A method for preparing low-sulfur trimanganese tetraoxide

Abstract

The application provides a preparation method of low-sulfur trimanganese tetraoxide and belongs to the technical field of manganese compound preparation. The specific preparation process is as follows: high-sulfur trimanganese tetraoxide is mixed with a composite oxidant to perform an oxidation reaction, and then a reduction reaction is performed under a reducing atmosphere to obtain low-sulfur trimanganese tetraoxide; the composite oxidant is a mixture of two or more than two of titanium dioxide, di-niobium pentoxide, di-vanadium pentoxide, chromium trioxide, di-manganese heptoxide, di-iron trioxide and cerium oxide. The composite oxidant can efficiently remove sulfur in high-sulfur trimanganese tetraoxide, and excellent desulfurization effect can be achieved at a lower oxidant addition amount and at a lower temperature.

Description

Technical Field

[0001] This invention relates to the field of manganese compound preparation technology, and in particular to a method for preparing low-sulfur manganese tetroxide. Background Technology

[0002] Manganese tetroxide (Mn3O4) is widely used in lithium-ion battery cathode materials for the preparation of lithium manganese oxide, ternary materials, and lithium-rich manganese-based cathode materials. Its purity, especially the sulfur impurity content, directly affects the electrochemical performance of the cathode material. Patent application CN 105060349A discloses a method for preparing high-purity, high-density spherical manganese tetroxide. The method involves spraying a manganese salt solution and a carbonate and / or bicarbonate solution into a vertical decomposition furnace, integrating the synthesis and decomposition of intermediate products to obtain manganese tetroxide. The lowest sulfur content in this manganese tetroxide is 78 ppm.

[0003] GB / T 21836-2024, "Manganese Tetraoxide," requires that battery-grade manganese tetraoxide have a sulfur content of ≤50 ppm (0.005%). Therefore, researching a method for preparing low-sulfur manganese tetraoxide is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing low-sulfur manganese tetroxide, so as to solve the problem of high sulfur content in manganese tetroxide prepared in the prior art.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing low-sulfur manganese tetroxide, comprising the following steps: High-sulfur manganese tetroxide is mixed with a composite oxidant and then subjected to an oxidation reaction, followed by a reduction reaction under a reducing atmosphere to obtain low-sulfur manganese tetroxide. The composite oxidant is a mixture of two or more of the following: titanium dioxide, niobium pentoxide, vanadium pentoxide, chromium trioxide, manganese heptaoxide, ferric oxide, and cerium oxide.

[0006] Preferably, the composite oxidant is manganese heptaoxide and cerium oxide.

[0007] Preferably, the mass ratio of manganese heptaoxide to cerium oxide is 1:1 to 3.

[0008] Preferably, the amount of the composite oxidant added is 400~600ppm.

[0009] Preferably, the oxidation reaction is carried out at a temperature of 400-500°C for 0.5-1.5 hours.

[0010] Preferably, the temperature of the reduction reaction is 200~400℃ and the time of the reduction reaction is 1~3h.

[0011] Preferably, the sulfur content of the low-sulfur manganese tetroxide is ≤50ppm.

[0012] Preferably, the low-sulfur manganese tetroxide is used in lithium battery cathode materials.

[0013] The beneficial effects of this invention are: This invention uses a composite oxidant that can efficiently remove sulfur from high-sulfur manganese tetroxide, achieving excellent desulfurization effect at lower temperatures with lower oxidant dosage.

[0014] In this invention, the oxidation reaction temperature is 200~400℃ and the oxidation reaction time is 0.5~1.5h, which greatly saves costs in the preparation of low-sulfur manganese tetroxide.

[0015] The low-sulfur manganese tetroxide obtained by this invention has a sulfur content of ≤50ppm and can be directly used in the preparation of high-performance lithium battery cathode materials to improve the rate performance and cycle stability of the battery. Detailed Implementation

[0016] This invention provides a method for preparing low-sulfur manganese tetroxide, comprising the following steps: High-sulfur manganese tetroxide is mixed with a composite oxidant and then subjected to an oxidation reaction, followed by a reduction reaction under a reducing atmosphere to obtain low-sulfur manganese tetroxide. The composite oxidant is a mixture of two or more of the following: titanium dioxide, niobium pentoxide, vanadium pentoxide, chromium trioxide, manganese heptaoxide, ferric oxide, and cerium oxide.

[0017] In this invention, the composite oxidant is manganese heptaoxide and cerium oxide.

[0018] In this invention, the mass ratio of manganese heptaoxide to cerium oxide is 1:1 to 3, specifically 1:1, 1:2, or 1:3.

[0019] In this invention, the amount of the composite oxidant added is 400~600ppm, specifically 400ppm, 420ppm, 440ppm, 450ppm, 460ppm, 480ppm, 500ppm, 520ppm, 540ppm, 550ppm, 560ppm, 580ppm, and 600ppm.

[0020] In this invention, the temperature of the oxidation reaction is 400~500℃, specifically 400℃, 420℃, 440℃, 450℃, 480℃, or 500℃, and the time of the oxidation reaction is 0.5~1.5h, specifically 0.5h, 0.8h, 1.0h, 1.2h, or 1.5h.

[0021] In this invention, the temperature of the reduction reaction is 200~400℃, specifically 200℃, 220℃, 240℃, 250℃, 260℃, 280℃, 300℃, 320℃, 340℃, 350℃, 360℃, 380℃, and 400℃, and the time of the reduction reaction is 1~3h, specifically 1h, 1.5h, 2.0h, 2.5h, and 3.0h.

[0022] During the oxidation reaction stage, the composite oxidant deeply removes sulfur-containing impurities from high-sulfur manganese tetroxide. In this process, small amounts of Mn are also removed from the surface or lattice defects of manganese tetroxide. 2+ It may be slightly oxidized. In the subsequent reduction stage, the oxidized Mn... 2+ The process involves reduction to ultimately produce high-purity, low-sulfur manganese tetroxide.

[0023] In this invention, the sulfur content of the low-sulfur manganese tetroxide is ≤50ppm.

[0024] In this invention, the low-sulfur manganese tetroxide is used in lithium battery cathode materials.

[0025] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0026] Example 1

[0027] A composite oxidant (manganese heptaoxide and cerium oxide in a mass ratio of 1:2) was added to high-sulfur manganese tetroxide with a sulfur content of 8524 ppm to obtain a mixture. The amount of composite oxidant added was 500 ppm. The mixture was placed in an air atmosphere and oxidized at 450°C for 1 hour. After cooling to room temperature, carbon monoxide gas was introduced and a reduction reaction was carried out at 300°C for 2 hours to obtain low-sulfur manganese tetroxide.

[0028] Example 2

[0029] The difference from Example 1 is that the mass ratio of manganese heptaoxide to cerium oxide is 1:1, while all other conditions are the same.

[0030] Example 3

[0031] The difference from Example 1 is that the mass ratio of manganese heptaoxide to cerium oxide is 1:3, while all other conditions are the same.

[0032] Example 4

[0033] The difference from Example 1 is that the amount of composite oxidant added is 400 ppm, while all other conditions are the same.

[0034] Example 5

[0035] The difference from Example 1 is that the amount of composite oxidant added is 600 ppm, while all other conditions are the same.

[0036] Example 6

[0037] The difference from Example 1 is that the composite oxidant is titanium dioxide and niobium pentoxide in a mass ratio of 1:2, while all other conditions are the same.

[0038] Comparative Example 1

[0039] The difference from Example 1 is that only manganese heptaoxide was added as an oxidant, with the same addition amount of 500 ppm, and all other conditions were the same.

[0040] Comparative Example 2

[0041] The difference from Example 1 is that only cerium oxide was added as an oxidant, with the same addition amount of 500 ppm, and all other conditions were the same.

[0042] Comparative Example 3

[0043] This comparative example uses the method of Example 1 in CN119284961B to prepare low-sulfur manganese tetroxide, that is, using 2000 ppm of niobium pentoxide as a strong oxidant, oxidizing at 500°C for 3 h, and then reducing at 350°C for 3 h.

[0044] The sulfur content and tap density of the low-sulfur manganese tetroxide in Examples 1-6 and Comparative Examples 1-3 were determined, and the results are shown in Table 1. (1) The sulfur content was determined using an inductively coupled plasma optical emission spectrometer (ICP-OES); (2) Tap density: The density shall be determined in accordance with the provisions of GB / T 5162-2021.

[0045] Table 1. Results of sulfur content and tap density tests

[0046] Comparing Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that under the same addition amount, the desulfurization effect of the composite oxidant is significantly better than that of manganese heptaoxide or cerium oxide alone, which indicates that manganese heptaoxide and cerium oxide have a synergistic effect.

[0047] Comparing Examples 1, 4, and 5, the addition of composite oxidant in the range of 400-600 ppm can achieve excellent desulfurization effect, with the best effect at 600 ppm.

[0048] Example 6 uses a composite oxidant of titanium dioxide and niobium pentoxide. The sulfur content in the low-sulfur manganese tetroxide prepared under the same process conditions is 35 ppm, which is lower than the effect of the combination of manganese heptaoxide and cerium oxide.

[0049] As shown in the above embodiments, this invention provides a method for preparing low-sulfur manganese tetroxide. The preparation process involves mixing high-sulfur manganese tetroxide with a composite oxidant and then performing an oxidation reaction, followed by a reduction reaction under a reducing atmosphere to obtain low-sulfur manganese tetroxide. The composite oxidant is a mixture of two or more of titanium dioxide, niobium pentoxide, vanadium pentoxide, chromium trioxide, manganese heptaoxide, ferric oxide, and cerium oxide. This invention utilizes a composite oxidant to efficiently remove sulfur from high-sulfur manganese tetroxide, achieving excellent desulfurization effects at lower temperatures and with lower oxidant dosages.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing low-sulfur manganese tetroxide, characterized in that, Includes the following steps: High-sulfur manganese tetroxide is mixed with a composite oxidant and then subjected to an oxidation reaction, followed by a reduction reaction under a reducing atmosphere to obtain low-sulfur manganese tetroxide. The composite oxidant is a mixture of two or more of the following: titanium dioxide, niobium pentoxide, vanadium pentoxide, chromium trioxide, manganese heptaoxide, ferric oxide, and cerium oxide.

2. The method for preparing low-sulfur manganese tetroxide according to claim 1, characterized in that, The composite oxidant is manganese heptaoxide and cerium oxide.

3. The method for preparing low-sulfur manganese tetroxide according to claim 1 or 2, characterized in that, The mass ratio of manganese heptaoxide to cerium oxide is 1:1~3.

4. The method for preparing low-sulfur manganese tetroxide according to claim 3, characterized in that, The amount of the composite oxidant added is 400~600ppm.

5. The method for preparing low-sulfur manganese tetroxide according to claim 1, 2, or 4, characterized in that, The oxidation reaction is carried out at a temperature of 400-500℃ for 0.5-1.5 hours.

6. The method for preparing low-sulfur manganese tetroxide according to claim 5, characterized in that, The reduction reaction is carried out at a temperature of 200~400℃ for 1~3 hours.

7. The method for preparing low-sulfur manganese tetroxide according to claim 4 or 6, characterized in that, The sulfur content of the low-sulfur manganese tetroxide is ≤50ppm.

8. The method for preparing low-sulfur manganese tetroxide according to claim 7, characterized in that, The low-sulfur manganese tetroxide is used in lithium battery cathode materials.

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