A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from ternary lithium battery cathode materials

Abstract

The present application belongs to the technical field of battery material recycling, and particularly relates to a method for preparing battery-grade lithium phosphate from lithium phosphate recovered from a positive electrode material of a ternary lithium battery. The present application uses calcium carbonate as a conversion agent, which can not only remove organic matter remaining in the lithium phosphate raw material at high temperature, but also release a large amount of carbon dioxide gas, so that the material is fluffy and porous, facilitating subsequent reactions; becomes calcium oxide during calcination, and directly reacts into calcium phosphate which is difficult to dissolve in water and lithium hydroxide which is easy to dissolve in water after steam is passed, and in this process, a small amount of nickel, cobalt, manganese, iron, copper, magnesium and other metals in the raw material can be converted into corresponding hydroxides which are insoluble in water, integrating the conversion and impurity removal processes; after water immersion and impurity removal, lithium hydroxide aqueous solution is obtained by filtration, phosphorus is precipitated by adding phosphoric acid, no new impurities are introduced, the mother liquor can be recycled and used, and the economic and environmental performance is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery material recycling, and in particular relates to a method for preparing battery-grade lithium phosphate from lithium phosphate recovered from anode materials of ternary lithium batteries. Background Art

[0002] In recent years, with the development of new energy vehicles and technological iterations, a large amount of scrapped ternary lithium battery materials has been generated. After being discharged and disassembled, the scrapped ternary materials are dissolved in sulfuric acid, and then precious metals such as nickel, cobalt, and manganese are recovered through an extraction process. Considering production costs and economic benefits, the residual extract is added with sodium phosphate to precipitate the lithium in the form of crude lithium phosphate to achieve the purpose of lithium recovery. However, the crude lithium phosphate obtained in this way cannot be directly used due to its high impurity content and large amount of organic matter attached to it. It needs to be purified or converted before it can be used in the production of lithium battery materials.

[0003] At present, there have been many reports on the research of lithium phosphate, which are mainly divided into two directions. One is to acid-decompose crude lithium phosphate and then remove impurities and phosphorus, and then convert it into lithium hydroxide, lithium carbonate, and lithium phosphate; the other is to purify the crude lithium phosphate into battery-grade lithium phosphate through certain technical means, such as the method used in the Chinese invention patent application: Method for preparing battery-grade lithium phosphate using crude lithium phosphate and crude phosphoric acid (Publication No.: CN115557479A) is to add water to the crude lithium phosphate to make a slurry, then acidify and dissolve it with phosphoric acid and remove impurities, and then adjust the pH with lithium carbonate or lithium hydroxide to regenerate lithium phosphate to prepare battery-grade lithium phosphate. This patent application adopts the method of acidifying and removing impurities and then converting it into battery-grade lithium phosphate. The process of purifying the lithium phosphate requires the consumption of a large amount of phosphoric acid and more expensive lithium carbonate or lithium hydroxide, and is therefore less economical. A Chinese invention patent application, "A method for preparing battery-grade lithium phosphate" (publication number: CN11153310A), uses crude lithium phosphate recovered from ternary materials or salt lake lithium phosphate as raw material. The raw material is first matured and crushed, then acid-lyzed and adjusted to a pH of 4-7 before filtering and removing impurities. The resulting lithium-containing filtrate is subjected to a secondary impurity removal with a resin, and then phosphoric acid is used to adjust the lithium:phosphorus molar ratio in the secondary filtrate to 2.95-3.05:1. Strong alkali is then used to adjust the pH and precipitate the lithium phosphate. The process of this patent application is long, requires the consumption of a large amount of acid and alkali, and is less environmentally friendly and economical. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the object of the present invention is to provide a method for preparing battery-grade lithium phosphate using lithium phosphate recovered from ternary materials.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from a ternary lithium battery cathode material, comprising the following steps:

[0007] (1) Calcium carbonate and crude lithium phosphate recovered from the positive electrode material of a ternary lithium battery are mixed in a mass ratio of (1-5):1, and ground for later use (the grinding is preferably performed by dry grinding until it passes through a 200-mesh sieve);

[0008] (2) calcining the ground mixture at 700-900°C for 2-5h (preferably calcining at 800-900°C for 2-3h), then cooling to 200-300°C and keeping warm for 1-3h; introducing steam into the mixture during the keeping warm process to promote the reaction (preferably introducing steam into the mixture at 300°C for 2-3h), removing the mixture and cooling it to room temperature; adding deionized water to the cooled mixture at a liquid-to-solid ratio of (10-15) mL / g and wet grinding the mixture, filtering the obtained slurry to obtain primary filtrate A;

[0009] (3) Add oxalic acid equivalent to 2-3 times the amount of calcium element substance to the primary filtrate A according to the calcium content in the primary filtrate A, raise the temperature to 80-95°C, and stir the reaction at 80-95°C for 0.5-2 hours to remove calcium (preferably, stir the reaction at 95°C for 1 hour). After the reaction is completed, filter while hot to obtain the secondary filtrate B;

[0010] (4) Phosphoric acid is added to the secondary filtrate B until the pH of the system is 6.0-6.5, and then sodium phosphate is added to adjust the pH of the system to 9.0-10.0, and the wet lithium phosphate is obtained by filtration; the wet lithium phosphate obtained is placed in a vacuum oven and dried to obtain battery-grade lithium phosphate.

[0011] Furthermore, in step (2), when introducing water vapor, according to the reaction materials, ensure that the water vapor is in full contact with the materials to promote the reaction.

[0012] Furthermore, in step (4), the drying is: baking at 105° C. for 4 hours.

[0013] Furthermore, in step (2), the mass ratio of the calcium carbonate to the crude lithium phosphate recovered from the ternary material is 1.3:1.

[0014] Furthermore, the lithium phosphate recovered in the ternary material is a crude lithium phosphate product obtained by adding sodium phosphate to the ternary lithium battery positive electrode material purchased from GEM Co., Ltd. after recovering precious metals. The mass percentage content of each element detected by ICP is as follows: lithium 17.2%, calcium 0.04%, magnesium 0.05%, nickel 0.87%, manganese 0.06%, and cobalt 0.12%.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0016] ① Compared with the acid leaching conversion technology, the present invention does not use a large amount of strong acid, and there is no acid water callback problem in the later stage, which is safer and more environmentally friendly;

[0017] ② The present invention adopts a calcium carbonate calcination process, which can not only remove residual organic matter in the lithium phosphate raw material at high temperature, but also release a large amount of carbon dioxide gas, making the material fluffy and porous, which is convenient for subsequent reactions; the lithium phosphate recovered from the positive electrode material of the ternary lithium battery contains a lot of organic matter, and contains metal impurities such as nickel, cobalt, manganese, calcium, and magnesium, making lithium extraction difficult. The present invention uses calcium carbonate as a conversion agent, which is converted into calcium oxide during the calcination process, and directly reacts after steam is passed to form calcium phosphate that is insoluble in water and lithium hydroxide that is easily soluble in water. In this process, a small amount of metals such as nickel, cobalt, manganese, iron, copper, and magnesium in the raw material can be converted into corresponding water-insoluble hydroxides, integrating the conversion and impurity removal processes; after water immersion and impurity removal, the lithium hydroxide aqueous solution is obtained by filtration, and the lithium phosphate is precipitated after adding phosphoric acid to adjust the pH. No new impurities are introduced, and the mother liquor can be recycled, which is highly economical and environmentally friendly. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described in detail below through specific embodiments.

[0019] In the following examples, electronic grade oxalic acid (H2C2O4·2H2O, purity 99.6%); industrial grade phosphoric acid (H3PO4, content 75%); the flow rate during the water vapor flow in the following examples is measured in terms of liquid water: 1 L / h. During the water vapor flow process, a stainless steel hose was connected to the muffle furnace, the other end of which was connected to a three-necked flask (1000 ml) filled with water via a rubber stopper. The three-necked flask was fixed in an electric heating mantle, and the temperature of the electric heating mantle was set at 150°C. The water vapor entered the muffle furnace through the hose and contacted the material. During the heating process, water was replenished regularly according to the change in the liquid level in the flask.

[0020] The raw material lithium phosphate used in the following examples and comparative examples is a crude lithium phosphate obtained by adding sodium phosphate to the nickel-cobalt-manganese ternary lithium battery positive electrode material purchased from GEM Co., Ltd. after recovering precious metals. The mass percentage content of each element is as follows after ICP detection: lithium 17.2%, calcium 0.04%, magnesium 0.05%, nickel 0.87%, manganese 0.06%, cobalt 0.12%, sodium 0.89%, sulfate 1.20%, iron 0.11%, and aluminum 0.02%.

[0021] The battery-grade lithium phosphate described in this application is lithium phosphate with a purity of ≥99%.

[0022] Example 1 A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from a ternary lithium battery cathode material, comprising the following steps:

[0023] (1) 100 g of lithium phosphate and 130 g of calcium carbonate were mixed and ground until they passed a 200-mesh sieve. The resulting mixture was placed in a muffle furnace and heated to 800° C. at 10° C. / min, and then calcined at 800° C. for 2 h. The muffle furnace was then cooled to 300° C. At 300° C., water vapor was introduced into the muffle furnace through an external interface for 2 h. The water vapor and heating device were then turned off, the material was taken out and cooled to room temperature (20-25° C., the same below), and 168.3 g was weighed.

[0024] (2) 168.3 g of the obtained material was placed in a ball mill, and 2000 mL of pure water was added and ball-milled for 1 hour. Then, calcium phosphate solid and 2000 mL of lithium hydroxide solution were filtered out. The lithium content in the lithium hydroxide solution was 7.52 g / L and the calcium content was 0.4835 g / L. The lithium leaching rate was calculated to be 87.4%. 6.1 g of electronic grade oxalic acid was added to the above 2000 mL of lithium hydroxide solution, and the temperature was raised to 95° C. and stirred for 1 hour. Then, the solution was filtered while hot and the filtrate was fixed to 2% by adding water. 000mL, the lithium content was detected to be 7.48g / L, and the calcium content was 0.0084g / L; then 95.8g of industrial-grade phosphoric acid was added thereto until the pH of the system was 6.5, and then 3.7g of sodium phosphate was added until the pH of the system was 9-10 (9.4 in this embodiment), and the wet lithium phosphate product was filtered. The wet lithium phosphate product was placed in a vacuum drying oven and heated to 105°C (vacuum degree -0.08MPa, the same below), and dried at 105°C for 4h to obtain 81.2g of battery-grade lithium phosphate.

[0025] XRD detection showed that the peak positions and relative intensities of the main peaks of the JADE pattern were basically consistent with those of the standard card of lithium phosphate, so the obtained product was determined to be lithium phosphate particles.

[0026] The content of each impurity component of the product was detected by ICP, and the water content was detected by coulometric method. The corresponding test results are shown in Table 1. The purity of lithium phosphate was then calculated by the difference method, that is, lithium phosphate purity = 100% - total impurity percentage - water percentage. The calculated purity of lithium phosphate in this embodiment is 99.4%. The calculation method of lithium phosphate purity in the following embodiments and comparative examples is the same as that in Example 1 and will not be repeated here. The contents of other undetected impurities (for example, potassium, chloride ions, zinc, and lead) are all within 1 ppm and can be ignored.

[0027] Example 2 A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from a ternary lithium battery cathode material, the specific steps being as follows:

[0028] (1) 100 g of lithium phosphate and 130 g of calcium carbonate were mixed and ground until they passed a 200-mesh sieve. The resulting mixture was placed in a muffle furnace and heated to 800° C., then calcined at 800° C. for 3 h. The muffle furnace was then cooled to 300° C. At 300° C., water vapor was introduced into the muffle furnace through an external interface for 3 h. The water vapor and heating device were then turned off, the material was taken out and cooled to room temperature, and 165.9 g was weighed.

[0029] (2) 165.9 g of the obtained material was placed in a ball mill, 2200 mL of pure water was added and the mixture was ball milled for 1 h, and calcium phosphate solid and 2200 mL of lithium hydroxide solution were filtered to obtain the lithium content of the lithium hydroxide solution, which was 7.18 g / L and the calcium content was 0.4105 g / L, and the lithium leaching rate was calculated to be 91.8%; 5.7 g of electronic grade oxalic acid was added to the above 2200 mL of lithium hydroxide solution, the temperature was raised to 95 ° C and the mixture was stirred for 1 h, then filtered while hot, and the filtrate was fixed to 2200 mL with water, and the lithium content was 7.15 g / L and the calcium content was 0.0049 g / L. g / L; then, 100.8 g of industrial-grade phosphoric acid was added thereto until the pH of the system reached 6.5, followed by the addition of 4.2 g of sodium phosphate to adjust the pH of the system to 9-10 (9.6 in the present embodiment), and the wet lithium phosphate product was filtered to obtain the wet lithium phosphate product. The wet lithium phosphate product was placed in a vacuum drying oven and heated to 105° C., and then dried at 105° C. for 4 h to obtain 86.1 g of battery-grade lithium phosphate. XRD analysis showed that the peak positions and relative intensities of the main peaks of the JADE pattern were substantially consistent with those of the standard lithium phosphate card. Therefore, the obtained product was determined to be lithium phosphate particles, and its purity was calculated to be 99.5%.

[0030] Example 3 A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from a ternary lithium battery cathode material, the specific steps being as follows:

[0031] (1) 100 g of lithium phosphate and 130 g of calcium carbonate were mixed and ground until they passed through a 200-mesh sieve. The resulting mixture was placed in a muffle furnace and heated to 900° C., then calcined at 900° C. for 3 h. The muffle furnace was then cooled to 300° C. At 300° C., water vapor was introduced into the muffle furnace through an external interface for 3 h. The water vapor and heating device were then turned off, the material was taken out and cooled to room temperature, and 165.1 g was weighed.

[0032] (2) 165.1 g of the obtained material was placed in a ball mill, and 2400 mL of pure water was added for ball milling for 1 h. The calcium phosphate solid and 2400 mL of lithium hydroxide solution were filtered to obtain the lithium content of the lithium hydroxide solution, which was 6.61 g / L and the calcium content was 0.3859 g / L. The lithium leaching rate was calculated to be 92.3%. 5.8 g of electronic grade oxalic acid was added to the above 2400 mL of lithium hydroxide solution, and the temperature was raised to 95 ° C. After stirring for 1 h, the solution was filtered while hot, and the filtrate was fixed to 2400 mL with water. The lithium content was 6.55 g / L and the calcium content was 0. .0037g / L; then, 101.5g of industrial-grade phosphoric acid was added to the filtrate until the pH of the system was 6.5, and then 5.6g of sodium phosphate was added to adjust the pH of the system to 9.2. The wet lithium phosphate product was filtered, and the wet lithium phosphate product was placed in a vacuum drying oven and heated to 105°C. It was dried at 105°C for 4h to obtain 85.4g of battery-grade lithium phosphate. XRD detection showed that its pattern on JADE was basically consistent with the peak positions and relative intensities of the main peaks of the standard card of lithium phosphate. Therefore, the obtained product was determined to be lithium phosphate particles, and its purity was calculated to be 99.5%.

[0033] Example 4 A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from a ternary lithium battery cathode material, comprising the following steps:

[0034] (1) 100 g of lithium phosphate and 130 g of calcium carbonate were mixed and ground until they passed a 200-mesh sieve. The resulting mixture was placed in a muffle furnace and heated to 700° C., then calcined at 700° C. for 2 h. The muffle furnace was then cooled to 200° C. At 300° C., water vapor was introduced into the muffle furnace through an external interface for 2 h. The water vapor and heating device were then turned off, the material was taken out and cooled to room temperature, and 168.9 g was weighed.

[0035] (2) 168.9 g of the obtained material was placed in a ball mill, and 2200 mL of pure water was added for ball milling for 1 h. The calcium phosphate solid and 2200 mL of lithium hydroxide solution were filtered to obtain the lithium content of 6.97 g / L and the calcium content of 0.4322 g / L in the lithium hydroxide solution. The lithium leaching rate was calculated to be 89.2%. 5.9 g of electronic grade oxalic acid was added to the above 2200 mL of lithium hydroxide solution, and the temperature was raised to 95 ° C. After stirring for 1 h, the solution was filtered while hot, and the filtrate was fixed to 2200 mL with water. The lithium content was 6.92 g / L and the calcium content was 0. .0059g / L; then, 98.3g of industrial-grade phosphoric acid was added to the filtrate until the pH of the system reached 6.5, and then 4.5g of sodium phosphate was added to adjust the pH of the system to 9.7. The wet lithium phosphate product was filtered, and the wet lithium phosphate product was placed in a vacuum drying oven and heated to 105°C. It was dried at 105°C for 4h to obtain 82.5g of battery-grade lithium phosphate. XRD detection showed that its pattern on JADE was basically consistent with the peak positions and relative intensities of the main peaks of the standard card of lithium phosphate. Therefore, the obtained product was determined to be lithium phosphate particles, and its purity was calculated to be 99.4%.

[0036] The composition analysis and calculated sample purity results of the products of Examples 1-4 obtained by ICP emission spectroscopy are shown in Table 1 below.

[0037] Table 1

[0038]

[0039] Note: The above contents are all in mass percentage.

[0040] Comparative Example 1 A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from a ternary lithium battery cathode material, the specific steps being as follows:

[0041] (1) 100 g of lithium phosphate and 144 g of calcium chloride were mixed and ground until they passed a 200-mesh sieve. The resulting mixture was placed in a muffle furnace and heated to 800° C., then calcined at 800° C. for 2 h. The muffle furnace was then cooled to 300° C. At 300° C., water vapor was introduced into the muffle furnace through an external interface for 2 h. The water vapor and heating device were then turned off, the material was taken out and cooled to room temperature, and 236.8 g was weighed.

[0042] (2) 236.8 g of the obtained material was placed in a ball mill, 2000 mL of pure water was added and the mixture was ball milled for 1 h, and calcium phosphate solid and 2000 mL of lithium chloride solution were filtered to obtain the lithium content of 6.95 g / L and the calcium content of 1.82 g / L in the lithium chloride solution. The lithium leaching rate was calculated to be 80.8%; 12.6 g of electronic grade oxalic acid was added to the above 2000 mL of lithium chloride solution, the temperature was raised to 95° C. and the mixture was stirred at this temperature for 1 h, then filtered while hot, and the filtrate was fixed to 2000 mL with water. The lithium content was 6.79 g / L and the calcium content was 0.0685 g / L. 5.5 g of phosphoric acid was added to the above filtrate to adjust the pH of the solution to 6.5, and then 108 g of sodium phosphate was added until the pH of the system was 9.3. The wet lithium phosphate product was filtered to obtain the wet lithium phosphate product. The wet lithium phosphate product was placed in a vacuum drying oven and heated to 105° C. and dried for 4 h to obtain 73.6 g of lithium phosphate product.

[0043] Comparative Example 2 A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from a ternary lithium battery positive electrode material, the specific steps are as follows:

[0044] (1) 100 g of lithium phosphate and 130 g of magnesium carbonate were mixed and ground until they passed through a 200-mesh sieve. The resulting mixture was placed in a muffle furnace and heated to 800° C., then calcined at 800° C. for 2 h. The muffle furnace was then cooled to 300° C. At 300° C., water vapor was introduced into the muffle furnace through an external interface for 2 h. The water vapor and heating device were then turned off, the material was taken out and cooled to room temperature, and 162.5 g was weighed.

[0045] (2) 162.5 g of the obtained material was placed in a ball mill, and 2000 mL of pure water was added and ball-milled for 1 hour. The magnesium phosphate solid and 2000 mL of lithium hydroxide solution were filtered to obtain the lithium content of 7.23 g / L and the magnesium content of 1.06 g / L in the lithium hydroxide solution. The lithium leaching rate was calculated to be 84.4%; 12 g of electronic grade oxalic acid was added to the above 2000 mL of lithium hydroxide solution, and the temperature was raised to 95° C. and stirred for 1 hour. The solution was then filtered while hot, and the filtrate was fixed to 2000 mL with water. The lithium content was 7.11 g / L and the magnesium content was 0.059 g / L. 89.3 g of industrial grade phosphoric acid was then added to the above filtrate until the pH of the system was 6.5. Then, 3.2 g of sodium phosphate was added until the pH of the system was 9.5. The wet lithium phosphate product was filtered to obtain the wet lithium phosphate product. The wet lithium phosphate product was placed in a vacuum drying oven and heated to 105° C. and dried for 4 hours to obtain 85.2 g of lithium phosphate product.

[0046] The components of the products of Comparative Example 1 and Comparative Example 2 were analyzed by ICP emission spectroscopy and the calculated sample purity results are shown in Table 2 below:

[0047] Table 2

[0048]

[0049] Note: The above contents are all in mass percentage.

Claims

1. A method for preparing battery-grade lithium phosphate from lithium phosphate recovered from the positive electrode material of nickel-cobalt-manganese ternary lithium battery, comprising the following steps: (1) Calcium carbonate and a crude lithium phosphate product obtained by adding sodium phosphate precipitation after recovering precious metals from the positive electrode material of a nickel-cobalt-manganese ternary lithium battery are mixed in a mass ratio of (1-5):1, and the mixture is ground and set aside; after ICP detection, the mass percentage content of each element in the crude lithium phosphate product is as follows: lithium 17.2%, calcium 0.04%, magnesium 0.05%, nickel 0.87%, manganese 0.06%, cobalt 0.12%, sodium 0.89%, sulfate 1.20%, iron 0.11%, and aluminum 0.02%; (2) calcining the ground mixture at 700-900°C for 2-5 hours, then cooling to 200-300°C and holding for 1-3 hours; introducing steam into the mixture during the holding process to promote the reaction; after the holding process, turning off the steam and heating device, taking out the mixture and cooling it to room temperature; adding deionized water to the cooled mixture at a liquid-to-solid ratio of (10-15) mL / g and wet grinding the mixture; filtering the resulting slurry to obtain a primary filtrate A; (3) Add oxalic acid in an amount equivalent to 2-3 times the amount of calcium in the primary filtrate A according to the calcium content, heat to 80-95°C, and stir for 0.5-2 hours to remove calcium. After the reaction is completed, filter while hot to obtain the secondary filtrate B; (4) Phosphoric acid is added to the secondary filtrate B until the pH is 6.0-6.5, and then sodium phosphate is added to adjust the pH of the system to 9-10, and the wet lithium phosphate is obtained by filtration; the wet lithium phosphate is placed in a vacuum drying oven and dried to obtain battery-grade lithium phosphate.

2. The method according to claim 1, characterized in that In step (2), when water vapor is introduced, it is ensured that the water vapor is in full contact with the materials according to the reaction materials to promote the reaction.

3. The method according to claim 1, characterized in that In step (4), the drying is carried out at 105° C. for 4 hours.

4. The method according to claim 1, wherein In step (2), the mass ratio of the calcium carbonate to the crude lithium phosphate is 1.3:1.

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