A method for recovering ternary black powder to prepare lithium salt

Abstract

The present application provides a method for recovering ternary black powder to prepare lithium salts, comprising the following steps: step S1: adding a reducing agent to the ternary black powder for roasting to obtain roasted black powder; step S2: adding water to the roasted black powder for water leaching, filtering to obtain a saturated lithium carbonate aqueous solution and undissolved solids; step S3: adding an inorganic acid to the saturated lithium carbonate aqueous solution until the pH is 6.5-7 to obtain a lithium salt aqueous solution; step S4: obtaining the lithium elution rate n of step S2, and determining, based on the lithium elution rate n, whether to wash the undissolved solids or continue to leaching the undissolved solids; step S5: obtaining the lithium salt saturation S of the lithium salt aqueous solution in step S3, and determining, based on the saturation S and the lithium elution rate n, whether to purify the lithium salt aqueous solution or to use the lithium salt aqueous solution as water for leaching in step S2. This method can produce a lithium salt product with high purity.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium battery material recycling, and specifically relates to a method for recycling ternary black powder to prepare lithium salt. Background Art

[0002] As a key component of energy transformation, the new energy vehicle industry has experienced rapid growth in recent years. To address the conflict between resource scarcity and the rapid growth of the new energy industry, the green and efficient recycling of lithium, cobalt, nickel, and manganese from retired new energy vehicle batteries has become a major concern within the new energy industry, both in my country and globally.

[0003] Currently, large-scale industrial recovery of lithium, cobalt, nickel, and manganese from ternary power batteries typically utilizes a wet process. The wet process involves discharging retired batteries, crushing them, heat-treating them, and sorting them into battery black powder. A reducing agent and high-concentration sulfuric acid are then added to the battery black powder to dissolve it into a leachate. A reducing agent and alkali are then added to the leachate to adjust the pH, removing impurities such as copper, iron, and aluminum. A clean solution is then obtained. Nickel, cobalt, and manganese are then extracted from the clean solution using different organic solvents to recover the elements. Finally, sodium carbonate is added at the end of the process to recover the lithium as lithium carbonate precipitate. In the wet recovery process, lithium recovery occurs at the end of the process. During the iron, aluminum, and copper removal and nickel, cobalt, and manganese extraction processes, significant lithium losses occur due to mechanical inclusions. The lithium yield is typically only around 80%. Furthermore, mechanical inclusions reduce the purity of the resulting nickel, cobalt, and manganese, impacting product quality.

[0004] To increase lithium yield and enhance the purity of nickel, cobalt, and manganese products, some companies are using a combined pyrometallurgical and hydrometallurgical process to pre-extract the lithium from ternary materials. This combined pyrometallurgical and hydrometallurgical process involves reducing and roasting ternary battery black powder to produce a calcined powder. Acid is then added to the calcined powder to pre-extract the lithium, producing a lithium-containing wash solution and a lithium-depleted calcined powder. The de-lithiated calcined powder is then subjected to acid dissolution, impurity removal, and organic solvent extraction to recover nickel, cobalt, and manganese. This pre-extraction process increases the lithium recovery rate to approximately 90%.

[0005] However, during the combined wet and pyrometallurgical process, nickel, cobalt, and manganese partially dissolve during the acid elution of lithium. The solubility of manganese accounts for nearly half of the total manganese, resulting in a lithium-containing wash solution containing a large amount of nickel, cobalt, and manganese. This requires a cumbersome process to remove the nickel, cobalt, and manganese from the lithium-containing wash solution, and the resulting lithium compounds are of low purity. Therefore, the industry is in urgent need of a new process to address the problem of nickel, cobalt, and manganese dissolution during the pre-extraction lithium acid elution process. Summary of the Invention

[0006] In view of this, the present application provides a method for recovering ternary black powder to prepare lithium salt, which aims to solve the problem of nickel, cobalt and manganese dissolution during the pre-extraction lithium acid elution process in the existing technical solutions.

[0007] In a first aspect, the present application provides a method for recovering ternary black powder to prepare lithium salt, comprising the following steps:

[0008] Step S1: adding a reducing agent to the ternary black powder and performing a roasting treatment to reduce the high-valent non-lithium active metal elements in the ternary black powder to low-valent non-lithium active metal elements to obtain roasted black powder, wherein the roasted black powder also includes lithium carbonate; wherein the non-lithium active metal elements include nickel, cobalt, and manganese;

[0009] Step S2: adding water to the roasted black powder for water immersion treatment, so that the lithium carbonate in the roasted black powder is dissolved in the water to saturation, and filtering to obtain a saturated lithium carbonate aqueous solution and undissolved solids;

[0010] Step S3: adding an inorganic acid to the saturated lithium carbonate aqueous solution until the pH is 6.5 to 7, so as to convert the lithium carbonate into a lithium salt corresponding to the inorganic acid, thereby obtaining a lithium salt aqueous solution;

[0011] Step S4: obtaining the lithium elution rate n of step S2, and determining whether to perform washing treatment on the undissolved solids or to continue to perform water immersion treatment on the undissolved solids according to the lithium elution rate n;

[0012] Among them, the lithium elution rate

[0013] m1 is the lithium content in the undissolved solid, and m2 is the lithium content in the calcined black powder;

[0014] Step S5: Obtaining the saturation S of the lithium salt in the lithium salt aqueous solution in step S3, and determining, based on the saturation S and the lithium elution rate n, whether the lithium salt aqueous solution is to be purified, or whether the lithium salt aqueous solution is to be used as the water for water immersion in step S2; wherein, the saturation S of the lithium salt in the lithium salt aqueous solution = C / C0; C is the concentration of the lithium salt in the lithium salt aqueous solution, in g / L, and C0 is the saturated solubility of the lithium salt in water, in g / L.

[0015] According to the present application, by utilizing the fact that Ni, Co, MnO and some metal impurities (such as Fe, Cu and Al, etc.) in the roasted black powder are insoluble in water, the solubility of lithium carbonate in water is about 13.3 g / L, the solubility of lithium sulfate in water is about 348 g / L, and the solubility of lithium chloride in water is about 840 g / L; saturated lithium carbonate is first leached out by water leaching, and then an inorganic acid (such as sulfuric acid) is added, and the lithium carbonate becomes a lithium salt corresponding to the inorganic acid (such as lithium sulfate). Since the saturation of lithium carbonate and the lithium salt corresponding to the inorganic acid in water is quite different, the lithium salt aqueous solution corresponding to the inorganic acid can continue to be used for water leaching, that is, the process of repeated water leaching, filtration, acid adjustment and neutralization is used, and the content of impurity elements in the obtained lithium salt aqueous solution is small, and a high-purity lithium salt can be obtained; at the same time, repeated water leaching can fully elute the lithium element in the roasted black powder, thereby improving the recovery rate of the lithium element.

[0016] Specifically, the method obtains roasted black powder by subjecting the ternary black powder to a reduction roasting treatment, wherein the roasted black powder mainly includes Ni, Co, MnO, lithium carbonate and some metal impurities (such as Fe, Cu and Al, etc.), and the lithium carbonate in the roasted black powder is dissolved in water by water immersion to obtain a saturated lithium carbonate aqueous solution and an insoluble solid. It can be understood that the solubility of the insoluble solid in water is extremely low, so that the impurity content in the saturated lithium carbonate aqueous solution is low. Therefore, in this application, the saturated lithium carbonate aqueous solution is further neutralized with an inorganic acid, and the pH is adjusted to 6.5-7 so that the lithium carbonate can be fully converted into a lithium salt corresponding to the inorganic acid (for example, when the inorganic acid is hydrochloric acid or sulfuric acid, the corresponding lithium salt is lithium chloride and lithium sulfate). The insoluble solid is further treated with water immersion using the lithium salt aqueous solution, and of course the impurity content in the obtained lithium salt aqueous solution is also low.

[0017] Subsequently, the lithium elution rate n of the previous water immersion treatment is calculated based on the lithium content m1 in the undissolved solid and the lithium content m2 in the roasted black powder. The lithium elution rate n is used to determine whether to repeat the water immersion treatment of the undissolved solid or to use the undissolved solid for extraction of other non-lithium metal elements after washing. Repeating the water immersion treatment can improve the recovery rate of the lithium element. In addition, the saturation S of the lithium salt in the lithium salt aqueous solution is calculated based on the concentration C of the lithium salt in the lithium salt aqueous solution obtained by acid adjustment and neutralization and the saturated solubility C0 of the lithium salt in water. Based on n and S, it is determined whether to purify the lithium salt aqueous solution or use the lithium salt aqueous solution as the water in step S2 for water immersion treatment. Using the lithium salt aqueous solution for water immersion treatment can reduce water consumption, thereby reducing the cost of subsequent evaporation and crystallization to prepare lithium salt products, improving evaporation efficiency, and saving energy and protecting the environment.

[0018] It can be understood that the present method can fully separate the lithium carbonate from other water-insoluble components (Ni, Co, MnO, Fe, Cu and Al, etc.) in the roasted black powder by repeated water immersion treatment, so that the lithium salt aqueous solution obtained by acid adjustment and neutralization has fewer impurities and a lithium salt product with higher purity can be obtained; in addition, by acid adjustment and neutralization and repeated water immersion, the recovery rate of the lithium element can be improved while saving water and the cost of subsequent evaporation and crystallization.

[0019] It should be noted that the saturated solubility C0 of lithium salt in water has a well-known meaning in the art, and its value is related to temperature. When calculating the saturation S of lithium salt in a lithium salt aqueous solution, C0 is the saturated solubility of lithium salt in water at the detection temperature.

[0020] In some embodiments, step S4 includes: if the lithium elution rate n of the step S2 satisfies n>n0, washing the insoluble solid to obtain a delithiation solid product; if the lithium elution rate n of the step S2 satisfies n≤n0, using the insoluble solid as the roasted black powder in the step S2 and repeating step S2 to continue water immersion treatment until the lithium elution rate n>n0; wherein n0 is the target lithium elution rate, and the value range of n0 is: 97%≤n0≤99%.

[0021] In some of the above-mentioned embodiments, specific limitations are placed on how to treat the undissolved solids based on the lithium elution rate after water leaching. Setting the target lithium elution rate n0 to 97% to 99% can further improve the recovery rate of the lithium element. Specifically, if the lithium elution rate n after the previous water leaching is less than or equal to n0, it indicates that the undissolved solids still contain a large amount of lithium carbonate. The undissolved solids can then be repeatedly water-leached until n is greater than n0 to improve the recovery rate of the lithium element. If n is greater than n0, it indicates that the lithium content in the undissolved solids is low and the product can be used as a delithiated solid product for the recovery of other non-lithium metal elements. For example, the delithiated solid product can be subjected to acid dissolution, impurity removal, and organic solvent extraction to recover the Ni, Co, and Mn elements therein.

[0022] In some embodiments, step S5 includes: if the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S>S0, purifying the lithium salt aqueous solution as a lithium-containing solution to obtain a lithium salt product; if the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S≤S0, and the lithium elution rate n≤n0, determining that the lithium salt aqueous solution is subjected to treatment A, wherein the treatment A includes: using the lithium salt aqueous solution as the water in step S2 and repeating steps S2 and S3 until the saturation S is greater than S0; if the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S≤S0, and the lithium elution rate n>n0, determining that the lithium salt aqueous solution is subjected to treatment B, wherein the treatment B includes: purifying the lithium salt aqueous solution as a lithium-containing solution to obtain a lithium salt product, or using the lithium salt aqueous solution to perform water leaching treatment on roasted black powder that has not been water-leached; wherein S0 is the target saturation, and the value range of S0 is: 1%≤S0≤99%.

[0023] In some of the above embodiments, it is specifically defined how to process the lithium salt aqueous solution according to the saturation S of the lithium salt in the lithium salt aqueous solution and the lithium elution rate n, and the target saturation S0 is set to 1% to 99%. When S is greater than S0, it means that the saturation of the lithium salt aqueous solution meets the requirements, and the next step of purification treatment can be carried out to prepare the lithium salt product; when S≤S0 and n≤n0, it means that the saturation of the lithium salt aqueous solution does not meet the requirements, and the content of lithium carbonate in the undissolved solids is relatively high, that is, the lithium salt aqueous solution can be used as water in the water immersion treatment to repeat steps S2 and S3. 3. Leaching lithium carbonate from the undissolved solids until the saturation reaches the required level. When S≤S0 and n>n0, it indicates that the lithium content in the undissolved solids is low and no further water leaching is required. Although the saturation of the lithium salt aqueous solution has not reached the required level, there is not enough lithium carbonate in the undissolved solids to further increase the saturation. Therefore, the lithium salt aqueous solution can be purified for use in preparing lithium salt products, or the lithium salt aqueous solution can be used to water leaching the roasted black powder that has not been water-leached, i.e., the next round of roasted black powder can be water-leached.

[0024] In some embodiments, the value range of S0 is: 40%≤S0≤75%.

[0025] In the above embodiment, the range of S0 is further limited to 40% to 75%. If the target saturation is set to less than 40%, the water content in the obtained lithium salt aqueous solution is high (i.e., the corresponding lithium content is low), that is, the cost of subsequent preparation of lithium salt products will increase, and the economic efficiency will be poor; and if the target saturation is set to greater than 75%, the lithium ion content in the obtained lithium salt aqueous solution is high. Due to the common ion effect, the solubility of the lithium salt aqueous solution in lithium carbonate is reduced, thereby reducing the lithium elution rate of a single water immersion treatment and affecting the recovery efficiency; therefore, setting S0 to 40% to 75% can more effectively balance the economy and efficiency of the recovery process.

[0026] In some embodiments, in step S1, the calcination conditions include: calcination at 500-800° C. for 2-4 hours; and the mass of the reducing agent is 20%-30% of the mass of the ternary black powder.

[0027] In some of the above embodiments, under this condition, the ternary black powder can be fully reduced so that the main components of the roasted black powder are Ni, Co, MnO, lithium carbonate and some metal impurities, which is more conducive to the separation and recovery of lithium and other non-lithium metal elements, thereby improving the recovery rate of lithium elements and improving the purity of the product.

[0028] In some embodiments, the reducing agent includes at least one of elemental carbon, natural gas, carbon monoxide, and hydrogen.

[0029] In some embodiments, in step S2, the water immersion treatment comprises: immersing for 0.5 to 1.5 hours at 0 to 40° C. Under these conditions, the solubility of lithium carbonate is relatively high, and immersing at a lower temperature is beneficial to improving the immersion efficiency.

[0030] In some embodiments, in step S2, the mass of the water is 1 to 8 times the mass of the roasted black powder. In the initial water immersion treatment, too low a water dosage will affect the efficiency of the water immersion treatment, while too high a water dosage will increase the cost of subsequent lithium salt recovery from the lithium salt aqueous solution. Setting the water mass to 1 to 8 times the mass of the roasted black powder can better balance recovery cost and recovery efficiency.

[0031] In some embodiments, in step S2, the undissolved solid includes elemental Ni, elemental Co, and MnO. Elemental Ni, elemental Co, and MnO are almost insoluble in water. Therefore, by using water leaching, the nickel, cobalt, and manganese content in the saturated lithium carbonate aqueous solution can be reduced, thereby improving the purity of the lithium salt product.

[0032] In some embodiments, in step S3, the inorganic acid is sulfuric acid or hydrochloric acid. In this case, the corresponding lithium salts of the inorganic acid are lithium sulfate and lithium chloride, both of which have high solubility in water, thereby reducing water consumption and thus production costs. Furthermore, a lithium sulfate product or a lithium chloride product can be obtained as needed.

[0033] In some embodiments, in step S4, washing the undissolved solids includes returning the washing water to the water immersion treatment for recycling.

[0034] In some of the above embodiments, although the lithium content in the undissolved solid is low at this time, some residual lithium carbonate may still be dissolved in the washing water after washing with water. Therefore, the washing water is returned to the water immersion treatment for recycling. On the one hand, it can reduce the overall water consumption, and on the other hand, it is also beneficial to improve the recovery rate of the lithium element.

[0035] In some of the above embodiments, the purification process includes: subjecting the lithium salt aqueous solution to an ion exchange resin to remove impurity ions, followed by evaporation and crystallization to obtain a lithium salt product. The ion exchange resin can remove a small amount of water-soluble high-valent metal ions, such as magnesium ions and calcium ions, from the lithium salt aqueous solution, thereby further improving the purity of the lithium salt product. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A process flow chart of a method for recovering ternary black powder to prepare lithium salt provided in a specific embodiment of this application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0038] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, 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 any one or more embodiments or examples.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0040] The present application provides a method for recovering ternary black powder to prepare lithium salt, which comprises the following steps:

[0041] S1, adding a reducing agent to the ternary battery black powder and roasting it to obtain roasted black powder.

[0042] In step S2, pure water is added to the roasted black powder obtained in step S1 to perform a water immersion process to dissolve the lithium carbonate in the roasted black powder. After the immersion process is completed, filtration is performed. Filtration obtains a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solids (referred to as undissolved solids).

[0043] S3, adding inorganic acid to the saturated lithium carbonate solution obtained in S3 until the pH of the solution is 6.5-7, and completing the addition of inorganic acid to obtain a lithium salt aqueous solution.

[0044] S4, detect whether the lithium elution rate n in the Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solid obtained in S2 is greater than n0, and the value range of n0 is 97%≤n0≤99%. For example, n0 is 98%. If it is less than 98%, return to the water leaching process and continue to circulate and dissolve the lithium carbonate therein. If the lithium elution rate is greater than 98%, use pure water to countercurrent wash the obtained insoluble solid. After washing, a Ni / Co / MnO / Fe / Al / Cu solid product (delithiumized solid product) and washing water are obtained. The washing water is returned to the water leaching process for repeated use. The Ni / Co / MnO / Fe / Al / Cu solid product can be subsequently acid-dissolved, impurity-removed, and organic solvent-extracted to recover the Ni / Co / Mn therein.

[0045] Among them, the lithium elution rate

[0046] m1 is the lithium content in the undissolved solid, and m2 is the lithium content in the calcined black powder.

[0047] S5. Detect whether the saturation S of the lithium salt in the resulting lithium salt aqueous solution is greater than S0. The range of S0 is 1% ≤ S0 ≤ 99%, preferably 40% ≤ S0 ≤ 75%. For example, if S0 is 40%, if the saturation is greater than 40%, the resulting lithium salt aqueous solution is subjected to an exchange resin to remove high-valent metal impurities, followed by evaporation and crystallization to obtain a high-purity lithium salt product. If the saturation is less than 40%, the unsaturated lithium salt is returned to the water leaching process to continue the cycle of dissolving lithium carbonate. For lithium sulfate as an example, the reason for S0 ≥ 40% is that the washed lithium sulfate needs to be evaporated and crystallized to produce lithium sulfate solid after impurities removal. If the lithium sulfate saturation is too low, the evaporation and crystallization efficiency is too low, wasting energy and being uneconomical. In addition, in the subsequent lithium sulfate precipitation process, the concentration of lithium sulfate reacting with sodium carbonate is generally greater than or equal to 40%. Therefore, the saturation of the lithium salt aqueous solution is preferably greater than or equal to 40%. The reason for S0 ≤ 75% is that the lithium in the high-concentration lithium sulfate solution will produce a common ion effect, reducing the single lithium element elution rate. Therefore, S0 ≤ 75% is preferred.

[0048] The saturation of lithium salt in the lithium salt aqueous solution S=C / C0; C is the concentration of lithium salt in the lithium salt aqueous solution, in g / L, and C0 is the saturated solubility of lithium salt in water, in g / L.

[0049] As an example, taking n0 as 98% and S0 as 50%, the process flow chart of the method provided in this application is as follows: Figure 1 shown.

[0050] Furthermore, the reducing agent used in step S1 is C, NG, CO, H2, water gas, or a mixture thereof. Furthermore, the main components of the calcined black powder are Ni, Co, MnO, Li2CO3, Fe, Al, and Cu. The calcination temperature is 500-800°C and the calcination time is 2-4 hours.

[0051] Furthermore, in step S2, the mass of pure water added is 1-8 times the mass of the roasted black powder, the water immersion time is 0.5-1.5 hours, and the water immersion temperature is 0-40°C. The reason for the low water immersion temperature is that lithium carbonate has a higher solubility at low temperatures, and low-temperature water immersion is beneficial for improving the solubility of lithium carbonate. Stirring is applied during the water immersion at a stirring speed of 200-2000 r / min.

[0052] Furthermore, in step S5, the inorganic acid is hydrochloric acid or sulfuric acid, and the mass fraction of the inorganic acid is 5-98%. When the inorganic acid is hydrochloric acid, the obtained lithium salt product is lithium chloride, and when the inorganic acid is sulfuric acid, the obtained lithium salt product is lithium sulfate.

[0053] In the further above-mentioned step S5, the exchange resin is CH-93 resin, 732 cation exchange resin, etc., further, the evaporation crystallization temperature in the above step S5 is 280-350°C to remove the crystal water in the lithium salt product.

[0054] As an example, assuming n0 is 98% and S0 is 40%, the subsequent treatment of the undissolved solid in step S2 and the lithium salt aqueous solution in step S3 is shown in Table 1.

[0055] Table 1

[0056]

[0057]

[0058] The scheme of the present application is described below with reference to the following specific examples. Unless otherwise specified, the raw materials used in the following examples are all from common commercial products, and the devices or equipment used are all purchased from conventional market sales channels.

[0059] Source of ternary black powder: Black powder is obtained by dismantling, crushing, roasting and screening of waste electrolytic batteries, with a roasting temperature of 300-400℃.

[0060] Example 1 (n0 value is 98%, S0 value is 40%)

[0061] 200g of NCM ternary black powder was tested by inductively coupled plasma spectroscopy (ICP) and found to contain 6.21% lithium, or 12.42g of lithium. 40g of water gas was trickled into the ternary black powder as a reducing agent and then calcined at 700°C for 2h to obtain calcined black powder.

[0062] Add 378g of pure water to the calcined black powder to dissolve the lithium carbonate in the powder. Soak for 0.5h at 25°C with a stirring speed of 500 rpm. After immersion, filter to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solids.

[0063] The lithium content in the undissolved solid was tested to be 11.64 g, and the lithium elution rate n was 6.28% (calculation method: n = 1-11.64 / 12.42 = 6.28%), which is less than 98%. It is necessary to use the subsequent lithium salt solution to continue water leaching treatment.

[0064] 18.27 g of 30 wt % sulfuric acid was added to the saturated lithium carbonate solution to adjust the acidity and neutralize the solution to a pH of 6.8. After the acid adjustment and neutralization were completed, a lithium sulfate solution was obtained. The concentration C of lithium sulfate in the lithium sulfate solution was tested to be 15.47 g / L, and the saturated solubility C0 of lithium sulfate was approximately 348 g / L. The lithium sulfate saturation S was 4.445% (calculated as S=15.47 / 348=4.445%) after one washing. Since S was less than 40%, the lithium sulfate solution was returned to continue leaching the Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solid.

[0065] After 21 cycles of water immersion, filtration, acid adjustment, neutralization, and circulation (during the circulation process, the removal efficiency of the undissolved solids was less than 98%, and the lithium sulfate content in the lithium sulfate solution was less than 0.4 times its saturation value), the lithium content of the sampled Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solid was calculated by ICP to be 0.144 g, and the lithium elution rate n was 98.84% (calculation method: n=1-0.144 / 12.42=98.84%), which is greater than 98%. The undissolved solids were countercurrently washed 4 times with pure water, and the resulting washing liquid could be added to the water immersion process for further use.

[0066] The lithium sulfate solution obtained by acid neutralization was sampled and tested, and the concentration C of lithium sulfate in the lithium sulfate solution was 144.77 g / L. The lithium sulfate saturation S was 41.6% after washing (the calculation formula is S=144.77 / 348=41.6%), S>40%, and the content of high-valent metal impurities (Mn, Ni, Co) was 89 ppm as measured by ICP. The total mass fraction consumed during the circulation process was 289 g of 30 wt% sulfuric acid. The lithium sulfate solution was then subjected to exchange resin treatment, specifically: the obtained lithium sulfate solution was subjected to After CH-93 resin was purified by evaporation and crystallization at 300° C. for 2 h, 97.05 g of lithium sulfate with a purity of 99.6% was obtained. The calculated lithium yield was 98.2% (calculated as: 97.05×99.6%×13.88 / 109.95 / 12.42=98.2%).

[0067] Example 2 (n0 value is 98%, S0 value is 40%)

[0068] 200g of the same NCM ternary black powder as in Example 1 was taken. Inductively coupled plasma (ICP) spectroscopy revealed a lithium content of 6.21%, or 12.42g. 40g of water gas was trickled into the ternary black powder as a reducing agent, and the powder was calcined at 700°C for 2h to obtain a calcined black powder.

[0069] Add 606g of pure water to the calcined black powder to dissolve the lithium carbonate in the powder. The immersion time is 0.5h at a temperature of 25°C and a stirring speed of 500r / min. After immersion, filter to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solids.

[0070] The lithium content in the undissolved solid was tested to be 11.18 g, and the lithium elution rate n was 10% (calculation method: n=1-11.18 / 12.42=10%), which is less than 98%. It is necessary to use the subsequent lithium salt solution to continue water leaching treatment.

[0071] 29.23 g of 30 wt % sulfuric acid was added to the saturated lithium carbonate solution to adjust the acidity and neutralize the solution to a pH of 6.9. After the acid adjustment and neutralization were completed, a lithium sulfate solution was obtained. The concentration C of lithium sulfate in the lithium sulfate solution was tested to be 15.65 g / L, and the saturated solubility C0 of lithium sulfate was approximately 348 g / L. The lithium sulfate saturation S was 4.498% (calculated as S=15.65 / 348=4.497%) after one washing. Since S was less than 40%, the lithium sulfate solution was returned to continue leaching the Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solid.

[0072] After 13 cycles of water immersion, filtration, acid adjustment and neutralization (during the cycle, the removal efficiency of the undissolved solids was less than 98%, and the lithium sulfate content in the lithium sulfate solution was less than 0.4 times its saturation value), the lithium content of the sampled Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solid was measured by ICP to be 0.128 g, and the lithium elution rate n was 98.97% (calculation method: n = 1-0.128 / 12.42 = 98.97%), which is greater than 98%. The undissolved solids were countercurrently washed four times with pure water, and the resulting washing liquid could be added to the water immersion process for further use.

[0073] The lithium sulfate solution obtained by acid neutralization was sampled and tested, and the concentration of lithium sulfate in the lithium sulfate solution was C, which was 108.95 g / L. The lithium sulfate saturation S was 31.31% after washing (the calculation formula was S=108.95 / 348=31.31%), S<40%, and the content of high-valent metal impurities (Mn, Ni, Co) was 93 ppm as measured by ICP. The total mass fraction consumed during the circulation process was 289 g of 30 wt% sulfuric acid. The lithium sulfate solution was then subjected to exchange resin treatment, specifically: the obtained lithium sulfate solution was subjected to After CH-93 resin was purified by evaporation and crystallization at 300° C. for 2.5 h, 97.11 g of lithium sulfate with a purity of 99.63% was obtained. The calculated lithium yield was 98.3% (calculated as: 97.11×99.63%×13.88 / 109.95 / 12.42=98.3%).

[0074] Compared with Example 1, Example 2 has a similar lithium elution rate and lithium yield. However, the amount of water required to evaporate 1g of lithium sulfate in Example 1 is 6.91mL (calculated as 1000 / 144.77=6.91), while the amount of water required to evaporate 1g of lithium sulfate in Example 2 is 9.18mL (calculated as 1000 / 108.95=9.18). The amount of water evaporated to obtain 1g of lithium sulfate in Example 2 is 32.9% higher than that in Example 1. Therefore, it is necessary to appropriately increase the concentration of the lithium sulfate solution obtained by washing (by continuing to return to the water immersion treatment, or reducing the water consumption of the first water immersion treatment, or increasing the number of washings) to increase the evaporation efficiency.

[0075] Example 3 (n0 value is 98%, S0 value is 40%)

[0076] 200g of NCM ternary black powder was tested by inductively coupled plasma (ICP) spectroscopy and found to contain 3.5% lithium, or 7g of lithium. 40g of water gas was trickled into the ternary black powder as a reducing agent and then calcined at 700°C for 2h to obtain calcined black powder.

[0077] Add 383g of pure water to the calcined black powder to dissolve the lithium carbonate in the powder. The immersion time is 0.5h at a temperature of 25°C and a stirring speed of 500r / min. After immersion, filter to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solids.

[0078] The lithium content in the undissolved solid was tested to be 6.24 g, and the lithium elution rate n was 10.86% (calculation method: n=1-6.24 / 7=10.86%), which is less than 98%. It is necessary to use the subsequent lithium salt solution to continue water leaching treatment.

[0079] 17.94 g of 30 wt % sulfuric acid was added to the saturated lithium carbonate solution to adjust the acidity and neutralize the solution to a pH of 6.8. After the acid adjustment and neutralization were completed, a lithium sulfate solution was obtained. The concentration C of lithium sulfate in the lithium sulfate solution was tested to be 15.35 g / L, and the saturated solubility C0 of lithium sulfate was approximately 348 g / L. The lithium sulfate saturation S was 4.41% (calculated as S=15.35 / 348=4.41%) after one washing. S1 was less than 40%, so the lithium sulfate solution was returned to continue leaching the Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solid.

[0080] After 12 cycles of water immersion, filtration, acid adjustment and neutralization (during the cycle, the removal efficiency of undissolved solids was less than 98%, and the lithium sulfate content in the lithium sulfate solution was less than 0.4 times its saturation value), the lithium content of the sampled Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solid was measured by ICP to be 0.105 g, and the lithium elution rate n was 98.5% (calculation method: n=1-0.105 / 7=98.5%), which is greater than 98%. The undissolved solids were countercurrently washed 4 times with pure water, and the resulting washing liquid could be added to the water immersion process for further use.

[0081] The lithium sulfate solution obtained by acid neutralization was sampled and tested, and the concentration C of lithium sulfate in the lithium sulfate solution was 101.22 g / L. The lithium sulfate saturation S was 29.09% after washing (the calculation formula was S=101.22 / 348=29.09%), S<40%, and the content of high-valent metal impurities (Mn, Ni, Co) was 87 ppm as measured by ICP. The total mass fraction consumed during the circulation process was 162.2 g of 30 wt% sulfuric acid. The lithium sulfate solution was then subjected to exchange resin treatment, specifically: the obtained lithium sulfate solution was subjected to After CH-93 resin was purified by evaporation and crystallization at 300° C. for 2 h, 54.49 g of lithium sulfate with a purity of 99.63% was obtained. The calculated lithium yield was 97.9% (calculated as: 54.49×99.63%×13.88 / 109.95 / 7=97.9%).

[0082] Compared with Example 1, the use of ternary black powder with low lithium content does not affect the lithium elution rate and lithium yield, indicating that this method is also suitable for processing ternary black powder with low lithium content.

[0083] Example 4

[0084] 200g of the same NCM ternary black powder as in Example 2 was taken. Inductively coupled plasma (ICP) spectroscopy revealed a lithium content of 6.21%, or 12.42g. 40g of water gas was trickled into the ternary black powder as a reducing agent, and the powder was calcined at 700°C for 2h to obtain a calcined black powder.

[0085] 606 g of a 261 g / L lithium sulfate solution (75% saturation) was added to the calcined black powder. The lithium carbonate in the powder was dissolved by leaching for 0.5 h at a temperature of 25°C (500 rpm). After leaching, the solution was filtered to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solids.

[0086] The lithium content in the undissolved solid was tested to be 11.92 g, and the lithium elution rate n was 4.0% (calculation method: n=1-11.92 / 12.42=4%), which is less than 98%. It is necessary to use the subsequent lithium salt solution to continue water leaching treatment.

[0087] It is shown that the lithium removal efficiency of a single immersion treatment using a lithium sulfate aqueous solution with a saturation of 75% is 4%.

[0088] Example 5

[0089] 200g of the same NCM ternary black powder as in Example 2 was taken. Inductively coupled plasma (ICP) spectroscopy revealed a lithium content of 6.21%, or 12.42g. 40g of water gas was trickled into the ternary black powder as a reducing agent, and the powder was calcined at 700°C for 2h to obtain a calcined black powder.

[0090] 606 g of a 295 g / L lithium sulfate solution (85% saturation) was added to the calcined black powder. The lithium carbonate in the powder was dissolved by immersion in water for 0.5 h at a temperature of 25°C (500 rpm). After immersion, the solution was filtered to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solids.

[0091] The lithium content in the undissolved solid was tested to be 12.04 g, and the lithium elution rate n was 3.06% (calculation method: n = 1-12.04 / 12.42 = 3.06%), which is less than 98%. It is necessary to use the subsequent lithium salt solution to continue water leaching treatment.

[0092] It is shown that the lithium removal efficiency of a single immersion treatment using a lithium sulfate aqueous solution with a saturation of 85% is 3.06%.

[0093] In Example 2, compared with Example 4 and Example 5, the lithium sulfate saturation in the initial washing solution of the same mass of washing solution increased from 0 to 75% and 85%, and the lithium elution rate decreased from 10% to 4% and 3.06%, respectively. The decrease in elution rate will increase the number of elutions, so an appropriate target saturation S0 can be selected to improve the lithium elution efficiency.

[0094] Comparative Example 1

[0095] 200g of the same NCM ternary black powder as in Example 1 was taken. Inductively coupled plasma (ICP) spectroscopy revealed a lithium content of 6.21%, or 12.42g. 40g of water gas was trickled into the ternary black powder as a reducing agent, and the powder was calcined at 700°C for 2h to obtain a calcined black powder.

[0096] 378 g of pure water and 289 g of 30% sulfuric acid (the same total acid content as in Example 1) were added to the roasted black powder to extract and dissolve the lithium carbonate in the roasted black powder. The immersion time was 0.5 h, the immersion temperature was 25° C., and the stirring speed during the immersion process was 500 r / min. After the immersion was completed, the solution containing lithium sulfate and lithium carbonate and undissolved Ni / Co / MnO / Li2CO3 / Fe / Al / Cu solids were filtered.

[0097] The lithium content in the undissolved solid was tested to be 7.32 g, and the lithium washing efficiency was 41.1% (calculation method: 1-7.32 / 12.42=41.1%).

[0098] The washed product was evaporated and crystallized at 300° C. for 3 h to obtain 105.91 g of lithium sulfate with a purity of 25.64%, of which manganese sulfate accounted for 48.3%.

[0099] Compared with the examples, in Comparative Example 1, the direct addition of high-concentration sulfuric acid for washing caused a large amount of reaction between the basic manganese oxide in the calcined powder and the sulfuric acid. That is, part of the sulfuric acid reacted with the manganese oxide and part of the sulfuric acid reacted with the lithium carbonate, which significantly reduced the lithium elution rate, increased manganese dissolution, and reduced the purity of the obtained lithium salt.

[0100] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for recovering ternary black powder to prepare lithium salt, characterized in that: The following steps are involved: Step S1: adding a reducing agent to the ternary black powder for reduction roasting, so as to reduce the high-valent non-lithium active metal elements in the ternary black powder to low-valent non-lithium active metal elements to obtain roasted black powder, wherein the roasted black powder also includes lithium carbonate; Wherein, the non-lithium active metal elements include nickel, cobalt and manganese; Step S2: adding water to the roasted black powder for water immersion treatment, so that the lithium carbonate in the roasted black powder is dissolved in the water to saturation, and filtering to obtain a saturated lithium carbonate aqueous solution and undissolved solids; Step S3: adding an inorganic acid to the saturated lithium carbonate aqueous solution until the pH is 6.5-7, so as to convert the lithium carbonate into a lithium salt corresponding to the inorganic acid, thereby obtaining a lithium salt aqueous solution; Step S4: obtaining the lithium elution rate n of step S2, and determining whether to perform washing treatment on the undissolved solids or to continue to perform water immersion treatment on the undissolved solids according to the lithium elution rate n; Among them, the lithium elution rate ; m1 is the lithium content in the undissolved solid, in g; m2 is the lithium content in the calcined black powder, in g; Step S4 comprises: if the lithium elution rate n of step S2 satisfies n>n0, washing the insoluble solid to obtain a delithiation solid product; If the lithium elution rate n in step S2 satisfies n≤n0, the undissolved solid is used as the roasted black powder in step S2 and the water leaching treatment is repeated in step S2 until the lithium elution rate n>n0, where n0 is the target lithium elution rate; Step S5: obtaining the saturation S of lithium salt in the lithium salt aqueous solution in step S3, and determining, based on the saturation S and the lithium elution rate n, whether the lithium salt aqueous solution is to be purified or whether the lithium salt aqueous solution is to be used as the water for water leaching in step S2; Among them, the saturation of lithium salt in lithium salt aqueous solution S=C / C0; C is the concentration of lithium salt in the lithium salt aqueous solution, in g / L, and C0 is the saturated solubility of lithium salt in water, in g / L; Step S5 includes: if the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S>S0, purifying the lithium salt aqueous solution as a lithium-containing solution to obtain a lithium salt product; If the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S≤S0, and the lithium elution rate n≤n0, it is determined that the lithium salt aqueous solution is to be treated A. The process A comprises: using the lithium salt aqueous solution as the water in step S2, repeating steps S2 and S3 until the saturation S is greater than S0; If the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S≤S0, and the lithium elution rate n>n0, it is determined that the lithium salt aqueous solution is to be treated B, The process B includes: purifying the lithium salt aqueous solution as a lithium-containing solution to obtain a lithium salt product, or using the lithium salt aqueous solution to perform water leaching on roasted black powder that has not been water-leached; S0 is the target saturation.

2. The method according to claim 1, characterized in that The value range of n0 is: 97%≤n0≤99%.

3. The method according to claim 2, characterized in that The value range of S0 is: 1%≤S0≤99%.

4. The method according to claim 3, characterized in that The value range of S0 is: 40%≤S0≤75%.

5. The method according to claim 1, wherein In step S1, the calcination conditions include: calcination at 500-800° C. for 2-4 hours; and the mass of the reducing agent is 20%-30% of the mass of the ternary black powder.

6. The method according to claim 1, characterized in that In the step S2, the conditions of the water immersion treatment include: immersing in water at 0-40° C. for 0.5-1.5 hours; and / or, in the step S2, the mass of the water is 1-8 times the mass of the roasted black powder.

7. The method according to claim 1, characterized in that In the step S2, the undissolved solid includes Ni element, Co element, and MnO.

8. The method according to claim 1, characterized in that In step S3, the inorganic acid is sulfuric acid or hydrochloric acid.

9. The method according to claim 1, characterized in that In the step S4, washing the undissolved solids includes returning the washing water to the water immersion process for recycling.

10. The method according to claim 1, characterized in that The purification process includes: performing impurity removal treatment on the lithium salt aqueous solution using an ion exchange resin to remove impurity ions, and then performing evaporation and crystallization treatment to obtain a lithium salt product.

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