A manganese iron oxide material and a method of making the same

Abstract

The application discloses a manganese-iron oxide material and a preparation method thereof, and relates to the technical field of lithium ion battery precursor material preparation; the application comprises the following steps: preparing a mixed salt solution A containing manganese and iron elements; preparing a mixed alkali solution B containing alkali and soluble carbonate; gradually adding the mixed solution A into the mixed alkali solution B under stirring, controlling the dropping speed of the solution A and the pH value of the whole system to be between 9 and 12, continuing to stir for a period of time after the dropping is completed, and then obtaining a filter cake through nucleation crystallization, cooling, filtering and washing; adding a surfactant, drying, calcining at a certain temperature, and obtaining the manganese-iron oxide; the application is simple and easy to operate, can realize uniform mixing of the manganese and iron elements at an atomic level, and the prepared manganese-iron oxide has high chemical stability and will not cause atomic segregation and other phenomena under high-temperature treatment, so that the manganese-iron lithium phosphate positive electrode material with good uniformity, high purity and excellent performance can be further prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery precursor material preparation, in particular to a manganese-iron oxide material and a preparation method thereof. BACKGROUND

[0002] Lithium iron phosphate (LFP) has been widely used as a cathode material for lithium ion batteries due to its abundant raw material sources, low price, environmental friendliness, good thermal stability, excellent cycle performance, and safety. It plays an important role in high-power electric tools, energy storage devices, light electric vehicles, and portable mobile device power sources. However, with the rapid development of the new energy industry in recent years, the electrochemical energy storage industry has also experienced explosive growth. LFP cannot meet the current market demand for high-energy density batteries due to its low working voltage, insufficient rate performance, and low electronic conductivity. Lithium manganese iron phosphate (LFMP) is a material doped with a certain proportion of manganese in lithium iron phosphate. Manganese and iron are located adjacent to each other in the periodic table, have similar ion radii, and share some chemical properties. Therefore, the doping of manganese does not significantly change the structure of lithium iron phosphate. In addition, due to the high voltage characteristics of manganese, the energy density of LFMP is increased by 10-20% compared to LFP under the same specific capacity, and the low-temperature performance is also improved, making it a promising new generation of high-energy density power battery cathode material.

[0003] Currently reported methods for preparing LMFP include spray drying, sol-gel, co-precipitation, and high-temperature solid-phase methods. The solid-phase method is considered the most suitable for industrial large-scale production due to its simplicity, ease of process control, and high yield. However, this method often fails to achieve uniform mixing of manganese and iron sources at the atomic level, resulting in low nanoscale levels, non-uniform products, low purity, and large sizes. Therefore, there is an urgent need for a manganese-iron oxide material and a preparation method thereof to address this issue. SUMMARY

[0004] The present application aims to provide a manganese-iron oxide material and a preparation method thereof to address the problems mentioned in the background.

[0005] To achieve the above-mentioned objectives, the present application provides the following technical solutions: a preparation method of a manganese-iron oxide material, comprising the following specific steps:

[0006] S1. configuring a mixed salt solution A containing manganese and iron elements;

[0007] S2. configuring a mixed alkali solution B containing alkali and soluble carbonate;

[0008] S3. gradually add the mixed salt solution A into the mixed alkali solution B under stirring, control the dropping speed of the mixed salt solution A and the pH value of the whole system between 9-12, continue stirring for a period of time after the dropping is completed, then perform nucleation crystallization, cooling, filtration and washing to obtain a filter cake;

[0009] S4. after adding a surfactant into the filter cake, perform drying, then place in a muffle furnace, calcine at a certain temperature to obtain a manganese iron oxide.

[0010] Preferably, in the step S1, the total ion concentration of manganese and iron in the mixed salt solution A is 0.6-6 mol / L, and the molar ratio of manganese to iron is (2-4):1.

[0011] Preferably, in the step S1, the iron salt is one or more of ferric chloride, ferric nitrate and ferric sulfate, and the manganese salt is one or more of manganese chloride, manganese nitrate and manganese sulfate.

[0012] Preferably, in the step S2, the alkali is sodium hydroxide or potassium hydroxide, and the concentration is 0.5-3 mol / L.

[0013] Preferably, in the step S2, the soluble carbonate is one or more of sodium carbonate, ammonium carbonate, ammonium bicarbonate and potassium carbonate, and the concentration is 0.1-1 mol / L.

[0014] Preferably, in the step S3, the dropping speed of the mixed salt solution A into the mixed alkali solution B is 2-5 ml / min, and the stirring is continued for 2-10 h after the dropping is completed.

[0015] Preferably, in the step S3, the reaction mixture after the mixed salt solution A is mixed with the mixed alkali solution B is nucleated and crystallized at 60-90℃ for 6-24 h, then cooled, filtered and washed with deionized water until neutral.

[0016] Preferably, in the step S4, the surfactant is one or more of polyethylene glycol, sodium dodecyl sulfate and sodium oleate, and the addition amount is 0.1-1% of the total mass of the manganese salt and the iron salt in the mixed salt solution A.

[0017] Preferably, in the step S4, the drying temperature of the filter cake is 60-90℃, the drying time is 10-24 h, the calcination temperature of the dried material in the muffle furnace is 400-700℃, and the calcination time is 4-8 h.

[0018] Another technical solution provided by the application is a manganese iron oxide material prepared by the above preparation method, and the chemical formula is Mn 3-x Fe xO4, wherein 0.6≤x≤1, the molar ratio of manganese element and iron element is (2-4):1, the manganese element and the iron element are uniformly mixed, the chemical stability is high, and the atomic segregation phenomenon does not occur under the high-temperature condition of preparation of the battery positive electrode material.

[0019] Compared with the prior art, the manganese iron oxide material and the preparation method thereof have the following beneficial effects:

[0020] 1. The manganese iron oxide material and the preparation method thereof can realize uniform mixing of manganese element and iron element at an atomic level, the ratio of the two can be controlled from the raw material end, and the manganese iron oxide prepared at the same time has high chemical stability and will not have atomic segregation phenomenon under high-temperature treatment, which is beneficial to the subsequent production process to prepare a manganese iron lithium phosphate positive electrode material with good uniformity, high purity and excellent performance.

[0021] 2. The preparation method of the manganese iron oxide material has simple and reasonable steps, a mild process and easy operation, is suitable for industrialized production and application, and the manganese iron oxide precursor obtained has a small overall particle size, which can effectively reduce the mechanical grinding time in the preparation of manganese iron lithium phosphate by a solid phase method and is also beneficial to better control of the product size of the manganese iron lithium phosphate. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 SEM image of the manganese iron oxide prepared for Example 3.

[0023] Figure 2 XRD image of the manganese iron oxide prepared for Example 3;

[0024] Figure 3 SEM image of the manganese iron oxide prepared for Example 3 after re-high-temperature heat treatment;

[0025] Figure 4 Mn element distribution map of the manganese iron oxide prepared for Example 3 after re-high-temperature heat treatment;

[0026] Figure 5 Fe element distribution map of the manganese iron oxide prepared for Example 3 after re-high-temperature heat treatment. DETAILED DESCRIPTION

[0027] A preparation method of a manganese iron oxide material, comprising the following specific steps:

[0028] S1. configuring a mixed salt solution A containing manganese element and iron element;

[0029] S2. configuring a mixed alkali solution B containing alkali and soluble carbonate;

[0030] S3. The mixed salt solution A is gradually added dropwise into the mixed alkali solution B under stirring, the dropping speed of the mixed salt solution A and the pH value of the whole system are controlled between 9 and 12, after the dropping is completed, the stirring is continued for a period of time, then the nucleation crystallization, cooling, filtration and washing are carried out to obtain the filter cake;

[0031] S4. The filter cake is doped with a surfactant and then dried, and then placed in a muffle furnace to be calcined at a certain temperature to obtain the manganese iron oxide.

[0032] In step S1, the total ion concentration of manganese and iron in the mixed salt solution A is 0.6-6 mol / L, and the amount-of-substance ratio of manganese to iron is (2-4):1.

[0033] In step S1, the iron salt is one or more of ferric chloride, ferric nitrate and ferric sulfate, and the manganese salt is one or more of manganese chloride, manganese nitrate and manganese sulfate.

[0034] In step S2, the alkali is sodium hydroxide or potassium hydroxide, and the concentration is 0.5-3 mol / L.

[0035] In step S2, the soluble carbonate salt is one or more of sodium carbonate, ammonium carbonate, ammonium bicarbonate and potassium carbonate, and the concentration is 0.1-1 mol / L.

[0036] In step S3, the dropping speed of the mixed salt solution A into the mixed alkali solution B is 2-5 ml / min, and the stirring is continued for 2-10 h after the dropping is completed.

[0037] In step S3, the reaction mixture after the mixing of the mixed salt solution A and the mixed alkali solution B is nucleated and crystallized at 60-90℃ for 6-24 h, and then cooled and filtered, and washed with deionized water until neutral.

[0038] In step S4, the surfactant is one or more of polyethylene glycol, sodium dodecyl sulfate and sodium oleate, and the addition amount is 0.1-1% of the total mass of the manganese salt and the iron salt in the mixed salt solution A.

[0039] In step S4, the filter cake is dried at 60-90℃ for 10-24 h, and the dried material is calcined in a muffle furnace at 400-700℃ for 4-8 h.

[0040] A manganese iron oxide material prepared by the above preparation method, having a chemical formula of Mn 3-x Fe x O4, wherein 0.6≤x≤1, the amount-of-substance ratio of manganese to iron is (2-4):1, the manganese and iron elements are uniformly mixed, the chemical stability is high, and the atomic segregation phenomenon does not occur under the high temperature conditions of the preparation of the positive electrode material of the battery.

[0041] Example 1:

[0042] (1) Preparation of mixed salt solution A: FeCl3-6H2O and MnCl2-4H2O were dissolved in deionized water to obtain a solution A with a total manganese and iron concentration of 3 mol / L, wherein the molar ratio of manganese to iron was 2:1.

[0043] (2) Preparation of mixed base solution B: mixed base solution B containing 1.5 mol / L NaOH and 0.5 mol / L Na2CO3 was prepared, wherein the amount of substance of CO3 2- was 1.5 times that of Fe 3+ .

[0044] (3) Under stirring conditions, solution A was added to solution B at a rate of 2 ml / min, and after the addition was completed, stirring was continued for 3 h while maintaining a pH of 10, then crystallization was carried out at 70°C for 12 h, after which the mixture was cooled, filtered, and washed with deionized water until neutral.

[0045] (4) 0.8 g of polyethylene glycol was added to the washed filter cake, which was dried in an oven at 70°C for 10 h. The dried material was then calcined in a muffle furnace at 500°C for 4 h to obtain manganese-iron oxide.

[0046] Example 2:

[0047] (1) Preparation of mixed salt solution A: FeCl3-6H2O and MnCl2-4H2O were dissolved in deionized water to obtain a solution A with a total manganese and iron concentration of 3 mol / L, wherein the molar ratio of manganese to iron was 4:1.

[0048] (2) Preparation of mixed base solution B: mixed base solution B containing 3 mol / L NaOH and 1 mol / L Na2CO3 was prepared, wherein the amount of substance of CO3 2- was 1.5 times that of Fe 3+ .

[0049] (3) Under stirring conditions, solution A was added to solution B at a rate of 2 ml / min, and after the addition was completed, stirring was continued for 3 h while maintaining a pH of 12, then crystallization was carried out at 70°C for 12 h, after which the mixture was cooled, filtered, and washed with deionized water until neutral.

[0050] (4) 0.8 g of sodium dodecyl sulfate was added to the washed filter cake, which was dried in an oven at 80°C for 6 h. The dried material was then calcined in a muffle furnace at 600°C for 6 h to obtain manganese-iron oxide.

[0051] Example 3:

[0052] (1) Preparation of mixed salt solution A: Fe2(S04)3.9H20 and MnS04.H20 were dissolved in deionized water to obtain a solution A with the total concentration of manganese and iron being 2 mol / L, wherein the molar ratio of manganese to iron was 2:1.

[0053] (2) Preparation of mixed base solution B: mixed base solution B containing 1 mol / L NaOH and 0.5 mol / L Na2C03 was prepared, wherein the molar amount of C03 2- was 1.5 times that of Fe 3+ .

[0054] (3) Under stirring, solution A was added into solution B at a rate of 4 ml / min, and after the addition was completed, the stirring was continued for 5 h while maintaining the pH at 10, and then crystallization was carried out at 80°C for 12 h, after which the product was cooled, filtered, and washed with deionized water until neutral.

[0055] (4) 0.8 g of sodium dodecyl sulfate was added to the washed filter cake, which was dried in an oven at 60°C for 10 h. The dried material was calcined in a muffle furnace at 400°C for 5 h to obtain manganese-iron oxide.

[0056] Example 4:

[0057] (1) Preparation of mixed salt solution A: Fe2(S04)3.9H20 and MnS04.H20 were dissolved in deionized water to obtain a solution A with the total concentration of manganese and iron being 2 mol / L, wherein the molar ratio of manganese to iron was 3:1.

[0058] (2) Preparation of mixed base solution B: mixed base solution B containing 2 mol / L NaOH and 0.5 mol / L Na2C03 was prepared, wherein the molar amount of C03 2- was 1.5 times that of Fe 3+ .

[0059] (3) Under stirring, solution A was added into solution B at a rate of 4 ml / min, and after the addition was completed, the stirring was continued for 3 h while maintaining the pH at 11, and then crystallization was carried out at 90°C for 12 h, after which the product was cooled, filtered, and washed with deionized water until neutral.

[0060] (4) 0.6 g of sodium oleate was added to the washed filter cake, which was dried in an oven at 70°C for 10 h. The dried material was calcined in a muffle furnace at 700°C for 4 h to obtain manganese-iron oxide.

[0061] Example 5:

[0062] (1) Configuration of mixed salt solution A: Fe(NO3)3.9H2O and Mn(NO3)2.4H2O are dissolved with deionized water to obtain a solution A with a total manganese iron concentration of 3 mol / L, wherein the amount of substance ratio of manganese element to iron element is 2:1.

[0063] (2) Configuration of mixed alkali solution B: mixed alkali solution B containing 3 mol / L NaOH and 1 mol / L Na2CO3 is configured, wherein the amount of substance of CO3 2- is 1.5 times of Fe 3+ .

[0064] (3) Under stirring conditions, solution A is added to solution B at a rate of 3 ml / min, after the addition is completed, continue stirring for 3h, keep the pH at 12, then crystallize at 70℃ for 12h, then cool, filter, wash with deionized water until neutral.

[0065] (4) 1.6g of polyethylene glycol is added to the filter cake after washing, dried in an oven at 80℃ for 10h. The dried material is calcined in a muffle furnace at 600℃ for 6h to obtain manganese iron oxide.

[0066] Example 6:

[0067] The manganese iron oxides prepared in the above examples 1 to 5 are respectively placed in a muffle furnace, under a nitrogen atmosphere, heated to 400℃ at a heating rate of 3℃ / min, kept for 2h, then heated to 750℃ at a heating rate of 1℃ / min and kept for 6h, after cooling to room temperature, no atomic segregation phenomenon is detected;

[0068] Taking example 3 as an example, Figure 1 it shows that its size is small and uniform, from Figures 3 to 5 it can be seen that after re-heating, its morphology and size do not change significantly, the distribution of manganese and iron elements remains uniform, which shows that it has high stability, when it is used as a precursor to process and prepare a battery positive electrode material, it is beneficial to obtain a product with good uniformity, high purity and excellent performance.

[0069] The above is only a preferred embodiment of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements that can be easily thought of by those skilled in the art within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be limited by the protection scope defined by the claims.

[0070] The parts not described in the present application are well-known technologies to those skilled in the art.

Claims

1. A method for preparing a manganese iron oxide material, characterized in that, The specific steps include the following: S1. Prepare a mixed salt solution A containing manganese and iron. The iron salt is one or more of ferric chloride, ferric nitrate, and ferric sulfate, and the manganese salt is one or more of manganese chloride, manganese nitrate, and manganese sulfate. The total ion concentration of manganese and iron in the mixed salt solution A is 0.6 to 6 mol / L, and the molar ratio of manganese to iron is (2 to 4):

1. S2. Prepare a mixed alkaline solution B containing an alkali and a soluble carbonate; the alkali is sodium hydroxide or potassium hydroxide, with a concentration of 0.5–3 mol / L; the soluble carbonate is one or more of sodium carbonate, ammonium carbonate, ammonium bicarbonate, and potassium carbonate, with a concentration of 0.1–1 mol / L; S3. Under stirring, gradually add mixed salt solution A to mixed alkali solution B at a rate of 2-5 ml / min. Control the adding rate of mixed salt solution A and the pH of the entire system between 9 and 12. After the addition is complete, continue stirring for 2-10 h. The reactants after mixing mixed salt solution A with mixed alkali solution B are nucleated and crystallized at 60-90℃ for 6-24 h. Then cool, filter, and wash with deionized water until neutral to obtain filter cake. S4. After adding a surfactant to the filter cake, it is dried. The surfactant is one or more of polyethylene glycol, sodium dodecyl sulfate, and sodium oleate. The amount added is 0.1-1% of the total mass of manganese and iron salts added to the mixed salt solution A. The filter cake is dried at 60-90℃ for 10-24 h. Then it is placed in a muffle furnace and calcined at 400-700℃ for 4-8 h to obtain manganese iron oxide with the chemical formula Mn. 3-x Fe x O4, 0.6≤x≤1, is a homogeneous mixture of manganese and iron elements with high chemical stability. It does not exhibit atomic segregation under the high-temperature conditions required for preparing battery cathode materials.

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