CN114538405A - Method for preparing lithium iron phosphate from waste lithium iron phosphate anode material - Google Patents
Method for preparing lithium iron phosphate from waste lithium iron phosphate anode material Download PDFInfo
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- CN114538405A CN114538405A CN202210332140.3A CN202210332140A CN114538405A CN 114538405 A CN114538405 A CN 114538405A CN 202210332140 A CN202210332140 A CN 202210332140A CN 114538405 A CN114538405 A CN 114538405A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/84—Recycling of batteries or fuel cells
Abstract
The invention provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, which comprises the following steps: (1) sequentially carrying out alkaline leaching separation on the lithium iron phosphate waste positive electrode material by using an aluminum foil and ball milling to obtain a granular material; sequentially soaking and separating the binder and roasting and separating carbon in the granular material by using an organic solvent to obtain a mixed material containing phosphorus, iron and lithium; (2) carrying out acid leaching on the mixed material in an oxalic acid solution, and carrying out solid-liquid separation to obtain a leaching solution and a dihydrate ferric oxalate precipitate; (3) mixing sodium carbonate with the leaching solution, precipitating lithium and carrying out solid-liquid separation to obtain lithium carbonate; (4) and (3) mixing the ferric oxalate dihydrate precipitate in the step (2) and the lithium carbonate and the phosphorus source in the step (3), and calcining to obtain the lithium iron phosphate. The method can obtain the lithium iron phosphate product with high purity and high recovery rate, has stable and excellent electrochemical performance, and can be directly applied to the application of the anode material in the battery.
Description
Technical Field
The invention relates to the field of lithium ion waste battery recovery, in particular to a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material.
Background
The lithium ion battery has the advantages of high working voltage, high energy density, small self-discharge, long service life, no memory effect, etc., and is widely used for various applicationsIn an electronic device. Unlike other chemical power systems, the cathode and anode materials of lithium batteries are constantly being developed, and the lithium battery, taking the cathode as an example, is initially commercialized and adopts layered LiCoO2Thereafter, spinel LiMn is used2O4And layered LiNi/Co/MnO3And the like. Lithium ion batteries are expanding from the traditional portable battery field to the fields of electric tools, electric bicycles, hybrid electric vehicles, and pure electric vehicles.
In the power cell systems currently under investigation, LiFePO4The battery has the advantages of long cycle life, good safety performance, environmental friendliness, low price and the like, and is considered to be one of the most ideal positive electrode materials of the power battery.
With the rapid development of hybrid electric vehicles and electric vehicles, the output of power lithium ion batteries will increase substantially. When the service life of the power lithium ion battery is over, a large amount of waste power lithium ion batteries must be generated, so that LiFePO4The recovery technology of the lithium ion battery has great practical and economic values.
At present, the following methods are mainly used for recovering waste materials of the lithium iron phosphate anode.
CN101383441A discloses a comprehensive recovery method of waste lithium iron phosphate positive electrode pieces, which comprises separating aluminum foil by mechanical separation or ultrasonic oscillation to obtain a mixture of lithium iron phosphate, conductive agent and binder residue. Baking the mixture at 80-150 deg.C for 8-24 h; and (3) grinding and grading the baked material, and controlling the particle size to be not more than 15 mu m. And obtaining the lithium iron phosphate anode recovery material. The method does not consider the influence of a residual binder and a conductive agent of the mixture on the electrochemical performance of the material, and the obtained lithium iron phosphate material has lower cycle performance and electrochemical performance.
CN104362408A discloses a method for recycling lithium iron phosphate fertilizer in the manufacturing process of lithium iron phosphate batteries, wherein the method comprises the steps of placing the recycled pole piece in a muffle furnace for baking at the high temperature of 400-600 ℃ for 2-3h, and separating active substance lithium iron phosphate and conductive agent from an aluminum foil; then baking the mixture for 4 to 6 hours at the high temperature of 650-800 ℃ in a muffle furnace, and screening to obtain lithium iron phosphate powder; washing the lithium iron phosphate powder with deionized water, and adding ethanol to prepare a suspension after washing; mixing soluble lithium salt, iron salt and phosphate in proportion in an ethanol solution, and drying in vacuum at the temperature of 140 ℃ under the temperature of 120-; roasting for 3-6h at the temperature of 850 ℃ under the protection of an inert atmosphere and 650-. The method directly repairs the lithium iron phosphate anode material, is difficult to obtain a stable and qualified anode product, and has obviously inferior charge and discharge performance to the quality lithium iron phosphate material.
Therefore, a method for directly preparing lithium iron phosphate from waste lithium iron phosphate cathode materials needs to be developed.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a method for preparing lithium iron phosphate from waste and old positive electrode materials of lithium iron phosphate, which is simple to recover, can directly synthesize raw materials for preparing the lithium iron phosphate after treatment, and can synthesize battery-grade lithium iron phosphate by mixing and calcining the raw materials with phosphorus salt according to a certain proportion. And the method has high recovery efficiency and high recovery purity, and is suitable for large-scale industrial production.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, which comprises the following steps:
(1) sequentially carrying out alkaline leaching separation on the lithium iron phosphate waste positive electrode material by using an aluminum foil and ball milling to obtain a granular material; sequentially soaking the granular material in an organic solvent to separate the binder and roasting to separate carbon to obtain a mixed material containing phosphorus, iron and lithium;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution, and carrying out solid-liquid separation to obtain a leaching solution and a dihydrate ferric oxalate precipitate;
(3) mixing sodium carbonate with the leaching solution, precipitating lithium and carrying out solid-liquid separation to obtain lithium carbonate;
(4) and (3) mixing the ferric oxalate dihydrate precipitate in the step (2) and the lithium carbonate and the phosphorus source in the step (3), and calcining to obtain the lithium iron phosphate.
The principle of the method of the invention is as follows: after aluminum foil separation, ball milling, binder separation and carbon roasting separation, the lithium iron phosphate battery positive electrode material is subjected to leaching reaction in an oxalic acid solution to generate indissolvable ferric oxalate, and the equation is as follows:
LiFePO4+H2C2O4·2H2O→FeC2O4·2H2O+LiH2PO4
the ferric oxalate can be used as an iron source for synthesizing lithium iron phosphate, sodium carbonate is continuously added into leachate after reaction, and lithium carbonate precipitate can be obtained, wherein the reaction equation is as follows:
2LiH2PO4+3Na2CO3＝Li2CO3+2Na3PO4+2H2O+2CO2
lithium carbonate obtained after the reaction can be used as a lithium source for synthesizing lithium iron phosphate. The battery-grade lithium iron phosphate can be obtained by mixing lithium carbonate, ferric oxalate and a phosphorus source according to a certain proportion and then calcining, the recovery of the battery-grade lithium iron phosphate is realized, the operation is simple, the recovery efficiency and the purity are high, and the method is suitable for large-scale industrial production.
Preferably, the alkaline solution of the alkaline leaching in the step (1) comprises a sodium hydroxide solution and/or a potassium hydroxide solution.
Preferably, the concentration of the alkali solution is 0.05 to 1mol/L, and may be, for example, 0.05mol/L, 0.16mol/L, 0.27mol/L, 0.37mol/L, 0.48mol/L, 0.58mol/L, 0.69mol/L, 0.79mol/L, 0.9mol/L, or 1mol/L, etc., but is not limited to the values recited, and other values not recited in this range are also applicable.
Preferably, drying is included between the alkaline leaching and the ball milling treatment in step (1).
Preferably, the drying temperature is 80 to 120 ℃, for example, 80 ℃, 85 ℃, 89 ℃, 94 ℃, 98 ℃, 103 ℃, 107 ℃, 112 ℃, 116 ℃ or 120 ℃, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the drying time is 2 to 5 hours, for example, 2 hours, 2.4 hours, 2.7 hours, 3 hours, 3.4 hours, 3.7 hours, 4 hours, 4.4 hours, 4.7 hours, or 5 hours, etc., but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the ball milling treatment is followed by sieving.
Preferably, the particle size of the particulate material is controlled by sieving to 15 μm or less, for example, 15 μm, 14 μm, 13 μm, 12 μm, 11 μm, 10 μm, 8 μm or 7 μm, but is not limited to the values listed, and other values not listed in this range are also applicable.
Preferably, the organic solvent soaking in step (1) is performed under ultrasonic conditions.
Preferably, the organic solvent for soaking in the organic solvent comprises any one of acetone, N-methyl pyrrolidone or dimethylformamide or a combination of at least two of them, wherein typical but non-limiting combinations are a combination of acetone and N-methyl pyrrolidone, a combination of dimethylformamide and N-methyl pyrrolidone, and a combination of acetone and dimethylformamide.
Preferably, the organic solvent is soaked for 1 to 4 hours, for example, 1 hour, 1.4 hours, 1.7 hours, 2 hours, 2.4 hours, 2.7 hours, 3 hours, 3.4 hours, 3.7 hours or 4 hours, etc., but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the temperature of the calcination in the step (1) is 200 to 400 ℃, and may be, for example, 200 ℃, 223 ℃, 245 ℃, 267 ℃, 289 ℃, 312 ℃, 334 ℃, 356 ℃, 378 ℃ or 400 ℃, but not limited to the values listed, and other values not listed in the range are also applicable.
Preferably, the baking time is 2 to 5 hours, for example, 2 hours, 2.4 hours, 2.7 hours, 3 hours, 3.4 hours, 3.7 hours, 4 hours, 4.4 hours, 4.7 hours, or 5 hours, etc., but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the concentration of the oxalic acid solution in the step (2) is 0.1 to 0.3mol/L, for example, 0.1mol/L, 0.13mol/L, 0.15mol/L, 0.17mol/L, 0.19mol/L, 0.22mol/L, 0.24mol/L, 0.26mol/L, 0.28mol/L or 0.3mol/L, etc., but not limited to the values listed, and other values not listed in the range are also applicable.
The concentration of the oxalic acid solution is further preferably in the range, so that the recovery rate and the purity of the iron are improved.
Preferably, the temperature of the acid leaching is 60 to 80 ℃, for example, 60 ℃, 63 ℃, 65 ℃, 67 ℃, 69 ℃, 72 ℃, 74 ℃, 76 ℃, 78 ℃ or 80 ℃, but not limited to the recited values, and other values not recited in the range are also applicable.
In the present invention, it is further preferable to set the temperature for acid leaching within the above range, and the leaching rate can be further improved.
Preferably, the acid leaching time is 60-120 min, such as 60min, 67min, 74min, 80min, 87min, 94min, 100min, 107min, 114min or 120min, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the solid-to-liquid ratio of the acid leaching is 10 to 100g/L, for example, 10g/L, 20g/L, 30g/L, 40g/L, 50g/L, 60g/L, 70g/L, 80g/L, 90g/L or 100g/L, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the sodium carbonate is added in the step (3) according to a molar ratio of the sodium carbonate to the lithium ions in the leachate of 1: 2-1.5: 2, which may be 1:2, 1.1:2, 1.2:2, 1.3:2, 1.4:2 or 1.5:2, for example.
Preferably, the temperature of the mixing in step (3) is 80 to 95 ℃, for example, 80 ℃, 82 ℃, 84 ℃, 85 ℃, 86 ℃, 87 ℃, 88 ℃, 90 ℃, 92 ℃ or 95 ℃, but not limited to the values listed, and other values not listed in the range are also applicable.
Preferably, the molar ratio of the lithium carbonate, the iron oxalate dihydrate precipitate and the phosphorus source in step (4) is (0.98-1.02): (0.98-1.02), and may be, for example, 0.98:0.98:1, 0.99:0.98:1, 1.00:0.98:1, 1.01:0.98:1, 1.02:0.98:1, 0.98:0.99:1, 0.98:1.00:1, 0.98:1.01:1, 0.99:1.02:1, 0.98:1.00:1.00, 0.98:1.00:0.99, 0.98:1.00:1.01 or 0.98:1.00:0.02, and the like, but is not limited to the same values as those stated above.
Preferably, the source of phosphorus comprises ammonium dihydrogen phosphate.
Preferably, the calcination in step (4) comprises three stages of calcination, namely a first calcination, a second calcination and a third calcination.
Preferably, the temperature of the first calcination is 280 to 320 ℃, for example, 280 ℃, 285 ℃, 289 ℃, 294 ℃, 298 ℃, 303 ℃, 307 ℃, 312 ℃, 316 ℃ or 320 ℃, etc., but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the time of the first calcination is 1.5 to 3 hours, for example, 1.5 hours, 1.7 hours, 1.9 hours, 2 hours, 2.2 hours, 2.4 hours, 2.5 hours, 2.7 hours, 2.9 hours, or 3 hours, etc., but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the first calcination is performed under vacuum conditions.
Preferably, the temperature of the second calcination is 420 to 480 ℃, for example, 420 ℃, 427 ℃, 434 ℃, 440 ℃, 447 ℃, 454 ℃, 460 ℃, 467 ℃, 474 ℃, or 480 ℃, etc., but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the time of the second calcination is 2 to 4 hours, for example, 2 hours, 2.3 hours, 2.5 hours, 2.7 hours, 2.9 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, or 4 hours, etc., but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the second calcination is carried out in a protective atmosphere.
Preferably, the temperature of the third calcination is 600 to 800 ℃, for example, 600 ℃, 620 ℃, 640 ℃, 660 ℃, 680 ℃, 710 ℃, 730 ℃, 750 ℃, 770 ℃ or 800 ℃ and the like, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the time of the third calcination is 12 to 36 hours, for example, 12 hours, 15 hours, 18 hours, 20 hours, 23 hours, 26 hours, 28 hours, 31 hours, 34 hours or 36 hours, etc., but is not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the third calcination is carried out in a protective atmosphere.
Preferably, the protective atmosphere in the second calcination and the third calcination is a nitrogen atmosphere.
The solid-liquid separation in the above process is not particularly limited in the present invention, and any device and method for solid-liquid separation known to those skilled in the art can be used, and may be adjusted according to the actual process, such as filtration, centrifugation, or sedimentation, or may be a combination of different methods.
The drying in the above process is not limited in any way, and any device and method for drying known to those skilled in the art can be used, and can be adjusted according to the actual process, such as air drying, vacuum drying, oven drying or freeze drying, or a combination of different methods.
The screening in the above process is not limited in any way, and any device and method for screening known to those skilled in the art can be used, and can be adjusted according to the actual process, for example, it can be a vibrating screening.
As a preferable technical scheme of the invention, the method comprises the following steps:
(1) sequentially carrying out alkaline leaching separation on the lithium iron phosphate waste positive electrode material by using an alkaline solution with the concentration of 0.05-1 mol/L to obtain an aluminum foil, carrying out solid-liquid separation, drying at 80-120 ℃ for 2-5 h, carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; sequentially soaking the granular material in an organic solvent under an ultrasonic condition for 1-4 h to separate a binder, performing solid-liquid separation, and roasting at 200-400 ℃ for 2-5 h to separate carbon to obtain a mixed material containing phosphorus, iron and lithium;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution with the concentration of 0.1-0.3 mol/L at the temperature of 60-80 ℃ for 60-120 min, wherein the solid-liquid ratio of the acid leaching is 10-100 g/L, and carrying out solid-liquid separation to obtain a leaching solution and ferric oxalate dihydrate precipitate;
(3) mixing sodium carbonate and the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1: 2-1.5: 2, precipitating lithium and carrying out solid-liquid separation to obtain lithium carbonate;
(4) mixing the lithium carbonate in the step (3), the ferric oxalate dihydrate precipitate in the step (2) and a phosphorus source according to a molar ratio of (0.98-1.02) to (0.98-1.02), and sequentially performing first calcination at 280-320 ℃ for 1.5-3 h under a vacuum condition, second calcination at 420-480 ℃ for 2-4 h under a nitrogen atmosphere and second calcination at 600-800 ℃ for 12-36 h under a nitrogen atmosphere to obtain the lithium iron phosphate.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the method for preparing the lithium iron phosphate from the waste lithium iron phosphate anode material provided by the invention prepares the high-purity lithium iron phosphate through simple and easily-industrialized steps, the purity of the high-purity lithium iron phosphate is up to more than 99.92 wt% under the optimal condition, the recovery rate of iron can reach 98 wt%, the recovery rate of general iron is more than 85%, the recovery rate of lithium can reach more than 99 wt%, and the recovery rate of general lithium is more than 90%;
(2) the lithium iron phosphate prepared by the method for preparing lithium iron phosphate from the waste lithium iron phosphate anode material provided by the invention has excellent performance, can be matched with the electrochemical performance of the original lithium iron phosphate material, and has the specific discharge capacity of 0.5C after being prepared into a lithium battery of more than 140mAh/g, preferably more than 160mAh/g, high cycle stability, and the specific discharge capacity of 300 times of cycle is still more than 135mAh/g, preferably more than 150 mAh/g;
(3) according to the method for preparing lithium iron phosphate from the waste lithium iron phosphate anode material, provided by the invention, iron precipitation is realized in an oxalic acid leaching manner, so that the lithium iron phosphate material can be repeatedly prepared, and compared with the existing method for recovering lithium iron phosphate, the electrochemical performance of the lithium iron phosphate is higher; compared with the existing process of only recovering lithium carbonate, the method provided by the invention can recover various elements in the waste lithium iron phosphate positive material, wherein the purity of the recovered ferric oxalate dihydrate is above 99%, the purity of lithium carbonate is above 99.91%, and the resource utilization effect is better.
Drawings
Fig. 1 is a schematic flow chart of a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material provided in embodiment 1 of the present invention.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
Example 1
The embodiment provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, as shown in fig. 1, the method includes the following steps:
(1) sequentially carrying out alkaline leaching on the waste lithium iron phosphate positive electrode material by using a sodium hydroxide solution with the concentration of 1mol/L under the condition of stirring for 200r/min to separate an aluminum foil, filtering, washing the material after the aluminum foil is separated, drying at 120 ℃ for 5h, further carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; sequentially carrying out organic solvent soaking on the granular materials for 4 hours to separate the binder by stirring the granular materials with an N-methyl pyrrolidone solvent under the ultrasonic condition of 200r/min (power of 50W), then filtering and drying the binder, and roasting the obtained product at 300 ℃ for 5 hours to separate carbon to obtain a mixed material containing phosphorus, iron and lithium;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution with the concentration of 0.3mol/L at the temperature of 80 ℃ for 120min, wherein the solid-liquid ratio of the acid leaching is 100g/L, and then filtering, carrying out solid-liquid separation and washing to obtain a leaching solution and ferric oxalate dihydrate precipitates;
(3) mixing sodium carbonate with the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1.5:2, precipitating lithium, filtering and washing to obtain lithium carbonate;
(4) and (3) mixing the lithium carbonate in the step (3), the ferric oxalate dihydrate precipitate in the step (2) and ammonium dihydrogen phosphate according to a molar ratio of 1.02:1:1 at 80 ℃, and sequentially performing first calcination at 300 ℃ for 2h under a vacuum condition, second calcination at 450 ℃ for 4h in a nitrogen atmosphere and second calcination at 800 ℃ for 36h in the nitrogen atmosphere to obtain the lithium iron phosphate.
Example 2
The embodiment provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, which comprises the following steps:
(1) sequentially carrying out alkaline leaching on the waste lithium iron phosphate positive electrode material by using a potassium hydroxide solution with the concentration of 0.1mol/L under the condition of stirring for 300r/min to separate an aluminum foil, filtering, washing the material after the aluminum foil is separated, drying at 90 ℃ for 4h, further carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; the granular materials are sequentially soaked in an N-methyl pyrrolidone solvent for 2 hours under the ultrasonic condition of stirring at 300r/min (power of 150W) to separate the binder, then filtered, dried and roasted at 200 ℃ for 3 hours to separate carbon, so that a mixed material containing phosphorus, iron and lithium is obtained;
(2) the mixed material is subjected to acid leaching at 70 ℃ for 90min in an oxalic acid solution with the concentration of 0.2mol/L, the solid-to-liquid ratio of the acid leaching is 50g/L, and then the mixed material is filtered and washed to obtain a leaching solution and ferric oxalate dihydrate precipitate;
(3) mixing sodium carbonate with the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1.2:2, precipitating lithium, filtering and washing to obtain lithium carbonate;
(4) and (3) mixing the lithium carbonate obtained in the step (3), the ferric oxalate dihydrate precipitate obtained in the step (2) and ammonium dihydrogen phosphate according to a molar ratio of 0.98:1.02:1 at 95 ℃, and sequentially performing first calcination at 300 ℃ for 2h under a vacuum condition, second calcination at 450 ℃ in a nitrogen atmosphere for 2h and second calcination at 700 ℃ in a nitrogen atmosphere for 24h to obtain the lithium iron phosphate.
Example 3
The embodiment provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, which comprises the following steps:
(1) sequentially carrying out alkaline leaching on the waste lithium iron phosphate positive electrode material by using a sodium hydroxide solution with the concentration of 0.2mol/L under the condition of stirring for 400r/min to separate an aluminum foil, filtering, washing the material after the aluminum foil is separated, drying the material at 100 ℃ for 4h, and then further carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; the granular materials are sequentially soaked in a dimethylformamide solvent for 3 hours under the ultrasonic condition of stirring at 400r/min (power of 90W) to separate a binder, then filtered, dried and roasted at 220 ℃ for 3.5 hours to separate carbon, so that a mixed material containing phosphorus, iron and lithium is obtained;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution with the concentration of 0.15mol/L at 65 ℃ for 100min, wherein the solid-to-liquid ratio of the acid leaching is 55g/L, and then filtering and washing to obtain a leaching solution and ferric oxalate dihydrate precipitates;
(3) mixing sodium carbonate with the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1.3:2, precipitating lithium, filtering and washing to obtain lithium carbonate;
(4) and (3) mixing the lithium carbonate in the step (3), the ferric oxalate dihydrate precipitate in the step (2) and ammonium dihydrogen phosphate according to a molar ratio of 1.02:0.98:1 at 90 ℃, and sequentially performing first calcination at 300 ℃ for 2h under a vacuum condition, second calcination at 480 ℃ in a nitrogen atmosphere for 2h and second calcination at 650 ℃ in the nitrogen atmosphere for 20h to obtain the lithium iron phosphate.
Example 4
The embodiment provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, which comprises the following steps:
(1) sequentially carrying out alkaline leaching on the waste lithium iron phosphate positive electrode material by using a sodium hydroxide solution with the concentration of 0.8mol/L under the condition of stirring for 350r/min to separate an aluminum foil, filtering, washing the material after the aluminum foil is separated, drying at 110 ℃ for 3.5h, further carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; the granular materials are sequentially soaked in an acetone solvent under the ultrasonic condition of stirring at 350r/min (power of 100W) for 5 hours to separate the binder, then filtered, dried and roasted at 320 ℃ for 3 hours to separate carbon, so as to obtain a mixed material containing phosphorus, iron and lithium;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution with the concentration of 0.22mol/L at 75 ℃ for 110min, wherein the solid-to-liquid ratio of the acid leaching is 89g/L, and then filtering and washing to obtain a leaching solution and ferric oxalate dihydrate precipitates;
(3) mixing sodium carbonate with the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1.4:2, precipitating lithium, filtering and washing to obtain lithium carbonate;
(4) and (3) mixing the lithium carbonate in the step (3), the ferric oxalate dihydrate precipitate in the step (2) and ammonium dihydrogen phosphate according to a molar ratio of 1:1:0.98 at 88 ℃, and sequentially performing first calcination at 300 ℃ for 2h under a vacuum condition, second calcination at 420 ℃ for 4h in a nitrogen atmosphere and second calcination at 750 ℃ for 30h in the nitrogen atmosphere to obtain the lithium iron phosphate.
Example 5
The embodiment provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, which comprises the following steps:
(1) sequentially carrying out alkaline leaching on the waste lithium iron phosphate positive electrode material by using a potassium hydroxide solution with the concentration of 0.9mol/L under the condition of stirring 280r/min to separate an aluminum foil, filtering, washing the material after the aluminum foil is separated, drying at 95 ℃ for 5 hours, further carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; the granular materials are sequentially soaked in a dimethylformamide solvent for 2 hours under the ultrasonic condition of stirring at 280r/min (power of 90W) to separate a binder, then filtered, dried and roasted at 250 ℃ for 4 hours to separate carbon, so that a mixed material containing phosphorus, iron and lithium is obtained;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution with the concentration of 0.28mol/L at 75 ℃ for 110min, wherein the solid-to-liquid ratio of the acid leaching is 20g/L, and then filtering and washing to obtain a leaching solution and ferric oxalate dihydrate precipitates;
(3) mixing sodium carbonate with the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1.1:2, precipitating lithium, filtering and washing to obtain lithium carbonate;
(4) and (3) mixing the lithium carbonate in the step (3), the ferric oxalate dihydrate precipitate in the step (2) and ammonium dihydrogen phosphate according to a molar ratio of 1.02:1:1.02 at the temperature of 80 ℃, and sequentially performing first calcination at 300 ℃ for 2h under a vacuum condition, second calcination at 430 ℃ in a nitrogen atmosphere for 2.5h and second calcination at 780 ℃ in the nitrogen atmosphere for 35h to obtain the lithium iron phosphate.
Example 6
The embodiment provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, which comprises the following steps:
(1) sequentially carrying out alkaline leaching on the waste lithium iron phosphate positive electrode material by using a sodium hydroxide solution with the concentration of 0.1mol/L under the condition of stirring 320r/min to separate an aluminum foil, filtering, washing the material after the aluminum foil is separated, drying at 80 ℃ for 5h, further carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; the granular materials are sequentially soaked in a dimethylformamide solvent for 1.5h under the ultrasonic condition of stirring 320r/min (power of 70W) to separate a binder, then filtered, dried and roasted at 400 ℃ for 5h to separate carbon, so that a mixed material containing phosphorus, iron and lithium is obtained;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution with the concentration of 0.1mol/L for 60min at the temperature of 60 ℃, wherein the solid-to-liquid ratio of the acid leaching is 30g/L, and then filtering and washing to obtain a leaching solution and ferric oxalate dihydrate precipitates;
(3) mixing sodium carbonate with the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1.4:2, precipitating lithium, filtering and washing to obtain lithium carbonate;
(4) and (3) mixing the lithium carbonate in the step (3), the ferric oxalate dihydrate precipitate in the step (2) and ammonium dihydrogen phosphate according to a molar ratio of 0.98:1:1.02 at 85 ℃, and sequentially performing first calcination at 300 ℃ for 2h under a vacuum condition, second calcination at 470 ℃ in a nitrogen atmosphere for 3.8h and second calcination at 700 ℃ in the nitrogen atmosphere for 33h to obtain the lithium iron phosphate.
Example 7
The embodiment provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, which comprises the following steps:
(1) sequentially carrying out alkaline leaching on the waste lithium iron phosphate positive electrode material by using a potassium hydroxide solution with the concentration of 0.7mol/L under the condition of stirring for 400r/min to separate an aluminum foil, filtering, washing the material after the aluminum foil is separated, drying the material at 100 ℃ for 4h, and then further carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; the granular materials are sequentially soaked in a dimethylformamide solvent for 1h under the ultrasonic condition of stirring at 400r/min (power of 60W) to separate a binder, then filtered, dried and roasted at 250 ℃ for 3h to separate carbon, so that a mixed material containing phosphorus, iron and lithium is obtained;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution with the concentration of 0.1mol/L at 70 ℃ for 100min, wherein the solid-to-liquid ratio of the acid leaching is 90g/L, and then filtering and washing to obtain a leaching solution and ferric oxalate dihydrate precipitates;
(3) mixing sodium carbonate with the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1:2, precipitating lithium, filtering and washing to obtain lithium carbonate;
(4) and (3) mixing the lithium carbonate in the step (3), the ferric oxalate dihydrate precipitate in the step (2) and ammonium dihydrogen phosphate according to a molar ratio of 1.02:1:1 at 90 ℃, and sequentially performing first calcination at 300 ℃ for 2h under a vacuum condition, second calcination at 450 ℃ for 4h in a nitrogen atmosphere and second calcination at 750 ℃ for 38h in the nitrogen atmosphere to obtain the lithium iron phosphate.
Example 8
The embodiment provides a method for preparing lithium iron phosphate from waste lithium iron phosphate cathode materials, which is the same as the embodiment 1 except that the concentration of oxalic acid in the step (2) is 0.05 mol/L.
Example 9
The embodiment provides a method for preparing lithium iron phosphate from waste lithium iron phosphate cathode materials, which is the same as the embodiment 1 except that the concentration of oxalic acid in the step (2) is 0.5 mol/L.
Example 10
The embodiment provides a method for preparing lithium iron phosphate from waste lithium iron phosphate cathode materials, which is the same as that in embodiment 1 except that the acid leaching temperature in step (2) is 50 ℃.
Example 11
The embodiment provides a method for preparing lithium iron phosphate from waste lithium iron phosphate cathode materials, which is the same as that in embodiment 1 except that the acid leaching temperature in step (2) is 90 ℃.
Example 12
The embodiment provides a method for preparing lithium iron phosphate from waste lithium iron phosphate cathode materials, which is the same as the embodiment 1 except that the step (4) is not subjected to primary calcination.
Example 13
The embodiment provides a method for preparing lithium iron phosphate from waste lithium iron phosphate cathode materials, which is the same as the embodiment 1 except that the third calcination is not performed in the step (4).
Comparative example 1
The comparative example provides a method for preparing lithium iron phosphate from waste lithium iron phosphate cathode materials, and the method is the same as the method in the example 1 except that roasting is not performed to separate carbon in the step (1).
Comparative example 2
The comparative example provides a method for preparing lithium iron phosphate from a waste lithium iron phosphate positive electrode material, and the method is the same as the method in the example 1 except that the step (1) is not soaked in an organic solvent.
Comparative example 3
The comparative example provides a method for preparing lithium iron phosphate from waste lithium iron phosphate cathode materials, and the method is the same as the method in the embodiment 1 except that a sulfuric acid solution is adopted in the step (2).
The test method comprises the following steps: testing the purity of lithium carbonate and ferric oxalate dihydrate by adopting an ICP (inductively coupled plasma) method, and calculating the recovery rate of lithium and iron by adopting a ratio method of the content of Li and Fe in the lithium carbonate and the ferric oxalate dihydrate to the content of Li and Fe in the waste cathode material; testing the purity of the lithium iron phosphate by adopting an ICP (inductively coupled plasma) method; testing the granularity of the lithium iron phosphate by adopting a laser granularity distribution instrument method; and testing the electrochemical performance of the lithium iron phosphate by adopting an electrochemical workstation method.
The test results of the above examples and comparative examples are shown in table 1.
TABLE 1
From table 1, the following points can be seen:
(1) it can be seen from the comprehensive embodiments 1 to 7 that the method for preparing lithium iron phosphate from the waste lithium iron phosphate positive electrode material provided by the invention can obtain a lithium iron phosphate product with high purity and high recovery rate, wherein the purity of lithium carbonate is more than 99.91%, the purity of iron oxalate dihydrate precipitate is more than 99%, the purity of lithium iron phosphate is more than 99.92%, the recovery rate of lithium is more than 90%, the recovery rate of iron is more than 85%, and the obtained lithium iron phosphate has excellent electrochemical performance, and after the lithium iron phosphate is prepared into a lithium battery, the 0.5C specific discharge capacity is more than 140mAh/g, preferably more than 160mAh/g, and the cycle stability is high, and the 300-cycle specific discharge capacity is still more than 135 mAh/g;
(2) it can be seen from the combination of the embodiment 1 and the embodiments 8 to 9 that the concentration of oxalic acid in the embodiment 8 is only 0.05mol/L, while the concentration of oxalic acid in the embodiment 9 is as high as 0.5mol/L, wherein the recovery rates of lithium and iron in the embodiment 8 are significantly reduced, while the recovery rate of iron is improved in the embodiment 9 by further improving the concentration of oxalic acid, but the cycle performance of lithium iron phosphate in the battery is reduced, and the recovery rate and the cycle stability are high in the embodiment 1, thereby showing that the invention can simultaneously guarantee the recovery rate, the purity and the final electrochemical performance of lithium iron phosphate by optimizing the specific concentration of oxalic acid;
(3) it can be seen from the comprehensive examples 1 and 10 to 11 that the recovery rates of lithium and iron and the cycling stability of the product can be ensured simultaneously by controlling the acid leaching temperature within a specific range;
(4) it can be seen from the comprehensive results of examples 1 and 12 to 13 that, in example 1, three-step calcination is strictly performed, and compared with the case where the first calcination is not performed in example 12 and the third calcination is not performed in example 13, the average particle sizes of lithium iron phosphate in examples 12 and 13 are large and respectively reach 14.6 μm and 24.5 μm, and the charge-discharge performance and the cycle stability of the lithium iron phosphate are far lower than those of example 1, thereby indicating that the calcination process of the lithium iron phosphate is strictly controlled, and the performance of the lithium iron phosphate product is remarkably improved;
(5) it can be seen from the comprehensive example 1 and the comparative examples 1-2 that in the comparative example 1, the roasting separation of carbon is not performed, the lithium carbonate, the ferric oxalate and the lithium iron phosphate have low purity, and the product performance is poor; in comparative example 2, no organic solvent was used for soaking, the lithium carbonate, iron oxalate and lithium iron phosphate had low purity, and both the charge and discharge performance and the cycle stability of lithium iron phosphate were poor.
The present invention is described in detail with reference to the above embodiments, but the present invention is not limited to the above detailed structural features, that is, the present invention is not meant to be implemented only by relying on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A method for preparing lithium iron phosphate from waste lithium iron phosphate anode materials is characterized by comprising the following steps:
(1) sequentially carrying out alkaline leaching separation on the lithium iron phosphate waste positive electrode material by using an aluminum foil and ball milling to obtain a granular material; sequentially soaking and separating the binder and roasting and separating carbon in the granular material by using an organic solvent to obtain a mixed material containing phosphorus, iron and lithium;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution, and carrying out solid-liquid separation to obtain a leaching solution and a dihydrate ferric oxalate precipitate;
(3) mixing sodium carbonate with the leaching solution, precipitating lithium and carrying out solid-liquid separation to obtain lithium carbonate;
(4) and (3) mixing the ferric oxalate dihydrate precipitate in the step (2) and the lithium carbonate and the phosphorus source in the step (3), and calcining to obtain the lithium iron phosphate.
2. The method according to claim 1, wherein the alkaline solution of the alkaline leaching in step (1) comprises a sodium hydroxide solution and/or a potassium hydroxide solution;
preferably, the concentration of the alkali solution is 0.05-1 mol/L.
3. The method according to claim 1 or 2, wherein the alkaline leaching and ball milling treatment in step (1) includes drying;
preferably, the drying temperature is 80-120 ℃;
preferably, the drying time is 2-5 h;
preferably, the ball milling treatment is followed by sieving;
preferably, the sieving controls the particle size of the particulate material to be below 15 μm.
4. The method according to any one of claims 1 to 3, wherein the organic solvent soaking in the step (1) is performed under ultrasonic conditions;
preferably, the organic solvent for soaking the organic solvent comprises any one of acetone, N-methyl pyrrolidone or dimethylformamide or a combination of at least two of the acetone, the N-methyl pyrrolidone or the dimethylformamide;
preferably, the soaking time of the organic solvent is 1-4 h.
5. The method according to any one of claims 1 to 4, wherein the temperature of the roasting in the step (1) is 200 to 400 ℃;
preferably, the roasting time is 2-5 h.
6. The method according to any one of claims 1 to 5, wherein the concentration of the oxalic acid solution in the step (2) is 0.1 to 0.3 mol/L;
preferably, the temperature of acid leaching is 60-80 ℃;
preferably, the acid leaching time is 60-120 min;
preferably, the solid-to-liquid ratio of the acid leaching is 10-100 g/L.
7. The method according to any one of claims 1 to 6, wherein the sodium carbonate is added in the step (3) in a molar ratio of 1:2 to 1.5:2 of the sodium carbonate to the lithium ions in the leachate;
preferably, the mixing temperature in the step (3) is 80-95 ℃.
8. The method according to any one of claims 1 to 7, wherein the molar ratio of the lithium carbonate, the iron oxalate dihydrate precipitate and the phosphorus source in step (4) is (0.98-1.02): (0.98-1.02);
preferably, the source of phosphorus comprises ammonium dihydrogen phosphate.
9. The method according to any one of claims 1 to 8, wherein the calcination in step (4) comprises three stages of calcination, namely a first calcination, a second calcination and a third calcination;
preferably, the temperature of the first calcination is 280-320 ℃;
preferably, the time of the first calcination is 1.5-3 h;
preferably, the first calcination is carried out under vacuum conditions;
preferably, the temperature of the second calcination is 420-480 ℃;
preferably, the time of the second calcination is 2-4 h;
preferably, the second calcination is carried out in a protective atmosphere;
preferably, the temperature of the third calcination is 600-800 ℃;
preferably, the time of the third calcination is 12-36 h;
preferably, the third calcination is carried out in a protective atmosphere;
preferably, the protective atmosphere in the second calcination and the third calcination is a nitrogen atmosphere.
10. A method according to any one of claims 1 to 9, characterized in that the method comprises the steps of:
(1) sequentially carrying out alkaline leaching separation on the lithium iron phosphate waste positive electrode material by using an alkaline solution with the concentration of 0.05-1 mol/L to obtain an aluminum foil, carrying out solid-liquid separation, drying at 80-120 ℃ for 2-5 h, carrying out ball milling treatment and vibrating screening to obtain a granular material with the particle size of below 15 mu m; sequentially soaking the granular material in an organic solvent under an ultrasonic condition for 1-4 h to separate a binder, performing solid-liquid separation, and roasting at 200-400 ℃ for 2-5 h to separate carbon to obtain a mixed material containing phosphorus, iron and lithium;
(2) carrying out acid leaching on the mixed material in an oxalic acid solution with the concentration of 0.1-0.3 mol/L at the temperature of 60-80 ℃ for 60-120 min, wherein the solid-liquid ratio of acid leaching is 10-100 g/L, and carrying out solid-liquid separation to obtain a leaching solution and ferric oxalate dihydrate precipitate;
(3) mixing sodium carbonate and the leachate according to the molar ratio of the sodium carbonate to the lithium ions in the leachate of 1: 2-1.5: 2, precipitating lithium and carrying out solid-liquid separation to obtain lithium carbonate;
(4) mixing the lithium carbonate in the step (3), the ferric oxalate dihydrate precipitate in the step (2) and a phosphorus source according to a molar ratio of (0.98-1.02) to (0.98-1.02), and sequentially performing first calcination at 280-320 ℃ for 1.5-3 h under a vacuum condition, second calcination at 420-480 ℃ for 2-4 h under a nitrogen atmosphere and second calcination at 600-800 ℃ for 12-36 h under a nitrogen atmosphere to obtain the lithium iron phosphate.
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