Method for recycling ternary lithium battery based on front impurity removal

Abstract

The invention provides a method for recycling a ternary lithium battery based on preposed impurity removal. The method comprises the following steps: S1, discharging and disassembling the ternary lithium battery, performing first roasting treatment in a protective gas atmosphere, crushing, and screening to obtain a current collector material, a negative electrode active material and primary black powder; s2, the primary black powder is added into water to be subjected to flotation carbon removal treatment, and carbon-removed primary black powder is obtained through drying; s3, carrying out second roasting treatment on the carbon-removed primary black powder in an oxygen-containing atmosphere to obtain roasted black powder; and S4, the roasted black powder is added into acid liquor to be subjected to acid leaching treatment, and acid leaching liquor and impurity-removed ternary black powder are obtained. The impurity removal rate of the impurity-removed ternary black powder obtained through the method can reach 98% or above, and therefore the influence of impurity elements on metal elements in the recycled ternary black powder is reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of ternary battery recycling, and specifically relates to a method for recycling ternary lithium batteries based on pre-impurity removal. Background Art

[0002] With increasing public concern about the energy crisis and environmental pollution, the new energy industry has experienced rapid growth. Lithium-ion batteries, as key energy storage devices in the new energy industry, play a vital role in electrochemical energy storage and new energy vehicles, with sales increasing annually. However, during cycling, lithium batteries can experience structural failure due to particle breakage / irreversible phase transitions of the positive electrode material, excessive growth / decomposition of the SEI on the negative electrode surface, lithium deposition on the negative electrode surface, decomposition and gassing of the electrolyte, increased trace impurities in the system, and current collector corrosion leading to active material stripping. These phenomena lead to significant capacity degradation after long-term cycling, ultimately leading to the end of life. Decommissioned batteries contain significant amounts of heavy metals and organic matter. Direct landfilling can cause significant environmental pollution. Furthermore, decommissioned batteries contain significant amounts of recyclable resources such as cobalt, nickel, manganese, copper, iron, aluminum, and carbon, resulting in a significant waste of resources. Compared to traditional smelting of non-ferrous metals from ores, the development and utilization of non-ferrous metal resources from decommissioned batteries can reduce energy consumption by 80-90% and production costs by 60-80%. Driven by resource and environmental protection and economic benefits, the retired battery recycling industry has flourished in recent years. However, there are still some technical issues in lithium battery recycling that need to be addressed.

[0003] Ternary lithium battery recycling is primarily divided into wet and pyrometallurgical processes. The wet process typically involves discharging the battery, disassembling it, roasting it, pulverizing it, and screening it to produce ternary black powder. A reducing agent and acid are then added to dissolve the ternary black powder. Iron is then added to remove copper, pH is adjusted to remove iron and aluminum, manganese is extracted with a P204 extractant, nickel and cobalt are separated and recovered with P507, and the raffinate is added with sodium carbonate to recover lithium carbonate. This process removes impurities such as aluminum, iron, and copper after the ternary black powder is dissolved. However, during the precipitation and filtration process, these impurities can carry over a significant amount of dissolved nickel, cobalt, manganese, and lithium, resulting in valuable metal loss and reduced yield. The pyrometallurgical process typically involves discharging the battery, disassembling it, roasting it, pulverizing it, and screening it to produce ternary black powder. The ternary black powder is then added with a reducing agent and roasted at high temperature to produce nickel, cobalt, and manganese oxides. Nickel, cobalt, and manganese are then recovered through electrolytic refining. During the electrolytic refining process, impurities such as copper, aluminum, and iron can precipitate at the cathode, reducing the purity of the resulting nickel-cobalt alloy. Therefore, finding a process to remove impurity ions in ternary materials before acid leaching and dissolution of the ternary materials in the wet process and before reduction roasting in the fire process is an urgent problem to be solved in the ternary lithium battery recycling industry. Summary of the Invention

[0004] In view of this, the present application provides a method for recycling ternary lithium batteries based on pre-impurity removal. This method can obtain impurity-removed ternary black powder with a low impurity element content through pre-impurity removal, thereby reducing the impact of impurity elements on the recovery of metal elements in the ternary black powder, and the loss of nickel, cobalt, manganese and lithium elements in the ternary black powder is small, and the recovery rate is high.

[0005] In a first aspect, the present application provides a method for recycling ternary lithium batteries based on pre-impurity removal, comprising the following steps:

[0006] Step S1: disassembling the ternary lithium battery after discharge and performing a first calcination treatment under a protective atmosphere, crushing and screening to obtain current collector material, negative electrode active material and primary black powder;

[0007] Step S2: adding the primary black powder into water for flotation decarbonization, and drying to obtain the decarbonized primary black powder;

[0008] Step S3: performing a second calcination treatment on the carbon-removed primary black powder in an oxygen-containing atmosphere to oxidize the copper in the carbon-removed primary black powder into copper oxide to obtain calcined black powder;

[0009] Step S4: adding the roasted black powder to an acid solution for acid leaching, so that the non-lithium substances (i.e., impurities) in the roasted black powder react with the acid solution to dissolve, thereby obtaining an acid leaching solution and impurity-removed ternary black powder; wherein the acid leaching solution includes Li + 、Fe 2+ 、Fe 3+ 、Al 3+ 、Cu 2+ , Ca 2+ or Mg 2+ At least one of .

[0010] Based on the present application, the method uses protective gas to protect the roasting after the ternary battery is disassembled, and then removes most of the copper / iron / aluminum / carbon through crushing and screening, and then performs deep carbon removal by flotation. The carbon removal black powder is roasted again in an oxygen-containing atmosphere to oxidize the copper in the carbon removal black powder impurities into copper oxide that is easily soluble in dilute acid, and then the iron / aluminum / copper oxide is dissolved by acid leaching to obtain the impurity-removed ternary black powder. The impurity removal rate of the impurity-removed ternary black powder obtained by this method can reach more than 98%, wherein the Al element content can be reduced to below 20 ppm, and the Fe element and Cu element can be reduced to below 10 ppm, thereby reducing the influence of impurity elements on the recovery of metal elements in the ternary black powder, and the loss of valuable elements (such as nickel, cobalt, manganese, lithium) in the ternary black powder is small, and the recovery rate is high.

[0011] Specifically, in step S1, the ternary lithium battery is subjected to a first calcination treatment under a protective gas atmosphere, the purpose of which is to remove the volatile electrolyte in the ternary lithium battery and the binder in the positive and negative electrode sheets, separate the active material layer in the electrode sheet from the current collector, and disperse the components in the active material layer. This process is carried out under a protective gas atmosphere to prevent the carbon element as the negative electrode active material from reacting with oxygen to generate carbon monoxide during the process, thereby preventing carbon monoxide from reducing the ternary lithium material as the positive electrode active material to a low-valent oxide that is easily acid-soluble, thereby reducing the loss of the ternary lithium material in the subsequent processing process and effectively improving the recovery rate of valuable metal elements (nickel, cobalt, manganese and lithium elements) in the ternary lithium material; after calcination, the calcined product is crushed to fully separate the components in the ternary lithium battery, mainly copper foil, aluminum foil, negative electrode active material and positive electrode active material. By utilizing the differences in particle size, density, etc. of the above materials, more than 98% of the copper foil, aluminum foil and more than 60% of the negative electrode active material can be separated from the ternary lithium material, so that the main material in the obtained primary black powder is the ternary lithium material;

[0012] In step S2, although some negative electrode active materials have been screened in step S1, some negative electrode active materials are still mixed in the primary black powder. Graphite, as a negative electrode active material, has a low density, and the carbon in the primary black powder can be directly removed by flotation. The carbon with a low density will float to the upper layer and be removed, thereby obtaining a decarbonized primary black powder. At the same time, the decarbonization treatment can reduce the damage to the ternary lithium material in the subsequent second calcination treatment in an oxygen-containing atmosphere.

[0013] In step S3, the decarbonized primary black powder is subjected to a second roasting treatment in an oxygen-containing atmosphere. Since the decarbonized primary black powder contains some copper, which is insoluble in acid solution, the acid leaching treatment cannot separate the copper from the ternary lithium material. The second roasting treatment is carried out in an oxygen-containing atmosphere. During this process, the copper can be oxidized into acid-soluble copper oxide, so that the copper element can be separated from the ternary lithium material through subsequent acid leaching treatment.

[0014] In step S4, the roasted black powder is subjected to acid leaching treatment. Most of the impurity oxides (such as CuO, etc.), impurity elements (such as Fe, Al, etc.), and impurity salts (such as MgCO3, etc.) in the roasted black powder are dissolved during the acid leaching process. The ternary lithium material (mainly lithium transition metal composite oxide LiMeO2, Me includes at least one of Ni, Co or Mn) is insoluble in the acid solution, so that most of the impurity metal elements in the roasted black powder are fixed to the acid leaching solution and separated from the ternary lithium material. The content of impurity metal elements in the obtained de-impurified ternary black powder is low, thereby reducing the influence of impurity elements on the subsequent recovery of metal elements in the ternary black powder. At the same time, since the ternary lithium material is insoluble in the acid solution, the recovery rate of each element in the ternary lithium material is high.

[0015] The non-lithium substance includes at least one of a non-lithium elemental substance, a non-lithium oxide, and a non-lithium salt, namely, an impurity elemental substance, an impurity oxide, and an impurity salt.

[0016] In some embodiments, in step S1, the conditions of the first calcination treatment include: heating to 300-400° C. at a heating rate of 2-10° C. / min, and calcining at this temperature for 0.5-3.5 h.

[0017] The temperature of the first calcination treatment is selected from any value of 300°C, 320°C, 340°C, 350°C, 360°C, 380°C, and 400°C, or a range formed by any two values; the time of the first calcination treatment is selected from any value of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, and 3.5h, or a range formed by any two values.

[0018] In some of the above embodiments, under these conditions, the electrolyte in the ternary lithium battery can be fully volatilized and the binder in the positive and negative electrode sheets can be fully decomposed, so that the components in the ternary lithium battery can be fully separated, which is beneficial for the components after crushing to fully react in the second roasting treatment and acid leaching treatment, and is beneficial for the removal of impurity metal elements.

[0019] In some embodiments, in step S1, the protective atmosphere is nitrogen and / or argon.

[0020] In some embodiments, in step S1, the particle size of the primary black powder obtained after crushing and screening is less than 0.6 mm. Based on the above embodiment, the reaction speed of each step can be accelerated and the recovery efficiency can be improved.

[0021] In some embodiments, the primary black powder includes lithium transition metal composite oxide (LiMeO2), C element, Cu element, Al element, Fe element, Mg element and Ca element. Based on the above embodiment, the lithium element and transition metal element (at least one of Ni, Co or Mn) are derived from the ternary lithium material as the positive electrode active material, the C element is derived from the graphite of the negative electrode active material, the Al element and Cu element are mainly derived from the current collector, the Fe element is mainly derived from the shell, and the Mg element and Ca element are derived from the decomposition products of some components in the ternary lithium battery. Therefore, it is necessary to separate the lithium transition metal composite oxide from other impurity components in the primary black powder to reduce the impurity content in the ternary black powder.

[0022] In some embodiments, in step S2, the flotation decarbonization treatment conditions include: a solid-liquid ratio of primary black powder to water of (80-200):1 g / L, stirring at 100-300 rpm for 5-30 minutes, standing for 5-30 minutes, and filtering out the floating carbon element on the upper layer; repeating the stirring, standing, and filtering operations 2-6 times. Based on the above embodiment, through multiple flotation, the density difference between the carbon element and other components can be utilized to separate them to obtain a decarbonized primary black powder, thereby reducing the damage of the carbon element to the structure of the ternary lithium material during the subsequent aerobic roasting process.

[0023] In some embodiments, in step S3, the volume fraction of oxygen in the oxygen-containing atmosphere is greater than or equal to 60%. Based on the above embodiment, under such conditions, the oxidation efficiency of the copper element can be improved, so that the copper element in the primary carbon removal black powder can be more quickly and fully oxidized into acid-soluble copper oxide, thereby making it easier to reduce the copper content in the black powder through acid leaching.

[0024] The volume fraction of oxygen in the oxygen-containing atmosphere is selected from any one of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%, or a range formed by any two of the values.

[0025] In some embodiments, in step S3, the second calcination treatment comprises calcining at 400-500° C. for 0.5-2 hours. Based on the above embodiment, under these conditions, the copper element can fully react with oxygen to form acid-soluble copper oxide, making it easier to reduce the copper content in the black powder through acid leaching.

[0026] The temperature of the second calcination treatment is selected from any value of 400°C, 420°C, 440°C, 450°C, 460°C, 480°C, and 500°C, or a range formed by any two values; the time of the second calcination treatment is selected from any value of 0.5h, 1h, 1.5h, and 2h, or a range formed by any two values.

[0027] In some embodiments, in step S4, the conditions for the acid leaching treatment include: a solid-liquid ratio of the roasted black powder to the acid solution of (120-180):1 g / L, acid leaching at 20-80° C. for 0.5-2 hours, and controlling the pH of the system to be 1-1.6 during the acid leaching process. Based on the above embodiment, under these conditions, the acid-soluble components in the roasted black powder, such as most impurity metal oxides (such as CuO, etc.), impurity metal elements (Fe, Al), and impurity metal salts (such as MgCO3, etc.), will be fully dissolved in the acid solution, thereby being separated from the ternary lithium material.

[0028] In the acid leaching treatment, the solid-liquid ratio of the roasted black powder to the acid solution is selected from any one of 120:1g / L, 130:1g / L, 140:1g / L, 150:1g / L, 160:1g / L, 170:1g / L, and 180:1g / L, or a range formed by any two values; the acid leaching temperature is selected from any one of 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, and 80°C, or a range formed by any two values; the acid leaching time is selected from any one of 0.5h, 1h, 1.5h, and 2h, or a range formed by any two values; and the pH of the system is controlled to be any one of 1, 1.2, 1.4, and 1.6, or a range formed by any two values ​​during the acid leaching process.

[0029] It should be noted that during the acid leaching process, as the reaction proceeds, the pH value of the system will gradually increase. Therefore, the pH of the system can be maintained at 1 to 1.6 by adding acid to allow the acid-soluble components in the roasted black powder to fully react and dissolve.

[0030] In some embodiments, in step S4, after the acid leaching, the further steps include: filtering the acid leaching solution and the calcined black powder after the acid leaching; washing the calcined black powder after the acid leaching with an acid solution, and drying the calcined black powder to obtain the impurity-removed ternary black powder. Based on the above embodiment, the surface of the calcined black powder after the acid leaching may still have some impurity metal ions adsorbed on it. Further washing with an acid solution can elute the impurity metal ions on the black powder surface, further reducing the impurity content of the impurity-removed ternary black powder.

[0031] In some embodiments, the pH of the acid solution during the washing process is 1 to 1.6, and the acid wash solution obtained from the washing process is used for the acid leaching process. Based on the above embodiment, the use of an acid solution with a pH of 1 to 1.6 for washing is more effective. Furthermore, since the pH of the acid wash solution after washing changes little and the acid wash solution still contains eluted impurity metal elements and lithium, using it for acid leaching can save costs and allow the impurity metal elements and lithium to be recycled.

[0032] In some embodiments, in step S4, the drying conditions include: drying at 120-350° C. for 1-3 hours.

[0033] In some embodiments, further comprising:

[0034] Step S5: adding an oxidant to the acid leaching solution to make Fe 2+ Oxidized to Fe 3+ , obtaining an oxidizing acid leaching solution;

[0035] Step S6: Adding a primary alkali solution to the oxidizing acid leaching solution to adjust the pH of the solution for precipitation treatment, so that the Fe 3+ and Al 3+Precipitation to obtain iron-aluminum slag and iron-aluminum-removed filtrate;

[0036] Step S7: Adding secondary alkali solution to the de-iron and de-aluminum filtrate to adjust the pH of the solution for precipitation treatment, so that the Cu 2+ , and the remaining Fe 3+ and Al 3+ Precipitation to obtain copper, iron and aluminum slag and copper, iron and aluminum removed filtrate;

[0037] Step S8: Pass the iron-aluminum-copper filtrate through an ion exchange resin to make Ca 2+ and Mg 2+ Remove to obtain purified liquid;

[0038] Step S9: adding a tertiary alkali solution to the purified liquid to perform a lithium precipitation reaction to obtain a lithium carbonate product;

[0039] Wherein, the tertiary alkali solution includes sodium carbonate solution and / or potassium carbonate solution.

[0040] In some of the above embodiments, since there is still some lithium element in the form of lithium carbonate in the ternary lithium battery, the acid dissolves in the acid leaching solution in the form of, for example, lithium sulfate during the acid leaching process. The impurity metal elements in the acid leaching solution can be removed through the above steps, and then a lithium carbonate product with a higher purity can be prepared by adding carbonate.

[0041] Specifically, ferrous ions are oxidized to ferric ions with a lower precipitation pH value by using an oxidant. Since the hydroxide Ksp corresponding to ferric ions and aluminum ions are both low, the Fe in the acid leaching solution can be simultaneously oxidized by adding a primary alkali solution. 3+ and Al 3+ Precipitation is performed to obtain an iron-aluminum slag with ferroaluminum sulfate as the main component. Of course, the iron-aluminum slag can also contain iron hydroxide and aluminum hydroxide; by adding a secondary alkali solution, the pH of the system is further increased, and the Cu in the system is 2+ and the Fe that was not completely precipitated in the previous step 3+ and Al 3+ After sufficient precipitation, copper-iron-aluminum slag containing copper hydroxide as the main component and a small amount of iron hydroxide and aluminum hydroxide is obtained; the iron-aluminum-copper filtrate is then passed through an ion exchange resin to remove high-valent metal ions (such as Ca 2+ and Mg 2+ ) is removed by ion exchange, so that the impurity metal element content in the purified liquid is low, and the lithium ions are precipitated in the form of lithium carbonate by adding tertiary alkali solution to supplement carbonate ions, thereby obtaining a lithium carbonate product with higher purity.

[0042] In some embodiments, in step S5, the oxidant is hydrogen peroxide, and the molar amount of the oxidant is 1 to 3 times the molar amount of the iron element in the acid leaching solution. Based on the above embodiment, a suitable excess of the oxidant can fully convert the iron element present in the form of ferrous ions into ferric ions. At the same time, using hydrogen peroxide as the oxidant can reduce the introduction of impurity ions.

[0043] In some embodiments, the primary alkali solution includes at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a sodium carbonate aqueous solution, and a potassium carbonate aqueous solution, and the precipitation treatment conditions include: precipitation for 0.5 to 2 hours at a pH of 3.8 to 4.3. Based on the above embodiment, under the above conditions, the Fe 3+ and Al 3+ When the precipitation treatment is carried out using a primary alkali solution, the pH value is selected from any one of 3.8, 3.9, 4.0, 4.1, 4.2, and 4.3, or a range formed by any two of the values.

[0044] In some embodiments, in step S7, the secondary alkali solution includes at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a sodium carbonate aqueous solution, and a potassium carbonate aqueous solution, and the precipitation treatment conditions include: precipitation for 0.5 to 2 hours at a pH of 6.5 to 7. Based on the above embodiment, under the above conditions, the Cu in the system 2+ It will react with hydroxide to precipitate copper hydroxide, and the Fe 3+ and Al 3+ When the secondary alkali solution is used for precipitation treatment, the pH value is selected from any one of 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0, or a range formed by any two of the values.

[0045] In some embodiments, in step S9, the conditions for the lithium precipitation reaction include: the molar amount of carbonate in the tertiary alkali solution is Li + 0.5 to 0.75 times the molar amount; sink lithium at 60 to 98 ° C for 0.2 to 3 hours. Based on the above embodiment, under the above conditions, the Li + The precipitation is fully converted into lithium carbonate.

[0046] In some embodiments, both the primary alkali solution and the secondary alkali solution are near-saturated solutions. Near-saturated solutions refer to alkali solutions with a saturated concentration of C0, and a concentration of C1 that satisfies the following: 0.9C0≤C1≤C0. Under these conditions, water introduction can be reduced, thereby reducing subsequent recycling costs.

[0047] In some embodiments, the ion exchange resin may be At least one of resin and 732 cation exchange resin.

[0048] In some embodiments, in step S9, before the lithium precipitation reaction, the purified liquid is concentrated, and the lithium ion concentration in the purified liquid after concentration is 20 to 30 g / L. + It mainly comes from the lithium element in the negative electrode of the ternary lithium battery, so the lithium ion concentration in the purified liquid is low. After concentration treatment, the lithium ions in the purified liquid are easier to precipitate, and less tertiary alkaline solution is consumed.

[0049] In some embodiments, in step S9, before the lithium precipitation reaction, acid is added to the purified liquid to adjust the pH to 1 to 1.6, and the purified liquid after pH adjustment is used for acid leaching and / or washing in step S4 to enrich the lithium ions in the purified liquid to a concentration of 20 to 30 g / L. Based on the above embodiment, since the lithium ion concentration in the purified liquid is low, and heating and evaporation concentration will increase the recovery cost, by adding acid to adjust the pH to 1 to 1.6 and using it for acid leaching and / or washing in step S4, lithium elements in different batches of ternary lithium batteries can be collected through multiple acid leaching and washing, thereby enriching the lithium ions in the purified liquid, which can effectively reduce the recovery cost.

[0050] Compared with the prior art, the present invention has the following advantages:

[0051] (1) The present application uses protective gas to protect the calcination process after the ternary battery is disassembled, and then removes most of the copper / iron / aluminum / carbon through crushing and screening, and then removes carbon through flotation. The carbon removal black powder is secondary roasted under oxygen-rich conditions to oxidize the copper in the carbon removal black powder impurities into copper oxide that is easily soluble in dilute acid, and then the iron, aluminum, copper, calcium, magnesium, etc. are dissolved through dilute acid leaching. The black powder after acid leaching is washed in dilute acid countercurrent and dried to obtain the impurity-removed ternary black powder. The impurity removal rate of the obtained impurity-removed black powder can reach more than 98%;

[0052] (2) The acid leaching solution is precipitated with alkali in a step-by-step manner to precipitate iron / aluminum / copper, and then calcium and magnesium are removed by exchange resin to obtain a high-purity lithium carbonate product, the purity of which can reach more than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a process flow chart for recycling ternary lithium batteries based on pre-impurity removal according to one embodiment of the present application. DETAILED DESCRIPTION

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The main purpose of this application is to provide a method for recycling ternary lithium batteries based on pre-impurity removal, aiming to solve the problems existing in the existing technical solutions.

[0058] To achieve the above objectives, the present application provides a method for recycling ternary lithium batteries based on pre-impurity removal, which comprises the following steps:

[0059] S1, after discharging and disassembling the ternary battery, it is roasted once in a protective gas atmosphere to remove the volatile electrolyte and destroy the binder in the decomposition active material. After the roasting is completed, the primary black powder is obtained after crushing and screening to remove most of the copper / iron / aluminum / carbon.

[0060] S2, adding deionized water to the primary black powder obtained in S1 for deep carbon removal by flotation;

[0061] S3, after flotation and carbon removal, drying and secondary roasting under oxygen-rich conditions to oxidize the copper in the impurities into copper oxide that is easily soluble in dilute acid. After the secondary roasting is completed, roasted black powder is obtained.

[0062] In step S4, the roasted black powder obtained in step S3 is mixed with dilute acid for acid leaching. During the acid leaching process, calcium and magnesium impurities, iron, aluminum, copper oxide, and some lithium ions dissolve into the dilute acid solution. Upon completion of the acid leaching process, the acid-leached black powder and the acid leaching solution are obtained. The acid-leached black powder is then washed with dilute acid in countercurrent flow and dried to obtain the impurity-free ternary black powder. The washing solution is then returned to the dilute acid leaching process for recycling.

[0063] S5, adding an oxidant to the acid leaching solution obtained in S4 to oxidize the divalent iron with a high precipitation pH value in the solution into trivalent iron with a low precipitation pH value.

[0064] S6, after the oxidation is completed, add the first-level alkali solution to precipitate the iron and aluminum. After the precipitation is completed, the iron-aluminum slag and the iron-aluminum-removed filtrate are obtained by filtration. The iron-aluminum slag can be used for further iron and aluminum recovery.

[0065] S7, adding secondary alkaline solution to the iron and aluminum removal filtrate to precipitate iron hydroxide / aluminum hydroxide / copper hydroxide. After the precipitation is completed, the iron, aluminum and copper removal filtrate and the iron hydroxide / aluminum hydroxide / copper hydroxide precipitate are obtained by filtration. The substance in the iron hydroxide / aluminum hydroxide / copper hydroxide precipitate is mainly copper hydroxide, which can be used to further recover the copper element therein.

[0066] S8, the obtained iron / aluminum / copper removed filtrate is passed through an exchange resin to remove calcium, magnesium and high-valent cationic impurities to obtain a purified solution.

[0067] S9, concentrating the purified liquid obtained in S8 and adding tertiary alkali solution to precipitate lithium ions to obtain a portion of lithium carbonate product.

[0068] Furthermore, in step S1, the primary calcination temperature is 300-400°C, the calcination time is 0.5-3.5 hours, the heating rate is 2-10°C / min, and the calcination atmosphere is nitrogen or argon. The protective gas is used to prevent the carbon dioxide generated by the reaction of carbon and oxygen during the calcination process from destroying the structure of the ternary material and preventing the generated CO from reducing the ternary material to low-valent oxides that are easily soluble in dilute acid, causing loss of the ternary material. The primary calcination removes the volatile electrolyte in the electrode and destroys and decomposes the binder in the active material, separating the positive and negative active materials from the copper and aluminum foils while converting the active materials into easily dispersible powders.

[0069] Furthermore, in step S1, the pulverization and screening process involves pulverizing and screening the primary calcined material, separating the aluminum foil, copper foil, and some graphite from the powdered electrode material based on differences in particle size and density. This process can separate over 98% of the copper and aluminum foils and over 60% of the graphite from the electrode material. The resulting electrode material after further pulverization and screening has a particle size of less than 0.6 mm. The screened copper, aluminum, and graphite can be sold as by-products.

[0070] Furthermore, in the above-mentioned step S2, the solid-liquid ratio of the flotation carbon removal is (80-200):1g / L, the stirring speed is 100-300rpm, the stirring is carried out for 5-30min, and the mixture is allowed to stand for 5-30min after stirring, and the carbon powder floating on the upper layer is filtered out to obtain graphite material. The stirring, standing, and carbon filtration steps are repeated 2-6 times, and then the carbon removal black powder is filtered out. The filtrate can be recycled for the flotation carbon removal step. The purpose of carbon removal is to prevent the CO generated by the reaction of carbon and oxygen during the secondary oxygen-enriched roasting process from destroying the structure of the ternary material, and to prevent the generated CO from reducing the ternary material to low-valent oxides that are easily soluble in dilute acid, resulting in loss of the ternary material.

[0071] The carbon black powder filtered out in step S2 is dried at 250°C for 1-3 hours and then subjected to secondary calcination. The secondary calcination temperature is 400-500°C. At this temperature, copper reacts with oxygen to form copper oxide, which is easily soluble in dilute acid. Aluminum and iron impurities do not react with oxygen at this temperature. The secondary calcination time is 0.5-2 hours, and the oxygen concentration during the calcination process is greater than 60%. This increased oxygen concentration helps improve copper oxidation efficiency.

[0072] Furthermore, in the dilute acid leaching in step S4, the solid-liquid ratio of the roasted black powder to the acid solution is (120-180):1 g / L, the stirring speed during the acid leaching process is 100-300 rpm, the acid leaching time is 0.5-2 h, the acid leaching process temperature is controlled at 20-80 ° C, and the acid leaching process pH is controlled at 1-1.6.

[0073] Furthermore, in the countercurrent pickling process in step S4, the pH of the pickling liquid is 1 to 1.6, the number of countercurrent washings is 2 to 10 times, and the black powder after washing is dried at a temperature of 120 to 350° C. for 1 to 3 hours.

[0074] In the further above-mentioned step S5, the oxidant is any one of hydrogen peroxide and ozone, and the molar amount of the oxidant is 1 to 3 times the molar amount of the iron element in the solution. The concentration of the hydrogen peroxide used is 8 to 30wt%. In the further above-mentioned steps S6 and S7, the primary and secondary alkali liquors used can be optionally sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. The further primary and secondary alkali liquor concentrations are nearly saturated solutions (the saturated concentration of the alkali liquor is C0, and the concentration of the alkali liquor nearly saturated solution is C1, satisfying 0.9C0≤C1≤C0). The further addition of the primary alkali liquor iron-aluminum precipitation process controls the solution pH value to be 3.8 to 4.3, and the precipitation time is 0.5 to 2h. The further addition of the secondary alkali liquor iron-aluminum-copper precipitation process controls the solution pH value to be 6.5 to 7, and the precipitation time is 0.5 to 2h. The further exchange resin used in the above-mentioned step S8 is Resin, 732 cation exchange resin, etc., are used to deeply remove high-valent cation impurities such as calcium and magnesium.

[0075] Further, in the above step S9, the purified liquid is concentrated, and the lithium ion concentration after concentration is 20-30 g / L. The purified liquid can also be used to prepare dilute sulfuric acid and then returned to the acid leaching or acid leaching washing process, and after multiple enrichment of lithium ions, it is concentrated and precipitated. Further, in the above step S9, the tertiary alkali solution is sodium carbonate or potassium carbonate solution, and the concentration range of the alkali solution is 150-350 g / L. The molar amount of sodium carbonate or potassium carbonate in the alkali solution is Li in the solution. + The lithium precipitation temperature is 60-98°C and the lithium precipitation time is 0.2-3h.

[0076] 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.

[0077] Example 1

[0078] Based on pre-impurity removal and recycling of ternary lithium batteries, the specific process flow chart is as follows Figure 1 As shown, 20 18650-type ternary lithium-ion batteries, whose positive electrode material is NCM622, were discharged and disassembled, yielding 596.4g of positive and negative electrode sheets. These sheets were then calcined at 350°C for 2h under a nitrogen atmosphere. After crushing and screening, 267.1g of electrode material was obtained. The elemental contents after crushing and screening are shown in Table 1-1. After calcination, 2.5L of deionized water was added, and the mixture was stirred at 150 rpm / min for 30min, allowed to stand for 10min, and then subjected to flotation for carbon removal. This stirring / standing / flotation process was repeated three times. After carbon removal, the black powder was dried at 180°C for 2h, yielding 260.98g of decarbonized black powder. The elemental contents after carbon removal are shown in Table 1-2. The dried decarbonized black powder was calcined at 400°C for 1h under an 80% oxygen atmosphere, yielding 260.99g of baked black powder. The roasted black powder was added with 2.37L of sulfuric acid solution with a pH of 1.2 (solid-to-liquid ratio of 110.12g / L). Concentrated sulfuric acid was added during the dissolution process to control the pH of the dissolution process between 1 and 1.6. The acid leaching time was 1 hour, the acid leaching temperature was 60°C, and stirring was applied at 200rpm / min during the acid leaching process. The pH value of the acid leaching end point was 1.5. After the acid leaching, the acid leached black powder and the acid leaching liquid were obtained. The acid leached black powder was countercurrently washed 5 times with sulfuric acid solution with a pH of 1.3. After the acid washing, it was washed with deionized water. After the deionized water washing, the black powder was dried at 280°C for 3 hours to obtain 252.2g of purified black powder. The content of each element after crushing and screening is shown in Tables 1-3, and its impurities have been relatively completely removed.

[0079] Add 2.8g of 8% hydrogen peroxide to the acid leaching solution to oxidize the divalent iron ions in the acid leaching solution (the molar amount of H2O2 is 1 times the molar amount of iron element), and then add 65.27mL of 200g / L sodium carbonate solution to the acid leaching solution to precipitate iron and aluminum. During the precipitation process, the pH is controlled at 3.8-4.3, and the precipitation time is 2h. After the precipitation is completed, filter to obtain iron-aluminum precipitate and iron-aluminum-removed filtrate. Add 3.57ml of 200g / L sodium carbonate solution to the iron-aluminum-removed aluminum filtrate to precipitate iron, aluminum and copper. During the precipitation process, the pH is controlled at 6.5-7, and the precipitation time is 2h. After the precipitation is completed, filter to obtain iron, aluminum and copper precipitate (ferric hydroxide / aluminum hydroxide / copper hydroxide) and iron-aluminum-copper-removed filtrate. Use The resin was used to deeply remove impurities from the iron, aluminum, and copper removal filtrate to obtain a purified solution. The purified solution was heated and concentrated to 159.2 mL, at which point the lithium ion concentration in the solution was 23 g / L. 93.2 mL of a 300 g / L sodium carbonate solution was added to the purified solution. The precipitation process was performed at 90°C for 1 hour. The precipitate was filtered and washed with water to obtain 17.92 g of lithium carbonate with a purity of 99.92%.

[0080] Table 1-1 Content of each element after crushing and screening

[0081] element Al Fe Cu C Li Ni Co Mn Proportion 0.60％ 0.13％ 0.02％ 2.10％ 6.87％ 34.86％ 11.67％ 10.88％

[0082] Table 1-2 Content of each element after carbon removal

[0083] element Al Fe Cu C Li Ni Co Mn Proportion 0.61％ 0.13％ 0.02％ 0.08％ 7.01％ 35.58％ 11.91％ 11.10％

[0084] Table 1-3 Element contents of impurity-removed ternary black powder

[0085] element Al Fe Cu Li Ni Co Mn Proportion 12ppm 8ppm 3ppm 5.80％ 36.81％ 12.32％ 11.49％

[0086] Example 2

[0087] Twenty 18650-type ternary lithium-ion batteries, using NCM811 as the positive electrode material, were disassembled and discharged to obtain 588g of positive and negative electrode sheets. These sheets were then calcined at 350°C for 2h under a nitrogen atmosphere. After crushing and screening, 266.2g of electrode material was obtained. The elemental contents after crushing and screening are shown in Table 2-1. After calcination, 2.5L of deionized water was added. The mixture was stirred at 150 rpm / min for 30min, allowed to stand for 10min, and then subjected to flotation for carbon removal. This stirring / standing / flotation process was repeated three times. After carbon removal, the black powder was dried at 180°C for 2h. After drying, 257.70g of decarbonized black powder was obtained. The elemental contents after decarbonization are shown in Table 2-2. The dried decarbonized black powder was calcined at 450°C for 1.5h under a 60% oxygen atmosphere, yielding 257.71g of baked black powder. 257.71 g of roasted black powder was added to 2.15 L of sulfuric acid solution with a pH of 1.2 (solid-to-liquid ratio of 119.87 g / L). Concentrated sulfuric acid was added during the dissolution process to control the pH of the dissolution process between 1 and 1.6. The acid leaching time was 1 hour, the acid leaching temperature was 80°C, and stirring was applied at 200 rpm / min during the acid leaching process. The pH value of the acid leaching end point was 1.2. After the acid leaching, the acid-leached black powder and the acid leaching liquid were obtained. The acid-leached black powder was countercurrently washed five times with sulfuric acid solution with a pH of 1.2. After the acid washing, it was washed with deionized water. After the deionized water washing, the black powder was dried at 280°C for 3 hours to obtain 249.1 g of purified black powder. The element contents after crushing and screening are shown in Table 2-3, indicating that the impurities have been relatively completely removed.

[0088] Add 3.0g of 8% hydrogen peroxide to the acid leaching solution to oxidize the divalent iron ions in the acid leaching solution (the molar amount of H2O2 is 1 times the molar amount of iron element), and then slowly add 90.71mL of 200g / L sodium carbonate solution to the acid leaching solution to precipitate iron and aluminum. During the precipitation process, the pH is controlled at 3.8-4.3, and the precipitation time is 2h. After the precipitation is completed, filter to obtain iron-aluminum precipitate and iron-aluminum-removed filtrate. Add 4.38mL of 200g / L sodium carbonate solution to the iron-aluminum-removed aluminum filtrate to precipitate iron, aluminum and copper. During the precipitation process, the pH is controlled at 6.5-7, and the precipitation time is 2h. After the precipitation is completed, filter to obtain iron, aluminum and copper precipitate (ferric hydroxide / aluminum hydroxide / copper hydroxide) and iron-aluminum-copper-removed filtrate. Use The resin was used to deeply remove impurities from the iron, aluminum, and copper removal filtrate to obtain a purified solution. The purified solution was heated and concentrated to 161.2 mL, at which point the lithium ion concentration in the solution reached 20 g / L. 82.37 mL of a 300 g / L sodium carbonate solution was added to the purified solution. The precipitation process was performed at 90°C for 1 hour. The precipitate was filtered and washed with water to obtain 15.85 g of lithium carbonate with a purity of 99.97%.

[0089] Table 2-1 Content of each element after crushing and screening

[0090] element Al Fe Cu C Li Ni Co Mn Proportion 0.73％ 0.14％ 0.028％ 3.0％ 6.77％ 45.8％ 5.75％ 5.36％

[0091] Table 2-2 Content of each element after carbon removal

[0092]

[0093]

[0094] Table 2-3 Content of each element in the impurity-removed ternary black powder

[0095] element Al Fe Cu Li Ni Co Mn Proportion 13ppm 7ppm 6ppm 5.92％ 48.83％ 6.13％ 5.71％

[0096] According to the results of Examples 1 and 2 above, the method for recycling ternary lithium batteries based on pre-impurity removal provided by this application can obtain an Al content of less than 15 ppm in the impurity-removed black powder, and a Fe and Cu content of less than 10 ppm, which is beneficial for reducing the impact of the above-mentioned impurity metal elements on the subsequent recovery process of the ternary black powder. At the same time, this application can recover lithium elements in the form of lithium carbonate from ternary lithium batteries to obtain a high-purity lithium carbonate product.

[0097] The above 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 recycling ternary lithium batteries based on pre-impurity removal, characterized in that: The following steps are involved: Step S1: disassembling the ternary lithium battery after discharge and performing a first calcination treatment under a protective atmosphere, crushing and screening to obtain current collector material, negative electrode active material and primary black powder; Step S2: adding the primary black powder into water for flotation decarbonization, and drying to obtain the decarbonized primary black powder; Step S3: performing a second calcination treatment on the carbon-removed primary black powder in an oxygen-containing atmosphere to oxidize the copper in the carbon-removed primary black powder into copper oxide to obtain calcined black powder; Step S4: adding the roasted black powder into an acid solution for acid leaching, so that non-lithium substances in the roasted black powder react with the acid solution and dissolve, thereby obtaining an acid leaching solution and impurity-removed ternary black powder; Wherein, the acid leaching solution includes at least one of Li+, Fe2+, Fe3+, Al3+, Cu2+, Ca2+ or Mg2+.

2. The method according to claim 1, characterized in that In step S1, the conditions of the first calcination treatment include: heating to 300-400°C at a heating rate of 2-10°C / min, and calcining at this temperature for 0.5-3.5h; Preferably, the protective atmosphere is selected from at least one of nitrogen and argon; Preferably, the primary black powder includes lithium transition metal oxide, C element, Cu element, Al element, Fe element, Mg element and Ca element.

3. The method according to claim 1, characterized in that In step S2, the conditions of the flotation decarbonization treatment include: the solid-liquid ratio of primary black powder and water is (80-200):1 g / L, stirring at 100-300 rpm for 5-30 minutes, standing for 5-30 minutes, and filtering out the carbon element floating on the upper layer; repeating the stirring, standing, and filtering operations 2-6 times.

4. The method according to claim 1, wherein In step S3, the volume fraction of oxygen in the oxygen-containing atmosphere is greater than or equal to 60%.

5. The method according to claim 1, characterized in that In the step S3, the conditions of the second calcination treatment include: calcination at 400-500° C. for 0.5-2 hours.

6. The method according to claim 1, characterized in that In step S4, the conditions for the acid leaching treatment include: a solid-liquid ratio of roasted black powder to acid solution of (120-180):1 g / L, acid leaching at 20-80° C. for 0.5-2 h, and controlling the pH of the system to be 1-1.6 during the acid leaching process.

7. The method according to claim 1, characterized in that In the step S4, after the acid leaching treatment, the following steps are further included: After the acid leaching treatment, filtering is performed to obtain the acid leaching liquid and the roasted black powder after the acid leaching treatment; The roasted black powder after acid leaching is washed with acid solution and dried to obtain the impurity-removed ternary black powder; Preferably, the pH of the acid solution in the washing treatment is 1 to 1.6, and the pickling solution obtained from the washing treatment is used for the acid leaching treatment.

8. The method according to any one of claims 1 to 7, characterized in that Also includes: Step S5: adding an oxidant to the acid leaching solution to oxidize Fe2+ in the acid leaching solution to Fe3+, thereby obtaining an oxidized acid leaching solution; Step S6: adding a primary alkali solution to the oxidizing acid leaching solution to adjust the pH of the solution for precipitation treatment, so as to precipitate Fe3+ and Al3+ in the oxidizing acid leaching solution to obtain iron-aluminum slag and iron-aluminum-removed filtrate; Step S7: adding a secondary alkali solution to the de-iron and de-aluminum filtrate to adjust the pH of the solution for precipitation treatment, so as to precipitate Cu2+ and the remaining Fe3+ and Al3+ in the de-iron and de-aluminum filtrate to obtain copper-iron-aluminum slag and the de-iron and de-copper-iron-aluminum filtrate; Step S8: passing the iron, aluminum and copper removal filtrate through an ion exchange resin to remove Ca2+ and Mg2+ to obtain a purified solution; Step S9: adding a tertiary alkali solution to the purified liquid to perform a lithium precipitation reaction to obtain a lithium carbonate product; Wherein, the tertiary alkali solution includes sodium carbonate solution and / or potassium carbonate solution.

9. The method according to claim 8, characterized in that The method satisfies at least one of the following conditions: (1) In step S5, the oxidant is any one of hydrogen peroxide and ozone, and the molar amount of the oxidant is 1 to 3 times the molar amount of the iron element in the acid leaching solution; (2) In step S6, the primary alkali solution includes at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a sodium carbonate aqueous solution, and a potassium carbonate aqueous solution, and the precipitation treatment conditions include: precipitation for 0.5 to 2 hours at a pH of 3.8 to 4.3; (3) In step S7, the secondary alkali solution includes at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a sodium carbonate aqueous solution, and a potassium carbonate aqueous solution, and the precipitation treatment conditions include: precipitation at a pH of 6.5 to 7 for 0.5 to 2 hours; (4) In step S9, the conditions for the lithium precipitation reaction include: the molar amount of carbonate in the tertiary alkali solution is 0.5 to 0.75 times the molar amount of Li+ in the purified solution; and lithium precipitation is carried out at 60 to 98° C. for 0.2 to 3 hours; (5) In the step S9, before the lithium precipitation reaction is carried out, the purified liquid is concentrated, and the lithium ion concentration in the purified liquid after concentration is 20-30 g / L.

10. The method according to claim 8, characterized in that In step S9, before the lithium precipitation reaction, acid is added to the purified liquid to adjust the pH to 1-1.6, and the purified liquid after pH adjustment is used for acid leaching and / or washing in step S4 to enrich the purified liquid to a lithium ion concentration of 20-30 g / L.

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