A preparation method of sodium manganese iron vanadium phosphate positive electrode material

Abstract

The present invention discloses a method for preparing a sodium manganese ferrovanadium phosphate material for a sodium battery positive electrode, comprising the following steps: S1. Preparing a hydrogen phosphate solution and a manganous salt solution. S2. Adding the hydrogen phosphate solution to the manganous salt solution to react to obtain a hydrogen manganese phosphate crystal nucleus slurry. S3. Filtering and washing the hydrogen manganese phosphate crystal nucleus slurry, adding water to the hydrogen manganese phosphate material to form a slurry and heating it to 85-95°C, then adding a ferrous source and a phosphate salt solution, respectively, to react to obtain a hydrogen manganese phosphate slurry. S4. Filtering, washing, and drying the hydrogen manganese phosphate slurry, then adding water to form a slurry, adding phosphoric acid, and heating it to 90-100°C to react to obtain a ferromanganese phosphate compound precipitate. The precipitate is filtered, washed, and dried to obtain the ferromanganese phosphate material. The present invention utilizes a co-precipitation method and high-temperature sintering to prepare the sodium manganese ferrovanadium phosphate product, which has the advantages of a short and simple process flow, requiring only a single sintering step, and low energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy and sodium batteries, and in particular to a method for preparing a sodium battery positive electrode manganese iron vanadium sodium phosphate material. Background Art

[0002] Compared with lithium-ion batteries, sodium-ion batteries have attracted widespread attention due to their advantages of being environmentally friendly, safe, low cost, low temperature and good rate performance. Polyanion sodium cathode materials, especially phosphate-based sodium cathode materials, have gradually become the focus of attention due to their advantages of low cost, short process flow, relatively high energy density, safety and non-toxicity. In the sodium manganese iron vanadium phosphate material, the introduction of manganese element increases the operating voltage, thereby improving the energy density of the sodium battery; the addition of iron element reduces the band gap width of the material, improves the electronic conductivity of the material, and also improves the stability of the material. The addition of vanadium element increases the unit cell volume, makes the sodium ion channel larger, and improves the ionic conductivity of the sodium ion; in addition, the introduction of iron and vanadium elements also inhibits manganese dissolution, alleviates the Jahn-Taylor effect, and improves the rate performance and cycle life of the sodium ion battery. CN117673330A discloses a method for preparing sodium manganese iron pyrophosphate cathode material. In this patent application, a phosphorus source, a manganese source, an iron source I, and a vanadium source are first pre-reacted with a reducing agent (such as ascorbic acid or lactic acid) to produce a phosphorus-manganese slurry. This slurry is then mixed with a sodium source, a carbon source, and an iron source II through dispersed ball milling, sand milling, spray drying, and subsequent sintering, roller pressing, secondary sintering, and crushing to produce vanadium-doped sodium manganese ferrophosphate. The preparation process in this patent application is long and complex, requiring two sintering steps, resulting in high energy consumption and hindering industrialization. Furthermore, the resulting vanadium-doped sodium manganese ferrophosphate product has a low discharge capacity of only 90-110 mAh / g. CN109659525A discloses a method for preparing a sodium manganese ferrophosphate composite positive electrode material. This patent application describes coaxial electrospinning using a sodium source, a spinning solution composed of a sodium source, an iron source, a manganese source, a phosphoric acid source, a fluorine source, a chelating agent, and a polymer as the outer axis, and an oil-based spinning solution as the inner axis. The process then extracts and removes the oil phase, followed by drying to obtain a hollow nanofiber precursor. This process is then heat-treated in a non-oxidizing atmosphere and cooled to obtain carbon-coated sodium manganese iron fluorophosphate. However, this method requires the use of a chelating agent and a polymer, and the fluorine source is highly corrosive to equipment and pipelines. Furthermore, the electrospinning process has low production capacity, making it difficult to industrialize and commercialize. Summary of the Invention

[0003] The present invention aims to solve one of the technical problems existing in the production and preparation process of the existing sodium battery positive electrode material. The present invention provides a method for preparing sodium manganese iron vanadium phosphate positive electrode material.

[0004] A method for preparing sodium manganese iron vanadium phosphate positive electrode material comprises the following steps:

[0005] S1. Prepare hydrogen phosphate solution and manganous salt solution.

[0006] S2. Adding a hydrogen phosphate solution into the reactor as a primer, and then slowly adding a manganous salt solution into the reactor at room temperature. After reacting for a period of time, a manganese hydrogen phosphate crystal nucleus slurry is obtained.

[0007] S3. The manganese hydrogen phosphate crystal nucleus slurry is filtered and washed, and the washed manganese hydrogen phosphate material is slurried with water and added into a reactor. When the temperature is raised to 85-95° C., a ferrous source and a phosphate solution are added into the reactor simultaneously. After reacting for a period of time, a manganese hydrogen phosphate slurry is obtained.

[0008] S4. The ferromanganese hydrogen phosphate slurry is filtered, washed, and dried. The dried slurry is then slurried with water, phosphoric acid is added, and the temperature is raised to 90-100° C. and reacted for a period of time to obtain a ferromanganese phosphate compound precipitate. The precipitate is filtered, washed, and dried to obtain a ferromanganese phosphate material.

[0009] S5. Add the manganese ferrophosphate material into a mixing crusher for mixing and crushing. After crushing to a certain particle size, add a vanadium source, a sodium source and a carbon source without adding water or any other solvent, and crush to a target particle size.

[0010] S6. The obtained dry powder is sintered at high temperature in a rotary kiln to obtain the desired sodium manganese iron vanadium phosphate product.

[0011] Preferably, in step S1, the hydrogen phosphate is at least one of sodium monohydrogen phosphate and sodium dihydrogen phosphate; and the manganous salt is at least one of manganese sulfate and manganese chloride.

[0012] Preferably, the stirring speed of the reactor in step S2 is 50-200 rpm, the manganous salt solution is added for 5-8 hours, the reaction time after the manganous salt solution is added is 30-60 minutes, and the molar ratio of manganous salt to phosphorus in hydrogen phosphate is 1:1.

[0013] Preferably, the ferrous source in step S3 is at least one of ferrous sulfate, ferrous chloride, and ferrous nitrate; the phosphate salt is at least one of monoammonium phosphate and diammonium phosphate, and the molar ratio of iron in the ferrous source to the manganese salt in S1 and the iron, manganese, and phosphorus in the phosphate salt in S3 is 1:8:1.

[0014] Preferably, in step S3, the conductivity of the washing water during slurry washing is less than 1000 us / cm, the stirring speed of the reactor is 50-200 rpm, the addition time of the ferrous source and the phosphate solution is 5-8 hours, and the reaction time after the addition of the ferrous source and the phosphate solution is 3-5 hours.

[0015] Preferably, during slurry washing in step S4, the conductivity of the washing water is less than 800 μS / cm, the drying temperature is 120° C., the drying time is 3 hours, the phosphoric acid has a mass concentration of 40-85%, the stirring speed of the reactor is 50-200 rpm, the phosphoric acid is added for 5-8 hours, and the reaction time after the addition of phosphoric acid is 3-5 hours.

[0016] Preferably, the vanadium source in step S5 is at least one of vanadyl sulfate, vanadium pentoxide, and vanadium chloride; the sodium source is at least one of sodium carbonate, sodium phosphate, monosodium phosphate, and disodium phosphate; and the carbon source is at least one of fructose, sucrose, and glucose.

[0017] Preferably, in step S5, the stirring speed is 500-1000 rpm, the crushing disk speed is 2000-5000 rpm, the crushed particle size of the manganese iron phosphate is 100-300 nm, and the crushed particle size after adding the vanadium source, sodium source and carbon source is 150-450 nm.

[0018] Preferably, in step S6, the rotary frequency of the rotary kiln is 30 Hz, the temperature of the heating section is 150-600° C., the temperature of the constant temperature section is 800-1000° C., the temperature of the cooling section is 200-300° C., and the sintering time is 12-20 h.

[0019] Advantages of the present invention: The present invention adopts co-precipitation method and high-temperature sintering to prepare sodium manganese iron vanadium phosphate product, which has the advantages of short process flow, simple process, only one sintering required, low energy consumption, etc., and the prepared sodium manganese iron vanadium phosphate product has the characteristics of high compaction density, high discharge capacity and high energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the XRD pattern of the sodium manganese iron vanadium phosphate material prepared in Example 3 of the present invention;

[0021] Figure 2 This is an SEM image of the sodium manganese iron vanadium phosphate material prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0022] 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. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0023] <Example 1>

[0024] 1. Prepare 500 L of 1.2 mol / L sodium dihydrogen phosphate solution and 400 L of 1.5 mol / L manganous sulfate solution.

[0025] 2. Sodium dihydrogen phosphate solution was added to the reactor as a base liquid. The reactor was stirred at 100 rpm. Then, manganous sulfate solution was slowly added to the reactor at room temperature. The addition time was 6 hours. The reaction was completed for 30 minutes to obtain manganese hydrogen phosphate crystal nucleus slurry.

[0026] 3. The slurry is filtered and washed. The washed manganese hydrogen phosphate material is slurried with water and added to the reactor. When the temperature is raised to 85-95°C, 75 L of 1.0 mol / L ferrous sulfate solution and 50 L of 1.5 mol / L ammonium dihydrogen phosphate solution are added to the reactor simultaneously. The addition time is 5 hours. After reacting for 3 hours, hydrogen ferrous manganese phosphate slurry is obtained.

[0027] 4. The slurry is filtered and washed until the conductivity of the washing water is less than 600us / cm, and then dried at 120℃ for 3h. The dried slurry is then slurried with water, and 50kg of 40% phosphoric acid is added for 5h. The temperature is raised to 90-100℃ and reacted for 3h to obtain an iron-manganese phosphate compound precipitate. The precipitate is filtered, washed, and dried to obtain an iron-manganese phosphate material.

[0028] 5. Add the ferromanganese phosphate material to the mixing crusher and stir and crush it at a stirring speed of 500-1000rpm and a crushing disk speed of 2000-5000rpm. The ferromanganese phosphate is crushed to a particle size of 150nm. Add 1.5kg of vanadium pentoxide, 105kg of sodium carbonate, and 5.5kg of sucrose. Do not add water or any other solvents and crush it to a particle size of 200nm.

[0029] 6. The obtained dry powder is sintered at high temperature in a rotary kiln with a rotation frequency of 30 Hz, a temperature of 150-600°C in the heating section, a temperature of 850°C in the constant temperature section, a temperature of 200-300°C in the cooling section, and a sintering time of 17 hours to obtain the desired sodium manganese iron vanadium phosphate product.

[0030] <Example 2>

[0031] 1. Prepare 1000 L of 1.2 mol / L sodium dihydrogen phosphate solution and 800 L of 1.5 mol / L manganous sulfate solution.

[0032] 2. Sodium dihydrogen phosphate solution was added to the reactor as a base liquid. The reactor was stirred at 100 rpm. Then, manganous sulfate solution was slowly added to the reactor at room temperature. The addition time was 8 hours. The reaction was completed for 60 minutes to obtain manganese hydrogen phosphate crystal nucleus slurry.

[0033] 3. The slurry is filtered and washed. The washed manganese hydrogen phosphate material is slurried with water and added to the reactor. When the temperature is raised to 85-95°C, 100 L of 1.4 mol / L ferrous sulfate solution and 140 L of 1.0 mol / L ammonium dihydrogen phosphate solution are added to the reactor simultaneously. The addition time is 8 hours. After reacting for 5 hours, hydrogen ferrous manganese phosphate slurry is obtained.

[0034] 4. The slurry is filtered and washed until the conductivity of the washing water is less than 600us / cm, and then dried at 120℃ for 3h. The dried slurry is then slurried with water, and 100kg of 40% phosphoric acid is added for 8h. The temperature is raised to 90-100℃ and the reaction is carried out for 5h to obtain a precipitate of iron-manganese phosphate compound. The precipitate is filtered, washed, and dried to obtain an iron-manganese phosphate material.

[0035] 5. Add the ferromanganese phosphate material to the mixing crusher and stir and crush it at a stirring speed of 500-1000rpm and a crushing disk speed of 2000-5000rpm. The ferromanganese phosphate is crushed to a particle size of 150nm. Add 3kg of vanadium pentoxide, 210kg of sodium carbonate, and 11kg of sucrose. Do not add water or any other solvents and crush it to a particle size of 200nm.

[0036] 6. The obtained dry powder is sintered at high temperature in a rotary kiln with a rotation frequency of 30 Hz, a temperature of 150-600°C in the heating section, a temperature of 850°C in the constant temperature section, a temperature of 200-300°C in the cooling section, and a sintering time of 17 hours to obtain the desired sodium manganese iron vanadium phosphate product.

[0037] <Example 3>

[0038] 1. Prepare 2500 L of 1.2 mol / L sodium dihydrogen phosphate solution and 2000 L of 1.5 mol / L manganous sulfate solution.

[0039] 2. Sodium dihydrogen phosphate solution was added to the reactor as a base solution. The reactor was stirred at 100 rpm. Then, manganous sulfate solution was slowly added to the reactor at room temperature. The addition time was 5 hours. The reaction was completed for 30 minutes to obtain manganese hydrogen phosphate crystal nucleus slurry.

[0040] 3. The slurry is filtered and washed. The washed manganese hydrogen phosphate material is slurried with water and added to the reactor. When the temperature is raised to 85-95°C, 250 L of 1.4 mol / L ferrous sulfate solution and 350 L of 1.0 mol / L ammonium dihydrogen phosphate solution are added to the reactor simultaneously. The addition time is 5 hours. After reacting for 3 hours, hydrogen ferrous manganese phosphate slurry is obtained.

[0041] 4. The slurry is filtered and washed until the conductivity of the washing water is less than 600us / cm, and then dried at 120℃ for 3h. The dried slurry is then slurried with water, and 250kg of 40% phosphoric acid is added for 6h. The temperature is raised to 90-100℃ and the reaction is carried out for 5h to obtain a precipitate of iron-manganese phosphate compound. The precipitate is filtered, washed, and dried to obtain an iron-manganese phosphate material.

[0042] 5. Add the ferromanganese phosphate material to the mixing crusher and stir and crush it at a stirring speed of 500-1000rpm and a crushing disk speed of 2000-5000rpm. The ferromanganese phosphate is crushed to a particle size of 150nm. Add 7.5kg of vanadium pentoxide, 525kg of sodium carbonate, and 27.5kg of sucrose. Do not add water or any other solvents and crush it to a particle size of 200nm.

[0043] 6. The obtained dry powder is sintered at high temperature in a rotary kiln with a rotation frequency of 30 Hz, a temperature of 150-600°C in the heating section, a temperature of 850°C in the constant temperature section, a temperature of 200-300°C in the cooling section, and a sintering time of 17 hours to obtain the desired sodium manganese iron vanadium phosphate product.

[0044] <Comparative Example 1>

[0045] Control Example 1 is identical to steps 1-3 of Example 3, except that step 4 is as follows: the ferromanganese hydrogen phosphate slurry is filtered and washed until the conductivity of the wash water is less than 600 μs / cm, and then dried at 120° C. for 3 hours to obtain a ferromanganese hydrogen phosphate material. The ferromanganese hydrogen phosphate material is then substituted for the ferromanganese phosphate material in step 5, and the subsequent steps are the same as in Example 3.

[0046] <Comparative Example 2>

[0047] Comparative Example 2 was identical to steps 1-3 of Example 3. Step 4 included filtering and washing the manganese ferrohydrogen phosphate slurry until the wash water conductivity was <600 μs / cm, then drying at 120°C for 3 hours to obtain a manganese ferrohydrogen phosphate material. The manganese ferrohydrogen phosphate material was then substituted for the manganese ferrophosphate material in step 5, without adding 7.5 kg of vanadium pentoxide. Subsequent steps were the same as in Example 3 to obtain sodium manganese ferrophosphate.

[0048] The sodium manganese iron vanadium phosphate material obtained in Example 3 was sent for XRD inspection ( Figure 1 ) and SEM ( Figure 2 ).from Figure 1 It can be seen that the material prepared in the embodiment is a pure phase sodium manganese iron vanadium phosphate material. Figure 2 It can be seen that the sodium manganese iron vanadium phosphate material is irregular flake-shaped, and the primary particle size is 300-500nm.

[0049] The sodium manganese iron vanadium phosphate products prepared in Examples 1-3 and Comparative Example 1, and the sodium manganese iron phosphate products prepared in Comparative Example 2 were tested for compaction density. Button-type batteries were then prepared under the same conditions, and their electrical properties were then tested under the same conditions according to conventional methods in the art. The electrical performance test results for Examples 1-3 and Comparative Examples 1-2 are shown in Table 1 below:

[0050]

[0051] As can be seen from Table 1, the sodium manganese iron vanadium phosphate prepared in the examples exhibits excellent compaction and electrical properties. The compaction density of Examples 1-3 is 0.3 g / cc higher than that of Control Examples 1-2. The 0.1C discharge capacity of the samples of Examples 1-3 reaches 145-150 mAh / g, 20-30 mAh / g higher than that of Control Examples 1-2. The prepared sodium manganese iron vanadium phosphate product exhibits high compaction density and high capacity, resulting in a high energy density. Furthermore, the process is simple to operate and is suitable for industrial production.

[0052] The above implementation cases are only for illustrating the technical solutions and features of the present invention, and their purpose is to enable people familiar with the technology to implement them better. They cannot be used to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention are within the scope of protection of the present invention. The ones not described in detail are prior art.

Claims

1. A method for preparing sodium manganese iron vanadium phosphate positive electrode material, characterized in that: The following steps are involved: S1. Prepare hydrogen phosphate solution and manganous salt solution; S2, using a hydrogen phosphate solution as a primer, and then adding a manganous salt solution to the reaction at room temperature to obtain a manganese hydrogen phosphate crystal nucleus slurry; S3, filtering and washing the manganese hydrogen phosphate crystal nucleus slurry, adding water to the washed manganese hydrogen phosphate material to make a slurry, raising the temperature to 85-95° C., and then adding a ferrous source solution and a phosphate solution simultaneously, and reacting to obtain a manganese hydrogen phosphate slurry; S4, the ferromanganese hydrogen phosphate slurry is filtered, washed, and dried, and then water is added to make a slurry after drying, phosphoric acid is added, and the temperature is raised to 90-100° C., the phosphoric acid has a mass concentration of 40%-85% phosphoric acid, the reaction stirring speed is 50-200 rpm, the phosphoric acid is added for 5-8 hours, and the reaction time after the addition of phosphoric acid is 3-5 hours, and the reaction obtains a ferromanganese phosphate compound precipitate, which is filtered, washed, and dried to obtain a ferromanganese phosphate material; S5, stirring and crushing the ferromanganese phosphate material, adding a vanadium source, a sodium source, and a carbon source after crushing, and crushing to a target particle size to obtain a dry powder; S6. The dry powder obtained in S5 is subjected to high-temperature sintering to obtain the desired sodium manganese iron vanadium phosphate product.

2. The method for preparing a sodium-ion positive electrode manganese iron vanadium phosphate material according to claim 1, characterized in that: The hydrogen phosphate in the hydrogen phosphate solution in step S1 is at least one of sodium monohydrogen phosphate and sodium dihydrogen phosphate.

3. The method for preparing a sodium-ion positive electrode manganese iron vanadium phosphate material according to claim 1, characterized in that: The manganous salt in the manganous salt solution in step S1 is at least one of manganous sulfate solution and manganous chloride solution.

4. The method for preparing a sodium-ion positive electrode manganese iron vanadium phosphate material according to claim 1, characterized in that: The stirring speed of the reaction in step S2 is 50-200 rpm, the time for adding the manganous salt solution is 5-8 hours, the reaction time after the addition of the manganous salt solution is 30-60 minutes, and the molar ratio of manganese to phosphorus in the manganous salt solution and the hydrogen phosphate solution is 1:

1.

5. The method for preparing a sodium-electrochemical cathode material of manganese iron vanadium phosphate according to claim 1, characterized in that: The ferrous source in the ferrous source solution in step S3 is at least one of ferrous sulfate, ferrous chloride, and ferrous nitrate; the phosphate salt in the phosphate solution is at least one of monoammonium phosphate and diammonium phosphate, and the molar ratio of iron, manganese, and phosphorus in the ferrous source solution in S3, the manganous salt solution in S1, and the phosphate solution in S3 is 1:8:

1.

6. The method for preparing a sodium-ion positive electrode manganese iron vanadium phosphate material according to claim 1, characterized in that: In step S3, the conductivity of the washing water during slurry washing is less than 1000 us / cm, the reaction stirring speed is 50-200 rpm, the ferrous source solution and the phosphate solution are added for 5-8 hours, and the reaction time after addition is 3-5 hours.

7. The method for preparing a sodium-ion positive electrode manganese iron vanadium phosphate material according to claim 6, characterized in that: During the slurry washing in step S4, the conductivity of the washing water is less than 800 μs / cm, the drying temperature is 120° C., and the drying time is 3 hours.

8. The method for preparing a sodium-ion positive electrode manganese iron vanadium phosphate material according to claim 1, characterized in that: The vanadium source in step S5 is at least one of vanadyl sulfate, vanadium pentoxide, and vanadium chloride; the sodium source is at least one of sodium carbonate, sodium phosphate, monosodium phosphate, and disodium phosphate; and the carbon source is at least one of fructose, sucrose, and glucose.

9. The method for preparing a sodium-ion positive electrode manganese iron vanadium phosphate material according to claim 1, characterized in that: In step S5, the mixture is crushed in a stirring crusher with a stirring speed of 500-1000 rpm and a crushing disk speed of 2000-5000 rpm. The crushed particle size of the manganese iron phosphate is 100-300 nm, and the crushed particle size after adding the vanadium source, sodium source and carbon source is 150-450 nm.

10. The method for preparing a sodium-ion positive electrode manganese iron vanadium phosphate material according to claim 1, characterized in that: In step S6, the dry powder obtained in S5 is sintered at high temperature in a rotary kiln. The rotary frequency of the rotary kiln is 30 Hz, the temperature of the heating section is 150-600°C, the temperature of the constant temperature section is 800-1000°C, the temperature of the cooling section is 200-300°C, and the sintering time is 12-20 hours.

Images