Iron-doped manganous-manganic oxide material as well as preparation method and application thereof

Abstract

The invention discloses an iron-doped manganous-manganic oxide material and a preparation method and application thereof.According to the iron-doped manganous-manganic oxide material and the preparation method and application thereof, manganese sulfate serves as a manganese source, DTPA ferric ammonium salt serves as a complexing agent and a doping agent, ammonia water serves as alkali liquor, ethyl alcohol serves as a dispersing agent, and the preparation process is optimized in a targeted mode; the iron-doped manganous-manganic oxide material with uniform particle size distribution is prepared, the doping uniformity of the iron element in large-size micron-sized manganous-manganic oxide particles is improved while the sulfur content in the material is reduced, and the product is good in particle size uniformity and high in tap density. In addition, the process provided by the invention also has the characteristics of simple flow, easiness in operation, low input cost, high economic benefit and large-scale popularization and application.

Description

Technical Field

[0001] The present invention relates to electrode materials and a preparation method thereof, and particularly relates to an iron-doped manganese tetroxide material, a preparation method thereof and an application thereof, belonging to the technical field of electrode materials and their preparation. Background Art

[0002] As one of the current main cathode materials for lithium-ion batteries, lithium manganate has broad application prospects due to its low price, high safety, good rate performance and excellent low-temperature performance. The precursors used for the preparation of lithium manganate usually include MnO, MnO 2 , Mn 2 O 3 , Mn 3 O 4 , MnOOH, MnCO 3 etc. Different precursors will directly affect the cycle performance, rate performance, specific capacity, morphology, etc. of lithium manganate.

[0003] Among them, Mn 3 O 4 has received extensive attention in recent years as a precursor for the preparation of lithium manganate due to its distinct advantages. First, Mn 3 O 4 and lithium manganate belong to the spinel structure, and have a smaller phase change stress during the preparation of lithium manganate; second, Mn 3 O 4 prepared by the oxidation of the manganese salt solution through the controlled crystallization method is easy to control the morphology and impurities, and can achieve more uniform doping modification; in addition, this method is conducive to large-scale production and has a high production efficiency. However, due to the existence of Mn 3+ in the lithium manganate cathode material, on the one hand, it will cause the occurrence of the Jahn-Teller effect, resulting in the collapse of the spinel structure of lithium manganate; on the other hand, under the erosion of the electrolyte, Mn 3+ undergoes a disproportionation reaction to generate Mn 2+ and Mn 4+ , among which Mn 2+ will dissolve in the electrolyte and adhere to the surface of the negative electrode, causing the loss of manganese. The above two points seriously affect the rate performance and cycle stability life of lithium manganate, greatly increasing the impedance of the battery, and are important obstacles to the further popularization of lithium manganate.

[0004] In addition, the manganese tetraoxide prepared by the one-step oxidation method of manganese sulfate will lead to the problem of high sulfur content. Excessive sulfur content will lead to a decrease in the capacity of lithium manganate produced by subsequent mixed lithium sintering, an increase in electrochemical impedance, and an increase in the self-discharge rate of the battery, which seriously affects the electrochemical performance of lithium manganate batteries. This is because manganese sulfate will generate basic manganese sulfate during hydrolysis, and the priority of basic manganese sulfate oxidation to manganese tetraoxide is lower than that of manganese hydroxide generated at the same time. Therefore, during the primary particle agglomeration process of manganese tetraoxide, it will not have time to fully oxidize and be wrapped in the particles, making it difficult to remove by washing. Excessive sulfur content will lead to a decrease in the capacity of lithium manganate produced by subsequent mixed lithium sintering, an increase in electrochemical impedance, and an increase in the self-discharge rate of the battery, which seriously affects the electrochemical performance of lithium manganate batteries. Although some patents introduce various dispersants to ensure the oxidation time of basic manganese sulfate in the process of preparing manganese tetraoxide by the one-step oxidation method of manganese sulfate, nano-scale manganese tetraoxide is often prepared, with too low a tap density and too large a specific surface area, which is difficult to meet the requirements of battery-grade manganese tetraoxide. In view of the problem that the sulfur content of the product is too high when manganese tetraoxide is prepared by oxidation method using manganese sulfate as raw material, a two-step oxidation method is generally used to reduce the sulfur content, that is, firstly, manganese sulfate is allowed to generate manganese hydroxide precipitation in an alkaline environment, the precipitate is washed and filtered in an environment protected by inert gas, and then the oxidant is introduced into the slurry again for oxidation.

[0005] In Patent CN103172117B, manganese sulfate is first precipitated as manganese hydroxide in a strong alkaline environment. After washing and filtering, it is added to a sodium hydroxide solution for slurrying and oxidized by introducing air to obtain a manganese tetraoxide product. However, when washing, filtering, and transferring the intermediate product manganese hydroxide, this method is not carried out under the protection of an inert gas, which easily generates other manganese oxides and affects the purity of the final manganese tetraoxide. In Patent CN115744994A, a manganese hydroxide suspension is first formed by reacting manganese sulfate in a sodium hydroxide solution under a nitrogen environment, and then the suspension is added to a sodium hydroxide solution and oxidized by introducing air to form manganese tetraoxide. Although this method uses a strong alkaline solution in the hydrolysis step and the oxidation step is also carried out in an alkaline solution, which inhibits the formation of basic manganese sulfate, the consumption of the alkaline solution is too large. In Patent CN103466720A, ammonia water is first used as a complexing agent and a neutralizing agent to prepare manganese tetraoxide by a one-step oxidation method, and then the product is calcined at 950 °C to remove sulfur in an environment with a protective gas introduced. Although the sulfur content after calcination reaches the level of 100 ppm, the calcination process needs to be carried out at a high temperature of 950 °C, which will cause greater energy consumption. On the other hand, when manganese tetraoxide is calcined at a high temperature in an inert gas atmosphere, there is also a possibility of being reduced to a lower-valent manganese oxide, affecting the product purity. In Patent CN100448784C, the rate of increase in pH during the reaction is controlled by calculating according to the relationship between pH and the activity of manganese ions to avoid the hydrolysis of manganese ions, reduce the generation of basic manganese sulfate, and directly oxidize manganese ions to manganese tetraoxide. This method is theoretically feasible, but in specific implementation, it has high requirements for operation accuracy and equipment. For example, it is necessary to judge the concentration of manganese ions in real time and accurately calculate and regulate the pH accordingly, which puts higher requirements on the operating equipment and increases the threshold for production investment. SUMMARY OF THE INVENTION

[0006] Aiming at the problems in the prior art that the manganese tetraoxide prepared by the one-step oxidation method of manganese sulfate has a high sulfur content and the presence of Mn 3+ will cause problems such as the Jahn-Teller effect, the present invention provides an iron-doped manganese tetraoxide material and a preparation method thereof. By using manganese sulfate as the manganese source, ammonium iron(III) DTPA as the complexing agent and doping agent, and ammonia water as the alkaline solution, an iron-doped manganese tetraoxide material with a uniform particle size distribution is prepared. At the same time, the process is improved by introducing ethanol as a dispersant in the early stage of the reaction and removing the dispersant in the middle stage of the reaction, which not only reduces the sulfur content in the product but also ensures the sphericity and tapped density of the product, improving and ensuring the overall performance of the iron-doped manganese tetraoxide material.

[0007] To achieve the above technical objectives, the technical solutions adopted by the present invention are specifically described as follows:

[0008] According to the first embodiment of the present invention, a preparation method of an iron-doped manganese tetraoxide material is provided:

[0009] A preparation method of an iron-doped manganese tetraoxide material, the preparation method comprising the following steps:

[0010] 1) React a manganese sulfate solution, an ammonium iron(III) DTPA solution, and ammonia water continuously in the presence of an oxidizing agent and a dispersant, and obtain a crude product after the reaction is completed.

[0011] 2) Wash, filter, and dry the crude product in sequence to obtain the iron-doped manganese tetraoxide material.

[0012] Preferably, the manganese sulfate solution is an aqueous solution of a manganese sulfate salt, and the concentration of the manganese sulfate salt is 0.5 - 2 mol / L, preferably 0.8 - 1.8 mol / L, more preferably 1 - 1.5 mol / L, such as one of 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L. The feeding rate of the manganese sulfate solution is 30 - 80 mL / h, preferably 40 - 70 mL / h, more preferably 45 - 65 mL / h, such as one of 30 mL / h, 32 mL / h, 35 mL / h, 38 mL / h, 40 mL / h, 42 mL / h, 45 mL / h, 48 mL / h, 50 mL / h, 55 mL / h, 60 mL / h, 65 mL / h, 70 mL / h, 75 mL / h, 80 mL / h.

[0013] Preferably, the ammonium iron(III) DTPA solution is an aqueous solution of an ammonium iron(III) DTPA, and the concentration of the ammonium iron(III) DTPA is 0.03 - 0.3 times the concentration of the manganese sulfate salt, preferably 0.04 - 0.25 times, more preferably 0.05 - 0.2 times. The feeding rate of the ammonium iron(III) DTPA is 3 - 25 mL / h, preferably 5 - 20 mL / h, more preferably 8 - 15 mL / h, such as one of 3 mL / h, 4 mL / h, 5 mL / h, 6 mL / h, 7 mL / h, 8 mL / h, 9 mL / h, 10 mL / h, 12 mL / h, 15 mL / h, 18 mL / h, 20 mL / h, 22 mL / h, 25 mL / h.

[0014] It should be noted that in the present invention, the molar ratio of the addition amount of ammonium ferric DTPA to the addition amount of manganese sulfate per unit time (for example, calculated as 1 h) is preferably between 0.005-0.5:1, more preferably 0.01-0.3:1, such as one of 0.005:1, 0.008:1, 0.01:1, 0.015:1, 0.02:1, 0.025:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1.

[0015] Preferably, the concentration of ammonia water is 0.5-1.8 mol / L, more preferably 0.8-1.6 mol / L, still more preferably 1-1.4 mol / L, such as one of 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L. The feeding rate of ammonia water is 50-80 mL / h, preferably 55-75 mL / h, more preferably 60-70 mL / h, such as one of 50 mL / h, 52 mL / h, 54 mL / h, 56 mL / h, 58 mL / h, 60 mL / h, 62 mL / h, 65 mL / h, 68 mL / h, 70 mL / h, 73 mL / h, 75 mL / h, 78 mL / h, 80 mL / h.

[0016] Preferably, the oxidant is an oxygen-containing gas. Preferably, the oxygen content in the oxygen-containing gas is not less than 20%, and more preferably the oxygen-containing gas is air and / or oxygen. It should be noted that when air is selected as the oxidant, its flow rate should be 200-700% higher than the amount required by actual calculation, and when oxygen is selected as the oxidant, the flow rate should be 30-100% higher than the amount required by actual calculation.

[0017] Preferably, the dispersant is ethanol (preferably anhydrous ethanol).

[0018] Preferably, step 1) is specifically as follows:

[0019] 101) First, mix the dispersant with water as the reaction bottom liquid (the amount of the reaction bottom liquid only needs to meet the normal progress of the subsequent reaction and can be reasonably adjusted according to the actual working conditions), and then simultaneously input the manganese sulfate solution, ammonium ferric DTPA solution and ammonia water and introduce the oxidant, and then carry out the reaction at the first reaction temperature.

[0020] 102) Stop inputting the manganese sulfate solution and ammonium ferric DTPA solution, and raise the temperature of the reaction system to the second reaction temperature for reaction. After the reaction is completed, restore it to the first reaction temperature.

[0021] 103) Stop the input of ammonia water and continue the reaction until the target product is formed. After the reaction is completed, a crude product is obtained.

[0022] Preferably, in step 101), the mixing volume ratio of the dispersant to water is 1:2 - 9, preferably 1:3 - 7, more preferably 1:4 - 5, such as one of 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9.

[0023] Preferably, in step 101), the amount of ammonia water introduced is such that the pH of the reaction system is 6 - 8, preferably 6.5 - 7.5, more preferably 6.8 - 7.2, such as one of 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.

[0024] Preferably, in step 101), the first reaction temperature is not higher than 80°C, preferably 15 - 75°C, more preferably 30 - 70°C, such as one of 0°C, 50°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 78°C. The reaction time at the first reaction temperature is 1 - 24 h, preferably 2 - 18 h, more preferably 3 - 12 h.

[0025] Preferably, in step 102), the second reaction temperature is not lower than 80°C, preferably 80 - 150°C, more preferably 85 - 120°C, such as one of 80°C, 82°C, 85°C, 88°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C. The reaction time at the second reaction temperature is 0.3 - 3 h, preferably 0.5 - 2.5 h, more preferably 1 - 2 h.

[0026] Preferably, in step 103), the time for continuous reaction is 1 - 12 h, preferably 2 - 10 h, more preferably 3 - 8 h. The D50 of the target product is 1 - 20 μm, preferably 3 - 18 μm, more preferably 5 - 15 μm, such as one of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm.

[0027] Preferably, step 2) is specifically as follows: First, wash the crude product with deionized water 1 - 5 times (preferably 2 - 3 times), then filter (preferably by suction filtration) to obtain a filter cake, and finally dry the filter cake (preferably at a temperature of 100 - 120 °C for 12 - 24 h) to obtain the iron-doped manganese tetroxide material.

[0028] Preferably, in the present invention, the reaction process is carried out under stirring, and the stirring rate is 200 - 1000 r / min.

[0029] According to the second embodiment of the present invention, there is provided an iron-doped manganese tetroxide material:

[0030] An iron-doped manganese tetroxide material: The iron-doped manganese tetroxide material is a bulk iron-doped manganese tetroxide material prepared by using the preparation method described in the first embodiment.

[0031] Preferably, in the iron-doped manganese tetroxide material, the molar ratio of Fe element to Mn is 0.001 - 0.5:1, preferably 0.003 - 0.3:1, more preferably 0.005 - 0.15:1, such as 0.001:1, 0.002:1, 0.003:1, 0.004:1, 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, 0.01:1, 0.015:1, 0.02:1, 0.025:1, 0.03:1, 0.035:1, 0.04:1, 0.045:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1.

[0032] According to the third embodiment of the present invention, there is provided an application of an iron-doped manganese tetroxide material:

[0033] An application of an iron-doped manganese tetroxide material prepared by using the method described in the first embodiment, using the iron-doped manganese tetroxide material to prepare an iron-doped lithium manganese oxide cathode material.

[0034] Preferably, using the iron-doped manganese tetroxide material to prepare an iron-doped lithium manganese oxide cathode material is specifically as follows:

[0035] Mix the iron-doped manganese tetroxide material with lithium carbonate evenly to obtain a mixed material. Then, pre-calcine the mixed material at a temperature of 400 - 650 °C (preferably 450 - 600 °C) for 1 - 10 h (preferably 3 - 7 h), and then calcine it at a temperature of 700 - 950 °C (preferably 750 - 900 °C) for 3 - 36 h (preferably 5 - 24 h). Finally, after cooling, an iron-doped lithium manganese oxide cathode material is obtained.

[0036] Preferably, the addition amount of lithium carbonate is such that lithium is in excess by 1 - 10%, preferably 2 - 8%. It should be noted that the excess of lithium is calculated according to the molar ratio of Li:Mn elements, such as LiMn 2 O 4 with 5% excess lithium for lithium doping, then the molar ratio Li:Mn = 1.05:2.

[0037] In the prior art, the manganese tetroxide prepared by the existing one-step oxidation method of manganese sulfate has the problem of high sulfur content. Too high sulfur content will lead to a decrease in the capacity of lithium manganese oxide prepared by subsequent lithium mixing and sintering, an increase in electrochemical impedance, and an increase in the self-discharge rate of the battery, seriously affecting the electrochemical performance of lithium manganese oxide batteries. For the lithium manganese oxide cathode material prepared from manganese tetroxide, due to the presence of Mn 3+ on the one hand, it will cause the occurrence of the Jahn-Teller effect, resulting in the collapse of the spinel structure of lithium manganese oxide; on the other hand, under the erosion of the electrolyte, Mn 3+ undergoes a disproportionation reaction to generate Mn 2+ and Mn 4+ , among which Mn 2+ will dissolve in the electrolyte and adhere to the surface of the negative electrode, causing the loss of manganese. The above two points seriously affect the rate performance and cycle stability life of lithium manganese oxide, greatly increasing the impedance of the battery, which is an important obstacle to the further popularization of lithium manganese oxide.

[0038] In the present invention, in view of the above problems, doping the lithium manganese oxide cathode material with iron elements is a significantly effective modification method. Fe 3+ can replace a part of the existence of Mn 3+ and occupy the 16d site of the spinel, alleviating the Jahn-Teller effect; at the same time, the Fe-O bond is stronger than the Mn-O bond, improving the stability of the spinel structure and inhibiting the lattice deformation, thus significantly improving the cycle life and rate performance of lithium manganese oxide. However, the common Fe 3+Doping is carried out by the solid-phase method. This method can achieve better uniform doping for nanoscale cathode particles, but for larger-sized micron-scale particles, the uniformity of solid-phase doping will be affected. Therefore, in the present invention, manganese sulfate is used as the manganese source, ammonium iron(III) DTPA is used as the complexing agent and doping agent, and ammonia water is used as the alkaline solution to prepare manganese ferrite with a uniform particle size distribution. At the same time, the process is also improved: ethanol is introduced as a dispersant in the early stage of the reaction to inhibit the agglomeration of primary particles, providing a longer time window for the oxidation of basic manganese sulfate to manganese ferrite. After the reaction proceeds for a period of time, ethanol is evaporated (ethanol will inhibit the agglomeration between primary particles, resulting in poor product morphology. Evaporating it midway can make the primary particles agglomerate to form spherical secondary particles, which is beneficial to the improvement of the performance of the cathode material). This not only ensures the spontaneous agglomeration of primary particles and reduces the sulfur content in the preparation of manganese ferrite by one-step oxidation of manganese sulfate salt, but also ensures the formation of spherical secondary particles with good spherical shape from the secondary spontaneous agglomeration of primary particles and guarantees the tap density of the product. Through the optimization of this process, while reducing the sulfur content of the product, the sphericity and tap density of the product are ensured, thus ensuring the electrochemical performance of lithium manganate. The lithium manganate cathode material prepared using the iron-doped manganese ferrite material obtained in the present invention as the precursor has excellent cycle life and good rate performance.

[0039] In the present invention, ammonium iron(III) DTPA (CAS No. 85959-68-8) is used as the complexing agent and doping agent. While ensuring the formation of spherical particles of the product, relying on the strong complexing ability of DTPA, more uniform coprecipitation doping of iron elements is achieved compared with the conventional solid-phase doping method, and it has high sphericity, good particle size uniformity, and high tap density. That is to say, in the present invention, ammonium iron(III) DTPA has a dual role. One is to act as a complexing agent to unify the precipitation rate of elements and control the nucleation behavior during the precipitation process; the other is to act as a doping source for iron doping to provide ferric ions. Due to the combined action of its two functions, the uniformity of iron element doping in the bulk phase of manganese ferrite can be significantly improved.

[0040] In the present invention, the lithium manganate cathode material prepared by mixing and firing the iron-doped manganese ferrite material can significantly enhance the lattice strength of the material, effectively resist the distortion of the lattice caused by Jahn-Teller, and improve the structural stability of the material during the cycling process and at high rate conditions.

[0041] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0042] 1: In the process of preparing manganese tetraoxide from manganese sulfate, the present invention first uses ammonium iron DTPA as a complexing agent and doping agent. While maintaining the product in the form of pellets, it improves the uniformity of iron element doping in micron-sized manganese tetraoxide particles with large dimensions. Moreover, the product has good particle size uniformity and high tap density.

[0043] 2: The present invention optimizes the process of introducing ethanol as a dispersant in the early stage of the reaction and removing the dispersant after the reaction proceeds to a certain stage. On the one hand, it inhibits the agglomeration of primary particles in the early stage and reduces the entrainment of sulfur elements. At the same time, in the middle and late stages, it ensures the secondary spontaneous agglomeration of the product, further improving the sphericity of the product and ensuring the tap density of the material.

[0044] 3: The process flow of the present invention is simple, easy to operate, has low input cost and high economic benefits, and has the characteristics of large-scale promotion and application. In addition, the lithium manganese oxide cathode material prepared using the iron-doped manganese tetraoxide material obtained by the present invention as a precursor has excellent cycle life and good rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 EDS energy spectrum diagram of the iron-doped manganese tetraoxide material I prepared in Example 1 of the present invention.

[0046] Figure 2 Particle size distribution of the lithium manganese oxide cathode materials obtained in Example 1, Example 2, and Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0047] The technical solutions of the present invention will be illustrated by examples below. The scope of protection claimed by the present invention includes but is not limited to the following examples.

[0048] Example 1

[0049] (1) Mix deionized water and ethanol at a volume ratio of 4:1 to obtain a total of 1.7 L as the bottom liquid in the reaction kettle. Dissolve manganese sulfate in deionized water to prepare a 1.2 mol / L manganese sulfate solution, prepare a 0.1 mol / L ammonium iron DTPA solution, and prepare a 2 mol / L ammonia water solution;

[0050] (2) In an environment with an oxygen flow rate of 1 L / min, simultaneously introduce the manganese sulfate solution into the reaction kettle containing the bottom liquid at a rate of 50 mL / h, introduce the ammonium iron DTPA solution into the reaction kettle at a rate of 6 mL / h, introduce the ammonia water solution into the reaction kettle at a rate of 60 mL / h, heat up to 70 °C, and adjust the stirring speed to 500 r / min for the reaction;

[0051] (3) After step (2) reacts for 7 hours, stop introducing manganese sulfate solution and DTPA iron ammonium salt solution, raise the reaction temperature to 80°C, continue stirring the reaction for 1 hour, and then return to 70°C; then stop introducing ammonia solution, continue the reaction until the product D50 (particle size) grows to 10±1 μm, take out the slurry, wash, filter, and dry to obtain iron-doped manganese tetraoxide material I.

[0052] (4) The iron-doped manganese tetraoxide material I is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-sintered at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, the iron-doped lithium manganate positive electrode material I is obtained.

[0053] The obtained iron-doped lithium manganate positive electrode material I was tested using an energy dispersive X-ray spectrometer, and the results are as follows: Figure 1 As shown, it can be seen from the figure that the Mn and Fe elements in the obtained iron-doped lithium manganese oxide positive electrode material I are evenly distributed in the spherical particles.

[0054] Example 2

[0055] (1) Mix deionized water and ethanol in a volume ratio of 3:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, dissolve manganese sulfate in deionized water to prepare a 1.5 mol / L manganese sulfate solution, prepare a 0.5 mol / L DTPA iron ammonium salt solution, and prepare a 2.2 mol / L ammonia solution;

[0056] (2) In an environment where the oxygen flow rate is 1 L / min, the manganese sulfate solution is introduced into the reactor containing the base liquid at a rate of 50 mL / h, the DTPA iron ammonium salt solution is introduced into the reactor at a rate of 10 mL / h, and the ammonia solution is introduced into the reactor at a rate of 68 mL / h, the temperature is raised to 70° C., and the stirring speed is adjusted to 500 r / min for reaction;

[0057] (3) After step (2) reacts for 4 hours, stop introducing manganese sulfate solution and DTPA iron ammonium salt solution, raise the reaction temperature to 80°C, continue stirring the reaction for 1 hour, and then return to 70°C; then stop introducing ammonia solution, continue the reaction until the product D50 (particle size) grows to 7±1 μm, take out the slurry, wash, filter, and dry to obtain iron-doped manganese tetraoxide material II.

[0058] (4) The iron-doped manganese tetraoxide material II is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-sintered at 500° C. for 6 h, and then calcined at 800° C. for 12 h. After cooling, the iron-doped lithium manganate positive electrode material II is obtained.

[0059] Example 3

[0060] (1) deionized water and ethanol were mixed in a volume ratio of 7:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, manganese sulfate was dissolved in deionized water to prepare a 0.8 mol / L manganese sulfate solution, a 0.2 mol / L DTPA iron ammonium salt solution was prepared, and a 1.8 mol / L ammonia solution was prepared;

[0061] (2) In an environment where the oxygen flow rate is 1 L / min, the manganese sulfate solution is introduced into the reactor containing the base liquid at a rate of 60 mL / h, the DTPA iron ammonium salt solution is introduced into the reactor at a rate of 5 mL / h, and the ammonia solution is introduced into the reactor at a rate of 53 mL / h, the temperature is raised to 70° C., and the stirring speed is adjusted to 700 r / min for reaction;

[0062] (3) After step (2) reacts for 4 hours, stop introducing manganese sulfate solution and DTPA iron ammonium salt solution, raise the reaction temperature to 80°C, continue stirring the reaction for 1 hour, and then return to 70°C; then stop introducing ammonia solution, continue the reaction until the product D50 (particle size) grows to 11±1 μm, take out the slurry, wash, filter, and dry to obtain iron-doped manganese tetraoxide material III.

[0063] (4) The iron-doped manganese tetraoxide material II is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-fired at 500° C. for 6 h, and then calcined at 800° C. for 12 h. After cooling, the iron-doped lithium manganate positive electrode material III is obtained.

[0064] Example 4

[0065] (1) deionized water and ethanol were mixed in a volume ratio of 4:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, manganese sulfate was dissolved in deionized water to prepare a 1.2 mol / L manganese sulfate solution, a 0.2 mol / L DTPA iron ammonium salt solution was prepared, and a 2 mol / L ammonia solution was prepared;

[0066] (2) In an environment where the oxygen flow rate is 1 L / min, the manganese sulfate solution is introduced into the reactor containing the base liquid at a rate of 50 mL / h, the DTPA iron ammonium salt solution is introduced into the reactor at a rate of 10 mL / h, and the ammonia solution is introduced into the reactor at a rate of 60 mL / h, the temperature is raised to 70° C., and the stirring speed is adjusted to 500 r / min for reaction;

[0067] (3) After step (2) has reacted for 7 hours, the introduction of manganese sulfate solution and DTPA ammonium iron salt solution was stopped, the reaction temperature was raised to 80°C, and the reaction was continued with stirring for 1 hour before returning to 70°C; then the introduction of ammonia solution was stopped, and the reaction was continued until the product D50 (particle size) grew to 10±1 μm, and the slurry was taken out for washing, filtering, and drying to obtain iron-doped manganese tetraoxide material IV.

[0068] (4) The iron-doped manganese tetraoxide material IV is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-sintered at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, the iron-doped lithium manganate positive electrode material IV is obtained.

[0069] Example 5

[0070] (1) Mix deionized water and ethanol in a volume ratio of 4:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, dissolve manganese sulfate in deionized water to prepare a 1.2 mol / L manganese sulfate solution, prepare a 0.3 mol / L DTPA iron ammonium salt solution, and prepare a 2 mol / L ammonia solution;

[0071] (2) In an environment where the oxygen flow rate is 1 L / min, the manganese sulfate solution is introduced into the reactor containing the bottom liquid at a rate of 50 mL / h, the DTPA iron ammonium salt solution is introduced into the reactor at a rate of 12 mL / h, and the ammonia solution is introduced into the reactor at a rate of 60 mL / h, the temperature is raised to 70° C., and the stirring speed is adjusted to 500 r / min for reaction;

[0072] (3) After step (2) reacts for 7 hours, stop introducing manganese sulfate solution and DTPA iron ammonium salt solution, raise the reaction temperature to 80°C, continue stirring the reaction for 1 hour, and then return to 70°C; then stop introducing ammonia solution, continue the reaction until the product D50 (particle size) grows to 10±1 μm, take out the slurry, wash, filter, and dry to obtain iron-doped manganese tetraoxide material V.

[0073] (4) The iron-doped manganese tetraoxide material V is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-fired at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, the iron-doped lithium manganate positive electrode material V is obtained.

[0074] Example 6

[0075] (1) deionized water and ethanol were mixed in a volume ratio of 4:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, manganese sulfate was dissolved in deionized water to prepare a 1.2 mol / L manganese sulfate solution, a 0.1 mol / L DTPA iron ammonium salt solution was prepared, and a 2 mol / L ammonia solution was prepared;

[0076] (2) In an environment where the oxygen flow rate is 1 L / min, the manganese sulfate solution is introduced into the reactor containing the bottom liquid at a rate of 50 mL / h, the DTPA iron ammonium salt solution is introduced into the reactor at a rate of 4 mL / h, and the ammonia solution is introduced into the reactor at a rate of 60 mL / h, the temperature is raised to 70° C., and the stirring speed is adjusted to 500 r / min for reaction;

[0077] (3) After step (2) reacts for 7 hours, stop introducing manganese sulfate solution and DTPA iron ammonium salt solution, raise the reaction temperature to 80°C, continue stirring the reaction for 1 hour, and then return to 70°C; then stop introducing ammonia solution, continue the reaction until the product D50 (particle size) grows to 10±1 μm, take out the slurry, wash, filter, and dry to obtain iron-doped manganese tetraoxide material VI.

[0078] (4) The iron-doped manganese tetraoxide material VI is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-sintered at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, the iron-doped lithium manganate positive electrode material VI is obtained.

[0079] Example 7

[0080] (1) deionized water and ethanol were mixed in a volume ratio of 4:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, manganese sulfate was dissolved in deionized water to prepare a 1.2 mol / L manganese sulfate solution, a 0.1 mol / L DTPA iron ammonium salt solution was prepared, and a 2 mol / L ammonia solution was prepared;

[0081] (2) In an environment where the oxygen flow rate is 1 L / min, the manganese sulfate solution is introduced into the reactor containing the bottom liquid at a rate of 50 mL / h, the DTPA iron ammonium salt solution is introduced into the reactor at a rate of 3 mL / h, and the ammonia solution is introduced into the reactor at a rate of 60 mL / h, the temperature is raised to 70° C., and the stirring speed is adjusted to 500 r / min for reaction;

[0082] (3) After step (2) has reacted for 7 hours, the introduction of manganese sulfate solution and DTPA ammonium iron salt solution was stopped, the reaction temperature was raised to 80°C, and the reaction was continued with stirring for 1 hour before returning to 70°C; then the introduction of ammonia solution was stopped, and the reaction was continued until the product D50 (particle size) grew to 10±1 μm, and the slurry was taken out for washing, filtering, and drying to obtain iron-doped manganese tetraoxide material VII.

[0083] (4) The iron-doped manganese tetraoxide material VII is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-sintered at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, the iron-doped lithium manganate positive electrode material VII is obtained.

[0084] Comparative Example 1

[0085] (1) deionized water and ethanol were mixed in a volume ratio of 4:1 to prepare a total of 1.7 L of reaction kettle bottom liquid, manganese sulfate was dissolved in deionized water to prepare a 1.2 mol / L manganese sulfate solution, and a 2 mol / L ammonia solution was prepared;

[0086] (2) Under an oxygen flow rate of 1 L / min, the manganese sulfate solution was introduced into the reactor containing the bottom liquid at a rate of 50 mL / h, and the ammonia solution was introduced into the reactor at a rate of 60 mL / h, the temperature was raised to 70° C., and the stirring speed was adjusted to 500 r / min for reaction;

[0087] (3) After the reaction in step (2) for 7 hours, stop introducing the manganese sulfate solution, increase the reaction temperature to 80°C, continue stirring the reaction for 1 hour, and then return to 70°C; then stop introducing the ammonia solution, continue the reaction until the product D50 (particle size) grows to 10±1 μm, take out the slurry, wash, filter, and dry to obtain the manganese tetraoxide material.

[0088] (4) The obtained iron-doped manganese tetraoxide material I is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-sintered at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, a lithium manganate positive electrode material is obtained.

[0089] Comparative Example 2

[0090] (1) 1.7 L of deionized water was used as the bottom liquid of the reaction kettle, manganese sulfate was dissolved in deionized water to prepare a 1.2 mol / L manganese sulfate solution, 0.1 mol / L DTPA iron ammonium salt solution was prepared, and 2 mol / L ammonia solution was prepared;

[0091] (2) Under an oxygen flow rate of 1 L / min, a manganese sulfate solution is introduced into a reactor containing a base liquid at a rate of 50 mL / h, a DTPA iron ammonium salt solution is introduced into the reactor at a rate of 6 mL / h, and an ammonia solution is introduced into the reactor at a rate of 60 mL / h. The temperature is raised to 70° C., and the stirring speed is adjusted to 500 r / min to react until the product D50 (particle size) grows to 10±1 μm. The slurry is taken out, washed, filtered, and dried to obtain an iron-doped manganese tetraoxide material.

[0092] (3) The obtained iron-doped manganese tetraoxide material is fully mixed with lithium carbonate to obtain a mixture, in which the lithium content is 5%. The mixture is pre-fired at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, an iron-doped lithium manganate positive electrode material is obtained.

[0093] Comparative Example 3

[0094] (1) deionized water and ethanol were mixed in a volume ratio of 4:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, manganese sulfate was dissolved in deionized water to prepare a 1.2 mol / L manganese sulfate solution, a 0.1 mol / L DTPA iron ammonium salt solution was prepared, and a 2 mol / L ammonia solution was prepared;

[0095] (2) Under an oxygen flow rate of 1 L / min, a manganese sulfate solution is introduced into a reactor containing a base liquid at a rate of 50 mL / h, a DTPA iron ammonium salt solution is introduced into the reactor at a rate of 6 mL / h, and an ammonia solution is introduced into the reactor at a rate of 60 mL / h, the temperature is raised to 70°C, and the stirring speed is adjusted to 500 r / min for reaction; after 12 hours, the slurry is taken out, washed, filtered, and dried to obtain an iron-doped manganese tetraoxide material.

[0096] (4) The obtained iron-doped manganese tetraoxide material is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-fired at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, an iron-doped lithium manganate positive electrode material is obtained.

[0097] Comparative Example 4

[0098] (1) Mix deionized water and ethanol in a volume ratio of 4:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, dissolve manganese sulfate in deionized water to prepare a 1.2 mol / L manganese sulfate solution, prepare a 1 mol / L DTPA iron ammonium salt solution, and prepare a 2 mol / L ammonia solution;

[0099] (2) In an environment where the oxygen flow rate is 1 L / min, the manganese sulfate solution is introduced into the reactor containing the bottom liquid at a rate of 50 mL / h, the DTPA iron ammonium salt solution is introduced into the reactor at a rate of 35 mL / h, and the ammonia solution is introduced into the reactor at a rate of 60 mL / h, the temperature is raised to 70° C., and the stirring speed is adjusted to 500 r / min for reaction;

[0100] (3) After step (2) reacts for 7 hours, stop introducing manganese sulfate solution and DTPA iron ammonium salt solution, raise the reaction temperature to 80°C, continue stirring the reaction for 1 hour, and then return to 70°C; then stop introducing ammonia solution, continue the reaction until the product D50 (particle size) grows to 10±1 μm, take out the slurry, wash, filter, and dry to obtain iron-doped manganese tetraoxide material.

[0101] (4) The obtained iron-doped manganese tetraoxide material is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-fired at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, an iron-doped lithium manganate positive electrode material is obtained.

[0102] Comparative Example 5

[0103] (1) Mix deionized water and ethanol in a volume ratio of 4:1 to prepare a total of 1.7 L of the reaction kettle bottom liquid, dissolve manganese sulfate in deionized water to prepare a 1.2 mol / L manganese sulfate solution, prepare a 0.01 mol / L DTPA iron ammonium salt solution, and prepare a 2 mol / L ammonia solution;

[0104] (2) In an environment where the oxygen flow rate is 1 L / min, the manganese sulfate solution is introduced into the reactor containing the base liquid at a rate of 50 mL / h, the DTPA iron ammonium salt solution is introduced into the reactor at a rate of 1 mL / h, and the ammonia solution is introduced into the reactor at a rate of 60 mL / h, the temperature is raised to 70° C., and the stirring speed is adjusted to 500 r / min for reaction;

[0105] (3) After step (2) reacts for 7 hours, stop introducing manganese sulfate solution and DTPA iron ammonium salt solution, raise the reaction temperature to 80°C, continue stirring the reaction for 1 hour, and then return to 70°C; then stop introducing ammonia solution, continue the reaction until the product D50 (particle size) grows to 10±1 μm, take out the slurry, wash, filter, and dry to obtain iron-doped manganese tetraoxide material.

[0106] (4) The obtained iron-doped manganese tetraoxide material is fully mixed with lithium carbonate to obtain a mixture, wherein the lithium content is 5%. The mixture is pre-fired at 500° C. for 5 h, and then calcined at 800° C. for 10 h. After cooling, an iron-doped lithium manganate positive electrode material is obtained.

[0107] Effect comparison table:

[0108]

Claims

1. A preparation method of iron-doped manganese tetraoxide material, characterized in that: The preparation method comprises the following steps: 1) React a manganese sulfate solution, an ammonium iron(III) DTPA solution and ammonia water continuously in the presence of an oxidant and a dispersant, and obtain a crude product after the reaction is completed; 2) Wash, filter and dry the crude product in sequence to obtain the iron-doped manganese tetraoxide material.

2. The preparation method according to claim 1, characterized in that: The manganese sulfate solution is an aqueous solution of manganese sulfate salt, the concentration of the manganese sulfate salt is 0.5 - 2 mol / L, preferably 0.8 - 1.8 mol / L, more preferably 1 - 1.5 mol / L; the feeding rate of the manganese sulfate solution is 30 - 80 mL / h, preferably 40 - 70 mL / h, more preferably 45 - 65 mL / h; and / or The ammonium iron(III) DTPA solution is an aqueous solution of ammonium iron(III) DTPA, the concentration of the ammonium iron(III) DTPA is 0.03 - 0.3 times the concentration of the manganese sulfate salt, preferably 0.04 - 0.25 times, more preferably 0.05 - 0.2 times; the feeding rate of the ammonium iron(III) DTPA is 3 - 25 mL / h, preferably 5 - 20 mL / h, more preferably 8 - 15 mL / h; and / or The concentration of ammonia water is 0.5 - 1.8 mol / L, preferably 0.8 - 1.6 mol / L, more preferably 1 - 1.4 mol / L; the feeding rate of ammonia water is 50 - 80 mL / h, preferably 55 - 75 mL / h, more preferably 60 - 70 mL / h; Preferably, the molar ratio of the addition amount of ammonium iron(III) DTPA to the addition amount of manganese sulfate per unit time is 0.005 - 0.5:1, preferably 0.01 - 0.3:

1.

3. The preparation method according to claim 1 or 2, characterized in that: The oxidant is an oxygen-containing gas; preferably the oxygen content in the oxygen-containing gas is not less than 20%, more preferably the oxygen-containing gas is air and / or oxygen; and / or The dispersant is ethanol.

4. The preparation method according to any one of claims 1 - 3, characterized in that: Step 1) is specifically: 101) First mix the dispersant and water as the reaction bottom liquid, then input the manganese sulfate solution, the ammonium iron(III) DTPA solution and ammonia water simultaneously and introduce the oxidant, and then react at the first reaction temperature; 102) Stop the input of the manganese sulfate solution and the ammonium iron(III) DTPA solution, and raise the temperature of the reaction system to the second reaction temperature for reaction, and restore to the first reaction temperature after the reaction is completed; 103) Stop the input of ammonia water and continue the reaction until the target product is formed, and obtain the crude product after the reaction is completed.

5. The preparation method according to claim 4, characterized in that: In step 101), the mixing volume ratio of the dispersant to water is 1:2 - 9, preferably 1:3 - 7, more preferably 1:4 - 5; and / or In step 101), the feeding amount of ammonia water is such that the pH of the reaction system is 6 - 8, preferably 6.5 - 7.5, more preferably 6.8 - 7.2; and / or In step 101), the first reaction temperature is not higher than 80°C, preferably 15 - 75°C, more preferably 30 - 70°C; the reaction time at the first reaction temperature is 1 - 24 h, preferably 2 - 18 h, more preferably 3 - 12 h.

6. The preparation method according to claim 4 or 5, characterized in that: In step 102), the second reaction temperature is not lower than 80°C, preferably 80 - 150°C, more preferably 85 - 120°C; the reaction time at the second reaction temperature is 0.3 - 3 h, preferably 0.5 - 2.5 h, more preferably 1 - 2 h; and / or In step 103), the continuation reaction time is 1 - 12 h, preferably 2 - 10 h, more preferably 3 - 8 h; the D50 of the target product is 1 - 20 μm, preferably 3 - 18 μm, more preferably 5 - 15 μm.

7. The preparation method according to any one of claims 1 - 6, characterized in that: Step 2) is specifically: first wash the crude product with deionized water 1 - 5 times (preferably 2 - 3 times), then filter (preferably by suction filtration) to obtain a filter cake, and finally dry the filter cake (preferably dry at a temperature of 100 - 120°C for 12 - 24 h) to obtain the iron-doped manganese tetraoxide material.

8. An iron-doped manganese tetraoxide material prepared by the preparation method according to any one of claims 1 - 7, characterized in that: The iron-doped manganese tetraoxide material is a bulk-phase iron-doped manganese tetraoxide material; in the iron-doped manganese tetraoxide material, the molar ratio of Fe element to Mn is 0.001 - 0.5:1, preferably 0.003 - 0.3:1, more preferably 0.005 - 0.15:

1.

9. An application of an iron-doped manganese tetraoxide material prepared by the preparation method according to any one of claims 1 - 7, characterized in that: The iron-doped manganese tetraoxide material is used to prepare an iron-doped lithium manganese oxide cathode material.

10. The application according to claim 9, characterized in that: Using the iron-doped manganese tetraoxide material to prepare an iron-doped lithium manganese oxide cathode material specifically means: Mix the iron-doped manganese tetraoxide material and lithium carbonate evenly to obtain a mixture; then pre-calcine the mixture at a temperature of 400 - 650°C (preferably 450 - 600°C) for 1 - 10 h (preferably 3 - 7 h), and then calcine it at a temperature of 700 - 950°C (preferably 750 - 900°C) for 3 - 36 h (preferably 5 - 24 h); finally, obtain the iron-doped lithium manganese oxide cathode material after cooling; As a preference, the addition amount of lithium carbonate is such that lithium is in an excess of 1 - 10%, preferably 2 - 8%.

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