A preparation method of broad distribution manganese manganese oxide

Abstract

A preparation method of wide-distribution trimanganese tetraoxide: when the pH of the reactor bottom liquid is adjusted to 9-10, air is continuously introduced into the reactor, then a manganese salt solution and an alkali solution are introduced, and the reaction system pH is controlled to react between 9-10, and during the reaction, reaction stirring energy dissipation or / and reaction residence time are regulated to control nuclear production, and qualified material is connected when the particle size of the reaction slurry is near the target particle size and the span value is stable between 1-1.5, and the reaction is terminated after the qualified material is sufficient; the obtained material is dehydrated, washed, and dried to obtain wide-distribution trimanganese tetraoxide. The present invention prepares wide-distribution trimanganese tetraoxide by controlling reaction stirring energy dissipation or / and reaction residence time to control nuclear production, and the trimanganese tetraoxide prepared has the characteristics of good sphericity, high tap density, and low specific surface area, thereby facilitating improvement of the electrical properties of lithium-ion battery materials.

Description

Technical Field

[0001] The present invention belongs to the field of synthesis of manganese compounds, and in particular relates to a method for preparing broadly distributed manganese manganese tetroxide used in the field of lithium ion batteries. Background Art

[0002] The traditional production method of lithium manganese oxide (LiMn2O4) mainly uses electrolytic manganese dioxide as the raw material, which is solid-phase calcined with lithium carbonate and corresponding additives under high temperature conditions. However, the lithium manganese oxide prepared by this method has a high impurity content, which is not conducive to the cycle performance of the battery. In recent years, research has discovered that manganese tetraoxide is a high-quality raw material for preparing lithium manganese oxide, and its performance is better than that of manganese dioxide.

[0003] Currently, the main methods for preparing manganese tetraoxide are manganese flake catalytic oxidation and wet co-precipitation oxidation. The manganese tetraoxide produced by the manganese flake catalytic oxidation method has poor sphericity, difficulty in doping, and difficulty controlling the particle size during the preparation process. The wet co-precipitation oxidation method, on the other hand, can produce narrowly distributed manganese tetraoxide with uniform particle size distribution. Alternatively, a pure continuous process with pH-controlled nucleation can produce high-density manganese tetraoxide with a mix of large and small particles. However, this pH-controlled process presents numerous challenges during the preparation process, including the generation of oversized particles, which can lead to uncontrolled particle size and poor sphericity in the resulting product. The pure continuous process with pH-controlled nucleation generally has a narrow span of around 1.1, which is detrimental to improving battery performance. Furthermore, the pH at the nucleation point in this pure continuous process is around 10.7-10.8, but this nucleation process is not continuous, requiring repeated pH control near the nucleation point to ensure stable particle size. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing manganese manganese tetroxide with broad distribution.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A method for preparing broad-distribution manganese manganese tetroxide comprises the following steps:

[0007] (1) Add pure water to the reactor, stir and heat, add alkali solution to adjust the pH of the bottom liquid of the reactor to 9-10, start stirring and continue to introduce air into the reactor, then introduce manganese salt solution and alkali solution into the reactor, and control the pH of the reaction system in the reactor to be between 9-10 for reaction, and monitor the D of the reaction slurry during the reaction process. 50 and span values, where D of the reaction slurry is monitored 50 The specific process of calculating and span values ​​is as follows:

[0008] The target particle size D50 of manganese tetraoxide is set as d, and the particle size of the reaction slurry monitored in real time during the reaction process is d1.

[0009] In the initial stage of the reaction, when the particle size of the reaction slurry is d1≤d-2, the reaction is carried out by a pure batch method of standing and extracting the supernatant;

[0010] When the particle size of the reaction slurry grows to d-2<d1≤d-1, other conditions remain unchanged and the reaction is carried out by overflow feeding. At this time, the reaction stirring energy dissipation is recorded as H, and the reaction residence time is recorded as T;

[0011] When the particle size of the reaction slurry grows to d-1<d1<d+1, the reaction is continued by overflowing and feeding. At this time, other conditions remain unchanged. By increasing the reaction stirring speed to increase the reaction stirring energy dissipation to H*(d+1) / (d-1) or increasing the salt flow rate to reduce the reaction residence time to T*(d-1) / (d+1), the reaction begins to produce nuclei and the span value becomes wider; or other conditions remain unchanged, reducing the reaction stirring speed to reduce the stirring energy dissipation to H*(d-1) / ( d+1), while increasing the salt flow rate to reduce the reaction residence time to T*(d-2) / (d+2), so that the reaction starts to produce nuclei and the span value becomes wider; or other conditions remain unchanged, by increasing the reaction stirring speed to increase the stirring energy dissipation to H*(d+2) / (d-2), while reducing the salt flow rate to increase the reaction residence time to T*(d+2) / (d-2), so that the reaction starts to produce nuclei and the span value becomes wider; so that the particle size of the reaction slurry is continuously maintained at d-1<d1<d+1;

[0012] When the particle size of the reaction slurry is d-1<d1<d+1 and the span value is stable between 1-1.5, qualified materials are added. The reaction is terminated when the qualified materials are sufficient; wherein, span value = (D90-D10) / D50;

[0013] (2) Dehydrating, washing and drying the material obtained in step (2) to obtain broadly distributed manganese manganese tetroxide.

[0014] In the above preparation method, preferably, the reaction stirring energy dissipation H=N p PN 3 D 5 / V; where N p is the energy coefficient of different types of stirring blades, dimensionless; P is the density of the reaction material, generally considered to be 1kg / m 3 ; N is the speed of the reactor agitator, unit is r / s; D is the diameter of the agitator blade, unit is m; V is the volume of the reactor, unit is m 3 .

[0015] In the above preparation method, preferably, the reaction stirring energy dissipation H is 0.8W / L-30W / L.

[0016] In the above preparation method, preferably, the reaction residence time is the ratio of the reactor volume to the sum of the salt and alkali flow rates, the salt refers to a manganese salt solution, and the alkali refers to a sodium hydroxide solution.

[0017] In the above preparation method, preferably, the reaction residence time T is greater than 3.34 h.

[0018] In the above preparation method, preferably, the manganese salt solution is a divalent manganese salt solution with a mass concentration of 20-200 g / L.

[0019] In the above preparation method, preferably, the alkali solution is a sodium hydroxide solution with a mass concentration of 0.1-600 g / L.

[0020] In the above preparation method, preferably, in step (1), the reaction temperature is 60°C-80°C.

[0021] In the above preparation method, preferably, in step (1), air is continuously introduced into the reactor during the reaction.

[0022] In the above preparation method, preferably, in step (1), the particles of the manganese tetraoxide are spherical, the main content of the manganese tetraoxide is Mn ≥ 70%, and the specific surface area is 0.3 cm 3 / g-2cm 3 / g, tap density not less than 2g / cm 3 , the span value is 1-1.5.

[0023] The present invention adopts wet co-precipitation oxidation technology, and co-precipitation is divided into two steps, and the first step is pure batch process, and the second step is pure continuous process, and pure batch process is by standing and settling and pumping out supernatant mode to allow reaction particle size to grow gradually, and standing and settling and pumping out supernatant mode can improve the solid content of reaction system, and along with the improvement of reaction solid content, particle and particle collision more and more, and particle and particle collision makes the sphericity of agglomerated manganese oxide more and more good. When reaction particle size grows to approach target particle size, reaction process is switched to pure continuous process by pure batch process, because particle sphericity becomes better at this moment, by increasing reaction stirring speed to improve stirring energy dissipation or increasing salt flow to reduce reaction residence time, reaction can produce small nucleus, span value becomes wide, and particle size growth rate slows down, and finally makes reaction particle size near target value. When the energy dissipation of reaction stirring increases, the particles flowing at a higher flow rate form a relative motion with the growing crystal particles. Under the action of the shear stress of the boundary layer of the fluid, some particles attached to the crystal surface are swept off, and the swept-off particles can produce small particles; and the reason why increasing the salt flow rate reduces the reaction residence time and nucleation is that the increase in salt flow rate causes the local saturation in the reactor to be too high, making it easier to produce small particles.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] (1) The present invention controls the nucleation production by controlling the reaction stirring energy dissipation and / or the reaction residence time to prepare a broadly distributed manganese tetraoxide. Compared with the broadly distributed manganese tetraoxide precursor obtained by conventionally controlling the nucleation production by pH, the manganese tetraoxide prepared by this method has better sphericity, higher tap density, and lower specific surface area, thereby being more conducive to improving the electrical properties of lithium-ion battery materials.

[0026] (2) The present invention controls the nucleation by changing the stirring energy dissipation and / or the reaction residence time under low pH conditions, so that oversized particles of manganese tetraoxide will not appear, and the processing performance of the positive electrode material is good.

[0027] (3) The manganese manganese oxide prepared by the present invention has a wide particle size distribution with a span value of 1-1.5. The wider diameter distribution can increase the compaction density of the positive electrode material powder, thereby improving the electrical performance of the battery material.

[0028] (4) The manganese manganese oxide prepared by the present invention has the characteristic of good sphericity, which can be beneficial to downstream battery cell manufacturers to improve the fluidity of dry coating.

[0029] (5) The present invention controls the nucleus production by changing the stirring energy dissipation and / or the reaction residence time. Compared with the traditional pure continuous process of controlling the nucleus production by pH, the nucleus production process of the present invention is more stable. In addition, the nucleus production process of the present invention is continuous and does not require human regulation, which is more conducive to the scale-up production of the product on the production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 1 is an electron microscope image of trimanganese tetraoxide prepared in Example 1 of the present invention.

[0031] Figure 2 1 is an electron microscope image of trimanganese tetraoxide prepared in Example 2 of the present invention.

[0032] Figure 3 1 is the XRD pattern of trimanganese tetraoxide prepared in Example 2 of the present invention.

[0033] Figure 4 1 is an electron microscope image of trimanganese tetraoxide prepared in Example 3 of the present invention.

[0034] Figure 5 1 is an electron microscope image of trimanganese tetraoxide prepared in Example 4 of the present invention.

[0035] Figure 6 1 is an electron microscope image of trimanganese tetraoxide prepared in Comparative Example 1 of the present invention.

[0036] Figure 7 It is a process flow chart of the entire reaction of Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0037] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0038] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0039] Unless otherwise specified, all reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

[0040] Example 1:

[0041] A preparation method of broad distribution manganese tetraoxide of the present invention, the process flow chart of which is as follows Figure 7 As shown, the following steps are included:

[0042] (1) Manganese sulfate crystals were added to hot pure water and dissolved to prepare a manganese sulfate solution with a manganese ion concentration of 110 g / L; at the same time, a sodium hydroxide solution with a mass concentration of 430 g / L was prepared.

[0043] (2) Prepare an air flow meter, a salt and alkali feed tube, and a peristaltic pump. Use the peristaltic pump to calibrate the metal salt flow rate to 140 mL / min and the alkali flow rate to 56 mL / min.

[0044] (3) Clean the 100L reactor, add pure water and completely submerge the reactor blades, turn on the compressed air to continuously introduce air into the reactor, start stirring and heat the reactor at the same time, when the temperature of the reactor rises to 70°C, add the sodium hydroxide solution prepared in step (1) into the reactor, and adjust the pH of the reactor bottom liquid to about 9.5.

[0045] (4) The target particle size D50 of manganese tetraoxide is set to d=10 μm, and the manganese sulfate solution and sodium hydroxide solution prepared in step (1) are continuously pumped into the reactor by a peristaltic pump, and the flow rate of the manganese sulfate solution is controlled to be 140 mL / min and the flow rate of the sodium hydroxide solution is controlled to be 56 mL / min. At this time, the reaction residence time is about 8.5 h, the reaction temperature is 70°C, the stirring speed is 10 r / s, the upper blade of the reactor is a four-blade straight blade with a blade diameter of 0.158 m and an energy coefficient of 5, and the lower blade is a 45° four-blade oblique blade with a blade diameter of 0.158 m and an energy coefficient of 1.4. The energy dissipation of the upper and lower blades is calculated by the formula and the sum is obtained to obtain the reaction stirring energy dissipation of 6.3 W / L; the air flow rate is maintained at 30 L / min, and the pH of the reaction process is controlled at 9- 10, and continue feeding. After the reaction reaches the liquid level full, start to let it stand and settle to extract the supernatant, then start stirring and continue feeding. Repeat this process until the slurry particle size D50 reaches 8μm, and the reaction is full and continuous overflow feeding begins. When the particle size rises to 9μm, other reaction conditions remain unchanged, and the reaction stirring energy dissipation is increased to 7.7W / L, that is, the reaction stirring speed is increased to 10.7r / s. After a period of time, the reaction begins to produce nuclei, and the particle size growth rate slows down. The final particle size is maintained between 9-11μm, and the span value is between 1-1.5. When the particle size and span value continue to be stable, qualified material is started. After the material is sufficient, the feeding is stopped to end the reaction, and the overflowed qualified material is combined to obtain a manganese tetraoxide precursor material with a particle size of 10.1μm and a diameter distance of 1.21.

[0046] (5) The material obtained in step (4) was dehydrated to remove the mother liquor, washed with hot pure water at 60°C, and then dehydrated again. This process was repeated 10 times, and finally dried in an oven at 140°C for 12 hours. The material was sieved to remove the magnetism, and a spherical and broadly distributed manganese tetraoxide product was obtained. The electron microscope image is shown in FIG. Figure 1 shown.

[0047] The manganese tetraoxide prepared in this example was sent for inspection and analysis. The finished product had a Mn content of 70.5% and a specific surface area of ​​0.51 cm 3 / g, and the tap density is 2.71g / cm 3 , particle size D50 is 10.1μm, and span value is 1.21.

[0048] The sintering evaluation of the manganese oxide raw material prepared in this example was carried out. The manganese oxide powder was mixed with lithium carbonate according to a lithium-manganese molar ratio of 0.5036 and sintered at 700°C for 14 hours in an air atmosphere. The electrochemical data of the lithium manganate obtained by sintering were as follows: the powder compaction density was 3.06 g / cm 3 The first discharge capacity at 0.1C is 132.4mAh / g, the first efficiency is 97.9%, and the capacity retention rate for 51 cycles at 60°C is 96.1%.

[0049] Example 2:

[0050] A preparation method of broad distribution manganese tetraoxide of the present invention, the process flow chart of which is as follows Figure 7 As shown, the following steps are included:

[0051] (1) Manganese sulfate crystals were added to hot pure water to dissolve and prepare a manganese sulfate solution with a manganese ion concentration of 110 g / L; at the same time, a sodium hydroxide solution with a mass concentration of 430 g / L was prepared.

[0052] (2) Prepare an air flow meter, a salt and alkali feed tube, and a peristaltic pump. Use the peristaltic pump to calibrate the metal salt flow rate to 140 mL / min and the alkali flow rate to 56 mL / min.

[0053] (3) Clean the 100L reactor, add pure water and completely submerge the reactor blades, turn on the compressed air to continuously introduce air into the reactor, start stirring and heat the reactor at the same time, when the temperature of the reactor rises to 70°C, add the sodium hydroxide solution prepared in step (1) into the reactor, and adjust the pH of the reactor bottom liquid to about 9.5.

[0054] (4) The target particle size D50 of manganese tetraoxide was set to d=10 μm, and the manganese sulfate solution and sodium hydroxide solution prepared in step (1) were continuously pumped into the reactor using a peristaltic pump. The flow rate of the manganese sulfate solution was controlled to be 140 mL / min, and the flow rate of the sodium hydroxide solution was controlled to be 56 mL / min. At this time, the reaction residence time was about 8.5 h, the reaction temperature was 70°C, the stirring speed was 10 r / s, the upper blade of the reactor was a four-blade straight blade with a blade diameter of 0.158 m and an energy coefficient of 5, and the lower blade was a 45° four-blade inclined blade with a blade diameter of 0.158 m and an energy coefficient of 1.4. By calculating the energy dissipation of the upper and lower blades and summing them, the reaction stirring energy dissipation was obtained to be 6.3 W / L. The air flow rate was maintained at 30 L / min, and the pH value of the reaction process was controlled between 9-10 and continuous feeding was carried out. After the reaction reached the liquid level full, the kettle was allowed to stand and settle to extract the supernatant, and then stirring was started to continue feeding. This was repeated until the particle size D50 reached 8 μm. The reaction was continued until the kettle was full and overflow feeding began. When the particle size grew to 9 μm, the other reaction conditions remained unchanged, and the reaction residence time was reduced to 6.95 hours, that is, the salt flow rate was increased to 171.3 mL / min, and the alkali flow rate was increased to 68.5 mL / min. After a period of time, the reaction began to produce nuclei, and the particle size growth rate slowed down. The final particle size was maintained between 9-11 μm, and the span value was between 1-1.5. When the particle size and span value remained stable, qualified materials were started until the material was sufficient, and the feeding was stopped to end the reaction. The overflowed qualified materials were combined to obtain a manganese tetraoxide precursor slurry with a particle size of 9.93 μm and a diameter distance of 1.32.

[0055] (5) The material obtained in step (4) was dehydrated to remove the mother liquor, washed with 60°C hot pure water, and then dehydrated. This process was repeated 10 times, and finally dried in an oven at 140°C for 12 hours. The material was sieved to remove magnetism and obtain a broadly distributed manganese tetraoxide product. The electron microscope image is as follows: Figure 2 Its XRD pattern is shown as Figure 3 shown.

[0056] The manganese tetraoxide obtained in this example was sent for inspection and analysis. The Mn content in the finished product was 70.9% and the specific surface area was 0.82 cm 3 / g, tap density 2.62g / cm 3 , particle size D50 is 9.93μm, and span value is 1.32.

[0057] The sintering evaluation of the manganese oxide powder obtained in this example was carried out. The manganese oxide powder was mixed with lithium carbonate according to a lithium-manganese molar ratio of 0.5036 and sintered at 700°C in an air atmosphere for 14 hours. The electrochemical data of the lithium manganate obtained by sintering were as follows: the powder compaction density was 3.12 g / cm 3The first discharge capacity at 0.1C is 133.7mAh / g, the first efficiency is 97.9%, and the capacity retention rate for 51 cycles at 60°C is 96.9%.

[0058] Example 3:

[0059] A preparation method of broad distribution manganese tetraoxide of the present invention, the process flow chart of which is as follows Figure 7 As shown, the following steps are included:

[0060] (1) Add manganese sulfate crystals into hot pure water and stir to dissolve, thereby preparing a manganese sulfate solution with a manganese ion concentration of 110 g / L; at the same time, prepare a sodium hydroxide solution with a mass concentration of 430 g / L.

[0061] (2) Prepare an air flow meter, a salt and alkali feed tube, and a peristaltic pump. Use the peristaltic pump to calibrate the metal salt flow rate to 140 ml / min and the alkali flow rate to 56 ml / min.

[0062] (3) Clean the 100L reactor, add pure water and completely submerge the reactor blades, turn on the compressed air to continuously introduce air into the reactor, start stirring and heat the reactor at the same time, when the temperature of the reactor rises to 70°C, add the sodium hydroxide solution prepared in step (1) into the reactor, and adjust the pH of the reactor bottom liquid to about 9.5.

[0063] (4) The manganese sulfate solution and the sodium hydroxide solution prepared in step (1) were continuously pumped into the reactor using a peristaltic pump, and the flow rate of the manganese sulfate solution was controlled to be 140 ml / min and the flow rate of the sodium hydroxide solution was controlled to be 56 ml / min. At this time, the reaction residence time was about 8.5 h, the reaction temperature was 70°C, the reaction stirring speed was 10 r / s, the upper blade of the reactor was a four-blade straight blade with a blade diameter of 0.158 m and an energy coefficient of 5, and the lower blade was a 45° four-blade inclined blade with an energy coefficient of 1.4. By calculating the energy dissipation of the upper and lower blades and summing them, the reaction stirring energy dissipation was obtained to be 6.3 W / L. The air flow rate was maintained at 30 L / min, and the pH value during the reaction was controlled between 9-10 and continuous feeding was performed. After the reaction reached the full liquid level, the reaction was allowed to stand and settle to extract the supernatant, and then stirring was started to continue feeding. This process was repeated until the particle size D50 reached 8 μm. The reaction was continued until the kettle was full and overflow feeding was started. When the particle size rose to 9 μm, other conditions remained unchanged, and the reaction stirring energy dissipation was reduced to 5.15 W / L, that is, the stirring speed was reduced to 9.4 r / s, and the reaction residence time was reduced to 5.67 h. At this time, the salt flow rate was increased to 208.3 mL / min, and the alkali flow rate was increased to 83.3 mL / min. After a period of time, the reaction began to produce nuclei, and the particle size growth rate slowed down. The final particle size was maintained between 9-11 μm, and the span value was between 1-1.5. When the particle size and span value remain stable, qualified material is added and the reaction is terminated after sufficient material is added, thereby obtaining a manganese tetraoxide precursor slurry with a particle size of 10.31 μm and a diameter distance of 1.39.

[0064] (5) The slurry obtained in step (4) was dehydrated to remove the mother liquor, washed with hot pure water at 60°C, and then dehydrated again. This process was repeated 10 times. Finally, it was dried in an oven at 140°C for 12 hours, sieved and demagnetized to obtain a spherical manganese tetraoxide product with wide distribution. The electron microscope image is as follows: Figure 4 shown.

[0065] The manganese tetraoxide prepared in this example was sent for inspection and analysis. The Mn content of the finished product was 70.4%, and the specific surface area was 0.91 cm 3 / g, and the tap density is 2.53g / cm 3 , particle size D50 is 10.31μm, and span value is 1.39.

[0066] The sintering evaluation of the trimanganese tetraoxide obtained in this example was carried out. The trimanganese tetraoxide powder was mixed with lithium carbonate according to a lithium-manganese molar ratio of 0.5036. The mixture was sintered at 700°C for 14 hours in an air atmosphere. The electrochemical data of the lithium manganate obtained by sintering were as follows: the powder compaction density was 3.09 g / cm 3The first discharge capacity at 0.1C is 132.8mAh / g, the first efficiency is 98.9%, and the capacity retention rate for 51 cycles at 60°C is 97.1%.

[0067] Example 4:

[0068] A preparation method of broad distribution manganese tetraoxide of the present invention, the process flow chart of which is as follows Figure 7 As shown, the following steps are included:

[0069] (1) Manganese sulfate crystals are added to hot pure water to prepare a manganese sulfate solution with a manganese ion concentration of 110 g / L; at the same time, a sodium hydroxide solution with a mass concentration of 430 g / L is prepared.

[0070] (2) Prepare an air flow meter, a salt and alkali feed tube, and a peristaltic pump. Use the peristaltic pump to calibrate the metal salt flow rate to 140 mL / min and the alkali flow rate to 56 mL / min.

[0071] (3) Clean the 100L reactor, add pure water and completely submerge the reactor blades, turn on the compressed air to continuously introduce air into the reactor, start stirring and heat the reactor at the same time, when the temperature of the reactor rises to 70°C, add the sodium hydroxide solution prepared in step (1) into the reactor, and adjust the pH of the reactor bottom liquid to about 9.5.

[0072] (4) The manganese sulfate solution and sodium hydroxide solution prepared in step (1) were continuously pumped into the reactor using a peristaltic pump, and the flow rate of the manganese sulfate solution was controlled to be 140 mL / min and the flow rate of the sodium hydroxide solution was controlled to be 56 mL / min. At this time, the reaction residence time was about 8.5 h, the reaction temperature was 70°C, the stirring speed was 10 r / s, the upper blade of the reactor was a four-blade straight blade with a blade diameter of 0.158 m and an energy coefficient of 5, and the lower blade was a 45° four-blade inclined blade with a blade diameter of 0.158 m and an energy coefficient of 1.4. By calculating the energy dissipation of the upper and lower blades and summing them, the reaction stirring energy dissipation was obtained to be 6.3 W / L. Maintain an air flow rate of 30L / min, control the pH value between 9-10 during the reaction process, and continue feeding. After the reaction reaches the full level, let it stand and settle to extract the supernatant, then start stirring and continue feeding. Repeat this process until the slurry particle size D50 reaches 8μm, then the reaction reaches the full level and continuous overflow feeding begins. When the particle size grows to 9μm, other conditions remain unchanged, increase the reaction stirring energy dissipation to 9.45W / L, that is, increase the reaction stirring speed to 11.4r / s, and increase the reaction residence time to 12.75h, that is, reduce the salt flow rate to 93.3mL / min and the alkali flow rate to 37.3mL / min. After a period of time, the reaction begins to produce nuclei, the particle size growth rate slows down, and the final particle size is maintained between 9-11μm and the span value is between 1-1.5. When the particle size and span value remain stable, start adding qualified materials. Stop feeding and end the reaction after sufficient materials are added, and merge the overflow qualified materials.

[0073] (5) The reaction slurry obtained in step (4) was dehydrated to remove the mother liquor, washed with hot pure water at 60°C, and then dehydrated again. This process was repeated 10 times, and finally dried in an oven at 140°C for 12 hours. The product was sieved to remove magnetism and obtain a spherical manganese tetraoxide with wide distribution. The electron microscope image is as follows: Figure 5 shown.

[0074] The manganese tetraoxide obtained in this example was sent for inspection and analysis. The finished product had a Mn content of 71%, a specific surface area of ​​0.45 cm3 / g, and a tap density of 2.81 g / cm 3 , particle size D50 is 10.29μm, and span value is 1.27.

[0075] The sintering evaluation of the trimanganese tetraoxide obtained in this example was carried out. The trimanganese tetraoxide powder was mixed with lithium carbonate according to a lithium-manganese molar ratio of 0.5036 and sintered at 700°C for 14 hours in an air atmosphere. The electrochemical data of the lithium manganate obtained by sintering were as follows: the powder compaction density was 3.08 g / cm 3 The first discharge capacity at 0.1C is 133.8mAh / g, the first efficiency is 97.9%, and the capacity retention rate is 97.9% after 51 cycles at 60°C.

[0076] Comparative Example 1:

[0077] The preparation method of the broad distribution manganese tetraoxide of this comparative example comprises the following steps:

[0078] (1) adding manganese sulfate crystals to hot pure water to prepare a manganese sulfate solution with a manganese ion concentration of 110 g / L; simultaneously, preparing a sodium hydroxide solution with a mass concentration of 430 g / L;

[0079] (2) Prepare an air flow meter, a salt and alkali feed tube, and a peristaltic pump. Use the peristaltic pump to calibrate the metal salt flow rate to 140 mL / min and the alkali flow rate to 56 mL / min.

[0080] (3) Clean the 100L reactor, add pure water and completely submerge the reactor blades, turn on the compressed air to continuously introduce air into the reactor, start stirring and heat the reactor at the same time, when the temperature of the reactor rises to 70°C, add the sodium hydroxide solution prepared in step (1) into the reactor, and adjust the pH of the reactor bottom liquid to about 9.5.

[0081] (4) The target particle size D50 of manganese tetraoxide is set to d=10 μm, and the manganese sulfate solution and sodium hydroxide solution prepared in step (1) are continuously pumped into the reactor by a peristaltic pump. The flow rate of manganese sulfate solution is controlled to be 140 mL / min, and the flow rate of sodium hydroxide solution is controlled to be 56 mL / min. At this time, the reaction residence time is about 8.5 h, the reaction temperature is 70°C, the reaction stirring speed is 10 r / s, the upper blade of the reactor is a four-blade straight blade with a blade diameter of 0.158 m and an energy coefficient of 5, and the blade diameter is 0.158 m. The lower blade is a 45° four-blade oblique blade with a blade diameter of 0.158 m and an energy coefficient of 1.4. By calculating the energy consumption of the upper and lower blades, the energy consumption of the upper and lower blades is: The energy dissipation of the reaction stirring was obtained by dissipation and summation, which was 6.3W / L. The air flow rate was maintained at 30L / min, and the pH of the reaction process was controlled between 9-10 and continuous feeding was carried out. After the reaction kettle was full, overflow began, until the particle size grew to 9μm, and the pH was gradually adjusted to about 10.8. The reaction began to produce nuclei, and after a period of time, the particle size growth rate slowed down. When the particle size grew to about 10μm, the reaction pH was adjusted back and forth near pH=10.8, and finally the slurry particle size was maintained between 9-11μm, and the span value was between 1-1.5. When the slurry particle size and span value remained stable, qualified materials were started to be added. After enough materials were added, feeding was stopped to end the reaction, and the overflowed qualified materials were merged.

[0082] (5) The reaction slurry obtained in step (4) was dehydrated to remove the mother liquor, washed with hot pure water at 60°C, and then dehydrated again. This process was repeated 10 times, and finally dried in an oven at 140°C for 12 hours. The product was sieved to remove magnetism and obtain a spherical manganese tetraoxide with wide distribution. The electron microscope image is as follows: Figure 6 shown.

[0083] The manganese tetraoxide obtained in this comparative example was sent for inspection and analysis. The Mn content of the finished product was 69.9%, and the specific surface area was 1.1 cm 3 / g, tap density is 2.01g / cm 3 , particle size D50 = 9.89 μm, span value 1.08.

[0084] The sintering evaluation of the manganese tetraoxide prepared in this comparative example was carried out. According to the lithium-manganese molar ratio of 0.5036, the manganese tetraoxide was mixed with lithium carbonate and sintered at 700 ° C for 14 h in an air atmosphere. The electrochemical data of the lithium manganate obtained by sintering were as follows: the powder compaction density was 2.73 g / cm 3 The first discharge capacity at 0.1C is 127.8mAh / g, the first efficiency is 97.1%, and the capacity retention rate for 51 cycles at 60°C is 95.3%.

Claims

1. A method for preparing broadly distributed manganese manganese oxide, characterized in that: The following steps are involved: (1) Add pure water to the reactor, stir and heat it, add alkali solution to adjust the pH of the bottom liquid of the reactor to 9-10, start to continuously introduce air into the reactor, then introduce manganese salt solution and alkali solution into the reactor, and control the pH of the reaction system in the reactor to be between 9-10 for reaction. Monitor the D of the reaction slurry during the reaction process. 50 and span values, where D of the reaction slurry is monitored 50 The specific process of calculating and span values ​​is as follows: The target particle size D50 of manganese tetraoxide is set as d, and the particle size of the reaction slurry monitored in real time during the reaction process is d1. In the initial stage of the reaction, when the particle size of the reaction slurry is d1≤d-2, the reaction is carried out by a pure batch method of standing and extracting the supernatant; When the particle size of the reaction slurry grows to d-2<d1≤d-1, other conditions remain unchanged and the reaction is carried out by overflow feeding. At this time, the reaction stirring energy dissipation is recorded as H, and the reaction residence time is recorded as T; When the particle size of the reaction slurry grows to d-1<d1<d+1, continue to react by overflowing and feeding, at this time, other conditions remain unchanged, increase the reaction stirring energy dissipation to H*(d+1) / (d-1), or reduce the reaction residence time to T*(d-1) / (d+1), so that the reaction starts to produce nuclei and the span value becomes wider; or other conditions remain unchanged, reduce the reaction stirring energy dissipation to H*(d-1) / (d+1) and reduce the reaction residence time to T*(d-2) / (d+2), so that the reaction starts to produce nuclei and the span value becomes wider; or other conditions remain unchanged, increase the reaction stirring energy dissipation to H*(d+2) / (d-2) and increase the reaction residence time to T*(d+2) / (d-2), so that the reaction starts to produce nuclei and the span value becomes wider; so that the particle size of the reaction slurry is continuously maintained at d-1<d1<d+1; When the particle size of the reaction slurry is stable between d-1<d1<d+1 and the span value is between 1-1.5, qualified materials are added. When there is enough qualified materials, the reaction is terminated. Wherein, the reaction stirring energy dissipation H=N p PN 3 D 5 / V,N p is the energy coefficient of different types of stirring blades, dimensionless; P is the density of the reaction material, generally considered to be 1kg / m 3 ; N is the speed of the reactor agitator, in r / s; D is the diameter of the agitator blade, in m; V is the volume of the reactor, in m 3 ; The reaction residence time is the ratio of the reactor volume to the saline and alkali flow rate; (2) Dehydrating, washing and drying the material obtained in step (1) to obtain broadly distributed manganese manganese tetroxide.

2. The preparation method according to claim 1, wherein The reaction stirring energy dissipation H is 0.8W / L-30W / L.

3. The preparation method according to claim 1, wherein The reaction residence time T>3.34h.

4. The preparation method according to claim 1, wherein The manganese salt solution is a divalent manganese salt solution with a mass concentration of 20-200 g / L.

5. The preparation method according to claim 1, wherein The alkali solution is a sodium hydroxide solution with a mass concentration of 0.1-600g / L.

6. The preparation method according to claim 1, wherein In step (1), the reaction temperature is 60°C-80°C.

7. The preparation method according to claim 1, wherein In step (1), the particles of the manganese tetraoxide are spherical, the main content of the manganese tetraoxide is Mn ≥ 70%, and the specific surface area is 0.3 cm 3 / g-2cm 3 / g, tap density not less than 2g / cm 3 , the span value is 1-1.5.

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