has a cadmium hydroxide structure having a stacking fault. The method for producing a nickel-manganese composite according to claim 1, wherein the nickel-manganese composite contains a cadmium hydroxide structure having a stacking fault and a hydrotalcite-like structure. A metal salt aqueous solution containing nickel, a metal salt aqueous solution containing manganese, a caustic soda aqueous solution, and an oxidizing agent are continuously supplied to a reaction vessel, and the nickel-manganese composite is continuously extracted from the reaction vessel. Item 4. A method for producing the nickel-manganese composite according to any one of Items 3 . The nickel-manganese composite produced by the method for producing a nickel-manganese composite according to any one of claims 1 to 4 is brought into contact with an aqueous solution of caustic soda, and then filtered and washed with water. Method for producing nickel-manganese composite.

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