Ferromanganese oxide and preparation method and application thereof

Abstract

The invention discloses a ferromanganese oxide and a preparation method and application thereof.The chemical formula of the ferromanganese oxide is (Mn2O3) x. (Fe2O3) 1-x, x is larger than 0 and smaller than 1, the ferromanganese oxide is of a single crystal type, the particle size is 0.5-2 microns, and during preparation, a mixed solution composed of soluble ferric salt and soluble manganese salt, alkali liquor and an aqueous solution with the pH being 9.5 + / -0.5 are firstly prepared to serve as base solutions; the preparation method comprises the following steps: preparing a mixed solution, respectively adding the mixed solution and alkali liquor into a base solution, reacting to obtain compound slurry, carrying out solid-liquid separation, washing and drying to obtain a compound sample, and finally sintering in an air atmosphere to obtain the ferromanganese oxide. The ferromanganese oxide prepared by the invention is used for later lithium doping synthesis of lithium manganese iron phosphate, and can be sintered to form larger single crystal particles, and the prepared lithium manganese iron phosphate material has strong performance stability and high tap density.

Description

Technical Field

[0001] The present invention belongs to the technical field of manganese-based new energy materials, and in particular relates to a manganese iron oxide and a preparation method and application thereof. Background Art

[0002] With the continuous development of lithium iron manganese phosphate, new manganese-based new energy materials have been developed. At present, the main precursors of lithium iron manganese phosphate are iron manganese phosphate, manganese phosphate, iron phosphate, manganese iron oxide, etc. In the prior art, manganese iron oxide is usually prepared by mixing manganese source and iron source and then calcining. The main microscopic morphology is amorphous and single crystal particles cannot be formed. For the further synthesis of lithium iron manganese phosphate materials in the later stage, there are problems such as low performance stability and low tap density. Summary of the invention

[0003] In order to overcome the problems in the prior art, the present invention provides a manganese iron oxide and a preparation method and application thereof. The prepared manganese iron oxide with a single crystal structure has a particle size of 0.5-2 μm. The manganese iron oxide prepared by the present invention is used for the later lithium doping synthesis of lithium manganese iron phosphate, which can be sintered to form single crystal particles with larger particles. The prepared lithium manganese iron phosphate material has strong performance stability and high tap density.

[0004] In order to solve the above technical problems, the technical solution proposed by the present invention is: The present invention provides a manganese iron oxide, the chemical formula of the manganese iron oxide is (Mn2O3) x ·(Fe2O3) 1-x , wherein 0<x<1, the manganese iron oxide is single crystal and has a particle size of 0.5-2 μm.

[0005] Based on the same technical concept, the present invention also provides a method for preparing the above-mentioned ferromanganese oxide, comprising the following steps: S1. preparing a mixed solution of soluble iron salt and soluble manganese salt and an aqueous solution with a pH of 9.5±0.5 as a base solution; S2, adding the mixed solution prepared in step 1 and the alkali solution to the base solution prepared in step S1 respectively under stirring, controlling the pH value to 9.5±0.5 during the reaction, and obtaining a composite slurry after the reaction; S3, separating the composite slurry obtained in step S2 into solid and liquid, washing, and drying to obtain a composite sample; S4. Sintering the composite sample obtained in step S3 in an air atmosphere to obtain ferromanganese oxide.

[0006] In the present invention, the bottom liquid is first configured to meet the stirring requirements of the reactor, and then the mixed solution composed of manganese salt and iron salt and the alkali solution are added to the bottom liquid respectively, and the reaction is carried out under the condition of pH 9.5±0.5 to ensure that the reaction is orderly and controllable. If the alkali solution is added to the mixed solution or the mixed solution is added to the alkali solution, the preset reaction condition pH 10±0.5 cannot be obtained. Due to the different hydrolysis pHs of manganese and iron, Fe begins to hydrolyze at a solution pH of 3.0, and Mn begins to hydrolyze at a pH of 9 or above. When the pH is 9.5±0.5, the purpose of coprecipitation can be achieved, and then the composite sample is sintered in an air atmosphere to oxidize the composite sample.

[0007] As an optional embodiment, in the preparation method provided by the present invention, in step S1, the molar ratio of manganese element to iron element in the soluble manganese salt and the soluble iron salt is .9:1-3:7.

[0008] Controlling the molar ratio of manganese to iron in the soluble manganese salt and the soluble iron salt within the above range is beneficial to the preparation of an iron-manganese phosphate battery with optimal performance.

[0009] As an optional embodiment, in the preparation method provided by the present invention, in step S1, the molar ratio of the sum of the molar amounts of manganese element and iron element in the mixed solution to the alkali solution is 1:2.0-1:2.3.

[0010] Controlling the molar ratio of the sum of the molar amounts of manganese and iron in the solution to the alkali solution within the above range is conducive to the reaction under optimal conditions. If it exceeds the high range, there may be excess reactants or impurities may be generated.

[0011] As an optional embodiment, in the preparation method provided by the present invention, in step S2, the reaction time is to continue stirring the reaction for 0.5-1 h after the feeding is completed.

[0012] As an optional embodiment, in the preparation method provided by the present invention, the composite sample obtained in step S3 is an iron-manganese composite, and its chemical formula is [MnO(OH)] 2x ·[FeO(OH)] 2(1-x) , the composite sample is hexagonal lepidocrocite.

[0013] In the present invention, the reaction equation for preparing the iron-manganese complex using manganese salt and iron salt in alkali solution is as follows: 2xMn 2+ +2(1-x)Fe 2+ +OH - +O2→[MnO(OH)] 2x ·[FeO(OH)] 2(1-x) As an optional embodiment, in the preparation method provided by the present invention, the composite sample is a nano-scale particle, and the particle size of the composite sample is 100-500 nm.

[0014] The nanometer-level iron-manganese composite is prepared in the present invention, which provides a basis for preparing submicron-level manganese-iron composite oxides. After sintering, the nanometer particles further react to form a single-crystalline oxide.

[0015] As an optional embodiment, in the preparation method provided by the present invention, in step S4, the sintering temperature is 600-800° C., and the sintering time is 2-10 h.

[0016] The sintering temperature is controlled at 600-800°C. If the temperature is too high, the sample will be over-burned and lose its activity, which is not conducive to further sintering. If the temperature is too low, single crystal compounds cannot be formed.

[0017] The chemical equation for obtaining iron-manganese oxide by sintering iron-manganese composite is as follows: [MnO(OH)] 2x ·[FeO(OH)] 2(1-x) →(Mn2O3) x ·(Fe2O3) 1-x +H2O As an optional embodiment, in the preparation method provided by the present invention, the soluble iron salt is selected from one or both of ferrous sulfate and ferrous chloride.

[0018] As an optional embodiment, in the preparation method provided by the present invention, the soluble manganese salt is selected from one or more of manganese sulfate, manganese chloride, and manganese acetate.

[0019] As an optional embodiment, in the preparation method provided by the present invention, the alkali solution is selected from one or more of NaOH, NH3·H2O, and KOH.

[0020] Based on the same technical concept, the present invention also provides the use of the above-mentioned ferromanganese oxide or the ferromanganese oxide obtained by the above-mentioned preparation method in the preparation of lithium iron phosphate batteries.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) Compared with the existing technology, this technology produces manganese iron oxide in the form of uniform single crystal particles, which is more controllable for the subsequent preparation of lithium manganese iron phosphate, thereby obtaining a higher quality lithium manganese iron phosphate product.

[0022] (2) Using this process, the mixed solution of manganese salt and iron salt is first oxidized to prepare an intermediate with a structure of hexagonal lepidocrocite, and then sintered to prepare manganese iron oxide. From the XRD phase analysis, the sample has good crystallinity and atomic-level mixing is achieved. Iron replaces part of the manganese in the manganese trioxide lattice. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 is a process flow chart of the present invention; Figure 2 The XRD detection spectrum of ferromanganese hydroxide prepared in Example 1 of the present invention; Figure 3 This is a SEM image of ferromanganese hydroxide prepared in Example 1 of the present invention; Figure 4 The XRD detection spectrum of the manganese iron oxide prepared in Example 1 of the present invention; Figure 5 This is a SEM image of the manganese iron oxide prepared in Example 1 of the present invention; Figure 6 The XRD detection spectrum of the manganese iron oxide prepared in Comparative Example 1; Figure 7 This is a SEM image of the manganese iron oxide prepared in Comparative Example 1; Figure 8 This is the XRD detection spectrum of the manganese iron oxide prepared in Comparative Example 2. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0026] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional 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.

[0027] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0028] Example 1 1. Solution preparation: (1) Dissolve 77 g of manganese sulfate monohydrate and 126 g of ferrous sulfate heptahydrate in 1 L of pure water to obtain a mixed solution; (2) Dissolve sodium hydroxide in 0.2 L of pure water and adjust the pH to 10.2 to prepare a base solution; (3) Prepare a 20% solution by taking 73 g of sodium hydroxide at a (Mn+Fe):OH molar ratio of 1:2.

[0029] 2. Preparation of ferromanganese oxide, process flow Figure 1 As shown: (1) Under stirring conditions, a peristaltic pump is used to add a mixed solution and a sodium hydroxide solution to the bottom liquid. During the process, the pH of the reaction liquid is controlled to be 9-10. After the addition of the materials is completed, the stirring reaction is continued for 1 hour to obtain a slurry. After the reaction end point, solid-liquid separation is performed, and the precipitate is washed with pure water and vacuum dried to obtain an iron-manganese complex. Figure 2 It can be seen from XRD analysis that the main phase is hexagonal lepidocrocite, and there is no other manganese phase, indicating that the sample is a single lattice, with Mn 30.36% and Fe 30.10%, and the calculated chemical formula is [MnO(OH)] 0.5 ·[FeO(OH)] 0.5 The iron-manganese complex was subjected to SEM examination, and the results were as follows Figure 3 As shown, from Figure 3 It can be seen that the manganese-iron composite particles are nanoscale, with a particle size between 100-500 nm, and some are in agglomerated state.

[0030] (2) The above-mentioned manganese iron composite was placed in a muffle furnace and sintered at 800°C for 2 hours to obtain manganese iron oxide. The XRD test results were as follows: Figure 4 As shown in Figure 1, according to the XRD analysis results, the sample phase is a single phase of manganese trioxide, indicating that manganese and iron have achieved atomic-level mixing. The iron-manganese oxide was tested by SEM, and the results are as follows Figure 5 As shown in the figure, according to the SEM analysis results, the formed particles are single crystals with a particle size of 0.5-2 μm, of which Mn is 34.59% and Fe is 35.41%. According to the calculation, the target product is (Mn2O3) 0.5 ·(Fe2O3) 0.5 .

[0031] Example 2 1. Solution preparation: (1) Dissolve 120 g of manganese chloride tetrahydrate and 81 g of ferrous chloride tetrahydrate in 1 L of pure water to obtain a mixed solution; (2) Dissolve sodium hydroxide in 0.2 L of pure water and adjust the pH to 10.3 to prepare a base solution; (3) Prepare a 20% solution by taking 89 g of sodium hydroxide at a (Mn+Fe):OH molar ratio of 1:1.

[0032] 2. Preparation of ferromanganese oxide, process flow Figure 1 As shown: (1) Under stirring conditions, a peristaltic pump was used to add the mixed solution and sodium hydroxide solution to the bottom liquid. During the process, the pH of the reaction liquid was controlled at 9-10. After the addition of materials, the stirring reaction was continued for 0.5 h to obtain a slurry. After the end of the reaction, solid-liquid separation was performed, and the precipitate was washed with pure water and vacuum dried to obtain an iron-manganese complex. XRD analysis showed that the main phase was hexagonal lepidocrocite, and there was no other manganese phase, indicating that the sample was a single lattice, with Mn 36.31% and Fe 24.86%. The calculated chemical formula was [MnO(OH)] 0.60 ·[FeO(OH)] 0.40 ..

[0033] (2) The above-mentioned manganese-iron composite was placed in a muffle furnace and sintered at 900°C for 6 hours to obtain manganese-iron oxide. After XRD detection, according to the XRD analysis results, the sample phase was a single phase of manganese trioxide, indicating that manganese and iron were mixed at the atomic level. The iron-manganese oxide was subjected to SEM detection. According to the SEM analysis results, the formed particles were single crystals with a particle size of 0.5-2 μm, of which Mn was 40.85% and Fe was 27.77%. According to the calculation, the target product was (Mn2O3) 0.60 ·(Fe2O3) 0.40 .

[0034] Example 3 1. Solution preparation: (1) Dissolve 170 g of manganese acetate tetrahydrate and 85 g of ferrous sulfate heptahydrate in 1 L of pure water to obtain a mixed solution; (2) Dissolve sodium hydroxide in 0.2 L of pure water and adjust the pH to 10.3 to prepare a base solution; (3) 340 mL of 20% ammonia solution with a (Mn+Fe):OH molar ratio of 1:1.

[0035] 2. Preparation of ferromanganese oxide, process flow Figure 1 As shown: (1) Under stirring conditions, a peristaltic pump was used to add the mixed solution and ammonia solution to the bottom liquid. During the process, the pH of the reaction liquid was controlled at 9-10. After the addition of materials, the stirring reaction was continued for 0.5 h to obtain a slurry. After the end of the reaction, solid-liquid separation was performed, and the precipitate was washed with pure water and dried to obtain an iron-manganese complex. XRD analysis showed that the main phase was hexagonal lepidocrocite, and there was no other manganese phase, indicating that the sample was a single lattice, with Mn 43.62% and Fe 19.02%. The calculated chemical formula was [MnO(OH)] 0.70 ·[FeO(OH)] 0.30 ..

[0036] (2) The above-mentioned manganese-iron composite was placed in a muffle furnace and sintered at 650°C for 6 hours to obtain manganese-iron oxide. After XRD detection, according to the XRD analysis results, the sample phase was a single phase of manganese trioxide, indicating that manganese and iron were mixed at the atomic level. The iron-manganese oxide was subjected to SEM detection. According to the SEM analysis results, the particles formed were single crystals with a particle size of 0.5-2 μm, of which Mn was 48.68% and Fe was 21.03%. According to the calculation, the target product is (Mn2O3) 0.70 ·(Fe2O3) 0.30 .

[0037] Comparative Example 1 32g of ferrous sulfate heptahydrate and 16g of manganese sulfate monohydrate were mixed in a solid phase, and then directly placed in a muffle furnace and sintered at 600°C in an air atmosphere for 4 hours to obtain a manganese-iron oxide mixture. The XRD results are as follows: Figure 6 As shown in the analysis results, the sintered material is a mixture of ferroferric oxide and manganese trioxide, and no single phase is formed. The SEM analysis results are as follows Figure 7 As shown, from Figure 7 It can be concluded that the material is amorphous and no single crystal is formed.

[0038] Comparative Example 2 1. Solution preparation: (1) Dissolve 77 g of manganese sulfate monohydrate and 126 g of ferrous sulfate heptahydrate in 1 L of pure water to obtain a mixed solution; (2) Prepare a 20% solution by taking 73 g of sodium hydroxide at a (Mn+Fe):OH molar ratio of 1:2.

[0039] 2. Preparation of ferromanganese oxide: (1) Under stirring conditions, a peristaltic pump is used to add a sodium hydroxide solution to the mixed solution. After the addition of the materials is completed, the stirring reaction is continued for 1 hour to obtain a slurry. After the reaction end point, solid-liquid separation is performed, and the precipitate is washed with pure water and dried to obtain an iron-manganese complex.

[0040] (2) The above-mentioned ferromanganese composite was placed in a muffle furnace and sintered at 800°C for 2h to obtain ferromanganese oxide, wherein Mn is 32.69% and Fe is 36.32%. The XRD results are as follows: Figure 8 As shown in the figure, it can be seen that due to the adjustment of the feeding method, no base liquid was used, and sodium hydroxide was directly introduced into the mixed solution, so that only part of the co-precipitation points were formed during the reaction process, and two phases appeared in the final product. From the chemical analysis composition, it can be seen that the Fe content in the product is relatively high. This is because the reaction pH cannot be stably controlled during the reaction process, resulting in Fe preferential precipitation, and the iron-manganese ratio in the product is inconsistent with the feeding ratio.

[0041] Comparative Example 3 1. Solution preparation: (1) Dissolve 77 g of manganese sulfate monohydrate and 126 g of ferrous sulfate heptahydrate in 1 L of pure water to obtain a mixed solution; (2) Dissolve sodium hydroxide in 0.2 L of pure water and adjust the pH to 8.5 to prepare a base solution; (3) Prepare a 20% solution by taking 73 g of sodium hydroxide at a (Mn+Fe):OH molar ratio of 1:2.

[0042] 2. Preparation of ferromanganese oxide, process flow Figure 1 As shown: (1) Under stirring conditions, a peristaltic pump is used to add the mixed solution and sodium hydroxide solution to the base liquid. During the process, the pH of the reaction liquid is controlled to be 8.5. After the addition of the materials is completed, the stirring reaction is continued for 1 hour to obtain a slurry. After the reaction endpoint, solid-liquid separation is performed, and the precipitate is washed with pure water and dried to obtain an iron-manganese complex.

[0043] (2) The above-mentioned ferromanganese composite was placed in a muffle furnace and sintered at 800°C for 2 hours to obtain ferromanganese oxide. The Mn content of the sample was tested to be 16.85%, and the Fe content was 53.46%. From the composition analysis, although the amount ratio of the ferromanganese input in the front end was consistent, the final samples were quite different, indicating that the reaction pH was too low, no co-precipitation was formed in the early stage, the iron precipitate was relatively large, and the manganese precipitate was relatively small.

[0044] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A manganese iron oxide, characterized in that: The chemical formula of the manganese iron oxide is (Mn2O3) x ·(Fe2O3) 1-x , wherein 0<x<1, the manganese iron oxide is single crystal and has a particle size of 0.5-2 μm.

2. The method for preparing ferromanganese oxide according to claim 1, characterized in that: The following steps are involved: S1. preparing a mixed solution of soluble iron salt and soluble manganese salt and an aqueous solution with a pH of 9.5±0.5 as a base solution; S2, adding the mixed solution prepared in step 1 and the alkali solution to the base solution prepared in step S1 respectively under stirring, controlling the pH value to 9.5±0.5 during the reaction, and obtaining a composite slurry after the reaction; S3, separating the composite slurry obtained in step S2 into solid and liquid, washing, and drying to obtain a composite sample; S4. Sintering the composite sample obtained in step S3 in an air atmosphere to obtain ferromanganese oxide.

3. The method for preparing ferromanganese oxide according to claim 2, characterized in that: In step S1, the molar ratio of manganese element to iron element in the soluble manganese salt and the soluble iron salt is .9:1-3:

7.

4. The method for preparing ferromanganese oxide according to claim 2, characterized in that: In step S1, the molar ratio of the sum of the molar amounts of manganese and iron in the mixed solution to the alkali solution is 1:2.0-1:2.

3.

5. The method for preparing ferromanganese oxide according to claim 2, characterized in that: In step S2, the reaction time is 0.5-1 h after the feeding is completed and the stirring reaction is continued.

6. The method for preparing ferromanganese oxide according to claim 2, characterized in that: The composite sample obtained in step S3 is an iron-manganese composite, and its chemical formula is [MnO(OH)] 2x ·[FeO(OH)] 2(1-x) , the composite sample is hexagonal lepidocrocite.

7. The method for preparing ferromanganese oxide according to claim 6, characterized in that: The composite sample is a nano-scale particle, and the particle size of the composite sample is 100-500 nm.

8. The method for preparing ferromanganese oxide according to claim 2, characterized in that: In step S4, the sintering temperature is 600-800° C., and the sintering time is 2-10 h.

9. The method for preparing ferromanganese oxide according to claim 2, characterized in that: The soluble iron salt is selected from one or both of ferrous sulfate and ferrous chloride; the soluble manganese salt is selected from one or more of manganese sulfate, manganese chloride and manganese acetate; the alkali solution is selected from one or more of NaOH, NH3·H2O and KOH.

10. Use of the manganese iron oxide according to claim 1 or the manganese iron oxide obtained by the preparation method according to claims 2 to 9 in preparing lithium iron phosphate batteries.

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