Separation method and application of mixed positive electrode material

Abstract

The invention provides a method for separating a mixed positive electrode material, the mixed positive electrode material comprises a lithium iron phosphate material and a nickel-cobalt-lithium material, and the method comprises the following steps: S1, mixing the mixed positive electrode material and a solution containing ferric iron salt to obtain a first mixed solution; s2, mechanically activating the first mixed solution to obtain a second mixed solution; and S3, separating the second mixed solution to obtain a precipitate containing iron phosphate substances and a third mixed solution. The invention also provides an application of the separation method in secondary battery recovery.

Description

Technical Field

[0001] The present application relates to the field of resource recovery technology, and in particular to a separation method of mixed positive electrode materials and applications thereof. Background Art

[0002] In recent years, the penetration rate of electric vehicles in various countries has exploded, which will also bring about a large number of power battery retirement problems. Ternary positive electrode materials are currently important positive electrode active materials for long driving range. Their main components, lithium, nickel, cobalt, etc., are all strategic scarce resources. At the same time, due to supply and demand relationships and ownership, their prices continue to rise. Phosphate-based positive electrode materials are cheap, have good safety performance, long cycle life, and good high-temperature performance, but compared with ternary materials, they still have disadvantages such as low compaction density and low capacity density. Therefore, mixing ternary materials with phosphate-based positive electrode materials as positive electrode materials for power batteries will be an important research direction for positive electrode material systems.

[0003] The mixed ternary materials and phosphate materials not only take advantage of the high density and compaction density of the ternary energy, but also give full play to the advantages of the low price and good cycle stability of the phosphate cathode materials. However, for the recovery of cathode materials in this mixed system, the main existing countermeasures are to first dissolve and leach all the ternary materials and lithium iron phosphate materials, and then purify and separate nickel, cobalt, manganese, iron, etc. step by step, and finally recover the lithium salt. This method has cumbersome steps and many process steps, which will bring a lot of secondary pollution and huge energy consumption, and the recovery rate of lithium is low. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present application provides a method for separating mixed positive electrode materials and applications thereof.

[0005] The first aspect of the present application provides a method for separating a mixed positive electrode material, wherein the mixed positive electrode material includes a lithium iron phosphate material and a nickel cobalt lithium material, and the method comprises the following steps:

[0006] S1: mixing the mixed positive electrode material and the solution containing the trivalent iron salt to obtain a first mixed solution;

[0007] S2: mechanically activating the first mixed solution to obtain a second mixed solution;

[0008] S3: Separating the second mixed solution to obtain a precipitate containing iron phosphate substances and a third mixed solution.

[0009] The present application uses selective leaching to leach lithium and separate nickel-cobalt-lithium materials and lithium iron phosphate materials, which not only reduces the separation process steps and the regeneration synthesis process steps, but also greatly improves the extraction efficiency of lithium. According to some embodiments of the present application, the mechanical activation of the first mixed solution is achieved by liquid-phase ball milling. In step S2, the surface characteristics of the particles are finely regulated by ball milling, and in particular, the surface coating layer can be removed to activate the surface of the particles. At the same time, the local thermal effect generated during the ball milling process can be combined with the shock wave pressure effect to cause the particles to react gradually in the centripetal direction, thereby reducing the transition metals in the nickel-cobalt-lithium materials and oxidizing the iron in the iron-lithium materials, thereby causing the original structure to fail and release lithium ions into the solution, while nickel, cobalt and other optional elements are reduced and leached in the low pH range.

[0010] According to some embodiments of the present application, the ball milling time is 1 h to 5 h, and the ball milling speed is 300 rpm to 600 rpm.

[0011] When the liquid phase ball milling time is less than 2 hours, the short ball milling time is insufficient for the particles to react fully in the centripetal direction, resulting in the inability to leach some lithium elements. When the ball milling time is too long, for example, more than 5 hours, the powder particles will be over-grinded, and the iron phosphate particles will be pulverized, causing the dissolution of P and Fe.

[0012] When the speed of liquid phase ball milling is too low, for example, the speed of ball milling is less than 300rpm, the force of ball milling in the centripetal and parallel directions of particles is too low, the surface peeling degree of material particles is weakened, resulting in a decrease in metal leaching rate. When the speed of liquid phase ball milling is too high, for example, the speed of ball milling is greater than 600rpm, the powder particles will be over-grinded, and the iron phosphate particles will be pulverized, causing the dissolution of P and Fe.

[0013] According to some embodiments of the present application, the mass ratio of the mixed positive electrode material to the ferric iron salt is 1:0.5 to 1:2, thereby controlling the concentration of ferric iron ions to inhibit the dissolution of Fe.

[0014] According to some embodiments of the present application, the pH of the solution containing the trivalent iron salt is 1 to 3.

[0015] According to some embodiments of the present application, in the solution containing the ferric iron salt, the concentration of the ferric iron salt is 50 g / L to 300 g / L.

[0016] According to some embodiments of the present application, the trivalent iron salt includes at least one of ferric sulfate, ferric chloride and ferric nitrate.

[0017] According to some embodiments of the present application, in the mixed positive electrode material, the mass ratio of lithium iron phosphate material to nickel cobalt lithium material is (0.1:10) to (10:0.1), preferably (1-10:1).

[0018] According to some embodiments of the present application, the nickel-cobalt-lithium material includes LiNi x Co y A (1-x-y) O 2 At least one of, wherein 0≤x≤1, 0≤y≤1, and the A element includes at least one of Mg, Mn, Cr, Fe, Al, Ga, Zr, Ti, Sb and W.

[0019] According to some embodiments of the present application, the lithium iron phosphate material includes LiFe z B (1-z) PO 4 At least one of, wherein 0≤z≤1, and the B element includes at least one of Mn, Co, Ti, Mg and Ca.

[0020] According to some embodiments of the present application, the mixed positive electrode material includes a substance obtained by pyrolysis of a positive electrode coating of a positive electrode plate of a secondary battery. Preferably, the pyrolysis is performed in an oxygen atmosphere at a temperature of 300°C-500°C.

[0021] According to some embodiments of the present application, the third mixed solution includes Li, Ni, Co and optionally element A, and element A includes at least one of Mg, Mn, Cr, Fe, Al, Ga, Zr, Ti, Sb and W. Preferably, the third mixed solution is used to prepare the nickel-cobalt-lithium material.

[0022] According to some embodiments of the present application, the iron phosphate substance includes Fe, P and an optional B element, the B element includes at least one of Mn, Co, Ti, Mg and Ca, and the iron phosphate substance is, for example, an iron phosphate salt.

[0023] The second aspect of the present application improves the application of the separation method described in the first aspect in secondary battery recycling.

[0024] According to some embodiments of the present application, the secondary battery recycling includes recycling of the positive electrode material in the secondary battery.

[0025] According to some embodiments of the present application, the secondary battery is a lithium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery, or a lithium polymer secondary battery.

[0026] According to some embodiments of the present application, the secondary battery is a secondary battery used in devices such as electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, mobile phones, tablet computers or laptop computers.

[0027] The beneficial effects of this application are:

[0028] The present application adopts trivalent iron salt as a redox agent and then mechanically grinds and activates it to achieve efficient and selective leaching of lithium, nickel, cobalt and optional manganese, etc. and to achieve the purpose of separation from phosphate. The valence state of Fe in the iron phosphate changes during the leaching process, lithium is leached, and Fe changes valence to form iron phosphate precipitation. The formed iron phosphate can be directly processed as a precursor for the synthesis of lithium iron phosphate materials. The lithium salt is selectively leached first to improve the leaching efficiency and reduce the loss in the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of a separation method according to one embodiment of the present application.

[0030] Figure 2 This is a SEM image of the positive electrode sheet in Example 1 of the present application. DETAILED DESCRIPTION

[0031] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0032] In the description herein, unless otherwise specified, “above” and “below” include the number.

[0033] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0034] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0035] The present application provides a method for separating mixed positive electrode materials, such as Figure 1 As shown, it includes the following steps:

[0036] (1) adding the mixed positive electrode material to a uniformly dispersed solvent containing trivalent iron, mechanically grinding the dispersion, and obtaining a ternary leaching solution containing elements such as Ni, Co, Mn and Li and an iron phosphate precipitate by a selective leaching and mechanical activation method;

[0037] (2) passing the ternary leaching solution into a precursor processing synthesis and lithium salt separation system to obtain a ternary material precursor and a lithium salt;

[0038] (3) introducing the ternary material precursor into a ternary synthesis system to obtain a regenerated nickel-cobalt-manganese ternary material NCM;

[0039] (4) Lithium salt and iron phosphate are introduced into the lithium iron phosphate synthesis system as precursors for lithium iron phosphate synthesis to obtain regenerated lithium iron phosphate LFP.

[0040] In some embodiments, discarded lithium iron phosphate and ternary material mixed positive electrode sheets are placed in an oxygen atmosphere for high-temperature pyrolysis, and the binder is removed by high-temperature pyrolysis to obtain the mixed positive electrode material powder of the present application.

[0041] The present application is further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0042] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0043] Examples and Comparative Examples

[0044] Example 1

[0045] The discarded lithium iron phosphate and ternary material mixed positive electrode sheets were cut into small strips of 2cm×4cm and placed in a porcelain ark, which was then pyrolyzed at 500°C in an oxygen atmosphere for 1h (heating rate 2°C / min), and the binder was removed by high-temperature pyrolysis to obtain the mixed positive electrode material powder.

[0046] Figure 2 This is a microscopic image of the surface of the mixed positive electrode sheet of this embodiment. Figure 2 It can be observed that large particles of ternary materials and small particles of lithium iron phosphate materials are mixed and evenly coated on the surface of the current collector.

[0047] The obtained mixed positive electrode powder is added to a specific acid solution (HNO 3 :HCl=3:1, V / V) and stirred at room temperature for 1h. The element content was tested by ICP-MS (7500ce, Agent) to determine the content of each element in the mixed material, especially the content of lithium, nickel, cobalt and iron. The ratio of lithium iron phosphate material and ternary material in the mixed material was determined to be 7:3 by calculation.

[0048] Weigh Fe 2 (SO4) 3 Put it in a 500mL beaker, add 300mL deionized water, prepare a ferric sulfate solution with a concentration of 250g / L, stir and disperse it with magnetic force for 1h, and then add an appropriate amount of sulfuric acid to adjust its pH to about 2. Weigh 50g of the mixed positive electrode material and add it to the above-mentioned ferric sulfate solution to obtain a first mixed solution, and then liquid-phase ball milling in a ball mill for 3h to complete the reaction, the ball milling speed is 500rpm, and a second mixed solution is obtained. The main components of the second mixed solution are precipitates of iron phosphate substances and leaching solutions containing elements such as lithium, nickel, cobalt, and manganese, among which the leaching rate of Li is 95.7%, that is, 95.7% by weight of the lithium element in the above-mentioned mixed positive electrode material is leached into the liquid part of the second mixed solution. The second mixed solution is centrifuged to obtain a solution containing elements such as lithium, nickel, cobalt, and manganese (the third mixed solution) and an iron phosphate precipitate. The iron phosphate precipitate is washed with deionized water and placed in an oven at 80°C for 12h. The obtained product iron phosphate is used as a precursor for the synthesis of lithium iron phosphate. The third mixed solution is slowly adjusted to pH 3 to 5 by adding ammonia water, and the remaining Fe ions are precipitated, and the fourth mixed solution is obtained by filtration. The ratio of nickel, cobalt, manganese and lithium in the fourth mixed solution is adjusted to be used as a raw material for the ternary synthesis process.

[0049] Example 2

[0050] The discarded lithium iron manganese phosphate and ternary material mixed positive electrode sheets cut into 2cm×4cm were placed in a porcelain ark, which was placed in an oxygen atmosphere for high-temperature pyrolysis at 450℃ for 0.5h (heating rate 2℃ / min). Part of the binder was pyrolyzed at high temperature to achieve the purpose of separating the powder and the electrode, and the powder was collected to obtain the mixed positive electrode material.

[0051] The obtained lithium iron manganese phosphate and ternary mixed positive electrode powder are added to a specific acid solution (HNO 3 :HCl=3:1, V / V) and stirred at room temperature for 1.5h. The element content was tested by ICP-MS (7500ce, Agent) to determine the content of each element in the mixed material, especially the content of lithium, nickel, cobalt and iron. The ratio of lithium iron manganese phosphate material and ternary material in the mixed material was determined to be 8:2 by calculation.

[0052] Weigh Fe 2 (SO 4 ) 3 Put it in a 500mL beaker, add 300mL deionized water, configure a ferric sulfate solution with a concentration of 200g / L, disperse it with magnetic stirring for 1h, and then add an appropriate amount of sulfuric acid to adjust the pH of the ferric sulfate solution to about 1.5. Weigh 50g of mixed positive electrode material and add it to the above-mentioned ferric sulfate solution to obtain a first mixed solution, then disperse it under mechanical grinding conditions for 3h to complete the reaction, the ball mill speed is 500rpm, and a second mixed solution is obtained, wherein the leaching rate of the Li element is 96.2%. The main components of the second mixed solution are the precipitation of iron phosphate and the leachate of lithium, nickel, cobalt, manganese, etc. The second mixed solution is centrifuged to obtain a solution of lithium, nickel, cobalt, manganese, etc. (the third mixed solution) and an iron manganese phosphate precipitation.

[0053] Example 3

[0054] Example 3 was carried out with reference to Example 1, except that the liquid phase ball milling time was 1.8 h. Due to the shorter time, the Li leaching rate obtained in Example 3 was 81.4%.

[0055] Example 4

[0056] Example 4 was carried out with reference to Example 1, except that the liquid phase ball milling time was 4 hours. The Li leaching rate obtained in Example 4 was 95.9%.

[0057] Example 5

[0058] Example 5 was carried out with reference to Example 1, except that the speed of liquid phase ball milling was 300 rpm. The leaching rate of Li obtained in Example 5 was 87.2%.

[0059] Example 6

[0060] Example 5 was carried out with reference to Example 1, except that the speed of the liquid phase ball milling was different, which was 800 rpm. The leaching rate of Li obtained in Example 6 was 94.5%, but 26.1% of Fe and 14% of P were also leached into the liquid phase of the second mixed solution. The leaching rates of Fe and P in the liquid phase of the second mixed solution in Example 1 were both less than 0.5%.

[0061] Comparative Example 1

[0062] Comparative Example 1 was carried out with reference to Example 1, except that no ball milling was performed. The Li leaching rate obtained in Comparative Example 1 was 1.7%.

[0063] Comparative Example 2

[0064] Comparative Example 2 was carried out with reference to Example 1, except that the mixed positive electrode powder was firstly subjected to ball milling treatment and then mixed with the ferric sulfate solution. The Li leaching rate obtained in Comparative Example 2 was 62.3%.

[0065] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that some modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.

Claims

1. A method for separating a mixed positive electrode material, wherein the mixed positive electrode material comprises a lithium iron phosphate material and a nickel cobalt lithium material, The following steps are involved: S1: mixing the mixed positive electrode material and the solution containing the trivalent iron salt to obtain a first mixed solution; S2: mechanically activating the first mixed solution to obtain a second mixed solution; S3: Separating the second mixed solution to obtain a precipitate containing iron phosphate substances and a third mixed solution.

2. The separation method according to claim 1, It is characterized in that The mechanical activation of the first mixed solution is achieved by liquid phase ball milling.

3. The separation method according to claim 2, It is characterized in that The ball milling time is 1h to 5h; and / or The ball milling speed is 300 rpm to 600 rpm.

4. The separation method according to claim 1, It is characterized in that The mass ratio of the mixed positive electrode material to the trivalent iron salt is 1:0.5 to 1:

2.

5. The separation method according to claim 1, It is characterized in that The pH of the solution comprising the ferric salt is 1 to 3; and / or The solution comprising the ferric iron salt has a concentration of the ferric iron salt of 50 g / L to 300 g / L; and / or The ferric iron salt includes at least one of ferric sulfate, ferric chloride and ferric nitrate.

6. The separation method according to claim 1, It is characterized in that In the mixed positive electrode material, the mass ratio of lithium iron phosphate material to nickel cobalt lithium material is 0.1:10-10:0.1, preferably (1-10):

1.

7. The separation method according to claim 1, It is characterized in that The nickel-cobalt-lithium material includes LiNi x Co y A (1-x-y) O 2 At least one of, wherein 0≤x≤1, 0≤y≤1, and the A element comprises at least one of Mg, Mn, Cr, Fe, Al, Ga, Zr, Ti, Sb and W; and / or The lithium iron phosphate material includes LiFe z B (1-z) PO 4 At least one of, wherein 0≤z≤1, and the B element includes at least one of Mn, Co, Ti, Mg, V and Ca.

8. The separation method according to claim 1, It is characterized in that The mixed positive electrode material includes a material obtained by pyrolysis of a coating of a positive electrode plate of a secondary battery. Preferably, the pyrolysis is performed in an oxygen atmosphere at a temperature of 300°C to 500°C.

9. The separation method according to claim 7, It is characterized in that The third mixed solution comprises Li, Ni, Co and an optional A element, wherein the A element comprises at least one of Mg, Mn, Cr, Fe, Al, Ga, Zr, Ti, Sb and W. Preferably, the third mixed solution is used to prepare the nickel-cobalt-lithium material; and / or The iron phosphate material includes Fe, P and an optional B element, and the B element includes at least one of Mn, Co, Ti, Mg and Ca.

10. Use of the separation method according to any one of claims 1 to 9 in secondary battery recycling.

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