JPH0649577B2 - Novel manganese compound and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel manganese compound and a method for producing the same. More specifically, the present invention relates to a novel manganese compound suitable as a positive electrode active material for lithium batteries and useful as a lithium adsorbent in a high pH range, and a method for producing the same.

[Prior Art] Conventionally, as a crystal structure of manganese dioxide used as a positive electrode active material of a non-aqueous primary battery, as disclosed in JP-B-49-25571, a γ-β type or US Pat. , 856 are known.

On the other hand, LiMn ₂ is used as the positive electrode active material of the non-aqueous secondary battery.
O ₄ and its acid-treated products have been proposed (JP-A-63-63).
187569, Sho 63-114065). LiMn ₂ O
₄ and its acid-treated products are characterized in that manganese oxide is pre-doped with lithium to synthesize spinel-type lithium manganate having a three-dimensional channel structure, and lithium can be smoothly doped and dedoped by charging and discharging. There is a point that has been improved. However, since these active materials are synthesized using lithium, they have the drawback of being expensive in terms of performance, and have not yet been put into practical use.

On the other hand, the present inventors have prepared MgMn ₂ O ₄ prepared using magnesium whose ionic radius is slightly smaller than lithium.
It has been found that a three-dimensional channel structure is formed even when Mg or Mg ₂ MnO ₄ is acid-treated (Japanese Patent Laid-Open No. 62-27).
0420, Journal of the Japan Society of Sea Water 42, 114 pages, 1
988). These acid-treated products have excellent lithium selective adsorption properties in an aqueous solution and are suitable as a lithium adsorbent from a dilute solution. However, since these acid-treated products contain a relatively large amount of water of 10 to 20%, they have poor stability in organic solvents and are not suitable as a positive electrode active material for nonaqueous secondary batteries and the like.

[Problems to be Solved by the Invention] The present invention has been proposed in view of the above-mentioned conventional circumstances, and is a manganese compound suitable for a non-aqueous solvent, that is, it has a low water content and is three-dimensional. It is to provide a manganese compound having a channel structure at low cost.

[Means for Solving Problems] In order to achieve the above-mentioned object, the present inventors have studied various magnesium extraction methods from MgMn ₂ O ₄ prepared using magnesium, which is an inexpensive raw material, and as a result, It has been found that when magnesium is extracted using an oxidizing and acidic agent, a manganese compound having the original tetragonal structure and a low water content is synthesized. The present invention has been completed based on such findings, and is characterized in that a stable manganese compound is obtained by extracting magnesium under an oxidizing atmosphere.

The manganese compound obtained in the present invention was previously prepared from MgMn ₂ O.
₄ was treated with an acid to obtain a manganese compound (spacing 4.6).
3 ± 0.03, 2.71 ± 0.03, 2.42 ± 0.0
3, 2.33 ± 0.03, 2.00 ± 0.03, 1.5
It has a clearly different X-ray diffraction characteristic (having an X-ray diffraction peak at 4 ± 0.03), and thus is clearly another novel manganese compound. It is considered that this is because the extraction of magnesium under an oxidizing atmosphere suppressed dissolution of trivalent manganese due to the disproportionation reaction, and produced a manganese compound having a different structure. That is,
The present invention is a substance after magnesium extraction from MgMn ₂ O ₄ , and the main X-ray diffraction peak is a face spacing of 4.8.
9 ± 0.05Å, 2.74 ± 0.03Å, 2.47 ±
The present invention provides a manganese compound as described in 0.03Å and 2.03 ± 0.03Å.

As MgMn ₂ O ₄ used as a raw material in the present invention, for example, MgO and Mn ₂ O ₃ are mixed at a molar ratio of 1: 1,
By heat treatment at a temperature of 1100 ° C. for several hours, or hydroxides, oxides, carbonates, bicarbonates, nitrates, halides of magnesium and hydrous oxides, oxides, oxide hydroxides of manganese. , Carbonate, bicarbonate, nitrate and the like in a suitable combination, and then heat-treated at a temperature of 400 ° C. or higher.

The target manganese compound is obtained by immersing this MgMn ₂ O ₄ in a solution that is acidic and oxidizing, stirring it to elute and remove magnesium, washing the solid with water, and drying. As a solution that is acidic and oxidative,
Either a solution containing an acidic oxidizing agent or a solution containing a mixture of an oxidizing agent and an acid can be used, but a solution containing an acidic oxidizing agent is preferable from the viewpoint of treatment operation. As the acidic oxidizing agent, peroxonisulfate, bromine and the like are known, but any oxidizing agent which exhibits weak acidity in an aqueous solution and has an appropriate oxidizing power can be used. Among the acidic oxidizers, ammonium peroxonisulfate is preferable from the viewpoint of economical efficiency and easy handling. When an aqueous solution of ammonium peroxodisulfate is heated, oxygen and hydrogen ions are generated. This generated oxygen suppresses the dissolution of manganese oxide by exhibiting an oxidizing action, and at the same time, the generated hydrogen ion is MgM.
Facilitates the elution of magnesium from n ₂ O ₄ . The processing temperature can be from room temperature to 100 ° C, but is preferably 6
0-80 degreeC is good. The concentration of ammonium peroxodisulfate is preferably 0.25 to 2N, but is not limited to this. The treatment time depends on the heating temperature, but usually 0.5 to 4 hours is preferable.

By such a treatment, 85% or more of magnesium in MgMn ₂ O ₄ is extracted. In addition, the manganese oxide after magnesium extraction has a surface spacing of 4.89 ± 0.05 Å 2.7.
4 ± 0.03Å, 2.47 ± 0.03Å, 2.03 ±
A diffraction pattern with a peak at 0.03Å is given. These peaks are the X-ray diffraction peaks (A) of the raw material MgMn ₂ O _4.
STM card No. 23-392. Surface spacing 4.884
Å, 2.736 Å, 2.470 Å, 2.025 Å coincide with the X-ray diffraction peak). That is, the manganese oxide obtained by extracting magnesium by this treatment is the original M
It is clear that the tetragonal structure of gMn ₂ O ₄ is retained, and thus it is clear that a three-dimensional channel structure is formed after the escape of magnesium. In addition, the water content of the manganese oxide is 3% or less, which is significantly smaller than that of the MgMn ₂ O ₄ acid-treated product and is suitable as a non-aqueous solvent-based material.

It is possible to prepare tetragonal manganese oxides containing various concentrations of magnesium by changing the treatment conditions with a solution containing an acidic and oxidizing agent.

EXAMPLES Next, the present invention will be described in detail with reference to examples.

Example 1. Magnesium hydroxide 11.7 g and hydroxide manganese oxide 3
5.2 g was pulverized and mixed, and heat-treated in air at 950 ° C. for 2 hours. The X-ray diffraction pattern of this sample is ASTM card No. This is in agreement with the data of MgMn ₂ O ₄ of 23-392.

10 g of the MgMn ₂ O ₄ was placed in 500 ml of 1N ammonium peroxodisulfate solution and heated at 70 ° C. for 1 hour or 2 hours. After that, the precipitate is swallowed and washed with water.
It was dried at 0 ° C. The magnesium content and water content of the obtained manganese oxide are shown in Table 1.

The X-ray diffraction pattern of the manganese oxide is shown in FIG.

As is clear from these results, it is understood that the manganese oxide retains the original tetragonal structure even after extraction with magnesium, and a three-dimensional channel structure is formed. It also has a low water content and is suitable as a positive electrode material for non-aqueous batteries.

Example 2. To 90% by weight of the B sample synthesized in Example 1, 6% by weight of acetylene black as a conductive agent and 4% by weight of polytetrafluoroethylene as a binder were added, and a diameter of 15 mm was obtained on a stainless steel plate by a pressure of 3 t / cm ^2. After pressure molding, 1
It was vacuum dried at 50 ° C. for 5 hours to obtain an anode pellet. The cathode was prepared by pressure-bonding a lithium metal foil on a stainless plate. A battery was prepared by using a polypropylene thin film as the separator and using an electrolyte solution obtained by dissolving 1M of lithium perchlorate in a mixed solution of propylene carbonate and tetrahydrofuran in an equal volume. This battery was repeatedly charged and discharged at 1 mA every 3 hours to examine the cycle characteristics. FIG. 2 shows the cycle characteristics of the battery, and it can be seen that there is almost no voltage change up to 20 cycles and the cycle characteristics are good.

[Effects of the Invention] As described above, the manganese compound obtained by extracting magnesium from MgMn ₂ O ₄ has a three-dimensional channel structure, and the insertion / extraction reaction of lithium easily proceeds. It is suitable as a positive electrode active material for secondary batteries, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the X-ray diffraction result of the manganese compound obtained in the present invention, where A and B are A in Table 1, respectively.
It corresponds to the sample and the B sample. FIG. 2 is a characteristic diagram showing charge / discharge cycle characteristics of an organic electrolyte battery using the manganese compound obtained in the present invention as a positive electrode active material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunsaku Kato 2-3-3 Hananomiya-cho, Takamatsu-shi, Kagawa Inside Shikoku Institute of Industrial Technology, Industrial Technology Institute (56) Reference JP-A-63-64919 (JP, A) )

Claims (2)

[Claims] 1. A substance obtained by extracting magnesium from MgMn ₂ O ₄ , which has an interplanar spacing of 4.89 ± 0.05 Å,
2.74 ± 0.03Å, 2.47 ± 0.03Å, 2.0
A manganese compound having an X-ray diffraction peak at 3 ± 0.03Å. 2. The method for producing a manganese compound according to claim 1, wherein MgMn ₂ O ₄ is treated with a solution containing an acidic and oxidizing agent to extract magnesium.