A method for selectively leaching lithium from a mixture of positive and negative electrode black powder from spent lithium-ion batteries

Abstract

This invention belongs to the field of resource utilization of waste battery electrode materials, specifically providing a method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries. The method involves mixing waste lithium-ion battery black powder, additives, and an aqueous solution containing inorganic acids to form a slurry, which is then placed in a pressure reactor for a hydrothermal reaction to selectively leach lithium. Solid-liquid separation is then performed to obtain a lithium-enriched leachate. The additives are one or more inorganic salts of calcium, magnesium, iron, and aluminum. In the slurry, H... + The molar ratio of the additive to Li is 0.8~1.3:1, the solid-liquid ratio is 100~500 g / L, and the amount of additive is 5~20% of the mass of the black powder; the hydrothermal reaction temperature is not lower than 180℃, and the hydrothermal reaction time is not lower than 1 hour. This invention has a short process, wide adaptability of raw materials, low cost, low pollution, easy process control, and is easy to industrialize.

Description

Technical Field

[0001] This invention belongs to the field of waste battery resource recycling technology, and relates to a method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries. Background Technology

[0002] Waste lithium-ion batteries are rich in key battery elements such as lithium, nickel, cobalt, and manganese. Their resource recycling is of great strategic significance for alleviating global resource supply pressure and promoting sustainable development. Current mainstream recycling processes obtain battery black powder through a "dismantling-crushing-sorting" process. The main components include positive electrode active materials such as Li(NiCoMn)O2 and LiCoO2, as well as graphite. Due to differences in pretreatment processes, the black powder also contains varying degrees of impurities such as iron, aluminum, copper, fluorine, and phosphorus. Traditional hydrometallurgical processes, which simultaneously and completely leach lithium, nickel, cobalt, and manganese, are widely used to treat waste lithium-ion battery black powder. While this can recover valuable metals, lithium extraction at the end of the process suffers from low lithium recovery rates, high reagent consumption, and lengthy processes. Preferential selective extraction of lithium from waste lithium-ion battery black powder is beneficial for improving lithium recovery rates and shortening the overall process flow. Currently, high-temperature reduction-leaching and combined processes such as salt roasting-leaching isothermal-hydrometallurgical extraction are used for preferential lithium extraction. In Chinese patent document CN106129511A, a reducing agent such as lignite / bituminous coal is used to reduce and roast the cathode material at a temperature of 500-750℃, combined with CO2 carbonization and water leaching to achieve preferential lithium extraction. In another Chinese patent document CN113930619A, the cathode material is mixed with concentrated sulfuric acid and roasted at a temperature of 400-600℃, combined with dilute alkaline leaching to achieve preferential lithium extraction. However, these high-temperature reaction processes not only consume a lot of energy but also pose environmental problems such as exhaust gas pollution.

[0003] Compared to the combined fire-hydrometallurgical process, the all-hydrometallurgical process offers advantages such as strong process controllability, high reaction efficiency, and no high-temperature exhaust emissions. Chinese patent document CN109022793A discloses the use of strong oxidants such as perchlorate / persulfate at temperatures of 40–100°C to achieve selective lithium leaching. However, these strong oxidants are costly and pose safety risks. In contrast, the pressure acid leaching process, based on the preferential lithium extraction characteristics of lithium-bearing transition metal oxides (such as Li(NiCoMn)O2 and LiCoO2) in acidic environments, offers lower reagent costs and better selectivity. For example, X. Hu et al. achieved selective preferential leaching of lithium from waste ternary cathode materials through a pressurized acid leaching process with controlled acid dosage (X. Hu, C. Xu, X. Li, et al. Preferential Extraction of Lithium from Spent Cathodes and the Regeneration of Layered Oxides for Li / Na-Ion Batteries, ACS Appl. Mater. Interfaces 2022, 14, 24255−24264), with a lithium leaching rate of up to 98.5% under optimized conditions. However, it is worth noting that the above research focused on high-grade battery black powder with a high degree of sorting containing only cathode materials, without considering the mixed positive and negative electrode black powder generated from actual industrial dismantling. In practice, it has been found that when using a pressurized acid leaching process to treat the mixed positive and negative electrode black powder with high fluorine and phosphorus content generated from actual dismantling, the lithium content in the leaching residue is usually higher than 0.4%, and the lithium leaching rate can only reach about 85%, which is insufficient to meet the lithium yield requirements of industrial processes, limiting the large-scale industrial application of this method. Summary of the Invention

[0004] In order to overcome the shortcomings of existing methods for treating waste lithium-ion battery black powder, the present invention aims to provide a method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries, which aims to improve lithium yield, reduce lithium extraction costs, and reduce environmental pollution.

[0005] Previous research in this invention has shown that the surfaces of unsorted black powder cathode and anode materials contain protective layers such as SEI, with lithium deeply embedded in the material and between layers. Simultaneously, a large number of impurities such as F and P are also present. These impurities significantly affect lithium extraction. Although harsh conditions such as roasting, high acidity, and high temperature can aid lithium extraction, they also affect the selectivity of lithium extraction. To address the problem of selective lithium extraction from ineffectively sorted cathode and anode black powder, this invention provides the following solution:

[0006] A method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries involves mixing waste lithium-ion battery black powder, additives, and an aqueous solution containing inorganic acid to form a slurry, which is then placed in a pressure reactor for hydrothermal reaction to selectively leach lithium. Subsequently, solid-liquid separation is performed to obtain a leachate enriched with lithium.

[0007] The black powder is a mixed powder containing positive electrode active material and graphite negative electrode material from waste lithium-ion batteries, wherein the fluorine content is ≥2 wt.% and / or the phosphorus content is ≥0.4 wt.%; the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide;

[0008] The additive is an inorganic salt of at least one element selected from calcium, magnesium, iron, and aluminum;

[0009] In the slurry, the H in the inorganic acid + The molar ratio of lithium to black powder (H) + The ratio of Li to carbon dioxide (Li) is 0.8 to 1.3:1, the solid-liquid ratio is 100 g / L to 500 g / L, and the amount of additive is 5% to 20% of the mass of the black powder.

[0010] In the hydrothermal reaction, the reaction temperature is not lower than 180℃ and the reaction time is not lower than 1 hour.

[0011] To address the problem of selective lithium extraction from poorly sorted, high-F and / or-P-content, unprocessed cathode and anode black powders, this invention innovatively employs the aforementioned special additives to assist in hydrothermal treatment, further coordinating the type and dosage of additives, and H... + By combining and synergistically controlling the Li / Li ratio, reaction temperature, and slurry solid-liquid ratio, the synergistic effect of ion exchange, redox, and hydrolysis reactions can suppress the formation of slightly soluble lithium compounds such as lithium fluoride and lithium phosphate while preferentially leaching lithium from lithium-containing compounds such as lithium nickel cobalt manganese oxide into the solution. Meanwhile, valuable metals other than lithium, such as transition metals like nickel, cobalt, and manganese, remain in the leaching residue, thus achieving highly efficient and selective leaching of lithium from waste battery black powder.

[0012] In this invention, the black powder can be any positive or negative electrode black powder with industrial recycling value. In particular, for black powder containing a large amount of F and P that is not finely sorted and is difficult to process effectively with existing technologies, the combination of the process and parameters described in this invention can also achieve excellent selective extraction effect of Li.

[0013] As an optional embodiment, the black powder described in this invention is a black powder containing F and P, wherein the content of F can be 2~5 wt.%, and can be as high as 4~5 wt.%, and the content of P can be 0.45~1 wt.%. All content of the components described in this invention refers to weight percentage.

[0014] As an optional embodiment, the black powder is a black powder containing F and P, wherein the F content can be 2~3.5 wt.% and the P content can be 0.6~1 wt.%. In this invention, for black powder with high F and P content, the method of this invention can achieve excellent Li single-stage extraction efficiency and selectivity.

[0015] In this invention, the black powder is also allowed to contain Al, etc. As an optional option, the content of Al in the black powder can be 0.5~3.5 wt.%.

[0016] In this invention, the black powder is allowed to contain at least one transition metal element selected from nickel, cobalt, and manganese. There are no special requirements for the content of the transition metal. For example, it may contain 10-25 wt.% Ni, 2-8 wt.% Co, and 0-15 wt.% Mn; or more specifically, 10-20 wt.% Ni, 3-6 wt.% Co, and 0-10 wt.% Mn.

[0017] Preferably, the inorganic acid is at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0018] In this invention, the additive is at least one inorganic salt of calcium, magnesium, iron, and aluminum; more preferably, it is an inorganic salt of calcium and / or magnesium. Research in this invention shows that inorganic salts of calcium and / or magnesium, as additives, have better compatibility and synergy with the difficult-to-process black powder with its special physicochemical characteristics described in this invention, which helps to further enhance the synergistic effect with the process and further strengthen the selectivity of lithium extraction.

[0019] Preferably, the additive comprises an inorganic salt of calcium and an inorganic salt of magnesium in a weight ratio of 1:0.5~2. Studies have shown that the additive combination of the present invention helps to further adapt to the characteristics of the difficult-to-process black powder, helps to further synergize with the process, and further enhances the selectivity of lithium extraction.

[0020] As an optional embodiment, the additive can be at least one inorganic salt selected from sulfates, hydrochlorides, and nitrates of the cations (calcium, magnesium, iron, and aluminum); furthermore, the anion of the additive can be the same as the anion of the inorganic acid. For example, when sulfuric acid is used in the slurry, calcium sulfate and magnesium sulfate are preferred additives. Similarly, when hydrochloric acid is used in the slurry, calcium chloride and magnesium chloride are preferred additives.

[0021] In this invention, the types of additives, the amount of additives used, and H in the processing process are specified. + The combined control of the lithium ratio, slurry solid-liquid ratio, and hydrothermal reaction temperature is key to achieving high lithium leaching rates and selective lithium leaching.

[0022] Preferably, in the slurry, H + The / Li molar ratio is 0.9~1.1:1; more specifically, it can be 0.95~1.05:1; even more specifically, it can be 1~1.05:1. This invention demonstrates that, under the additive-assisted hydrothermal process described above, in this preferred H... + At the / Li ratio, it can be combined with other parameters to further enhance the lithium extraction rate and selectivity.

[0023] Preferably, the solid-liquid ratio in the slurry is 200 g / L to 400 g / L; more preferably, it is 250 g / L to 350 g / L. This invention demonstrates that, under the additive-assisted hydrothermal process, at this preferred solid-liquid ratio, it can be combined with other parameters to further enhance the lithium extraction rate and selectivity.

[0024] Preferably, the amount of additive in the slurry is 8-15% of the mass of black powder; more preferably, it can be 10-12%. Research in this invention shows that, under the additive-assisted hydrothermal process, this preferred additive, combined with other parameters, can further enhance the extraction rate and selectivity of lithium.

[0025] Preferably, the hydrothermal reaction temperature is 200℃~250℃; more preferably, it can be 210~230℃. Research in this invention shows that at this preferred temperature, it can be further combined and synergistically integrated with other processes to further enhance the lithium extraction rate and selectivity.

[0026] Preferably, the hydrothermal reaction time is 1.5 to 10 hours; more preferably, it can be 2 to 4 hours.

[0027] In this invention, after hydrothermal treatment, solid-liquid separation can be performed using existing methods. These methods include, for example, filtration, sedimentation, and centrifugation.

[0028] The lithium-ion-rich leachate obtained by this invention can yield the desired lithium salt based on conventional extraction / precipitation methods.

[0029] The present invention obtains leaching residue with low lithium content enriched with transition metal elements such as nickel, cobalt, and manganese. Nickel, cobalt, and manganese can be recovered through traditional processes to prepare nickel, cobalt, and manganese products, or a nickel-cobalt mixed solution can be obtained through wet leaching-purification and directly supplied to the ternary material precursor synthesis industry.

[0030] The concept and technical principle of the selective preferential lithium leaching method of this invention are as follows:

[0031] The main component of waste lithium-ion battery black powder, the positive electrode active material, is represented as a lithium-ion transition metal oxide, LiMeO2 (where Me represents Ni, Co, and Mn). When the black powder is mixed with an inorganic acid solution and leached under high temperature and pressure, the following main reaction occurs:

[0032] ;

[0033] ;

[0034] ;

[0035] Reaction (1) is an ion exchange delithiation reaction, reaction (2) is a redox acid leaching reaction, and reaction (3) is a Ni 2+ Co 2+ Mn 2+ The hydrolysis reaction. Reactions (1) and (2) promote lithium leaching, while the high-temperature enhanced conditions cause H to... + Fully consumed and promote co-leaching of Ni 2+ Co 2+ and Mn 2+ Hydrolysis occurs, and the precipitate forms in the residue. Meanwhile, the H produced by hydrolysis reaction (3)... + and the small amount of H remaining in the solution + This will continue to cause reactions (1) and (2) to occur, and the reaction equilibrium will continue to shift towards delithiation and hydrolysis, ultimately achieving preferential selective leaching of lithium.

[0036] However, the study found that when high-pressure acid leaching is used to treat the unprocessed positive and negative electrode mixed black powder with high fluorine and phosphorus content, the lithium leaching rate is often low, and the residual lithium content in the residue is usually between 0.4% and 0.9%, with a lithium preferential leaching rate of less than 85%. In response to this type of difficult-to-treat black powder, this invention innovatively adds additives to the pressurized acid leaching reaction system. By combining the control of parameters such as the composition of the additives, temperature, solid-liquid ratio, and time, synergistic effects can be achieved. This can adapt to the surface physicochemical structure characteristics of this type of black powder with high P and / or F, effectively regulate the chemical behavior of fluorine and phosphorus impurities in the system, suppress lithium phase conversion loss caused by side reactions, and thus significantly improve the lithium leaching rate. Taking calcium- and aluminum-containing inorganic salt additives as an example, the reaction principle includes reactions (4) to (7):

[0037] ;

[0038] ;

[0039] ;

[0040] ;

[0041] In addition, the addition of additives can effectively suppress the rise of HF concentration in the aqueous phase during leaching, reduce the material requirements of high-pressure reaction vessels for fluorine, and reduce the manufacturing cost of high-pressure reaction vessels.

[0042] Beneficial effects

[0043] To address the difficulty in selectively extracting lithium from high-F and / or-P content cathode and anode black powders, this invention innovatively employs the aforementioned special additives to assist in hydrothermal treatment, further coordinating the type and dosage of additives, and H... + The combined and synergistic control of the Li / Li ratio, reaction temperature, and slurry solid-liquid ratio enables synergistic and highly selective extraction of lithium. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of X-ray diffraction of the positive and negative electrode mixed black powder in Example 1.

[0045] Figure 2 This is a schematic diagram of X-ray diffraction of the solid products obtained after pressure acid leaching reaction in Example 1 and Comparative Example 1. Detailed Implementation

[0046] To facilitate understanding of the present invention, the present invention will be described more fully and in detail in conjunction with preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0047] Unless otherwise defined, all technical terms used in this invention have the same meaning as commonly understood by those skilled in the art. The technical terms used in this invention are for the purpose of describing particular embodiments only and are not intended to limit the scope of protection of this invention.

[0048] In embodiments of the present invention, the selective leaching effect is characterized by two indicators: lithium leaching rate and leaching selectivity coefficient. The leaching rate E of the element... i The leaching selectivity coefficient β is calculated according to equations (7) and (8), respectively:

[0049] ;

[0050] ;

[0051] Where E i x represents the leaching rate (%) of element i. i、 y i These represent the mass percentage (%) of element i in black powder and leaching residue, respectively; m o and m r These represent the mass (g) of black powder and leaching residue, respectively. β is the leaching selectivity coefficient, E Li x Liand M Li E represents the leaching rate of Li, the mass percentage of Li in the black powder (%), and the molar mass of Li (g / mol), respectively; j x j M j These represent the leaching rate of element j, the mass percentage of element j in the black powder (%), and the molar mass of element j (g / mol), respectively. Element j includes Ni, Co, and Mn.

[0052] In the following cases, the content of the ingredients in the black powder refers to the weight percentage.

[0053] Example 1

[0054] Waste lithium-ion battery black powder is a mixed powder of high-nickel positive electrode active material and negative electrode graphite (see XRD). Figure 1 The mixture contains 3.41% Li, 16.22% Ni, 3.64% Co, 8.62% Mn, 0.51% Al, 2.80% F, and 0.82% P. Using calcium sulfate as an additive, black powder, calcium sulfate, and dilute sulfuric acid solution are mixed in a stirred reaction tank to form a slurry, controlling the solid-liquid ratio at 300 g / L. The sulfuric acid solution contains H... + With a Li molar ratio of 1.0 to the black powder, the dosage of calcium sulfate additive was set to 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% of the black powder mass, respectively. The slurry was then transferred to a pressure reactor, heated and stirred to 220°C, and maintained at this temperature for 2 hours. After the reaction was complete, solid-liquid separation of the leaching slurry was achieved by vacuum filtration to obtain a lithium-rich leaching solution and a lithium-poor leaching residue (XRD see [reference]). Figure 2 The elemental content in the leaching residue was analyzed, and the leaching rate and leaching selectivity were calculated. The results are shown in Table 1.

[0055] ;

[0056] The results showed that selective leaching of lithium could be achieved under different additive dosages, with lithium leaching rates of 95.28%, 98.78%, 98.54%, and 98.11%, respectively; and leaching selectivity coefficients of 820.8, 3045.3, 2374.3, and 1822.7, respectively. In particular, within the additive dosage range of 10–15 wt.%, the lithium leaching rate was greater than 98%, and the selectivity was greater than 2000.

[0057] Example 2

[0058] The waste lithium-ion battery black powder is the same as in Example 1. This black powder is mixed with a dilute sulfuric acid solution in a stirred reaction tank to form a slurry with a solid-liquid ratio of 300 g / L, and the pH is controlled. +The Li content was 1.0, and the additives were calcium sulfate, magnesium sulfate, ferric sulfate, and aluminum sulfate, each at 10 wt.% of the black powder mass. The slurry was then transferred to a pressure reactor and heated and stirred to 220°C, where it was kept at this temperature and stirred for 4 hours. After the reaction was completed, solid-liquid separation of the leaching slurry was achieved by vacuum filtration, yielding a lithium-rich leaching solution and a lithium-poor leaching residue. The elemental content in the leaching residue was analyzed, and the leaching rate and leaching selectivity were calculated. The results are shown in Table 2.

[0059] ;

[0060] Table 2 shows that selective leaching of lithium can be achieved with calcium sulfate, magnesium sulfate, ferric sulfate, and aluminum sulfate as additives, with lithium leaching rates of 98.78%, 99.09%, 97.23%, and 97.34%, respectively; and leaching selectivity coefficients of 3045.3, 3634.1, 1029.5, and 1022.5, respectively, indicating good selective leaching effects. The selective leaching effect is particularly outstanding when calcium sulfate, magnesium sulfate, and a combination of calcium sulfate and magnesium sulfate are used as additives, with lithium leaching rates exceeding 98% and leaching selectivity coefficients exceeding 3000.

[0061] Example 3

[0062] The waste lithium-ion battery black powder is a mixed powder of lithium nickel cobalt manganese oxide positive electrode active material and graphite negative electrode, containing 3.69% Li, 14.13% Ni, 5.52% Co, 7.79% Mn, 0.81% Al, 4.22% F, and 0.66% P. Using magnesium sulfate as an additive, this black powder, magnesium sulfate, and dilute sulfuric acid solution are mixed in a pressure reactor to form a slurry, controlling the solid-liquid ratio at 200 g / L. The sulfuric acid solution contains H... + The molar ratio of Li in the cathode powder was 1.0. The amounts of magnesium sulfate additive were 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% of the black powder mass, respectively. The mixture was then heated and stirred to 200℃ and maintained at this temperature for 4 hours. After the reaction was complete, solid-liquid separation of the leaching slurry was achieved by vacuum filtration to obtain lithium-rich leaching solution and lithium-poor leaching residue. The elemental content in the leaching residue was analyzed, and the leaching rate and leaching selectivity were calculated. The results are shown in Table 3.

[0063] ;

[0064] Table 3 shows that selective leaching of lithium can be achieved under the conditions of additive dosages of 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% of the black powder mass, with lithium leaching rates of 92.98%, 96.29%, 96.58%, and 96.03%, respectively; and leaching selectivity coefficients of 505.7, 933.7, 980.8, and 765.6, respectively. Among these, when the additive dosage is in the range of 10-15 wt.%, the lithium leaching rate is greater than 96%, and the selectivity coefficient is greater than 900. Examples 1 and 3 demonstrate that this invention can still achieve excellent lithium extraction rate and extraction selectivity even for black powder with an F content as high as 4-5%.

[0065] Example 4

[0066] The waste lithium-ion battery black powder is a mixed powder of lithium nickel cobalt aluminum oxide positive electrode active material and negative electrode graphite, containing 3.44% Li, 12.75% Ni, 5.30% Co, 3.24% Al, 2.48% F, and 0.94% P. Using aluminum nitrate as an additive, this black powder, aluminum nitrate, and dilute nitric acid solution are mixed in a pressure reactor to form a slurry with a solid-liquid ratio of 300 g / L, and the H₂O content is controlled. + / Li is the set value, the amount of aluminum nitrate additive is 10 wt.% of the black powder mass, then heat and stir to the set temperature (220℃), and keep at this temperature for 4 hours. H + The values ​​for / Li were set to 0.8, 0.9, 1.0, 1.1, and 1.2, respectively. After the reaction was completed, solid-liquid separation of the leaching slurry was achieved by vacuum filtration to obtain lithium-rich leaching solution and lithium-poor leaching residue. The elemental content in the leaching residue was analyzed, and the leaching rate and leaching selectivity were calculated. The results are shown in Table 4.

[0067] ;

[0068] As shown in Table 4, in H + Selective leaching of lithium was achieved under conditions of Li / Li ratios of 0.8, 0.9, 1.0, 1.1, and 1.2, with lithium leaching rates of 90.82%, 96.21%, 98.11%, 98.36%, and 98.43%, respectively; leaching selectivity coefficients were 4062.6, 3427.9, 3554.2, 1973.2, and 1216.3, respectively; among which H... + When the Li ratio is in the range of 0.9 to 1.1, the lithium leaching rate is greater than 96% and the selectivity coefficient is greater than 1900.

[0069] Example 5

[0070] The waste lithium-ion battery black powder is a mixed powder of high-manganese positive electrode active material and negative electrode graphite, containing 3.24% Li, 11.44% Ni, 4.60% Co, 11.27% Mn, 1.54% Al, 2.67% F, and 0.81% P. Using ferric chloride as an additive, this black powder, ferric chloride, and dilute hydrochloric acid solution are mixed in a pressure reactor to form a slurry with a solid-liquid ratio of 300 g / L, and the H2O is controlled... + The Li content was 1.0, and the amount of ferric chloride additive was 10 wt.% of the black powder mass. The mixture was then heated and stirred to the set temperature, and the reaction was maintained at this temperature for 2 hours. The set temperatures were 180℃, 200℃, 220℃, and 240℃. After the reaction was complete, solid-liquid separation of the leaching slurry was achieved by vacuum filtration to obtain lithium-rich leaching solution and lithium-poor leaching residue. The elemental content in the leaching residue was analyzed, and the leaching rate and leaching selectivity were calculated. The results are shown in Table 5.

[0071] ;

[0072] Table 5 shows that selective leaching of lithium can be achieved at temperatures of 180℃, 200℃, 220℃, and 240℃, with lithium leaching rates of 93.85%, 96.29%, 98.38%, and 98.32%, respectively; and leaching selectivity coefficients of 231.5, 535.5, 2269.7, and 2312.5, respectively. Among these, the lithium leaching rate is greater than 98% and the leaching selectivity coefficient is greater than 2000 when the reaction temperature is in the range of 220~240℃.

[0073] Example 6

[0074] The waste lithium-ion battery black powder is the same as in Example 5. Using calcium sulfate as an additive, this black powder is mixed with calcium sulfate and dilute sulfuric acid solution in a pressure reactor at a set solid-liquid ratio to form a slurry, with H₂ controlled. + The Li-to-Li ratio was 1.1, and the amount of calcium sulfate additive was 15 wt.% of the black powder mass. The mixture was then heated and stirred to 220℃ and maintained at this temperature for 2 hours. The solid-liquid ratios were set at 100 g / L, 200 g / L, 300 g / L, 400 g / L, and 500 g / L. After the reaction was complete, the leaching slurry was separated into solid and liquid components by vacuum filtration to obtain lithium-rich leaching solution and lithium-poor leaching residue. The elemental content in the leaching residue was analyzed, and the leaching rate and leaching selectivity were calculated. The results are shown in Table 6.

[0075] ;

[0076] Table 6 shows that selective leaching of lithium can be achieved under solid-liquid ratios of 100 g / L, 200 g / L, 300 g / L, 400 g / L, and 500 g / L, with lithium leaching rates of 97.69%, 98.24%, 98.86%, 97.12%, and 94.25%, respectively; and leaching selectivity coefficients of 591.1, 1118.0, 1928.6, 658.4, and 291.3, respectively. Specifically, within the solid-liquid ratio range of 200–400 g / L, the lithium leaching rate is greater than 97%, and the leaching selectivity coefficient is greater than 600.

[0077] Example 7

[0078] The waste lithium-ion battery black powder is a complex mixture of high-nickel positive electrode active material and negative electrode graphite, containing 4.71% Li, 24.35% Ni, 6.04% Co, 7.22% Mn, 0.54% Al, 2.48% F, and 0.47% P. Using magnesium sulfate as an additive, this black powder, magnesium sulfate, and dilute sulfuric acid solution are mixed in a pressure reactor to form a slurry, controlling the solid-liquid ratio at 300 g / L. + The Li content was 0.9%, and the amount of magnesium sulfate additive was 10 wt.% of the black powder mass. The mixture was then heated and stirred to 220℃, and the reaction was maintained at this temperature until the set reaction time was reached. The set reaction times were 1 h, 2 h, 4 h, and 6 h. After the reaction was completed, the solid-liquid separation of the leaching slurry was achieved by vacuum filtration to obtain a lithium-rich leaching solution and a lithium-poor leaching residue. The elemental content in the leaching residue was analyzed, and the leaching rate and leaching selectivity were calculated. The results are shown in Table 7.

[0079] ;

[0080] As shown in Table 7, selective leaching of lithium can be achieved under reaction times of 4 h and 6 h, with lithium leaching rates of 98.11% and 98.19%, respectively; and leaching selectivity coefficients of 4251.3 and 4544.2, respectively.

[0081] Comparative Example 1

[0082] Compared with Example 1, Comparative Example 1 used the same raw materials and operating conditions except for the absence of calcium sulfate additive. The lithium leaching rate obtained in Comparative Example 1 was only 86.61%, while the leaching rates of nickel, cobalt, and manganese were 2.15%, 2.16%, and 2.48%, respectively, with a leaching selectivity coefficient of 280.2. Comparing Example 1 (Table 1) and Comparative Example 1, it can be seen that when the amount of calcium sulfate additive in Example 1 was 10-20 wt.%, the lithium leaching rate obtained was greater than 98%, and the lithium leaching effect obtained in Example 1 was significantly better than that in Comparative Example 1. For selective lithium leaching, a high lithium leaching rate is one of the primary goals. This invention introduces a component in the hydrothermal reaction that can react with F... - PO43- Metal ion additives that form sparingly soluble compounds or stable complexes in the reaction can bring unexpected positive effects, significantly improving the lithium leaching rate and highlighting the key role of additives in hydrothermal reaction systems. Adding an amount of additive greater than 10 wt.% in the hydrothermal system is the preferred condition for obtaining a good lithium leaching rate.

[0083] Comparative Example 2

[0084] Compared with Comparative Example 2, Example 3 used the same raw materials and operating conditions, except that calcium sulfate was not added. Comparative Example 2 achieved a lithium leaching rate of only 85.45%, while the leaching rates for nickel, cobalt, and manganese were 1.53%, 1.61%, and 6.55%, respectively, with a leaching selectivity of 187.3. As shown in Table 3, the lithium leaching rate obtained in Example 3 was significantly better than that in Comparative Example 2. This demonstrates that the addition of additives provides good selective lithium leaching for different types of black powder.

[0085] Comparative Example 3

[0086] Compared with Comparative Example 3 and Example 4, except for H + Aside from the difference in Li, the raw materials and other operating conditions are the same; the only difference lies in the H controlled in Comparative Example 3. + The leaching rates and selectivity of Comparative Example 3 are 0.5 and 1.5, respectively. Table 8 shows the leaching rates and selectivity obtained in Comparative Example 3.

[0087] ;

[0088] When H + When H = 0.5, although the leaching selectivity reaches 888.3, ​​the lithium leaching rate is only 52.23%; when H = 0.5, the lithium leaching rate is only 52.23%. + When the Li / Li ratio is 1.5, the lithium leaching rate is as high as 99.02%, but the leaching selectivity is only 173.6. Comparing Tables 8 and 4, it can be seen that the selective leaching effect obtained in Example 4 is significantly better than that in Comparative Example 3. Therefore, a suitable H... + / Li is an important factor in obtaining good lithium selective leaching effect, H + Both excessively large and excessively small / Li values ​​are detrimental to achieving good selective leaching results.

[0089] Comparative Example 4

[0090] Compared with Example 5, Comparative Example 4 used the same raw materials and other operating conditions, except for the hydrothermal reaction temperature. The only difference was that the temperatures used in Comparative Example 4 were 120°C and 160°C, respectively. The leaching rate and selectivity obtained in Comparative Example 4 are shown in Table 9.

[0091] ;

[0092] The lithium leaching rates obtained in Comparative Example 4 were 51.43% and 78.42%, with leaching selectivity coefficients of 2.5 and 22.6, respectively. The leaching effect obtained in Comparative Example 3 was significantly worse than that in Example 5 (see Table 5). This demonstrates that a hydrothermal reaction temperature of at least 180°C is an important condition for achieving selective lithium leaching.

[0093] Comparative Example 5

[0094] Compared to Example 6, Comparative Example 5 used the same raw materials and operating conditions, except for the solid-liquid ratio. The only difference was that the solid-liquid ratio used in the Comparative Example was 800 g / L. At a solid-liquid ratio of 800 g / L, the leaching pulp had high density and viscosity, resulting in poor mass transfer. Comparative Example 5 achieved a lithium leaching rate of only 84.35%, while the leaching rates for nickel, cobalt, and manganese were 6.23%, 7.32%, and 10.56%, respectively, with a leaching selectivity coefficient of 59.8. Comparing Table 6, Example 6 showed significantly better selective leaching than Comparative Example 5. This demonstrates that a suitable solid-liquid ratio is crucial for obtaining good selective leaching performance.

[0095] Comparative Example 6

[0096] Compared to Example 7, all raw materials and other operating conditions were the same except for the hydrothermal reaction time. The only difference was that the reaction time used in the comparative example was 0.5 hours. The lithium leaching rate obtained in Comparative Example 6 was only 84.63%, while the leaching rates of nickel, cobalt, and manganese were as high as 8.23%, 9.42%, and 12.67%, respectively, with a leaching selectivity coefficient of only 53.5. Comparing Table 8, the selective leaching effect of Example 7 was significantly better than that of Comparative Example 6. This demonstrates that sufficient hydrothermal reaction time is an important guarantee for obtaining good selective leaching results.

[0097] Compared with existing technologies for recycling black powder from waste lithium-ion batteries, this invention has the following advantages:

[0098] 1. For difficult-to-process black powder with high P / F ratio, this invention innovatively employs the aforementioned special additives to assist in hydrothermal treatment, further coordinating the type and dosage of additives, and H... + By combining and synergistically controlling the Li / Li ratio, reaction temperature, and slurry solid-liquid ratio, the synergistic effect of ion exchange, redox, and hydrolysis reactions can suppress the formation of slightly soluble lithium compounds such as lithium fluoride and lithium phosphate while preferentially leaching lithium from lithium-containing compounds such as lithium nickel cobalt manganese oxide into the solution. Meanwhile, valuable metals other than lithium, such as transition metals like nickel, cobalt, and manganese, remain in the leaching residue, thus achieving highly efficient and selective leaching of lithium from waste battery black powder.

[0099] 2. This invention has a high lithium leaching rate and good leaching selectivity. The lithium leaching rate can reach over 95%, and the leaching selectivity can reach over 500. It can obtain lithium-rich leachate with low nickel, cobalt, and manganese content. Compared with the existing full leaching process, the lithium-rich leachate has a lower purification burden, which is conducive to achieving low lithium recovery costs, high lithium recovery rate, and good economic benefits.

[0100] 3. This invention achieves selective leaching of lithium from waste lithium-ion battery black powder through a fully wet process, eliminating the need for high-temperature reduction or high-temperature roasting. Compared to high-temperature reduction-leaching and sulfuric acid roasting-leaching processes, the process flow is shorter, energy consumption is lower, no high-temperature waste gas is generated, and it is environmentally friendly.

[0101] 4. The leaching residue obtained by this invention has a low lithium content, and can be used to recover nickel, cobalt, and manganese through traditional wet processes to prepare nickel, cobalt, and manganese products, or to obtain a nickel-cobalt mixed solution through wet leaching-purification and directly supply it to the ternary material precursor synthesis industry, thus shortening the recovery process of elements such as nickel, cobalt, and manganese.

[0102] 5. This invention is a fully wet process, which is easy to control, has good engineering scale-up effect, and is easy to industrialize.

[0103] The scope of protection of this invention is not limited to the specific embodiments described above. It should be noted that any changes and improvements made by those skilled in the art without departing from the concept of this invention are within the scope of protection of this invention.

Claims

1. A method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries, characterized in that, Waste lithium-ion battery black powder, additives and aqueous solution containing inorganic acid are mixed to form a slurry, which is then placed in a pressure reactor for hydrothermal reaction to selectively leach lithium. Subsequently, solid-liquid separation is performed to obtain a leachate enriched with lithium. The black powder is a mixed powder containing positive electrode active material from waste lithium-ion batteries and graphite negative electrode material, wherein the content of F is 2~5 wt.%; the content of P is 0.45~1 wt.%; the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide; The additive is an inorganic salt of magnesium; or an inorganic salt of calcium and magnesium. In the slurry, the H in the inorganic acid + The molar ratio of Li in the black powder is 0.8~1.3:1, the solid-liquid ratio is 100g / L~500g / L, and the amount of additive is 5~20% of the mass of the black powder; In the hydrothermal reaction, the reaction temperature is not lower than 180℃ and the reaction time is not lower than 1 hour.

2. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries as described in claim 1, characterized in that, In the black powder, the content of F can be 2~3.5 wt.% and the content of P can be 0.6~1 wt.%.

3. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries as described in claim 2, characterized in that, The black powder contains 0.5-3.5 wt.% Al, 10-25 wt.% Ni, 2-8 wt.% Co, and 0-15 wt.% Mn.

4. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries as described in claim 1, characterized in that, The inorganic acid is at least one of sulfuric acid, hydrochloric acid, and nitric acid.

5. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries as described in claim 1, characterized in that, The additive is at least one inorganic salt selected from magnesium sulfate, hydrochloride, and nitrate. Alternatively, the additive may be at least one inorganic salt selected from magnesium and calcium sulfates, hydrochlorides, and nitrates.

6. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from spent lithium-ion batteries as described in claim 5, characterized in that, The additives include inorganic salts of calcium and magnesium in a weight ratio of 1:0.5~2.

7. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries as described in claim 1, characterized in that, H in the inorganic acid + The molar ratio of Li in the black powder is 0.9~1.1:1; The solid-liquid ratio in the slurry is 200 g / L to 400 g / L.

8. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries as described in claim 1, characterized in that, In the slurry, the amount of additive is 8-15% of the mass of black powder.

9. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from waste lithium-ion batteries as described in claim 1, characterized in that, The hydrothermal reaction temperature is 200℃~250℃.

10. The method for selectively leaching lithium from a mixture of positive and negative electrode black powder from spent lithium-ion batteries as described in claim 1, characterized in that, The hydrothermal reaction time is 1.5 to 10 hours.

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