Method for recycling high-purity lithium sulfide from ternary battery powder

Abstract

The invention provides a method for recycling high-purity lithium sulfide from ternary battery powder. The method solves the following technical problems: firstly, the traditional recovery process mainly aims at preparing lithium carbonate, the process is long, the energy consumption is high, and the existing lithium sulfide preparation needs to take high-purity lithium salt as a raw material, so that the cost is high, the reaction condition is harsh, and the product purity is difficult to meet the requirement of a solid-state battery; secondly, the retired ternary battery is complex in component, a leaching solution contains transition metal ions such as nickel, cobalt and manganese and impurities such as calcium, magnesium and fluorine, the impurities are difficult to reduce to the strict standard required by a solid-state battery electrolyte in a traditional purification process, and new impurities are possibly introduced; thirdly, the existing process is insufficient in selective separation and deep purification of lithium, and the lithium is difficult to separate from other metals, so that the purity of the recovered product is low; and 4, complex steps such as ethanol dissolution and crystallization, hydrogen protection calcination and the like are often needed in the existing lithium sulfide preparation, so that the cost is further increased, and large-scale application of lithium sulfide and efficient resource utilization of retired ternary batteries are limited.

Description

A method for recovering high-purity lithium sulfide from ternary battery powder Technical Field

[0001] This invention belongs to the field of resource recycling technology for retired power batteries, specifically relating to a method for recovering high-purity lithium sulfide from ternary battery powder. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage power stations, ternary lithium batteries have become the mainstream energy storage device due to their advantages such as high energy density and long cycle life. However, the large-scale application of ternary lithium batteries has also brought about the problem of recycling and disposing of a large number of retired batteries. Retired ternary batteries contain a variety of valuable metal resources such as nickel, cobalt, manganese, and lithium. Directly discarding them would not only waste resources but also potentially cause environmental pollution due to heavy metal leakage. Therefore, the resource recycling and utilization of retired ternary batteries has become a focus of industry attention.

[0003] In the recycling process of retired ternary lithium batteries, lithium has extremely high recycling value. Lithium sulfide, as a core electrolyte material for solid-state batteries, possesses characteristics such as high ionic conductivity and good electrochemical stability, and has broad application prospects in next-generation high-performance solid-state batteries. Currently, traditional processes for recovering lithium resources from retired ternary lithium batteries mainly focus on the preparation of lithium carbonate, requiring multiple complex steps such as leaching, purification, precipitation, and calcination. This process is lengthy and energy-intensive. Furthermore, existing methods for preparing lithium sulfide mostly use high-purity lithium salts as raw materials, obtaining them through multiple chemical reactions and purification processes. This results in high raw material costs, stringent reaction conditions, and difficulty in achieving the required purity for solid-state batteries (current processes typically only achieve a lithium sulfide purity of 99.9%), limiting the large-scale application of lithium sulfide.

[0004] Furthermore, existing recycling processes still have shortcomings in the selective separation and deep purification of lithium. Retired ternary batteries have complex compositions; in addition to lithium, the leachate contains large amounts of transition metal ions such as nickel, cobalt, and manganese, as well as impurities such as calcium, magnesium, and fluorine. These impurities severely affect the purity of subsequent products. Traditional purification processes struggle to reduce impurity levels to the stringent standards required for solid-state battery electrolytes, and some processes employ steps such as organic solvent dissolution and crystallization, which not only increase production costs but may also introduce new impurities. Therefore, developing a method for recovering high-purity lithium sulfide from ternary battery powder that is short in process flow, low in cost, and produces high-purity products has become a key technological issue for promoting the efficient utilization of retired ternary batteries and the industrialization of solid-state batteries. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a method for recovering high-purity lithium sulfide from ternary battery powder, which solves the problems that traditional recovery processes mainly focus on the preparation of lithium carbonate, resulting in long processes, high energy consumption, and the need for high-purity lithium salts as raw materials in existing lithium sulfide preparation, which leads to high costs, harsh reaction conditions, and difficulty in meeting the purity requirements of solid-state batteries.

[0006] The first aspect of the present invention provides a method for recovering high-purity lithium sulfide from ternary battery powder, comprising the following steps: S1: under high temperature conditions, sulfur dioxide is introduced to reduce nickel, cobalt, and manganese in the ternary battery powder to divalent form, and to convert lithium in the ternary battery powder into lithium sulfate; S2: the product of step S1 is subjected to water leaching for lithium extraction, filtered and separated to obtain a lithium sulfate solution; S3: the lithium sulfate solution is evaporated, concentrated, and purified to obtain a concentrated lithium sulfate solution; S4: the concentrated lithium sulfate solution is evaporated and crystallized to obtain crude lithium sulfate; S5: the crude lithium sulfate is dried and then reduced with hydrogen to obtain high-purity lithium sulfide.

[0007] The high-purity lithium sulfide in this invention refers to lithium sulfide with a purity of 99.99%, a total amount of metal impurities of less than 100 ppm, and a product quality that meets the requirements of lithium sulfide electrolyte for solid-state batteries.

[0008] This invention provides a method for recovering high-purity lithium sulfide from ternary lithium battery powder, which has at least the following beneficial effects: First, the lithium recovery is highly targeted and has a high conversion rate. Step S1 involves introducing sulfur dioxide at high temperature to precisely achieve a dual reaction: reducing nickel, cobalt, and manganese to divalent states (easily separated from lithium), while simultaneously converting lithium to lithium sulfate. This design avoids the formation of difficult-to-separate complexes between lithium and other metal elements, laying the foundation for efficient lithium extraction and significantly improving the lithium recovery rate.

[0009] Secondly, the process is simple and highly efficient. The entire process, from reduction and conversion, water leaching for lithium extraction, to concentration and purification, crystallization, and hydrogen reduction, is tightly integrated with no complex procedures. Water leaching for lithium extraction can quickly separate lithium sulfate from other metallic impurities, and the subsequent concentration and purification steps further remove trace impurities, simplifying the separation and purification operation and reducing production energy consumption and costs.

[0010] Third, the product boasts high purity and significant application value. This invention ultimately removes residual impurities and water of crystallization from crude lithium sulfate by hydrogen reduction, yielding high-purity lithium sulfide. Compared to traditional recycling methods, this process avoids the introduction and accumulation of impurities, resulting in a product purity more readily meeting the demands of high-end applications and enhancing the economic value of the recycled product.

[0011] Fourth, it is well-suited for ternary lithium battery recycling scenarios and has strong practicality. The process design of this invention is perfectly matched to the compositional characteristics of ternary lithium battery powder. Specific reaction conditions and separation methods are selected based on the elemental properties of nickel, cobalt, manganese, and lithium, solving the industry pain points of difficulty in separating lithium from other metals and insufficient product purity in ternary lithium battery recycling, and has significant prospects for industrial application.

[0012] The process flow of this invention is short. The first step produces high-purity lithium sulfate, and the second step directly reduces it to lithium sulfide with high-purity hydrogen. Compared with existing technologies, this process eliminates the need for ethanol dissolution and crystallization of lithium sulfide, as well as hydrogen-protected calcination, significantly reducing production costs. The process from waste ternary lithium powder to high-purity lithium sulfate is extremely short, eliminating the intermediate lithium carbonate production step and further reducing process costs. The yield of high-purity lithium sulfide using this process is far lower than that of competitors, which is beneficial for promoting the commercial application of lithium sulfide solid-state batteries.

[0013] According to some embodiments of the present invention, in step S1, the temperature of the high-temperature condition is 450-750°C.

[0014] According to some embodiments of the present invention, in step S1, the temperature of the high-temperature condition is any value of 450, 500°C, 550°C, 600°C, 650°C, 700°C, or 750°C, such as 550°C, or a range of any two, such as 600°C to 700°C.

[0015] According to some embodiments of the present invention, in step S1, the reduction time is 30-540 min.

[0016] According to some embodiments of the present invention, in step S1, the restoration time is any value among 30min, 60min, 120min, 180min, 240min, 360min, 420min, and 540min, such as 180min, or any range formed by both, such as 120min to 360min.

[0017] According to some embodiments of the present invention, in step S1, the amount of sulfur dioxide used is 0.9-1.1 times the theoretical amount.

[0018] According to some embodiments of the present invention, in step S1, the amount of sulfur dioxide used is any one of 0.9 times, 0.95 times, 1.0 times, 1.05 times, and 1.1 times the theoretical amount, such as 1.0 times, or any range formed by both, such as 0.95 times to 1.05 times.

[0019] According to some embodiments of the present invention, in step S2, the solid-liquid ratio of lithium extraction by water leaching is 1:(1~5).

[0020] According to some embodiments of the present invention, in step S2, the solid-liquid ratio of the water leaching lithium extraction is any value of 1:1, 1:2, 1:3, 1:4, or 1:5, such as 1:3, or any range of two, such as 1:2 to 1:4.

[0021] According to some embodiments of the present invention, in step S2, the leaching temperature for lithium extraction by water leaching is 20-100°C.

[0022] According to some embodiments of the present invention, in step S2, the leaching temperature of the water-based lithium extraction is any value among 20°C, 40°C, 60°C, 80°C, and 100°C, such as 60°C, or any range formed by both, such as 40°C to 80°C.

[0023] According to some embodiments of the present invention, in step S2, the leaching time for lithium extraction by water is 30-360 min.

[0024] According to some embodiments of the present invention, in step S2, the leaching time for lithium extraction by water leaching is any value among 30 min, 60 min, 120 min, 240 min, 300 min, and 360 min, such as 120 min, or any range formed by both, such as 60 min to 240 min.

[0025] According to some embodiments of the present invention, in step S2, the leaching pH of lithium extraction by water is 8-10.

[0026] According to some embodiments of the present invention, in step S2, the leaching pH of the lithium extraction is any value of 8, 8.5, 9, 9.5, 10, such as 9, or a range of any two, such as 8.5 to 9.5.

[0027] According to some embodiments of the present invention, in step S2, the pH is adjusted during the water leaching lithium extraction process, and the pH adjuster is one of lithium carbonate and lithium hydroxide.

[0028] In step S2 of this invention, during the water leaching process for lithium extraction, the leaching pH is adjusted to 8-10, and lithium carbonate and lithium hydroxide are selected as regulating agents. The core purpose is to ensure efficient dissolution and selective separation of lithium, while avoiding interference from impurities. Specifically: + This can promote the stable dissolution of lithium sulfate and inhibit lithium loss. In step S1, the lithium in the ternary battery powder has been converted into lithium sulfate (Li₂SO₄), and lithium sulfate has more stable solubility under neutral to weakly alkaline conditions (avoiding excessive acidity leading to the formation of complexes between lithium and other metals, or excessive alkalinity leading to the formation of lithium hydroxide precipitate). Controlling the pH at 8-10 ensures that lithium sulfate remains in ionic form (Li₂SO₄). +It is fully soluble in water, reducing the decrease in lithium leaching rate caused by precipitation or complexation. The stability of lithium leaching rate in the examples in the specification (no obvious loss) also confirms the rationality of this pH range.

[0029] Furthermore, impurity metal ions can be precipitated in a targeted manner to achieve preliminary separation of lithium from impurities.

[0030] The aqueous leaching solution of retired ternary lithium battery powder contains impurity ions such as nickel, cobalt, manganese (divalent), calcium, and magnesium. Divalent nickel, cobalt, and manganese ions will form insoluble hydroxides (such as Ni(OH)2, Co(OH)2, and Mn(OH)2) in a weakly alkaline environment with pH=8-10, with solubility products Ksp less than 10. -15 These precipitates can be removed directly through subsequent filtration; however, if the pH is below 8, impurity metal ions (such as Mn) are difficult to precipitate completely. 2+ (It still dissolves in large quantities at pH < 8), leading to an increased subsequent purification load; if pH is above 10, excess OH-... - This may cause aluminum to transform into aluminate and dissolve. Therefore, the pH range of 8-10 is the optimal balance range for complete precipitation of impurities and no loss of lithium.

[0031] Furthermore, it can prevent the introduction of new impurities and ensure subsequent purification efficiency.

[0032] Lithium carbonate (Li₂CO₃) or lithium hydroxide (LiOH) is selected as the pH adjuster, instead of conventional bases such as sodium hydroxide (NaOH) and sodium carbonate (Na₂CO₃): both adjusters have Li₂CO₃ as their cation. + When adjusting pH, only Li is introduced. + and CO3² - / OH - (CO3²) - In subsequent evaporation and concentration, it can evaporate with the water or react with a small amount of impurities, leaving no new metal ions; if a regulator containing other cations such as sodium or potassium is used, it will introduce Na+ into the leachate. + K + Impurities such as lithium sulfate crystals are difficult to remove with subsequent lithium-type chelating resins or defluorinating resins, which may ultimately affect the purity of lithium sulfate crystals and even lead to lithium sulfide products failing to meet purity standards.

[0033] According to some embodiments of the present invention, in step S3, the lithium sulfate solution is evaporated and concentrated to a lithium concentration of 20-30 g / L, then a lithium-type chelating resin is used to adsorb divalent metals to reduce the calcium and magnesium concentrations to below 1 ppm, the pH is adjusted to 4-5, a defluorinating resin is used to remove fluoride to reduce the fluoride concentration to below 5 ppm, and then the pH is adjusted to 7-8 with lithium carbonate or lithium hydroxide.

[0034] The deep purification process in step S3 includes a first stage of impurity removal, namely, calcium and magnesium removal by a lithium chelating resin column, and a second stage of pH adjustment, namely, first adjusting the pH to 4-5, then removing fluoride by a fluoride removal resin column, and then adding lithium carbonate to adjust the pH to 7-8.

[0035] In the deep purification process of step S3, the two pH adjustments (first to 4-5 for fluoride removal, then back to 7-8) are key operations designed for different purification targets. The core purpose is to adapt to the optimal working environment of different resins, ensure the efficiency of impurity removal, and avoid introducing new impurities or causing lithium loss. Specifically, the first adjustment of pH to 4-5 is to adapt to the adsorption characteristics of the fluoride removal resin and achieve efficient removal of fluoride ions.

[0036] In step S3, fluoride removal relies on a "fluoride-removing resin" (usually a hydroxyl-type or fluorine-selective chelating resin). The adsorption capacity of these resins is highly sensitive to pH. The optimal pH range for fluoride adsorption is as follows: Under weakly acidic conditions (pH=4-5), the active groups (such as -OH, -PO3H2) of the fluoride-removing resin (e.g., hydroxyapatite type, aminophosphonic acid type) are in a protonated state, making it easier to capture fluoride ions (F ions) through "ion exchange" or "complexation". - — For example, protonated -OH can react with F - Forming hydrogen bonds, or through PO3H2 and F - Ion exchange occurs, significantly increasing the adsorption capacity (adsorption efficiency is 30%-50% higher than under neutral / alkaline conditions).

[0037] To avoid fluoride forming complexes with other ions: If the pH is higher than 5 (neutral / alkaline), trace amounts of calcium and magnesium ions remaining in the leachate (not completely removed by the chelating resin) may react with fluoride. - CaF2 and MgF2 precipitates are formed (Ksp of CaF2 = 3.4 × 10⁻⁶). -11 (These precipitates are easily formed when pH > 5). These precipitates adhere to the resin surface, clogging the resin pores and causing the resin to become "poisoned" and ineffective. If the pH is below 4 (strongly acidic), excessive H+ will cause these precipitates to form. + It will compete with the active groups of the resin for binding sites, inhibiting F - Adsorption can also corrode the resin skeleton, shortening the resin's service life.

[0038] Therefore, pH=4-5 is the optimal range for "high-efficiency adsorption of fluoride removal resin" and "no precipitation interference", which can ensure that the fluoride concentration is reduced to below 5ppm (meeting the impurity requirements of solid-state battery electrolyte).

[0039] The pH is adjusted to 7-8 a second time to create a stable environment for subsequent evaporation and crystallization, ensuring the purity of lithium sulfate.

[0040] After the first defluorination, the solution is weakly acidic (pH=4-5). Directly introducing it into step S4 (evaporation and crystallization) would cause problems. Therefore, it needs to be adjusted back to neutral to weakly alkaline (pH=7-8): This avoids corrosion of the equipment and the introduction of impurities. If the acidic solution directly enters the evaporation and crystallization equipment (such as a stainless steel reactor), prolonged high-temperature heating will cause corrosion, leading to the dissolution of metal ions such as Fe and Cr, and introducing new impurities (these impurities cannot be removed by subsequent crystallization and will ultimately affect the purity of lithium sulfide). A neutral environment of pH=7-8 significantly reduces the risk of equipment corrosion and avoids residual H+ in the solution. + It may undergo side reactions with reagents (such as hydrogen) in subsequent drying and reduction steps.

[0041] The "impurity-free characteristic" of suitable pH adjusters: using lithium carbonate (Li₂CO₃) or lithium hydroxide (LiOH) to adjust the pH introduces only Li₂. + (Supplemental lithium source) and CO3 2- / OH - (CO3) 2- During evaporation, it will be converted into CO2 and volatilize, OH - (No residue) unlike NaOH and Na2CO3, which introduce Na. + Impurities (Na) + It will affect the control of sodium content in the subsequent crystallization mother liquor, and Na+ must be avoided. + >0.1g / L), ensuring the purity of the lithium sulfate crude material.

[0042] According to some embodiments of the present invention, in step S4, the evaporation crystallization rate is 50-100 kg / m³. 3 ·h.

[0043] According to some embodiments of the present invention, in step S4, the lithium sulfate crystallization rate is controlled at 30-70%, with the sodium content in the crystallization mother liquor as the control index. When the sodium content in the crystallization mother liquor is less than 0.1 g / L, the crystallized material is centrifuged to obtain high-purity lithium sulfate crude material. When the sodium content in the crystallization mother liquor is 0.1~1.0 g / L, the crystallized material is centrifuged, then re-dissolved in pure water and recrystallized to obtain high-purity lithium sulfate crude material.

[0044] According to some embodiments of the present invention, in step S5, the drying temperature is 120-500°C.

[0045] According to some embodiments of the present invention, in step S5, the drying temperature is any value among 120°C, 200°C, 240°C, 300°C, 400°C, and 500°C, such as 240°C, or any range formed by both, such as 200°C to 300°C.

[0046] According to some embodiments of the present invention, in step S5, the drying time is 120-360 min.

[0047] According to some embodiments of the present invention, in step S5, the drying time is any value among 120min, 180min, 240min, 300min, and 360min, such as 240min, or any range formed by both, such as 180min to 300min.

[0048] According to some embodiments of the present invention, in step S5, the product is dried until the moisture content is less than 0.01%.

[0049] According to some embodiments of the present invention, in step S5, the reducing atmosphere is hydrogen, or a mixture of hydrogen and nitrogen, and the hydrogen concentration is 5-100%.

[0050] According to some embodiments of the present invention, in step S5, the temperature of hydrogen reduction is 800-1100°C.

[0051] According to some embodiments of the present invention, in step S5, the temperature of hydrogen reduction is any value among 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, and 1100°C, such as 850°C, or any range formed by both, such as 900°C to 1000°C.

[0052] According to some embodiments of the present invention, in step S5, the hydrogen reduction time is 120-360 min.

[0053] According to some embodiments of the present invention, in step S5, the hydrogen reduction time is any value among 120 min, 180 min, 240 min, 300 min, and 360 min, such as 240 min, or any range formed by both, such as 180 min to 300 min.

[0054] According to some embodiments of the present invention, in step S5, the amount of hydrogen used during hydrogen reduction is 110-500% of the theoretical amount (Li2SO4+4H2=Li2S+4H2O).

[0055] According to some embodiments of the present invention, in step S5, the amount of hydrogen used during hydrogen reduction is any value among 110%, 200%, 300%, 400%, and 500% of the theoretical amount, such as 300%, or any range formed by both, such as 200% to 400%.

[0056] According to some embodiments of the present invention, the method further includes, after step S5, cooling and packaging lithium sulfide under high-purity nitrogen protection conditions and storing it under vacuum. Detailed Implementation

[0057] This invention uses retired ternary battery powder as raw material to recycle and prepare high-purity lithium sulfide. On the one hand, it realizes the targeted recycling of lithium resources in retired batteries, avoiding the resource waste and heavy metal pollution caused by traditional disposal or simple treatment, which is in line with the trend of environmental protection and resource recycling. On the other hand, it transforms the recycled lithium resources into high-purity lithium sulfide, the core electrolyte material of solid-state batteries, instead of lithium carbonate in traditional recycling processes, which greatly improves the utilization value of lithium resources and opens up a high-value-added application path for the retired battery recycling industry.

[0058] The simplified process reduces production costs and energy consumption. Compared to existing technologies, the process of this invention eliminates the "lithium carbonate preparation step" in traditional lithium recycling, directly obtaining lithium sulfide from lithium sulfate solution through crystallization, drying, and hydrogen reduction. It also eliminates the need for complex purification steps such as ethanol dissolution and hydrogen-protected calcination, resulting in a shorter and simpler process. Furthermore, the parameters for each step (such as the reduction temperature of S1 at 450-750℃ and the leaching temperature of S2 at 20-100℃) are rationally designed, avoiding high energy consumption caused by extreme reaction conditions. This significantly reduces equipment investment, energy consumption, and time costs in the production process, providing a cost advantage for large-scale industrial applications.

[0059] The product boasts high purity, meeting the core material requirements for solid-state batteries. This invention ensures product purity through multi-stage synergistic control: in S1, sulfur dioxide reduction directionally converts lithium into lithium sulfate, reducing impurity interference; in S3, lithium-type chelating resin removes calcium and magnesium (to below 1 ppm) and defluorinating resin removes fluoride (to below 5 ppm), achieving deep purification; in S4, crystallization rate control and mother liquor sodium content monitoring further purify lithium sulfate; in S5, precise control of hydrogen reduction parameters (110-500% theoretical dosage, 800-1100℃ temperature, etc.) ultimately achieves a lithium sulfide purity of 99.99% and a total metal impurity content of less than 100 ppm, fully meeting the stringent purity requirements of solid-state batteries for lithium sulfide electrolytes, and providing high-quality raw material support for the industrialization of solid-state batteries.

[0060] The process exhibits strong stability and adaptability, facilitating industrial-scale promotion. The parameters for each step in this invention are set within reasonable ranges (e.g., S1 reduction time 30-540 min, S2 solid-liquid ratio 1:(1-5), S5 drying time 120-360 min, etc.), and support flexible adjustments (e.g., selection of different temperatures, times, and dosages). This allows it to adapt to ternary battery powder raw materials of different compositions and batches, avoiding process instability caused by raw material fluctuations. Furthermore, each step (e.g., water immersion, filtration, resin purification, evaporation crystallization, etc.) employs mature industrial-grade processing methods, requiring no special customized equipment. This facilitates rapid adaptation and modification of production lines by existing battery recycling companies or new material companies, lowering the barrier to industrial-scale promotion.

[0061] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0062] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0064] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0065] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0066] The lithium-type chelating resin column is filled with Separate S90 calcium and magnesium chelating resin.

[0067] The fluoride removal resin column is made of CH-32 fluoride removal resin.

[0068] The resin column has an inner diameter of 30mm and a height of 100mm.

[0069] Ternary battery powder is made from waste NCM523 batteries that have been crushed to a particle size of ≤50μm.

[0070] In the embodiments, the purity of the main component lithium sulfide and the content of trace metal impurities were tested according to the "Chemical Analysis Methods for Sulfide Solid Electrolytes" published by the China Society of Automotive Engineers.

[0071] Example 1: A method for recovering high-purity lithium sulfide from ternary battery powder. The specific process is as follows: Step (1): Weigh 20g of waste ternary battery powder into a crucible, put the crucible and the ternary battery powder into a tube furnace, and then introduce sulfur dioxide gas into the tube furnace. To ensure the reaction proceeds fully, the amount of sulfur dioxide used is 1.1 times the theoretical amount, and heat the tube furnace to 600°C and keep it at 600°C for 360 minutes. After that, let the tube furnace cool naturally to collect the sample. Place the recovered sample in a mortar and crush it to obtain lithium-containing powder.

[0072] Step (2): The lithium powder obtained in step (1) is leached in water with a solid-liquid ratio of 1:3. Lithium carbonate is added step by step during the leaching process, the pH value is adjusted to 8, the leaching temperature is 60℃, the leaching time is 60 minutes, and the solution is filtered to obtain lithium sulfate solution.

[0073] Step (3): The lithium sulfate solution is heated and evaporated to concentrate the lithium concentration to 25 g / L to obtain a lithium-rich solution; the first stage of impurity removal is to pass the lithium-rich solution through a lithium-type chelating resin column to reduce calcium and magnesium to below 1 ppm; the second stage of impurity removal is to adjust the pH value to 4 and pass it through a fluoride removal resin column to reduce fluoride to below 5 ppm; then lithium carbonate is added stepwise to adjust the pH value to 7.

[0074] Step (4): Evaporate and crystallize the lithium sulfate solution obtained in step (3). The lithium sulfate crystallization rate is controlled at 53-55%. The sodium content of the crystallization mother liquor is used as the control index. The subsequent operations are carried out in the following two cases: When the sodium content in the crystallization mother liquor is detected to be lower than 0.1 g / L, the obtained crystal material is directly centrifuged for solid-liquid separation. The product after separation is high-purity lithium sulfate. When the sodium content in the crystallization mother liquor is detected to be in the range of 0.1 g / L to 1.0 g / L, the obtained crystal material is first centrifuged for solid-liquid separation, and then the separated crystals are dissolved with high-purity water. After that, the dissolved solution is evaporated, concentrated and recrystallized again, centrifuged, and finally high-purity lithium sulfate is obtained.

[0075] Step (5): Place the high-purity lithium sulfate in a vacuum drying oven and dry it at a temperature of 240℃ for 240 minutes. The product moisture content is less than 0.01%, and dried lithium sulfate is obtained.

[0076] Step (6): Place the dried lithium sulfate in a tube furnace, and then introduce a mixture of hydrogen and nitrogen into the tube furnace. The amount of hydrogen is 120% of the theoretical amount, so that the volume of hydrogen is 50% of the total volume of hydrogen and nitrogen. Heat to 950°C and hold for 240 minutes to carry out the reduction reaction to obtain high-purity lithium sulfide. After testing, the purity of lithium sulfide reaches 99.99%, and the total amount of metal impurities is less than 100 ppm. The product quality meets the requirements of lithium sulfide electrolyte for solid-state batteries.

[0077] Step (7): Under the protection of high-purity nitrogen, the tube furnace is naturally cooled to room temperature, and high-purity lithium sulfide is stored under vacuum.

[0078] Example 2: A method for recovering high-purity lithium sulfide from ternary battery powder. The specific process is as follows: Step (1): Weigh 20g of waste ternary battery powder into a crucible, put the crucible and the ternary battery powder into a tube furnace, and then introduce sulfur dioxide gas into the tube furnace. To ensure the reaction proceeds fully, the amount of sulfur dioxide used is 1.0 times the theoretical amount, and heat the tube furnace to 550°C and keep it at 550°C for 420 minutes. After that, let the tube furnace cool naturally to collect the sample. Place the recovered sample in a mortar and crush it to obtain lithium-containing powder.

[0079] Step (2): The lithium powder obtained in step (1) is leached in water with a solid-liquid ratio of 1:2. Lithium carbonate is added step by step during the leaching process, the pH value is adjusted to 9, the leaching temperature is 40℃, the leaching time is 60 minutes, and the solution is filtered to obtain lithium sulfate solution.

[0080] Step (3): The lithium sulfate solution is heated and evaporated to concentrate the lithium concentration to 28~30g / L to obtain a lithium-rich solution; the first stage of impurity removal is to pass the lithium-rich solution through a lithium-type chelating resin column to reduce calcium and magnesium to below 1ppm; the second stage of impurity removal is to adjust the pH value to 5 and pass it through a fluoride removal resin column to reduce fluoride to below 5ppm; then lithium carbonate is added stepwise to adjust the pH value to 8.

[0081] Step (4): Evaporate and crystallize the lithium sulfate solution obtained in step (3). The lithium sulfate crystallization rate is controlled at 53-55%. The sodium content of the crystallization mother liquor is used as the control index. The subsequent operations are carried out in the following two cases: When the sodium content in the crystallization mother liquor is detected to be lower than 0.1 g / L, the obtained crystal material is directly centrifuged for solid-liquid separation. The product after separation is high-purity lithium sulfate. When the sodium content in the crystallization mother liquor is detected to be in the range of 0.1 g / L to 1.0 g / L, the obtained crystal material is first centrifuged for solid-liquid separation, and then the separated crystals are dissolved with high-purity water. After that, the dissolved solution is evaporated, concentrated and recrystallized again, centrifuged, and finally high-purity lithium sulfate is obtained.

[0082] Step (5): Place the high-purity lithium sulfate in a vacuum drying oven and dry it at a temperature of 150°C for 360 minutes. The product moisture content is less than 0.01%, and dried lithium sulfate is obtained.

[0083] Step (6): Place the dried lithium sulfate in a tube furnace, and then introduce a mixture of hydrogen and nitrogen into the tube furnace. The amount of hydrogen is 110% of the theoretical amount, so that the volume of hydrogen is 60% of the total volume of hydrogen and nitrogen. Heat to 1000℃ and hold for 120 minutes to carry out the reduction reaction to obtain high-purity lithium sulfide. After testing, the purity of lithium sulfide reaches 99.99%, and the total amount of metal impurities is less than 100ppm. The product quality meets the requirements of lithium sulfide electrolyte for solid-state batteries.

[0084] Step (7): Under the protection of high-purity nitrogen, the tube furnace is naturally cooled to room temperature, and high-purity lithium sulfide is stored under vacuum.

[0085] Example 3: A method for recovering high-purity lithium sulfide from ternary battery powder. The specific process is as follows: Step (1): Weigh 20g of waste ternary battery powder into a crucible, put the crucible and ternary electrode powder into a tube furnace, and then introduce sulfur dioxide gas into the tube furnace. To ensure the reaction proceeds fully, the amount of sulfur dioxide is 0.9 times the theoretical amount, and heat the tube furnace to 600°C and keep it at 600°C for 390 minutes. After that, let the tube furnace cool naturally to collect the sample. Place the recovered sample in a mortar and crush it to obtain lithium-containing powder.

[0086] Step (2): The lithium powder obtained in step (1) is leached in water with a solid-liquid ratio of 1:4. Lithium hydroxide is added step by step during the leaching process, the pH value is adjusted to 10, the leaching temperature is 25℃, the leaching time is 30 minutes, and the solution is filtered to obtain lithium sulfate solution.

[0087] Step (3): The lithium sulfate solution is heated and evaporated to concentrate the lithium concentration to 25~28g / L to obtain a lithium-rich solution; the first stage of impurity removal is to pass the lithium-rich solution through a lithium-type chelating resin column to reduce calcium and magnesium to below 1ppm; the second stage of impurity removal is to adjust the pH value to 5 and pass it through a fluoride removal resin column to reduce fluoride to below 5ppm; then lithium hydroxide is added stepwise to adjust the pH value to 7.

[0088] Step (4): Evaporate and crystallize the lithium sulfate solution obtained in step (3). The lithium sulfate crystallization rate is controlled at 53-55%. The sodium content of the crystallization mother liquor is used as the control index. The subsequent operations are carried out in the following two cases: When the sodium content in the crystallization mother liquor is detected to be lower than 0.1 g / L, the obtained crystal material is directly centrifuged for solid-liquid separation. The product after separation is high-purity lithium sulfate. When the sodium content in the crystallization mother liquor is detected to be in the range of 0.1 g / L to 1.0 g / L, the obtained crystal material is first centrifuged for solid-liquid separation, and then the separated crystals are dissolved with high-purity water. After that, the dissolved solution is evaporated, concentrated and recrystallized again, centrifuged, and finally high-purity lithium sulfate is obtained.

[0089] Step (5): Place the high-purity lithium sulfate in a vacuum drying oven and dry it at 300℃ for 120 minutes. The product moisture content is less than 0.01%, and dried lithium sulfate is obtained.

[0090] Step (6): Place the dried lithium sulfate in a tube furnace, and then introduce a mixture of hydrogen and nitrogen into the tube furnace. The amount of hydrogen is 150% of the theoretical amount, so that the volume of hydrogen is 50% of the total volume of hydrogen and nitrogen. Heat to 1100℃ and hold for 180 minutes to carry out the reduction reaction to obtain high-purity lithium sulfide. After testing, the purity of lithium sulfide reaches 99.99%, and the total amount of metal impurities is less than 100ppm. The product quality meets the requirements of lithium sulfide electrolyte for solid-state batteries.

[0091] Step (7): Under the protection of high-purity nitrogen, the tube furnace is naturally cooled to room temperature, and high-purity lithium sulfide is stored under vacuum.

[0092] Comparative Example 1 This Comparative Example 1 is a method for recovering high-purity lithium sulfide from ternary battery powder. The difference between it and Example 1 is that the temperature for reducing the ternary battery powder in step (1) is changed to 400°C.

[0093] In Comparative Example 1, step (1) specifically involves: weighing ternary battery powder into a crucible, placing the crucible and ternary battery powder together into a tube furnace, then introducing sulfur dioxide gas into the tube furnace. To ensure the reaction proceeds fully, the amount of sulfur dioxide used is 1.1 times the theoretical amount, and the tube furnace is heated to 400°C and kept at 400°C for 360 minutes. After that, the tube furnace is allowed to cool naturally to collect the sample. The recovered sample is placed in a mortar and crushed to obtain lithium-containing powder.

[0094] The other steps and reaction parameters are the same as in Example 1.

[0095] The lithium sulfide obtained in Comparative Example 1 had a purity of 97.1%.

[0096] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for recovering high-purity lithium sulfide from ternary lithium battery powder, characterized in that, Includes the following steps: S1: Under high temperature conditions, sulfur dioxide is introduced to reduce nickel, cobalt, and manganese in the ternary battery powder to divalent form, and to convert lithium in the ternary battery powder into lithium sulfate; S2: The product of step S1 is subjected to water leaching to extract lithium, filtered and separated to obtain a lithium sulfate solution; S3: The lithium sulfate solution is evaporated, concentrated and purified to obtain a concentrated lithium sulfate solution. S4: Evaporate and crystallize the concentrated lithium sulfate solution to obtain crude lithium sulfate; S5: Dry the crude lithium sulfate and reduce it in a reducing atmosphere to obtain high-purity lithium sulfide.

2. The method according to claim 1, characterized in that, In step S1, the temperature of the high-temperature condition is 450-750℃; and / or the reduction time is 30-540 min.

3. The method according to claim 1, characterized in that, In step S1, the amount of sulfur dioxide used is 0.9-1.1 times the theoretical amount.

4. The method according to claim 1, characterized in that, In step S2, the solid-liquid ratio of lithium extraction by water leaching is 1:(1~5); and / or, in step S2, the leaching temperature of lithium extraction by water leaching is 20-100℃; and / or, in step S2, the leaching time of lithium extraction by water leaching is 30-360min; and / or, in step S2, the leaching pH of lithium extraction by water leaching is 8-10.

5. The method according to claim 4, characterized in that, In step S2, the pH is adjusted during the water leaching lithium extraction process, and the pH adjuster is either lithium carbonate or lithium hydroxide.

6. The method according to claim 1, characterized in that, In step S3, the lithium sulfate solution is evaporated and concentrated to a lithium concentration of 20-30 g / L. Then, lithium-type chelating resin is used to adsorb divalent metals to reduce the calcium and magnesium concentrations to below 1 ppm. The pH is adjusted to 4-5, and fluoride is removed using a defluorinating resin to reduce the fluoride concentration to below 5 ppm. Finally, the pH is adjusted to 7-8 using lithium carbonate or lithium hydroxide.

7. The method according to claim 1, characterized in that, In step S4, the lithium sulfate crystallization rate is controlled at 30-70%, with the sodium content in the crystallization mother liquor as the control index. When the sodium content in the crystallization mother liquor is less than 0.1 g / L, the crystal material is centrifuged to obtain high-purity lithium sulfate crude material. When the sodium content in the crystallization mother liquor is 0.1~1.0 g / L, the crystal material is centrifuged, then re-dissolved in pure water and recrystallized to obtain high-purity lithium sulfate crude material.

8. The method according to claim 1, characterized in that, In step S5, the drying temperature is 120-500℃; and / or, in step S5, the drying time is 120-360 min; and / or, in step S5, the moisture content is dried to less than 0.01%.

9. The method according to claim 1, characterized in that, In step S5, the reducing atmosphere is hydrogen, or a mixture of hydrogen and nitrogen; and / or, in step S5, the reduction temperature is 800-1100℃; and / or, in step S5, the reduction time is 120-360 min; and / or, in step S5, the amount of hydrogen used during reduction is 110-500% of the theoretical amount.

10. The method according to claim 1, characterized in that, The method further includes, after step S5, cooling and packaging lithium sulfide under high-purity nitrogen protection conditions and storing it under vacuum.