Preparation method and application of manganese pyrophosphate

Abstract

The invention relates to the technical field of battery positive electrode materials, in particular to a preparation method and application of manganese pyrophosphate. The preparation method of the manganese pyrophosphate comprises the following steps: (a) adding a phosphorus salt solution into a divalent manganese salt solution, and carrying out a mixing reaction; and (b) carrying out suction filtration, drying and calcining on the reaction system after the mixed reaction is finished to obtain the manganese pyrophosphate. According to the preparation method of the manganese pyrophosphate, an oxidizing agent and a non-ionic surface active agent (organic solvent) do not need to be added in the preparation process, so that the preparation method is green, environment-friendly, low in production cost and suitable for large-scale production, the reaction can be carried out at room temperature, the preparation method is simple, the synthesis period is short, and the yield is close to 100%.

Description

Technical Field

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

[0002] LiFePO 4 With its significant advantages such as low cost, high safety and long life, it is widely used in lithium-ion batteries. With the development of social economy, people have put forward requirements for lithium-ion batteries with higher energy density, lower cost and higher safety. 4 With LiFePO 4 Comparable theoretical capacity (~171 mAh / g), but with a higher operating voltage (~4.1 V), which can provide a higher energy density (~700 Wh / kg), which makes LiMnPO 4 Become a new research hotspot.

[0003] The prior art uses manganese-containing inorganic salts, phosphate-containing inorganic salts and non-ionic surfactants dissolved in deionized water, and ammonia water is used to adjust the pH of the reaction to prepare nano manganese pyrophosphate materials. Organic solvents and ammonia water are added to the manganese pyrophosphate prepared by the prior art, which has environmental pollution and wastewater discharge problems and is not suitable for large-scale production.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing manganese pyrophosphate and application thereof. The method for preparing manganese pyrophosphate does not require the addition of an oxidant and a nonionic surfactant, is green and environmentally friendly, has a low production cost, is suitable for large-scale production, has a simple preparation method, a short synthesis cycle, and a yield of nearly 100%.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0007] One aspect of the present invention relates to a method for preparing manganese pyrophosphate, comprising the following steps:

[0008] (a) adding a phosphate solution to a divalent manganese salt solution and performing a mixing reaction;

[0009] (b) filtering, drying and calcining the reaction system after the mixed reaction to obtain the manganese pyrophosphate.

[0010] The method for preparing manganese pyrophosphate does not require the addition of an oxidant and a non-ionic surfactant (organic solvent) during the preparation process, is green and environmentally friendly, has a low production cost, and is suitable for large-scale production. The method can react at room temperature, has a simple preparation method, a short synthesis cycle, and a yield of nearly 100%.

[0011] Another aspect of the present invention also relates to a method for preparing lithium manganese phosphate, including the method for preparing manganese pyrophosphate.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) The preparation method of manganese pyrophosphate provided by the present invention does not require the addition of an oxidant and a nonionic surfactant (organic solvent) during the preparation process, is green and environmentally friendly, has a low production cost, and is suitable for large-scale production. The method can be reacted at room temperature, has a simple preparation method, a short synthesis cycle, and a yield of nearly 100%.

[0014] (2) The method for preparing manganese pyrophosphate provided by the present invention can prepare manganese pyrophosphate with a spherical morphology and a porous structure as a whole. The primary particle size is about 200 nm, the particles are evenly dispersed, and the Mn / P ratio of the manganese pyrophosphate is 1:1, which is convenient for subsequent feeding.

[0015] (3) The method for preparing manganese pyrophosphate provided by the present invention comprises adding a phosphate solution to a divalent manganese salt solution, adjusting the pH of the mixed reaction to 4.0-5.0, and controlling the pH of the reaction solution to allow the divalent manganese salt and the phosphate salt to form an intermediate Mn(PO 3 (OH))·3H 2 O is then calcined to generate Mn 2 P 2 O 7 The valence state of manganese does not change before and after the reaction, so there is no need to add an oxidant; the present invention controls the pH value of the reaction to first prepare Mn(PO 3 (OH))·3H 2 O intermediate is then calcined to generate Mn 2 P 2 O 7 During the calcination process, the crystal water will be removed from the surface of the intermediate, so that the calcined Mn 2 P 2 O 7 The porous structure enables the particles to be evenly dispersed, and the LiMnPO 4 Therefore, there is no need to add non-ionic surfactants in this reaction to regulate the particle morphology and make the particles evenly dispersed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 Mn prepared in the embodiment of the present invention 2 P 2 O 7 SEM images of

[0018] Figure 2 Mn prepared in the embodiment of the present invention 2 P 2 O 7 XRD pattern of

[0019] Figure 3 LiMnPO prepared by combining Example 1 and Example 3 4 XRD pattern of . DETAILED DESCRIPTION

[0020] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0021] One aspect of the present invention relates to a method for preparing manganese pyrophosphate, comprising the following steps:

[0022] (a) adding a phosphate solution to a divalent manganese salt solution and performing a mixing reaction;

[0023] (b) filtering, drying and calcining the reaction system after the mixed reaction to obtain the manganese pyrophosphate.

[0024] The method for preparing manganese pyrophosphate does not require the addition of an oxidant and a non-ionic surfactant (organic solvent) during the preparation process, is green and environmentally friendly, has a low production cost, and is suitable for large-scale production. The method can react at room temperature, has a simple preparation method, a short synthesis cycle, and a yield of nearly 100%.

[0025] The method for preparing manganese pyrophosphate comprises adding a phosphate solution to a divalent manganese salt solution, adjusting the pH of the mixed reaction to 4.0-5.0, and controlling the pH of the reaction solution to allow the divalent manganese salt and the phosphate salt to form an intermediate Mn(PO 3 (OH))·3H 2 O is then calcined to generate Mn 2 P 2 O 7 The valence state of manganese does not change before and after the reaction, so there is no need to add an oxidant; the present invention controls the pH value of the reaction to first prepare Mn(PO 3 (OH))·3H 2 O intermediate is then calcined to generate Mn 2 P 2 O 7 During the calcination process, the crystal water will be removed from the surface of the intermediate, so that the calcined Mn 2 P 2 O 7 The porous structure enables the particles to be evenly dispersed, and the LiMnPO 4 Therefore, there is no need to add non-ionic surfactants in this reaction to regulate the particle morphology and make the particles evenly dispersed.

[0026] The method for preparing manganese pyrophosphate prepares manganese pyrophosphate with a spherical morphology and a porous structure as a whole. The primary particle size is about 200 nm, the particles are evenly dispersed, and the Mn / P ratio of the manganese pyrophosphate is 1:1, which is convenient for subsequent feeding.

[0027] The pH of the divalent manganese source after dissolving in water is about 4.0, and the pH of the phosphate solution is between 6.5 and 7.5. Slowly adding the phosphate solution to the divalent manganese salt solution can break the HPO 4 2- The ionization balance of HPO 4 2- The formation of Mn(PO 3 (OH))·3H 2 O is generated, increasing the yield of manganese pyrophosphate.

[0028] Furthermore, the phosphate salt solution is mainly prepared by mixing phosphoric acid and alkali.

[0029] Furthermore, the pH of the phosphate solution is 6.5-7.5, including but not limited to any point value of 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4 or 7.5 or a range between any two of them.

[0030] Furthermore, the divalent manganese salt includes but is not limited to at least one of manganese sulfate, manganese chloride, manganese acetate or manganese carbonate.

[0031] Furthermore, the pH of the divalent manganese salt solution is 3.8-4.2, including but not limited to any one of 3.8, 3.9, 4.0, 4.1 or 4.2 or a range between any two of them.

[0032] Limiting the pH of phosphate solution and divalent manganese salt solution to a certain range can break the HPO 4 2- The ionization balance of HPO 4 2- The formation of Mn(PO 3 (OH))·3H 2 O is generated, increasing the yield of manganese pyrophosphate.

[0033] The present invention does not specifically limit the type of base, and any base conventional in the art can be used to implement the technical solution of the present invention. In some specific embodiments, the base includes but is not limited to: sodium hydroxide and / or potassium hydroxide.

[0034] Furthermore, the molar ratio of phosphorus in the phosphate solution to manganese in the divalent manganese salt is 1.0 to 1.2: 1, including but not limited to 1.0: 1, 1.1: 1 or 1.2: 1. The feeding amounts of phosphorus and manganese are limited to a certain range, and the Mn / P ratio of the prepared manganese pyrophosphate is close to 1: 1, and the yield of manganese pyrophosphate is high.

[0035] Furthermore, the temperature of the mixed reaction is 20-30° C., including but not limited to any one of 20° C., 22° C., 24° C., 26° C., 28° C. or 30° C. or a range between any two thereof. The mixed reaction can be carried out at room temperature, which can reduce production costs.

[0036] Furthermore, the pH of the mixed reaction is 4.0 to 5.0, including but not limited to any point value of 4.0, 4.2, 4.4, 4.6, 4.8 or 5.0 or any range value between two of them. The mixed reaction is carried out under this pH condition to break the HPO 4 2- The ionization balance of HPO 4 2- The formation of Mn(PO 3 (OH))·3H 2 O is generated, the yield of manganese pyrophosphate is increased, and the generation of Mn 3 (PO 4 ) 2 7H 2 O.

[0037] Furthermore, the mixing reaction time is 55 to 65 minutes, including but not limited to any one of 55 minutes, 57 minutes, 59 minutes, 61 minutes, 63 minutes or 65 minutes or any range between two of them. Performing the mixing reaction within a certain time can ensure that the mixing reaction is fully carried out.

[0038] Furthermore, the calcination temperature is 350-550°C, including but not limited to any point value of 350°C, 380°C, 400°C, 430°C, 450°C, 480°C, 500°C, 530°C or 550°C or any range value between two of them. By controlling the calcination temperature within a certain range, Mn(PO 3 (OH))·3H 2 O in the crystal water, thereby generating Mn 2 P 2 O 7 If the calcination temperature is not within the appropriate range, it may cause Mn(PO 3 (OH))·3H 2 O cannot be completely converted into Mn 2 P 2 O 7 , causing Mn 2 P 2 O 7 The yield is low.

[0039] Furthermore, the calcination time is 1 to 2 hours, including but not limited to any one of 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours, or a range between any two of them.

[0040] Furthermore, the heating rate of the calcination is 5 to 10°C / min, including but not limited to any one of 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min or a range between any two of them.

[0041] The main equations involved in the preparation process of manganese pyrophosphate are as follows:

[0042] H 3 PO 4 +2NaOH → Na 2 HPO 4 +2H 2 O;

[0043] Mn 2+ +HPO4 2- +3H 2 O→Mn(PO3 (OH))·3H 2 O;

[0044] Mn(PO 3 (OH))·3H 2 O→1 / 2Mn 2 P 2 O 7 +7 / 2H 2 O.

[0045] Another aspect of the present invention also relates to a method for preparing lithium manganese phosphate, including the method for preparing manganese pyrophosphate.

[0046] Furthermore, the preparation method of lithium manganese phosphate comprises the following steps:

[0047] ball-milling, spray-drying and calcining the first slurry to obtain the lithium manganese phosphate;

[0048] The first slurry includes: manganese pyrophosphate, a phosphorus source, a lithium source and a carbon source.

[0049] Furthermore, the molar ratio of lithium, manganese and phosphorus in the first slurry is (1.0-1.1):(0.98-1.0):1, including but not limited to 1.0:1.0:1, 1.1:0.99:1 or 1.1:0.98:1.

[0050] Furthermore, the molar ratio of the carbon element in the carbon source to the phosphorus element in the first slurry is 0.05 to 0.07:1, including but not limited to 0.05:1, 0.06:1 or 0.07:1.

[0051] The present invention does not specifically limit the type of phosphorus source, and conventional phosphorus sources in the art can be used to implement the technical solution of the present invention. In some specific embodiments, the phosphorus source includes but is not limited to at least one of sodium dihydrogen phosphate, sodium monohydrogen phosphate or trisodium phosphate.

[0052] The present invention does not specifically limit the type of lithium source, and conventional lithium sources in the art can be used to implement the technical solution of the present invention. In some specific embodiments, the lithium source includes but is not limited to at least one of lithium hydroxide, lithium carbonate or lithium phosphate.

[0053] The present invention does not specifically limit the type of carbon source, and conventional carbon sources in the art can be used to implement the technical solution of the present invention. In some specific embodiments, the carbon source includes but is not limited to: sucrose and / or glucose.

[0054] Furthermore, the particle size of the particles in the slurry after ball milling is ≤400 nm, including but not limited to any point value of 400 nm, 350 nm, 300 nm, 250 nm, 200 nm or 150 nm or a range value between any two of them.

[0055] Furthermore, the solid content of the slurry after ball milling is 30% to 40%, including but not limited to any point value of 30%, 32%, 34%, 36%, 38% or 40% or a range value between any two of them.

[0056] Furthermore, the rotation speed of the ball mill is 300-500 rpm / min, including but not limited to any one of 300 rpm / min, 350 rpm / min, 400 rpm / min, 450 rpm / min or 500 rpm / min or a range between any two of them.

[0057] Furthermore, the ball milling time is 2 to 4 hours, including but not limited to any one of 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours or a range between any two of them.

[0058] Furthermore, the calcination temperature is 750-850°C, including but not limited to any point value of 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C or 850°C or a range value between any two of them.

[0059] Furthermore, the calcination time is 8 to 10 hours, including but not limited to any one of 8 hours, 8.5 hours, 9 hours, 9.5 hours or 10 hours or a range between any two of them.

[0060] Furthermore, the calcination is performed under an inert atmosphere.

[0061] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0062] Example 1

[0063] The method for preparing manganese pyrophosphate provided in this example comprises the following steps:

[0064] Step S1: Dissolve 10.14 g of manganese sulfate in 55 mL of deionized water at room temperature to obtain Mn 2+ Solution A;

[0065] Step S2: 84.47 g of phosphoric acid and 1.89 g of sodium hydroxide were mixed to a pH of 7.00 to obtain a sodium monohydrogen phosphate solution B;

[0066] Step S3: slowly adding solution B into solution A for mixed reaction, wherein the molar ratio of phosphorus element to manganese element is 1.0:1, the reaction temperature is 25°C, the reaction pH is 4.0, and the reaction time is 1h;

[0067] Step S4: The solution after the mixed reaction is filtered, dried and calcined at 550°C for 1 hour at a heating rate of 10°C / min to obtain a porous structure of manganese pyrophosphate (Mn 2 P 2 O 7 ).

[0068] Figure 1 Mn prepared in the embodiment of the present invention 2 P 2 O 7 From the SEM graph, it can be seen that Mn 2 P 2 O 7 The overall porous structure is spherical in shape, the primary particle size is about 200nm, and the particles are dispersed relatively evenly.

[0069] Figure 2 Mn prepared in the embodiment of the present invention 2 P 2 O 7 The XRD pattern of Mn prepared by the above method 2 P 2 O 7 The XRD pattern of the product is consistent with the standard card JCPDS#29-0891, and there is no impurity phase, indicating that the method can prepare Mn with good crystallinity and pure phase. 2 P 2 O 7 .

[0070] Example 2

[0071] The method for preparing manganese pyrophosphate provided in this example comprises the following steps:

[0072] Step S1: Dissolve 11.87 g of manganese chloride in 55 mL of deionized water at room temperature to obtain Mn 2+ Solution A;

[0073] Step S2: 84.47 g of phosphoric acid and 2.96 g of sodium hydroxide were mixed to a pH of 7.50 to obtain a sodium monohydrogen phosphate solution B;

[0074] Step S3: slowly adding solution B into solution A for mixed reaction, wherein the molar ratio of phosphorus element to manganese element is 1.2:1, the reaction temperature is 25°C, the reaction pH is 4.5, and the reaction time is 1h;

[0075] Step S4: The solution after the mixed reaction is filtered, dried and calcined at 550°C for 2h at a heating rate of 10°C / min to obtain a porous structure of manganese pyrophosphate (Mn 2 P 2 O 7 ).

[0076] Example 3

[0077] The method for preparing manganese pyrophosphate provided in this example comprises the following steps:

[0078] Step S1: dissolving manganese chloride in deionized water at room temperature to obtain Mn 2+ Solution A, the pH of solution A is 3.8;

[0079] Step S2: mixing phosphoric acid and sodium hydroxide to obtain a sodium monohydrogen phosphate solution B at a pH of 6.50;

[0080] Step S3: slowly adding solution B into solution A for mixed reaction, wherein the molar ratio of phosphorus element to manganese element is 1.1:1, the reaction temperature is 20° C., the reaction pH is 5.0, and the reaction time is 55 min;

[0081] Step S4: The solution after the mixed reaction is filtered, dried and calcined at 350°C for 1.5h at a heating rate of 5°C / min to obtain a porous manganese pyrophosphate (Mn 2 P 2 O 7 ).

[0082] Example 4

[0083] The method for preparing manganese pyrophosphate provided in this example comprises the following steps:

[0084] Step S1: dissolving manganese acetate in deionized water at room temperature to obtain Mn 2+ Solution A, the pH of solution A is 4.2;

[0085] Step S2: mixing phosphoric acid and sodium hydroxide to obtain a sodium monohydrogen phosphate solution B at a pH of 6.8;

[0086] Step S3: slowly adding solution B into solution A for mixed reaction, wherein the molar ratio of phosphorus element to manganese element is 1.1:1, the reaction temperature is 30° C., the reaction pH is 4.5, and the reaction time is 65 min;

[0087] Step S4: The solution after the mixed reaction is filtered, dried and calcined at 450°C for 2h at a heating rate of 8°C / min to obtain a porous structure of manganese pyrophosphate (Mn 2 P 2 O 7 ).

[0088] Example 5

[0089] This example provides a method for preparing lithium manganese phosphate, comprising the following steps:

[0090] Step S1: 342 g of manganese pyrophosphate (Mn 2 P 2 O 7 ) was mixed with 171.4 g of sodium monohydrogen phosphate, 91 g of lithium carbonate, and 58 g of sucrose in a Li:Mn:P molar ratio of 1.02:0.99:1.0 and a C / P molar ratio of 0.07:1 with deionized water to prepare a slurry with a solid content of 40%, and ball milled at 300 rpm / min for 2 h to obtain slurry D;

[0091] Step S2: After the ball-milled slurry D is spray-dried, 2 After calcination at 850 °C for 9 h in an atmosphere, the mixture was naturally cooled to room temperature to obtain lithium manganese phosphate (LiMnPO 4 ).

[0092] Comparative Example 1

[0093] The method for preparing manganese pyrophosphate provided in this comparative example is different from that in Example 1 in that in step S2, the pH of solution B is adjusted to 4.0.

[0094] Comparative Example 2

[0095] The method for preparing manganese pyrophosphate provided in this comparative example is different from that in Example 1 in that in step S3, the pH of the reaction is 5.3.

[0096] Comparative Example 3

[0097] The method for preparing manganese pyrophosphate provided in this comparative example is different from that in Example 1 in that in step S4, the calcination temperature is 320°C.

[0098] Experimental example

[0099] The manganese pyrophosphate prepared in Examples 1 to 4 and Comparative Examples 1 to 3 is used to prepare lithium manganese phosphate by the preparation method of lithium manganese phosphate provided in Example 5, and the prepared lithium manganese phosphate is respectively made into lithium ion batteries, the specific method is: LiMnPO 4, Super-P, and PVDF were uniformly dispersed in NMP at a mass ratio of 9:0.5:0.5 to obtain an electrode slurry, which was coated on aluminum foil and dried in vacuum at 100°C for 12 hours before slicing to obtain a positive electrode sheet. Using argon as the protective gas, the positive electrode sheet, metal lithium sheet, Celgard2325 separator, and 1M LiPF 6 The CR2032 button cell was assembled with ethylene carbonate / diethyl carbonate electrolyte. The performance of the lithium-ion battery was tested by constant current and constant voltage charging, cut-off voltage 4.5V, cut-off current 20mA; constant current discharge, cut-off voltage 2.5V.

[0100] The performance of the prepared lithium manganese phosphate was tested, and the test results are shown in Table 1.

[0101] Table 1 LiMnPO prepared from different examples and comparative examples 4 First charge and discharge performance

[0102]

[0103] It can be seen from the data in Table 1 that the lithium manganese phosphate material prepared by using the manganese pyrophosphate prepared in the embodiment of the present invention has a higher discharge capacity and first efficiency at 0.1C than the comparative example, indicating that the manganese pyrophosphate prepared in the present invention can be used to prepare lithium manganese phosphate to maximize the performance of LiMnPO 4 Excellent charge and discharge performance.

[0104] Figure 3 LiMnPO prepared by combining Example 1 and Example 3 4 The XRD pattern of LiMnPO prepared by the above method 4 The XRD pattern of the prepared LiMnPO is consistent with the standard card JCPDS#77-01781, and there is no impurity phase, indicating that the method can prepare LiMnPO with good crystallinity and pure phase. 4 .

[0105] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing manganese pyrophosphate, characterized in that: The following steps are involved: (a) adding a phosphate solution to a divalent manganese salt solution and performing a mixing reaction; (b) filtering, drying and calcining the reaction system after the mixed reaction to obtain the manganese pyrophosphate.

2. The method for preparing manganese pyrophosphate according to claim 1, characterized in that: The pH of the phosphate solution is 6.5-7.

5.

3. The method for preparing manganese pyrophosphate according to claim 1, characterized in that: The phosphate salt solution is mainly prepared by mixing phosphoric acid and alkali.

4. The method for preparing manganese pyrophosphate according to claim 3, characterized in that: The alkali includes sodium hydroxide and / or potassium hydroxide.

5. The method for preparing manganese pyrophosphate according to claim 1, characterized in that: The pH of the divalent manganese salt solution is 3.8-4.

2.

6. The method for preparing manganese pyrophosphate according to claim 1, characterized in that: The divalent manganese salt includes at least one of manganese sulfate, manganese chloride, manganese acetate or manganese carbonate.

7. The method for preparing manganese pyrophosphate according to claim 1, characterized in that: The molar ratio of the phosphorus element in the phosphate salt solution to the manganese element in the divalent manganese salt is 1.0-1.2:

1.

8. The method for preparing manganese pyrophosphate according to claim 1, characterized in that: Includes at least one of the following technical features: (1) The temperature of the mixed reaction is 20 to 30° C.; (2) the pH of the mixed reaction is 4.0 to 5.0; (3) The mixing reaction time is 55 to 65 minutes.

9. The method for preparing manganese pyrophosphate according to claim 1, characterized in that: Include at least one of the following technical features: (1) The calcination temperature is 350-550° C.; (2) the calcination time is 1 to 2 hours; (3) The heating rate of the calcination is 5 to 10°C / min.

10. A method for preparing lithium manganese phosphate, characterized in that: A method for preparing manganese pyrophosphate comprising the steps of any one of claims 1 to 9.

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