Method for preparing in situ metal doped manganese iron oxalate precursor

Abstract

To provide a method for preparing an in situ metal doped manganese iron oxalate precursor.SOLUTION: Iron source, manganese source, doped metal elements (Mg, Zn, etc.) are weighed according to a stoichiometric ratio, and deionized water is added to the weighed metal to ultrasonically dissolve the weighed metal to obtain a mixed metal solution. The mixed metal solution is added to a prepared oxalic acid solution and subsequently a certain concentration of complexing agent is added to the solution to perform co-precipitation reaction under the protection of inert gas. A resultant suspension of metal doped manganese iron oxalate is recovered and then filtered, washed and dried to obtain a powder of manganese iron oxalate precursor.EFFECT: By using the manganese iron oxalate precursor as the iron and manganese sources, this can effectively avoid the problem of uneven mixing due to the iron and manganese sources. Moreover, lithium manganese iron phosphate synthesized from the manganese iron oxalate precursor after metal doping can significantly improve the electronic conductivity, thereby enhancing the electrochemical properties of lithium manganese iron phosphate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic fine chemicals, and particularly to a method for preparing an iron manganese oxalate precursor with in-situ metal doping.

Background Art

[0002] Lithium-ion batteries have unique advantages such as high operating voltage, no memory effect, high discharge specific capacity, high safety factor, and characteristics such as good cycle stability, light weight, and small size. Therefore, in aspects such as portable electronic devices, industrial production, and the electric vehicle market, they show extensive application value and potential economic benefits. Therefore, as an environmentally friendly and pollution-free new energy source, lithium-ion batteries have attracted increasing attention in recent years.

[0003] Many of the iron sources and manganese sources used in conventional lithium-ion batteries are prone to uneven mixing, and the synthesized materials have low electronic conductivity and poor electrochemical properties, so they cannot meet the usage needs of lithium-ion batteries. In contrast, the present invention proposes a method for preparing an iron manganese oxalate precursor with in-situ metal doping.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the present invention is to solve the problem that many of the iron sources and manganese sources used in conventional lithium-ion batteries are prone to uneven mixing, and the synthesized materials have low electronic conductivity and poor electrochemical properties, so they cannot meet the usage needs of lithium-ion batteries, and to provide a method for preparing an iron manganese oxalate precursor with in-situ metal doping.

Means for Solving the Problems

[0005] To achieve the above object, the present invention provides the following technical means.

[0006] The first aspect of the present invention provides a method for preparing an iron manganese oxalate precursor for in situ metal doping, including the following steps: Step S1: Weigh a certain amount of ferrous salt, manganese salt solid and other doped metal salts according to the stoichiometric ratio, add an appropriate amount of deionized water, dissolve by ultrasonic wave to obtain a metal mixed solution with a concentration of 0.3 - 3.0 mol / L. Step S2: Weigh a certain mass of precipitant and complexing agent according to the molar ratio of 1:1 - 1.5 between the metal mixed solution and the precipitant, add deionized water, dissolve by ultrasonic wave to obtain a mixed solution. The concentration of the precipitant solution is 0.3 - 3.0 mol / L, and the concentration of the complexing agent solution is 0.1 - 1.0 mol / L. Step S3: Add the prepared precipitant and complexing agent solutions to the reaction kettle, seal it, then perform oxygen removal by bubbling, and start heating and stirring. Step S4: After the temperature rises and stabilizes, drop the prepared metal mixed solution into the mixed solution of the precipitant and the complexing agent at a certain flow rate. Step S5: React at a certain temperature for 0.5 - 48 hours under the protection of an inert gas to obtain a suspension of iron manganese oxalate, and Step S6: After the reaction is completed, recover the suspension of iron manganese oxalate from the reaction kettle, and sequentially perform filtration, washing, and drying to obtain iron manganese oxalate precursor powder.

[0007] Preferably, the ferrous salt in S1 includes one or more of ferrous nitrate, ferrous sulfate, ferrous acetate, and ferrous chloride, but is not limited thereto. The ferrous sulfate may be amorphous ferrous sulfate monohydrate or crystalline ferrous sulfate monohydrate.

[0008] Preferably, the manganese salt in S1 includes one or more of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride, but is not limited thereto. The manganese sulfate may be amorphous manganese sulfate monohydrate or crystalline manganese sulfate monohydrate.

[0009] Preferably, other doped metal ions of the S1 include, but are not limited to, Mg and Zn, and include one or more of Co, Ni, Al, Cu, Zr, Cr, and V. The doped metal salt may be an amorphous metal salt or a crystalline metal salt.

[0010] Preferably, the molar ratio of the iron salt to the manganese salt of the S1 is 1:1 to 5, the concentration of the two-metal mixed solution is 0.3 to 3.0 mol / L, the molar ratio of other doped metal elements of the S1 to the manganese element is 1:6 to 120, and the molar ratio to the iron element is 1:4 to 80.

[0011] Preferably, the precipitant of the S2 is an oxalate. Examples of the oxalate include, but are not limited to, one or more of oxalic acid, potassium oxalate, and sodium oxalate.

[0012] Preferably, the molar ratio of the metal mixed solution to the precipitant of the S2 is 1:1 to 1.5, the concentration of the precipitant solution is 0.3 to 3.0 mol / L, and the bubbling gas used in the S3 is one of argon, nitrogen, and helium.

[0013] Preferably, the temperature range of the S4 is 20 to 100 °C, and the dropping flow rate of the precipitant is 0.01 to 1.0 L / min.

[0014] Preferably, the inert gas of the S5 is one of argon, nitrogen, and helium, the reaction temperature is 20 to 100 °C, and the reaction time is 0.5 to 48 hours.

[0015] A second aspect of the present invention provides an in-situ metal-doped manganese iron oxalate precursor prepared by the method described in the first aspect of the present invention.

Advantages of the Invention

[0016] The present invention has at least the following advantageous effects: (1) In the method for preparing an iron manganese oxalate precursor for in-situ metal doping provided by the present invention, an iron manganese oxalate precursor that can be mixed with a lithium source is prepared using a coprecipitation method, and a lithium iron manganese phosphate cathode material is synthesized by a solid-phase method. By using the iron manganese oxalate precursor as the iron source and manganese source as compared with other iron sources and manganese sources, the problem of non-uniform mixing of the iron source and manganese source can be effectively avoided, and the lithium iron manganese phosphate synthesized from the iron manganese oxalate precursor after metal doping can greatly improve the electron conductivity, thereby improving the electrochemical properties of lithium iron manganese phosphate. (2) In the method for preparing an iron manganese oxalate precursor for in-situ metal doping provided by the present invention, oxalate is not likely to introduce impurity phases during the synthesis process of the cathode material, has high crystallinity, strong binding force, helps to stabilize the skeletal structure of the synthesized product, decomposes during the reaction process to release gas, and can suppress the aggregation of particles and the growth of crystal grains. (3) In the method for preparing an iron manganese oxalate precursor for in-situ metal doping provided by the present invention, the obtained product has high purity, uniform powder particle size distribution, stable thermodynamic properties, and not only that, the manufacturing process is simple and reasonable, can be easily mass-produced industrially, has good economic benefits, and is the best choice for raw materials for preparing cathode materials for driving batteries.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0018] The technical means in the embodiments of the present invention will be described in detail below. It should be noted that the described embodiments are only some of the embodiments of the present invention, and it goes without saying that they are not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative activities belong to the protection scope of the present invention.

[0019] As the technical means of the present invention, a method for preparing an iron manganese oxalate precursor by in-situ metal doping, comprising the following steps.

[0020] A method for preparing an iron manganese oxalate precursor by in-situ metal doping is provided, comprising the following steps. S1: According to the stoichiometric ratio, a certain amount of iron salt, manganese salt solid and other doped metal salts (such as Mg, Zn, etc.) are weighed, an appropriate amount of deionized water is added and dissolved by ultrasonic wave to obtain a metal mixed solution with a concentration of 0.3 - 3.0 mol / L.

[0021] S2: According to the molar ratio of the metal mixed solution to the precipitant of 1:1 - 1.5, a certain mass of precipitant and complexing agent are weighed, deionized water is added and dissolved by ultrasonic wave to obtain a mixed solution. The concentration of the precipitant solution is 0.3 - 3.0 mol / L, and the concentration of the complexing agent solution is 0.1 - 1.0 mol / L.

[0022] S3: Add the prepared precipitant and complexing agent solutions to the reaction kettle, seal it, then perform oxygen removal by bubbling, and start heating and stirring.

[0023] S4: After the temperature rises and stabilizes, the prepared metal mixed solution is dropped into the mixed solution of the precipitant and complexing agent at a certain flow rate.

[0024] S5: React at a certain temperature for 0.5 - 48 hours under the protection of an inert gas to obtain a suspension of iron manganese oxalate.

[0025] S6: After the reaction is completed, the suspension of iron manganese oxalate is recovered from the reaction kettle, and filtered, washed, and dried sequentially to obtain iron manganese oxalate precursor powder.

[0026] The iron salt of S1 includes, but is not limited to, one or more of ferrous nitrate, ferrous sulfate, ferrous acetate, and ferrous chloride. The ferrous sulfate may be amorphous hydrated ferrous sulfate or crystalline hydrated ferrous sulfate, and specifically may be one or more of anhydrous ferrous sulfate, ferrous sulfate monohydrate, and ferrous sulfate heptahydrate.

[0027] The manganese salt of S1 includes, but is not limited to, one or more of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride. The manganese sulfate may be amorphous hydrated manganese sulfate or crystalline hydrated manganese sulfate, and specifically may be one or more of anhydrous manganese sulfate, manganese sulfate monohydrate, and manganese sulfate tetrahydrate.

[0028] The other doped metal ions of S1 include Mg and Zn, but are not limited thereto, and include one or more of Co, Ni, Al, Cu, Zr, Cr, and V. The doped metal salt may be an amorphous metal salt or a crystalline metal salt. The magnesium salt may specifically be one or more of anhydrous magnesium sulfate, magnesium acetate, and magnesium sulfate heptahydrate, and the Zn salt may specifically be one or more of anhydrous zinc sulfate, zinc acetate, and zinc sulfate heptahydrate.

[0029] The molar ratio of the iron salt and manganese salt of S1 is 1:1 to 5, and the concentration of the two-metal mixed solution is 0.3 to 3.0 mol / L.

[0030] The molar ratio of the other doped metal element of S1 to the manganese element is 1:6 to 120, and the molar ratio to the iron element is 1:4 to 80.

[0031] The precipitant of S2 is oxalate, and examples of oxalate include, but are not limited to, one or more of oxalic acid, potassium oxalate, and sodium oxalate.

[0032] The precipitant of S2 is one or more of ammonium oxalate, ammonium sulfate, and ammonium chloride.

[0033] Preferably, the molar ratio of the metal mixed solution of S2 to the precipitant is 1:1 to 1.5, and the concentration of the precipitant solution is 0.3 to 3.0 mol / L.

[0034] The bubbling gas used in S3 is one of argon, nitrogen, and helium.

[0035] The temperature range of S4 is 20 to 100 °C, and the dropping flow rate of the precipitant is 0.01 to 1.0 L / min.

[0036] The inert gas in S5 is one of argon, nitrogen, and helium, the reaction temperature is 20 to 100 °C, and the reaction time is 0.5 to 48 hours.

[0037] The present invention prepares a metal mixed solution, an oxalic acid solution, and a complexing agent solution, causes a coprecipitation reaction under the protection of an inert gas, and prepares an in-situ metal-doped manganese iron oxalate precursor powder having stable thermodynamic properties by methods such as filtration, washing, and drying. Other metal ions (such as Mg, Zn, etc.) are in-situ doped into the manganese iron oxalate precursor and used in the synthesis of the lithium manganese iron phosphate cathode material. By overcoming the problems such as poor inherent electron conductivity of lithium manganese iron phosphate and uneven mixing of metal elements, the electrochemical properties are improved.

[0038] Based on the above method, the present invention provides the following partial examples. The raw materials, reagents, or apparatuses used in the following examples can be uniformly obtained commercially or obtained by conventional known methods unless otherwise specified.

Example

[0039] (Example 1) A method for preparing an in-situ metal-doped manganese iron oxalate precursor, the molecular formula is Mn 0.6 Fe 0.38 Mg 0.02 C2O4·2H2O, and includes the following steps.

[0040] Step 1: Weigh 422.58 g of ferrous sulfate heptahydrate, 405.65 g of manganese sulfate monohydrate, and 19.18 g of magnesium sulfate heptahydrate into a beaker according to a molar ratio of 4:6. Add 4 L of deionized water, and stir with ultrasonic waves until the metal salts are completely dissolved to obtain a metal mixed solution with a concentration of 1.0 mol / L, which is prepared for later use.

[0041] Step 2: Weigh 544.62 g of oxalic acid dihydrate and 56.84 g of ammonium oxalate as a complexing agent into a beaker. Add 4 L of deionized water, and stir with ultrasonic waves until oxalic acid dihydrate and ammonium oxalate are completely dissolved to obtain an oxalic acid solution with a concentration of 1.08 mol / L and a complexing agent solution with a concentration of 0.1 mol / L, which are prepared for later use.

[0042] Step 3: Pour the dissolved oxalic acid solution and complexing agent solution into the reaction kettle, start stirring at 400 r / min, and continue to perform oxygen removal by bubbling for 10 minutes under nitrogen gas protection. Set the reaction temperature to 40 °C.

[0043] Step 4: When the temperature stabilizes at 40 °C, slowly drop the metal mixed solution into the reaction kettle storing the oxalic acid solution and complexing agent at a rate of 0.08 L / min. Immediately, a yellow precipitate of iron manganese oxalate is formed in the reaction kettle.

[0044] Step 5: After all the metal mixed solution is dropped into the reaction kettle storing the oxalic acid solution and complexing agent, continue the reaction at 40 °C for 8 hours under nitrogen gas protection to obtain an iron manganese oxalate suspension.

[0045] Step 6: After the reaction is completed, recover all the mixed solution of iron manganese oxalate from the reaction kettle, filter it under reduced pressure, repeatedly wash it with deionized water until the filtrate becomes clear, take out the filter cake, and vacuum dry it at 80 °C for 12 hours to obtain iron manganese oxalate precursor powder.

[0046] (Example 2) A method for preparing an in situ metal-doped iron manganese oxalate precursor, the molecular formula of which is Mn0.6 Fe 0.38 Zn 0.02 With C2O4·2H2O, the following steps are included.

[0047] Step 1: Weigh 422.58 g of ferrous sulfate heptahydrate, 405.65 g of manganese sulfate monohydrate, and 23 g of zinc sulfate heptahydrate into a beaker according to a molar ratio of 4:6. Add 4 L of deionized water and stir with ultrasonic waves until the metal salts are completely dissolved to obtain a metal mixed solution with a concentration of 1.0 mol / L, which is prepared for later use.

[0048] Step 2: Weigh 544.62 g of oxalic acid dihydrate and 56.84 g of ammonium oxalate complexing agent into a beaker. Add 4 L of deionized water and stir with ultrasonic waves until oxalic acid dihydrate and ammonium oxalate are completely dissolved to obtain an oxalic acid solution with a concentration of 1.08 mol / L and a complexing agent solution with a concentration of 0.1 mol / L, which are prepared for later use.

[0049] Step 3: Pour the dissolved oxalic acid solution and complexing agent solution into the reaction kettle, start stirring at 400 r / min, and continue to carry out oxygen removal by bubbling under nitrogen gas protection for 10 minutes. Set the reaction temperature to 40°C.

[0050] Step 4: When the temperature stabilizes at 40°C, slowly drop the metal mixed solution into the reaction kettle storing the oxalic acid solution and complexing agent at a rate of 0.08 L / min. Immediately, a yellow precipitate of manganese iron oxalate is formed in the reaction kettle.

[0051] Step 5: After all the metal mixed solution is dropped into the reaction kettle storing the oxalic acid solution and complexing agent, continue the reaction at 40°C for 8 hours under nitrogen gas protection to obtain a manganese iron oxalate suspension.

[0052] Step 6: After the reaction is completed, recover all the mixed solution of manganese iron oxalate from the reaction kettle, filter it under reduced pressure, repeatedly wash it with deionized water until the filtrate becomes transparent, take out the filter cake, and vacuum dry it at 80°C for 12 hours to obtain manganese iron oxalate precursor powder.

[0053] The product obtained in Example 1 was measured by XRD and SEM, and the results are shown in Figures 1-2.

[0054] The present invention synthesizes lithium iron manganese phosphate using a manganese iron oxalate precursor as a raw material and has the following advantages. First, oxalate is not likely to introduce impurity phases during the synthesis process of the cathode material. Second, the lithium iron manganese phosphate cathode material synthesized from the manganese iron oxalate precursor has high crystallinity, strong binding force, and helps to stabilize the skeletal structure of the synthesis product. Third, during the reaction process of the manganese iron oxalate precursor, it decomposes to release gas, which can suppress the aggregation of particles and the growth of crystal grains.

[0055] The basic principle, main features, and advantages of the present invention have been shown and described above. However, the present invention is not limited to the details of the above exemplary embodiments, and it is obvious to those skilled in the art that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any perspective. Since the scope of the present invention is limited by the claims rather than the above description, all changes within the meaning and scope of the requirements of equivalents falling within the claims are intended to be included in the present invention.

[0056] Although the embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is limited by the appended claims and their equivalents.

Claims

1. A method for preparing an iron manganese oxalate precursor by in-situ metal doping, comprising: Step S1: Weigh a certain amount of iron salt, manganese salt solid and other doped metal salts according to the stoichiometric ratio, add an appropriate amount of deionized water, dissolve by ultrasonic wave to obtain a metal mixed solution with a concentration of 0.3 to 3.0 mol / L; Step S2: Weigh a certain mass of the precipitating agent and complexing agent according to the molar ratio of 1:1 to 1.5 between the metal mixed solution and the precipitating agent, add deionized water, dissolve by ultrasonic wave to obtain a mixed solution, the concentration of the precipitating agent solution is 0.3 to 3.0 mol / L, and the concentration of the complexing agent solution is 0.1 to 1.0 mol / L; Step S3: Add the prepared solutions of the precipitating agent and the complexing agent to a reaction kettle, seal it, then perform oxygen removal by bubbling, and start heating and stirring; Step S4: After the temperature rises and stabilizes, drop the prepared metal mixed solution into the mixed solution of the precipitating agent and the complexing agent at a certain flow rate; Step S5: React at a certain temperature for 0.5 to 48 hours under the protection of an inert gas to obtain a suspension of iron manganese oxalate; Step S6: After the reaction is completed, recover the suspension of iron manganese oxalate from the reaction kettle, and sequentially perform filtration, washing and drying to obtain an iron manganese oxalate precursor powder. A method for preparing an iron manganese oxalate precursor by in-situ metal doping, characterized by comprising the above steps.

2. The iron salt in S1 includes, but is not limited to, one or more of ferrous nitrate, ferrous sulfate, ferrous acetate, and ferrous chloride. The ferrous sulfate may be amorphous ferrous sulfate monohydrate or crystalline ferrous sulfate monohydrate. The method for preparing an iron manganese oxalate precursor by in-situ metal doping according to Claim 1.

3. The manganese salt in S1 includes, but is not limited to, one or more of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride. The manganese sulfate may be amorphous manganese sulfate monohydrate or crystalline manganese sulfate monohydrate. The method for preparing an iron manganese oxalate precursor by in-situ metal doping according to Claim 1.

4. Other doped metal ions of S1 include, but are not limited to, Mg and Zn, and include one or more of Co, Ni, Al, Cu, Zr, Cr, and V. The doped metal salt may be an amorphous metal salt or a crystalline metal salt. The method for preparing an iron manganese oxalate precursor with in-situ metal doping according to claim 1, characterized in that.

5. The molar ratio of the iron salt to the manganese salt of S1 is 1:1 to 5, the concentration of the two-metal mixed solution is 0.3 to 3.0 mol / L, the molar ratio of the other doped metal element of S1 to the manganese element is 1:6 to 120, and the molar ratio to the iron element is 1:4 to 80. The method for preparing an iron manganese oxalate precursor with in-situ metal doping according to claim 1, characterized in that.

6. The precipitant of S2 is an oxalate. Examples of the oxalate include, but are not limited to, one or more of oxalic acid, potassium oxalate, and sodium oxalate. The method for preparing an iron manganese oxalate precursor with in-situ metal doping according to claim 1, characterized in that.

7. The molar ratio of the metal mixed solution of S2 to the precipitant is 1:1 to 1.5, the concentration of the precipitant solution is 0.3 to 3.0 mol / L, and the bubbling gas used in S3 is one of argon, nitrogen, and helium. The method for preparing an iron manganese oxalate precursor with in-situ metal doping according to claim 1, characterized in that.

8. The temperature range of S4 is 20 to 100 °C, and the dropping flow rate of the precipitant is 0.01 to 1.0 L / min. The method for preparing an iron manganese oxalate precursor with in-situ metal doping according to claim 1, characterized in that.

9. The inert gas of S5 is one of argon, nitrogen, and helium, the reaction temperature is 20 to 100 °C, and the reaction time is 0.5 to 48 hours. The method for preparing an iron manganese oxalate precursor with in-situ metal doping according to claim 1, characterized in that.

10. An iron manganese oxalate precursor with in-situ metal doping, characterized in that the iron manganese oxalate precursor is prepared by the method according to any one of claims 1 to 9. An iron manganese oxalate precursor with in-situ metal doping.

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