A kind of manganese iron lithium phosphate positive electrode material and its preparation method are broken and ball milled

Abstract

The application discloses a kind of preparation methods of manganese iron lithium phosphate positive electrode material by breaking wall and ball milling, belong to electrode material technical field, the method includes the following steps: lithium source, manganese source, iron source, ammonium dihydrogen phosphate and glucose are put into breaking wall machine and are broken and mixed;Then ball milling is carried out, until the granularity of powder reaches 150~200nm;Solvent and dispersing agent are added into ball mill jar and continue ball milling 4~7h, obtain slurry;Slurry is transferred to stirrer, after non-oxidizing gas is inhaled, it is stirred while heating, dry, obtain precursor material;Precursor material is ground and sieved;Then put into anvil with cover, sinter under non-oxidizing atmosphere, after sintering is finished, cool to room temperature, obtain manganese iron lithium phosphate positive electrode material.The method is simple in operation, raw material is less in contact with air, can better control material metamorphism, suitable for mass production, and the obtained manganese iron lithium phosphate positive electrode material has excellent specific capacity and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to a lithium manganese iron phosphate cathode material prepared by cell wall breaking and ball milling, and its preparation method. Background Technology

[0002] With the continuous improvement of people's living standards, the consumption of non-renewable energy and the increasing severity of environmental problems, traditional fossil energy can no longer meet people's needs. Therefore, the new energy industry is receiving more and more attention. Since Goodenough discovered phosphate-based cathode materials, researchers have conducted more in-depth studies on phosphate cathode materials and industrialized them.

[0003] Like lithium iron phosphate, lithium manganese iron phosphate also has a stable olivine structure. Both have a theoretical capacity of 170 mAh / g. However, lithium iron phosphate has a voltage platform of only 3.4V, while lithium manganese iron phosphate can reach 4.1V. This makes the energy density of the latter about 20% higher than that of lithium iron phosphate. At the same time, lithium manganese iron phosphate has the advantages of good safety, good cycle performance and low cost, making it an ideal green lithium-ion battery cathode material.

[0004] Currently, the main synthesis methods for lithium manganese iron phosphate electrode materials are liquid-phase and solid-phase methods. Liquid-phase methods produce particles with smooth surfaces and small particle sizes, but reducing particle size lowers compaction density. Excessively small particle sizes result in large specific surface areas, requiring large amounts of binders and increasing costs. Solid-phase methods, on the other hand, are simpler and easier to control, making them suitable for large-scale industrial production. They also produce lithium manganese iron phosphate cathode materials with high compaction density. However, existing solid-phase processes often involve mixing raw materials in a sand mill, coating the particle surface with a carbon source after the slurry dries, and finally spray drying. These methods are energy-intensive and significantly impact the cost control of electrode materials.

[0005] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0006] The purpose of this invention is to provide a lithium manganese iron phosphate cathode material that has undergone cell wall breaking and ball milling, and its preparation method, so as to solve the problem of high energy consumption when producing lithium manganese iron phosphate cathode material by solid-state method.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling includes the following steps:

[0009] Step 1: Put the lithium source, manganese source, iron source, ammonium dihydrogen phosphate and glucose into a high-speed blender and crush and mix them intermittently several times.

[0010] Step 2: Ball mill the raw materials that have undergone cell wall breaking treatment until the particle size of the powder reaches 150~200nm;

[0011] Step 3: Add the solvent and dispersant to the ball mill jar and continue ball milling for 4-7 hours to obtain a uniform slurry;

[0012] Step 4: Transfer the slurry to a mixer, introduce a non-oxidizing gas, and heat and stir simultaneously to dry it. The heating temperature is 40~90℃ to obtain the precursor material.

[0013] Step 5: Grind and sieve the precursor material;

[0014] Step 6: Place the sieved precursor material into a covered crucible and sinter it under a non-oxidizing atmosphere. After sintering, cool it to room temperature to obtain lithium manganese iron phosphate cathode material.

[0015] Preferably, in step one, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, and lithium acetate; the manganese source includes one or more of manganese dihydrogen phosphate, manganese carbonate, manganese dioxide, and manganese tetroxide; the iron source includes one or more of ferric phosphate, ferrous oxalate, and ferrous acetate, and the time for each crushing and mixing is 1-2 minutes.

[0016] Preferably, in steps two and three, the ball-to-material ratio is 5:1 to 10:1, the ball mill speed is 350 to 400 rpm, and the ball milling time is 1 to 4 hours.

[0017] Preferably, in step three, the solvent includes anhydrous ethanol, and the dispersant includes one or more of oleic acid, hexanoic acid, and polyacryl alcohol.

[0018] Preferably, in step three, the solvent further includes glycerol, the volume of which does not exceed 10% of the volume of anhydrous ethanol, the volume ratio of the dispersant to anhydrous ethanol is 1:30 to 1:20, and the solid content of the slurry is 40 to 60%.

[0019] Preferably, in step four, the stirring speed is 150~250 rpm.

[0020] Preferably, in step five, the sieve mesh size is 100-200 mesh.

[0021] Preferably, in step six, the rate of introduction of non-oxidizing gas is 200~300 mL / min, sintering is carried out in a tube furnace, the tube furnace is purged with non-oxidizing gas before sintering, the sintering temperature is 650~700℃, and the time is 8~12h.

[0022] Preferably, in step six, the replacement method is to first evacuate the vacuum and then fill it with a non-oxidizing gas, and replace it at least three times.

[0023] This invention also provides a lithium manganese iron phosphate cathode material that has undergone cell wall breaking and ball milling, prepared by any of the methods described above, wherein the general formula of the lithium manganese iron phosphate cathode material is LiMn. x Fe 1-x PO4 / C, where 0.5≤x≤0.8.

[0024] Beneficial effects:

[0025] The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling provided by the present invention is simple and easy to achieve large-scale production. The equipment involved is simple, energy consumption is low, and production costs can be reduced. The slurry used in the preparation process has a high solid content, which can improve production efficiency. The electrode material prepared by this process is mainly solid solution phase, which can meet the current performance requirements of high specific capacity, high rate and good dispersibility of batteries. Attached Figure Description

[0026] Figure 1 The specific capacity test results are for the lithium manganese iron phosphate cathode material prepared in Example 1.

[0027] Figure 2 The specific capacity cycling test results are for the lithium manganese iron phosphate cathode material prepared in Example 1. Detailed Implementation

[0028] 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, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0029] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0030] This invention addresses the problem of high energy consumption in the solid-state production of lithium manganese iron phosphate cathode materials by providing a method for preparing lithium manganese iron phosphate cathode materials through cell wall breaking and ball milling. This method includes the following steps:

[0031] Step 1: Put the lithium source, manganese source, iron source, ammonium dihydrogen phosphate and glucose into a high-speed blender and crush and mix them intermittently several times.

[0032] Step 2: Ball mill the raw materials that have undergone cell wall breaking treatment until the particle size of the powder reaches 150~200nm (e.g., 151nm, 155nm, 160nm, 165nm, 170nm, 175nm, 180nm, 185nm, 190nm, 195nm, 199nm).

[0033] Step 3: Add the solvent and dispersant to the ball mill jar and continue ball milling for 4-7 hours (e.g., 4.5 hours, 5.0 hours, 5.5 hours, 6.0 hours, 6.5 hours, 6.9 hours) to obtain a uniform slurry;

[0034] Step 4: Transfer the slurry to a mixer, introduce a non-oxidizing gas, and heat and stir simultaneously to dry it. The heating temperature is 40~90℃ (41℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 89℃) to obtain the precursor material.

[0035] Step 5: Grind and sieve the precursor material;

[0036] Step 6: Place the sieved precursor material into a covered crucible and sinter it under a non-oxidizing atmosphere. After sintering, cool it to room temperature to obtain lithium manganese iron phosphate cathode material.

[0037] In a preferred embodiment of the present invention, in step one, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, and lithium acetate; the manganese source includes one or more of manganese dihydrogen phosphate, manganese carbonate, manganese dioxide, and manganese tetroxide; the iron source includes one or more of ferric phosphate, ferrous oxalate, and ferrous acetate, and the time for each crushing and mixing is 1 to 2 minutes (e.g., 1 minute 1 second, 1 minute 5 seconds, 1 minute 10 seconds, 1 minute 15 seconds, 1 minute 20 seconds, 1 minute 25 seconds, 1 minute 30 seconds, 1 minute 35 seconds, 1 minute 40 seconds, 1 minute 45 seconds, 1 minute 50 seconds, 1 minute 55 seconds, 1 minute 59 seconds).

[0038] In a preferred embodiment of the present invention, in steps two and three, the ball-to-material ratio is 5:1 to 10:1 (e.g., 5:1, 6:1, 7:1, 8:1, 9:1), the ball mill speed is 350 to 400 rpm (e.g., 351 rpm, 355 rpm, 360 rpm, 365 rpm, 370 rpm, 375 rpm, 380 rpm, 385 rpm, 390 rpm, 395 rpm, 399 rpm), and the ball milling time is 1 to 4 hours (e.g., 1.5 hours, 2.0 hours, 2.5 hours, 3.0 hours, 3.5 hours).

[0039] In a preferred embodiment of the present invention, in step three, the solvent is anhydrous ethanol, and the dispersant includes one or more of oleic acid, hexanoic acid, and polyacryl alcohol.

[0040] In a preferred embodiment of the present invention, in step three, the volume of glycerol used does not exceed 10% of the volume of anhydrous ethanol (e.g., 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 9.9%), the volume ratio of dispersant to anhydrous ethanol is 1:30 to 1:20 (e.g., 1:29, 1:28, 1:27, 1:26, 1:25, 1:24, 1:23, 1:22, 1:21), and the solid content of the slurry is 40 to 60% (e.g., 41%, 43%, 45%, 47%, 49%, 50%, 51%, 53%, 55%, 57%, 59%).

[0041] In a preferred embodiment of the present invention, in step four, the stirring speed is 150~250 rpm (e.g., 155 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 245 rpm).

[0042] In a preferred embodiment of the present invention, in step five, the mesh size of the sieve is 100 to 200 mesh (e.g., 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh).

[0043] In a preferred embodiment of the present invention, in step six, the rate of introduction of non-oxidizing gas is 200-300 mL / min (e.g., 210 mL / min, 220 mL / min, 230 mL / min, 240 mL / min, 250 mL / min, 260 mL / min, 270 mL / min, 280 mL / min, 290 mL / min), sintering is performed using a tubular furnace, the tubular furnace is purged with non-oxidizing gas before sintering, the sintering temperature is 650-700℃ (e.g., 655℃, 660℃, 665℃, 670℃, 675℃, 680℃, 685℃, 690℃, 695℃), and the time is 8-12h (e.g., 8.5h, 9.0h, 9.5h, 10.0h, 10.5h, 11.0h, 11.5h).

[0044] In a preferred embodiment of the present invention, in step six, the replacement method is to first evacuate the vacuum and then fill it with a non-oxidizing gas, and replace it at least three times.

[0045] This invention also proposes a lithium manganese iron phosphate cathode material, obtained by the above-described preparation method, wherein the general formula of the lithium manganese iron phosphate cathode material is LiMn. x Fe 1-x PO4 / C; where 0.5≤x≤0.8 (e.g., x=0.5, x=0.6, x=0.7, x=0.8).

[0046] The following detailed description of a lithium manganese iron phosphate cathode material prepared by cell wall breaking and ball milling, and its preparation method, is provided through specific embodiments of the present invention.

[0047] In the following embodiment:

[0048] The non-oxidizing gas used is nitrogen, argon, or an argon-hydrogen mixture, with the hydrogen content in the argon-hydrogen mixture not exceeding 5%.

[0049] The blender used has a power of 900W.

[0050] Example 1

[0051] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.6:1, with 30 mmol of lithium carbonate (2.2167 g). All the above materials were placed in a blender, and glucose was added as a carbon source at 8% of the total mass of the other raw material powders. The blender was then crushed and mixed for 1 minute each time, for a total of 3 runs. The powder was then placed in a ball mill and ball-milled for 2 hours at a ball-to-powder ratio of 5:1 at a speed of 350 rpm to obtain the powder.

[0052] Add 25 mL of solvent, which is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol, and then add oleic acid, the volume ratio of oleic acid to anhydrous ethanol being 1:30. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0053] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C, test its discharge specific capacity, such as Figure 1 As shown.

[0054] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0055] Example 2

[0056] Lithium carbonate, iron phosphate, manganese tetroxide, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.2:1, with 30 mmol of lithium carbonate (2.2167 g). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 1 minute, for a total of 3 runs. The powder was then placed in a ball mill and ball-milled for 2 hours at a ball-to-powder ratio of 5:1 and a ball mill speed of 350 rpm to obtain the final powder.

[0057] Add 25 mL of solvent to the above powder. The solvent is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 10% of that of anhydrous ethanol. Then add hexanoic acid, with a volume ratio of hexanoic acid to anhydrous ethanol of 1:30. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0058] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0059] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0060] Example 3

[0061] Lithium carbonate, iron phosphate, manganese dioxide, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.6:1, with 30 mmol of lithium carbonate (2.2167 g). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 1 minute, for a total of 3 runs. The powder was then placed in a ball mill and ball-milled for 2 hours at a ball-to-powder ratio of 5:1 and a ball mill speed of 350 rpm to obtain the final powder.

[0062] Add 25 mL of solvent, which is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol, and then add polyacrylol, with a volume ratio of polyacrylol to anhydrous ethanol of 1:20. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0063] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0064] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0065] Example 4

[0066] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.6:1, with 30 mmol of lithium carbonate (2.2167 g). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 2 minutes, for a total of 4 runs. The powder was then placed in a ball mill and ball-milled for 2 hours, with a ball-to-powder ratio of 5:1 and a ball mill speed of 350 rpm, to obtain the final powder.

[0067] Add 25 mL of solvent, namely anhydrous ethanol, to the above powder, then add oleic acid, with a volume ratio of oleic acid to anhydrous ethanol of 1:25, and continue ball milling for 5 hours to obtain a uniform slurry; transfer the slurry to a stirrer, and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0068] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0069] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0070] Example 5

[0071] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.6:0.4:1, with 30 mmol of lithium carbonate (2.2167 g). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 1 minute, for a total of 4 runs. The powder was then placed in a ball mill and ball-milled for 4 hours, with a ball-to-powder ratio of 5:1 and a ball mill speed of 350 rpm, to obtain the final powder.

[0072] Add 25 mL of solvent to the above powder. The solvent is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol. Then add oleic acid, with a volume ratio of oleic acid to anhydrous ethanol of 1:30. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 90°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0073] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 8 hours in a non-oxidizing atmosphere at a sintering temperature of 700℃ and a non-oxidizing gas flow rate of 300 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.4 Fe 0.6 PO4 / C.

[0074] In this embodiment, the non-oxidizing gas used is argon.

[0075] Example 6

[0076] Lithium acetate, ferrous acetate, manganese dihydrogen phosphate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 1:0.4:0.6:1, with 60 mmol of lithium acetate (3.9594 g). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 2 minutes, for a total of 4 runs. The powder was then placed in a ball mill and ball-milled for 1 hour, with a ball-to-powder ratio of 10:1 and a ball mill speed of 350 rpm, to obtain the final powder.

[0077] Add 25 mL of solvent, which is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol, and then add oleic acid, the volume ratio of oleic acid to anhydrous ethanol being 1:30. Continue ball milling for 7 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 70°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0078] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 10 hours in a non-oxidizing atmosphere at a sintering temperature of 680℃ and a non-oxidizing gas flow rate of 260 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0079] In this embodiment, the non-oxidizing gas used is argon.

[0080] Example 7

[0081] Lithium hydroxide, ferrous acetate, manganese dihydrogen phosphate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 1:0.4:0.6:1, with 60 mmol of lithium hydroxide (1.4369 g). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 2 minutes, for a total of 4 runs. The powder was then placed in a ball mill and ball-milled for 2 hours, with a ball-to-powder ratio of 8:1 and a ball mill speed of 350 rpm, to obtain the final powder.

[0082] Add 25 mL of solvent, which is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol, and then add oleic acid, the volume ratio of oleic acid to anhydrous ethanol being 1:30. Continue ball milling for 4 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0083] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 10 hours in a non-oxidizing atmosphere at a sintering temperature of 700℃ and a non-oxidizing gas flow rate of 300 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0084] In this embodiment, the non-oxidizing gas used is argon.

[0085] Example 8

[0086] Lithium dihydrogen phosphate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 1:0.4:0.6:1, with 60 mmol (6.2357 g) of lithium dihydrogen phosphate. The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 1 minute, for a total of 3 runs. The powder was then placed in a ball mill and ball-milled for 2 hours at a ball-to-powder ratio of 5:1 and a ball mill speed of 350 rpm to obtain the final powder.

[0087] Add 25 mL of solvent, which is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol, and then add oleic acid, the volume ratio of oleic acid to anhydrous ethanol being 1:30. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0088] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0089] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0090] Example 9

[0091] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.2:0.8:1, with 30 mmol of lithium carbonate (2.2167 g). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 1 minute, for a total of 3 runs. The powder was then placed in a ball mill and ball-milled for 2 hours at a ball-to-powder ratio of 5:1 and a ball mill speed of 350 rpm to obtain the powder.

[0092] Add 25 mL of solvent, which is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol, and then add oleic acid, the volume ratio of oleic acid to anhydrous ethanol being 1:30. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0093] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.8 Fe 0.2 PO4 / C.

[0094] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0095] Example 10

[0096] Lithium acetate, ferrous acetate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 1.0:0.5:0.5:1, with 60 mmol of lithium acetate (3.9594 g). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed, with each blender run lasting 1 minute, for a total of 3 runs. The powder was then placed in a ball mill and ball-milled for 2 hours at a ball-to-powder ratio of 5:1 and a ball mill speed of 350 rpm to obtain the final powder.

[0097] Add 25 mL of solvent, which is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol, and then add oleic acid, the volume ratio of oleic acid to anhydrous ethanol being 1:30. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it and obtain the precursor material.

[0098] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.5 Fe 0.5 PO4 / C.

[0099] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0100] Comparative Example 1

[0101] This comparative example provides a lithium manganese iron phosphate cathode material. Its preparation method is based on Example 1, but the step of crushing and mixing the raw materials using a blender is omitted, while other conditions remain unchanged. The specific details are as follows:

[0102] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.6:1, with 30 mmol of lithium carbonate (2.2167 g in mass). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The powder was then placed in a ball mill and ball-milled for 2 hours at a ball-to-powder ratio of 5:1 and a ball mill speed of 350-400 rpm to obtain the powder.

[0103] Add 25 mL of solvent to the above powder. The solvent is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol. Then add oleic acid, with a volume ratio of oleic acid to anhydrous ethanol of 1:30. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it in a water bath at 50°C while stirring under a non-oxidizing atmosphere to dry it.

[0104] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0105] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0106] Comparative Example 2

[0107] This comparative example provides a lithium manganese iron phosphate cathode material, whose preparation method is based on Example 2, omitting the ball milling process while keeping other conditions unchanged, as follows:

[0108] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.6:1, with 30 mmol of lithium carbonate (2.2167 g in mass). The mixture was placed in a blender, and glucose was added as a carbon source. The amount of carbon source added was 8% of the total mass of the other raw material powders. The mixture was then crushed and mixed. Each blender run lasted 1 minute, and the process was repeated 3 times to obtain the powder.

[0109] Add 25 mL of solvent to the above powder. The solvent is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 10% of that of anhydrous ethanol. Then add hexanoic acid, with a volume ratio of hexanoic acid to anhydrous ethanol of 1:30. Then use a high-speed blender to break it down to obtain a uniform slurry. Transfer the slurry to a stirrer and heat it while stirring under a non-oxidizing atmosphere to dry it.

[0110] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0111] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0112] Comparative Example 3

[0113] This comparative example provides a lithium manganese iron phosphate cathode material. Its preparation method is based on Example 1, but omits the crushing and mixing process using a wall-wall blender and the ball milling process, while keeping other conditions unchanged. The specific details are as follows:

[0114] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.6:1, with 30 mmol of lithium carbonate (2.2167 g in mass). The mixture was placed in a mortar, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. Then, 25 mL of solvent was added, which was a mixed solution of anhydrous ethanol and glycerol, with the volume of glycerol being 5% of the volume of anhydrous ethanol. Then, oleic acid was added, with the volume ratio of oleic acid to anhydrous ethanol being 1:20. The mixture was then stirred and mixed for 15 minutes to obtain a uniform slurry.

[0115] The slurry was transferred to a stirrer and dried under a non-oxidizing atmosphere by stirring and heating. The dried precursor material was then ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was purged three times, it was sintered for 12 hours under a non-oxidizing atmosphere at a temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0116] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0117] Comparative Example 4

[0118] This comparative example provides a lithium manganese iron phosphate cathode material, whose preparation method is based on Example 3, using a sand mill instead of a wall-breaking machine to crush and mix the raw materials and the ball milling process, while keeping other conditions unchanged, as follows:

[0119] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.6:1, with 30 mmol of lithium carbonate (2.2167 g). The mixture was placed in a blender, and glucose was added as a carbon source, amounting to 8% of the total mass of the other raw material powders. Then, 25 mL of a solvent, a mixture of anhydrous ethanol and glycerol (5% of the volume of anhydrous ethanol), was added. Polyacrylamide was then added, with a volume ratio of polyacrylamide to anhydrous ethanol of 1:20. The mixture was then ground in a sand mill for 4 hours to obtain a uniform slurry. The slurry was transferred to a stirrer and dried under a non-oxidizing atmosphere while being stirred and heated.

[0120] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0121] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0122] Comparative Example 5

[0123] This comparative example provides a lithium manganese iron phosphate cathode material. Its preparation method is based on Example 1, but the step of crushing and mixing the raw materials using a wall-breaking machine is omitted, and the ball milling time is extended, while other conditions remain unchanged. The details are as follows:

[0124] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.4:0.6:1, with 30 mmol of lithium carbonate (2.2167 g in mass). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The powder was then placed in a ball mill and ball-milled for 4 hours at a ball-to-powder ratio of 5:1 and a ball mill speed of 350 rpm to obtain the powder.

[0125] Add 25 mL of solvent to the above powder. The solvent is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol. Then add oleic acid, with a volume ratio of oleic acid to anhydrous ethanol of 1:30. Continue ball milling for 5 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and dry it by stirring and heating under a non-oxidizing atmosphere.

[0126] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.6 Fe 0.4 PO4 / C.

[0127] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0128] Comparative Example 6

[0129] This comparative example provides a lithium manganese iron phosphate cathode material. Its preparation method is based on Example 9, but the step of crushing and mixing the raw materials using a blender is omitted, while other conditions remain unchanged. The specific details are as follows:

[0130] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.2:0.8:1, with 30 mmol of lithium carbonate (2.2167 g in mass). The mixture was placed in a blender, and glucose was added as a carbon source, with the amount of carbon source added being 8% of the total mass of the other raw material powders. The powder was then placed in a ball mill and ball-milled for 4 hours at a ball-to-material ratio of 5:1 and a ball mill speed of 350 rpm to obtain the powder.

[0131] Add 25 mL of solvent to the above powder. The solvent is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol. Then add oleic acid, with a volume ratio of oleic acid to anhydrous ethanol of 1:30. Continue ball milling for 4 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and dry it by stirring and heating under a non-oxidizing atmosphere.

[0132] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.8 Fe 0.2 PO4 / C.

[0133] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0134] Comparative Example 7

[0135] This comparative example provides a lithium manganese iron phosphate cathode material. Its preparation method is based on Example 10, but the step of crushing and mixing the raw materials using a blender is omitted, while other conditions remain unchanged. The specific details are as follows:

[0136] Lithium carbonate, iron phosphate, manganese carbonate, and ammonium dihydrogen phosphate were weighed in a molar ratio of 0.5:0.5:0.5:1, with 30 mmol of lithium carbonate (2.2167 g in mass). The mixture was placed in a blender, and glucose was added as a carbon source. The amount of carbon source added was 8% of the total mass of the other raw material powders. The powder was then placed in a ball mill and ball-milled for 4 hours at a ball-to-material ratio of 5:1 and a ball mill speed of 350 rpm to obtain the powder.

[0137] Add 25 mL of solvent to the above powder. The solvent is a mixed solution of anhydrous ethanol and glycerol, wherein the volume of glycerol is 5% of that of anhydrous ethanol. Then add oleic acid, with a volume ratio of oleic acid to anhydrous ethanol of 1:30. Continue ball milling for 4 hours to obtain a uniform slurry. Transfer the slurry to a stirrer and dry it by stirring and heating under a non-oxidizing atmosphere.

[0138] The dried precursor material was ground and sieved through a 100-mesh sieve. The sieved powder was placed in a covered crucible and then placed in a tube furnace. After the gas inside the tube furnace was replaced three times, it was sintered for 12 hours in a non-oxidizing atmosphere at a sintering temperature of 650℃ and a non-oxidizing gas flow rate of 200 mL / min to obtain the lithium manganese iron phosphate cathode material LiMn. 0.5 Fe 0.5 PO4 / C.

[0139] In this embodiment, the non-oxidizing gas used is an argon-hydrogen mixture, in which hydrogen accounts for 5%.

[0140] Performance testing

[0141] The lithium manganese iron phosphate cathode materials prepared in Examples 1-10 and Comparative Examples 1-6 were subjected to button cell testing. 4g of the above lithium manganese iron phosphate cathode material, 0.5g of conductive graphite, and 0.5g of polyvinylidene fluoride were mixed in a planetary ball mill at 300 rpm. The coating thickness was 300μm. After drying, the mixture was cut into uniformly sized round pieces for button cell assembly. After standing, the pieces were tested, and their discharge specific capacity and rate performance were compared (see Table 1). The discharge specific capacity of Example 1 is shown below. Figure 1 As shown.

[0142] Table 1 Performance test results of lithium manganese iron phosphate cathode materials prepared in different embodiments and comparative examples

[0143]

[0144] As shown in Table 1 above, in Examples 1 to 10, the discharge specific capacity at 0.1C can reach above 154 mAh / g, with a maximum of 163.4 mAh / g, and the discharge specific capacity at 1.0C can reach above 145 mAh / g, with a maximum of 153.4 mAh / g, all of which are significantly better than the comparative examples.

[0145] Comparative Examples 8-10 and 5-7 show that, based on ball milling, further breaking down the raw materials can improve the discharge performance of the obtained lithium manganese iron phosphate cathode material, and this effect becomes more pronounced as the proportion of manganese source in the raw materials increases.

[0146] Taking Example 1 as an example, its cycle life was tested, such as... Figure 2 As shown, after 35 cycles, its specific capacity still showed no signs of decay, demonstrating good cycling performance.

[0147] In summary, this invention provides a lithium manganese iron phosphate cathode material prepared by cell wall breaking and ball milling, and its preparation method. The preparation method is simple and easy to achieve large-scale production. Furthermore, the equipment involved is simple, energy-efficient, and can reduce production costs. The obtained lithium manganese iron phosphate cathode material has advantages such as high specific capacity, high rate capability, and good cycle life.

[0148] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing lithium manganese iron phosphate cathode material by cell wall breaking and ball milling, characterized in that, Includes the following steps: Step 1: Put the lithium source, manganese source, iron source, ammonium dihydrogen phosphate and glucose into a high-speed blender and blend intermittently 3 to 4 times, with each blending time being 1 to 2 minutes. Step 2: Ball mill the raw materials that have undergone cell wall breaking treatment until the particle size of the powder reaches 150~200nm; Step 3: Add the solvent and dispersant to the ball mill jar and continue ball milling for 4-7 hours to obtain a uniform slurry; Step 4: Transfer the slurry to a mixer, introduce a non-oxidizing gas, and heat and stir simultaneously to dry it. The heating temperature is 40~90℃ to obtain the precursor material. Step 5: Grind and sieve the precursor material; Step 6: Place the sieved precursor material into a covered crucible and sinter it under a non-oxidizing atmosphere. After sintering, cool it to room temperature to obtain lithium manganese iron phosphate cathode material.

2. The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling as described in claim 1, characterized in that, In step one, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, and lithium acetate; the manganese source includes one or more of manganese dihydrogen phosphate, manganese carbonate, manganese dioxide, and manganese tetroxide; and the iron source includes one or more of ferric phosphate, ferrous oxalate, and ferrous acetate.

3. The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling as described in claim 1, characterized in that, In steps two and three, the ball-to-material ratio is 5:1 to 10:1, the ball mill speed is 350 to 400 rpm, and the ball milling time is 1 to 4 hours.

4. The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling as described in claim 1, characterized in that, In step three, the solvent includes anhydrous ethanol, and the dispersant includes one or more of oleic acid, hexanoic acid, and polyacryl alcohol.

5. The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling as described in claim 1, characterized in that, In step three, the solvent also includes glycerol, the volume of which does not exceed 10% of the volume of anhydrous ethanol, the volume ratio of the dispersant to anhydrous ethanol is 1:30 to 1:20, and the solid content of the slurry is 40 to 60%.

6. The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling as described in claim 1, characterized in that, In step four, the stirring speed is 150~250 rpm.

7. The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling as described in claim 1, characterized in that, In step five, the sieve mesh size is 100-200 mesh.

8. The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling as described in claim 1, characterized in that, In step six, the non-oxidizing gas is introduced at a rate of 200-300 mL / min, and sintering is carried out in a tube furnace. Before sintering, the tube furnace is purged with non-oxidizing gas. The sintering temperature is 650-700℃ and the time is 8-12 h.

9. The method for preparing lithium manganese iron phosphate cathode material after cell wall breaking and ball milling as described in claim 8, characterized in that, In step six, the replacement method involves first evacuating the vacuum, then filling with a non-oxidizing gas, and repeating the replacement at least three times.

10. A lithium manganese iron phosphate cathode material subjected to cell wall breaking and ball milling, characterized in that, The lithium manganese iron phosphate cathode material is prepared by the method described in any one of claims 1 to 9, and the general formula of the material is LiMn. x Fe 1-x PO4 / C, where 0.5≤x≤0.8.

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