Application of poly-2-acrylamide-2-methylpropanesulfonic acid in removal of residual lithium on surface of high-nickel NCM ternary material

Abstract

The invention provides application of poly-2-acrylamide-2-methylpropanesulfonic acid in removal of residual lithium on the surface of a high-nickel NCM ternary material, and relates to the technical field of surface treatment of the high-nickel NCM ternary material. The method aims at solving the problem that an existing method for removing lithium carbonate on the surface of an NCM material through high-temperature calcination or high-concentration ethyl alcohol soaking and cleaning has adverse effects on the structure and performance of the high-nickel NCM ternary material. According to the invention, the cleaning agent using poly-2-acrylamide-2-methylpropanesulfonic acid as a main component is provided for cleaning the residual lithium of the high-nickel NCM ternary material, and verification proves that the high-nickel NCM ternary material can be effectively prevented from being damaged by existing high-temperature calcination and high-concentration ethanol soaking and cleaning treatment, and meanwhile, the electrochemical performance of the high-nickel NCM ternary material is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of surface treatment of high-nickel NCM ternary materials, and in particular to application of poly 2-acrylamide-2-methylpropane sulfonic acid in removing residual lithium on the surface of high-nickel NCM ternary materials. Background Art

[0002] With the rapid development of electric vehicles, portable electronic devices and energy storage systems, lithium-ion battery technology has been widely used and developed rapidly in the past few decades. As the positive electrode material of the new generation of lithium-ion batteries, high-nickel NCM (nickel cobalt manganese oxide) ternary materials have attracted widespread attention due to their high energy density and low cost. However, during the synthesis and use of high-nickel NCM ternary materials, the residual lithium content on the surface increases, and the residual lithium easily reacts with water and carbon dioxide to form lithium carbonate (Li 2 CO 3 ) and other by-products, which not only affect the cycle performance and rate performance of the battery, but may also cause safety hazards to the battery.

[0003] Traditional technologies usually use high-temperature calcination or organic washing methods to remove lithium carbonate from the surface of NCM materials. The high-temperature calcination method heats the NCM material under high temperature to decompose the lithium carbonate on the surface into carbon dioxide and lithium oxide, thereby removing residual lithium. The organic washing method soaks the NCM material in high-concentration ethanol to dissolve the lithium carbonate on the surface, thereby removing residual lithium. However, these methods have problems such as complex operation, high energy consumption and environmental pollution, and in the process of removing lithium carbonate, they may have an adverse effect on the structure and performance of the material.

[0004] Therefore, it is particularly important to research and develop a new treatment method that is efficient, environmentally friendly and will not damage the material itself.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide an acid detergent and a treatment method for removing residual lithium on the surface of high-nickel NCM ternary materials. After treatment with the acid detergent and method of the present application, the damage to the high-nickel NCM ternary materials caused by existing high-temperature calcination and organic water washing treatment can be effectively avoided, while significantly improving the electrochemical properties of the materials.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] The invention discloses an application of the poly 2-acrylamide-2-methylpropane sulfonic acid in removing residual lithium from the surface of a high-nickel NCM ternary material.

[0009] Furthermore, the nickel content in the high-nickel NCM ternary material is greater than 80%.

[0010] Furthermore, the residual lithium on the surface of the high-nickel NCM ternary material is lithium carbonate formed on the surface of the high-nickel NCM ternary material during the synthesis and use of the high-nickel NCM ternary material.

[0011] The present invention provides an acid washing solution for removing residual lithium on the surface of a high-nickel NCM ternary material, characterized in that the acid washing solution is mainly prepared by dissolving poly 2-acrylamide-2-methylpropane sulfonic acid in a solvent.

[0012] Further, the solvent includes any one of phosphoric acid, boric acid, and N-methylpyrrolidone;

[0013] Furthermore, the concentration of poly (2-acrylamide-2-methylpropanesulfonic acid) in the acid washing solution is 0.5-1.5 wt %.

[0014] The present invention provides a method for treating residual lithium on the surface of a high-nickel NCM ternary material, characterized in that the treatment method comprises:

[0015] The acid washing liquid is mixed with the high-nickel NCM ternary material to be treated and stirred, and then filtered, and the filtered product is dried to complete the treatment.

[0016] Furthermore, in the treatment process, the mass ratio of the acid washing solution to the high-nickel NCM ternary material to be treated is 1:(50-200).

[0017] Furthermore, the stirring speed is 600-1200 rpm, and the stirring time is 0.5-2 h.

[0018] Furthermore, the filtration is vacuum filtration, the temperature of the vacuum filtration is 20 to 25° C., and the pressure of the vacuum filtration is -0.06 to -0.10 MPa.

[0019] Furthermore, the drying temperature is 80-120° C., and the drying time is 1-4 hours.

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

[0021] The invention provides an application of poly 2-acrylamide-2-methylpropane sulfonic acid in removing residual lithium from the surface of high-nickel NCM ternary materials. In view of the problems that the existing methods of removing lithium carbonate from the surface of NCM materials by high-temperature calcination or organic high-concentration ethanol immersion cleaning have adverse effects on the structure and performance of high-nickel NCM ternary materials, this application creatively proposes to use poly 2-acrylamide-2-methylpropane sulfonic acid as a cleaning agent with the main component to clean the residual lithium of high-nickel NCM ternary materials. It has been verified that it can effectively avoid the damage of the existing high-temperature calcination and organic water washing treatment to the high-nickel NCM ternary materials, and at the same time significantly improve the electrochemical performance of the materials.

[0022] The acid washing solution provided by the present invention has a main solute component of poly 2-acrylamide-2-methylpropane sulfonic acid. The acid washing solution can effectively remove the lithium carbonate content on the surface of the high-nickel NCM ternary material and improve the electrochemical performance of the high-nickel NCM ternary material.

[0023] The method for treating residual lithium on the surface of a high-nickel NCM ternary material provided by the present invention comprises first mixing the acid washing solution with the high-nickel NCM ternary material to be treated and stirring the mixture, then filtering the mixture by suction, and drying the filtered product to obtain the treated high-nickel NCM ternary material. The method has the technical advantages of being environmentally friendly and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The third cycle discharge specific capacity diagram of Examples 1 to 3, the base group and the bare group provided in Test Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] According to one aspect of the present invention, poly (2-acrylamide-2-methylpropane sulfonic acid) is used in removing residual lithium from the surface of high-nickel NCM ternary materials.

[0028] The invention provides an application of poly 2-acrylamide-2-methylpropane sulfonic acid in removing residual lithium from the surface of high-nickel NCM ternary materials. In view of the problems that the existing methods of removing lithium carbonate from the surface of NCM materials by high-temperature calcination or organic high-concentration ethanol immersion cleaning have adverse effects on the structure and performance of high-nickel NCM ternary materials, this application creatively proposes to use poly 2-acrylamide-2-methylpropane sulfonic acid as a cleaning agent with the main component to clean the residual lithium of high-nickel NCM ternary materials. It has been verified that the existing high-temperature calcination and organic water washing treatment can effectively avoid the damage to the high-nickel NCM ternary materials, and significantly improve the electrochemical performance of the materials.

[0029] It should be noted that, after research, the present applicant found that although poly 2-acrylamide-2-methylpropane sulfonic acid (PAMPS) is a strong acid, due to its specific molecular structure and the processing application method of the present application, it can reduce damage to the material during the removal process of residual lithium on the surface of high-nickel NCM ternary materials.

[0030] In a preferred embodiment of the present invention, the nickel content in the high-nickel NCM ternary material is greater than 80%.

[0031] In a preferred embodiment of the present invention, the residual lithium on the surface of the high-nickel NCM ternary material is lithium carbonate formed on the surface of the high-nickel NCM ternary material during the synthesis and use of the high-nickel NCM ternary material.

[0032] According to one aspect of the present invention, an acid washing solution is provided for removing residual lithium from the surface of a high-nickel NCM ternary material. The acid washing solution is mainly prepared by dissolving poly 2-acrylamide-2-methylpropane sulfonic acid in a solvent.

[0033] The acid washing solution provided by the present invention has a main solute component of poly 2-acrylamide-2-methylpropane sulfonic acid, and the acid washing solution can effectively remove the residual lithium (lithium carbonate) content on the surface of the high-nickel NCM ternary material.

[0034] In a preferred embodiment of the present invention, the solvent includes any one of phosphoric acid, boric acid, and N-methylpyrrolidone;

[0035] In the above preferred embodiment, the concentration of poly (2-acrylamide-2-methylpropanesulfonic acid) in the acid washing solution is 0.5 to 1.5 wt %.

[0036] As a preferred embodiment, the concentration of poly 2-acrylamide-2-methylpropane sulfonic acid in the above-mentioned acid washing solution is 0.5-1.5wt%. Too high a concentration will lead to structural decay of the high-nickel NCM ternary material, and too low a concentration will have a poor effect in removing lithium carbonate.

[0037] According to one aspect of the present invention, a method for treating residual lithium on the surface of a high-nickel NCM ternary material comprises:

[0038] The acid washing liquid is mixed with the high-nickel NCM ternary material to be treated and stirred, and then filtered, and the filtered product is dried to complete the treatment.

[0039] The method for treating residual lithium on the surface of a high-nickel NCM ternary material provided by the present invention comprises first mixing the acid washing solution with the high-nickel NCM ternary material to be treated and stirring the mixture, then filtering the mixture by suction, and drying the filtered product to obtain the treated high-nickel NCM ternary material. The method has the technical advantages of being environmentally friendly and easy to operate.

[0040] In a preferred embodiment of the present invention, the mass ratio of the acid washing solution to the high-nickel NCM ternary material to be treated during the treatment process is 1:(50-200).

[0041] In a preferred embodiment of the present invention, the stirring speed is 600-1200 rpm, and the stirring time is 0.5-2 h.

[0042] In a preferred embodiment of the present invention, the filtration is vacuum filtration, the temperature of the vacuum filtration is 20 to 25° C., and the pressure of the vacuum filtration is -0.06 to -0.10 MPa.

[0043] In a preferred embodiment of the present invention, the drying temperature is 80-120° C., and the drying time is 1-4 hours.

[0044] Preferably, the method for treating residual lithium on the surface of the high-nickel NCM ternary material comprises:

[0045] S1: First, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) monomer and N-methylpyrrolidone (NMP) solvent are mixed and stirred, and then an initiator azobisisobutyronitrile (AIBN) is added to induce monomer polymerization to prepare poly (2-acrylamide-2-methylpropanesulfonic acid) (PAMPS);

[0046] S2: poly (2-acrylamide-2-methylpropane sulfonic acid) (PAMPS) and N-methylpyrrolidone (NMP) were mixed to form acid detergents with different mass fractions;

[0047] S3: mixing the acid detergent with the nickel-cobalt-manganese ternary material (NCM) having an aging time of 7 days;

[0048] S4: The mixture is filtered and dried to obtain an acid-washed product.

[0049] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0050] Note: The "high nickel NCM ternary material with an aging time of 7 days" in the following examples and comparative examples refers to the high nickel NCM ternary material exposed to hot and humid air for 7 days, and its surface is covered with lithium carbonate. The following examples and comparative examples all use the same batch of high nickel NCM ternary materials with an aging time of 7 days, and their raw materials, specifications, performance parameters, aging time and degree are all at the same level.

[0051] Example 1

[0052] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0053] (1) Preparation of acid detergent: 1 g of 2-acrylamide-2-methylpropane sulfonic acid (AMPS) was added to 5 mL of N-methylpyrrolidone (NMP) solvent to form a sealant seal, and ultrasonically stirred for 10 min. Then, 0.02 g of azobisisobutyronitrile (AIBN) was added and placed at 60° C. for 24 h to polymerize the monomers to obtain a poly(2-acrylamide-2-methylpropane sulfonic acid) (PAMPPS) solution, which was mixed with N-methylpyrrolidone (NMP) to prepare an acid detergent with a mass fraction of 0.5 wt%.

[0054] (2) Acid washing step: The NCM aged for 7 days was mixed with 0.5 wt% of an acid detergent and stirred at a speed of 1000 rpm for 2 h, followed by vacuum filtration. The filtered product was placed in a vacuum oven at 100° C. and dried for 2 h to obtain a final acid-treated product.

[0055] Example 2

[0056] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0057] (1) Preparation of acid detergent: 1 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) was added to 5 mL of N-methylpyrrolidone (NMP) solvent and sealed with sealant. The mixture was ultrasonically stirred for 10 min, and then 0.02 g of azobisisobutyronitrile (AIBN) was added. The mixture was placed at 60° C. for 24 h to polymerize the monomers to obtain 2-acrylamide-2-methylpropanesulfonic acid (PAMPPS) solution, which was then mixed with N-methylpyrrolidone (NMP) to prepare an acid detergent with a mass fraction of 1.0 wt%.

[0058] (2) Acid washing step: The NCM aged for 7 days was mixed with 1.0 wt% of an acid detergent and stirred at a speed of 1000 rpm for 2 h, followed by vacuum filtration. The filtered product was placed in a vacuum oven at 100° C. and dried for 2 h to obtain a final acid-treated product.

[0059] Example 3

[0060] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0061] (1) Preparation of acid detergent: 1 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) was added to 5 mL of N-methylpyrrolidone (NMP) solvent and sealed with sealant. The mixture was ultrasonically stirred for 10 min, and then 0.02 g of azobisisobutyronitrile (AIBN) was added. The mixture was placed at 60° C. for 24 h to polymerize the monomers to obtain 2-acrylamide-2-methylpropanesulfonic acid (PAMPPS) solution, which was then mixed with N-methylpyrrolidone (NMP) to prepare acid detergents with different mass fractions of 1.5 wt %.

[0062] (2) Acid washing step: The NCM aged for 7 days was mixed with 1.5 wt% of an acid detergent at a speed of 1000 rpm for 2 h, followed by vacuum filtration. The filtered product was placed in a vacuum oven at 100° C. and dried for 2 h to obtain a final acid-treated product.

[0063] Example 4

[0064] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0065] (1) Preparation of acid detergent: 1 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) was added to 5 mL of N-methylpyrrolidone (NMP) solvent and sealed with sealant. The mixture was ultrasonically stirred for 10 min, and then 0.02 g of azobisisobutyronitrile (AIBN) was added. The mixture was placed at 60° C. for 24 h to polymerize the monomers to obtain a 2-acrylamide-2-methylpropanesulfonic acid (PAMPPS) solution, which was then mixed with N-methylpyrrolidone (NMP) to prepare an acid detergent with a mass fraction of 2.0 wt%.

[0066] (2) Acid washing step: The NCM aged for 7 days was mixed with 2.0 wt% of an acid detergent and stirred at a speed of 1000 rpm for 2 h, followed by vacuum filtration. The filtered product was placed in a vacuum oven at 100° C. and dried for 2 h to obtain a final acid-treated product.

[0067] The difference between this embodiment and embodiment 1 is that 2.0 wt % of acid detergent is used for pickling treatment.

[0068] Example 5

[0069] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0070] (1) Preparation of acid detergent: 1 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) was added to 5 mL of N-methylpyrrolidone (NMP) solvent and sealed with sealant. The mixture was ultrasonically stirred for 10 min, and then 0.02 g of azobisisobutyronitrile (AIBN) was added. The mixture was placed at 60° C. for 24 h to polymerize the monomers to obtain a 2-acrylamide-2-methylpropanesulfonic acid (PAMPPS) solution, which was then mixed with N-methylpyrrolidone (NMP) to prepare an acid detergent with a mass fraction of 0.3 wt%.

[0071] (2) Acid washing step: The NCM aged for 7 days was mixed with 0.3 wt% of an acid detergent at a speed of 1000 rpm for 2 h, followed by vacuum filtration. The filtered product was placed in a vacuum oven at 100° C. and dried for two hours to obtain a final acid-treated product.

[0072] The difference between this embodiment and embodiment 1 is that 0.3 wt % of acid detergent is used for pickling treatment.

[0073] Example 6

[0074] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0075] (1) Preparation of acid detergent: same as in Example 1.

[0076] (2) Acid washing step: The NCM aged for 7 days was mixed with 0.5 wt% of an acid detergent and stirred at a speed of 1000 rpm for 2 h, followed by vacuum filtration. The filtered product was placed in a vacuum oven at 120° C. and dried for 2 h to obtain a final acid-treated product.

[0077] Comparative Example 1

[0078] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0079] Acid washing step: NCM aged for 7 days was mixed with 0.5 wt% polyacrylic acid detergent at a speed of 1000 rpm for 2 hours, followed by vacuum filtration, and the filtered product was placed in a vacuum oven at 100° C. and dried for 2 hours to obtain the final acid-treated product.

[0080] The difference between this comparative example and Example 1 is that polyacrylic acid is used to replace poly 2-acrylamide-2-methylpropane sulfonic acid (PAMPPS) to prepare the acid detergent.

[0081] Comparative Example 2

[0082] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0083] Acid washing step: The NCM aged for 7 days was mixed with 0.5 wt% poly (2-acrylamide-2-methylpropanesulfonic acid) (PAMPPS) acid detergent at a speed of 1000 rpm for 2 h, followed by evaporation and crystallization, and the product was placed in a vacuum oven at 100° C. and dried for 2 h to obtain the final acid-treated product.

[0084] Comparative Example 3

[0085] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0086] The NCM aged for 7 days was 2 The product was calcined at 800°C for 3 h in an atmosphere to obtain a final high-temperature calcined product.

[0087] Comparative Example 4

[0088] A method for treating residual lithium on the surface of a high-nickel NCM ternary material, the method comprising:

[0089] The NCM aged for 7 days was mixed with 2.0 wt% of glycolic acid detergent at a speed of 1000 rpm for 2 hours, and then evaporated and crystallized. The product was placed in a vacuum oven at 100° C. and dried for 2 hours to obtain the final acid-treated product.

[0090] Test Example 1

[0091] In order to show that the acid detergent of the present application can effectively remove the residual lithium content on the surface of the high-nickel NCM ternary material with an aging time of 7 days. This test example now tests the third cycle discharge specific capacity and coulomb efficiency of the high-nickel NCM ternary materials treated in Examples 1 to 6 and Comparative Examples 1 to 4, and the specific results are as follows:

[0092]

[0093]

[0094] Figure 1 The third cycle discharge specific capacity of Examples 1 to 3, the base group and the bare group provided in this test example.

[0095] Note: Figure 1 The base group (control group) is a high-nickel NCM ternary material with an aging time of 7 days, which has not been treated in any way; the bare group refers to a high-nickel NCM ternary material with an aging time of 7 days, that is, a high-nickel NCM ternary material exposed to hot and humid air for 7 days, and its surface is covered with lithium carbonate.

[0096] From the above, it can be seen that the high-nickel positive electrode material obtained after treatment in Examples 1 to 3 of the present application has improved third-cycle discharge specific capacity and coulombic efficiency compared with the untreated control group, indicating that the high-nickel positive electrode material has a good effect in removing lithium carbonate from the surface.

[0097] Compared with Examples 1 to 3, in Examples 4 and 5, the pickling solution with a poly 2-acrylamide-2-methylpropane sulfonic acid concentration higher than 1.5wt% will cause the structural decay of the high-nickel NCM ternary material, while the pickling solution with a poly 2-acrylamide-2-methylpropane sulfonic acid concentration lower than 0.5wt% is not effective in removing lithium carbonate. Compared with Examples 1 to 3, in Example 6, the embodiment of the vacuum filtration temperature of Examples 1 to 3 of the present application is 100°C, which is better than the embodiment of Example 6 with a vacuum filtration temperature of 120°C.

[0098] Compared with Examples 1 to 3, the effect of poly 2-acrylamide-2-methylpropane sulfonic acid (PAMPPS) in removing lithium carbonate in Comparative Example 1 is better than that of polyacrylic acid. Compared with Examples 1 to 3, the effect of vacuum filtration in Comparative Example 2 is better than that of evaporative crystallization. By comparing Comparative Examples 3 and 4 with Examples 1 to 3, it is found that the treatment methods of Examples 1 to 3 of the present application can effectively avoid the damage to high-nickel NCM ternary materials caused by existing high-temperature calcination and high-concentration ethanol immersion cleaning treatments, and at the same time significantly improve the electrochemical performance of high-nickel NCM ternary materials.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Application of poly (2-acrylamide-2-methylpropane sulfonic acid) in removing residual lithium from the surface of high-nickel NCM ternary materials.

2. The use according to claim 1, characterized in that: The nickel content in the high-nickel NCM ternary material is greater than 80%.

3. The use according to claim 1, characterized in that: The residual lithium on the surface of the high-nickel NCM ternary material is lithium carbonate formed on the surface of the high-nickel NCM ternary material during the synthesis and use process.

4. An acid washing solution for removing residual lithium from the surface of high-nickel NCM ternary materials, characterized in that: The acid washing solution is mainly prepared by dissolving poly 2-acrylamide-2-methylpropane sulfonic acid in a solvent.

5. The acid cleaning solution according to claim 4, characterized in that The solvent includes any one of phosphoric acid, boric acid, and N-methylpyrrolidone; Preferably, the concentration of poly (2-acrylamide-2-methylpropanesulfonic acid) in the acid washing solution is 0.5 to 1.5 wt %.

6. A method for treating residual lithium on the surface of high-nickel NCM ternary material, characterized in that: The processing method comprises: The acid washing solution according to claim 4 or 5 is mixed with the high-nickel NCM ternary material to be treated and stirred, and then filtered, and the filtered product is dried to complete the treatment.

7. The processing method according to claim 6, characterized in that: During the treatment process, the mass ratio of the acid washing solution to the high-nickel NCM ternary material to be treated is 1:(50-200).

8. The processing method according to claim 6, characterized in that: The stirring speed is 600-1200 rpm, and the stirring time is 0.5-2 h.

9. The processing method according to claim 6, characterized in that: The filtration is vacuum filtration, the temperature of the vacuum filtration is 20 to 25° C., and the pressure of the vacuum filtration is -0.06 to -0.10 MPa.

10. The processing method according to claim 6, characterized in that: The drying temperature is 80-120° C., and the drying time is 1-4 hours.

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