Method for recycling single crystal positive electrode material of retired lithium ion battery in green way

Abstract

This invention discloses a green method for recycling single-crystal cathode materials from retired lithium-ion batteries, comprising the following steps: pre-treating retired layered lithium-ion battery packs to obtain black powder; pyrolyzing the black powder to obtain powder, thoroughly washing and drying the powder with deionized water, and annealing the powder in air; thereby obtaining a single-crystal recycled cathode material with excellent electrochemical performance. This invention broadens the application fields suitable for recycled cathode materials, provides a method for large-scale production of high-performance recycled materials, and enables better quality control of recycled cathodes. It ensures the processing performance and electrochemical performance of the recycled material, meeting the requirements of power batteries for cathode materials. The preparation steps of this invention are simple, the recycled product has high purity, the raw material utilization rate is high, and wastewater discharge is eliminated.

Description

Technical Field

[0001] This invention relates to the field of recycling technology for cathode materials of retired lithium-ion batteries, and in particular to a green method for recycling single-crystal cathode materials from retired lithium-ion batteries. Background Technology

[0002] Currently, a large number of lithium-ion batteries will be retired after long-term use. Furthermore, the scarcity of lithium-ion battery cathode materials has led to rising battery prices. Therefore, recycling retired lithium-ion battery cathode materials is a promising prospect. Traditional recovery methods that extract valuable elements from cathode material waste liquid are difficult to separate and purify, and pollute the environment. Direct regeneration can effectively avoid these problems. The focus of direct regeneration methods is lithium replenishment, repairing the material composition and structural defects caused by lithium loss during the charging and discharging process of the cathode material, and maximizing the preservation of the high added value of the cathode material. For example, patent CN 110797602A repairs and regenerates cathode materials through direct lithium replenishment, but the raw materials used are only powder obtained from the post-failure treatment of cathode material electrodes, or scraps of cathode materials. The materials are relatively pure, and the experimental scale is small. Direct regeneration technology has developed in the recycling and utilization of retired cathode materials due to its advantages such as short process time, environmental friendliness, low energy consumption, and high added value.

[0003] However, since the morphology of decommissioned layered cathode materials is usually composed of secondary polycrystalline particles consisting of many primary nanoscale particles, their failure also includes other problems, such as particle fragmentation, surface structure damage, and poor particle structure stability. Single-crystal materials, lacking grain boundaries, can effectively mitigate the formation of microcracks caused by the anisotropic volume changes in polycrystalline materials, increasing electrode compaction density and mechanical strength, reducing volume expansion rate, exhibiting better structural stability, and thus contributing to increased battery volumetric energy density and improved battery safety. For example, patent CN 113265704A provides a method for using LiNi from spent lithium-ion batteries... 1-x-y Mn x Co y A method for regenerating O2 ternary electrode materials to prepare sheet-like single-crystal ternary electrode materials with uniform morphology and size and exposed {010} crystal planes. This significantly improves the cycle performance and stability of the electrode material. Patent CN 113328161B invented a method for regenerating near-single-crystal ternary cathode materials from waste lithium-ion battery cathode materials; the electrochemical performance of the regenerated cathode materials is difficult to match that of commercial materials. However, both methods use cathode sheets separated under laboratory conditions, resulting in small-scale production and low efficiency.

[0004] Therefore, a green method for recycling retired lithium-ion batteries to regenerate monocrystalline cathode materials is needed to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides a green method for recycling single-crystal cathode materials from retired lithium-ion batteries to solve the aforementioned problems in the prior art.

[0006] The solution of the present invention is:

[0007] A green method for recycling single-crystal cathode materials from retired lithium-ion batteries includes the following steps:

[0008] 1) After pretreatment, the retired layered lithium-ion battery packs are used to obtain black powder containing positive and negative electrode active materials and conductive agents. The content of Al and Cu metal elements in the black powder is determined by inductively coupled plasma atomic emission spectrometry. If the content of Al and Cu metal elements in the black powder is less than the specified value, the black powder is used as raw material.

[0009] 2) First, the black powder is subjected to lithium supplementation calcination. The obtained material is then calcined with lithium hydroxide at high temperature, causing the various substances in the black powder to decompose at different temperatures and accelerating crystal growth to obtain powder. The powder is thoroughly washed with deionized water and dried, and then annealed in air to obtain a single-crystal regenerated cathode material with excellent electrochemical performance.

[0010] As a preferred technical solution, the decommissioned layered lithium-ion battery pack uses LiNi 1-x-y Co x Al y O2, LiNi 1-x- y Co x Mn y One or more of the waste lithium-ion batteries containing O2 and LiCoO2 as cathode materials, wherein 0≤x≤0.1 and 0≤y≤0.1.

[0011] As a preferred technical solution, in step 1), the content of the black powder metal elements Al and Cu is less than a specified value, which is when the Al content is ≤0.015% and the Cu content is ≤0.005%.

[0012] As a preferred technical solution, in step 2), the black powder is calcined for lithium supplementation by mixing black powder and lithium salt at a mass ratio of 2:1 to 5 and calcining in air at 250 to 600°C for 2 to 6 hours.

[0013] As a preferred technical solution, the lithium salt used in step 2) for lithium replenishment is any one of the following: a mixed lithium salt of lithium chloride and lithium carbonate, a mixed lithium salt of lithium sulfate and lithium acetate, or a mixed lithium salt of lithium nitrate and lithium chloride. The two lithium salts are mixed in a ratio that forms the lowest eutectic point.

[0014] As a preferred technical solution, the material obtained in step 2) is calcined with lithium hydroxide at a high temperature by mixing the material and lithium hydroxide at a mass ratio of 1:0.4-1, the calcination temperature being 630-900℃, and the calcination time being 6-15h.

[0015] As a preferred technical solution, the mixing method is either ball milling or supercritical process; the ball milling is a planetary ball mill with a rotation speed of 500-1000 r / min and a time of 7-15 h; the supercritical process is to mix in a supercritical reactor and react the mixture under supercritical CO2 conditions for 2 h.

[0016] As a preferred technical solution, in step 2), the powder is thoroughly washed and dried with deionized water to perform 2-3 stages of countercurrent washing. The final stage wash water has a pH ≤ 8 and is completely dried in a forced-air drying oven at 100-150℃. In the countercurrent washing, the first stage wash water is used to recover Li with saturated sodium carbonate solution and is used as a solution for preparing the hydrothermal synthesis of cathode materials. The second and third stage wash water are used as the first and second stage wash solutions for the next batch of powder, respectively. The final stage wash water for the powder is all deionized water, so no wastewater discharge will occur.

[0017] As a preferred technical solution, in step 2), the powder is annealed in air at 350-650°C for 2-6 hours in an air atmosphere.

[0018] As a preferred technical solution, the method further includes testing the chemical properties of the monocrystalline recycled cathode material in step 3), wherein the chemical properties are tested by preparing a coin cell from the obtained monocrystalline recycled cathode material and testing it at a constant temperature of 30°C.

[0019] A green method for recycling retired lithium-ion batteries and regenerating single-crystal cathode materials using the above-mentioned technical solution includes the following steps: 1) After pretreatment of retired layered lithium-ion battery packs, black powder containing positive and negative electrode active materials and conductive agents is obtained. The content of Al and Cu metal elements in the black powder is determined by inductively coupled plasma atomic emission spectrometry. If the content of Al and Cu metal elements in the black powder is less than the specified value, the black powder is used as raw material; 2) The black powder is first subjected to lithium supplementation calcination. The obtained material is calcined with lithium hydroxide at high temperature, so that the substances in the black powder decompose at different temperatures and accelerate crystal growth to obtain powder; the powder is thoroughly washed with deionized water and dried, and then annealed in air to obtain single-crystal regenerated cathode material with excellent electrochemical performance.

[0020] Advantages of this invention:

[0021] This invention broadens the application fields suitable for recycled cathode materials and provides a method for large-scale production of high-performance recycled materials, enabling better quality control of recycled cathodes. It ensures the processing and electrochemical performance of the recycled materials, meeting the requirements of power batteries for cathode materials. The preparation steps of this invention are simple, the recycled product has high purity, and the raw material utilization rate is high, achieving zero wastewater discharge. Attached Figure Description

[0022] Figure 1 SEM image of recycled lithium cobalt oxide material from Example 1;

[0023] Figure 2 Cyclic performance curves for recycled single-crystal material (S-LCO) and commercially available lithium cobalt oxide single-crystal material (P-LCO) from Example 1 are shown.

[0024] Figure 3 The rate performance diagrams for the recycled single-crystal material (S-NCM) and the commercially available lithium nickel cobalt manganese oxide single-crystal cathode material in Example 2 are shown.

[0025] Figure 4 The images show the XRD patterns of the recycled single-crystal material (S-LCO) and the commercially available lithium cobalt oxide single-crystal cathode material (P-LCO) from Example 3. Detailed Implementation

[0026] To overcome the above deficiencies, this invention provides a green method for recycling retired lithium-ion batteries to regenerate single-crystal cathode materials, thereby solving the problems mentioned in the background art.

[0027] A green method for recycling single-crystal cathode materials from retired lithium-ion batteries includes the following steps:

[0028] 1) After pretreatment, the retired layered lithium-ion battery packs are used to obtain black powder containing positive and negative electrode active materials and conductive agents. The content of Al and Cu metal elements in the black powder is determined by inductively coupled plasma atomic emission spectrometry. If the content of Al and Cu metal elements in the black powder is less than the specified value, the black powder is used as raw material.

[0029] 2) First, the black powder is subjected to lithium supplementation calcination. The obtained material is then calcined with lithium hydroxide at high temperature, causing the various substances in the black powder to decompose at different temperatures and accelerating crystal growth to obtain powder. The powder is thoroughly washed with deionized water and dried, and then annealed in air to obtain a single-crystal regenerated cathode material with excellent electrochemical performance.

[0030] The retired layered lithium-ion battery pack uses one or more of the following waste lithium-ion batteries with LiNi1-x-yCoxAlyO2, LiNi1-x-yCoxMnyO2, and LiCoO2 as cathode materials, wherein 0≤x≤0.1 and 0≤y≤0.1.

[0031] In step 1), the content of the metal elements Al and Cu in the black powder is less than the specified values, which are Al content ≤ 0.015% and Cu content ≤ 0.005%.

[0032] In step 2), the black powder is calcined to supplement lithium by mixing black powder and lithium salt at a mass ratio of 2:1 to 5 and calcining in air at 250 to 600°C for 2 to 6 hours.

[0033] The lithium salt used in step 2) for lithium replenishment is any one of the following: a mixed lithium salt of lithium chloride and lithium carbonate, a mixed lithium salt of lithium sulfate and lithium acetate, or a mixed lithium salt of lithium nitrate and lithium chloride. The two lithium salts are mixed in proportion to form the lowest eutectic point.

[0034] The material obtained in step 2) is calcined with lithium hydroxide at a high temperature by mixing the material and lithium hydroxide at a mass ratio of 1:0.4-1, with a calcination temperature of 630-900℃ and a calcination time of 6-15h.

[0035] The mixing method is either ball milling or supercritical process; the ball milling is a planetary ball mill with a rotation speed of 500-1000 r / min and a time of 7-15 h; the supercritical process is to mix in a supercritical reactor and react the mixture under supercritical CO2 conditions for 2 h.

[0036] In step 2), the powder is thoroughly washed with deionized water and dried. This process involves 2-3 stages of countercurrent washing. The final stage wash water has a pH ≤ 8 and is completely dried in a forced-air drying oven at 100-150°C. In the countercurrent washing, the first stage wash water is used to recover Li using a saturated sodium carbonate solution, which is then used as a solution for preparing the hydrothermal synthesis of the cathode material. The second and third stage wash waters are used sequentially as the first and second stage wash solutions for the next batch of powder. The final stage wash water used for the powder is deionized water, and no wastewater discharge is generated.

[0037] In step 2), the powder is annealed in air at 350–650°C for 2–6 hours in an air atmosphere.

[0038] It also includes testing the chemical properties of the single-crystal recycled cathode material described in step 3). The chemical properties test involves preparing a coin cell from the obtained single-crystal recycled cathode material and testing it at a constant temperature of 30°C.

[0039] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0040] Example 1:

[0041] After fully automated charged crushing, sorting, and pretreatment, retired lithium cobalt oxide batteries yielded black powder containing a large amount of positive and negative electrode active materials and a small amount of conductive agent. The Al and Cu metal element content in the black powder was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The Al content was 0.01%, and the Cu content was 0.005%. The black powder was mixed with a mixture of lithium sulfate and lithium acetate at a mass ratio of 2:1 and calcined in air at 450°C for 4 hours to obtain a lithium replenishing material.

[0042] The lithium-added material was ball-milled with lithium hydroxide at a mass ratio of 1:0.4 for 8 hours at 500 rpm and calcined at 650℃ for 12 hours. The material was then subjected to countercurrent washing until the pH of the final wash water was ≤8, and then completely dried in a forced-air drying oven at 100℃. The dried powder was annealed in air at 350℃ for 2 hours to obtain the regenerated lithium cobalt oxide cathode material. The obtained regenerated cathode material was used to fabricate coin cells, which were then tested at a constant temperature of 30℃.

[0043] Figure 1 This is a SEM image of the recycled lithium cobalt oxide cathode material obtained through this embodiment. As can be seen from the image, the recycled lithium cobalt oxide cathode material particles are smooth and of moderate size, and no agglomeration occurs.

[0044] Figure 2 The figures show the cycle performance curves of the recycled single-crystal material (S-LCO) and the commercially available lithium nickel cobalt manganese oxide single-crystal material (P-LCO) in this embodiment. As can be seen from the figures, the capacity retention rates of the recycled lithium cobalt oxide cathode material obtained in this embodiment are not much different from those of the commercial lithium cobalt oxide material, indicating that the prepared recycled material fully meets the requirements for use.

[0045] Example 2:

[0046] Retired nickel-cobalt-manganese lithium oxide batteries, after pretreatment including fully automated charged crushing and sorting, yielded black powder containing a large amount of positive and negative electrode active materials and a small amount of conductive agent. The Al and Cu metal element content in the black powder was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The Al content was 0.005%, and the Cu content was 0.002%. The black powder was mixed with lithium nitrate and lithium chloride at a mass ratio of 2:2 and calcined in air at 250°C for 6 hours to obtain a lithium replenishing material.

[0047] In a supercritical reactor, the lithium-replenished material was reacted with lithium hydroxide at a mass ratio of 1:1 under supercritical CO2 conditions for 2 hours. Calcination was then carried out at 900℃ for 6 hours. The material was then countercurrently washed, and when the pH of the final wash water was ≤8, it was completely dried in a forced-air drying oven at 120℃. The dried powder was annealed in air at 550℃ for 4 hours to obtain regenerated lithium nickel cobalt manganese oxide cathode material. The obtained regenerated cathode material was used to fabricate coin cells, which were then tested at a constant temperature of 30℃.

[0048] Figure 3 The figures show the rate performance curves of the recycled single-crystal material (S-NCM) and the commercially available lithium nickel cobalt manganese oxide single-crystal material (P-NCM) in this embodiment. As can be seen from the figures, the recycled lithium nickel cobalt manganese oxide cathode material (S-NCM) obtained through this embodiment has excellent rate performance and can meet the charging and discharging performance requirements at high rates.

[0049] Example 3:

[0050] Retired lithium cobalt oxide batteries, after pretreatment including fully automated charged crushing and sorting, yielded black powder containing a large amount of positive and negative electrode active materials and a small amount of conductive agent. The Al and Cu metal element content in the black powder was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The Al content was 0.01%, and the Cu content was 0.005%. The black powder was mixed with lithium chloride and lithium carbonate at a mass ratio of 2:5 and calcined in air at 550°C for 2 hours to obtain a lithium replenishing material.

[0051] In a supercritical reactor, the lithium-added material was reacted with lithium hydroxide at a mass ratio of 1:0.5 under supercritical CO2 conditions for 2 hours. Calcination was then carried out at 710℃ for 4 hours. The material was then countercurrently washed, and when the pH of the final wash water was ≤8, it was completely dried in a forced-air drying oven at 110℃. The dried powder was annealed in air at 450℃ for 2 hours to obtain regenerated lithium cobalt oxide cathode material. The obtained regenerated cathode material was used to fabricate coin cells, which were then tested at a constant temperature of 30℃.

[0052] Figure 4 The figures show the XRD patterns of the recycled single-crystal material (S-LCO) and the commercially available lithium cobalt oxide single-crystal material (P-LCO) in this embodiment. As can be seen from the figures, the crystal structure of the recycled lithium cobalt oxide single-crystal cathode material obtained in this embodiment is consistent with that of the commercial lithium cobalt oxide material, indicating that the purity of the prepared recycled material fully meets the requirements for use.

[0053] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for green recycling of single-crystal cathode materials from retired lithium-ion batteries, characterized in that, Includes the following steps: 1) After pretreatment, the retired layered lithium-ion battery packs are used to obtain black powder containing positive and negative electrode active materials and conductive agents. The content of Al and Cu metal elements in the black powder is determined by inductively coupled plasma atomic emission spectrometry. The content of Al and Cu metal elements in the black powder is less than the specified values, which are Al content ≤ 0.015% and Cu content ≤ 0.005%. The black powder is used as raw material. 2) First, the black powder is subjected to lithium supplementation calcination. The obtained material is then calcined with lithium hydroxide at high temperature, causing the various substances in the black powder to decompose at different temperatures and accelerating crystal growth to obtain powder. The black powder is calcined with lithium by mixing black powder and lithium salt at a mass ratio of 2:1 to 5 and calcining in air at 250 to 600°C for 2 to 6 hours. The obtained material was calcined with lithium hydroxide at a high temperature. The material and lithium hydroxide were mixed at a mass ratio of 1:0.4-1, the calcination temperature was 630-900℃, and the calcination time was 6-15h. The powder is thoroughly washed and dried with deionized water, and then annealed in air to obtain a single-crystal regenerated cathode material with excellent electrochemical performance.

2. The method for green recycling of single-crystal cathode materials from retired lithium-ion batteries as described in claim 1, characterized in that: The retired layered lithium-ion battery pack uses LiNi 1-x-y Co x Al y O2, LiNi 1-x-y Co x Mn y One or more of the waste lithium-ion batteries containing O2 and LiCoO2 as cathode materials, wherein 0≤x≤0.1 and 0≤y≤0.

1.

3. The method for green recycling of single-crystal cathode materials from retired lithium-ion batteries as described in claim 1, characterized in that: The lithium salt used in step 2) for lithium replenishment is any one of the following: a mixed lithium salt of lithium chloride and lithium carbonate, a mixed lithium salt of lithium sulfate and lithium acetate, or a mixed lithium salt of lithium nitrate and lithium chloride. The two lithium salts are mixed in proportion to form the lowest eutectic point.

4. The method for green recycling of single-crystal cathode materials from retired lithium-ion batteries as described in claim 1, characterized in that: The material after lithium supplementation is mixed with lithium hydroxide by one of ball milling or supercritical process; the ball milling is a planetary ball mill with a speed of 500-1000 r / min and a time of 7-15 h; the supercritical process is to mix in a supercritical reactor and react the mixture under supercritical CO2 conditions for 2 h.

5. The method for green recycling of single-crystal cathode materials from retired lithium-ion batteries as described in claim 1, characterized in that: In step 2), the powder is thoroughly washed with deionized water and dried. The powder undergoes 2-3 stages of countercurrent washing, with the final stage wash water having a pH ≤ 8. The powder is then completely dried in a forced-air drying oven at 100-150℃. In the countercurrent washing, the first stage wash water is used to recover Li using a saturated sodium carbonate solution, which is then used as a solution for preparing the hydrothermal synthesis of the cathode material. The second and third stage wash waters are used sequentially as the first and second stage wash solutions for the next batch of powder. The final stage wash water used for the powder is always deionized water, so no wastewater discharge is generated.

6. The method for green recycling of single-crystal cathode materials from retired lithium-ion batteries as described in claim 1, characterized in that: In step 2), the powder is annealed in air at 350–650°C for 2–6 hours in an air atmosphere.

7. The method for green recycling of single-crystal cathode materials from retired lithium-ion batteries as described in claim 1, characterized in that: It also includes testing the chemical properties of the single-crystal recycled cathode material described in step 3). The chemical properties test involves preparing a coin cell from the obtained single-crystal recycled cathode material and testing it at a constant temperature of 30°C.

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