Preparation method and application of positive electrode material precursor

Abstract

The invention discloses a preparation method and application of a positive electrode material precursor. The preparation method comprises the following steps: S1, mixing a manganese source, an iron source, a phosphorus source and hydrochloric acid to form a mixed solution; s2, carrying out fluidized roasting on the mixed solution obtained in the step S1 to form a MnxFe1-x (PO4-x / 2) z precursor; the chemical general formula of the positive electrode material precursor is MnxFe1-x (PO4-x / 2) z, x is more than or equal to 0.5 and less than or equal to 0.95, and z is more than or equal to 0.95 and less than or equal to 1.10; in the MnxFe1-x (PO4-x / 2) z precursor, manganese is bivalent, and iron is trivalent. The invention provides a preparation method and application of a positive electrode material precursor. The precursor material is uniform in ferromanganese compound distribution, stable in crystal structure, controllable in particle size and high in tap density.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary battery raw materials, and in particular to a preparation method of a positive electrode material precursor and application thereof. Background Art

[0002] Lithium iron manganese phosphate is a new type of phosphate-based lithium-ion battery cathode material, which is expected to become the mainstream of lithium battery cathode materials in the future. Compared with lithium iron phosphate, lithium iron manganese phosphate has the advantages of higher energy density and low temperature performance; compared with ternary materials, lithium iron manganese phosphate has higher safety and cost advantages, so lithium iron manganese phosphate is gradually being widely used in the field of new energy. However, the main defects of lithium iron manganese phosphate materials are the uneven distribution of manganese and iron in its microstructure, manganese dissolution, poor conductivity and low compaction density. In terms of preparation process, there are mainly problems such as complex process flow, harsh control conditions and high environmental treatment cost. Existing research uses a carbon coating layer containing N to improve the conductivity of lithium iron manganese phosphate, inhibit the dissolution of Mn, and improve the electrochemical properties of the material. There are also studies that use coprecipitation reaction combined with vanadium doping to prepare iron manganese vanadium phosphate precursor materials and obtain lithium iron manganese vanadium phosphate / carbon cathode materials. However, in the precursor preparation process mentioned in the above invention, the mixing uniformity of the manganese and iron elements during the reaction cannot be controlled, resulting in a disordered crystal structure and uneven element distribution inside the precursor material, which ultimately leads to a decrease in the performance of the positive electrode material. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a preparation method and application of a positive electrode material precursor. The precursor material has a uniform distribution of manganese iron compounds, a stable crystal structure, a controllable particle size, and a high tap density.

[0004] The present invention also provides application of the positive electrode material precursor.

[0005] According to an embodiment of the first aspect of the present invention, a method for preparing a positive electrode material precursor is proposed, comprising:

[0006] S1. Mixing a manganese source, an iron source, a phosphorus source, and hydrochloric acid into a mixed solution;

[0007] S2. The mixed solution in step S1 is subjected to fluidized calcination to form Mn x Fe 1-x (PO 4-x / 2 ) z Precursor;

[0008] The chemical formula of the positive electrode material precursor is Mn x Fe 1-x (PO 4-x / 2 ) z, where 0.5≤x≤0.95, 0.95≤z≤1.10;

[0009] The Mn x Fe 1-x (PO 4-x / 2 ) z In the precursor, manganese is divalent and iron is trivalent.

[0010] According to the first aspect of the present invention, there are at least the following beneficial effects:

[0011] The Mn prepared by the present invention x Fe 1-x (PO 4-x / 2 ) z The precursor has the advantages of uniform phase mixing, high tap density and high reaction activity. The manganese is divalent, which can greatly reduce the amount of carbon source used in the subsequent sintering process of the positive electrode material. When manganese is in a divalent state, its reduction degree is high, which means that during the carbon thermal reduction process, the carbon source required for the redox reaction of manganese is less, reducing the consumption of the carbon source. The chemical properties of trivalent iron are relatively stable. By controlling the iron to be trivalent, more Fe3+ can be promoted to combine with other sources (such as manganese sources, phosphorus sources, etc.) to form stable compounds, and the required reduction reactions are relatively few, further reducing the consumption of carbon sources. The manganese ferrophosphate precursor material prepared by the fluidized calcination process adopted in the present invention has the advantages of uniform distribution of manganese iron compounds, stable crystal structure, controllable particle size, high tap density, and simple synthesis reaction of positive electrode materials. During the fluidized calcination process, the material is carried by the airflow, the contact between the particles is more uniform, and the temperature distribution is more uniform, ensuring the uniform heating of the reaction materials, thereby avoiding the problem of incomplete or uneven material reaction caused by local excessively high or low temperatures.

[0012] According to some embodiments of the present invention, the Mn x Fe 1-x (PO 4-x / 2 ) z The primary particles of the precursor are at least one of flake, spherical, elliptical, rectangular and blocky, and the secondary particles are agglomerates of the primary particles, and the particle size D50 thereof is in the range of 2-10 μm.

[0013] Fluidized bed calcination reacts at high temperature to form primary particles. After fluidized bed calcination, the primary particles form larger agglomerates. These agglomerates are secondary particles. Because the reaction is fast during fluidized bed calcination, the primary particles are very small, perhaps only nanometers in size, and agglomerate together to form secondary particles. During fluidized bed calcination, the particle size of the primary particles is very small. The smaller particle size helps to increase the specific surface area of ​​the particles, thereby increasing the activity of the reaction. The D50 of the secondary particles is between 2-10μm. Relatively large agglomerates can provide a particle structure suitable for the subsequent synthesis of positive electrode materials.

[0014] According to some embodiments of the present invention, the Mn x Fe 1-x (PO 4-x / 2 ) z The tap density of the precursor is 0.5-1.5g / cm 3 .

[0015] According to some embodiments of the present invention, the Mn x Fe 1-x (PO 4-x / 2 ) z The specific surface area of ​​the precursor is 1-15m 2 / g.

[0016] According to some embodiments of the present invention, the mass concentration of hydrochloric acid in the mixed solution is 5%-30%.

[0017] According to some embodiments of the present invention, the temperature of the fluidized calcination is 400°C-800°C.

[0018] According to some embodiments of the present invention, the fluidized calcination time is 2-60 min.

[0019] According to some embodiments of the present invention, the manganese source includes at least one of metallic manganese, manganese monoxide, manganese dioxide, dimanganese trioxide, trimanganese tetroxide, manganese phosphate, manganese hydroxide, manganese oxyhydroxide, manganese oxalate, manganese chloride, manganese carbonate, manganese acetate and hydrates thereof.

[0020] According to some embodiments of the present invention, the iron source includes at least one of metallic iron, ferrous oxide, ferrous oxide, ferric oxide, ferric oxyhydroxide, ferric phosphate, ferric oxalate, ferrous oxalate, ferric chloride, ferrous chloride, ferrous acetate, ferrous carbonate, ferrous hydroxide, ferric hydroxide and hydrates thereof.

[0021] According to some embodiments of the present invention, the phosphorus source includes at least one of phosphoric acid, metaphosphoric acid, phosphorous acid, iron phosphate, manganese phosphate, phosphorus pentoxide and hydrates thereof.

[0022] According to some embodiments of the present invention, the molar ratio of the iron source to the manganese source in step S1 is 1:(1-19).

[0023] According to some embodiments of the present invention, the ratio of the sum of the moles of the iron source and the manganese source to the mole of the phosphorus source is 1:0.95-1.10.

[0024] According to an embodiment of the second aspect of the present invention, a positive electrode material lithium manganese iron phosphate is proposed, and the raw materials for preparing the positive electrode material lithium manganese iron phosphate include the positive electrode material precursor prepared by the above preparation method.

[0025] According to some embodiments of the present invention, the general chemical formula of the lithium manganese iron phosphate is Li 1+u Mn x Me y Fe 1-x-y (PO 4 ) z / C, -0.05≤u≤0.10, 0.50≤x≤0.95, 0≤y≤0.1, 0.95≤z≤1.10;

[0026] Me is at least one of V, Al, Mg, Ti, Nb, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc.

[0027] According to some embodiments of the present invention, the Li 1+u Mn x Me y Fe 1-x-y PO 4 The morphology of / C is at least one of flake, spherical, elliptical, rectangular and blocky, the particle size D50 of the primary particles is in the range of 0.1-1.0 μm, the secondary particles are agglomerates of the primary particles, and the particle size D50 of the secondary particles is in the range of 0.5-10 μm.

[0028] According to some embodiments of the present invention, the 1+u Mn x Me y Fe 1-x-y PO 4 The specific surface area of ​​ / C is 5-25m 2 / g.

[0029] According to some embodiments of the present invention, the Li 1+u Mn x Me y Fe 1-x-y PO 4 / C compaction density is 2.1-2.6g / cm 3 .

[0030] According to some embodiments of the present invention, the Li 1+u Mn x Me y Fe 1-x-y PO 4 The carbon content of / C is 0.5-4%.

[0031] According to some embodiments of the present invention, the Li 1+u Mn x Mey Fe 1-x-y PO 4 The preparation method of / C comprises: x Fe 1-x (PO 4-x / 2 ) z The precursor material is mixed with a lithium source, an additive, and a carbon source, ground to form a mixed material, carbon thermally reduced in an inert gas atmosphere, naturally cooled to room temperature, and finally pulverized to obtain Li 1+u Mn x Me y Fe 1-x-y (PO 4 ) z / C positive electrode material finished product.

[0032] Li 1+u Mn x Me y Fe 1-x-y PO 4 The preparation method of / C has a simple production process, low equipment requirements, and strong process controllability. In addition, the chlorine element produced in the entire process can be recycled, which is green and environmentally friendly, with low cost and energy consumption, and no additional environmental protection treatment facilities are required, making it very suitable for large-scale production. Precursors and cathode materials of different specifications can be produced by adjusting the raw material ratio, and the application scope and applicable scenarios of the products can be expanded according to customer needs.

[0033] According to some embodiments of the present invention, the Mn x Fe 1-x (PO 4-x / 2 ) z The molar ratio of the precursor to the lithium source is 1:(0.95-1.05).

[0034] According to some embodiments of the present invention, the additive includes at least one of V, Al, Mg, Ti, Nb, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc metals and their oxides.

[0035] According to some embodiments of the present invention, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium oxalate, lithium acetate, lithium phosphate and lithium dihydrogen phosphate.

[0036] According to some embodiments of the present invention, the carbon source includes at least one of glucose, sucrose, fructose, polypropylene alcohol, polyethylene glycol, citric acid, phenolic resin, graphite, carbon black, acetylene black, carbon nanotubes and graphene.

[0037] According to some embodiments of the present invention, the content of the carbon source is Mn x Fe1-x (PO 4-x / 2 ) z 5wt.%-20wt.% of the total amount of the precursor and the lithium source.

[0038] According to some embodiments of the present invention, the inert gas includes at least one of nitrogen, hydrogen and argon.

[0039] According to some embodiments of the present invention, the temperature of the carbon thermal reduction is 500-800° C., and the time of the carbon thermal reduction is 4-20 h.

[0040] According to an embodiment of the third aspect of the present invention, a lithium-ion battery is provided, wherein the raw materials for preparing the lithium-ion battery include the modified positive electrode material lithium manganese iron phosphate.

[0041] If there is no special explanation, the actual meaning of “about” in the present invention is that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

[0042] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0043] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0045] Figure 1 is a SEM image of the precursor prepared in Example 1 of the present invention;

[0046] Figure 2 is the XRD pattern of the precursor prepared in Example 1 of the present invention;

[0047] Figure 3 is a SEM image of the lithium manganese iron phosphate material prepared in Example 1 of the present invention;

[0048] Figure 4 is the XRD pattern of the lithium iron manganese phosphate material prepared in Example 1 of the present invention;

[0049] Figure 5 It is a schematic diagram of the process flow of preparing the lithium manganese iron phosphate positive electrode material of the present invention. DETAILED DESCRIPTION

[0050] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0051] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0052] The quality of the prepared raw materials is only used to indicate the proportion, and does not represent the actual quality. In actual production, the output can be proportionally increased or decreased according to demand.

[0053] Example 1

[0054] In this example, a positive electrode material precursor and a positive electrode material lithium manganese iron phosphate are prepared, specifically:

[0055] The preparation method of the positive electrode material precursor is as follows:

[0056] S1. Weigh 59.80 g of 99.0% pure Mn 2 O 3 , 15.4 g of 99.0% pure Fe 2 O 3 , 72.4 g of 99.0% pure P 2 O 5 , 547.5 g of 20% HCl solution were mixed and stirred to form a uniform mixed solution;

[0057] S2. The above solution is subjected to fluidized calcination at a temperature of 700°C for 10 min to form Mn 0.75 Fe 0.25 (PO 3.625 ) 1.01 Precursor.

[0058] The preparation method of the positive electrode material lithium manganese iron phosphate is as follows:

[0059] S3. Mn 0.75 Fe 0.25 (PO 3.625 )1.01 The precursor material and 51.8 g of 99.5% pure Li 2 C 2 O 4 , 3.1 g of 99.0% pure vanadium metal powder, and 11.9 g of 99.5% pure polyethylene glycol were mixed and ground, and the mixture was carbon thermally reduced under nitrogen atmosphere at a temperature of 800°C for 10 h. After the reaction was completed, it was naturally cooled and finally crushed to obtain Li 1.01 Mn 0.75 V 0.06 Fe 0.19 (PO 4 ) 1.01 / C positive electrode material finished product.

[0060] The SEM image of the precursor prepared in Example 1 is as follows Figure 1 As shown in the figure, it can be seen that the particle morphology of the precursor is uniform, the primary particles are flake or block-shaped, and the particle size of the secondary particles is about 5μm.

[0061] The XRD pattern of the precursor prepared in Example 1 is as follows: Figure 2 As shown, the phase shown is a phosphate crystal structure of divalent manganese and trivalent iron, without other impurity peaks;

[0062] The SEM image of the lithium manganese iron phosphate material prepared in Example 1 is as follows Figure 3 As shown, the primary particles are block-shaped or elliptical particles with a size of about 1 μm, and the surface carbon layer is tightly coated and evenly distributed;

[0063] The XRD pattern of the lithium manganese iron phosphate material prepared in Example 1 of the present invention is as follows: Figure 4 As shown, the phase shown is the phase of lithium manganese iron phosphate, and no other impurity peaks are generated, indicating that lithium manganese iron phosphate crystals with higher purity are generated;

[0064] The schematic diagram of the preparation process of the lithium manganese iron phosphate positive electrode material of the present invention is as follows Figure 5 shown.

[0065] Example 2

[0066] In this example, a positive electrode material precursor and a positive electrode material lithium manganese iron phosphate are prepared, specifically:

[0067] The preparation method of the positive electrode material precursor is as follows:

[0068] S1. Weigh 38.90 g of 99.0% pure Mn metal powder, 14.7 g of 99.0% pure Fe metal powder, and 117.6 g of 85% H 3 PO 4 , 405.6 g of 18% HCl solution were mixed and stirred to form a uniform mixed solution;

[0069] S2. The above solution is subjected to fluidized calcination at a temperature of 600°C for 20 min to form Mn 0.7 Fe 0.3 (PO 3.65 ) 1.02 Precursor.

[0070] The preparation method of the positive electrode material lithium manganese iron phosphate is as follows:

[0071] S3. Mn 0.7 Fe 0.3 (PO 3.65 ) 1.02 The precursor material and 37.9 g of 99.5% pure Li 2 CO 3 , 1.9 g of 99.0% pure Ti metal powder, and 6.3 g of 99.5% pure glucose were mixed and ground, and the mixture was carbon thermally reduced under nitrogen atmosphere at a temperature of 750°C for 8 h. After the reaction was completed, it was naturally cooled and finally crushed to obtain Li 1.02 Mn 0.7 Ti 0.04 Fe 0.26 (PO 4 ) 1.02 / C positive electrode material finished product.

[0072] Example 3

[0073] In this example, a positive electrode material precursor and a positive electrode material lithium manganese iron phosphate are prepared, specifically:

[0074] The preparation method of the positive electrode material precursor is as follows:

[0075] S1. Weigh 119.9 g of 99.0% pure MnCl 2 ·4H 2 O, 46.6 g of 98.0% pure FeCl 2 , 201.9 g of 50% H 3 PO 4 Mix and stir to form a uniform mixed solution;

[0076] S2. The above solution is subjected to fluidized calcination at a temperature of 500°C for 5 minutes to form Mn 0.6 Fe 0.4 (PO 3.7 ) 1.03 Precursor.

[0077] The preparation method of the positive electrode material lithium manganese iron phosphate is as follows:

[0078] S3. Mn0.6 Fe 0.4 (PO 3.7 ) 1.03 The precursor material and 38.3 g of 99.5% pure Li 2 CO 3 1.0 g of 99.0% pure Mg metal powder and 8.6 g of 99.5% pure glucose were mixed and ground, and the mixture was carbon thermally reduced under nitrogen atmosphere at a temperature of 700°C for 6 h. After the reaction was completed, it was naturally cooled and finally crushed to obtain Li 1.03 Mn 0.6 Mg 0.04 Fe 0.36 (PO 4 ) 1.03 / C positive electrode material finished product.

[0079] Example 4

[0080] In this example, a positive electrode material precursor and a positive electrode material lithium manganese iron phosphate are prepared, specifically:

[0081] The preparation method of the positive electrode material precursor is as follows:

[0082] S1. Weigh 46.6 g of 99.0% pure MnO, 23.3 g of 99.0% pure FeO, and 74.6 g of 99.0% pure P 2 O 5 , 456.3 g of 16% HCl solution were mixed and stirred to form a uniform mixed solution;

[0083] S2. The above solution is subjected to fluidized calcination at a temperature of 550°C for 40 min to form Mn 0.65 Fe 0.35 (PO 3.675 ) 1.04 Precursor.

[0084] The preparation method of the positive electrode material lithium manganese iron phosphate is as follows:

[0085] S3. Mn 0.65 Fe 0.35 (PO 3.675 ) 1.04 The precursor material was mixed with 25.1 g of 99.5% pure LiOH, 2.8 g of 99.0% pure Nb metal powder, and 13.3 g of 99.5% pure citric acid and ground. After the mixture was formed, it was carbon thermally reduced under an argon atmosphere at a temperature of 650°C for 12 h. After the reaction was completed, it was naturally cooled and finally crushed to obtain Li 1.04 Mn 0.65 Nb 0.03 Fe0.32 (PO 4 ) 1.04 / C positive electrode material finished product.

[0086] Example 5

[0087] In this example, a positive electrode material precursor and a positive electrode material lithium manganese iron phosphate are prepared, specifically:

[0088] The preparation method of the positive electrode material precursor is as follows:

[0089] S1. Weigh 71.9 g of 99.0% pure Mn(OH) 2 , 15.1 g of 99.0% pure Fe(OH) 3 , 118.8 g of 85% H 3 PO 4 , 456.3 g of 24% HCl solution were mixed and stirred to form a uniform mixed solution;

[0090] S2. The above solution is subjected to fluidized calcination at a temperature of 750°C for 2 minutes to form Mn 0.8 Fe 0.2 (PO 3.6 ) 1.03 Precursor.

[0091] The preparation method of the positive electrode material lithium manganese iron phosphate is as follows:

[0092] S3. Mn 0.8 Fe 0.2 (PO 3.6 ) 1.03 The precursor material and 38.3 g of 99.5% pure Li 2 CO 3 , 2.8 g of 99.0% pure Nb metal powder, 1.0 g of 99.0% pure Ti metal powder, 0.2 g of 99.0% pure Mg metal powder, 2.1 g of 99.5% pure glucose, and 4.7 g of 99.5% pure polyethylene glycol were mixed and ground to form a mixture, which was then carbon thermally reduced under an argon atmosphere at a temperature of 725°C for 8 hours. After the reaction was completed, the mixture was naturally cooled and finally pulverized to obtain Li 1.03 Mn 0.8 Nb 0.03 Ti 0.02 Mg 0.01 Fe 0.14 (PO 4 ) 1.03 / C positive electrode material finished product.

[0093] Comparative Example 1

[0094] In this example, a positive electrode material precursor and a positive electrode material lithium manganese iron phosphate are prepared, specifically:

[0095] The preparation method of the positive electrode material precursor is as follows:

[0096] S1. Weigh the same mass of Mn as described in Example 1. 2 O 3 , Fe 2 O 3 and vanadium metal powder, and weigh 117.9 g of 98.5% pure NH 4 H 2 PO 4 , 37.6 g of 99.5% pure Li 2 CO 3 2. 38.6 g of polyethylene glycol with a purity of 99.5% were added to 347.6 g of pure water respectively, and the mixture was ground and stirred to form a uniform mixed solution. The mixed solution was spray-dried to form a lithium manganese iron phosphate precursor.

[0097] The preparation method of the positive electrode material lithium manganese iron phosphate is as follows:

[0098] S2. Place the lithium manganese iron phosphate precursor material into a sintering furnace for sintering in an atmosphere of N 2 , heated to 800℃ and calcined for 10h, and finally the powder was crushed to obtain Li 1.01 Mn 0.75 V 0.06 Fe 0.19 (PO 4 ) 1.01 / C Finished product.

[0099] Comparative Example 2

[0100] In this example, a positive electrode material, lithium manganese iron phosphate, was prepared. The same raw materials were used as in Example 1, but fluidized calcination was not used in the process, that is, manganese was not controlled to be divalent and iron was not controlled to be trivalent. Specifically:

[0101] S1. Weigh 59.80 g of 99.0% pure Mn 2 O 3 , 15.4 g of 99.0% pure Fe 2 O 3 , 116.45 g of 85.0% pure H 3 PO 4 51.8 g of 99.5% pure Li 2 C 2 O 4, 3.1 g of 99.0% pure vanadium metal powder, and 11.9 g of 99.5% pure polyethylene glycol were mixed and ground, and the mixture was carbon thermally reduced under nitrogen atmosphere at a temperature of 800°C for 10 h. After the reaction was completed, it was naturally cooled and finally crushed to obtain Li 1.01 Mn 0.75 V 0.06 Fe 0.19 (PO 4 ) 1.01 / C positive electrode material finished product.

[0102] Test Example 1

[0103] In this example, the particle size, tap density and specific surface area of ​​the precursor materials prepared in the examples and comparative examples were measured, as shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] It can be seen from Table 1 above that compared with the ordinary spray drying process, the precursor material using the fluidized bed calcination process has a smaller particle size, a larger tap density, and a larger specific surface area, which is beneficial to the subsequent positive electrode material preparation process.

[0108] Test Example 2

[0109] In this example, the physical properties of the lithium manganese iron phosphate positive electrode materials of the embodiment and the comparative example were measured, as shown in Table 2.

[0110] Table 2

[0111]

[0112] It can be seen from Table 2 above that the positive electrode material synthesized from the precursor material prepared by the fluidized bed calcination process has the characteristics of small particle size, large compaction density, and moderate specific surface area. It has good processing performance, which is beneficial to the performance of the positive electrode material and the improvement of the energy density of the prepared battery.

[0113] Test Example 3

[0114] The present invention measures the electrochemical properties of the lithium iron manganese phosphate electrode materials prepared in the embodiments and comparative examples, and uses button batteries for characterization. The positive electrode active material uses the lithium iron manganese phosphate positive electrode materials prepared in the embodiments and comparative examples, respectively, the negative electrode uses a lithium sheet, the conductive agent uses Super P, the binder uses polyvinylidene fluoride, the diaphragm uses Celgard 2500 composite membrane, and the electrolyte uses 1 mol / L lithium hexafluorophosphate as a lithium salt, and a volume ratio of 1:1 dimethyl carbonate (DMC) and ethylene carbonate (EC) solution is used as a solvent. The mass ratio of the positive active material, the conductive agent and the binder is 8:1:1. The assembly of the button battery is completed in a glove box with an argon protective atmosphere. The electrochemical performance test of the button battery was carried out using a blue electric test cabinet, and the test voltage range was set to 2.8V~4.5V. The results are shown in Table 3.

[0115] Table 3

[0116]

[0117] From the comparison in the above table, it can be seen that the lithium iron manganese phosphate cathode material prepared by the novel preparation process of the present invention has a high first coulomb efficiency, 1C discharge capacity and cycle retention rate, indicating the superiority of its process; in addition, the process flow proposed by this patent does not contain ammonia, and the gas generated in the process can be recycled for recycling, which can greatly reduce the equipment cost of environmental protection treatment in industrial production, and is a green environmental protection process. The chlorine element in the entire process is recycled, and does not contain ammonia, nitrate, etc., and the environmental protection cost is greatly reduced. It belongs to a green environmental protection process, and can obtain lithium iron manganese phosphate cathode materials with excellent processing performance and outstanding electrical properties.

[0118] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing a positive electrode material precursor, characterized in that: include: S1. Mixing a manganese source, an iron source, a phosphorus source, and hydrochloric acid into a mixed solution; S2. The mixed solution in step S1 is subjected to fluidized calcination to form Mn x Fe 1-x (PO 4-x / 2 ) z Precursor; The chemical formula of the positive electrode material precursor is Mn x Fe 1-x (PO 4-x / 2 ) z , where 0.5≤x≤0.95, 0.95≤z≤1.10; The Mn x Fe 1-x (PO 4-x / 2 ) z In the precursor, manganese is divalent and iron is trivalent.

2. The method for preparing a cathode material precursor according to claim 1, characterized in that: The temperature of the fluidized calcination is 400°C-800°C.

3. The method for preparing a cathode material precursor according to claim 1, characterized in that: The manganese source includes at least one of metallic manganese, manganese monoxide, manganese dioxide, dimanganese trioxide, trimanganese tetroxide, manganese phosphate, manganese hydroxide, manganese oxyhydroxide, manganese oxalate, manganese chloride, manganese carbonate, manganese acetate and hydrates thereof.

4. The method for preparing a cathode material precursor according to claim 1, characterized in that: The iron source includes at least one of metallic iron, ferrous oxide, ferrous oxide, ferric oxide, ferric oxyhydroxide, ferric phosphate, ferric oxalate, ferrous oxalate, ferric chloride, ferrous chloride, ferrous acetate, ferrous carbonate, ferrous hydroxide, ferric hydroxide and hydrates thereof.

5. The method for preparing a cathode material precursor according to claim 1, characterized in that: The phosphorus source includes at least one of phosphoric acid, metaphosphoric acid, phosphorous acid, iron phosphate, manganese phosphate, phosphorus pentoxide and hydrates thereof.

6. The method for preparing a cathode material precursor according to claim 1, characterized in that: The molar ratio of the iron source to the manganese source in step S1 is 1:(1-19).

7. The method for preparing a cathode material precursor according to claim 1, characterized in that: The ratio of the sum of the molar numbers of the iron source and the manganese source to the molar number of the phosphorus source is 1:0.95-1.

10.

8. A positive electrode material of lithium manganese iron phosphate, characterized in that: The raw material for preparing the positive electrode material lithium manganese iron phosphate includes a positive electrode material precursor prepared by the preparation method according to any one of claims 1 to 7.

9. The positive electrode material of claim 8, wherein: The general chemical formula of the lithium manganese iron phosphate is Li 1+u Mn x Me y Fe 1-x-y (PO4) z / C, -0.05≤u≤0.10, 0.50≤x≤0.95, 0≤y≤0.1, 0.95≤z≤1.10; Me is at least one of V, Al, Mg, Ti, Nb, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc.

10. A lithium ion battery, characterized in that: The raw materials for preparing the lithium-ion battery include the modified positive electrode material lithium manganese iron phosphate as described in claim 8 or 9.

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