Recycling method of lithium ion battery negative electrode material

Abstract

The invention provides a recovery method of a lithium ion battery negative electrode material, and belongs to the technical field of lithium ion battery material recovery. The recovery method comprises the following steps: step S1, obtaining a negative pole piece in an inert atmosphere, then roasting the negative pole piece in the inert atmosphere to obtain a roasted product, adding water into the roasted product in the inert atmosphere to carry out water leaching lithium extraction treatment, and then carrying out first solid-liquid separation treatment to obtain a negative current collector, graphite powder and a lithium extraction solution; s2, at least adding a fluorine removal agent into the lithium extraction liquid for fluorine removal treatment to obtain first treatment liquid; then removing divalent and / or more than divalent metal ions from the first treatment liquid through cation exchange resin to obtain a second treatment liquid; and S3, the second treatment liquid is heated, and a lithium-containing product is obtained. By means of the method, the lithium element can be converted into the lithium-containing product with the high purity, and the recovery rate of the graphite and the lithium element is increased.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium-ion battery material recycling, and specifically relates to a method for recycling negative electrode materials of lithium-ion batteries. Background Art

[0002] With the development of emerging technologies, the application of lithium-ion batteries in new energy vehicles and energy storage 3C digital products has surged. However, lithium-ion batteries usually have a capacity decay value of less than 80% after 5-8 years of use, and will be scrapped due to capacity anxiety and safety considerations. According to data from the China Automotive Technology Research Center, the cumulative scrap volume of lithium-ion batteries in my country in 2020 was about 200,000 tons, and by 2025, the scrap volume of lithium-ion batteries will rise to about 780,000 tons. Lithium-ion batteries are mainly composed of several important parts: positive electrode materials, negative electrode materials, diaphragms, electrolytes, current collectors, and shells. Among them, the main materials of negative electrode materials are usually graphite, hard carbon, silicon carbon, etc., accounting for about 10% of the battery cost and about 15% of the battery mass, that is, in 2025, 780,000 tons of scrapped batteries contain about 117,000 tons of negative electrode main materials.

[0003] The traditional lithium-ion battery recycling method is to process the lithium-ion battery into battery black powder through salt water immersion discharge, crushing, screening and high-temperature roasting, and then separate the elements through acid leaching, organic solvent extraction separation and lithium precipitation. Among them, the negative electrode main material (mainly carbon material) is mixed with the positive electrode material during the crushing process, and then the negative electrode main material is converted into carbon dioxide during the high-temperature roasting process, which will cause the loss of the negative electrode main material and generate a large amount of carbon emissions. In addition, due to incomplete water immersion discharge, the negative electrode material will contain lithium elements. After a long process such as acid leaching, extraction and lithium precipitation, a large amount of lithium elements will be lost, resulting in a waste of lithium metal resources and reducing the recovery efficiency. In addition, the disassembled battery negative electrode material has residual fluorine-containing electrolyte, which will cause serious environmental pollution if not handled properly.

[0004] There is an existing technology that proposes to disassemble lithium-ion batteries in water so that the lithium in the negative electrode material reacts with water and organic solvents such as electrolytes to generate lithium carbonate. This method uses the existing electrolyte in the battery to react with lithium to recover the lithium element in the negative electrode material. However, the electrolyte material content in the battery is limited and cannot fully react with lithium, which reduces the yield of lithium carbonate. In addition, it is difficult to disassemble lithium-ion batteries in water, and the high-priced metal ions such as copper, iron, and aluminum dissolved in the solution during disassembly will also reduce the purity of lithium carbonate. Therefore, how to comprehensively recycle the negative electrode main materials of scrapped lithium-ion batteries with huge potential resources and recycle the negative electrode materials of lithium-ion batteries in a green and environmentally friendly way is an urgent problem to be solved in this field. Summary of the invention

[0005] In view of this, the present application provides a method for recycling negative electrode materials of lithium-ion batteries. By obtaining negative electrode plates and calcining the negative electrode plates under an inert atmosphere, and then combining water leaching lithium treatment to separate graphite powder, and recovering lithium elements and removing impurities, the lithium elements can be subsequently converted into lithium-containing products with higher purity. This method has fewer recovery steps, can reduce lithium element loss, improve graphite and lithium element recovery rates and safety, and has the advantages of being green and environmentally friendly.

[0006] In a first aspect, the present application provides a method for recovering negative electrode materials of lithium-ion batteries, comprising the following steps: step S1, obtaining a negative electrode plate under an inert atmosphere, and then calcining the negative electrode plate under an inert atmosphere to obtain a calcined product, adding water to the calcined product under an inert atmosphere to perform water leaching of lithium, and then performing a first solid-liquid separation treatment to obtain a negative electrode current collector, graphite powder and a lithium extraction solution; step S2, at least adding a defluorinating agent to the lithium extraction solution for defluorination treatment to obtain a first treatment solution; then removing divalent and / or divalent or higher metal ions from the first treatment solution through a cation exchange resin to obtain a second treatment solution; step S3, heating the second treatment solution to obtain a lithium-containing product. The present application uses a roasting process to gasify and decompose the organic matter such as the binder and electrolyte remaining in the negative electrode plate, thereby reducing the difficulty of separating the negative electrode active material and the copper foil current collector. Combined with the subsequent water leaching lithium extraction process, the copper foil current collector and the negative electrode main material graphite powder can be easily separated, and it is also beneficial to improve the copper foil current collector yield, reduce the copper ion impurities in the lithium extraction solution, and improve the recovery rate and recovery efficiency of the two. In addition, the lithium element (usually lithium element) in the negative electrode plate can be converted into a lithium extraction solution (LiOH solution) in the form of a solution. The lithium extraction solution can remove fluorine and other metal ion impurities through defluorination treatment and cation exchange resin treatment, which is beneficial to obtain a higher purity lithium-containing product. At the same time, the lithium element treatment requires fewer steps, which can avoid the loss of lithium elements and improve the recovery rate of lithium elements. The present application can obtain high-value graphite powder and lithium-containing products through the above method, which has the advantages of low cost and green environmental protection.

[0007] In the present application, the negative electrode sheet can be obtained by methods known in the art, such as disassembling the lithium-ion battery under an inert atmosphere to separate the negative electrode sheet. In particular, the present application does not specifically limit the state of charge of the lithium-ion battery before disassembly, for example, it can be any value within a range of 0% to 100%.

[0008] In the present application, the inert atmosphere is selected from at least one of argon, helium, neon, krypton, xenon or radon. It is understood that the types of inert atmospheres used in the disassembly of the lithium-ion battery, the roasting treatment in step S1 and the water leaching of lithium can be the same or different.

[0009] In some embodiments, in step S2, at least a defluorinating agent is added to the lithium extraction solution for defluorination treatment to obtain a first treatment liquid, including: adding a defluorinating agent to the lithium extraction solution to obtain a defluorination system, and subjecting the defluorination system to a second solid-liquid separation treatment to obtain a defluoridating liquid and a fluoride residue, wherein the defluoridating liquid is the first treatment liquid. The present application adopts water leaching lithium treatment to convert the lithium element in the negative electrode plate into lithium hydroxide, which is present in the lithium extraction solution, wherein the fluorine-containing solvent contained in the electrolyte remaining in the negative electrode plate will form fluorine impurities in the lithium extraction solution. The present application can quickly and effectively remove fluorine impurities in the form of a solid phase through a defluorinating agent, thereby improving the purity of lithium-containing products.

[0010] In some embodiments, in step S2, at least a defluorination agent is added to the lithium extraction liquid for defluorination treatment to obtain a first treatment liquid, including: adding a defluorination agent to the lithium extraction liquid to obtain a defluorination system, performing a second solid-liquid separation treatment on the defluorination system to obtain a defluorination liquid and a fluoride residue, and then passing carbon dioxide gas into the defluorination liquid to obtain a first treatment liquid, wherein the first treatment liquid contains lithium bicarbonate. Passing carbon dioxide after the defluorination treatment to convert lithium hydroxide in the defluorination liquid into lithium bicarbonate is beneficial to improving the solubility of lithium ions and reducing the loss of lithium ions in the subsequent cation exchange resin, thereby improving the yield of lithium elements and facilitating the subsequent removal of impurities in a solution state.

[0011] In practical applications, lithium carbonate is used in more scenarios. Therefore, this process can obtain lithium bicarbonate solution by using excess carbon dioxide gas between defluorination and exchange resin, and further obtain lithium carbonate product by heating treatment.

[0012] In some embodiments, the volume ratio of the defluorination liquid to the carbon dioxide gas is 1:(25-40), preferably 1:(28-33), and more preferably 1:30. The present application introduces an excess of carbon dioxide into the defluorination liquid to carbonize the lithium ions and convert them into a lithium bicarbonate solution with a higher solubility than lithium carbonate, which can further increase the solubility of the lithium ions, facilitate the subsequent removal of impurities by a cation exchange resin in a solution state, reduce the loss of lithium ions, and increase the yield of lithium elements. In addition, when converted into lithium bicarbonate with a higher solubility, compared with a lithium carbonate solution, the mass of the solvent contained in the lithium bicarbonate solution is less when dissolving the same mass of lithium ions, so it is beneficial to reduce the amount of solvent evaporation during subsequent evaporation and crystallization, and reduce energy consumption and costs.

[0013] The method of the present application can obtain LiOH products or Li2CO3 products. Under the guidance of the present application, those skilled in the art can select a recovery method according to actual needs, thereby enriching the types of lithium products.

[0014] In some embodiments, in step S1, the temperature of the calcination treatment is T1°C, and the time of the calcination treatment is t1 h; 300≤T1≤400; 0.5≤t1≤3.0. For example, T1 can be 300, 305, 313, 318, 327, 335, 341, 347, 359, 369, 374, 381, 387, 400 or a value within the range of any two thereof; t1 can be 0.5, 0.6, 0.8, 0.9, 1.2, 1.3, 1.5, 1.7, 1.9, 2.2, 2.4, 2.6, 2.8, 3.0 or a value within the range of any two thereof. When the conditions of the calcination treatment are adjusted to meet the above range, the decomposition efficiency of organic matter in the binder and electrolyte can be improved, while reducing or avoiding the loss of graphite, and improving the recovery efficiency and the yield of the graphite powder product.

[0015] In some embodiments, step S1 further includes: recovering the hydrogen generated during the water leaching of lithium by molecular sieve pressure swing adsorption. The reaction of lithium metal in the negative electrode with water will release hydrogen. The use of molecular sieve pressure swing recovery adsorption can reduce the risk of excessive hydrogen concentration, while obtaining a purer hydrogen product, thereby improving the resource utilization efficiency of lithium-ion batteries. Preferably, the molecular sieve is selected from at least one of type A zeolite molecular sieve, faujasite molecular sieve, and mordenite molecular sieve.

[0016] In some embodiments, in step S1, the first solid-liquid separation treatment includes: after the water leaching lithium treatment is completed, the negative electrode current collector and the mixed system are separated, and then the mixed system is subjected to the first filtration and the second filtration in sequence, and graphite powder is obtained after the first filtration, and the lithium extraction liquid is obtained after the second filtration; the pore size of the filter membrane used for the first filtration is 30μm to 50μm; the pore size of the filter membrane used for the second filtration is 0.01nm to 0.05nm. The present application adopts water leaching lithium treatment to convert lithium into lithium ion solution, combined with the first filtration and the second filtration, wherein the first filtration can separate graphite powder and lithium-containing solution to obtain a graphite powder product, and the second filtration can remove a small amount of residual graphite in the lithium-containing solution to obtain a lithium extraction liquid with higher purity.

[0017] Exemplarily, the pore size of the filter membrane used for the first filtration is 30μm, 31μm, 32μm, 34μm, 35μm, 36μm, 38μm, 39μm, 42μm, 43μm, 44μm, 46μm, 47μm, 50μm or a value within the range of any two thereof, and the pore size of the filter membrane used for the second filtration is 0.01nm, 0.02nm, 0.03nm, 0.04nm, 0.05nm or a value within the range of any two thereof, for example, the second filtration can be performed using a precision filter, and the filter membrane used can be a Dow PVDF membrane. When the pore size of the filter membrane for the first filtration and / or the second filtration is regulated within the above range, the solid-liquid separation treatment efficiency can be improved, which is conducive to further improving the purity of the lithium ion solution and the yield of the graphite powder product.

[0018] In some embodiments, the mixed system is subjected to a first filtration and a second filtration in sequence, graphite powder is obtained after the first filtration, and lithium extraction liquid is obtained after the second filtration, including: first filtration of the mixed system to obtain graphite powder and lithium-containing solution; second filtration of the lithium-containing solution to obtain lithium extraction liquid; wherein the second filtration is fine filtration. Fine filtration can remove a small amount of graphite, suspended matter, colloid, and organic macromolecules in the lithium-containing solution.

[0019] In some embodiments, step S1 further includes: washing the graphite powder to obtain a graphite product and a washing liquid, and combining the washing liquid into a mixed system to continue filtering and extracting lithium. The washing treatment in the present application can be carried out in a manner known in the art, for example, deionized water can be used for countercurrent washing. The obtained graphite product can also be dried under a protective atmosphere, and dispersed and crushed. Among them, the drying temperature is 130-260°C, and the protective atmosphere can be at least one of an inert atmosphere or a nitrogen atmosphere; the dispersion and crushing treatment can be carried out by a high-speed disperser for dispersion grinding, the rotation speed can be adjusted to 8000rpm to 12000rpm, and the dispersion grinding time is 2h to 4h.

[0020] In some embodiments, in step S2, the defluorinating agent is selected from at least one of calcium hydroxide and magnesium hydroxide; and / or, the molar ratio of fluoride ions in the lithium extraction solution to the defluorinating agent is 1:(1.05-5). Exemplarily, the molar ratio of fluoride ions in the lithium extraction solution to the defluorinating agent is 1.05, 1:1.2, 1:1.6, 1:1.7, 1:2.0, 1:2.4, 1:2.8, 1:3.0, 1:3.2, 1:3.6, 1:3.9, 1:4.3, 1:4.5, 1:4.7, 1:5 or a value within the range composed of any two of them. The use of the above-mentioned defluorinating agent can remove fluorine without introducing new impurity anions, which is beneficial to improve the purity of lithium-containing products. On this basis, regulating the molar amount of the defluorinating agent and the fluoride ions in the lithium extraction solution to satisfy the above relationship can further improve the defluorination effect and improve the purity of the lithium-containing product.

[0021] In some embodiments, in step S2, the cation exchange resin comprises At least one of CH-93 resin and 732 cation exchange resin; preferably, the divalent and / or higher-valent metal ions include at least one of calcium ions, magnesium ions, iron ions and aluminum ions.

[0022] In some embodiments, in step S3, the temperature of the heating treatment is T2°C; 90≤T2≤180, for example, the value of T2 can be 90, 94, 102, 108, 115, 121, 128, 133, 145, 146, 154, 164, 167, 176, 180 or a value in the range of any two thereof. The heating treatment can obtain a lithium-containing product and distilled water, and the distilled water can be returned to the water leaching lithium treatment process for recycling.

[0023] In some embodiments, if the defluorination liquid is the first treatment liquid, then in step S3, the second treatment liquid is heated to obtain a lithium hydroxide product. By heating the second treatment liquid obtained by water leaching lithium and defluorination treatment, a lithium hydroxide product with higher purity can be obtained. For the second treatment liquid containing lithium hydroxide, the heating is mainly for evaporation and crystallization.

[0024] In some embodiments, if the first treatment liquid contains lithium bicarbonate, then step S3, the second treatment liquid is subjected to heat treatment to obtain a lithium carbonate product. The second treatment liquid is subjected to heat treatment after water leaching of lithium, defluorination treatment and introduction of carbon dioxide gas for reaction, so that the lithium bicarbonate is thermally decomposed to obtain a lithium carbonate product with higher purity.

[0025] In the present application, after the second treatment liquid is heated to obtain a lithium-containing product, the lithium-containing product can be washed, for example, countercurrent washed 2 to 6 times, and then dried. The drying temperature can be selected from 110°C to 350°C, for example 120°C.

[0026] The method for recycling negative electrode materials of lithium-ion batteries provided in this application has at least the following beneficial effects:

[0027] The present application obtains the negative electrode sheet under an inert atmosphere, then calcines at high temperature to decompose and gasify the organic matter such as the binder and electrolyte in the negative electrode sheet, and then performs water leaching and lithium extraction treatment to react the lithium element in the negative electrode sheet with water, and the graphite powder and lithium extraction liquid can be separated through the first solid-liquid separation treatment. Among them, the technical parameters of the recovered graphite powder reach the battery-grade graphite standard through multiple processes such as graded filtration and separation; the lithium extraction liquid is subjected to defluorination treatment to obtain a defluorination liquid, and the defluorination liquid can be subjected to subsequent treatment to obtain a lithium hydroxide product, or a lithium carbonate product can be obtained by subsequent treatment after carbon dioxide is introduced into the defluorination liquid, which can meet different product requirements and obtain high-value graphite powder products and high-purity lithium-containing products. The method reduces the recycling and processing procedures, can reduce the loss of lithium elements in different processes, and increase the recovery rate of lithium elements to more than 90%. In addition, the purity of the lithium-containing product can be improved by adding a fluoridating agent to remove fluorine, and by exchanging resins to remove impurity elements such as calcium, magnesium, aluminum, and iron. The purity of the recovered lithium hydroxide and lithium carbonate can reach more than 99.9%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a process flow chart of a method for recycling negative electrode materials of lithium-ion batteries provided in Example 1 of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. It should be understood by those skilled in the art that, 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.

[0030] The inventors of the present application found in the research on the recovery of negative electrode materials of lithium-ion batteries that: the negative electrode sheet of the lithium-ion battery is heated together with the separator, so that the separator melts and covers the negative electrode active material and forms a secondary composite film on its surface, and then the secondary composite film is torn in an aqueous solution to separate the negative electrode active material layer from the copper foil, and then the negative electrode active material layer is pyrolyzed and ground. Although this method completes the recovery of the negative electrode active material of the lithium-ion battery, after the secondary composite film is torn in the aqueous solution to separate the negative electrode active material, the lithium in the negative electrode active material will react with water to generate hydrogen. The concentration of hydrogen in the air exceeds 4% and there is a risk of explosion. If it is not properly handled, there will be safety hazards. At the same time, this method also has problems such as carbon cannot be recovered and it is difficult to remove impurities.

[0031] In order to solve the above problems, the present application proposes a method for recycling negative electrode materials of lithium-ion batteries, comprising the following steps:

[0032] Step S1, disassemble the obtained battery under an inert atmosphere (e.g., argon atmosphere) to obtain a negative electrode sheet. The obtained negative electrode sheet is roasted under an inert atmosphere (e.g., argon atmosphere) to decompose and gasify organic matter such as binder and electrolyte. Add deionized water to the roasted negative electrode sheet under a closed inert atmosphere (e.g., argon atmosphere) for water leaching and lithium extraction, and recover the hydrogen generated by the reaction of the negative electrode lithium source (i.e., lithium element) and water through molecular sieve pressure swing adsorption. After the water leaching is completed, the negative electrode copper foil is taken out to obtain a mixed system.

[0033] The obtained mixed system is first filtered to obtain graphite powder and lithium-containing solution, and the obtained graphite powder is counter-washed with deionized water, and then dried and dispersed and crushed under a protective atmosphere to obtain a graphite product. The graphite washing water (washing liquid) is returned to the filtering process and filtered to become part of the lithium-containing solution to recover the lithium element therein.

[0034] The lithium-containing solution obtained above is filtered through a precision filter (i.e., the second filtration) to remove a small amount of graphite remaining therein.

[0035] Step S2: adding a defluorinating agent to the obtained refined filtrate (i.e., lithium extraction solution) to remove the fluoride residue therein through filtration to obtain a defluorinated liquid; the defluorinated liquid can be subsequently treated in different ways:

[0036] Method 1: Directly perform resin exchange on the defluorination liquid to remove high-valent impurity ions, such as Ca 2+ ,Mg 2+ 、Al 3+ , Fe 3+ etc. to obtain a purified liquid; Method 2: Pass carbon dioxide into the above-obtained defluorination liquid to convert lithium ions in the solution into lithium bicarbonate, and then remove divalent and higher metals such as calcium, magnesium, aluminum, and iron in the solution through an exchange resin to obtain a purified liquid.

[0037] Step S3, heating and decomposing the purified liquid (i.e., the second treatment liquid) obtained above to obtain lithium hydroxide or lithium carbonate and distilled water, and returning the distilled water to the water immersion section (i.e., water leaching lithium treatment) for recycling, and obtaining the lithium hydroxide or lithium carbonate through countercurrent washing and drying steps to obtain a high-purity lithium hydroxide or lithium carbonate product.

[0038] In this process, the specific step S1 negative electrode material includes graphite and lithium element (i.e. lithium metal). Lithium element is the lithium ion that is deintercalated during the discharge of the lithium-ion battery and left behind when the lithium ion is intercalated during the charge. The charge and discharge process is shown in the following formula.

[0039] When charging: xLi + +xe - +6C→Li x C6; when discharging: Li x C6→xLi + +xe - +6C.

[0040] In the present application, the negative electrode material may also include other materials such as silicon-carbon materials and oxide materials.

[0041] In some embodiments, after the calcination treatment, the calcined product is added with water under an inert atmosphere for water leaching of lithium, wherein the inert atmosphere can be an argon atmosphere under closed conditions. During the water leaching of lithium, the hydrogen generated by the reaction of the negative electrode lithium element and water can be recovered by molecular sieve pressure swing adsorption.

[0042] After the water leaching lithium treatment is completed, the first solid-liquid separation treatment is carried out to obtain the negative electrode current collector, graphite powder and lithium extraction solution. The negative electrode current collector is generally copper foil, which has been separated from the negative electrode material by the aforementioned roasting and water leaching lithium extraction treatment and can be taken out directly. The remaining mixed system can then be separated by filtration to obtain graphite powder and lithium-containing solution. The obtained graphite powder can be washed, for example, by countercurrent washing with deionized water, and then dried and dispersed and crushed under a protective atmosphere to obtain a graphite product. The washing liquid obtained after the washing treatment can be incorporated into the next batch of the mixed system to recover the lithium element therein. The lithium-containing solution can be filtered to remove a small amount of residual graphite, and the lithium extraction solution can be obtained after precise filtration.

[0043] The present application bakes the negative electrode plates of waste lithium-ion batteries at high temperature under an inert atmosphere to decompose organic matter such as gasified binders and electrolytes, reduce the difficulty of separating the negative electrode active materials and copper foil, and improve the yield of copper foil and negative electrode main material graphite powder. In the process of water leaching lithium, the hydrogen produced by the reaction of the negative electrode lithium single substance with water can be recovered by molecular sieve pressure swing adsorption, reducing safety hazards and increasing recovery benefits. The lithium single substance can be converted into a lithium hydroxide product by the reaction of the negative electrode lithium single substance with water, or it can be converted into a lithium carbonate product by introducing carbon dioxide to recover the lithium element in the lithium-ion battery, reducing the recovery process and improving the lithium element yield. By adding a fluorinating agent to remove fluorine and an exchange resin to remove impurity elements such as calcium, magnesium, aluminum and iron, the purity of the lithium-containing product recovered by the negative electrode can be improved.

[0044] In some embodiments, the time for water leaching lithium treatment is 0.1 to 2 hours, for example, it can be 0.1 h, 0.2 h, 0.3 h, 0.5 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.2 h, 1.3 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h or a value within the range composed of any two of them.

[0045] In some embodiments, step S1 further comprises: washing the graphite powder to obtain a graphite product and a washing liquid, and combining the washing liquid into a mixed system to continue filtering and extracting lithium. The washing treatment in the present application can be carried out in a manner known in the art, for example, countercurrent washing can be performed with deionized water. The number of countercurrent washings of the graphite powder is further 2 to 10 times.

[0046] Example 1

[0047] The recycling method of the negative electrode material of the lithium ion battery in this embodiment, please refer to Figure 1 The process flow diagram shown includes the following steps:

[0048] Step S1, disassemble the lithium iron phosphate battery in an argon glove box, collect 200g of negative electrode plates, the initial ratio of the negative electrode active material layer in the negative electrode plates of the battery is artificial graphite: natural graphite: conductive carbon black: carboxymethyl cellulose (CMC): styrene butadiene rubber (SBR) = 55%: 41%: 0.65%: 1.35%: 2.0%, and the double-sided compaction density is 221g / m 2 The thickness of the copper foil in the negative electrode is 6.8 μm, and the surface density of the copper foil is 60.6 g / m 2 , the mass of copper foil in 200g negative electrode material is 41.4g. The lithium content in the negative electrode active material layer was tested by inductively coupled plasma spectroscopy (ICP). It was calculated that 200g negative electrode sheet contained 7.48g of lithium element. Then the theoretical content of artificial graphite and natural graphite in the negative electrode sheet was calculated to be (200-41.4-7.48)×(55%+41%)=145.08g.

[0049] The negative electrode plate was calcined in an argon atmosphere, the calcination temperature T1℃ was 350℃, and the calcination time t1h was 2.5h. After the calcination, the plate was cooled and deionized water was added under an argon atmosphere for water leaching of lithium. The hydrogen produced by the reaction of the negative electrode lithium element and water was recovered by molecular sieve pressure swing adsorption, wherein the molecular sieve was type A zeolite molecular sieve. After the water leaching of lithium was completed, the negative electrode copper foil was taken out, and the copper foil was washed and dried and weighed to obtain a mass of 40.88g, and the copper foil yield was Q Cu1 =40.88 / 41.4×100%=98.73%. The remaining mixed system is first filtered, and the pore size of the filter membrane used for the first filtration is 50μm, to obtain a lithium-containing solution and graphite powder. Then the lithium-containing solution is second filtered using a precision filter to obtain a lithium extraction solution. The main material of the precision filter is Dow PVDF membrane, and the pore size of the filter membrane is 0.03nm.

[0050] The graphite powder was counter-washed for 5 times, and the washing liquid was merged into the above-mentioned mixed system to continue filtering and extracting lithium. Then, the graphite powder was dried at 220°C under a nitrogen atmosphere, and the dried graphite powder was transported to a high-speed disperser and dispersed and ground for 3 hours at a speed of 8000rpm. After that, a graphite powder product was obtained, wherein the mass of the obtained graphite powder was 138.25g, and the equivalent graphite recovery efficiency was 95.29%. The particle size of the obtained graphite powder was measured using a laser particle size analyzer, and its Dmax was less than 70, reaching the battery grade standard.

[0051] Step S2: Add 0.0.601 g of calcium hydroxide as a defluorinating agent to the lithium extraction solution, and measure the F content of the lithium extraction solution by fluorine electrode potential method. - The content of the fluorine ion in the lithium extraction solution is 0.00154 mol, and the molar ratio of the fluorine ion in the lithium extraction solution to the defluorinating agent is 1:5. Then, the reaction is carried out for 0.5 h under stirring at a speed of 200 r / min for defluorination treatment. After the defluorination treatment is completed, the fluoride residue is removed by filtration to obtain a defluoridated liquid. Carbon dioxide gas is injected into the defluoridated liquid, and the volume ratio of the defluoridated liquid to the carbon dioxide gas is 1:30 to obtain a first treated liquid. Then the first treated liquid is subjected to The CH-93 resin removes divalent and / or divalent metal ions, including calcium ions, magnesium ions, iron ions and aluminum ions, in the solution to obtain a second treatment solution.

[0052] Step S3, heating the second treatment liquid at 160°C to evaporate and obtain distilled water, which can be returned to the water leaching lithium treatment process for recycling. At the same time, the heating treatment also decomposes lithium bicarbonate to obtain a lithium carbonate product, and the obtained lithium carbonate product is countercurrently washed 3 times, and then dried at 120°C for 2h to obtain 38.95g of a lithium carbonate product with a purity of 99.91%, and the calculated comprehensive yield of lithium element is 97.76%.

[0053] Example 2

[0054] The method for recycling the negative electrode material of a lithium ion battery of this embodiment comprises the following steps:

[0055] Step S1, disassemble the ternary lithium battery in an argon glove box, collect 320g of negative electrode sheets, the initial ratio of the negative electrode active material layer in the negative electrode sheet of the battery is artificial graphite: natural graphite: conductive carbon black: carboxymethyl cellulose (CMC): styrene butadiene rubber (SBR) = 57%: 39%: 0.45%: 1.55%: 2.0%, and the double-sided compaction density is 234g / m 2 The thickness of the copper foil in the negative electrode is 7.2 μm, and the surface density of the copper foil is 64.1 g / m 2 , the mass of copper foil in 320g negative electrode material is 66.5g. The lithium content in the negative electrode active material layer was tested by inductively coupled plasma spectroscopy (ICP). It was calculated that 320g negative electrode sheet contained 10.62g of lithium element. Then the theoretical content of artificial graphite and natural graphite in the negative electrode sheet was calculated to be (320-66.5-10.62)×(57%+39%)=233.165g.

[0056] The negative electrode plate was calcined in an argon atmosphere, the calcination temperature T1℃ was 350℃, and the calcination time t1h was 2.5h. After the calcination, the plate was cooled and deionized water was added under an argon atmosphere for water leaching of lithium. The hydrogen produced by the reaction of the negative electrode lithium element and water was recovered by molecular sieve pressure swing adsorption, wherein the molecular sieve was type A zeolite molecular sieve. After the water leaching of lithium was completed, the negative electrode copper foil was taken out, and the copper foil was washed and dried, and the mass of the copper foil was weighed to be 65.7g, and the copper foil yield was Q Cu1 =65.7 / 66.5×100%=98.8%. The remaining mixed system is first filtered, and the pore size of the filter membrane used for the first filtration is 50μm, to obtain a lithium-containing solution and graphite powder. Then the lithium-containing solution is second filtered using a precision filter to obtain a lithium extraction solution. The main material of the precision filter is Dow PVDF membrane, and the pore size of the filter membrane is 0.03nm.

[0057] The graphite powder was counter-washed for 5 times, and the washing liquid was merged into the above-mentioned mixed system to continue filtering and extracting lithium. Then, it was dried at 220°C under a nitrogen atmosphere, and the dried graphite powder was transported to a high-speed disperser and dispersed and ground for 3 hours at a speed of 10,000 rpm. After that, a graphite powder product was obtained, wherein the mass of the obtained graphite powder was 217.49 g, and the equivalent graphite recovery efficiency was 93.28%. The particle size of the obtained graphite powder was measured using a laser particle size analyzer, and its Dmax was less than 70, reaching the battery grade standard.

[0058] Step S2: Add 0.202 g of calcium hydroxide as a defluorinating agent to the lithium extraction solution. The F in the lithium extraction solution tested by fluorine electrode potential method is - The content of fluorine ions in the lithium extraction solution is 0.0024 mol, and the molar ratio of fluorine ions in the lithium extraction solution to the defluorinating agent is 1:1.05. Then, the reaction is carried out for 0.5 h under stirring at a speed of 200 r / min for defluorination treatment. After the defluorination treatment is completed, the fluoride residue is removed by filtration to obtain a defluoridated liquid. Carbon dioxide gas is injected into the defluoridated liquid, and the volume ratio of the defluoridated liquid to the carbon dioxide gas is 1:30 to obtain a first treated liquid. Then the first treated liquid is subjected to The CH-93 resin removes divalent and / or divalent metal ions, including calcium ions, magnesium ions, iron ions and aluminum ions, in the solution to obtain a second treatment solution.

[0059] Step S3, heating the second treatment liquid at 160°C to evaporate and obtain distilled water, which can be returned to the water leaching lithium treatment process for recycling. At the same time, the heating treatment also decomposes lithium bicarbonate to obtain a lithium carbonate product, and the obtained lithium carbonate product is countercurrently washed 3 times, and then dried at 110°C for 2h to obtain 54.60g of a lithium carbonate product with a purity of 99.97%, and the calculated comprehensive yield of lithium element is 96.56%.

[0060] Example 3

[0061] The method for recycling negative electrode materials of lithium ion batteries in this embodiment is different from that in embodiment 1 only in that, after the defluorination treatment in step S2 is completed, carbon dioxide gas is no longer introduced into the defluorination liquid, and the defluorination liquid is directly used as the first treatment liquid for subsequent The second treatment liquid is obtained by treating with CH-93 resin.

[0062] In step S3, the second treatment liquid is heated at 160° C. to evaporate and obtain distilled water, which can be returned to the water leaching lithium treatment process for recycling. After the heating treatment, a lithium hydroxide product is obtained, and the obtained lithium hydroxide product is countercurrent washed 3 times, and then dried at 120° C. for 2 hours to obtain 34.64 g of a lithium hydroxide product with a purity of 99.95%, and the calculated comprehensive yield of lithium element is 97.72%.

[0063] The recovery methods of lithium-ion battery negative electrode materials of Examples 4 to 8 differ from those of Example 1 in that the relevant parameters are adjusted according to Table 1, and the purity of the obtained lithium carbonate product and the comprehensive yield of lithium element are shown in Table 1.

[0064] Table 1

[0065]

[0066] It can be seen from the above embodiments that the present application can efficiently recover and separate copper foil current collectors, graphite powder products and lithium-containing products through the above-mentioned recycling method. This method can reduce the recycling process and reduce the loss of lithium elements in different processes. The recovery rate of lithium elements is increased to more than 90%, and high-purity lithium-containing products with a purity of more than 99.9% and graphite powder products that meet battery-grade standards are obtained. This can increase the added value of recycled products and adapt to the needs of different lithium-containing products in actual industrial production.

[0067] In particular, the present application regulates the volume ratio of the defluorination liquid and the carbon dioxide gas to 1: (25-40), carbonizes the lithium ions and converts them into a lithium bicarbonate solution with higher solubility, which can further improve the solubility of lithium ions compared to lithium carbonate, reduce the loss of lithium ions, and increase the yield of lithium elements (to about 95%). In particular, when the volume ratio of the two is regulated to 1: (28-33), the yield of lithium elements can be further improved, and the recovery efficiency can be improved (to about 97%).

[0068] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for recycling negative electrode materials of lithium ion batteries, characterized in that: The following steps are involved: Step S1, obtaining a negative electrode sheet under an inert atmosphere, and then calcining the negative electrode sheet under an inert atmosphere to obtain a calcined product, adding water to the calcined product under an inert atmosphere to perform water leaching for lithium extraction, and then performing a first solid-liquid separation process to obtain a negative electrode current collector, graphite powder and lithium extraction solution; Step S2, adding a defluorinating agent to at least the lithium extraction solution for defluorination treatment to obtain a first treated solution; Then, the first treatment liquid is passed through a cation exchange resin to remove divalent and / or divalent or higher metal ions to obtain a second treatment liquid; Step S3, heating the second treatment liquid to obtain a lithium-containing product.

2. The recycling method according to claim 1, characterized in that: In the step S2, at least the lithium extraction solution is treated with a defluorinating agent to obtain a first treatment solution, including: adding a defluorinating agent to the lithium extraction solution to obtain a defluorinating system, subjecting the defluorinating system to a second solid-liquid separation treatment to obtain a defluorinating liquid and a fluoride residue, wherein the defluorinating liquid is the first treatment liquid; or A defluorination agent is added to the lithium extraction liquid to obtain a defluorination system, the defluorination system is subjected to a second solid-liquid separation treatment to obtain a defluorination liquid and a fluoride residue, and then carbon dioxide gas is introduced into the defluorination liquid to obtain the first treatment liquid, wherein the first treatment liquid contains lithium bicarbonate.

3. The recycling method according to claim 2, characterized in that: The carbon dioxide gas is introduced into the defluorination liquid, and the volume ratio of the defluorination liquid to the carbon dioxide gas is 1:(25-40); Preferably it is 1:(28~33).

4. The recovery method according to any one of claims 1 to 3, characterized in that: In the step S1, the temperature of the calcination treatment is T1°C, and the time of the calcination treatment is t1 h; 300≤T1≤400; 0.5≤t1≤3.

0.

5. The recovery method according to any one of claims 1 to 3, characterized in that: The step S1 further comprises: recovering the hydrogen generated in the water leaching lithium process by molecular sieve pressure swing adsorption; Preferably, the molecular sieve is at least one selected from type A zeolite molecular sieve, faujasite, and mordenite.

6. The recovery method according to any one of claims 1 to 3, characterized in that: In the step S1, the first solid-liquid separation process includes: After the water leaching lithium treatment is completed, the negative electrode current collector and the mixed system are separated, and then the mixed system is subjected to a first filtration and a second filtration in sequence, graphite powder is obtained after the first filtration, and a lithium extraction solution is obtained after the second filtration; The pore size of the filter membrane used for the first filtration is 30 μm to 50 μm; The pore size of the filter membrane used for the second filtration is 0.01 nm to 0.05 nm.

7. The recycling method according to claim 6, characterized in that: The mixed system is subjected to a first filtration and a second filtration in sequence, graphite powder is obtained after the first filtration, and lithium extraction liquid is obtained after the second filtration, comprising: Performing a first filtration on the mixed system to obtain the graphite powder and the lithium-containing solution; Performing a second filtration on the lithium-containing solution to obtain the lithium-extracting solution; Wherein, the second filtration is fine filtration; Preferably, the graphite powder is washed to obtain a graphite product and a washing liquid, and the washing liquid is combined into the mixed system to continue filtering and extracting lithium.

8. The recovery method according to any one of claims 1 to 3, characterized in that: In step S2, the defluorination agent is selected from at least one of calcium hydroxide and magnesium hydroxide; and / or, The molar ratio of fluoride ions in the lithium extraction solution to the defluorination agent is 1:(1.05-5); Preferably, in step S2, the cation exchange resin comprises At least one of CH-93 resin and 732 cation exchange resin; Preferably, the divalent and / or higher-valent metal ions include at least one of calcium ions, magnesium ions, iron ions, and aluminum ions.

9. The recycling method according to claim 1, characterized in that: In step S3, the temperature of the heating treatment is T2°C; 90≤T2≤180.

10. The recycling method according to claim 2, characterized in that: If the defluorination liquid is the first treatment liquid, then in step S3, the second treatment liquid is subjected to a heating treatment to obtain a lithium hydroxide product; or If the first treatment liquid contains lithium bicarbonate, in step S3, the second treatment liquid is subjected to heating treatment to obtain a lithium carbonate product.

Images