A method for preparing lithium manganese iron phosphate

Abstract

The invention discloses a method for preparing lithium iron manganese phosphate, belonging to the technical field of lithium batteries; the invention provides a method for preparing lithium iron manganese phosphate, comprising the following steps: step 1: putting manganese iron oxalate, lithium dihydrogen phosphate, lithium carbonate, sucrose, and magnesium hydroxide into equipment in sequence, adding anhydrous ethanol and then ball milling to obtain slurry A; step 2: filtering the slurry A in step 1 through a 100-mesh drying net, spray drying to obtain powder B; step 3: placing the powder B in step 2 under an inert gas atmosphere, sintering to obtain sintered material C; step 4: ball milling the sintered material C in step 3, polyvinyl alcohol, and anhydrous ethanol to obtain slurry D; step 5: spray drying the slurry D in step 4 to obtain powder E; step 6: placing the powder E in step 4 under an inert gas atmosphere, sintering to obtain sintered material F, cooling and crushing the screen to obtain lithium iron manganese phosphate. The method is simple, low-cost, and suitable for industrialization.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for preparing lithium manganese iron phosphate. Background Art

[0002] In recent years, lithium-ion batteries have ushered in huge development opportunities. Lithium iron phosphate batteries are regarded as a potential development route for lithium-ion batteries due to their high safety, good cycle stability and environmental friendliness. However, according to reports, the energy density of lithium iron phosphate has approached the theoretical mass production limit and has been maintained in the range of 160-165Wh / kg for more than two years. Olivine-type lithium manganese iron phosphate material is based on the development of lithium iron phosphate and lithium manganese phosphate. The theoretical performance specific capacity of the three is relatively similar (170mAh / g). 2+ It can broaden the diffusion and channel of lithium ions to a certain extent. By utilizing the synergistic effect of the two, the energy density can be increased by more than 20% with the same capacity in theory. Due to the introduction of manganese, the performance of lithium iron phosphate battery is also better at low temperature. Compared with lithium iron phosphate battery, lithium iron phosphate battery has higher energy density, better stability, longer cycle life and high safety. At the same time, under the condition of abundant manganese resources in the world, its material cost can be reduced by 10% compared with lithium iron phosphate, which is more cost-effective.

[0003] Lithium iron manganese phosphate has significant advantages and has attracted much attention from the industry. According to industry analysis, the global market size and market demand for lithium iron manganese phosphate in 2021 will be 310 million yuan and 5,000 tons respectively, with rapid year-on-year growth and continued growth year by year. By 2025, it is expected to reach 9.2 billion yuan and 154,000 tons, with a penetration rate of more than 15% in various industries. Therefore, the preparation of lithium iron manganese phosphate is very important for improving battery performance, ensuring safety in use, and promoting the development of the new energy industry. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a synthesis method with simple process, low cost and time saving, which has great industrial application prospects. In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: a preparation method of lithium manganese iron phosphate, comprising the following steps:

[0005] Step 1: Put ferromanganese oxalate, lithium dihydrogen phosphate, lithium carbonate, sucrose and magnesium hydroxide into the equipment in sequence, add anhydrous ethanol and then ball-mill to obtain slurry A;

[0006] Step 2: Filter the slurry A in step 1 through a 100-mesh drying net, and obtain powder B after spray drying;

[0007] Step 3: placing the powder B in step 2 under an inert gas atmosphere and sintering to obtain a sintered material C;

[0008] Step 4: ball-milling the sintered material C, polyvinyl alcohol and anhydrous ethanol in step 3 to obtain slurry D;

[0009] Step 5: spray-dry the slurry D in step 4 to obtain powder E;

[0010] Step 6: Place the powder E in step 4 under an inert gas atmosphere, sinter to obtain sintered material F, and cool, crush, and screen to obtain lithium iron manganese phosphate.

[0011] Furthermore, in step 1, 55-70% manganese iron oxalate, 25-40% lithium dihydrogen phosphate, 0.7-1.2% lithium carbonate, 1-2% sucrose, and 1-2% magnesium hydroxide are included; and in step 3, 0.1-0.3% polyvinyl alcohol is included.

[0012] Furthermore, the mass volume ratio of ferromanganese oxalate to anhydrous ethanol in step 1 is 1:1 (g / ml); the volume ratio of anhydrous ethanol in step 1 to anhydrous ethanol in step 4 is 1:1.

[0013] Furthermore, the ball milling speed of step 1 is 30 Hz and the time is 2-4 hours.

[0014] Furthermore, the spray drying temperature in step 2 is 200-300°C.

[0015] Furthermore, the sintering temperature of step 3 is 450-600° C., the time is 16-20 h, and the inert gas of step 3 is nitrogen with a flow rate of 0.5 L / h.

[0016] Furthermore, the ball milling speed in step 4 is 30 Hz and the time is 2-4 hours.

[0017] Furthermore, the spray drying temperature in step 5 is 200-300°C.

[0018] Furthermore, the sintering temperature of step 6 is 450-650° C., the time is 16-20 h, and the inert gas of step 6 is nitrogen with a flow rate of 0.5 L / h.

[0019] Furthermore, the sieve in step 6 is 300 mesh.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The lithium manganese iron phosphate material of the present invention is similar to lithium iron phosphate and has a relatively low cost.

[0022] 2. The lithium manganese iron phosphate of the present invention has been significantly improved in terms of energy density, low temperature performance, safety and cost. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Example 1

[0025] The present invention provides a method for preparing lithium manganese iron phosphate, comprising the following steps:

[0026] (1) Weigh 500 g of ferromanganese oxalate, 291.45 g of lithium dihydrogen phosphate, 8.2 g of lithium carbonate, 13.81 g of sucrose, and 1.64 g of magnesium hydroxide, put them into a ball mill in sequence, add 500 ml of anhydrous ethanol, and ball mill at 30 Hz for 3 hours.

[0027] (2) Filter the slurry through a 100-mesh drying net. Open the spray drying tower, heat it to 250°C, and spray dry the material.

[0028] (3) The spray-dried material is placed in a sagger and enters an atmosphere furnace with a temperature curve (RT→270min→450℃→180min→450℃→50min→600℃-60min-600℃-200min-50℃). Nitrogen is introduced throughout the process (flow rate 0.5L / H).

[0029] (4) After cooling to room temperature, 13.81 g of polyvinyl alcohol was added to the ball mill, followed by 500 ml of anhydrous ethanol, and the mixture was ball milled at 30 Hz for 3 hours.

[0030] (5) Filter the slurry through a 100-mesh drying net. Open the spray drying tower, heat it to 250°C, and spray dry the material.

[0031] (6) The spray-dried material is placed in a sagger and enters an atmosphere furnace with a temperature curve (RT→270min→450℃→180min→450℃→70min→650℃→480min→650℃→200min→50℃). Nitrogen protection (flow rate 0.5L / H) is also introduced; the material is cooled to room temperature and crushed to obtain lithium manganese iron phosphate after screening with a 300-mesh sieve.

[0032] Example 2

[0033] (7) Weigh 456 g of ferromanganese oxalate, 207.22 g of lithium dihydrogen phosphate, 5.8 g of lithium carbonate, 8.21 g of sucrose, and 0.83 g of magnesium hydroxide, and put them into a ball mill in sequence. Pour in 456 ml of anhydrous ethanol, and mill at 30 Hz for 3 hours.

[0034] (8) Filter the slurry through a 100-mesh drying net. Open the spray drying tower, heat it to 250°C, and spray dry the material.

[0035] (9) The spray-dried material is placed in a sagger and placed in an atmosphere furnace with a temperature curve (RT→270min→450℃→180min→450℃→50min→600℃-60min-600℃-200min-50℃). Nitrogen is introduced throughout the process (flow rate 0.5L / H).

[0036] (10) After cooling to room temperature, 8.21 g of polyvinyl alcohol was added to the ball mill, followed by 456 ml of anhydrous ethanol. The mixture was ball milled at 30 Hz for 3 hours.

[0037] (11) Filter the slurry through a 100-mesh screen. Open the spray drying tower, heat it to 250°C, and spray dry the material.

[0038] (12) The spray-dried material was placed in a sagger and entered into an atmosphere furnace with a temperature curve (RT→270min→450℃→180min→450℃→70min→650℃→480min→650℃→200min→50℃). Nitrogen protection (flow rate 0.5L / H) was also introduced. The material was cooled to room temperature and crushed to obtain lithium manganese iron phosphate after screening with a 300-mesh sieve.

[0039] Example 3

[0040] (13) Weigh 580 g of ferromanganese oxalate, 331.56.45 g of lithium dihydrogen phosphate, 9.95 g of lithium carbonate, 16.58 g of sucrose, and 2.49 g of magnesium hydroxide, put them into a ball mill in sequence, add 580 ml of anhydrous ethanol, and mill at 30 Hz for 3 hours.

[0041] (14) Filter the slurry through a 100-mesh screen. Open the spray drying tower, heat it to 250°C, and spray dry the material.

[0042] (15) The spray-dried material is placed in a sagger and placed in an atmosphere furnace with a temperature curve (RT→270min→450°C→180min→450°C→50min→600°C-60min-600°C-200min-50°C). Nitrogen is introduced throughout the process (flow rate 0.5L / H).

[0043] (16) After cooling to room temperature, 16.58 g of polyvinyl alcohol was added to the ball mill, followed by 580 ml of anhydrous ethanol. The mixture was ball milled at 30 Hz for 3 h.

[0044] (17) Filter the slurry through a 100-mesh screen. Open the spray drying tower, heat it to 250°C, and spray dry the material.

[0045] (18) The spray-dried material was placed in a sagger and entered into an atmosphere furnace with a temperature curve (RT→270min→450℃→180min→450℃→70min→650℃→480min→650℃→200min→50℃). Nitrogen protection (flow rate 0.5L / H) was also introduced. The material was cooled to room temperature and crushed to obtain lithium iron manganese phosphate after screening with a 300-mesh sieve.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing lithium manganese iron phosphate, characterized in that: The steps include: Step 1: Put ferromanganese oxalate, lithium dihydrogen phosphate, lithium carbonate, sucrose and magnesium hydroxide into the equipment in sequence, add anhydrous ethanol and then ball-mill to obtain slurry A; Step 2: Filter the slurry A in step 1 through a 100-mesh drying net, and obtain powder B after spray drying; Step 3: placing the powder B in step 2 under an inert gas atmosphere and sintering to obtain a sintered material C; Step 4: ball-milling the sintered material C, polyvinyl alcohol and anhydrous ethanol in step 3 to obtain slurry D; Step 5: spray-dry the slurry D in step 4 to obtain powder E; Step 6: Place the powder E in step 4 under an inert gas atmosphere, sinter to obtain sintered material F, and cool, crush, and screen to obtain lithium iron manganese phosphate.

2. The method for preparing lithium iron manganese phosphate according to claim 1, characterized in that: Calculated by mass fraction, the step 1 comprises 55-70% ferromanganese oxalate, 25-40% lithium dihydrogen phosphate, 0.7-1.2% lithium carbonate, 1-2% sucrose, and 1-2% magnesium hydroxide; and the step 3 comprises 0.1-0.3% polyvinyl alcohol.

3. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The mass volume ratio of ferromanganese oxalate to anhydrous ethanol in step 1 is 1:1 (g / ml); the volume ratio of anhydrous ethanol in step 1 to anhydrous ethanol in step 4 is 1:

1.

4. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The ball milling speed of step 1 is 30 Hz and the time is 2-4 hours.

5. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The spray drying temperature in step 2 is 200-300°C.

6. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The sintering temperature of step 3 is 450-600° C., the time is 16-20 h, and the inert gas of step 3 is nitrogen with a flow rate of 0.5 L / h.

7. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The ball milling speed of step 4 is 30 Hz and the time is 2-4 hours.

8. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The spray drying temperature in step 5 is 200-300°C.

9. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The sintering temperature of step 6 is 450-650° C., the time is 16-20 h, and the inert gas of step 6 is nitrogen with a flow rate of 0.5 L / h.

10. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The sieve in step 6 is 300 mesh.