A method for recycling cathode materials from waste lithium batteries

Abstract

This invention discloses a method for recycling waste lithium battery cathode materials, comprising the following steps: (1) collecting waste lithium-ion batteries, performing preliminary discharge treatment, and then immersing them in a salt solution for deep discharge; after air drying, peeling off the outer shell and disassembling to obtain the cathode sheet, and obtaining the cathode material to be treated after scraping, crushing or sieving; (2) adding the cathode material to be treated to a low eutectic solvent H-DES, heating and leaching under stirring conditions, so that the valuable metals in the cathode material enter the leaching system; the low eutectic solvent H-DES is composed of aminosulfonic acid, hydrogen bond acceptor and water in a molar ratio of 1:(0.2-2):(1-10), and refluxed under heating and stirring conditions until a uniform and stable liquid phase is formed; (3) after enriching the obtained leaching solution, it is subjected to low-temperature cooling crystallization to separate the solid phase and the filtrate; ethanol is added to the obtained filtrate as an antisolvent, and after stirring and standing, lithium is precipitated in the form of LiNH4SO4, and the ethanol filtrate containing H-DES and the white precipitate LiNH4SO4 are separated.

Description

Technical Field

[0001] This invention relates to a method for recycling and utilizing cathode materials from waste lithium batteries. Background Technology

[0002] With the rapid development of consumer electronics, electric vehicles, and energy storage devices, the use of lithium-ion batteries continues to increase, resulting in a large number of retired or scrapped lithium-ion batteries. The cathode materials of waste lithium-ion batteries usually contain high-value metal elements such as lithium, cobalt, nickel, and manganese. If they are directly landfilled or improperly disposed of, it will not only waste key metal resources, but may also pose environmental risks due to electrolyte residues and heavy metal migration.

[0003] Existing recycling processes for spent lithium-ion battery cathode materials mainly include pyrometallurgy and traditional hydrometallurgy. Pyrometallurgical processes typically require high-temperature smelting, resulting in high energy consumption, demanding equipment requirements, poor metal selectivity, and difficulty in high-value recovery of lithium from slag. Traditional hydrometallurgical processes typically use strong inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, along with reducing agents such as hydrogen peroxide and sulfites, to dissolve metal elements from the cathode material. While this method offers high leaching efficiency, it suffers from drawbacks such as high acid consumption, strong corrosiveness, high salt content in the waste liquid, long subsequent separation processes, and a significant risk of secondary pollution.

[0004] Eutectic solvents, with their designable components, low volatility, recyclability, and good environmental compatibility, are considered an important green solvent option for metal recovery, replacing traditional strong acid and strong base systems. However, existing eutectic solvent recovery technologies still suffer from the following shortcomings: First, high viscosity or limited mass transfer makes it difficult to increase the solid-liquid ratio; second, multiple metals coexist after leaching, requiring complex extraction, precipitation, or multi-stage pH adjustment for separation; third, high-selectivity separation of lithium from metals such as cobalt, nickel, and manganese is difficult; and fourth, the closed-loop circulation path of eutectic solvents and auxiliary reagents is unclear, resulting in significant chemical consumption and wastewater treatment pressure during industrial scale-up.

[0005] Therefore, there is a need to develop a recyclable and green recycling method that can achieve efficient leaching of cathode materials from waste lithium-ion batteries under relatively mild conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a method for recovering metals from waste lithium battery cathode materials. By constructing an H-DES leaching system, cooling and crystallizing to obtain Co-containing or Ni, Co, and Mn-containing crystals, and antisolvent crystallizing to obtain LiNH4SO4, efficient separation of cobalt and lithium is achieved under relatively mild conditions.

[0007] To achieve the above objectives, the following technical solution is adopted: A method for recycling and utilizing cathode materials from waste lithium batteries includes the following steps: (1) Collect waste lithium-ion batteries, perform preliminary discharge treatment, and then soak them in salt solution for deep discharge; after air drying, peel off the outer shell and disassemble to obtain the positive electrode sheet, and obtain the positive electrode material to be treated after scraping, crushing or sieving. (2) The cathode material to be treated is added to the eutectic solvent H-DES and heated for leaching under stirring conditions, so that the valuable metals in the cathode material enter the leaching system; the eutectic solvent H-DES is composed of aminosulfonic acid, hydrogen bond acceptor and water in a molar ratio of 1:(0.2-2):(1-10), and is refluxed under heating and stirring conditions until a uniform and stable liquid phase is formed; (3) After enriching the leachate, the solid phase and filtrate are separated by low-temperature cooling crystallization. Ethanol is added to the filtrate as an antisolvent, and after stirring and standing, lithium is precipitated in the form of LiNH4SO4. The ethanol filtrate containing H-DES and the white precipitate LiNH4SO4 are separated.

[0008] According to the above scheme, the cathode material to be processed in step (1) is lithium cobalt oxide (LCO) or a ternary cathode material containing Ni, Co, and Mn. For example, NCM811, NCM622, NCM523, NCM111, or NCM721.

[0009] According to the above scheme, the salt solution mentioned in step (1) is a NaCl, Na2SO4, (NH4)2SO4, or Na2CO3 solution. Preferably, it is a 5% NaCl solution.

[0010] According to the above scheme, the hydrogen bond acceptor in step (2) is one or more of methanol, ethanol, ethylene glycol, polyethylene glycol 200, butanediol, glycerol, choline chloride, tetramethylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, and betaine hydrochloride.

[0011] According to the above scheme, the hydrogen bond acceptor in step (2) is ethylene glycol, which is composed of ethylene glycol in a molar ratio of 1:0.5:10.

[0012] According to the above scheme, in step (2), the positive electrode material and the eutectic solvent H-DES are mixed at a solid-liquid ratio of 1-1000 g / L, the leaching temperature is 20-95℃, and the leaching time is 1-30 h. In a preferred scheme, they are mixed at a solid-liquid ratio of 90-130 g / L, the leaching temperature is 75-95℃, and the leaching time is 6-30 h. In a more preferred scheme, they are mixed at a solid-liquid ratio of 110 g / L.

[0013] According to the above scheme, the amount of ethanol added in step (3) is 1-20 times the volume of the filtrate. Preferably, it is 10 times, and the precipitation process is carried out at 10-60℃.

[0014] According to the above scheme, step (3) also includes recovering ethanol and H-DES from the obtained ethanol filtrate containing H-DES by vacuum distillation and recycling it.

[0015] According to the above scheme, step (3) also includes washing the solid product with water and then dissolving it to obtain a metal salt solution containing Ni, Co and Mn, and then selectively separating and recovering it by adjusting the pH or adding a precipitant.

[0016] According to the above scheme, step (3) also includes directly calcining the solid product in situ to obtain oxides containing Ni, Co and Mn, and adding a lithium source for regeneration of waste battery cathode materials.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) High leaching efficiency. Through the hydrogen bond network, acidic sites, and water-mediated mass transfer of the eutectic solvent H-DES, the layered structure of the cathode material can be disrupted under relatively mild conditions, promoting the release of Li, Co, Ni, and Mn. Under optimal conditions, the leaching rates of Co and Li in LCO can reach 99.89% and 100%, respectively; the leaching rates of Li, Co, Ni, and Mn in NCM523 can reach 100%, 99.2%, 99.8%, and 99.9%, respectively.

[0018] (2) High solid-liquid ratio and mild conditions. In the preferred embodiment, the solid-liquid ratio can reach 110 g / L, the reaction temperature is about 90°C, no high-temperature smelting is required, and no large amount of strong corrosive acids and bases and strong oxidizing or reducing agents are required, thus reducing equipment corrosion and safety risks.

[0019] (3) The cobalt-lithium separation process is simple. The leachate is first cooled and crystallized to obtain cobalt-containing crystals, and then LiNH4SO4 is obtained by ethanol antisolvent crystallization, which reduces the need for multi-stage extraction, multiple precipitation or complex pH adjustment separation steps.

[0020] (4) Low chemical consumption and waste liquid burden. Lithium separation mainly relies on ethanol to change solubility, without introducing a large amount of traditional precipitant. Both ethanol and H-DES can be recovered and recycled through vacuum distillation, which helps to reduce the overall treatment cost and secondary pollution.

[0021] (5) The product has a distinct phase. Cobalt salt can yield (NH4)2Co(SO4)2·6H2O, and lithium salt can yield LiNH4SO4; in the example, the purity of LiNH4SO4 was 98.28%, and the purity of the product can be further improved by washing or recrystallization.

[0022] (6) Wide range of applications. This system is not only applicable to lithium cobalt oxide (LCO), but also to ternary cathode materials such as NCM523; for Ni / Co / Mn enriched solid phases, it can be further dissolved for selective precipitation or calcined for regeneration, and has the potential to be coupled with the closed-loop regeneration route of cathode materials.

[0023] (7) Easy to scale up. The process mainly consists of conventional unit operations such as mixing preparation, heating leaching, solid-liquid separation, crystallization, filtration, and vacuum distillation. The equipment is highly versatile and has an engineering basis for continuous or semi-continuous scale-up. Attached Figure Description

[0024] Figure 1 The states of aminosulfonic acid (SA) before (a) and after (b) dissolving in water, and the states before (c) and after (d) forming H-DES.

[0025] Figure 2 Infrared spectra of SA, EG, H2O and H-DES.

[0026] Figure 3 The state of the leachate at different temperatures.

[0027] Figure 4 Leaching rates of Co and Li in H-DES cyclic leaching.

[0028] Figure 5 XRD pattern of (NH4)2Co(SO4)2·6H2O crystals obtained in Example 2.

[0029] Figure 6 XRD pattern of LiNH4SO4 crystals obtained in Example 2.

[0030] Figure 7 SEM images, particle size distribution diagrams, and surface scan diagrams of the (NH4)2Co(SO4)2·6H2O crystals obtained in Example 2.

[0031] Figure 8 SEM image, particle size distribution map, and surface scan image of the LiNH4SO4 crystals obtained in Example 2.

[0032] Figure 9 Infrared spectra before and after ethanol recovery.

[0033] Figure 10 Infrared and nuclear magnetic resonance images of the recovered H-DES. Detailed Implementation

[0034] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following embodiments further illustrate the invention. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention; any equivalent modifications or substitutions made by those skilled in the art without departing from the concept of this invention should fall within the scope of protection of this invention.

[0035] Unless otherwise stated, the specific implementation method is as follows: "H-DES" refers to a eutectic solvent composed of aminosulfonic acid (SA), ethylene glycol (EG), and water (H2O).

[0036] "Solid-liquid ratio" refers to the ratio of the mass (g) of the cathode material to the volume (L) of the leaching agent (g / L).

[0037] Metal leaching rate is calculated using the following formula:

[0038] in η Represents the leaching rate of metal ions; m 0 (g) is the mass of the metal ions initially added to the solvent; C i (mg / L) is the concentration of metal ions measured by a full-spectrum direct-reading plasma atomic emission spectrometer; V i (L) is the volume of the solution after it has been brought to a constant volume.

[0039] Example 1 Step (1): Commercially available waste lithium battery cathode material (such as LiCoO2) was selected as the experimental raw material. For waste lithium batteries, a preliminary discharge was first performed, followed by deep discharge by immersion in a 5% (w / w) salt solution. After 24 hours of discharge, the batteries were air-dried for 12 hours, and the outer casing was peeled off for disassembly to obtain the cathode sheet. The cathode sheet was dried and pulverized for later use.

[0040] Step (2): Sulfamic acid (SA) was used as a hydrogen bond donor, ethylene glycol (EG) as a hydrogen bond acceptor, and water (H2O) as a modifier. The mixture was added to a round-bottom flask and stirred at 70°C for 24 hours until a homogeneous and stable SA-EG-H2O eutectic solvent (H-DES) was formed. The states of sulfamic acid (SA) before (a) and after (b) dissolution in water, and the states before (c) and after (d) formation of H-DES are shown below. Figure 1 As shown. Infrared spectra of SA, EG, H2O, and H-DES in different ratios are attached. Figure 2 As shown.

[0041] Step (3): Weigh 1.1 g of the pretreated LCO cathode material and add it to 10 mL of the H-DES prepared in step (2) (solid-liquid ratio 110 g / L). Place the mixture on a 90℃ constant temperature magnetic stirrer and heat and stir for 24 hours. The appearance of the leachate at different temperatures is as follows. Figure 3 As shown.

[0042] Step (4): After the reaction is complete, allow the mixture to cool naturally to room temperature and let it stand to crystallize. Separate the solid and filtrate by vacuum filtration to obtain a wine-red crystal and a clear solution. If the solid contains undissolved LCO, dissolve it again in deionized water and filter; the filtrate will be a clear wine-red solution.

[0043] Step (5): Under these conditions, the leaching rates of cobalt and lithium are 99.89% and 100%, respectively. When recycling H-DES, the changes in the leaching rates of cobalt and lithium are as follows: Figure 4 As shown. The sequence is initial, first loop, second loop, third loop; the specific data for Li are: 100, 95.19, 85.94, 81.02; the specific data for Co are: 99.89, 88.97, 80.83, 76.43.

[0044] Example 2 This embodiment is the same as steps (1) and (2) of Experiment Example 1.

[0045] Step (3): Weigh 0.9 g of pretreated lithium cobalt oxide cathode material and add it to 10 mL of H-DES prepared under preferred conditions (solid-liquid ratio 90 g / L). Place the flask on an 85℃ constant temperature magnetic stirrer and heat and stir for 6 hours.

[0046] Step (4): After the reaction, allow the mixture to cool naturally and stand to crystallize. Separate the solid and filtrate by vacuum filtration. Dissolve the undissolved LCO in deionized water and then filter. The filtrate is a wine-red solution.

[0047] Step (5): The wine-red filtrate was evaporated under reduced pressure and crystallized to obtain (NH4)2Co(SO4)2·6H2O crystals. The XRD pattern is shown in [reference needed]. Figure 5 As shown. Adding anhydrous ethanol to the clear filtrate precipitated white particles, which were then filtered to obtain LiNH4SO4 lithium salt crystals. The XRD pattern is shown below. Figure 6 As shown. The H-DES solution was recovered by distillation and used in the next leaching round. Under these conditions, the Co leaching rate was 79.82% and the Li leaching rate was 91.68%.

[0048] The obtained (NH4)2Co(SO4)2·6H2O cobalt salt crystals were analyzed by SEM, particle size distribution and elemental surface scan, such as... Figure 7As shown in the figure. SEM results show that the product exhibits a flaky particle aggregate morphology, with particle sizes mainly concentrated in the range of 0.3–0.6 μm. Elemental surface scan results indicate that N, O, S, and Co elements are relatively uniformly distributed within the particle region, suggesting the coexistence of ammonium, sulfate, and cobalt elements in the obtained product.

[0049] The LiNH4SO4 lithium salt crystals obtained in Example 2 were analyzed by SEM, particle size distribution and elemental surface scan, as follows: Figure 8 As shown in the figure. SEM results show that the product mainly exhibits a granular aggregate morphology, with particle sizes concentrated in the range of 1.0–1.6 μm. Elemental surface scan results show that N, O, and S elements are uniformly distributed within the granular regions, indicating the presence of ammonium and sulfate structural units in the product. Due to the low atomic number of Li, conventional EDS is difficult to detect effectively; therefore, the lithium salt phase is mainly bound to... Figure 6 The XRD results confirmed this. Figure 6 and Figure 8 The results show that adding ethanol as an antisolvent to the filtrate can cause LiNH4SO4 to crystallize out, thus achieving the separation and recovery of lithium salt.

[0050] Example 3 This embodiment is the same as steps (1) and (2) of Experiment Example 1.

[0051] Step (3): Weigh 0.9 g of the pretreated LCO cathode material, add it to 10 mL of H-DES (solid-liquid ratio 90 g / L), and heat and stir on a 95℃ constant temperature magnetic stirrer for 30 hours.

[0052] Step (4): After the reaction is complete, cool and filter to obtain a wine-red crystalline substance and a clear solution. Undissolved LCO can be dissolved and filtered again with deionized water.

[0053] Step (5): The wine-red solution was crystallized under reduced pressure to obtain high-purity cobalt salt (NH4)2Co(SO4)2·6H2O. Anhydrous ethanol was added to the clarified filtrate, and the mixture was stirred and allowed to stand to precipitate white lithium salt LiNH4SO4. The precipitate was then filtered, washed, and dried. The resulting H-DES solution can be recovered and reused. Under these conditions, the leaching rates of Co and Li were 96.27% and 98.78%, respectively.

[0054] Example 4 Lithium recovery was performed on the supernatant after separating the wine-red crystals in step (5) of Example 1: Anhydrous ethanol was added to the filtrate, with the amount of ethanol added being 10 times the volume of the filtrate. After stirring evenly and cooling, the lithium salt rapidly and almost completely precipitated out. The white precipitate was collected by filtration, washed with anhydrous ethanol, and dried to obtain lithium ammonium sulfate (LiNH4SO4) product. The purity of the obtained lithium ammonium sulfate was tested to be 98.28%.

[0055] Example 5 The H-DES recovered and replenished in Example 4 was used for the next round of LCO leaching (process conditions were kept consistent with those in Example 1 or within the preferred range). The metal leaching rates for the first cycle were measured to be: Li: 95.19%, Co: 88.97%.

[0056] Infrared spectra before and after ethanol recovery are attached. Figure 9 As shown, the recovered ethanol was essentially unchanged from the original ethanol. The infrared and nuclear magnetic resonance spectra of the recovered H-DES are shown in [reference needed]. Figure 10 As shown, the H-DES system of this invention has the basis of being recyclable and can still maintain a high leaching capacity after repeated use; by further optimizing the replenishment ratio, dehydration or impurity removal method and cycle conditions, the cycle stability can be further improved.

[0057] Example 6 The ternary cathode material NCM523 was used as the cathode material to be treated. H-DES (a eutectic solvent composed of SA, EG, and H2O) was prepared according to the method in Example 1 and set aside. A certain amount of NCM523 cathode material was weighed and added to the H-DES to achieve a solid-liquid ratio of 110 g / L. The mixture was placed under constant temperature stirring conditions and heated and stirred at 90°C for 24 h to carry out the leaching reaction. After the reaction was completed, the mixture was cooled, and solid-liquid separation was performed by vacuum filtration or centrifugation to obtain the leaching solution and leaching residue. The metal ion content of the leaching solution was detected, and the leaching rate was calculated. The results showed that under the above conditions, the leaching rates of each metal in NCM523 could reach: Li 100%, Co 99.2%, Ni 99.8%, and Mn 99.9%, respectively. This indicates that the H-DES system described in this invention is not only suitable for LCO materials but can also achieve efficient synergistic leaching and recovery of multiple metal components in typical ternary cathode materials under mild conditions. In a preferred embodiment, the NCM523 leaching solution can be further separated and solvent recovered according to Examples 3 and 4: for example, firstly, low-temperature cooling and crystallization preferentially precipitates cobalt, nickel, and manganese-containing crystals, and then the filtrate is precipitated with ethanol for lithium precipitation. After low-temperature cooling and crystallization and solid-liquid separation, Ni, Mn, and Co are enriched in the obtained solid phase product; the solid phase is washed with water and then dissolved to obtain a solution containing Ni, Mn, and Co, which can then be recovered and reused by pH-adjusted selective precipitation or conventional separation and recovery methods in the art. At the same time, ethanol is recovered by vacuum distillation and H-DES is recovered for recycling, and the solid after lithium separation is recovered in steps, thereby realizing an integrated process of leaching-separation-solvent closed-loop circulation.

Claims

1. A method for recycling and utilizing cathode materials from waste lithium batteries, characterized in that... Includes the following steps: (1) Collect waste lithium-ion batteries, perform preliminary discharge treatment first, and then soak them in salt solution for deep discharge. After air drying, the outer shell is peeled off and the positive electrode sheet is obtained. After scraping, crushing or sieving, the positive electrode material to be processed is obtained. (2) The cathode material to be treated is added to the eutectic solvent H-DES and heated for leaching under stirring conditions, so that the valuable metals in the cathode material enter the leaching system; the eutectic solvent H-DES is composed of aminosulfonic acid, hydrogen bond acceptor and water in a molar ratio of 1:(0.2-2):(1-10), and is refluxed under heating and stirring conditions until a uniform and stable liquid phase is formed; (3) After enriching the leachate, the solid phase and filtrate are separated by low-temperature cooling crystallization. Ethanol is added to the filtrate as an antisolvent, and after stirring and standing, lithium is precipitated in the form of LiNH4SO4. The ethanol filtrate containing H-DES and the white precipitate LiNH4SO4 are separated.

2. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... The cathode material to be processed in step (1) is lithium cobalt oxide or a ternary cathode material containing Ni, Co and Mn.

3. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... The salt solution mentioned in step (1) is a NaCl, Na2SO4, (NH4)2SO4 or Na2CO3 solution.

4. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... The hydrogen bond acceptor mentioned in step (2) is one or more of methanol, ethanol, ethylene glycol, polyethylene glycol 200, butanediol, glycerol, choline chloride, tetramethylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, and betaine hydrochloride.

5. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... The hydrogen bond acceptor in step (2) is ethylene glycol, and is composed of ethylene glycol in a molar ratio of 1:0.5:

10.

6. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... In step (2), the cathode material and the eutectic solvent H-DES are mixed at a solid-liquid ratio of 1-1000 g / L, and the leaching temperature is 20-95℃, and the leaching time is 1-30 h.

7. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... In step (3), the amount of ethanol added is 1-20 times the volume of the filtrate.

8. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... Step (3) also includes recovering ethanol and H-DES from the obtained ethanol filtrate containing H-DES by vacuum distillation and recycling it.

9. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... Step (3) also includes washing the solid product with water and then dissolving it to obtain a metal salt solution containing Co or Ni, Co, and Mn, and then selectively separating and recovering it by adjusting the pH or adding a precipitant.

10. The method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that... Step (3) also includes directly calcining the solid product in situ to obtain oxides containing Ni, Co, and Mn, and then adding a lithium source for regeneration of waste battery cathode materials.

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