Ferromanganese oxide precursor as well as preparation method and application thereof

Abstract

The invention relates to a ferromanganese oxide precursor as well as a preparation method and application thereof, and belongs to the technical field of lithium ion battery materials. The technical problems that in the prior art, the process for preparing the lithium manganese iron phosphate through a solid phase method is simple, but the synthesized material is poor in performance, and the material for preparing the lithium manganese iron phosphate through a liquid phase method is good in performance, high in cost and large in environmental protection pressure are solved. The preparation method of the ferromanganese oxide precursor comprises the following steps: mixing an iron source, a manganese source, SiO2 and a basic oxide solid phase, and sintering in an air or oxygen atmosphere to obtain the ferromanganese oxide precursor; in the sintering process of the ferromanganese oxide precursor, a manganese source, an iron source and SiO2 form eutectic, and meanwhile, the basic oxide is used as a fluxing agent to reduce the sintering temperature, so that elements of the finally synthesized ferromanganese oxide precursor are uniformly distributed. The lithium manganese iron phosphate composite material synthesized by the manganese iron oxide precursor is excellent in performance, low in cost, high in compaction density and high in gram volume.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery materials, and specifically relates to a manganese iron oxide precursor and a preparation method and application thereof, and in particular relates to the application of the manganese iron oxide precursor in the preparation of a manganese iron phosphate lithium composite material. Background Art

[0002] With the application of lithium-ion batteries, commercial products have higher and higher requirements for the cost performance of lithium-ion batteries, which is mainly reflected in the increasingly fierce competition among battery manufacturers for the cost per watt-hour of batteries. In recent years, the market share of lithium iron phosphate positive electrode materials has surpassed that of ternary positive electrode materials, on the one hand because lithium iron phosphate is safer, and on the other hand because lithium iron phosphate is cheaper.

[0003] With the development of material technology, lithium manganese iron phosphate has received more and more attention from the industry. Compared with lithium iron phosphate, lithium manganese iron phosphate has the same gram capacity, but the voltage of lithium manganese iron phosphate is higher than that of lithium iron phosphate, so the theoretical cost of lithium manganese iron phosphate battery is lower than that of lithium iron phosphate, so the research on lithium manganese iron phosphate by materials, batteries and vehicle manufacturers is gradually deepening.

[0004] For LiMn x Fe 1-x PO4, whether it is lithium iron phosphate when x=0 or lithium manganese iron phosphate when x≠0, material synthesis can be divided into solid phase method and liquid phase method. The solid phase method has a simple process but the synthesized material has the worst performance. The liquid phase method synthesized material has good performance but has high corrosion resistance requirements for equipment, resulting in high costs and greater pressure on the environmental protection.

[0005] In order to solve the above technical problems, the prior art discloses a new solid phase process to synthesize LiMn x Fe 1-xPO4 material, this method improves the performance of the material and has the characteristics of low cost. However, it uses manganese and iron sulfate as manganese source and iron source, resulting in the synthesis reaction to generate toxic gas sulfur dioxide that needs to be treated, and due to the different thermal decomposition temperatures of the two sulfates, the generated manganese iron oxide is easy to agglomerate, and the synthetic manganese iron lithium oxide has a high hardness, which is difficult to ball mill, and is not conducive to the generation of high-purity manganese iron phosphate. In addition, the method has a long reaction time and a high reaction temperature. At the same time, the purity of manganese iron oxide synthesized by the reaction of manganese salt and iron salt is relatively small, and there are also miscellaneous phase byproducts such as iron oxide and manganese oxide. For example, a Chinese patent discloses a preparation method, positive electrode material and lithium ion battery of manganese iron phosphate (publication number CN116969435A), by first mixing a manganese source and an iron source, directly using solid phase sintering to obtain manganese iron oxide; then the manganese iron oxide is solid-phase mixed with a lithium source and a phosphorus source, and solid-phase sintering is performed at a certain temperature to obtain lithium manganese iron phosphate. This method directly mixes the iron source and the manganese source in the solid phase and then sintering, resulting in uneven mixing of manganese and iron, and the final product has poor performance. Summary of the invention

[0006] The present invention aims to solve the technical problems in the prior art that the solid phase method for preparing lithium manganese iron phosphate has a simple process but poor performance of the synthesized material, and the liquid phase method for preparing lithium manganese iron phosphate has good performance of the synthesized material but high cost and great pressure on the environmental protection. A manganese iron oxide precursor and a preparation method and application thereof are provided. The manganese iron oxide precursor has uniform element distribution. The lithium manganese iron phosphate composite material prepared using the precursor has excellent performance, low cost, high compaction density and high gram capacity.

[0007] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a method for preparing a manganese iron oxide precursor, the steps of which are as follows:

[0009] The iron source, manganese source, SiO2 and alkaline oxide are solid-phase mixed and sintered in air or oxygen atmosphere to obtain a manganese iron oxide precursor;

[0010] At least one of the iron source and the manganese source is an oxide;

[0011] In the manganese iron oxide precursor, the molar ratio of Mn:Fe is x:(1-x), and x is 0.6-0.8;

[0012] The amount of SiO2 added is 0.3wt%-1.5wt%;

[0013] The basic oxide is added in an amount of 0.1 wt% to 1 wt%.

[0014] Preferably, the iron source is one or more of ferroferric oxide, ferrous oxide, ferrous basic oxide (FeO(OH)), ferric hydroxide, ferrous hydroxide, ferrous sulfate, ferrous sulfate, ferric carbonate, ferrous oxalate, ferrous oxalate, ferrous acetate, and ferric citrate.

[0015] Preferably, the manganese source is one or more of manganese tetraoxide, manganese trioxide, manganous oxide, manganese dioxide, monohydroxy manganese oxide (MnO(OH)), hydrated manganese dioxide (MnO(OH)2), manganese hydroxide (Mn(OH)2), manganese sulfate, manganese carbonate, manganese oxalate, and manganese acetate.

[0016] Preferably, the basic oxide is one or more of calcium oxide, barium oxide, chromium oxide, aluminum oxide, beryllium oxide, and zinc oxide.

[0017] Preferably, the sintering temperature is 200-900° C., the heating rate is 3-5° C. / min, and the sintering time is 4-15 h.

[0018] The present invention also provides a manganese iron oxide precursor prepared by the above-mentioned method for preparing the manganese iron oxide precursor.

[0019] The present invention also provides a lithium manganese iron phosphate composite material prepared by using the above-mentioned manganese iron oxide precursor.

[0020] The present invention also provides a method for preparing the above-mentioned lithium iron manganese phosphate composite material, the steps of which are as follows:

[0021] The manganese iron oxide precursor, the phosphorus source and the lithium source are wet-grinded, spray-dried and sintered under an inert atmosphere to obtain a manganese iron lithium phosphate composite material;

[0022] The amounts of the manganese iron oxide precursor, phosphorus source and lithium source are prepared according to the element molar ratio of Li:(Mn+Fe):P=(1.01-1.1):1:1.

[0023] Preferably, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium oxalate, lithium acetate, lithium sulfate, lithium nitrate, and lithium chloride.

[0024] Preferably, the phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium tripolyphosphate, phosphoric acid, calcium phosphate, phosphate ester, lithium dihydrogen phosphate, iron phosphate, lithium phosphate, lithium dihydrogen phosphate, and manganese phosphate.

[0025] Preferably, when the manganese iron oxide precursor, the phosphorus source and the lithium source are wet-milled, one or more of a carbon source and a doping ion source are also added for wet-milling;

[0026] The amount of the carbon source added is 15wt%-25wt%, and the amount of the doping ion source added is 0.1wt%-1wt%.

[0027] More preferably, the carbon source is one or more of glucose, starch, and polyethylene glycol;

[0028] More preferably, the doping element of the doping ion source is one or more of aluminum, magnesium, nickel, cobalt, titanium, copper, calcium, niobium, chromium, zinc, lanthanum, antimony, tellurium, strontium, tungsten, indium, and yttrium; and the doping ion source is an oxide, carbonate, nitrate, sulfate or oxalate of the corresponding metal element.

[0029] Preferably, the solid content of the wet grinding is 35wt%-45wt%.

[0030] Preferably, the wet grinding is performed to a material particle size D50 of 0.5-0.6 μm.

[0031] Preferably, the spray drying conditions are: air inlet temperature is 200-260°C, and air outlet temperature is 100-110°C.

[0032] Preferably, the sintering temperature is 500-900° C., the heating rate is 3-5° C. / min, and the sintering time is 4-20 h.

[0033] Preferably, the inert atmosphere is one or more of nitrogen, helium and argon.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The preparation method of the lithium iron manganese phosphate composite material of the present invention comprises the following steps: in the sintering process of the manganese iron oxide precursor, in addition to the manganese source and the iron source, SiO2 and an alkaline oxide are added, the manganese source, the iron source and the SiO2 form a eutectic, and the alkaline oxide is used as a flux to reduce the sintering temperature, so that the elements of the finally synthesized manganese iron oxide precursor are uniformly distributed, and the lithium iron manganese phosphate synthesized by the manganese iron oxide precursor has excellent performance, low cost, high compaction density and high gram capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only 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.

[0037] Figure 1 This is the charge and discharge curve of the lithium manganese iron phosphate composite material of Example 1 of the present invention. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with embodiments.

[0039] In the following examples, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, devices, instruments, equipment, etc. used in the following examples can be obtained from commercial sources.

[0040] Example 1

[0041] S1. Iron oxide and manganese trioxide are prepared in a molar ratio of Mn:Fe=0.6:0.4, and 0.5wt% SiO2 and 0.3wt% alumina are added and mixed in the solid phase; the mixed material is sintered in air, the temperature is increased to 600°C at 3°C / min, and the temperature is kept for 8 hours to complete the sintering, thereby obtaining a manganese iron oxide precursor.

[0042] S2. Manganese iron oxide precursor, ammonium dihydrogen phosphate and lithium carbonate are prepared in an element molar ratio of Li: (Mn + Fe): P = 1.01:1:1, and mixed with deionized water at a solid content of 40wt%, and glucose is added, wherein the amount of glucose added accounts for 20wt% of the theoretical amount of the finished product; then stirred at a speed of 200r / min for 1h, and slurry A is obtained after completion.

[0043] S3, grinding the slurry A obtained in S2, and the slurry particle size D50 after sand grinding is 0.5μm, and spraying is performed with an inlet air temperature of 200℃ and an outlet air temperature of 100℃. After completion, the temperature is raised to 200℃ at 3℃ / min in a nitrogen atmosphere, and kept warm for 1h, and then raised to 700℃ and kept warm for 5h to complete sintering to obtain a lithium manganese iron phosphate composite material.

[0044] Example 2

[0045] The difference between Example 2 and Example 1 is that the amount of SiO2 added is changed to 0.3wt%.

[0046] Example 3

[0047] The only difference between Example 3 and Example 1 is that the amount of SiO2 added is changed to 0.8wt%.

[0048] Example 4

[0049] The only difference between Example 4 and Example 1 is that the amount of aluminum oxide added is changed to 0.1 wt%.

[0050] Example 5

[0051] The only difference between Example 5 and Example 1 is that the amount of aluminum oxide added is changed to 0.6 wt %.

[0052] Example 6

[0053] The only difference between Example 6 and Example 1 is that the type of basic oxide is changed, and aluminum oxide is replaced by barium oxide.

[0054] Comparative Example 1

[0055] The LMFP used in Comparative Example 1 is the commercialized LMFP in the current market, and the synthesis route is a finished product LMFP prepared by using ferromanganese phosphate as a precursor.

[0056] Comparative Example 2

[0057] The only difference between Comparative Example 2 and Example 1 is that no SiO2 is added.

[0058] Comparative Example 3

[0059] The only difference between Comparative Example 3 and Example 1 is that no basic oxide alumina is added.

[0060] Comparative Example 4

[0061] The only difference between Comparative Example 4 and Example 1 is that SiO2 and aluminum oxide are not added.

[0062] The lithium iron manganese phosphate composite materials of Examples 1-6 and Comparative Examples 1-4 were tested. Test method: The relevant physical and chemical properties and electrochemical properties were tested with reference to the national standard "Carbon composite lithium iron phosphate positive electrode material for lithium ion batteries" GB / T 30835-2014, wherein button batteries were made (the mass ratio of active material, conductive agent and binder was 90:5:5, and the charge and discharge voltage range was 2.0-4.4V).

[0063] The test results are shown in Table 1 and Figure 1 shown.

[0064] Table 1 Performance of lithium manganese iron phosphate composite materials of Examples 1-6 and Comparative Examples 1-4

[0065]

[0066]

[0067] The above data show that after adding SiO2 and alkaline oxide, the compaction density and gram capacity of the lithium manganese iron phosphate composite material are improved. The compaction density of the lithium manganese iron phosphate composite material of Example 1 is 2.79 g / cm 3, much higher than that of Comparative Example 1; and its gram capacity is 2.5 mAh higher than that of Comparative Example 2 without adding SiO2, 8.2 mAh higher than that of Comparative Example 3 without adding alkaline oxide, and 9.1 mAh higher than that of Comparative Example 4 without adding either.

[0068] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A method for preparing a manganese iron oxide precursor, characterized in that: Here are the steps: The iron source, manganese source, SiO2 and alkaline oxide are solid-phase mixed and sintered in air or oxygen atmosphere to obtain a manganese iron oxide precursor; At least one of the iron source and the manganese source is an oxide; In the manganese iron oxide precursor, the molar ratio of Mn:Fe is x:(1-x), and x is 0.6-0.8; The amount of SiO2 added is 0.3wt%-1.5wt%; The basic oxide is added in an amount of 0.1 wt% to 1 wt%.

2. The method for preparing a manganese iron oxide precursor according to claim 1, characterized in that: The iron source is one or more of ferroferric oxide, ferrous oxide, ferrous hydroxide, ferrous hydroxide, ferrous sulfate, ferrous sulfate, ferric carbonate, ferrous oxalate, ferrous oxalate, ferrous acetate, and ferric citrate; And / or, the manganese source is one or more of manganese tetraoxide, manganese trioxide, manganous oxide, manganese dioxide, monohydroxy manganese oxide, hydrated manganese dioxide, manganese hydroxide, manganese sulfate, manganese carbonate, manganese oxalate, and manganese acetate; And / or, the basic oxide is one or more of calcium oxide, barium oxide, chromium oxide, aluminum oxide, beryllium oxide, and zinc oxide.

3. The method for preparing the ferromanganese oxide precursor according to claim 1, characterized in that: The sintering temperature is 200-900° C., the heating rate is 3-5° C. / min, and the sintering time is 4-15h.

4. A manganese iron oxide precursor prepared according to the method for preparing a manganese iron oxide precursor according to any one of claims 1 to 3.

5. A lithium iron manganese phosphate composite material prepared using the manganese iron oxide precursor according to claim 4.

6. The method for preparing the lithium iron manganese phosphate composite material according to claim 5, characterized in that: Here are the steps: The manganese iron oxide precursor, the phosphorus source and the lithium source are wet-grinded, spray-dried and sintered under an inert atmosphere to obtain a manganese iron lithium phosphate composite material; The amounts of the manganese iron oxide precursor, the phosphorus source and the lithium source are prepared according to the element molar ratio of Li:(Mn+Fe):P=(1.01-1.1):1:

1.

7. The method for preparing the lithium iron manganese phosphate composite material according to claim 6, characterized in that: The lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium oxalate, lithium acetate, lithium sulfate, lithium nitrate, and lithium chloride; And / or, the phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium tripolyphosphate, phosphoric acid, calcium phosphate, phosphate ester, lithium dihydrogen phosphate, iron phosphate, lithium phosphate, lithium dihydrogen phosphate, and manganese phosphate.

8. The method for preparing the lithium iron manganese phosphate composite material according to claim 6, characterized in that: When the manganese iron oxide precursor, the phosphorus source and the lithium source are wet-milled, one or more of a carbon source and a doping ion source are also added for wet-milling; The carbon source is one or more of glucose, starch, and polyethylene glycol; The amount of the carbon source added is 15wt%-25wt%; The doping element of the doping ion source is one or more of aluminum, magnesium, nickel, cobalt, titanium, copper, calcium, niobium, chromium, zinc, lanthanum, antimony, tellurium, strontium, tungsten, indium, and yttrium; The doping ion source is added in an amount of 0.1 wt%-1 wt%.

9. The method for preparing the lithium iron manganese phosphate composite material according to claim 6, characterized in that: The solid content of the wet grinding is 35wt%-45wt%; And / or, the wet grinding is performed to a material particle size D50 of 0.5-0.6 μm.

10. The method for preparing the lithium iron manganese phosphate composite material according to claim 6, characterized in that: The spray drying conditions are: the air inlet temperature is 200-260°C, and the air outlet temperature is 100-110°C; And / or, the sintering temperature is 500-900°C, the heating rate is 3-5°C / min, and the sintering time is 4-20h; And / or, the inert atmosphere is one or more of nitrogen, helium, and argon.

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