Method and product for direct regeneration of waste lithium-ion battery positive electrode black powder

Abstract

The present invention discloses a method for quickly and directly regenerating waste lithium-ion battery positive electrode black powder into positive electrode material by lithiation reaction at room temperature and pressure combined with rapid heat treatment. An organic lithium solution is obtained by reacting a lithium salt with a specific solvent at room temperature and pressure; then the failed positive electrode black powder is mixed with the organic lithium solution, stirred and reacted at room temperature and pressure to achieve lithiation, and the solution after the reaction is recovered and reused. After the solid obtained by the reaction is separated and dried, it can be regenerated into a positive electrode material after high-temperature sintering for a period of time, and its performance is restored to the same level as commercial positive electrode materials, and it can be reused in the production of lithium batteries. The method is simple to operate, does not require exogenous conditions such as heating and pressurization, has low equipment requirements, is low in cost, and has high value of recovered products.

Description

Technical Field

[0001] The invention belongs to the technical field of waste lithium-ion battery material recycling, and in particular relates to a method and product for directly regenerating waste lithium-ion battery positive electrode black powder. Background Art

[0002] In the recycling process of waste batteries, after pre-treatment, including crushing, sorting, separation and other steps, the part with the highest recycling value, including positive electrode active substances, is called black powder, which is the main treatment object in the actual recycling process. In existing patent reports, the main method for treating black powder is mainly based on the improvement of the wet route to extract the valuable metals therein. Due to the high price of lithium salts, the extraction of lithium has received the most attention. For example, the patent discloses a method for recovering valuable metals from waste lithium-ion battery black powder by carbon thermal reduction and preparing lithium carbonate products (application number: 202211068390.7), a method for recovering high-purity lithium oxalate and high-purity lithium hydroxide from waste lithium battery dismantling black powder and / or waste lithium battery positive electrode powder (application number: 202211427014.2), a method for selectively leaching and recovering lithium from waste lithium-ion battery black powder (application number: 202310043626.X), and a method for selectively extracting lithium from waste lithium-ion battery black powder and cleanly utilizing all components (application number: 202310370070.5). All of them use an improved wet process to leach the black powder, and then preferentially extract and recover the lithium in the form of lithium salt. There are also a small number of patents that focus on other metals besides lithium recovery, mainly nickel, manganese, and cobalt, which are of higher value. For example, a method for recovering nickel, cobalt, manganese, and lithium from waste power lithium-ion battery black powder (application number: 202010354105.2). Overall, the existing methods for recovering waste lithium-ion battery black powder are based on the wet leaching process, which often requires a large amount of acid and alkali reagents, and there are many reaction steps, requiring reduction roasting, acid leaching, pH adjustment, precipitation, separation and other steps. The obtained products are mainly various lithium salts, which can only be used as precursors in the positive electrode production process. They also need to be mixed and roasted for a long time before new positive electrode materials can be obtained. The use of acid and alkali reagents will produce a large amount of wastewater, and its treatment will not only increase costs, but also pose environmental risks.

[0003] For the widely used lithium iron phosphate cathode material with a market share of over 50%, the price of iron is too low and recycling is not very meaningful. The wet recycling method must ensure that the lithium recovery rate reaches an extremely high level in order to achieve profitability. However, the decline in the price of lithium carbonate in recent years has made the wet recycling of lithium iron phosphate basically unprofitable. The industry urgently needs to develop a new clean and efficient recycling method. Summary of the invention

[0004] The first aspect of the present invention is to address the deficiencies of the prior art and to propose a low-cost method for directly regenerating black powder from positive electrodes of waste lithium-ion batteries.

[0005] The present invention provides a method for directly regenerating waste lithium-ion battery positive electrode black powder, comprising the following steps:

[0006] S1. Dismantling, sorting and pre-treating waste lithium-ion batteries to obtain positive electrode material black powder;

[0007] S2. Stirring a lithium salt and an organic solvent at room temperature and pressure to react to prepare an organic lithium solution; the lithium salt is one or a combination of lithium chloride, lithium sulfate, lithium acetate, lithium carbonate, lithium hydroxide, lithium iodide, lithium bromide, and lithium nitrate, and the organic solvent is at least one of methanol, ethanol, tert-butanol, isopentanol, n-pentanol, acetonitrile, and N-methylpyrrolidone; the mass ratio of the total mass of the lithium salt to the organic solvent is 1:100 to 25:100, and when two lithium salts are used, the mass ratio of the two lithium salts is 1:1 to 1:20; then placing the black powder in the organic lithium solution, stirring and reacting at room temperature and pressure to obtain lithiated black powder;

[0008] S3. After solid-liquid separation and drying of the lithiated black powder and the solution, heat treatment is performed to obtain a regenerated positive electrode material; the dried solid is subjected to a stepwise heat treatment, wherein the temperature of the first stage is 200-500°C, the heat treatment time is 0.5-15h, and the heat treatment atmosphere is at least one of air, nitrogen, argon-hydrogen mixture, argon, oxygen, and carbon dioxide; the temperature of the second stage is 600-1000°C, the heat treatment time is 0.5-15h, and the heat treatment atmosphere is at least one of air, nitrogen, argon-hydrogen mixture, argon, oxygen, and carbon dioxide.

[0009] As a preferred solution, in step S1, the positive electrode material is at least one of lithium cobalt oxide, lithium iron phosphate, nickel manganese cobalt ternary material, and lithium manganese oxide.

[0010] As a preferred solution, in step S2, the solid-liquid ratio of the reaction between the black powder and the organic lithium solution is not greater than 1:1, and the reaction time is not less than 1 hour.

[0011] As a preferred solution, in step S3, the lithiated black powder and the solution after the reaction are separated into solid and liquid by pressure filtration or suction filtration.

[0012] As a preferred solution, in step S3, the solid after solid-liquid separation is vacuum dried at a drying temperature of 60-120°C.

[0013] The second aspect of the present invention is to address the deficiencies of the prior art and propose an electrode sheet of material for an electrode material layer produced by the above-mentioned method for directly regenerating waste lithium-ion battery positive electrode black powder.

[0014] A pole piece of the present invention comprises a current collector and an electrode material layer arranged on the surface of the current collector, wherein the material of the electrode material layer comprises the regenerated positive electrode material prepared as described in any one of the above items.

[0015] A third aspect of the present invention is to address the deficiencies of the prior art and to provide a lithium-ion battery comprising the pole piece described above.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention constructs a medium between lithium and the failed positive electrode by designing an organic lithium complex, and uses the adsorption effect of organic groups on the surface of black powder particles to play a bridging role, thereby reducing the thermodynamic barrier of the lithiation regeneration reaction, so that lithium can be spontaneously adsorbed to the surface of black powder particles at room temperature and pressure without the need for external driving force (such as heating, pressurization, power supply, etc.) to achieve the lithiation process, greatly simplifying the process conditions and required equipment for direct regeneration, and only one step of solid-liquid reaction and one step of heat treatment are required to achieve the transformation from the scrapped positive electrode to a new positive electrode material. Compared with the existing wet recovery method by finding a solvent combination that can dissolve the positive electrode and the existing direct recovery method by driving the lithium ions in the liquid to diffuse into the failed positive electrode to achieve lithiation repair through a combination of external forces, the present invention greatly reduces the cost of battery black powder regeneration and greatly reduces the discharge of waste, so that the method can be commercially applied on a large scale, and truly realizes the recycling of the positive electrode of discarded lithium ion batteries.

[0018] The method provided by the present invention does not involve the use of strong acid reagents, and the selected organic solvent is basically a common green and harmless reagent, and the amount used is small. It can also be collected and reused after the solid-liquid reaction, so the discharge of waste and wastewater is greatly reduced, and the reagent cost and environmental protection cost are greatly reduced. By utilizing the substitution reaction that is easy to occur under mild conditions, by adjusting the type and ratio of lithium salts, and the type of organic solvent, an organic lithium solution can be prepared only by mechanical stirring at normal temperature and pressure. Subsequently, by utilizing the high affinity of the long-chain organic groups in the organic lithium molecules for the surface of the failed positive electrode material particles, the lithiation process of the failed positive electrode material can be achieved at normal temperature and pressure by simple mechanical stirring. Since no additional heating, pressurization, power-on and other steps are required, and the use of strong acid and alkali reagents is not involved, the requirements for actual production equipment are greatly reduced, and the reaction can be completed using a conventional solid-liquid reaction container, which is convenient for large-scale application. After the solid-liquid reaction is completed, the solid part is dried and heat treated, and then it can be directly regenerated into a new positive electrode material. Its electrochemical performance is comparable to that of the same type of commercial positive electrode materials, and it can be used in the production of new lithium batteries. The value of the recycled product is greatly increased, and the liquid part can be reused after being collected, with basically no wastewater discharge in the entire process.

[0019] The present invention has developed a set of technical routes that are completely different from existing recycling methods through innovation in principle and unique reaction design. It has significant advantages over existing recycling methods in terms of both technological advancement and economy.

[0020] The dried solid is subjected to a stepwise heat treatment, wherein the temperature of the first stage is 200-500°C, the heat treatment time is 0.5-15h, and the heat treatment atmosphere is at least one of air, nitrogen, argon-hydrogen mixture, argon, oxygen, and carbon dioxide. The first stage low-temperature heat treatment is mainly to provide a suitable temperature range for the occurrence of the lithiation reaction to prevent the lithium-containing component from volatilizing too quickly; the second stage temperature is 600-1000°C, the heat treatment time is 0.5-15h, and the heat treatment atmosphere is at least one of air, nitrogen, argon-hydrogen mixture, argon, oxygen, and carbon dioxide; the second stage high-temperature heat treatment is after the lithiation reaction. The high temperature causes the atoms to diffuse inside the solid, realizing atomic rearrangement, thereby making the structure more regular and completely repaired. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic flow chart of the method for directly regenerating the positive electrode black powder of waste lithium-ion batteries in the present invention;

[0022] Figure 2 This is a microscopic morphology of the nickel-manganese-cobalt ternary positive electrode black powder in Example 1 of the present invention;

[0023] Figure 3 This is a microscopic morphology of the regenerated nickel-manganese-cobalt ternary positive electrode material in Example 1 of the present invention;

[0024] Figure 4 Comparison of the charge and discharge curves of the nickel-manganese-cobalt ternary positive electrode black powder, the recycled nickel-manganese-cobalt ternary positive electrode material, and the commercial nickel-manganese-cobalt ternary positive electrode material in Example 1 of the present invention;

[0025] Figure 5 This is a comparison chart of the cycle performance of the lithium-ion battery C1# and the lithium-ion battery C5# of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0027] Example 1

[0028] In this embodiment, waste nickel-manganese-cobalt ternary battery black powder is directly regenerated to obtain regenerated nickel-manganese-cobalt ternary positive electrode material. The process flow is as follows: Figure 1 As shown, the specific steps include:

[0029] S1. After disassembling, crushing, sorting and pre-treating the discarded nickel-manganese-cobalt ternary batteries, nickel-manganese-cobalt ternary positive electrode black powder is obtained; the black powder is pre-treated to preliminarily remove residual impurities.

[0030] S2. Analyze the composition of nickel-manganese-cobalt ternary positive electrode black powder, then take an appropriate amount of lithium acetate and isoamyl alcohol to react, stir for 4 hours at room temperature and pressure to obtain an organic lithium solution; then add the pretreated black powder to the organic lithium solution with a solid-liquid ratio of 1:1, and react for 12 hours at room temperature and pressure. Filter and separate the mixed solution after the reaction to obtain lithiated black powder, and dry it at 60°C in vacuum overnight.

[0031] S3. The dried lithiated black powder is subjected to a stepwise heat treatment at 200°C for 2 hours and 900°C for 5 hours in an air or oxygen atmosphere to obtain a regenerated nickel-manganese-cobalt ternary positive electrode material.

[0032] The microscopic morphology of the nickel-manganese-cobalt ternary positive electrode black powder and the obtained regenerated nickel-manganese-cobalt ternary positive electrode material in Example 1 was observed by scanning electron microscopy (SEM). Figure 2 and 3 As shown: From the microscopic morphology of the nickel-manganese-cobalt ternary positive electrode black powder, it can be seen that there are obvious fragmentation and microcracks on the surface of its grains. This is because the repeated insertion / extraction of lithium ions causes the layered structure of lithium cobalt oxide to be destroyed and collapsed, thus destroying its crystal structure. After being repaired, the microscopic morphology of the regenerated nickel-manganese-cobalt ternary positive electrode material becomes smooth again, the microcracks are repaired, and the lithium cobalt oxide structure becomes complete again.

[0033] Example 2

[0034] In this embodiment, waste lithium iron phosphate battery black powder is directly regenerated to obtain regenerated lithium iron phosphate positive electrode material. The process flow is as follows: Figure 1 As shown, the specific steps include:

[0035] S1. After disassembling, crushing, sorting and pre-treating the discarded lithium iron phosphate batteries, lithium iron phosphate positive electrode black powder is obtained; the black powder is pre-treated to preliminarily remove residual impurities.

[0036] S2. Analyze the composition of the lithium iron phosphate positive electrode black powder, then take an appropriate amount of lithium hydroxide and acetonitrile to react, stir at room temperature and pressure for 4 hours to obtain an organic lithium solution; then add the pretreated black powder to the organic lithium solution with a solid-liquid ratio of 1:50, and react at room temperature and pressure for 1 hour. The mixed solution after the reaction is filtered and separated to obtain lithiated black powder, which is then dried overnight at 120°C in vacuum.

[0037] S3. The dried lithiated black powder is subjected to a stepwise heat treatment at 500° C. for 0.5 h and 700° C. for 10 h in an atmosphere of nitrogen or an argon-hydrogen mixture to obtain a regenerated lithium iron phosphate positive electrode material.

[0038] Example 3

[0039] In this embodiment, waste lithium cobalt oxide battery black powder is directly regenerated to obtain regenerated lithium cobalt oxide positive electrode material. The process flow is as follows: Figure 1 As shown, the specific steps include:

[0040] S1. After disassembling, crushing, sorting and pre-treating the discarded lithium cobalt oxide batteries, lithium cobalt oxide positive electrode black powder is obtained; the black powder is pre-treated to preliminarily remove residual impurities.

[0041] S2. Analyze the composition of the lithium cobalt oxide positive electrode black powder, then take an appropriate amount of lithium chloride and N-methylpyrrolidone to react, stir at room temperature and pressure for 4 hours to obtain an organic lithium solution; then add the pretreated black powder to the organic lithium solution with a solid-liquid ratio of 1:10, and react at room temperature and pressure for 48 hours. The mixed solution after the reaction is filtered and separated to obtain lithiated black powder, which is then dried overnight at 80°C in vacuum.

[0042] S3. The dried lithiated black powder is subjected to a stepwise heat treatment at 500° C. for 2 h and 1000° C. for 2 h in an air atmosphere to obtain a regenerated lithium cobalt oxide positive electrode material.

[0043] Example 4

[0044] In this embodiment, waste lithium manganese oxide battery black powder is directly regenerated to obtain regenerated lithium manganese oxide positive electrode material. The process flow is as follows: Figure 1 As shown, the specific steps include:

[0045] S1. After disassembling, crushing, sorting and pre-treating the discarded lithium manganese oxide batteries, lithium manganese oxide positive electrode black powder is obtained; the black powder is pre-treated to preliminarily remove residual impurities.

[0046] S2. Analyze the composition of lithium manganate positive electrode black powder, then take an appropriate amount of lithium carbonate and n-pentanol to react, stir at room temperature and pressure for 4 hours to obtain an organic lithium solution; then add the pretreated black powder to the organic lithium solution with a solid-liquid ratio of 1:20, and react at room temperature and pressure for 24 hours. The mixed solution after the reaction is filtered and separated to obtain lithiated black powder, which is then dried overnight at 100°C in vacuum.

[0047] S3. The dried lithiated black powder is subjected to a stepwise heat treatment at 200° C. for 1 h and 800° C. for 15 h in an air atmosphere to obtain a regenerated lithium manganese oxide positive electrode material.

[0048] Application Examples

[0049] This application example uses the recycled positive electrode materials prepared in the above embodiments 1 to 4 and the commercial positive electrode materials purchased on the market to prepare lithium-ion batteries. The specific process includes the following steps:

[0050] S1. Preparation of positive electrode sheets, including: mixing positive electrode material, conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) in a mass ratio of 90:5:5 and dissolving in an organic solvent N-methylpyrrolidone (NMP) to prepare positive electrode slurry, and then coating the positive electrode slurry on a positive electrode current collector aluminum foil, and cutting to obtain positive electrode sheets after drying;

[0051] S2. Preparation of negative electrode sheets, including: preparing negative electrode slurry by mixing artificial graphite, conductive agent acetylene black, adhesive sodium carboxymethyl cellulose and carboxyl styrene butadiene latex in a mass ratio of 90:7:2:1, and then coating the negative electrode slurry on the negative electrode current collector copper foil, and cutting and drying to obtain negative electrode sheets;

[0052] S3, assembling a lithium-ion battery, comprising: winding and assembling the positive electrode sheet obtained in step S1, the negative electrode sheet obtained in step S2 and a PP separator, injecting an electrolyte (ethylene carbonate EC: ethyl methyl carbonate EMC: diethyl carbonate DEC = 1:1:1, 1 mol / L LiPF6) to obtain a lithium-ion battery; then charging the obtained battery cell to 4.3 V at 25°C and a current density of 0.1C, and then charging to 2.5 V at a current density of 0.1C for formation.

[0053] According to the above method, the regenerated nickel-manganese-cobalt ternary positive electrode, regenerated lithium iron phosphate positive electrode, regenerated lithium cobalt oxide positive electrode, and regenerated lithium manganese oxide positive electrode prepared in Examples 1 to 4 were respectively used as positive electrode materials to prepare lithium ion batteries C1# to C4# accordingly. At the same time, commercial nickel-manganese-cobalt ternary positive electrode, commercial lithium iron phosphate positive electrode, commercial lithium cobalt oxide positive electrode, and commercial lithium manganese oxide positive electrode were used as positive electrode materials to prepare lithium ion batteries C5# to C8# accordingly.

[0054] Test example

[0055] This test case tests the cycle performance of lithium-ion batteries C1#~C8#, including:

[0056] 1. The cycle performance of lithium-ion battery C1# (electrode material adopts the recycled nickel-manganese-cobalt ternary material of Example 1) and lithium-ion battery C5# (electrode material adopts commercial nickel-manganese-cobalt ternary material) were tested. Specifically, the cycle was carried out at a rate of 0.5C. The charge-discharge cycle curves are shown in FIG. Figure 4 As shown, the cycle performance is Figure 5 As shown. Figure 4 , 5It can be seen that the average discharge specific capacity of lithium-ion battery C1# at 0.5C rate reaches 160mAh / g, which is comparable to that of batteries using commercial electrode materials, and the cycle retention rate after 100 cycles reaches more than 94%, which is better than battery C5# using commercial nickel-manganese-cobalt ternary materials as the positive electrode.

[0057] 2. The cycle performance of lithium-ion battery C2# (the electrode material is the regenerated lithium iron phosphate material of Example 2) and lithium-ion battery C6# (the electrode material is the commercial lithium iron phosphate material) were tested. Specifically, the cycle was carried out at a rate of 0.5C. The average discharge specific capacity of lithium-ion battery C2# at a rate of 0.5C reached 150 mAh / g, which is equivalent to that of batteries using commercial electrode materials, and the cycle retention rate after 200 cycles reached more than 93%, which is better than battery C6# using commercial lithium iron phosphate material as the positive electrode.

[0058] 3. The cycle performance of lithium-ion battery C3# (the electrode material is the recycled lithium cobalt oxide material of Example 3) and lithium-ion battery C7# (the electrode material is the commercial lithium cobalt oxide material) were tested. Specifically, the cycle was carried out at a rate of 0.5C. The average discharge specific capacity of lithium-ion battery C3# at a rate of 0.5C reached 140 mAh / g, which is equivalent to that of batteries using commercial electrode materials, and the cycle retention rate after 100 cycles reached more than 95%, which is better than battery C7# using commercial lithium iron phosphate material as the positive electrode.

[0059] 4. The cycle performance of lithium-ion battery C4# (the electrode material is the regenerated lithium manganese oxide material of Example 4) and lithium-ion battery C8# (the electrode material is the commercial lithium manganese oxide material) were tested. Specifically, the cycle was carried out at a rate of 0.5C. The average discharge specific capacity of lithium-ion battery C4# at a rate of 0.5C reached 135 mAh / g, which is equivalent to that of batteries using commercial electrode materials, and the cycle retention rate after 100 cycles reached more than 92%, which is better than battery C8# using commercial lithium iron phosphate material as the positive electrode.

[0060] As can be seen from the above, the method for direct regeneration of waste lithium-ion battery positive electrode black powder proposed in the present invention is to prepare an organic lithium solution at room temperature and pressure, then lithiate the black powder at room temperature and pressure through solid-liquid reaction, and directly regenerate the positive electrode black powder into positive electrode material for reuse in combination with subsequent heat treatment. The obtained regenerated material has comparable performance to commercial positive electrode materials of the same type. This method no longer requires the use of strong acids and alkalis, has a simple process, less waste emissions, and a higher product value, providing a new technical route for the actual treatment of waste lithium-ion battery black powder, with extremely high economic and environmental benefits.

[0061] The above embodiments of the present invention are only examples for explaining the present invention, and are not intended to limit the specific implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above examples. It is impossible to give detailed examples of all implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A direct regeneration method for waste lithium-ion battery positive electrode black powder, comprising the following steps: S1. Dismantling, sorting and pre-treating waste lithium-ion batteries to obtain positive electrode material black powder; S2, stirring a lithium salt and an organic solvent at room temperature and pressure to react to produce an organic lithium solution; the organic lithium solution is any one of a solution obtained by reacting lithium acetate and isoamyl alcohol, a solution obtained by reacting lithium hydroxide and acetonitrile, a solution obtained by reacting lithium chloride and N-methylpyrrolidone, or a solution obtained by reacting lithium carbonate and n-amyl alcohol; the mass ratio of the total mass of the lithium salt to the organic solvent is 1:100 to 25:100; then placing the black powder in the organic lithium solution, stirring and reacting at room temperature and pressure to obtain lithiated black powder; S3, performing solid-liquid separation and drying on the lithiated black powder and the solution, and then performing heat treatment to obtain a regenerated positive electrode material; In step S3, the dried solid is subjected to step heat treatment, the temperature of the first stage is 200-500°C, the heat treatment time is 0.5-15h, and the heat treatment atmosphere is at least one of air, nitrogen, argon-hydrogen mixture, argon, oxygen, and carbon dioxide; the temperature of the second stage is 600-1000°C, the heat treatment time is 0.5-15h, and the heat treatment atmosphere is at least one of air, nitrogen, argon-hydrogen mixture, argon, oxygen, and carbon dioxide.

2. The direct regeneration method of waste lithium-ion battery positive electrode black powder according to claim 1, characterized in that: In step S1, the positive electrode material is at least one of lithium cobalt oxide, lithium iron phosphate, nickel manganese cobalt ternary material, and lithium manganese oxide.

3. The direct regeneration method of waste lithium ion battery positive electrode black powder according to claim 1, characterized in that: In step S2, the solid-liquid ratio of the reaction between the black powder and the organic lithium solution is not greater than 1:1, and the reaction time is not less than 1 hour.

4. The direct regeneration method of waste lithium-ion battery positive electrode black powder according to claim 1, characterized in that: In step S3, the lithiated black powder and the solution after the reaction are separated into solid and liquid by pressure filtration or suction filtration.

5. The direct regeneration method of waste lithium-ion battery positive electrode black powder according to claim 1, characterized in that: In step S3, the solid after solid-liquid separation is vacuum dried at a drying temperature of 60-120°C.

6. A pole piece, characterized in that: It comprises a current collector and an electrode material layer arranged on the surface of the current collector, wherein the material of the electrode material layer comprises the regenerated positive electrode material prepared according to any one of claims 1-5.

7. A lithium ion battery, characterized in that: Including the pole piece as described in claim 6.

Images