A method for preparing high-compact lithium iron manganese phosphate material by coating large particles with small particles

Abstract

A method for preparing high-compact lithium iron manganese phosphate material by coating large particles with small particles according to the present invention comprises the following steps: mixing raw material powders composed of Li2CO3, Mn3O4, FePO4, and LiH2PO4 with a carbon source glucose and water in a stirring tank; grinding the uniformly mixed materials and then performing spray drying, subjecting the dried powder to a first sintering, and then crushing to prepare a first-sintering precursor material A; grinding the same mixed materials and then performing spray drying, subjecting the dried powder to a first sintering, changing the sintering temperature, and then crushing to prepare a first-sintering precursor material B; mixing the first-sintering precursor material A and the first-sintering precursor material B and then performing a second sintering to obtain a final product. The method for preparing high-compact lithium iron manganese phosphate material by coating large particles with small particles according to the present invention improves the compacting effect and simultaneously improves the electrical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium iron manganese phosphate material manufacturing, and particularly relates to a method for preparing high-compactness lithium iron manganese phosphate material by coating large particles with small particles. Background Art

[0002] As an upgraded direction of lithium iron phosphate batteries, lithium iron manganese phosphate has high safety and stability. Lithium iron manganese phosphate has an olivine structure, and Li+ ions can be embedded and extracted in the crystal to realize the charge and discharge of lithium ion batteries. During the process of lithium ion embedding and extraction, the crystal form can be maintained stable, with very good stability, ensuring the safety and high cycle performance of the battery. Compared with lithium iron phosphate, although the theoretical specific capacity of both is about 170 mAh / g, the overall discharge platform of lithium iron manganese phosphate is between 3.8V and 4.1V, while the theoretical discharge platform of lithium iron phosphate is 3.4V, and the actual level is 3.2 - 3.3V, and the energy density can be about 15% - 25% higher.

[0003] However, in practical applications, traditional lithium iron manganese phosphate has problems of low tap density and specific capacity (generally, the tap density is between 2.1 - 2.2 g / cm³ and the specific capacity is between 135 - 150 mAh / g), which cannot meet the urgent demand of power battery manufacturers for energy density improvement. Therefore, it is necessary to develop higher-performance lithium iron manganese phosphate cathode materials.

[0004] Therefore, the present invention is specifically proposed to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing high-compactness lithium iron manganese phosphate material by coating large particles with small particles, including the following steps:

[0006] (1) Mix the raw material powder composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 with carbon source glucose and water in a stirring tank;

[0007] (2) Grind the uniformly mixed material in step (1) in a sand mill and then perform spray drying. The dried powder is subjected to a first sintering, and then crushed to prepare a first-sintering precursor material A with a D50 of 5 - 10 μm;

[0008] (3) Obtain the same mixed material in the same manner as in step (1), grind it in a sand mill and then perform spray drying. The dried powder is subjected to a first sintering, change the sintering temperature, and then crush it to prepare a first-sintering precursor material B with a D50 of 1 - 4 μm;

[0009] (4) Mix a first sintering precursor material A and a first sintering precursor material B by physical mixing and then perform secondary sintering to obtain the final product.

[0010] Preferably, in step (1), the raw materials, carbon source glucose, and water are mixed according to the ratio of 28:7:65 by weight.

[0011] Preferably, the 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 The raw material powder composed of is proportioned according to the molar ratio of Li:Mn:Fe:P = (1.01 - 1.05):0.6:0.4:(0.96 - 1).

[0012] Preferably, the 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 The raw material powder composed of is proportioned according to the molar ratio of Li:Mn:Fe:P = 1.02:0.60:0.4:0.98.

[0013] Preferably, the sintering temperature in step (2) is a constant temperature of 700 °C, and the sintering constant temperature time is 9 h.

[0014] Preferably, the sintering temperature in step (3) is a constant temperature of 650 °C, and the sintering constant temperature time is 9 h.

[0015] Preferably, the grinding conditions in steps (2) and (3) are grinding to 0.3 μm at D50.

[0016] Preferably, in step (4), the physical mixing method is mixed according to the ratio of 90% large particles and 10% small particles.

[0017] Preferably, the temperature of the secondary sintering in step (4) is a constant temperature of 600 °C.

[0018] Preferably, the mass proportion of the carbon content after the first sintering in steps (2) and (3) is 1.45% - 1.55%.

[0019] Preferably, the powder after drying in steps (2) and (3) is subjected to the first sintering under a closed N 2 condition.

[0020] Preferably, the finished product after secondary sintering in step (4) is compacted to 2.3-2.5 g / cm³ to obtain the final product.

[0021] The beneficial effects of the present invention are as follows:

[0022] The tap density of the lithium iron manganese phosphate of the present invention is increased compared with the traditional one, and the specific capacity is significantly improved, which can meet the urgent need of power battery manufacturers for the improvement of energy density;

[0023] The preparation of high-tap-density lithium iron manganese phosphate material by coating large particles with small particles in the present invention improves the tap effect. At the same time, when the tap density increases, the voids between particles decrease, the hindrance to electron conduction decreases, and the resistivity decreases, which plays a role in improving the electrical performance. Description of the Drawings

[0024] Figure 1 It is a scanning electron microscope (SEM) image of the first-firing precursor material A;

[0025] Figure 2 It is a scanning electron microscope (SEM) image of the high-tap-density lithium iron manganese phosphate material prepared by coating large particles with small particles of the present invention. Detailed Embodiments

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0027] Example 1

[0028] A method for preparing a high-tap-density lithium iron manganese phosphate material by coating large particles with small particles in this embodiment includes the following steps:

[0029] (1) Mix the raw material powder composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 with the carbon source glucose and water in a stirring tank, and the mixing ratio is 28:7:65 by weight, where Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4The raw material powders are formulated according to the molar ratio of Li:Mn:Fe:P = 1.05:0.6:0.4:1;

[0030] (2) Grind the uniformly mixed materials in step (1) in a sand mill until D50 reaches 0.3 μm, then perform spray drying. The dried powder is sintered once at a constant temperature of 700 °C in a closed N 2 atmosphere. The constant temperature sintering time is 9 h, and then it is crushed to prepare a first-sintered precursor material A with D50 in the range of 5 - 10 μm;

[0031] (3) Obtain the same mixed materials in the same manner as in step (1), grind them in a sand mill until D50 reaches 0.3 μm, then perform spray drying. The dried powder is sintered once in a closed N 2 atmosphere. Change the sintering temperature to a constant temperature of 650 °C, and the constant temperature sintering time is 9 h. Then it is crushed to prepare a first-sintered precursor material B with D50 in the range of 1 - 4 μm;

[0032] (4) Physically mix the first-sintered precursor material A and the first-sintered precursor material B according to the ratio of 60% - 90% for large particles and 10% - 40% for small particles, and then perform secondary sintering. The temperature of the secondary sintering is a constant temperature of 600 °C. The finished product after secondary sintering is compacted to 2.3 - 2.5 g / cm³ to obtain the final product.

[0033] Example 2

[0034] A method for preparing a high-compact lithium iron manganese phosphate material with small particles coating large particles in this example includes the following steps:

[0035] (1) Mix the raw material powders composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 with the carbon source glucose and water in a stirring tank. The mixing ratio is 28:7:65 by weight. Among them, the raw material powders composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 are formulated according to the molar ratio of Li:Mn:Fe:P = 1.03:0.6:0.4:0.985;

[0036] (2) Grind the uniformly mixed materials in step (1) in a sand mill until D50 reaches 0.3 μm, then perform spray drying. The dried powder is sintered once at a constant temperature of 700 °C under a closed N 2 condition, with a constant sintering time of 9 h, and then crush to prepare a first-sintered precursor material A with D50 in the range of 5 - 10 μm;

[0037] (3) Obtain the same mixed materials in the same manner as in step (1), grind in a sand mill until D50 reaches 0.3 μm, then perform spray drying. The dried powder is sintered once under a closed N 2 condition, change the sintering temperature to a constant 650 °C, with a constant sintering time of 9 h, and then crush to prepare a first-sintered precursor material B with D50 in the range of 1 - 4 μm;

[0038] (4) Physically mix the first-sintered precursor material A and the first-sintered precursor material B according to the ratio of 60% - 90% large particles and 10% - 40% small particles, and then perform secondary sintering. The temperature of the secondary sintering is a constant 600 °C. The finished product after secondary sintering is compacted to obtain the final product at 2.3 - 2.5 g / cm³.

[0039] Example 3

[0040] A method for preparing a high-compact lithium iron phosphate manganese by coating small particles on large particles in this example includes the following steps:

[0041] (1) Mix the raw material powders composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 with the carbon source glucose and water in a stirring tank. The mixing ratio is 28:7:65 by weight. Among them, the raw material powders composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 are proportioned according to the molar ratio of Li:Mn:Fe:P = 1.01:0.6:0.4:0.96;

[0042] (2) Grind the uniformly mixed materials in step (1) in a sand mill until D50 reaches 0.3 μm, then perform spray drying. The dried powder is sintered once at a constant temperature of 700 °C under a closed N 2 condition, with a constant sintering time of 9 h, and then crush to prepare a first-sintered precursor material A with D50 in the range of 5 - 10 μm;

[0043] (3) Obtain the same mixed material in the same manner as in step (1), grind it to D50 of 0.3 μm in a sand mill, then perform spray drying. The dried powder is sintered once under a closed N 2 condition, change the sintering temperature to a constant temperature of 650 °C, and the sintering constant temperature time is 9 h, and then crush it to prepare a first-fired precursor material B with D50 of 1-4 μm;

[0044] (4) Physically mix the first-fired precursor material A and the first-fired precursor material B according to the ratio of 60%-90% large particles and 10%-40% small particles, and then perform secondary sintering. The temperature of the secondary sintering is a constant temperature of 600 °C, and the finished product after secondary sintering is compacted to 2.3-2.5 g / cm³ to obtain the final product.

[0045] Example 4

[0046] A method for preparing a high-compact lithium iron phosphate manganese material with small particles coating large particles in this example includes the following steps:

[0047] (1) Mix the raw material powder composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 with the carbon source glucose and water in a stirring tank. The mixing ratio is 28:7:65 by weight. Among them, the raw material powder composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 is proportioned according to the molar ratio of Li:Mn:Fe:P = 1.02:0.6:0.4:0.98;

[0048] (2) Grind the uniformly mixed material in step (1) to D50 of 0.3 μm in a sand mill, then perform spray drying. The dried powder is sintered once at a constant temperature of 700 °C under a closed N 2 condition, and the sintering constant temperature time is 9 h, and then crush it to prepare a first-fired precursor material A with D50 of 5-10 μm;

[0049] (3) Obtain the same mixed material in the same manner as in step (1), grind it to D50 of 0.3 μm in a sand mill, then perform spray drying. The dried powder is under a closed N 2Under the above conditions, perform sintering once, change the sintering temperature to a constant temperature of 650 °C, and the sintering constant temperature time is 9 h, and then crush to prepare a first-sintering precursor material B with a D50 of 1-4 μm;

[0050] (4)Physically mix the first-sintering precursor material A and the first-sintering precursor material B, and mix them according to the ratio of 60%-90% of large particles and 10%-40% of small particles, and then perform secondary sintering. The temperature of the secondary sintering is a constant temperature of 600 °C. The finished product after the secondary sintering is compacted to 2.3-2.5 g / cm³ to obtain the final product.

[0051] Comparative Example 1

[0052] A method for preparing a high-compact lithium iron manganese phosphate material with small particles coating large particles in this embodiment includes the following steps:

[0053] (1)Mix the raw material powder composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 with the carbon source glucose and water in a stirring tank. The mixing ratio is 28:7:65 by weight. Among them, the raw material powder composed of Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO 4 is proportioned according to the molar ratio of Li:Mn:Fe:P = 1.05:0.6:0.4:1;

[0054] (2)Grind the uniformly mixed materials in step (1) in a sand mill to a D50 of 0.3 μm, then perform spray drying. The dried powder is sintered once at a constant temperature of 700 °C under a closed N 2 condition. The sintering constant temperature time is 9 h, and then crush to prepare a final product with a D50 of 5-20 μm.

[0055] Comparative Example 2

[0056] A method for preparing a high-compact lithium iron manganese phosphate material with small particles coating large particles in this embodiment includes the following steps:

[0057] (1)Mix Li 2 CO 3 , Mn 3 O 4 , FePO 4 , LiH 2 PO4 The raw material powder composed of, glucose as the carbon source, and water are mixed in a stirring tank, and the mixing ratio is 28:7:65 by weight, where Li 2 CO 3 , Mn 3 O 4 ,

[0058] FePO 4 , LiH 2 PO 4 The raw material powder is proportioned according to the molar ratio of Li:Mn:Fe:P = 1.01:0.6:0.4:0.96;

[0059] (2) The uniformly mixed materials in step (1) are ground to D50 of 0.3 μm in a sand mill and then spray-dried. The dried powder is sintered once at a constant temperature of 700 °C under a closed N 2 condition for 9 h, and then crushed to prepare a final product with D50 of 5 - 20 μm.

[0060] Actual test

[0061] Test of tap density: For the lithium iron manganese phosphate cathode materials prepared in the above examples and comparative examples, weigh 1.00 g of the sample and add it to the cavity of the instrument for testing tap density, and test the tap density under a certain pressure according to the process requirements.

[0062] Capacity test: For the lithium iron manganese phosphate cathode materials prepared in the above examples and comparative examples, prepare button cells for electrochemical performance testing. The specific steps include: uniformly mixing the lithium iron manganese phosphate cathode material, conductive agent cnt, and binder PVDF in a ratio of 90:5:5 in NMP, then coating it on aluminum foil and drying it in a vacuum drying oven. After drying, assemble the battery in an argon glove box, press it into a positive electrode plate with a tablet press. The negative electrode is a lithium metal sheet, and the electrolyte is 1 mol / L LiPF6 - EC:DMC (volume ratio 1:1), and a polypropylene porous membrane is used as the separator. The parameter conditions selected for testing the electrochemical performance are: the test voltage range is 2.5 - 4.3 V, and the tested tap density, discharge condition, and resistivity are shown in Table 1.

[0063] Table 1

[0064] It can be seen from the table that compared with Comparative Examples 1 and 2, the tap density of the examples is increased by more than 0.3, and the resistivity is improved. This is because the small particles coated on the surface of the large particles can fill the voids of the large particles, thus improving the tap density. When the tap density increases, the voids between the particles decrease, the hindrance to electron conduction is reduced, and the resistivity decreases, playing a role in improving the electrical performance.

[0065] As described above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A method for preparing high-density lithium manganese iron phosphate material by coating large particles with small particles, characterized in that: The following steps are involved: (1) mixing raw material powders composed of Li2CO3, Mn3O4, FePO4, and LiH2PO4 with carbon source glucose and water in a stirring tank, wherein the raw material powders composed of Li2CO3, Mn3O4, FePO4, and LiH2PO4 are proportioned according to a molar ratio of Li:Mn:Fe:P=(1.01-1.05):0.6:0.4:(0.96-1); (2) grinding the uniformly mixed materials in step (1) in a sand mill and then spray drying, sintering the dried powder once, and then crushing to prepare a sintered precursor material A with a D50 of 5 to 10 μm; (3) The same mixed material is obtained in the manner of step (1), ground in a sand mill and then spray dried, the dried powder is sintered once, the sintering temperature is changed, and then crushed to prepare a sintered precursor material B with a D50 of 1 to 4 μm; (4) mixing the first-fired precursor material A and the first-fired precursor material B in a physical mixing manner and then performing secondary sintering to obtain a final product, wherein the physical mixing manner is such that large particles account for 60% to 90% and small particles account for 10% to 40%; The grinding conditions in steps (2) and (3) are grinding to 0.3 μm at D50, and the carbon content after the first sintering accounts for 1.45% to 1.55% by weight.

2. The method for preparing high-density lithium manganese iron phosphate material by coating large particles with small particles according to claim 1, characterized in that: The raw materials, carbon source glucose and water in step (1) are mixed in a ratio of 28:7:65 by weight.

3. The method for preparing high-density lithium manganese iron phosphate material by coating large particles with small particles according to claim 1, characterized in that: The raw material powders composed of Li2CO3, Mn3O4, FePO4 and LiH2PO4 are mixed according to the molar ratio of Li:Mn:Fe:P=1.02:0.60:0.4:0.

98.

4. The method for preparing high-density lithium manganese iron phosphate material by coating large particles with small particles according to claim 1, characterized in that: The sintering temperature in step (2) is a constant temperature of 700° C., and the sintering constant temperature time is 9 hours.

5. The method for preparing high-density lithium manganese iron phosphate material by coating large particles with small particles according to claim 1, characterized in that: The sintering temperature in step (3) is a constant temperature of 650° C., and the sintering constant temperature time is 9 hours.

6. The method for preparing high-density lithium manganese iron phosphate material by coating large particles with small particles according to claim 1, characterized in that: The temperature of the secondary sintering in step (4) is a constant temperature of 600°C.

7. The method for preparing high-density lithium iron manganese phosphate material by coating large particles with small particles according to claim 1, characterized in that: The powder dried in steps (2) and (3) is sintered once under closed N2 conditions.

8. The method for preparing high-density lithium manganese iron phosphate material by coating large particles with small particles according to claim 1, characterized in that: The finished product after secondary sintering in step (4) is compacted to obtain the final product at 2.3-2.5 g / cm³.

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