JP2015040138A - Method for removing sulfate radical from manganese oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing sulfate radicals which is a method for reducing sulfate radicals by washing, and easily reduces sulfate radicals from manganese oxides containing several percentages by weight of sulfate radicals to a level required for being used as a manganese source of a lithium-manganese composite oxide in comparison with conventional methods without causing the composition change of the manganese oxides.SOLUTION: In a method for removing sulfate radicals, water, manganese oxides, and at least one salt selected from the group consisting of zinc amalgam, ascorbic acid, sulfurous acid, ethylenediaminetetraacetic acid 2 aconitic acid, erythorbic acid, formic acid, dibutylhydroxytoluene, oxalic acid dihydrate, diisobutylaluminium hydride, sodium borohydride tocopherol, and sulfur dioxide are mixed with each other.

Description

  The present invention relates to a method for removing sulfate radicals from manganese oxide. More specifically, the present invention relates to a method for removing sulfate radicals from manganese oxide using manganese sulfate as a raw material by washing, and a method for washing manganese oxide.

  Various manganese oxides have been proposed as manganese sources for lithium manganese composite oxides used as positive electrode active materials for lithium ion secondary batteries. Due to its cost, availability, and ease of handling, manganese oxides starting from manganese sulfate are widely used industrially as manganese sources for lithium manganese composite oxides.

Such a manganese oxide and a lithium manganese composite oxide using this as a manganese source contain several weight percent of sulfate radicals (SO ₄ ) derived from the starting material. However, since the sulfate radical inhibits the battery reaction of the lithium ion secondary battery, it is necessary to reduce the sulfate radical to about 0.5% by weight or less that does not inhibit the battery reaction.

  In order to reduce the sulfate radicals contained in the lithium manganese composite oxide, a method for producing a manganese oxide in which the incorporation of sulfate radicals from manganese sulfate is suppressed is disclosed (Patent Document 1). For example, Patent Document 1 reports manganese trioxide obtained by adding manganese sulfate at a specific flow rate after obtaining manganese hydroxide using manganese sulfate as a starting material and oxidizing it. The trimanganese tetroxide had a low sulfur concentration of 0.001% by weight (a sulfate group concentration of 0.003% by weight).

  However, manganese oxides that suppress the uptake of sulfate radicals from the starting material manganese sulfate tend to complicate the reaction process for obtaining this, and further requires fine control of the reaction conditions. For this reason, the method represented by Patent Document 1 for suppressing the uptake of sulfate radicals during the production of manganese oxide tends to complicate the production equipment.

As a more simple and industrial method for reducing sulfate radicals, a method for removing sulfate radicals contained therein by variously treating the manganese oxide after production has been reported. For example, by firing manganese dioxide having an SO ₄ content of 0.6% by weight at a high temperature of 800 ° C. or higher, a method for removing the sulfate radical (Patent Document 2), after washing manganese dioxide with pure water, By heat-treating this to make manganese dioxide into dimanganese trioxide, a method of reducing sulfate radicals to 0.3% by weight (Patent Document 3), and further, manganese dioxide containing 1.1% by weight of sulfate radicals. A method (Patent Document 4) for removing washing sulfate radicals with warm water or dilute ammonia water has been reported.

  Moreover, the method of reducing the sulfate radical of electrolytic manganese dioxide to 0.3 weight% by processing with acids other than a sulfuric acid without heat processing is reported (patent document 5).

JP 2004-292264 A Japanese Patent Laid-Open No. 11-147841 JP 2008-156162 A JP 2001-155734 A JP 2002-056847 A

  The method for removing sulfate radicals by heat treatment involves a change in the composition of manganese oxide due to thermal decomposition. In addition, the equipment required for heat treatment is large and easily complicated. Therefore, industrially, it is preferable that the sulfate radical is removed without heat treatment.

  Furthermore, when removing sulfate radicals to a desired amount by washing such as acid washing, it is necessary to wash with a large amount of washing liquid for a long time. Long-term washing facilitates the removal of sulfate radicals. On the other hand, the manganese oxide partially reacts due to contact with the cleaning liquid, and the composition may become non-uniform.

  Furthermore, it is preferable to remove the sulfate radical as much as possible. However, the more the removal treatment is performed, the higher the production cost of the resulting manganese oxide. A manganese oxide as a manganese source of a lithium manganese composite oxide is required to have a method for removing a minimum sulfate group for use in the application while suppressing an increase in production cost.

  In the present invention, among the methods for reducing sulfate radicals, in particular, a sulfate radical removal method by washing, from manganese oxide containing several weight% of sulfate radicals, without any change in the composition of manganese oxide, and It is an object of the present invention to provide a method for reducing sulfate radicals to a level necessary for serving as a manganese source of a lithium manganese composite oxide more simply than before.

  The present inventors have studied a method for removing sulfate radicals from manganese oxides containing several weight percent of sulfate radicals without heat treatment. As a result, it was found that by using an aqueous solution containing a small amount of an additive, sulfate radicals can be reduced without changing the composition of the manganese oxide even after long-time washing, and the present invention has been completed.

  The present invention will be described below.

  The present invention is from the group of zinc amalgam, ascorbic acid, sulfurous acid, ethylenediaminetetraacetic acid 2aconitic acid, erythorbic acid, dibutylhydroxytoluene, oxalic acid dihydrate, diisobutylaluminum hydride, sodium tocopherol borohydride, and sulfur dioxide. This is a method for removing sulfate radicals by mixing at least one selected salt (hereinafter referred to as “treatment agent”), water and manganese oxide. Thereby, removal of a sulfate radical advances, without a composition of manganese oxide changing.

The present invention is a method for removing sulfate radicals from manganese oxides containing sulfate radicals (SO ₄ ). Therefore, the manganese oxide used for the method of the present invention contains a certain amount of sulfate radical. As such a manganese oxide, a sulfate group is contained in an amount of 0.6 wt% to 4 wt%, further 0.6 wt% to 2 wt%, and further 0.6 wt% to 1 wt%. A manganese oxide is mentioned.

  In the present invention, the sulfate radical content (% by weight) is the ratio of the sulfate radical weight to the manganese oxide weight.

The manganese oxide used for the removal method of the present invention may be a manganese oxide containing the above sulfate group, and examples thereof include manganese oxide using manganese sulfate as a raw material. Furthermore, the manganese oxide is preferably at least one selected from the group consisting of manganese dioxide (MnO ₂ ), manganese trioxide (Mn ₂ O ₃ ), and trimanganese tetraoxide (Mn ₃ O ₄ ). More preferably, it is manganese trioxide.

  Manganese oxide can be subjected to the removal method of the present invention in any shape. In order to increase the efficiency of removing sulfate radicals, the manganese oxide is preferably used in a powder form, and further in a powder form having a volume average particle diameter of 1 to 50 μm.

  As long as the manganese oxide used in the removal method of the present invention can be used as a manganese source of the lithium manganese composite oxide, the physical properties other than the sulfate radical are arbitrary.

For example, the surface area may be 0.5 to 5.0 m ² / g as the BET specific surface area, the density may be 1.3 to 2.6 g / cm ³ as the tap density, and the average particle size may be 1.0 to 50 μm.

  Here, the “tap density” is the bulk density of the powder after tapping the container filled with the powder and tapping until the volume of the container disappears. Therefore, it is a value different from the density when the powder is pressure-molded, so-called press density.

  In the present invention, zinc amalgam, ascorbic acid, sulfurous acid, ethylenediaminetetraacetic acid 2-aconitic acid, erythorbic acid, dibutylhydroxytoluene, oxalic acid dihydrate, diisobutylaluminum hydride, sodium borohydride tocopherol, and dioxide At least one salt selected from the group of sulfur is used. From the viewpoint of increasing the efficiency of removing sulfate radicals, the treating agent is preferably at least one salt selected from the group of ascorbic acid, sulfurous acid and erythorbic acid, and is at least one salt of sulfurous acid or erythorbic acid. It is preferable. These treatment agents can be provided in a solid form or in a powder form. Therefore, since there is almost no volatilization of the treatment agent during the sulfate radical removal treatment, the sulfate radical removal treatment can be performed in a stable and constant atmosphere.

  Examples of the salt used as the treating agent include alkali metal salts, and further, sodium salts or potassium salts of inorganic acids.

  In the removal method of the present invention, it is preferable to use a treatment agent of 2 mol% or more, more preferably 10 mol% or more, and even more preferably 30 mol% or more based on manganese in the manganese oxide to be treated. The greater the proportion of the treatment agent relative to the manganese oxide, the greater the effect of suppressing the change in the composition of the manganese oxide. However, the treatment agent may be 50 mol% or less, further 40 mol% or less of the manganese oxide subjected to the treatment.

  From the viewpoint of improving the efficiency of removing sulfate radicals, the water mixed with the treating agent and the manganese oxide is preferably substantially free of sulfate radicals, preferably substantially free of anions and cations, and pure water. It is preferable that However, the removal method using water that does not contain impurities such as pure water tends to increase the manufacturing cost. Therefore, the water used in the present invention may contain cations of 0.001% by weight or more, further 0.003% by weight or more, and further 0.004% by weight or more. Thereby, the pre-processing cost of the water provided to this invention can be suppressed.

  In the removal method of the present invention, it is preferable to use 10 times or more, more preferably 15 times or more, and even 20 times or more of the weight of the manganese oxide to be treated. The greater the amount of water used, the greater the effect of removing sulfate radicals. However, if the water is 50 times or less, more preferably 30 times or less the weight of manganese oxide, manganese oxidation after treatment by the removal method of the present invention The content of sulfate radicals such that the product can be used as a manganese source of the lithium manganese composite oxide, for example, the sulfate radical concentration is 0.5% by weight or less.

  In the removing method of the present invention, the treating agent, water and manganese oxide may be mixed. The mixing method is arbitrary. For example, a method in which manganese oxide, water and a treatment agent are mixed simultaneously, a method in which manganese oxide and water are mixed to obtain a slurry, and a treatment agent is mixed therewith, and further, a treatment An example is a method in which an agent and water are mixed to form a removal solution, which is mixed with manganese oxide.

  Since the treatment agent is a salt, the removal method of the present invention can carry out the treatment at a pH exceeding 6. Since the liquid property during the treatment does not become strongly acidic, the sulfate radical removal treatment can be performed under the condition that the reaction of the manganese oxide is further suppressed. For this reason, the removal method of the present invention is preferably performed at a pH of 7 to 10, more preferably at a pH of 7 to 9.

  In the removal method of the present invention, the higher the temperature, the higher the sulfate radical removal efficiency. Therefore, the treatment temperature is preferably 40 ° C. or higher, more preferably 60 ° C. or higher. On the other hand, if the temperature becomes too high, water tends to evaporate. Therefore, the treatment temperature may be less than 90 ° C., further 80 ° C. or less, and further 70 ° C. or less.

  In the removal method of the present invention, the oxidation-reduction potential (hereinafter referred to as “ORP”) with respect to the standard hydrogen electrode in the atmosphere during the removal treatment is less than 300 mV, and further 250 mV or less. The ORP within this range is also considered to be one of the reasons that the change in the chemical composition of the manganese oxide is suppressed.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for reducing sulfate radicals from manganese oxides containing several weight percent of sulfate radicals more easily than before and without changing the composition of the manganese oxide. Furthermore, the present invention can also be used as a method for cleaning manganese oxide.

  By the removal method of the present invention, the sulfate group contained in the manganese oxide is reduced by 30% or more, further 40% or more, and further 50% or more compared to the sulfate group before the treatment.

  Furthermore, manganese oxide does not react in the removal method of the present invention. Therefore, the chemical composition of the manganese oxide does not change before and after the removal method of the present invention is applied for 1 hour or more, further 3 hours or more.

  Furthermore, the manganese oxide cleaning method of the present invention provides a manganese oxide having a low sulfate radical. The manganese oxide is suitable as a manganese raw material for a lithium manganese composite oxide.

Scanning electron microscope image of the synthetic trimanganese tetraoxide (scale in the figure is 1 μm) Scanning electron microscope observation of the manganese oxide after the treatment of Example 1 (scale in the figure is 1 μm) Scanning electron microscope image of the manganese oxide after treatment in Comparative Example 1 (scale in the figure is 1 μm)

  Next, an Example is shown and this invention is demonstrated. However, the present invention is not limited to these examples.

(Composition analysis)
A sample was dissolved in a hydrochloric acid solution, and the measurement solution was measured by ICP spectroscopic analysis as a measurement solution. A commercially available ICP spectroscopic analyzer (trade name: ICP 3000 DV, manufactured by PerkinElmer Japan) was used for the ICP emission analysis.

  The manganese concentration and the sulfate radical concentration were determined from the obtained measurement results.

(X-ray diffraction measurement)
The crystal phase of the sample was measured by powder X-ray diffraction. The measurement was performed with a general X-ray diffractometer. A CuKα ray (λ = 1.5405 mm) is used as the radiation source, the measurement mode is step scan, the scan condition is 0.04 ° per second, the measurement time is 3 seconds, and the measurement range is 2 ° to 5 ° to 80 °. Measured with

  No. of JCPDS pattern of trimanganese tetraoxide The powder X-ray diffraction pattern of 24734 was compared with the obtained powder X-ray diffraction pattern and identified.

(Scanning electron micrograph)
The sample was observed using a general scanning electron microscope (manufactured by JEOL).

Synthesis Example After heating 500 mL of pure water to 80 ° C., a reaction slurry in which trimanganese tetraoxide was crystallized was obtained by mixing the raw material liquid while blowing air so that the ORP was 100 ± 20 mV. The raw material solution used was a 2 mol / L manganese sulfate aqueous solution and a 2 mol / L sodium hydroxide aqueous solution.

  The manganese sulfate aqueous solution was continuously added to pure water at a constant rate, while the sodium hydroxide aqueous solution was appropriately added so that the pH of the reaction slurry was constant at 7.0.

  The reaction slurry was continuously discharged and the raw material solution was added so that the total amount of the reaction slurry was 1 L. The reaction slurry was recovered, filtered and washed to obtain a product. The obtained product was dried at 100 ° C. to obtain trimanganese tetraoxide. The sulfate group content of the manganese trioxide was 0.8% by weight.

  The electron microscopic observation figure of the obtained trimanganese tetraoxide is shown in FIG.

Example 1
The mixed reaction slurry obtained in the synthesis example was subjected to solid-liquid separation to obtain trimanganese tetraoxide as a solid phase. The resulting sulfate group of trimanganese tetraoxide was 0.8% by weight.

  After adding water and sodium elsorbate to 15 g of the trimanganese tetraoxide, the sulfate radical was removed while stirring at a temperature of 60 ° C. In the removal treatment, water has a cation concentration of 0.004% by weight and pH = 7.7, and among cations contained in water, cations having a concentration of 1 ppm by weight or more are sodium ions, silicon ions, potassium ions, And calcium ions.

  The water was 20 times the weight of trimanganese tetraoxide, and sodium erythorbate was 10 mol% with respect to manganese contained in trimanganese tetraoxide.

  The removal treatment was performed for 180 minutes, followed by filtration and washing, followed by drying at 100 ° C. in the atmosphere.

  Powder X-ray diffraction measurement of the dried manganese oxide was performed, and it was confirmed that the manganese trioxide after the removal treatment was also a single phase of manganese trioxide. Furthermore, it was confirmed that there was no change in the particle shape from the synthetic trimanganese tetraoxide.

  Table 1 shows the experimental conditions of this example, and Table 2 shows the evaluation results of manganese trioxide before and after the removal treatment of this example. Moreover, the scanning electron micrograph of the trimanganese tetraoxide of a present Example is shown in FIG.

Example 2
The sulfate radical removal treatment and removal were performed in the same manner as in Example 1 except that sodium erythorbate was 2 mol% with respect to manganese contained in trimanganese tetraoxide and the removal treatment was 30 minutes. The treated manganese trioxide was filtered, washed, and dried.

  Powder X-ray diffraction measurement of the dried manganese oxide was performed, and it was confirmed that the manganese trioxide after the removal treatment was also a single phase of manganese trioxide. Furthermore, it was confirmed that there was no change in the particle shape from the synthetic trimanganese tetraoxide.

  Table 1 shows the experimental conditions of this example, and Table 2 shows the evaluation results of manganese trioxide before and after the removal treatment of this example.

Example 3
Example 1 except that sodium sulfite was used in place of sodium erythorbate, that sodium sulfite was 30 mol% relative to manganese contained in trimanganese tetraoxide, and that the removal treatment was 60 minutes. In this way, the sulfate radical removal treatment, and the trimanganese tetraoxide after the removal treatment were filtered, washed, and dried.

  Powder X-ray diffraction measurement of the dried manganese oxide was performed, and it was confirmed that the manganese trioxide after the removal treatment was also a single phase of manganese trioxide. Furthermore, it was confirmed that there was no change in the particle shape from the synthetic trimanganese tetraoxide.

  Table 1 shows the experimental conditions of this example, and Table 2 shows the evaluation results of manganese trioxide before and after the removal treatment of this example.

Comparative Example 1
The treatment was performed in the same manner as in Example 1 except that sodium erythorbate was not used, and the treated trimanganese tetraoxide was filtered, washed, and dried.

  Powder X-ray diffraction measurement of the dried manganese oxide was performed, and it was confirmed that the manganese trioxide after the removal treatment contained γ-MnOOH in addition to trimanganese tetraoxide. Further, it was confirmed that acicular crystals were formed in the trimanganese tetraoxide of this comparative example as compared with the particle shape from the trimanganese tetraoxide of the synthesis example.

  Table 1 shows the experimental conditions of this comparative example, and Table 2 shows the evaluation results of manganese trioxide before and after the removal treatment of this comparative example. Moreover, the scanning electron micrograph of the trimanganese tetraoxide of this comparative example is shown in FIG.

  From the results of the examples and comparative examples, in the removal method of the present invention, the trimanganese tetraoxide does not cause a partial reaction, the sulfate radical after the treatment is 0.5% by weight or less, and the lithium manganese based composite oxidation It has been found that sulfate radicals can be removed to the extent that they can be used as manganese sources. On the other hand, in the comparative example, the sulfate radical was removed more than in the examples, but it was found that local reaction occurred during the treatment of trimanganese tetraoxide.

Claims (3)

  Selected from the group of zinc amalgam, ascorbic acid, sulfurous acid, ethylenediaminetetraacetic acid 2-aconitic acid, erythorbic acid, formic acid, dibutylhydroxytoluene, oxalic acid dihydrate, diisobutylaluminum hydride, sodium tocopherol borohydride, and sulfur dioxide A method for removing sulfate radicals, comprising mixing at least one salt, water and manganese oxide.   The method for removing a sulfate radical according to claim 1, wherein the water contains 0.001% by weight or more of cations.   The method for removing sulfate radicals according to claim 1 or 2, wherein the manganese oxide is trimanganese tetraoxide.

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