Method for recycling lithium from waste lithium battery

Abstract

The invention provides a method for recycling lithium from a waste lithium battery, which comprises the following steps: pretreating the waste lithium battery to obtain a waste lithium battery black material; the method comprises the following steps: mixing the waste lithium battery black material with a leaching agent, and carrying out lithium leaching to obtain a lithium-containing leaching solution; mixing the lithium-containing leachate with a lithium ion adsorbent, and carrying out adsorption reaction to obtain a lithium-loaded adsorbent precipitate; and carrying out desorption treatment on the lithium-loaded adsorbent precipitate, and releasing lithium ions to obtain a lithium-rich solution. Carrying out post-treatment on the lithium-rich solution to obtain a lithium product; the lithium ion adsorbent is a photosensitive azo group modified metal organic coordination compound. According to the method, the photosensitive azo group modified metal organic coordination compound is adopted as an adsorbent, the lithium ions can be selectively captured, the use of a toxic organic solvent is avoided, and the lithium ions can be controllably released only through ultraviolet irradiation in the desorption process due to the photoresponse characteristic of the metal organic coordination compound, so that the process simplification, greenness and low carbon are realized while the lithium is efficiently recovered.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium battery recycling technology, specifically relating to a method for recovering lithium from waste lithium batteries. Background Technology

[0002] With the rapid development of electric vehicles and portable electronic devices, the number of spent lithium batteries is growing exponentially. As lithium is a scarce strategic resource, its efficient recycling and utilization has become a critical issue that the industry urgently needs to address. Therefore, developing efficient and green spent lithium battery recycling technologies is crucial for ensuring strategic resource security and promoting a circular economy.

[0003] Currently, the mainstream recycling technologies mainly include pyrometallurgy and hydrometallurgy. Pyrometallurgical processes are energy-intensive, and lithium is easily lost in high-temperature slag, resulting in low recovery rates and poor selectivity. Although hydrometallurgy (acid leaching-extraction / precipitation) is widely used, it still faces significant challenges in lithium recovery: (1) Due to the coexistence of various metal ions (such as cobalt, nickel, manganese, and aluminum) in the leachate, their physicochemical properties are similar, making it difficult for traditional precipitation or solvent extraction methods to achieve high-selectivity separation of lithium, resulting in low purity of lithium products or lengthy recycling processes; (2) Solvent extraction technology heavily relies on volatile organic solvents such as tributyl phosphate and P507, as well as a large amount of acid and alkali reagents for extraction and back-extraction. These organic solvents are not only flammable and toxic, posing safety and environmental risks, but their loss and residue during the process also increase the difficulty and cost of subsequent wastewater treatment. The overall greening and cleanliness of the process need to be improved.

[0004] Therefore, developing a new green recycling process that can efficiently and selectively recover lithium while minimizing the use of harmful organic solvents is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering lithium from spent lithium batteries. This invention utilizes a metal-organic coordination compound modified with a photosensitive azo group as a lithium-ion adsorbent, achieving a green and efficient lithium-ion separation and extraction process. This adsorbent can selectively recognize and capture lithium ions in an all-aqueous system through its specific coordination structure, thus completely avoiding the environmental and safety problems caused by the use of volatile and toxic organic solvents in traditional processes, exhibiting significant environmental friendliness. Simultaneously, the photosensitive azo group introduced into the adsorbent gives it unique photoresponsive characteristics, allowing for the controlled release of lithium ions triggered only by ultraviolet light irradiation, achieving clean and low-energy operation of the desorption process, further reducing secondary pollution and reagent consumption. Therefore, this recovery process ensures efficient recovery of lithium resources while simplifying the separation process, meeting the industrial needs of green recycling.

[0006] To achieve this objective, the present invention adopts the following technical solution: This invention provides a method for recovering lithium from spent lithium batteries, the method comprising the following steps: Waste lithium batteries are pretreated to obtain waste lithium battery black material.

[0007] The waste lithium battery black material and leaching agent are mixed and lithium is leached to obtain a lithium-containing leachate.

[0008] The lithium-containing leachate and lithium-ion adsorbent are mixed and subjected to an adsorption reaction to obtain a lithium-loaded adsorbent precipitate.

[0009] The lithium-loaded adsorbent precipitate is desorbed to release lithium ions, resulting in a lithium-rich solution.

[0010] The lithium-rich solution is then post-processed to obtain the lithium product.

[0011] The lithium-ion adsorbent is a metal-organic coordination compound modified with a photosensitive azo group.

[0012] This invention achieves a green and efficient lithium-ion separation and extraction process by using a metal-organic coordination compound modified with a photosensitive azo group as a lithium-ion adsorbent. This adsorbent can selectively recognize and capture lithium ions in an all-aqueous system through its specific coordination structure, thus completely avoiding the environmental and safety problems caused by the use of volatile and toxic organic solvents in traditional processes, demonstrating significant environmental friendliness. Simultaneously, the photosensitive azo group introduced into the adsorbent gives it unique photoresponsive characteristics, allowing for the controlled release of lithium ions triggered by ultraviolet light irradiation. This enables clean and low-energy operation of the desorption process, further reducing secondary pollution and reagent consumption. Therefore, this recovery process simplifies the separation process while ensuring efficient recovery of lithium resources, meeting the industrial demand for green recycling.

[0013] Preferably, the preprocessing step includes: (a) The waste lithium battery is preheated and then subjected to cryogenic treatment to obtain the embrittled waste lithium battery body.

[0014] (b) The embrittled waste lithium battery body is crushed to obtain the waste lithium battery black material.

[0015] In this invention, deep cryogenic treatment following preheating can decompose some organic materials (such as battery separators, conductive agents, etc.) while increasing the brittleness of waste and improving the crushing effect.

[0016] Preferably, the preheating temperature is 100~200℃, for example, 100℃, 150℃ or 200℃, and the time is 2~5h, for example, 2h, 3h, 4h or 5h.

[0017] Preferably, the temperature of the cryogenic treatment is -50 to -100°C, for example, -50°C, -75°C, or -100°C, and the time is 1 to 3 hours, for example, 1 hour, 2 hours, or 3 hours.

[0018] Preferably, the crushing is carried out under ultraviolet light irradiation and / or microwave-assisted conditions.

[0019] This invention uses ultraviolet irradiation combined with microwave assistance, which helps to improve the decomposition and crushing of organic matter in the embrittled body of waste lithium batteries.

[0020] Preferably, an inert gas is also introduced during the crushing process. For example, the inert gas may be nitrogen.

[0021] In this invention, an inert gas is introduced during the crushing process. On the one hand, this provides an inert atmosphere to prevent the battery materials from oxidizing or burning when in contact with air, ensuring safety. On the other hand, the contact between the embrittled waste lithium battery body and the room temperature gas generates intense heat exchange and airflow disturbance, forming a fluidization effect similar to "boiling". This enhances the collision and shearing between materials, which helps to improve the decomposition and crushing effect of organic matter in the embrittled waste lithium battery body and increase the crushing rate.

[0022] Preferably, the leaching agent comprises any one or a combination of at least two of oxalic acid, amino acids, persulfates, or fluorides.

[0023] Preferably, the amino acid includes glycine and / or glutamic acid.

[0024] Preferably, the persulfate includes any one or a combination of at least two of ammonium persulfate, potassium persulfate, or sodium persulfate.

[0025] Preferably, the fluoride includes any one or a combination of at least two of ammonium fluoride, potassium fluoride, or sodium fluoride.

[0026] Preferably, during the lithium leaching process, the pH of the solution system is 1.5 to 2.5, for example, it can be 1.5, 2 or 2.5.

[0027] Preferably, the lithium-ion adsorbent comprises Li5L2, wherein L is a pentadentate pyrrole ligand containing a photosensitive azo group. It should be noted that the present invention does not limit the preparation method of Li5L2. For example, the method can be as follows: reacting an aniline derivative with a nitrite under acidic conditions to generate a diazonium salt, and then coupling it with another aromatic compound (such as a phenol or another aniline derivative) to generate an azobenzene intermediate with specific functional groups (such as -COOH, -OH, etc.). Then, through organic reactions such as esterification and amidation, the above azobenzene unit is linked to a molecule containing a pyrrole ring and a carboxylic acid group to obtain the target ligand H2L. Select a lithium salt, such as lithium hexafluorophosphate, lithium perchlorate or lithium nitrate, and dissolve the ligand H2L in a certain molar ratio (e.g., much higher than 5:2 to ensure complete reaction) in a mixed solvent such as a mixture of N,N-dimethylformamide, acetonitrile, methanol or water, and react at a constant temperature of 80-120℃ for 24-72h. After the reaction is completed, filter, wash and dry.

[0028] Preferably, the photosensitive azo group is selected from any one or a combination of at least two of the azobipyridine group, azophenyl group, or azopyrrole group.

[0029] In this invention, the selected photosensitive azo group endows Li5L2 with unique photoresponse characteristics. Under irradiation with ultraviolet light of a specific wavelength, the azo group undergoes reversible cis-trans isomerization, which can precisely control the material's binding capacity and release kinetics for lithium ions, thereby realizing the photo-controlled switching of the adsorption-desorption process. This characteristic not only significantly improves the selectivity and efficiency of lithium recovery, but also enables the desorption step to be completed under mild, low-energy light conditions, avoiding the adsorbent structure damage caused by traditional acid desorption and ensuring the cycling stability of the material.

[0030] Preferably, the organometallic coordination compound is further modified with hydrophilic groups.

[0031] In this invention, the introduction of hydrophilic groups makes the lithium-ion adsorbent water-soluble, giving it good dispersibility and contact efficiency in water, thereby significantly improving the adsorption reaction kinetics. This characteristic not only avoids the operational difficulties of traditional adsorbents in solid-liquid separation, but also achieves highly selective enrichment and recovery of lithium ions in the leachate.

[0032] It should be noted that the present invention does not limit the method of modifying the hydrophilic group. For example, the following method can be used: Li5L2 is dispersed in N,N-dimethylformamide, an excess of silane coupling agent containing the target hydrophilic group (such as (3-glycidyl etheroxypropyl)) is added, and the mixture is stirred at 60-80°C for 12-24 hours. After the reaction is completed, the mixture is centrifuged, washed, and dried.

[0033] Preferably, the hydrophilic group includes any one or a combination of at least two of hydroxyl, polyethylene glycol, or sodium sulfonate groups.

[0034] Preferably, the molar ratio of lithium ions to lithium ion adsorbent in the lithium-containing leachate is 1:(1.5~3), for example, it can be 1:1.5, 1:2, 1:2.5 or 1:3, etc.

[0035] In this invention, a suitable molar ratio ensures that the adsorbent has sufficient adsorption sites for lithium ions, achieving efficient adsorption, while avoiding waste caused by excessive adsorbent and subsequent separation difficulties.

[0036] Preferably, the temperature of the adsorption reaction is 25~40℃, for example, it can be 25℃, 30℃, 35℃ or 40℃.

[0037] Preferably, the adsorption reaction time is 1 to 3 hours, for example, 1 hour, 2 hours or 3 hours.

[0038] Preferably, during the mixing process of the lithium-containing leachate and the lithium-ion adsorbent, a crown ether extractant is also added.

[0039] In this invention, the introduction of crown ether extractants can effectively synergize with lithium ion adsorbents to selectively complex lithium ions, thereby significantly improving lithium recovery rate and product purity.

[0040] Preferably, the crown ether extractant includes any one or a combination of at least two of 12-crown-4, 15-crown-5, or benzo-15-crown-5.

[0041] Preferably, the molar ratio of the crown ether extractant to the lithium ions in the lithium-containing leachate is (0.2-2):1, for example, it can be 0.2:1, 0.5:1, 1:1, 1.5:1 or 2:1, etc.

[0042] Preferably, the desorption treatment method includes: The lithium-loaded adsorbent precipitate was dispersed in an aqueous medium and then irradiated with ultraviolet light.

[0043] Preferably, the method includes the following steps: (1) Provide used lithium batteries; The waste lithium battery is preheated at 100~200℃ for 2~5 hours (e.g., 2 hours, 3 hours, 4 hours or 5 hours), and then immediately transferred to -50~-100℃ for 1~3 hours (e.g., 1 hour, 2 hours or 3 hours) for cryogenic treatment to obtain the embrittled waste lithium battery body.

[0044] The brittle body of the waste lithium battery is placed into a crusher for crushing to obtain waste lithium battery black material with a particle size D50 of 0.1~0.5mm (for example, it can be 0.1mm, 0.2mm, 0.3mm, 0.4mm or 0.5mm, etc.).

[0045] The crushing process utilizes ultraviolet irradiation and microwave assistance; an inert gas is also introduced during the crushing process.

[0046] (2) Place the waste lithium battery black material in a leaching agent, adjust the pH of the solution system to 1.5~2.5, and control the temperature to 60~90℃ (for example, it can be 60℃, 70℃, 80℃ or 90℃, etc.) so that the lithium in the waste lithium battery black material is leached out to obtain a lithium-containing leachate.

[0047] The leaching agent includes any one or a combination of at least two of oxalic acid, amino acids, persulfates, or fluorides.

[0048] (3) Add lithium ion adsorbent to the lithium-containing leachate and mix. Control the temperature to 25~40℃ and carry out lithium adsorption reaction for 1~3h to obtain lithium-loaded adsorbent precipitate.

[0049] The lithium-ion adsorbent comprises a metal-organic coordination compound modified with a photosensitive azo group and a hydrophilic group. The photosensitive azo group is selected from any one or a combination of at least two of azobipyridine group, azophenyl group, or azopyrrole group. The hydrophilic group comprises any one or a combination of at least two of hydroxyl group, polyethylene glycol group, or sodium sulfonate group. The molar ratio of lithium ions to lithium-ion adsorbent in the lithium-containing leachate is 1:(1.5~3).

[0050] (4) Dissolve the lithium-loaded adsorbent precipitate in water to form a dispersion.

[0051] The dispersion is irradiated with ultraviolet light of wavelength 300~400nm (e.g., 300nm, 350nm or 400nm) for 2~6h (e.g., 2h, 3h, 4h, 5h or 6h) to release lithium ions from the lithium ion adsorbent, thereby obtaining a lithium-rich solution.

[0052] (5) Add a precipitant (such as sodium carbonate) or introduce carbon dioxide gas into the lithium-rich solution to generate lithium carbonate precipitate. After solid-liquid separation, washing and drying, battery-grade lithium carbonate product is obtained.

[0053] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0054] Compared with the prior art, the present invention has the following beneficial effects: This invention achieves a green and efficient lithium-ion separation and extraction process by using a metal-organic coordination compound modified with a photosensitive azo group as a lithium-ion adsorbent. This adsorbent can selectively recognize and capture lithium ions in an all-aqueous system through its specific coordination structure, thus completely avoiding the environmental and safety problems caused by the use of volatile and toxic organic solvents in traditional processes, demonstrating significant environmental friendliness. Simultaneously, the photosensitive azo group introduced into the adsorbent gives it unique photoresponsive characteristics, allowing for the controlled release of lithium ions triggered by ultraviolet light irradiation. This enables clean and low-energy operation of the desorption process, further reducing secondary pollution and reagent consumption. Therefore, this recovery process simplifies the separation process while ensuring efficient recovery of lithium resources, meeting the industrial demand for green recycling. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] Example 1 This embodiment provides a method for recovering lithium from spent lithium batteries, the method comprising the following steps: (1) Provide discharged waste lithium batteries; The waste lithium battery was preheated at 150°C for 3 hours, and then immediately transferred to -75°C for 2 hours of cryogenic treatment to obtain a brittle waste lithium battery body.

[0057] The brittle body of the waste lithium battery is placed in a crusher for crushing to obtain waste lithium battery black material with a particle size D50 of 0.3 mm.

[0058] The crushing process utilizes ultraviolet irradiation (wavelength 365nm, power 750W) and microwave assistance (power 650W, temperature 65℃); nitrogen gas is also introduced during the crushing process.

[0059] (2) The waste lithium battery black material is placed in a leaching agent, the pH of the solution system is adjusted to 2, and the temperature is controlled at 75°C, so that the lithium in the waste lithium battery black material is leached out to obtain a lithium-containing leachate.

[0060] The leaching agent is composed of oxalic acid (0.5 mol / L), histidine (0.05 mol / L), potassium fluoride (0.02 mol / L), potassium persulfate (0.05 mol / L), and water.

[0061] (3) Add lithium ion adsorbent to the lithium-containing leachate and mix. Control the temperature at 30°C and carry out the lithium adsorption reaction for 2 hours to obtain lithium-loaded adsorbent precipitate.

[0062] The lithium-ion adsorbent comprises Li5L2 modified with a hydrophilic group, wherein L is a pentadentate pyrrole ligand containing a photosensitive azo group, the photosensitive azo group is an azo bipyridine group, and the hydrophilic group is a polyethylene glycol group; the molar ratio of lithium ions to lithium-ion adsorbent in the lithium-containing leachate is 1:2.

[0063] (4) Dissolve the lithium-loaded adsorbent precipitate in water to form a dispersion.

[0064] The dispersion was irradiated with ultraviolet light at a wavelength of 365 nm for 4 hours to release lithium ions from the lithium ion adsorbent, resulting in a lithium-rich solution.

[0065] (5) Carbon dioxide gas is introduced into the lithium-rich solution to generate lithium carbonate precipitate. After solid-liquid separation, washing and drying, battery-grade lithium carbonate product is obtained.

[0066] Example 2 This embodiment provides a method for recovering lithium from spent lithium batteries, the method comprising the following steps: (1) Provide discharged waste lithium batteries; The waste lithium battery was preheated at 100°C for 5 hours, and then immediately transferred to -50°C for 3 hours of cryogenic treatment to obtain a brittle waste lithium battery body.

[0067] The brittle body of the waste lithium battery is placed into a crusher for crushing to obtain waste lithium battery black material with a particle size D50 of 0.5 mm.

[0068] The crushing process utilizes ultraviolet irradiation (wavelength 365nm, power 750W) and microwave assistance (power 650W, temperature 65℃); nitrogen gas is also introduced during the crushing process.

[0069] (2) The waste lithium battery black material is placed in a leaching agent, the pH of the solution system is adjusted to 1.5, and the temperature is controlled at 60°C, so that the lithium in the waste lithium battery black material is leached out to obtain a lithium-containing leachate.

[0070] The leaching agent is composed of oxalic acid (0.5 mol / L), histidine (0.05 mol / L), potassium fluoride (0.02 mol / L), potassium persulfate (0.05 mol / L), and water.

[0071] (3) Add lithium ion adsorbent to the lithium-containing leachate and mix. Control the temperature at 25°C and carry out the lithium adsorption reaction for 3 hours to obtain lithium-loaded adsorbent precipitate.

[0072] The lithium-ion adsorbent comprises Li5L2 modified with a hydrophilic group, wherein L is a pentadentate pyrrole ligand containing a photosensitive azo group, the photosensitive azo group is an azophenyl group, and the hydrophilic group is a sodium sulfonate group; the molar ratio of lithium ions to lithium-ion adsorbent in the lithium-containing leachate is 1:1.5.

[0073] (4) Dissolve the lithium-loaded adsorbent precipitate in water to form a dispersion.

[0074] The dispersion was irradiated with ultraviolet light at a wavelength of 365 nm for 6 hours to release lithium ions from the lithium ion adsorbent, resulting in a lithium-rich solution.

[0075] (5) Carbon dioxide gas is introduced into the lithium-rich solution to generate lithium carbonate precipitate. After solid-liquid separation, washing and drying, battery-grade lithium carbonate product is obtained.

[0076] Example 3 This embodiment provides a method for recovering lithium from spent lithium batteries, the method comprising the following steps: (1) Provide discharged waste lithium batteries; The waste lithium battery was preheated at 200°C for 2 hours, and then immediately transferred to -100°C for 1 hour of cryogenic treatment to obtain a brittle waste lithium battery body.

[0077] The brittle body of the waste lithium battery is placed in a crusher for crushing to obtain waste lithium battery black material with a particle size D50 of 0.1 mm.

[0078] The crushing process utilizes ultraviolet irradiation (wavelength 365nm, power 750W) and microwave assistance (power 650W, temperature 65℃); nitrogen gas is also introduced during the crushing process.

[0079] (2) The waste lithium battery black material is placed in a leaching agent, the pH of the solution system is adjusted to 2.5, and the temperature is controlled at 90°C, so that the lithium in the waste lithium battery black material is leached out to obtain a lithium-containing leachate.

[0080] The leaching agent is composed of oxalic acid (0.5 mol / L), histidine (0.05 mol / L), potassium fluoride (0.02 mol / L), potassium persulfate (0.05 mol / L), and water.

[0081] (3) Add lithium ion adsorbent to the lithium-containing leachate and mix. Control the temperature at 40°C and carry out the lithium adsorption reaction for 1 hour to obtain lithium-loaded adsorbent precipitate.

[0082] The lithium-ion adsorbent comprises Li5L2 modified with a hydrophilic group, wherein L is a pentadentate pyrrole ligand containing a photosensitive azo group, the photosensitive azo group is an azopyrrole group, and the hydrophilic group is a hydroxyl group; the molar ratio of lithium ions to lithium-ion adsorbent in the lithium-containing leachate is 1:3.

[0083] (4) Dissolve the lithium-loaded adsorbent precipitate in water to form a dispersion.

[0084] The dispersion was irradiated with ultraviolet light at a wavelength of 365 nm for 2 hours to release lithium ions from the lithium ion adsorbent, resulting in a lithium-rich solution.

[0085] (5) Carbon dioxide gas is introduced into the lithium-rich solution to generate lithium carbonate precipitate. After solid-liquid separation, washing and drying, battery-grade lithium carbonate product is obtained.

[0086] Example 4 The difference between this embodiment and Embodiment 1 is that, during the process of placing the waste lithium battery black material in the leaching agent, a crown ether extractant is also added, and the crown ether extractant is 12-crown-4; the molar ratio of the crown ether extractant to the lithium ions in the lithium-containing leaching solution is 1.1:1.

[0087] The remaining methods and parameters are consistent with those in Example 1.

[0088] Example 5 The difference between this embodiment and embodiment 1 is that in step (1), cryogenic treatment is not performed.

[0089] The remaining methods and parameters are consistent with those in Example 1.

[0090] Example 6 The difference between this embodiment and embodiment 1 is that in step (1), there is no ultraviolet irradiation or microwave assistance.

[0091] The remaining methods and parameters are consistent with those in Example 1.

[0092] Example 7 The difference between this embodiment and embodiment 1 is that nitrogen is not introduced during the crushing process in step (1).

[0093] The remaining methods and parameters are consistent with those in Example 1.

[0094] Example 8 The difference between this embodiment and Embodiment 1 is that the lithium-ion adsorbent does not contain hydrophilic groups, that is, hydrophilic groups are not used to modify Li5L2.

[0095] The remaining methods and parameters are consistent with those in Example 1.

[0096] Example 9 The difference between this embodiment and Embodiment 1 is that the molar ratio of lithium ions to lithium ion adsorbent in the lithium-containing leachate is 1:3.5.

[0097] The remaining methods and parameters are consistent with those in Example 1.

[0098] Example 10 The difference between this embodiment and Embodiment 1 is that the molar ratio of lithium ions to lithium ion adsorbent in the lithium-containing leachate is 1:1.

[0099] The remaining methods and parameters are consistent with those in Example 1.

[0100] Comparative Example 1 The difference between this comparative example and Example 1 is that the lithium-ion adsorbent is replaced with a functionalized adsorbent. The functionalized adsorbent is prepared as follows: MCM-41 molecular sieve is dispersed in ethanol, and aminopropyltriethoxysilane (APTES) is added. The mixture is ball-milled at room temperature for 1 hour to amination the MCM-41 molecular sieve. Then, 15-crown-5 and carbohydroxylethyltriethoxysilane (TEOS-GA) are reacted in ethanol at a 1:1 molar ratio to form a silane bridge. This silane bridge solution is slowly added to the amination of the MCM-41 molecular sieve, and ball-milling continues at room temperature for 2 hours to ensure that 15-crown-5 is firmly attached to the alumina surface via silicon-oxygen bonds. Finally, the mixture is dried at 60°C for 12 hours to obtain the functionalized adsorbent.

[0101] The remaining methods and parameters are consistent with those in Example 1.

[0102] Performance testing The purity of the battery-grade lithium carbonate products recovered in the above examples and comparative examples was tested using inductively coupled plasma optical emission spectrometry (ICP-OES), and the lithium recovery rate was calculated using the formula: Lithium recovery rate = mass of lithium in the product / mass of lithium in waste lithium battery black material × 100%.

[0103] The results are shown in Table 1.

[0104] Table 1 analyze: This invention achieves a green and efficient lithium-ion separation and extraction process by using a metal-organic coordination compound modified with a photosensitive azo group as a lithium-ion adsorbent. This adsorbent can selectively recognize and capture lithium ions in an all-aqueous system through its specific coordination structure, thus completely avoiding the environmental and safety problems caused by the use of volatile and toxic organic solvents in traditional processes, demonstrating significant environmental friendliness. Simultaneously, the photosensitive azo group introduced into the adsorbent gives it unique photoresponsive characteristics, allowing for the controlled release of lithium ions triggered by ultraviolet light irradiation. This enables clean and low-energy operation of the desorption process, further reducing secondary pollution and reagent consumption. Therefore, this recovery process simplifies the separation process while ensuring efficient recovery of lithium resources, meeting the industrial demand for green recycling.

[0105] As can be seen from the comparison between Example 1 and Examples 5-7, if deep cryogenic treatment is not performed, the embrittlement effect of the battery material is insufficient, resulting in uneven particle size and a large number of coarse particles after crushing, which affects the subsequent leaching efficiency and leads to a slight decrease in lithium recovery rate and product purity. If there is no ultraviolet irradiation and microwave assistance in step (1), the organic binder and other components will not decompose completely, and agglomeration is likely to occur during the crushing process, which will also lead to a decrease in the quality of the black material and a decrease in the leaching rate. If nitrogen is not introduced during the crushing process in step (1), there is a risk of local oxidation or thermal runaway, and the "fluidization" effect brought about by airflow disturbance is lacking, resulting in a decrease in crushing efficiency and a wider particle size distribution of the black material.

[0106] As can be seen from the comparison between Example 1 and Example 8, if the lithium-ion adsorbent does not contain hydrophilic groups, that is, if hydrophilic groups are not used to modify Li5L2, the adsorbent has poor dispersibility in the aqueous phase, is prone to agglomeration and sedimentation, and the contact area with lithium ions is greatly reduced, resulting in slow adsorption kinetics and insufficient adsorption capacity, which ultimately seriously affects the lithium recovery rate and product purity.

[0107] A comparison of Examples 1 and 9-10 shows that if the molar ratio of lithium ions to lithium ion adsorbent in the lithium-containing leachate is too small, i.e., the amount of lithium ion adsorbent used is too large, although a high recovery rate can be guaranteed, it will result in a waste of adsorbent material, increase costs, and excessive adsorbent may carry more impurities or increase the volume of subsequent solid-liquid separation, which is not beneficial to improving product purity, and may even reduce the final lithium concentration due to the excessive volume of desorption liquid; if the molar ratio of lithium ions to lithium ion adsorbent in the lithium-containing leachate is too large, i.e., the amount of lithium ion adsorbent used is too small, then after the adsorbent sites are saturated, a large number of lithium ions will still remain in the solution, resulting in a significant decrease in recovery rate.

[0108] As can be seen from the comparison between Example 1 and Comparative Example 1, compared with the functionalized adsorbent used in Comparative Example 1, the lithium-ion adsorbent used in this application achieves a gentler, more thorough and lower energy consumption desorption process due to the light-controlled release characteristics brought by the photosensitive azo group; at the same time, its metal-organic framework structure provides higher density and more specific lithium coordination sites, thus showing significant advantages in both the selective adsorption efficiency of lithium and the purity and recovery rate of the final product.

[0109] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recovering lithium from spent lithium batteries, characterized in that, The method includes the following steps: Waste lithium batteries are pre-treated to obtain waste lithium battery black material; The waste lithium battery black material and leaching agent are mixed and lithium leaching is performed to obtain a lithium-containing leachate; The lithium-containing leachate and lithium-ion adsorbent are mixed and subjected to an adsorption reaction to obtain a lithium-loaded adsorbent precipitate. The lithium-loaded adsorbent precipitate is desorbed to release lithium ions, resulting in a lithium-rich solution. The lithium-rich solution is post-processed to obtain lithium products; The lithium-ion adsorbent is a metal-organic coordination compound modified with a photosensitive azo group.

2. The method according to claim 1, characterized in that, The preprocessing steps include: (a) Preheating the waste lithium battery and then subjecting it to cryogenic treatment to obtain a brittle waste lithium battery body; (b) The embrittled waste lithium battery body is crushed to obtain the waste lithium battery black material; Preferably, the preheating temperature is 100~200℃ and the time is 2~5h; Preferably, the cryogenic treatment is performed at a temperature of -50 to -100°C for 1 to 3 hours.

3. The method according to claim 2, characterized in that, The crushing is carried out under ultraviolet light irradiation and / or microwave-assisted conditions; Preferably, an inert gas is also introduced during the crushing process.

4. The method according to any one of claims 1-3, characterized in that, The leaching agent includes any one or a combination of at least two of oxalic acid, amino acids, persulfates, or fluorides; Preferably, the amino acid includes glycine and / or glutamic acid; Preferably, the persulfate includes any one or a combination of at least two of ammonium persulfate, potassium persulfate, or sodium persulfate; Preferably, the fluoride includes any one or a combination of at least two of ammonium fluoride, potassium fluoride, or sodium fluoride.

5. The method according to any one of claims 1-4, characterized in that, During the lithium leaching process, the pH of the solution system is 1.5 to 2.

5.

6. The method according to any one of claims 1-5, characterized in that, The lithium-ion adsorbent includes Li5L2, wherein L is a pentadentate pyrrole ligand containing a photosensitive azo group; Preferably, the photosensitive azo group is selected from any one or a combination of at least two of the following: azobipyridine group, azophenyl group, or azopyrrole group; Preferably, the organometallic coordination compound is further modified with hydrophilic groups; Preferably, the hydrophilic group includes any one or a combination of at least two of hydroxyl, polyethylene glycol, or sodium sulfonate groups; Preferably, the molar ratio of lithium ions to lithium ion adsorbent in the lithium-containing leachate is 1:(1.5~3).

7. The method according to any one of claims 1-6, characterized in that, The temperature of the adsorption reaction is 25~40℃; Preferably, the adsorption reaction takes 1 to 3 hours.

8. The method according to any one of claims 1-7, characterized in that, During the mixing process of the lithium-containing leachate and the lithium-ion adsorbent, crown ether extractants are also added; Preferably, the crown ether extractant comprises any one or a combination of at least two of 12-crown-4, 15-crown-5, or benzo-15-crown-5; Preferably, the molar ratio of the crown ether extractant to the lithium ions in the lithium-containing leachate is (0.2-2):

1.

9. The method according to any one of claims 1-8, characterized in that, The desorption process includes: The lithium-loaded adsorbent precipitate was dispersed in an aqueous medium and then irradiated with ultraviolet light.

10. The method according to any one of claims 1-9, characterized in that, The method includes the following steps: (1) Provide used lithium batteries; The waste lithium battery is preheated at 100~200℃ for 2~5 hours, and then immediately transferred to -50~-100℃ for 1~3 hours of cryogenic treatment to obtain the embrittled waste lithium battery body. The brittle body of the waste lithium battery is placed in a crusher for crushing to obtain waste lithium battery black material with a particle size D50 of 0.1~0.5mm; The crushing process utilizes ultraviolet light irradiation and microwave assistance; an inert gas is also introduced during the crushing process. (2) Place the waste lithium battery black material in a leaching agent, adjust the pH of the solution system to 1.5~2.5, and control the temperature to 60~90℃, so that the lithium in the waste lithium battery black material is leached out to obtain a lithium-containing leachate. The leaching agent includes any one or a combination of at least two of oxalic acid, amino acids, persulfates, or fluorides; (3) Add lithium ion adsorbent to the lithium-containing leachate and mix. Control the temperature at 25~40℃ and carry out lithium adsorption reaction for 1~3h to obtain lithium-loaded adsorbent precipitate. The lithium-ion adsorbent comprises a metal-organic coordination compound modified with a photosensitive azo group and a hydrophilic group. The photosensitive azo group is selected from any one or a combination of at least two of azobipyridine group, azophenyl group, or azopyrrole group. The hydrophilic group comprises any one or a combination of at least two of hydroxyl group, polyethylene glycol group, or sodium sulfonate group. The molar ratio of lithium ions to lithium-ion adsorbent in the lithium-containing leachate is 1:(1.5~3). (4) Dissolve the lithium-loaded adsorbent precipitate in water to form a dispersion; The dispersion was irradiated with ultraviolet light of wavelength 300~400nm for 2~6h to release lithium ions from the lithium ion adsorbent, thus obtaining a lithium-rich solution. (5) Add a precipitant or introduce carbon dioxide gas into the lithium-rich solution to generate lithium carbonate precipitate. After solid-liquid separation, washing and drying, battery-grade lithium carbonate product is obtained.

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