CN101359756A - A kind of recovery method of lithium iron phosphate cathode material in lithium ion battery waste - Google Patents

Abstract

The invention relates to a method for recovering a lithium iron phosphate anode material in lithium ion battery scraps, comprising: roasting the scraps in the atmosphere of inert gases at a temperature of between 450 and 600 DEG C for 2 to 5 hours, wherein, the method also includes: adding the powdered products into an ethanol solution of soluble ferric salt for mixing, drying the mixture, then roasting the mixture in the atmosphere of inert gases at a temperature of between 300 and 500 DEG C for 2 to 5 hours, and obtaining the lithium iron phosphate anode material through recovery. The recovery method can be used to obtain the lithium iron phosphate anode material with rather high tap density, so the lithium ion secondary battery made by adopting the anode material has rather high capacity.

Description

A kind of recovery method of lithium iron phosphate cathode material in lithium ion battery waste

technical field

The invention relates to a recovery method of lithium iron phosphate cathode material in lithium ion battery waste.

Background technique

At present, lithium-ion secondary batteries with lithium iron phosphate as the positive electrode material have gradually entered the market due to their low cost and good safety performance, and have begun to be widely used in power batteries for notebook computers, power tools and electric vehicles. With the application of lithium-ion secondary batteries using lithium iron phosphate as the positive electrode material, the output of batteries is increasing rapidly, and a large amount of waste slurry and waste pole pieces will be produced in the process of preparing batteries. Therefore, in order to recycle and reuse materials, save costs and protect the environment, it is very necessary to recycle lithium iron phosphate in waste.

CN1585180A discloses a method for recovering positive electrode residues of lithium-ion secondary batteries. The method heat-treats the leftover scraps of positive electrodes produced during the preparation of lithium-ion secondary batteries, removes the adhesive between the aluminum foil substrate and the positive electrode material, and uses a mechanical method to separate the aluminum foil substrate from the positive electrode material; or heat-treated positive electrodes The pole piece is placed in distilled water, and the positive electrode material attached to the aluminum foil substrate is separated from the aluminum foil substrate by ultrasonic vibration or mechanical stirring at a certain temperature, and then the positive electrode material is separated, and the positive electrode material that can be used directly is obtained after drying. . However, the capacity of the lithium ion secondary battery made of the positive electrode material recovered by this method is relatively low.

CN1953269A discloses a kind of recovery method of waste lithium-ion battery, described method is that battery discharges electricity completely, separates the positive pole of battery, negative pole and separator; It is characterized in that comprising the following steps: (1) the positive pole that separates is cut into fragments, Place in N-methylpyrrolidone solution, stir at 50-100°C for 2-5 hours, separate the aluminum foil, filter out the positive electrode active material, and dry it in vacuum at 100-140°C to obtain a crude positive electrode active material; (2) Mix the crude positive active material product described in step (1) with Li ₂ CO ₃ by mechanical ball milling, calcining in air or oxygen atmosphere at a temperature of 700-950°C for 10-24 hours, cooling to room temperature, and grinding to obtain LiCoO ₂ , the mass ratio of the raw positive electrode active material to Li ₂ CO ₃ is 3-5:1. In this way, the positive electrode active material of the lithium-ion battery can be recovered. However, the capacity of the lithium ion secondary battery made of the positive electrode material recovered by this method is still low.

Contents of the invention

The object of the present invention is to overcome the defect that the positive electrode material obtained in the recycling method of the above-mentioned prior art makes the capacity of the lithium ion secondary battery lower, and provides a kind of recovery lithium ion battery that can obtain the higher capacity of the lithium ion secondary battery Method for lithium iron phosphate cathode material from waste.

The invention provides a method for recovering lithium iron phosphate positive electrode materials from waste materials of lithium ion batteries. The method comprises: baking the waste materials at 450-600° C. for 2-5 hours in an atmosphere of an inert gas, wherein the method also includes: The method includes: adding the baked powder product into an ethanol solution of soluble iron salt, mixing, drying, and then roasting at 300-500° C. for 2-5 hours in an inert gas atmosphere to recover the lithium iron phosphate positive electrode material.

By adopting the recovery method provided by the invention, the tap density of the obtained lithium iron phosphate cathode material is relatively high, so that the capacity of the lithium ion secondary battery made of the cathode material is relatively high. The recycling and reuse of lithium iron phosphate raw materials is realized, which can save costs and have environmental protection benefits.

Description of drawings

Fig. 1 is the XRD diffractogram of the lithium iron phosphate cathode material that embodiment 1 obtains;

2 is a scanning electron microscope image of the lithium iron phosphate cathode material obtained in Example 1.

Detailed ways

The method for recovering lithium iron phosphate positive electrode material in lithium ion battery waste provided by the present invention comprises: baking the waste at 450-600° C. for 2-5 hours in an inert gas atmosphere, wherein the method also includes: The powder product obtained by roasting is added to the ethanol solution of the soluble iron salt, mixed, dried, and then calcined at 300-500° C. for 2-5 hours in an inert gas atmosphere, and the lithium iron phosphate cathode material is recovered.

According to the recovery method provided by the present invention, the waste material includes waste slurry and spent pole pieces, the waste slurry includes various lithium iron phosphate positive electrode slurries prepared in an oil-based or water-based manner, and the waste pole pieces include waste produced during the production process. Waste pole pieces, scraps and waste pole pieces dismantled from scrap batteries. When there are waste pole pieces among the waste materials to be recycled, after the above-mentioned baking, use a sieve to separate the material peeled off from the current collector, and sort out the current collector at the same time, so that the collector can also be recycled. When the waste to be recovered is waste slurry, after the above-mentioned baking, the following steps are directly carried out without sieving.

According to the recovery method provided by the present invention, in preferred cases, the concentration of the soluble iron salt in the ethanol solution of the soluble iron salt is 0.01-0.2mol/L, preferably 0.05-0.15mol/L, and the soluble iron salt can be Various water-soluble salts of ferrous iron and/or ferric iron, such as one or more of sulfate, chloride and nitrate.

According to the recovery method provided by the present invention, in preferred cases, the method also includes mixing the obtained lithium iron phosphate positive electrode material with lithium source and/or phosphorus source, drying, and drying at 550- Baking at 750°C for 3-10 hours. Preferably, the obtained lithium iron phosphate positive electrode material is mixed with lithium source and/or phosphorus source by ball milling, and the medium of ball milling mixing can be various media known to those skilled in the art, such as absolute ethanol, acetone and one or more of deionized water.

According to the recovery method provided by the present invention, preferably, the molar amount of the lithium source or phosphorus source used is 0.1-3%, preferably 0.5-2.0%, of the molar amount of the obtained lithium iron phosphate.

According to the recovery method provided by the present invention, the lithium source can be a variety of lithium sources known to those skilled in the art for solid phase synthesis of lithium iron phosphate, such as lithium carbonate, lithium hydroxide, lithium oxalate, lithium acetate, fluoride One or more of lithium, lithium bromide, lithium iodide and lithium dihydrogen phosphate; the phosphorus source can be a variety of phosphorus sources known to those skilled in the art for solid-phase synthesis of lithium iron phosphate, such as ammonium phosphate, One or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate and lithium dihydrogen phosphate.

According to the recovery method provided by the present invention, preferably, the method further includes mixing the obtained lithium iron phosphate positive electrode material with a carbon source, drying, and roasting at 550-750° C. under an inert gas atmosphere, The time of roasting is 3-10 hours.

According to the recovery method provided by the present invention, preferably, the method further includes, before drying and roasting, mixing the carbon source with the obtained mixture of the obtained lithium iron phosphate cathode material and the lithium source and/or the phosphorus source.

According to the recovery method provided by the present invention, in preferred cases, the molar number of the carbon source used is 0.1-3% of the molar number of the obtained lithium iron phosphate, and the carbon source is carbon black, acetylene black, graphite and One or more carbohydrates. The carbon-coated lithium iron phosphate positive electrode material can improve the conductivity of the lithium iron phosphate positive electrode material.

According to the recovery method provided by the present invention, the inert gas is various inert gases known to those skilled in the art, such as one or more of nitrogen, helium, neon, argon, krypton, xenon and radon .

According to various preferred embodiments of the present invention, aiming at the disadvantages of poor electrical performance and low density of lithium iron phosphate itself, the various disadvantages of lithium iron phosphate are solved in the recycling process, so as to achieve the goal of reuse. Various standards, can be directly used as positive electrode active material of lithium ion secondary battery.

The present invention will be described in more detail below by way of examples.

Example 1

Take 10kg of lithium iron phosphate positive electrode waste slurry, put it into a material tray, put it into a high-temperature resistance furnace under a nitrogen atmosphere, bake it at a furnace temperature of 450°C for 5 hours, and then cool it with the furnace. Add the cooled material to the ferric nitrate ethanol solution whose concentration of ferric nitrate is 0.15mol/L and stir. Baking at 350° C. for 5 hours, and then cooling in the furnace to obtain the lithium iron phosphate cathode material.

The product was tested with a Japanese Rigaku D/MAX2200PC X-ray diffractometer, and the obtained diffraction pattern is shown in Figure 1. It can be seen from this figure that the diffraction peaks tested in the upper part are consistent with the standard lithium iron phosphate in the lower part. The diffraction peaks are basically the same, and the main peak intensity is higher, and the half-peak width (B value is 0.178) is narrower, indicating that its crystal is very complete. Adopt scanning electron microscope (the KYKY2800 type that Beijing Chinese Academy of Sciences instrument factory produces) to this product to observe, the scanning electron microscope picture that obtains is shown in Figure 2, can find out from this figure, particle is more uniform, and surface is smoother, and single particle Relatively dense.

Example 2

Take 10kg of lithium iron phosphate waste slurry, put it into a material tray, put it into a high-temperature resistance furnace under a nitrogen atmosphere, bake it at a furnace temperature of 450°C for 5 hours, and then cool it with the furnace. Add the cooled material to the ferric nitrate ethanol solution whose concentration of ferric nitrate is 0.2mol/L and stir. After the ethanol volatilizes, put it into a tray and put it into a high-temperature resistance furnace under a nitrogen atmosphere. Bake at 350°C for 5h, then cool with the furnace.

Then 5kg of the obtained material is added to the ball milling tank, and 70.6g of lithium carbonate and 109.4g of ammonium dihydrogen phosphate are weighed respectively according to 3% of the molar number of 5kg lithium iron phosphate, and all are added to the ball milling tank, and then alcohol and pickaxe are added. Balls, after ball milling for 2 hours, take out the evenly mixed material and dry it at 60°C. Finally, put the dried material into a high-temperature resistance furnace under a nitrogen atmosphere, bake it at a temperature of 650°C for 10 hours, and then cool it down to room temperature with the furnace to obtain a lithium iron phosphate cathode material.

Using the same X-ray diffractometer and scanning electron microscope used in Example 1 to test the obtained lithium iron phosphate positive electrode material, the obtained XRD diffraction pattern is basically similar to Figure 1, and the obtained scanning electron microscope pattern is similar to that shown in Figure 1. Figure 2 is basically similar. The diffraction peaks of the tested XRD diffraction patterns are all lithium iron phosphate diffraction peaks, and the peak intensity is above 1340, and the half-peak width B value is below 0.18, indicating that the crystal form is very complete. It can be seen from the scanning electron microscope image that the obtained lithium iron phosphate cathode material has a smooth surface, uniform particles, and relatively dense individual particles.

Example 3

Take 10 kg of lithium iron phosphate cathode sheets scrapped in production, put them into a material tray, put them into a high-temperature resistance furnace under a nitrogen atmosphere, bake them at a furnace temperature of 550°C for 4 hours, and then cool with the furnace. Put the baked pole piece on a sieve with a mesh of 5mm, knead the pole piece, and shake the sieve from time to time to completely separate the material and the current collector. Add the obtained powder into the ferric nitrate ethanol solution whose concentration of ferric nitrate is 0.1mol/L and stir. Bake at 400°C for 4 hours, then cool with the furnace.

Then 5kg of the obtained material is added to the ball milling tank, and 26g of lithium hydroxide monohydrate, 84.3g of diammonium hydrogen phosphate and 7.6g of acetylene black are weighed respectively according to 2% of the molar number of 5kg lithium iron phosphate, and all are added to the ball milling tank Then add alcohol and pick balls, take out the evenly mixed material after ball milling for 2 hours, and dry it at 60°C. Finally, put the dried material into a high-temperature resistance furnace under a nitrogen atmosphere, bake it at a temperature of 750° C. for 6 hours, and then cool it to room temperature with the furnace to obtain a lithium iron phosphate cathode material.

Using the same X-ray diffractometer and scanning electron microscope used in Example 1 to test the obtained lithium iron phosphate positive electrode material, the obtained XRD diffraction pattern is basically similar to Figure 1, and the obtained scanning electron microscope pattern is similar to that shown in Figure 1. Figure 2 is basically similar. The diffraction peaks of the tested XRD diffraction patterns are all lithium iron phosphate diffraction peaks, and the peak intensity is above 1340, and the half-peak width B value is below 0.18, indicating that the crystal form is very complete. It can be seen from the scanning electron microscope image that the obtained lithium iron phosphate cathode material has a smooth surface, uniform particles, and relatively dense individual particles.

Example 4

Take 10kg of lithium iron phosphate cathode sheets scrapped in production, put them into a material tray, put them into a high-temperature resistance furnace under a nitrogen atmosphere, bake them at a furnace temperature of 600°C for 2 hours, and then cool them with the furnace. Put the baked electrode piece on a sieve with a mesh of 5mm, knead the electrode piece, and shake the sieve from time to time to completely separate the material on the current collector from the current collector. The obtained powder is added to the ethanol solution of ferric chloride whose concentration of ferric chloride is 0.05mol/L and stirred. After the ethanol is volatilized, put it into a tray, put it into a high-temperature resistance furnace under nitrogen atmosphere, and Bake at 500°C for 4 hours, then cool with the furnace.

Then add 5 kg of the obtained material into the ball milling tank, weigh 32.94 g of lithium dihydrogen phosphate according to 1% of the molar number of 5 kg of lithium iron phosphate, add it to the ball milling tank, add alcohol and pick balls, and take out after ball milling for 2 hours Mix the material evenly and dry it at 60°C. Finally, put the dried material into a high-temperature resistance furnace under a nitrogen atmosphere, bake it at a temperature of 600°C for 4 hours, and then cool it down to room temperature with the furnace to obtain a lithium iron phosphate cathode material.

Using the same X-ray diffractometer and scanning electron microscope used in Example 1 to test the obtained lithium iron phosphate positive electrode material, the obtained XRD diffraction pattern is basically similar to Figure 1, and the obtained scanning electron microscope pattern is similar to that shown in Figure 1. Figure 2 is basically similar. The diffraction peaks of the tested XRD diffraction patterns are all lithium iron phosphate diffraction peaks, and the peak intensity is above 1340, and the half-peak width B value is below 0.18, indicating that the crystal form is very complete. It can be seen from the scanning electron microscope image that the obtained lithium iron phosphate cathode material has a smooth surface, uniform particles, and relatively dense individual particles.

Comparative example 1

Take 10kg of lithium iron phosphate waste slurry, put it into a material tray, put it into a high-temperature resistance furnace under a nitrogen atmosphere, bake it at a furnace temperature of 450°C for 5 hours, and then cool it with the furnace. Then 5kg of the obtained material is added to the ball milling tank, and 26g of lithium hydroxide monohydrate, 84.3g of diammonium hydrogen phosphate, and 7.6g of acetylene black are all added to the ball milling tank according to 2% of the molar number of 5kg lithium iron phosphate. , then add alcohol and pick balls, ball mill for 2 hours, take out the evenly mixed material, and dry it at 60°C. Finally, put the dried material into a high-temperature resistance furnace under a nitrogen atmosphere, bake it at a temperature of 650°C for 10 hours, and then cool it down to room temperature with the furnace to obtain a lithium iron phosphate cathode material.

Performance Testing

1. Test density

The tap density of the samples was tested with a self-made stainless steel tap density tester. The cylinder of the tester is divided into two parts, the test cylinder and the auxiliary cylinder, wherein the volume of the test cylinder is 50cm ³ and the mass is 165.2g.

During the test, put the sample into the cylinder of the tester, lift the entire cylinder vertically up to a height of 30cm, then let it fall freely, and repeat 40 times, and then remove the auxiliary cover on the test cylinder. Put the cylinder in a horizontal position, use a scraper to scrape off the excess material on the test cylinder at an angle of 45 degrees, and remove all the powder on the surface of the cylinder, weigh it, and then deduct the mass of the cylinder itself, that is The mass M of the powder is obtained, and the tap density is M/50 (g/cm ³ ), each sample is tested three times, and the average value is taken.

The densities of the lithium iron phosphate cathode materials recovered in Examples 1-4 and Comparative Example 1 were tested according to the above method, and the results are listed in Table 1.

Table 1

First time (g/cm ³ ) Second time (g/cm ³ ) The third time (g/cm ³ ) Average(g/cm ³ ) Example 1 1.62 1.61 1.62 1.62 Example 2 1.60 1.61 1.62 1.61 Example 3 1.66 1.68 1.68 1.67 Example 4 1.64 1.65 1.64 1.64 Comparative example 1 1.09 1.08 1.08 1.08

2. Test battery capacity

The lithium iron phosphate cathode material prepared in Examples 1-4 and Comparative Example 1 was mixed with acetylene black as a conductive agent and 60% polytetrafluoroethylene emulsion as a binder in a mass ratio of 80:15:5 . Use absolute ethanol as a dispersant, ultrasonically oscillate for 15 minutes to mix them evenly, make a disc with an area of about 1cm ² and a thickness of less than 1mm, and press it on the current collector aluminum foil to form a positive electrode sheet, vacuum at 120°C Dry 8h.

Then the metal lithium sheet is used as the negative electrode, the polypropylene microporous membrane (2300) is used as the diaphragm, and the electrolyte is a mixed solution of lithium hexafluorophosphate in ethylene carbonate+diethyl carbonate+dimethyl carbonate (volume ratio is 1:1:1) , wherein the concentration of lithium hexafluorophosphate is 1mol/L, installed in an argon-filled glove box to form a 2032-type button cell, and make ten button cells for each positive electrode material. The charge and discharge tests were carried out at a charge and discharge rate of 0.05, and the voltage range was 2.5-3.8v.

The average discharge specific capacity and average initial charge-discharge efficiency of the button batteries made of the positive electrode materials of Examples 1-4 and Comparative Example 1 were tested respectively, and the results are listed in Table 2.

Table 2

Cathode material Average discharge specific capacity (mAh/g) Average first charge and discharge efficiency (%) Example 1 147.9 90.2 Example 2 150.6 92.7 Example 3 153.8 94.9 Example 4 149.2 93.1 Comparative example 1 119.9 87.5

The discharge specific capacity calculation formula is:

Discharge specific capacity = discharge capacity (mA) / mass of sample (g)

The formula for calculating the first charge and discharge efficiency is:

The first charge and discharge efficiency = discharge capacity (mA) / charge capacity (mA) × 100%

It can be seen from the data in Table 1 that the density of the lithium iron phosphate positive electrode material obtained in Examples 1-4 is higher than that of the lithium iron phosphate positive electrode material obtained in Comparative Example 1.

It can be seen from the data in Table 2 that the lithium iron phosphate positive electrode material obtained in Examples 1-4 makes the capacity of the lithium ion secondary battery much larger than that of Comparative Example 1.

Therefore, the density of the lithium iron phosphate positive electrode material obtained by the recovery method of the present invention is very large, so the capacity of the lithium ion secondary battery obtained by the positive electrode material is also very large, and it can be directly used as the positive electrode material to make lithium ion secondary batteries. secondary battery.

Claims (10)

1. A method for recovering lithium iron phosphate cathode materials from lithium ion battery waste, the method comprising: baking the waste at 450-600°C for 2-5 hours in an inert gas atmosphere, characterized in that the The method also includes adding the baked powder product into an ethanol solution of soluble iron salt, mixing, drying, and then firing at 300-500° C. for 2-5 hours in an inert gas atmosphere to recover the lithium iron phosphate cathode material. 2. The method according to claim 1, wherein the concentration of the soluble iron salt in the ethanol solution of the soluble iron salt is 0.01-0.2mol/L, and the soluble iron salt is ferrous and/or ferric One or more of sulfates, chlorides and nitrates. 3. The method according to claim 2, wherein the concentration of the soluble iron salt in the ethanol solution of the soluble iron salt is 0.05-0.15mol/L. 4. The method according to claim 1, wherein the method further comprises, mixing the obtained lithium iron phosphate positive electrode material with a lithium source and/or a phosphorus source, drying, and drying at 550- Calcined at 750°C. 5. The method according to claim 4, wherein the molar amount of the lithium source or phosphorus source used is 0.1-3% of the molar amount of the obtained lithium iron phosphate. 6. The method according to claim 5, wherein the molar amount of the lithium source or phosphorus source is 0.5-2.0% of the molar amount of the obtained lithium iron phosphate. 7. The method according to claim 4, 5 or 6, wherein the lithium source is lithium carbonate, lithium hydroxide, lithium oxalate, lithium acetate, lithium fluoride, lithium bromide, lithium iodide and lithium dihydrogen phosphate One or more of them; the phosphorus source is one or more of ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate and lithium dihydrogen phosphate. 8. The method according to claim 1, wherein the method further comprises mixing the obtained lithium iron phosphate cathode material with a carbon source, drying, and firing at 550-750°C under an atmosphere of an inert gas; The molar amount of the carbon source used is 0.1-3% of the molar amount of the obtained lithium iron phosphate, and the carbon source is one or more of carbon black, acetylene black, graphite and carbohydrates. 9. The method according to claim 4, wherein the method further comprises, before drying and roasting, mixing the carbon source with the obtained lithium iron phosphate cathode material and the mixture of lithium source and/or phosphorus source, The molar amount of the carbon source used is 0.1-3% of the molar amount of the obtained lithium iron phosphate, and the carbon source is one or more of carbon black, acetylene black, graphite and carbohydrates. 10. The method according to claim 1 or 4, wherein the inert gas is one or more of nitrogen, helium, neon, argon, krypton, xenon and radon.

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