Method for preparing lithium manganese iron phosphate material, lithium manganese iron phosphate material, and use

Abstract

The present application provides a method for preparing a lithium manganese iron phosphate material, a lithium manganese iron phosphate material, and use. The method comprises the following steps: mixing a manganese source, an iron source, and a solvent to give a mixed liquid, removing the solvent from the mixed liquid, and calcining the residue to give an oxide precursor; and mixing a phosphorus source and a lithium source with the oxide precursor and sintering the mixture to give the lithium manganese iron phosphate material. In the method of the present application, an oxide precursor containing manganese and iron is prepared first, so that manganese and iron are mixed at an atomic level, and the lithium manganese iron phosphate material is then prepared. As a result, the process of preparing lithium manganese iron phosphate is simplified, and the elements manganese and iron in the prepared lithium manganese iron phosphate material are mixed at an atomic level, thereby improving the cycling performance of the lithium manganese iron phosphate material.

Description

A method for preparing lithium manganese iron phosphate materials, lithium manganese iron phosphate materials and their applications Technical Field

[0001] This application belongs to the field of battery technology and relates to a method for preparing lithium manganese iron phosphate material, lithium manganese iron phosphate material and its application. Background Technology

[0002] Lithium-ion batteries have become one of the most popular energy storage solutions due to their high energy density, long lifespan, and environmental friendliness. LiMn x Fe 1-x Lithium manganese iron phosphate (LMFP) has attracted widespread attention in recent years as a cathode material for lithium-ion batteries. Compared with traditional lithium-ion battery cathode materials, LMFP stands out due to its unique electrochemical properties, high safety, and low cost. In particular, its high operating voltage and good thermal stability make LMFP an ideal material for electric vehicles and large-scale energy storage.

[0003] Currently, the main commercial methods for preparing LMFPs are solid-state methods and co-precipitation methods. However, these methods often involve complex processes and high production costs. Therefore, developing simpler and lower-cost synthesis methods is key to realizing the large-scale application of LMFP materials. Furthermore, achieving atomic-level mixing of manganese and iron in the material has a positive effect on improving crystallinity and promoting electron and lithium-ion transport, thereby enhancing the material's electrochemical performance. However, atomic-level mixing places high demands on the preparation method and presents significant technological barriers.

[0004] Based on the above research, there is a need to provide a method for preparing lithium manganese iron phosphate (LMFP) materials. The method is simple and can achieve atomic-level mixing of manganese and iron elements in LMFP.

[0005] Summary of the Invention

[0006] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] This application provides a method for preparing lithium manganese iron phosphate (LMP) materials, LMP materials, and their applications. The method first prepares an oxide precursor containing manganese and iron to achieve atomic-level mixing of manganese and iron, and then prepares LMP materials together with other raw materials. This simplifies the preparation process of LMP materials, and the manganese and iron elements in the prepared LMP materials can achieve atomic-level mixing, thereby improving the cycle performance of LMP materials.

[0008] In a first aspect, this application provides a method for preparing lithium manganese iron phosphate materials, the method comprising the following steps:

[0009] (1) A manganese source, an iron source and a solvent are mixed, and the mixture obtained by removing the solvent is calcined to obtain an oxide precursor;

[0010] (2) The phosphorus source, lithium source and oxide precursor described in step (1) are mixed and sintered to obtain the lithium manganese iron phosphate material.

[0011] This application prepares a manganese and iron oxide precursor by first fully dispersing manganese and iron sources in a solvent, then removing the solvent and calcining it. This achieves atomic-level mixing of manganese and iron elements. The manganese and iron oxide precursor is then solid-state mixed with phosphorus and lithium sources and sintered to prepare lithium manganese iron phosphate material. Therefore, the method described in this application differs from co-precipitation and traditional solid-state mixing methods. It not only simplifies the preparation process but also enables atomic-level mixing of manganese and iron elements, thereby improving the cycle performance of the battery.

[0012] In one embodiment, the solvent removal method in step (1) includes spray drying.

[0013] This application employs a spray drying method that promotes atomic-level mixing of iron and manganese, thereby obtaining a lithium iron phosphate cathode material with a more stable structure and stronger ion and electron transport capabilities.

[0014] Optionally, the inlet air temperature of the spray dryer is 200-240℃, for example, 200℃, 210℃, 220℃, 230℃ or 240℃, and the outlet air temperature is 95-120℃, for example, 95℃, 100℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] In one embodiment, a doped metal source is also incorporated during the mixing process described in step (1).

[0016] In this application, a doped metal source is added when preparing the oxide precursor, which can further improve the performance of lithium manganese iron phosphate material. Moreover, compared with the doping in step (2) or the traditional doping method, the doping in this application can achieve more uniform doping.

[0017] Optionally, the doped metal source includes any one or a combination of at least two of magnesium, aluminum, zinc, titanium, copper, or nickel sources.

[0018] Optionally, the molar ratio of manganese ions in the manganese source, iron ions in the iron source, and dopant ions in the dopant source is (2-9):(1-8):(0.05-0.5), for example, it can be 2:8:0.05, 5:5:0.1, 7:3:0.3 or 9:1:0.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] In one embodiment, the calcination temperature in step (1) is 750-950°C, for example, it can be 750°C, 800°C, 850°C, 900°C or 950°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Optionally, the calcination time in step (1) is 1-3 hours, for example, it can be 1 hour, 2 hours or 3 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] In one embodiment, the total metal ion concentration in the mixture in step (1) is 0.5-2 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] The total metal ion concentration obtained by mixing in step (1) of this application will affect the spray drying effect and thus affect the degree of atomic mixing.

[0023] Optionally, the iron source in step (1) includes a ferrous iron source.

[0024] Optionally, the ferrous source in step (1) includes ferrous chloride.

[0025] Optionally, the manganese source in step (1) includes manganese chloride.

[0026] This application uses inexpensive ferrous chloride and manganese chloride as raw materials.

[0027] In one embodiment, a carbon source is also incorporated during the mixing process described in step (2).

[0028] Optionally, the amount of carbon source added is 5-15 wt% of the total mass of manganese source and iron source in step (1), for example, it can be 5 wt%, 10 wt% or 15 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] In one embodiment, the molar ratio of lithium ions in the lithium source to the total molar amount of manganese ions and iron ions in the oxide precursor in step (2) is (1.01-1.04):1, for example, it can be 1.01:1, 1.02:1, 1.03:1 or 1.04:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Optionally, the lithium source and phosphorus source in step (2) are both lithium dihydrogen phosphate.

[0031] Optionally, the sintering temperature in step (2) is 600-700℃, for example, 600℃, 650℃, or 700℃, and the time is 8-12h, for example, 8h, 10h, or 12h, and the atmosphere includes a protective gas.

[0032] Optionally, the protective gas includes nitrogen.

[0033] As an optional technical solution to the method described in this application, the method includes the following steps:

[0034] (1) The manganese source, iron source, doped metal source and solvent are mixed, and the mixture obtained by mixing has a total metal ion concentration of 0.5-2 mol / L. The mixture is spray-dried and then calcined at 750-950℃ for 1-3 h to obtain the oxide precursor.

[0035] The inlet air temperature of the spray dryer is 200-240℃, and the outlet air temperature is 95-120℃.

[0036] The molar ratio of manganese ions in the manganese source, iron ions in the iron source, and dopant ions in the dopant source is (2-9):(1-8):(0.05-0.5).

[0037] (2) The phosphorus source, lithium source, carbon source and the oxide precursor described in step (1) are mixed and then sintered in a protective gas at a temperature of 600-700°C for 8-12 hours to obtain the lithium manganese iron phosphate material.

[0038] The amount of carbon source added is 5-15 wt% of the total mass of the manganese and iron sources in step (1).

[0039] Secondly, this application provides a lithium manganese iron phosphate material, which is prepared by the method described in any one of the first aspects.

[0040] Secondly, this application provides a lithium-ion battery comprising the lithium manganese iron phosphate material as described in the second aspect.

[0041] Compared with related technologies, this application has the following advantages:

[0042] (1) The process flow of this application is simple, eliminating the sand milling step in the traditional solid phase method and the coprecipitation step in the coprecipitation method. It takes less time, is simple, and has low process cost.

[0043] (2) The method described in this application can achieve atomic-level mixing of manganese and iron elements. After calcination, a more stable structure and stronger ion and electron transport capability of lithium manganese iron phosphate material can be obtained, which can improve the cycle performance of lithium manganese iron phosphate material.

[0044] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0045] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0046] Figure 1 is a SEM image of the lithium manganese iron phosphate material obtained in Example 1 of this application. Detailed Implementation

[0047] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0048] Example 1

[0049] This embodiment provides a method for preparing lithium manganese iron phosphate materials, the method comprising the following steps:

[0050] (1) Manganese chloride, ferrous chloride, magnesium chloride, and water were mixed, and the resulting mixture was spray-dried and then calcined at 850°C for 2 hours to obtain an oxide precursor (chemical formula: Mn). 0.6 Fe 0.4 Mg 0.01 O);

[0051] The inlet air temperature of the spray dryer is 220°C, and the outlet air temperature is 100°C.

[0052] The total metal ion concentration of the mixture is 1 mol / L, wherein the molar ratio of manganese ions, iron ions and magnesium ions is 6:4:0.1;

[0053] (2) Lithium dihydrogen phosphate, the oxide precursor described in step (1) and glucose are mixed and then sintered in nitrogen at 650°C for 10 hours to obtain the lithium manganese iron phosphate material. The SEM image of the lithium manganese iron phosphate material is shown in Figure 1.

[0054] The molar ratio of Li in the lithium dihydrogen phosphate to Mn+Fe in the oxide precursor is 1.02:1; the amount of glucose added is 10 wt% of the total mass of manganese chloride and ferrous chloride in step (1).

[0055] Example 2

[0056] This embodiment provides a method for preparing lithium manganese iron phosphate materials, the method comprising the following steps:

[0057] (1) Manganese chloride, ferrous chloride, magnesium chloride and water were mixed, and the resulting mixture was spray-dried and then calcined at 750°C for 3 hours to obtain an oxide precursor (chemical formula: Mn). 0.8 Fe 0.2 Mg 0.05 O);

[0058] The inlet air temperature of the spray dryer is 240°C, and the outlet air temperature is 120°C.

[0059] The total metal ion concentration of the mixture is 2 mol / L, wherein the molar ratio of manganese ions, iron ions and magnesium ions is 8:2:0.5;

[0060] (2) Lithium dihydrogen phosphate, the oxide precursor described in step (1) and glucose are mixed and then sintered in nitrogen at 700°C for 8 hours to obtain the lithium manganese iron phosphate material.

[0061] The molar ratio of Li in the lithium dihydrogen phosphate to Mn+Fe in the oxide precursor is 1.04:1; the amount of glucose added is 5 wt% of the total mass of manganese chloride and ferrous chloride in step (1).

[0062] Example 3

[0063] This embodiment provides a method for preparing lithium manganese iron phosphate materials, the method comprising the following steps:

[0064] (1) Manganese chloride, ferrous chloride, magnesium chloride, and water were mixed, and the resulting mixture was spray-dried and then calcined at 950°C for 1 hour to obtain an oxide precursor (chemical formula: Mn). 0.4 Fe 0.6 Mg 0.005 O);

[0065] The inlet air temperature of the spray dryer is 200°C, and the outlet air temperature is 95°C.

[0066] The total metal ion concentration of the mixture is 0.5 mol / L, wherein the molar ratio of manganese ions, iron ions and magnesium ions is 4:6:0.05;

[0067] (2) Lithium dihydrogen phosphate, the oxide precursor described in step (1) and glucose are mixed and then sintered in nitrogen at 600°C for 12 hours to obtain the lithium manganese iron phosphate material.

[0068] The molar ratio of Li in the lithium dihydrogen phosphate to Mn+Fe in the oxide precursor is 1.02:1; the amount of glucose added is 15 wt% of the total mass of manganese chloride and ferrous chloride in step (1).

[0069] Example 4

[0070] This embodiment provides a method for preparing lithium manganese iron phosphate material. The method is the same as in Example 1 except that magnesium chloride is not added in step (1) and magnesium chloride is added during mixing in step (2).

[0071] In step (2), after adding magnesium chloride, the molar ratio of manganese ions, iron ions and magnesium ions in the system is 6:4:0.1.

[0072] Example 5

[0073] This embodiment provides a method for preparing lithium manganese iron phosphate material. Except for step (1) where magnesium chloride is not added, the method is the same as in Example 1.

[0074] Example 6

[0075] This embodiment provides a method for preparing lithium manganese iron phosphate material. The method is the same as in Example 1 except that in step (1), spray drying is not performed, but the mixture in step (1) is stirred and evaporated at 90°C to remove water.

[0076] Example 7

[0077] This embodiment provides a method for preparing lithium manganese iron phosphate material. Except for the concentration of the mixture in step (1) being 5 mol / L, the method is the same as in Example 1.

[0078] Example 8

[0079] This embodiment provides a method for preparing lithium manganese iron phosphate material. Except for the concentration of the mixture in step (1) being 0.1 mol / L, the method is the same as in Example 1.

[0080] Comparative Example 1

[0081] This comparative example provides a method for preparing lithium manganese iron phosphate material, which is the same as that in Example 1 except that step (1) is not calcined.

[0082] Comparative Example 2

[0083] This comparative example provides a method for preparing lithium manganese iron phosphate materials, the method comprising the following steps:

[0084] Manganese chloride, ferrous chloride, magnesium chloride, lithium dihydrogen phosphate and glucose were mixed and then sintered in nitrogen at 650°C for 10 hours to obtain the lithium manganese iron phosphate material.

[0085] In the mixture obtained by mixing, the molar ratio of Li to Mn+Fe is 1.02:1, the molar ratio of manganese ions, iron ions and magnesium ions is 6:4:0.1, and the amount of glucose added is 10wt% of the total mass of manganese chloride and ferrous chloride.

[0086] The lithium manganese iron phosphate material prepared in the above examples and comparative examples was used to prepare a positive electrode sheet, which was then used with a lithium metal sheet, a polypropylene separator, and a lithium hexafluorophosphate electrolyte to prepare a lithium-ion battery. The electrochemical performance of the lithium-ion battery was then tested. The charge and discharge conditions were as follows: at a temperature of 25°C, the battery was first charged at a constant current of 0.1C to a voltage of 4.5V, then charged at a constant voltage of 4.5V to a current of 0.05C, and then discharged at a constant current of 0.1C to a voltage of 2.5V. This constituted one charge and discharge cycle at a rate of 0.1C. Then, a second and third charge and discharge cycle were performed at rates of 0.2C and 0.5C, respectively, to fully activate the battery. After that, the battery was charged and discharged at a rate of 1C for 50 cycles, and the discharge capacity after 50 cycles was measured to obtain the capacity retention rate.

[0087] The test results are shown in Table 1:

[0088] Table 1

[0089] As can be seen from Table 1:

[0090] The method described in this application can improve the uniformity of manganese and iron mixing in lithium manganese iron phosphate materials, thereby improving the structural stability and other properties of lithium manganese iron phosphate materials, and thus significantly improving battery cycle performance. As shown in Example 1 and Comparative Example 1, the two calcinations in this application can improve the structural stability of the material and further improve cycle performance. As shown in Example 1 and Comparative Example 2, compared with the traditional solid-phase synthesis method, this application can achieve atomic-level mixing of manganese and iron elements, resulting in lithium manganese iron phosphate materials with excellent cycle performance. As shown in Example 1 and Examples 4-5, the addition of the dopant source and the timing of its addition can further improve the stability of lithium manganese iron phosphate materials. As shown in Example 1 and Example 6, spray drying in this application can promote atomic-level mixing of iron and manganese elements, improving the stability of lithium manganese iron phosphate materials. As shown in Example 1 and Examples 7-8, the concentration of the spray-dried mixture affects the degree of mixing of iron and manganese elements, thereby affecting the cycle performance of lithium manganese iron phosphate materials.

[0091] In summary, this application provides a method for preparing lithium manganese iron phosphate (LFP) materials, LFP materials, and their applications. The method first prepares an oxide precursor containing manganese and iron, enabling atomic-level mixing of manganese and iron, and then prepares LFP materials. This simplifies the preparation process of LFP materials, and the manganese and iron elements in the prepared LFP materials can be atomically mixed, thereby improving the cycle performance of LFP materials.

[0092] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for preparing a lithium manganese iron phosphate material, comprising the following steps: (1) mixing a manganese source, an iron source and a solvent, and calcining the mixture after removing the solvent to obtain an oxide precursor; (2) mixing a phosphorus source, a lithium source and the oxide precursor of step (1) and sintering to obtain the lithium manganese iron phosphate material.

2. The method of claim 1, wherein, The removing of the solvent in step (1) comprises spray drying. Optionally, the inlet air temperature of the spray drying is 200-240℃, and the outlet air temperature is 95-120℃.

3. The method of claim 1 or 2, wherein, Optionally, the mixing in step (1) further comprises mixing a doping metal source. Optionally, the doping metal source comprises any one or a combination of at least two of a magnesium source, an aluminum source, a zinc source, a titanium source, a copper source or a nickel source. Optionally, the molar ratio of manganese ions in the manganese source, iron ions in the iron source and doping ions in the doping source is (2-9) : (1-8) : (0.05-0.5).

4. The method according to any one of claims 1 to 3, wherein, The calcining in step (1) is performed at a temperature of 750-950℃. Optionally, the calcining in step (1) is performed for 1-3h.

5. The method according to any one of claims 1 to 4, wherein, The total metal ion concentration in the mixture in step (1) is 0.5-2mol / L. Optionally, the iron source in step (1) comprises a ferrous source. Optionally, the ferrous source in step (1) comprises ferrous chloride. Optionally, the manganese source in step (1) comprises manganese chloride.

6. The method according to any one of claims 1 to 5, wherein, Optionally, the mixing in step (2) further comprises mixing a carbon source. Optionally, the carbon source is added in an amount of 5-15wt% of the total mass of the manganese source and the iron source in step (1).

7. The method according to any one of claims 1 to 6, wherein, The molar ratio of lithium ions in the lithium source to the total molar amount of manganese ions and iron ions in the oxide precursor in step (2) is (1.01-1.04) :

1. Optionally, the lithium source and the phosphorus source in step (2) are both lithium dihydrogen phosphate. Optionally, the sintering in step (2) is performed at a temperature of 600-700℃ for 8-12h in a protective gas atmosphere. 8.The method of any one of claims 1-7, comprising the following steps: (1) mixing a manganese source, an iron source, a doping metal source and a solvent, and spray drying the mixture to obtain a mixture with a total metal ion concentration of 0.5-2mol / L, and then calcining at 750-950℃ for 1-3h to obtain an oxide precursor; the inlet air temperature of the spray drying is 200-240℃, and the outlet air temperature is 95-120℃; the molar ratio of manganese ions in the manganese source, iron ions in the iron source and doping ions in the doping source is (2-9) : (1-8) : (0.05-0.5) ; (2) mixing a phosphorus source, a lithium source, a carbon source and the oxide precursor of step (1), and then sintering at a temperature of 600-700℃ for 8-12h in a protective gas atmosphere to obtain the lithium manganese iron phosphate material; the carbon source is added in an amount of 5-15wt% of the total mass of the manganese source and the iron source in step (1).

9. A lithium iron manganese phosphate material, wherein, The lithium manganese iron phosphate material is prepared by the method of any one of claims 1-8.

10. A lithium-ion battery, wherein, The lithium ion battery comprises the lithium manganese iron phosphate material of claim 9.

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