A continuous production method and product for preparing lithium sulfide from spent lithium batteries.

Abstract

This application pertains to the field of lithium-ion battery recycling, specifically disclosing a continuous production method and product for preparing lithium sulfide from spent lithium batteries. The method mainly includes: pre-treating retired lithium batteries by charging; extracting an active lithium solution by soaking the lithium-containing negative electrode material in a mixed solution of aromatic reagent and ether solvent; reacting the recovered lithium solution with a sulfide precursor at room temperature to generate lithium sulfide; separating the crude lithium sulfide product and a reusable lithium extraction solution, the latter of which is purified and reused for lithium recycling from spent batteries and lithium sulfide preparation, achieving continuous production. This application designs a closed-loop integrated process of recycling-reuse-re-recycling, allowing the lithium extraction solution to be recycled multiple times using simple separation technology. Designed as a continuous operating system, this not only improves production efficiency but also reduces reagent consumption, thereby further reducing production costs.

Description

Technical Field

[0001] This application pertains to the field of lithium-ion battery recycling, and more specifically, relates to a continuous production method and product for preparing lithium sulfide from waste lithium batteries. Background Technology

[0002] Lithium-ion batteries, as key energy storage components in modern electric vehicles and electronic products, are widely used due to their high energy density and long lifespan. However, with the increasing number of lithium-ion batteries and technological upgrades, a large number of them face retirement, leading to the waste of lithium resources and environmental pollution. Therefore, lithium recycling has become crucial for achieving sustainable resource utilization and environmental protection.

[0003] Lithium sulfide, an important lithium-containing compound, is a crucial intermediate in many chemical reactions and material synthesis. It has wide applications in lithium-ion batteries, encompassing cathode materials, solid-state electrolytes, anode materials, interface engineering, and novel battery systems. The application of lithium sulfide not only improves the energy density and cycle life of lithium-ion batteries but also enhances their safety and stability. With the continuous advancement of lithium-ion battery technology and the increasing demand for its applications, lithium sulfide, as an important functional material, has an even broader application prospect. Therefore, the production and utilization of lithium sulfide are of vital importance to the development of lithium energy technology. By recycling lithium resources from spent lithium batteries and extracting and preparing lithium sulfide, we can not only alleviate resource pressure but also promote the sustainable development of the lithium energy industry.

[0004] Patent documents CN 112607712 A and CN 116040587 A disclose a method for preparing lithium sulfide using metallic lithium. This involves mixing metallic lithium and sulfur powder in a certain proportion and reacting them at high temperature in a vacuum oven for an extended period to obtain crude lithium sulfide. The crude product is then subjected to complex ball milling, washing, and drying to finally obtain the final lithium sulfide product. Patent document CN 108358175 B discloses a method for preparing lithium sulfide, in which lithium sulfide, sulfur-rich compounds, metallic lithium, and aromatic compounds are dissolved in an ether-based organic solvent for reaction. The resulting mixed solution containing precipitates is separated, and then heat-treated to obtain lithium sulfide. Patent document CN11157288A discloses a method for synthesizing lithium sulfide, using any one of the following as the lithiation solution: a lithium metal-aromatic compound organic ether solution, a lithium iodide solution, or a n-butyllithium solution. This solution reacts with elemental sulfur to obtain lithium sulfide; the recovered supernatant can be reused. However, existing technologies for reusing lithium extraction solutions typically employ simple centrifugal filtration. This method has drawbacks: other impurities are introduced into the solution during lithium sulfide preparation, and polycyclic aromatic hydrocarbons may decompose into smaller molecules, significantly impacting subsequent reuse. Furthermore, these patented technologies all require expensive, high-purity metallic lithium as raw material, resulting in high production costs, lengthy and complex processes, and ultimately, low purity lithium sulfide products. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to extract active lithium from retired lithium batteries for direct synthesis of lithium sulfide materials, thereby achieving more efficient and high-value applications. A simple and efficient method for recovering and reusing active lithium from retired lithium batteries is developed. This method involves extracting active lithium from retired lithium batteries using a mixed solution prepared with aromatic reagents and ether solvents, and then directly reacting the extracted active lithium solution with a sulfide precursor to prepare lithium sulfide materials.

[0006] To achieve the above objectives, this application provides a continuous production method using spent lithium batteries, comprising the following steps:

[0007] S1. Using an aromatic compound solution with a molar concentration of 0.1M to 2M, extract active lithium from the negative electrode of the spent lithium battery to obtain a lithium-containing solution; the aromatic compound is C6-C. 30 Benzene ring aromatic hydrocarbons or heterocyclic aromatic hydrocarbons containing at least one benzene ring;

[0008] S2. A sulfide precursor is added to a lithium-containing solution, such that the molar ratio of active lithium in the lithium-containing solution to sulfur in the sulfide precursor is (2~2.5):1. After sufficient reaction and separation of solid and liquid, the crude lithium sulfide product and a secondary lithium extraction solution are obtained. The sulfide precursor is sulfur powder, hydrogen sulfide, C1-C6 thiols, and inorganic polysulfides.

[0009] S3. Add 1% to 5% of activated carbon by mass to the secondary lithium extraction solution and purify at 30℃ to 50℃ for 30 min to 120 min;

[0010] S4. Add an aromatic compound to restore the molar concentration of the purified secondary lithium extraction solution to the same level as the aromatic compound solution in step S1; then, treat the secondary lithium extraction solution as the aromatic compound solution and return to step S1.

[0011] Preferably, the activated carbon in step S3 is microporous activated carbon, carboxyl-modified activated carbon, or hydroxyl-modified activated carbon.

[0012] Preferably, microfiltration is further included between steps S3 and S4 to remove activated carbon from the purified secondary lithium extraction solution.

[0013] Preferably, in step S1, the aromatic compound is one or more of biphenyl, naphthalene, phenanthrene, anthracene, tetraphenyl, pyrene, perylene, pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, or phenothiazine.

[0014] As a further preferred embodiment, in step S1, the solvent for the aromatic compound solution is an ether-based organic solvent.

[0015] Preferably, in step S1, the mass ratio of the aromatic compound solution to the negative electrode of the waste lithium battery is (1~5):1.

[0016] Preferably, the inorganic polysulfide has the chemical formula X₂S. n Where X is a lithium ion or ammonium ion, and n is an integer from 2 to 8.

[0017] Preferably, the continuous production method further includes: purifying the crude lithium sulfide product obtained in step S2: cleaning, removing impurities, and purifying the crude lithium sulfide product.

[0018] As a further preferred option, the solvent used for cleaning is ethylene glycol dimethyl ether, tetrahydrofuran, or 2-methyltetrahydrofuran.

[0019] As a further preferred option, the solvent used for impurity removal is n-hexane, cyclohexane, or dichloromethane.

[0020] As a further preferred embodiment, the recrystallization method is annealing at a temperature of 100°C to 600°C for 0.5h to 6h under an argon or helium atmosphere.

[0021] As a further preferred embodiment, the sulfide precursor in step S2 is sulfur powder, the annealing temperature is 200℃~600℃, and the annealing time is 2h~6h.

[0022] As a further preferred embodiment, the sulfide precursor in step S2 is hydrogen sulfide, the annealing temperature is 100℃~500℃, and the annealing time is 0.5h~4h.

[0023] As a further preferred embodiment, the sulfide precursor in step S2 is a C1-C6 thiol or an inorganic polysulfide, the annealing temperature is 100℃~400℃, and the annealing time is 0.5h~3h.

[0024] Preferably, the separation method in step S2 is static sedimentation, vacuum filtration, or positive pressure filtration.

[0025] As a further preferred embodiment, the aromatic compound added in step S4 is 2wt% to 10wt% of the aromatic compound in the aromatic compound solution in step S1.

[0026] This application also provides a crude lithium sulfide product or lithium sulfide prepared using the above method.

[0027] Overall, compared with the prior art, the technical solution conceived in this application realizes the preparation of lithium sulfide from spent lithium batteries, and mainly has the following technical advantages:

[0028] 1. The remaining active lithium in waste lithium batteries can be directly extracted by a simple chemical method. The resulting active lithium solution has high purity and high reactivity. It can spontaneously react with sulfide precursors driven by redox forces. Lithium sulfide samples can be directly synthesized without the need for auxiliary processes such as ball milling and heating.

[0029] 2. Compared with existing technologies, this application uses the active lithium solution recovered from spent lithium batteries as a lithium source to directly prepare lithium sulfide samples under mild reaction conditions, thus realizing the reuse of waste resources. This application avoids the use of costly and complex inorganic lithium salts or metallic lithium as lithium sources in traditional preparation methods, achieving efficient recycling of lithium resources and significantly improving economic benefits.

[0030] 3. Compared with the prior art, this application designs a closed-loop integrated process of recycling-reuse-re-recycling, in which the lithium extraction solution can be recycled multiple times through simple separation technology. It is designed as a continuous operating system. This continuous production mode not only improves production efficiency but also reduces reagent consumption, thereby further reducing production costs.

[0031] 4. Purifying the secondary lithium extraction solution with activated carbon reduces impurities in the solution without excessively consuming its useful components, thus reducing environmental pollution and reagent waste.

[0032] 5. The technical solution of this application has the advantages of high utilization rate of waste resources, high product purity, high economic benefits, and environmental friendliness. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the continuous production process of Embodiment 1 of this application;

[0034] Figure 2 The XRD pattern of low-crystallinity lithium sulfide synthesized in Example 1-1 of this application;

[0035] Figure 3 The XRD pattern of the highly crystalline lithium sulfide powder synthesized in Example 1-1 of this application is shown.

[0036] Figure 4 The XRD pattern of the solid electrolyte synthesized in Example 2-1 of this application;

[0037] Figure 5 The solid electrolyte synthesized in Example 2-1 of this application is used for solid-state battery cycling curves. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0039] Furthermore, throughout this specification, references to "one embodiment"; "one embodiment," "some embodiments," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. Therefore, the appearance of the phrase "in one embodiment;" throughout this specification, along with similar language, may but not necessarily refer to the same embodiment.

[0040] This application provides a method for preparing lithium sulfide using spent lithium batteries, mainly including the following steps:

[0041] S1. The spent lithium batteries undergo a pre-charging treatment to ensure that active lithium is fully embedded in the negative electrode. The negative electrode containing active lithium is then separated through meticulous disassembly. Under an inert atmosphere (such as argon), the negative electrode is immersed in an aromatic compound solution to extract active lithium, and the resulting lithium-containing solution is recovered. The aromatic compound is C6-C. 30The aromatic hydrocarbon solution contains benzene ring aromatic hydrocarbons or heterocyclic aromatic hydrocarbons containing at least one benzene ring, such as biphenyl, naphthalene, phenanthrene, anthracene, tetraphenylene, pyrene, perylene, pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, or phenothiazine, etc.; the concentration of the aromatic hydrocarbon compound solution is 0.1M to 2M (preferably 0.2M to 1M), and the soaking time is 0.5h to 10h, preferably 0.5h to 4h; the solvent of the aromatic hydrocarbon compound solution is an ether organic solvent, such as one or more of ethylene glycol dimethyl ether, tetrahydrofuran, or 2-methyltetrahydrofuran;

[0042] In some embodiments, the charging pretreatment specifically involves: treating waste lithium batteries (batteries whose capacity has decayed to less than 80% of their initial capacity and do not meet the actual application requirements) with constant current / constant voltage charging, with the charging current ranging from 0.01 to 1C, to allow active lithium to migrate and embed into the negative electrode material; then disassembling the charged waste lithium batteries in an environment with a relative humidity of less than 10% to separate the negative electrode material containing active lithium; the negative electrode material of the waste lithium batteries is a carbon-based or silicon-based active material, etc.; including but not limited to one or more of natural graphite, artificial graphite, soft carbon, hard carbon, nano-silicon, carbon-coated nano-silicon, silicon alloy, and silicon-carbon composite materials;

[0043] S2. The lithium content in the lithium-containing solution obtained above is determined by methods such as inductively coupled atomic emission spectrometry (empirical parameters can also be used when processing the same type of waste lithium batteries multiple times). A dry sulfide precursor (active lithium readily reacts with water and deteriorates; the water content of the sulfide precursor should be ≤100ppm, preferably ≤10ppm) is added to the lithium-containing solution. The molar ratio of active lithium in the lithium-containing solution to sulfur in the sulfide precursor is (2~2.5):1, meaning that lithium and sulfur react completely to form lithium sulfide or active lithium is slightly in excess during the reaction. After a spontaneous redox reaction, the solid and liquid are separated (by methods such as static sedimentation, vacuum filtration, or positive pressure filtration) to obtain a low-crystallinity crude lithium sulfide product and a secondary lithium extraction solution, respectively. The reaction of lithium and sulfur can be accelerated by stirring at 200~2000 rpm for 1~48 hours or by ultrasonic vibration at 100W~1500W power. The reaction time is related to the amount of reactants and conditions such as temperature, ultrasonic power, and stirring speed.

[0044] The sulfide precursors are sulfur powder, hydrogen sulfide, C1-C6 thiols, and substances containing -S. n -Polysulfide X2S with β-bond n Where X is a lithium ion or an ammonium ion, and n is an integer from 2 to 8; in some embodiments, the molar ratio of active lithium in the lithium-containing solution to sulfur in the sulfide precursor is preferably (2~2.1):1;

[0045] S3. Because a small amount of polysulfides (Li2S) still exist in the secondary lithium extraction solution after separation. X Impurities (where X = 2, 3, 4, 5, 6) are byproducts generated from the partial reaction of sulfur and lithium. These compounds dissolve in small amounts in the solution and are difficult to completely separate using conventional physical methods. Furthermore, polycyclic aromatic hydrocarbons (PAHs) may undergo other side reactions or cracking during the reaction to generate small molecule aromatic compounds (biphenyl, naphthalene, etc.). These impurities significantly affect the subsequent lithium extraction efficiency. Therefore, the secondary lithium extraction solution needs to be purified to remove impurities. New reagents are then added to compensate for the loss of PAHs, thus achieving the initial solution ratio and ensuring the stability and selectivity of the secondary lithium extraction solution in subsequent reactions. Based on the chemical properties of the impurities, the purification process mainly employs activated carbon adsorption. 1%–5% of activated carbon (by mass of the secondary lithium extraction solution) is added to the secondary lithium extraction solution, and purification is carried out at 30°C–50°C for 30–120 minutes. In some embodiments, the activated carbon is powdered or granular activated carbon, or activated carbon modified with hydroxyl and carboxyl groups. Powdered activated carbon has a smaller particle size and a larger adsorption surface area, enabling rapid adsorption of small molecule impurities and making it more suitable for static or rapid impurity adsorption. Granular activated carbon is suitable for treating large-volume solutions, exhibits good performance under hydrodynamic conditions, and is well-suited for dynamic adsorption systems. Modified activated carbon can enhance the selective adsorption of specific impurities. For example, acidic functional groups can enhance the adsorption of metal ions and polar organic compounds while reducing the impact on polycyclic aromatic hydrocarbons.

[0046] Based on the molecular structure characteristics of impurities such as polysulfides and small-molecule organic compounds, and considering that polycyclic aromatic hydrocarbons (PAHs) are themselves macromolecules, the activated carbon should be selected with a pore size suitable for adsorbing small-molecule impurities, preferably microporous activated carbon (<2 nm). Furthermore, 1 wt% to 10 wt% of mesoporous activated carbon (pore size 2 to 50 nm) can be added to the activated carbon to combine them. This mixing of microporous and mesoporous structures can further improve the adsorption selectivity for certain larger impurities while avoiding excessive adsorption of PAHs. The amount of activated carbon used should be optimized according to the solution volume and impurity concentration. A higher proportion of activated carbon is needed when the impurity content is high. Conversely, when the PAH concentration in the solution is high, excessive use of activated carbon should be avoided to reduce PAH loss. The amount of activated carbon should be controlled at 1 to 5 wt%, and the adsorption time at 0.5 to 2 hours. This balances the impurity removal effect with reducing PAH adsorption. Furthermore, appropriate heating treatment helps to further reduce the adsorption of polycyclic aromatic hydrocarbons. The heating temperature is controlled at 30℃~50℃ to prevent the large-scale volatilization of low-boiling-point solvents. The solution treated with activated carbon adsorption is separated using a microporous membrane (0.1~0.5μm) to obtain a purified secondary lithium extraction solution.

[0047] S4. Add an aromatic compound to restore the molar concentration of the purified secondary lithium extraction solution to the same level as the aromatic compound solution in step S1; return the secondary lithium extraction solution to step S1 as the aromatic compound solution; to ensure that the concentration and amount of reagents used in the cycle do not need to be repeatedly readjusted, the aromatic compound and solvent can be added simultaneously to keep the concentration and mass of the secondary lithium extraction solution the same as the aromatic compound solution in step S1. Typically, adding 2wt%~10wt% of the aromatic compound and 4wt%~7wt% of the solvent from the original aromatic compound solution is sufficient to achieve this. Repeating the above steps enables continuous lithium recovery and lithium sulfide production, achieving maximum utilization efficiency. Experimental results show that the lithium extraction solution can be recycled at least 4 times.

[0048] Following step S2, the crude lithium sulfide product with low crystallinity is washed, impurity removed, and purified to obtain lithium sulfide with high crystallinity. The washing removes excess active lithium solution using ether solvents such as ethylene glycol dimethyl ether, tetrahydrofuran, or 2-methyltetrahydrofuran. The impurity removal removes residual sulfur-containing or hydrocarbon organic impurities using solvents such as n-hexane, cyclohexane, or dichloromethane. The recrystallization method is performed at 100°C under an argon or helium atmosphere. Annealing is performed at a temperature of ~600℃ for 0.5h to 10h. The annealing temperature is related to the type of sulfide precursor. For example, when the sulfide precursor in step S2 is sulfur powder, the annealing temperature is 200℃ to 600℃ and the annealing time is 2h to 6h. When the sulfide precursor in step S2 is hydrogen sulfide, the annealing temperature is 100℃ to 500℃ and the annealing time is 0.5h to 4h. When the sulfide precursor in step S2 is C1-C6 thiols or inorganic polysulfides, the annealing temperature is 100℃ to 400℃ and the annealing time is 0.5h to 3h.

[0049] The highly crystalline lithium sulfide powder obtained by the above method can be directly used to prepare solid electrolyte materials; for the preparation of Li 5.5 PS 4.5 Cl 1.5 For example, specifically:

[0050] The highly crystalline lithium sulfide powder, lithium chloride, and phosphorus pentasulfide were mixed in a molar ratio of 3:1:4 and ground in an argon inert atmosphere until the solid mixture was uniform in color. The mixed solid material was then transferred to a sealed zirconia ball mill jar, and a certain mass of zirconia grinding beads were added. The sealed ball mill jar containing the mixture was ball-milled at 100-300 rpm for 1-2 hours at room temperature. The ball-milled mixture was removed from the ball mill jar under an inert atmosphere, and the mixed solid powder was pressed into sheets under a certain pressure. These sheets were then sealed in a vacuum glass tube and annealed at 400-500℃ for 10-20 hours at a rate of 2-4℃ / min. After cooling to room temperature, the powder was removed, crushed, and sieved to obtain Li. 5.5 PS 4.5 Cl 1.5 Solid electrolyte powder.

[0051] The following is an example:

[0052] Example 1-1

[0053] I. Experimental Preparation

[0054] Pre-treatment of retired batteries:

[0055] S1. The pretreatment of retired batteries mainly adopts a low-current constant current charging method to charge retired lithium iron phosphate batteries (capacity decayed to less than 80% of the initial capacity) to 4.3V (100% SOC) so that the active lithium is completely embedded in the graphite anode material. After the voltage is stabilized, charging is stopped.

[0056] S2. The retired lithium batteries are disassembled and pretreated in a dry room with relative humidity controlled at room temperature and less than 10%. The battery components are separated and the lithium-intercalated graphite negative electrode sheet rich in active lithium is taken out and transferred to an environment filled with argon inert atmosphere. It is then mechanically crushed into a suitable size for later use.

[0057] Prepare the lithium extraction solution: Add 404.5g of pyrene reagent and 2000mL of ethylene glycol dimethyl ether solvent to the reaction vessel, and stir at room temperature until the aromatic reagent is completely dissolved to form a transparent and homogeneous solution (the concentration of the lithium extraction solution is 1mol / L).

[0058] II. Preparation of crude lithium sulfide product

[0059] S1. Mechanically pulverized lithium-containing anode sheets are placed in a lithium extraction solution (i.e., the 1M pyrene in ethylene glycol dimethyl ether solution prepared in step one) at a solid-liquid mass ratio of 1:3. The solution is vigorously stirred at room temperature for 2 hours to extract active lithium. The active lithium in the graphite anode will be extracted through a spontaneous chemical reaction with aromatic reagents. After the reaction is complete, the solution is allowed to settle and filtered to separate the active lithium solution and a solid mixture of graphite anode material and copper foil. The obtained active lithium solution is reserved for later use.

[0060] S2. The lithium content in the obtained active lithium solution was determined by inductively coupled atomic emission spectrometry (ICAES). Sulfate precursor sulfur powder was added in small, multi-step steps under vigorous stirring at a lithium to sulfur molar ratio of 2.05:1. The sulfur powder was reduced and lithiated through a spontaneous chemical reaction. The reaction was carried out at 1500 rpm for 10 hours at room temperature. After complete reaction, the mixture was separated by settling and filtration to obtain crude lithium sulfide solid and a secondary lithium extraction solution using aromatic reagents. The crude lithium sulfide solid was dispersed in ethylene glycol dimethyl ether at a solid-liquid mass ratio of 1:5, stirred, washed, and separated 2-3 times until the filtrate was transparent to remove adsorbed and residual active lithium solution from the lithium sulfide surface, yielding washed crude lithium sulfide powder.

[0061] III. Obtaining Lithium Sulfide

[0062] S1. Disperse the crude lithium sulfide product in n-hexane at a solid-liquid mass ratio of 1:5, stir and separate 1-2 times to remove residual sulfur-containing and hydrocarbon organic impurities, and obtain low-crystallinity lithium sulfide powder after impurity removal.

[0063] S2. The obtained low-crystallinity lithium sulfide powder was placed in a muffle furnace and sintered at 500°C for 2 hours under an argon inert atmosphere. After cooling, a high-crystallinity lithium sulfide powder product was obtained.

[0064] IV. Solid electrolyte synthesis and battery performance testing

[0065] S1. The highly crystalline lithium sulfide, lithium chloride, and phosphorus pentasulfide powders were mixed in a molar ratio of 3:1:4 and ground in an argon inert atmosphere until the solid mixture was uniform in color. The mixed solid material was then transferred to a sealed zirconia ball mill jar, and a certain mass of zirconia grinding beads was added, wherein the weight ratio of zirconia balls to the mixture was 40:1. The sealed ball mill jar containing the mixture was ball-milled at 200 rpm for 2 hours at room temperature. The ball-milled mixture was removed from the ball mill jar under an inert atmosphere, and the mixed solid powder was pressed into sheets under a pressure of 400 MPa. These sheets were then sealed in a vacuum glass tube and annealed at 500°C for 20 hours at a rate of 2°C / min. After cooling to room temperature, the powder was removed, crushed, and sieved to obtain Li.5.5 PS 4.5 Cl 1.5 Solid electrolyte powder.

[0066] S2. Preparation of composite cathode material for solid-state batteries: by using NCM811 cathode, the Li 5.5 PS 4.5 Cl 1.5 Solid electrolyte powder and conductive carbon nanotubes were mixed at a certain mass ratio and ground in a mortar until the solid mixture was homogeneous. The mixture was then transferred to a sealed zirconia ball mill jar for ball milling. The resulting powder was then used as a composite cathode material. The composite cathode material, along with indium foil and lithium foil, were used to assemble an all-solid-state battery to test its performance.

[0067] Examples 1-2

[0068] S3. 2 wt% of powdered activated carbon with a pore size less than 2 nm was added to the secondary lithium extraction solution obtained in step S2 of Example 1-1. Static adsorption was performed at 40°C for 0.5 h. The purified secondary lithium extraction solution was then obtained by filtration through a 0.25 μm microporous membrane. Gas chromatography, liquid chromatography, nuclear magnetic resonance spectroscopy, and mass spectrometry determined that the main impurities in the secondary lithium extraction solution in this example were polysulfides dissolved in the solution and small molecule aromatic compounds (naphthalene, phenanthrene) generated from other side reactions or cracking of polycyclic aromatic hydrocarbons. Before adsorption by activated carbon, the impurity content was 4.7%, while after adsorption, the impurity content was 0.3%. The mass fraction of the aromatic reagent itself was 16.5% before adsorption and 16.0% after adsorption. The total mass reduction of the overall secondary lithium extraction solution compared to the lithium extraction solution in step S1 of Example 1-1 was 9.7%. Subsequently, a certain amount of solute and solvent were added to the above solution to maintain the same reagent and solvent ratio as the lithium extraction solution in step S1 of Example 1-1, and the solution was reused for lithium recovery.

[0069] The subsequent steps are the same as in Example 1-1. The mechanically pulverized lithium-containing anode sheet is placed in a solution at a solid-liquid mass ratio of 1:3. After reaction at room temperature, an active lithium solution and a solid mixture are separated. The lithium content in the obtained active lithium solution is determined by inductively coupled atomic emission spectrometry. Sulfur powder is added again at a lithium to sulfur molar ratio of 2.05:1 to prepare Li₂S. Crude lithium sulfide product solid and a secondary lithium extraction solution using aromatic reagents are separated.

[0070] Examples 1-3

[0071] Repeat Examples 1-2 using the same steps, except that the secondary lithium extraction solution used for the raw materials is the same as the final secondary lithium extraction solution used in Examples 1-2.

[0072] Examples 1-4

[0073] Repeat Examples 1-2 using the same steps, except that the secondary lithium extraction solution used for the raw materials is the same as the secondary lithium extraction solution used in Examples 1-3.

[0074] Table 1 shows the lithium extraction solutions obtained from multiple separations in Examples 1-2, 1-3, and 1-4, which were reused for active lithium extraction and lithium sulfide synthesis from spent batteries after the addition of lost solute and solvent. In this example, the impurity content and the mass of solute loss were determined by elemental analysis, UV-Vis absorption spectroscopy, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy. The changes in impurity and polycyclic aromatic hydrocarbon content during each purification process of the lithium extraction solution were investigated.

[0075] Table 1 shows the changes in impurity and polycyclic aromatic hydrocarbon content before and after purification of the lithium extraction solution in the examples.

[0076]

[0077] Example 2-1

[0078] Repeat the same steps as described in Example 1-1, except that the solvent used for impurity removal in step three is cyclohexane, and the sintering time is 3 hours.

[0079] Example 3-1

[0080] Repeat the same steps as described in Example 1-1, except that the solvent used for impurity removal in step three is dichloromethane, and the sintering time is 1 hour.

[0081] Example 4-1

[0082] The same steps as described in Example 1-1 were repeated, except that in step S2, sulfur powder was added under ultrasonic power of 700W, and the reaction was stirred for 10 hours. In step three, tetrahydrofuran was used as the solvent for cleaning, and the sintering temperature in steps S3-3 was 600℃.

[0083] Example 5-1

[0084] The same steps as described in Example 1-1 are repeated, except that the solvent used for cleaning in step S3-1 is tetrahydrofuran, the solvent used for impurity removal in step three is cyclohexane, and the sintering temperature in step three is 400°C.

[0085] Example 6-1

[0086] The same steps as described in Example 1-1 were repeated, except that in step S2, the reaction conditions were as follows: sulfur powder was added under ultrasonic power of 700W, and then the reaction was stirred for 10 hours. The solvent used for cleaning in step three was 2-methyltetrahydrofuran, and the sintering temperature in steps S3-3 of step two was 300°C.

[0087] Example 7-1

[0088] The same steps as described in Example 1-1 are repeated, except that the solvent used for cleaning in step three is 2-methyltetrahydrofuran, the solvent used for impurity removal in step three is cyclohexane, and the sintering temperature in step three is 200°C.

[0089] Example 8-1

[0090] The same steps as described in Example 1-1 are repeated, except that in step S2, hydrogen sulfide is used instead of sulfur powder as the sulfide precursor, and the reaction is carried out directly by continuously passing it into the active lithium solution. The sintering temperature in step three is 400°C.

[0091] Example 9-1

[0092] The same steps as described in Example 1-1 are repeated, except that the sulfide precursor in step S2 is hydrogen sulfide, which is reacted directly by continuously passing it into an active lithium solution. In step three, cyclohexane is used as the solvent for impurity removal, and the sintering temperature is 400°C with an annealing time of 2 hours.

[0093] Example 10-1

[0094] The same steps as described in Example 1-1 are repeated, except that the sulfide precursor in step S2 is hydrogen sulfide, which is reacted directly by continuously passing it into the active lithium solution. The solvent used for impurity removal in step three is dichloromethane, and the sintering temperature in step three is 400°C, with an annealing time of 1 hour.

[0095] Example 11-1

[0096] The same steps as described in Example 1-1 are repeated, except that the sulfide precursor in step S2 is hydrogen sulfide, which is reacted directly by continuously passing it into an active lithium solution. The solvent used for cleaning in step three is tetrahydrofuran, and the sintering temperature in step three is 300°C, with an annealing time of 1 hour.

[0097] Example 12-1

[0098] The same steps as described in Example 1-1 were repeated, except that the sulfide precursor in step S2 was hydrogen sulfide, which was reacted by continuously passing an active lithium solution through it. The solvent used for cleaning in step three was 2-methyltetrahydrofuran, and the sintering temperature in step three was 200°C, with an annealing time of 1 hour.

[0099] Example 13-1

[0100] The same steps as described in Example 1-1 are repeated, except that the sulfide precursor in step S2 is benzenethiol. In step three, the sintering temperature is 300°C and the annealing time is 2 hours.

[0101] Example 14-1

[0102] The same steps as described in Example 1-1 are repeated, except that the sulfide precursor in step S2 is benzenethiol. The solvent used for cleaning in step three is tetrahydrofuran, the solvent used for impurity removal in step three is cyclohexane, the sintering temperature in step three is 300°C, and the annealing time is 2 hours.

[0103] Example 15-1

[0104] The same steps as described in Example 1-1 are repeated, except that the sulfide precursor in step S2 is benzenethiol. The solvent used for cleaning in step three is 2-methyltetrahydrofuran, the solvent used for impurity removal in step three is dichloromethane, the sintering temperature in step three is 200°C, and the annealing time is 2 hours.

[0105] Example 16-1

[0106] The same steps as described in Example 1-1 were repeated, except that in step S2, ammonium polysulfide (NH4)2S3 was used instead of sulfur powder as the sulfide precursor, and the reaction was carried out by adding 30% ammonium polysulfide solution to the active lithium solution in small amounts multiple times. In step three, the solvent used for cleaning was ethylene glycol dimethyl ether, the solvent used for impurity removal was n-hexane, the sintering temperature was 400°C, and the annealing time was 1 hour.

[0107] Example 17-1

[0108] The same steps as described in Example 1-1 were repeated, except that in step S2, ammonium polysulfide (NH4)2S3 was used instead of sulfur powder as the sulfide precursor, and the reaction was carried out by adding 30% ammonium polysulfide solution to the active lithium solution in small amounts multiple times. In step three, tetrahydrofuran was used as the cleaning solvent, cyclohexane was used as the impurity removal solvent, the sintering temperature was 300°C, and the annealing time was 1 hour.

[0109] Example 18-1

[0110] The same steps as described in Example 1-1 were repeated, except that in step S2, ammonium polysulfide (NH4)2S3 was used instead of sulfur powder as the sulfide precursor, and the reaction was initiated by adding 30% ammonium polysulfide solution to the active lithium solution in small, repeated additions. In step three, 2-methyltetrahydrofuran was used for cleaning, dichloromethane was used for impurity removal, and the sintering temperature was 200°C with an annealing time of 1 hour.

[0111] Example 19-1

[0112] Repeat Example 1-1 with the same steps, except that the molar concentration of the lithium extraction solution in step S1 is 0.1M; the solid-liquid ratio of the active lithium anode sheet to the lithium extraction solution is 1:5; and the molar ratio of lithium to sulfur in step S2 is 2:1.

[0113] Example 20-1

[0114] Repeat Example 1-1 with the same steps, except that the molar concentration of the lithium extraction solution in step S1 is 2M; the solid-liquid ratio of the active lithium anode sheet to the lithium extraction solution is 1:1; and the molar ratio of lithium to sulfur in step S2 is 2.5:1.

[0115] Example 21-1

[0116] Repeat Example 1-1 with the same steps, except that the lithium extraction solution in step S1 is a tetrahydrofuran solution with a molar concentration of 0.2M bipyridine; the solid-liquid ratio of the active lithium anode sheet to the lithium extraction solution is 1:4; and the molar ratio of lithium to sulfur in step S2 is 2.1:1.

[0117] Table 2 summarizes and presents the low-crystallinity lithium sulfide synthesized in Examples 1-18 by adjusting parameters such as the type of sulfide precursor, the type of cleaning solvent, and the type of impurity removal solvent. The yield of low-crystallinity lithium sulfide obtained in different examples (compared to waste lithium batteries) was also tested.

[0118] Table 2 shows the experimental parameters and yields of synthesized low-crystallinity lithium sulfide in Examples 1-18.

[0119]

[0120] Table 3 summarizes and presents the high crystallinity lithium sulfide synthesized in Examples 1-18 by adjusting parameters such as sulfide precursor type, sintering temperature, and annealing time. It also tests the final yield of high crystallinity lithium sulfide obtained in different examples (compared to low crystallinity lithium sulfide).

[0121] Table 3. Experimental parameters and final yields of synthesized highly crystalline lithium sulfide in Examples 1-18.

[0122]

[0123] The XRD patterns of the low-crystallinity and high-crystallinity lithium sulfide powders synthesized in Examples 1-1 of this application are as follows: Figure 1 and Figure 2 As shown in the figure, the diffraction peaks of the synthesized lithium sulfide are completely consistent with those of the standard card, indicating that the lithium sulfide sample was successfully prepared. Testing showed that the purity of the synthesized highly crystalline lithium sulfide reached 99.9%.

[0124] The highly crystalline lithium sulfide synthesized in Example 2-1 of this application is used to synthesize Li 5.5 PS 4.5 Cl 1.5 XRD patterns of solid electrolyte powders are as follows Figure 3 As shown in the figure, the diffraction peaks of the synthesized electrolyte are completely consistent with those of the standard card, indicating that Li was successfully prepared. 5.5 PS 4.5 Cl 1.5 Solid electrolyte sample. The solid electrolyte was used to assemble NCM811@LiNbO3|Li 5.5 PS 4.5 Cl 1.5 | Cyclic performance testing of Li-In solid-state batteries, such as Figure 4 As shown in the figure, it can be seen from the graph that it has good electrochemical performance after cycling at a rate of 0.5C.

[0125] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A continuous production method for preparing lithium sulfide using waste lithium batteries, characterized in that: Includes the following steps: S1. Using an aromatic compound solution with a molar concentration of 0.1 M to 2 M, extract active lithium from the negative electrode of the spent lithium battery to obtain a lithium-containing solution; the aromatic compound is C6-C. 30 Benzene ring aromatic hydrocarbons or heterocyclic aromatic hydrocarbons containing at least one benzene ring; S2. A sulfide precursor is added to a lithium-containing solution, such that the molar ratio of active lithium in the lithium-containing solution to sulfur in the sulfide precursor is (2~2.5):

1. After sufficient reaction and separation of the solid and liquid, crude lithium sulfide and a secondary lithium extraction solution are obtained respectively. The sulfide precursor is sulfur powder, hydrogen sulfide, C1-C6 thiols or inorganic polysulfides. S3. Add 1% to 5% of activated carbon by mass to the secondary lithium extraction solution, and purify at 30℃ to 50℃ for 30 min to 120 min. The activated carbon is microporous activated carbon or a mixture of microporous and mesoporous activated carbon. When the activated carbon is a mixture of microporous and mesoporous activated carbon, the mass of the mesoporous activated carbon is 1 wt% to 10 wt% of the total mass of the activated carbon. S4. Add an aromatic compound to restore the molar concentration of the purified secondary lithium extraction solution to the same level as the aromatic compound solution in step S1; then, treat the secondary lithium extraction solution as the aromatic compound solution and return to step S1.

2. The method as described in claim 1, characterized in that: In step S1, the aromatic compound is one or more of biphenyl, naphthalene, phenanthrene, anthracene, tetraphenyl, pyrene, perylene, pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, or phenothiazine.

3. The method as described in claim 2, characterized in that: In step S1, the solvent for the aromatic compound solution is an ether-based organic solvent.

4. The method as described in claim 1, characterized in that: In step S1, the mass ratio of the aromatic compound solution to the negative electrode of the waste lithium battery is (1~5):

1.

5. The method as described in claim 1, characterized in that: The inorganic polysulfide has the chemical formula X₂S. n Where X is a lithium ion or ammonium ion, and n is an integer from 2 to 8.

6. The method as described in claim 1, characterized in that: Also includes: The crude lithium sulfide product obtained in step S2 is cleaned, impurities are removed, and it is recrystallized to obtain lithium sulfide.

7. The method as described in claim 6, characterized in that: The solvent used for cleaning is ethylene glycol dimethyl ether, tetrahydrofuran, or 2-methyltetrahydrofuran; the solvent used for impurity removal is n-hexane, cyclohexane, or dichloromethane.

8. The method as described in claim 6, characterized in that: The recrystallization method is to anneal at 100℃~600℃ for 0.5h~10h in an argon or helium atmosphere.

9. The method as described in claim 8, characterized in that: The sulfide precursor in step S2 is sulfur powder; the annealing temperature is 200℃~600℃, and the annealing time is 2h~6h; Alternatively, the sulfide precursor in step S2 is hydrogen sulfide, the annealing temperature is 100℃~500℃, and the annealing time is 0.5h~4h; or the sulfide precursor in step S2 is a C1-C6 thiol or inorganic polysulfide, the annealing temperature is 100℃~400℃, and the annealing time is 0.5h~3h.

10. Lithium sulfide prepared by any one of claims 6-9.

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