Recovery Method of Anode Material for Lithium-Ion Batteries

Abstract

The present application provides a method for recycling the negative electrode material of a lithium-ion battery, belonging to the technical field of recycling of lithium-ion battery materials. The recycling method includes: Step S1, obtaining a negative electrode plate under an inert atmosphere, then roasting the negative electrode plate under an inert atmosphere to obtain a roasting product, adding water to the roasting product under an inert atmosphere for lithium leaching treatment, and then performing a first solid-liquid separation treatment to obtain a negative electrode current collector, graphite powder, and a lithium leaching solution; Step S2, adding at least a defluorinating agent to the lithium leaching solution for defluorination treatment to obtain a first treated solution; then passing the first treated solution through a cation exchange resin to remove divalent and / or metal ions with a valence of two or more to obtain a second treated solution; Step S3, heating the second treated solution to obtain a lithium-containing product. Through the above method, lithium elements can be converted into lithium-containing products with a relatively high purity, and the recovery rates of graphite and lithium elements can be increased.

Description

Technical Field

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

[0002] With the development of emerging technologies, the application of lithium-ion batteries in new energy vehicles, energy storage, 3C digital products has increased rapidly. However, the battery capacity of lithium-ion batteries usually decays by less than 80% after 5-8 years of use. Due to capacity anxiety and safety considerations, they will be scrapped. According to data from the China Automotive Technology and Research Center, the cumulative scrap volume of lithium-ion batteries in China in 2020 was approximately 200,000 tons. By 2025, the scrap volume of lithium-ion batteries will rise to approximately 780,000 tons. Lithium-ion batteries mainly consist of several important parts: positive electrode material, negative electrode material, separator, electrolyte, current collector, and shell. Among them, the main material of the negative electrode is usually graphite, hard carbon, silicon carbon, etc., accounting for about 10% of the battery cost and about 15% of the battery mass. That is, among the 780,000 tons of scrapped batteries in 2025, there are approximately 117,000 tons of main negative electrode materials.

[0003] The traditional method for recycling lithium-ion batteries is to process lithium-ion batteries through procedures such as soaking in brine for discharging, crushing, screening, and high-temperature roasting to obtain battery black powder, and then separating the elements through procedures such as acid leaching, organic solvent extraction, and lithium precipitation. Among them, the main negative electrode material (mainly carbon material) is mixed with the positive electrode material during the crushing process, and then the main negative electrode material is converted into carbon dioxide during the high-temperature roasting process, resulting in the loss of the main negative electrode material and a large amount of carbon emissions. And due to incomplete water immersion discharge, the negative electrode material contains lithium elements, and a large amount of lithium elements will be lost after long procedures such as acid leaching, extraction, and lithium precipitation, causing waste of lithium metal resources and reducing the recycling efficiency. In addition, the residual fluorine-containing electrolyte in the disassembled battery negative electrode material will cause serious environmental pollution if not properly treated.

[0004] There is a prior art that proposes to disassemble lithium-ion batteries in water, so that lithium in the negative electrode material reacts with water and organic solvents such as electrolyte to generate lithium carbonate. This method uses the existing electrolyte in the battery to react with lithium to recover lithium elements in the negative electrode material. However, the content of electrolyte materials in the battery is limited and cannot react fully with lithium, reducing the lithium carbonate yield; and the operation of disassembling lithium-ion batteries in water is difficult, and high-valent 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 main negative electrode materials of scrapped lithium-ion batteries with a huge potential resource volume and greenly recycle the negative electrode materials of lithium-ion batteries 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 the negative electrode material of a lithium-ion battery. By obtaining the negative electrode sheet in an inert atmosphere, roasting the negative electrode sheet, and then combining water leaching to extract lithium, graphite powder can be separated, lithium elements can be recovered and purified, and subsequently, the lithium elements can be converted into lithium-containing products with relatively high purity. This method has fewer recycling steps, can reduce lithium element loss, improve the recovery rates and safety of graphite and lithium elements, and has the advantages of environmental friendliness and the like.

[0006] In a first aspect, the present application provides a method for recycling the negative electrode material of a lithium-ion battery, including the following steps: Step S1: Obtain the negative electrode sheet in an inert atmosphere, and then roast the negative electrode sheet in an inert atmosphere to obtain a roasted product. Add water to the roasted product in an inert atmosphere for water leaching to extract lithium, and then perform a first solid-liquid separation treatment to obtain a negative electrode current collector, graphite powder, and a lithium extraction solution; Step S2: Add at least a defluorinating agent to the lithium extraction solution for defluorination treatment to obtain a first treatment solution; then pass the first treatment solution through a cation exchange resin to remove divalent and / or metal ions with a valence of two or more to obtain a second treatment solution; Step S3: Heat the second treatment solution to obtain a lithium-containing product. Through the roasting treatment in the present application, organic substances such as the remaining binder and electrolyte in the negative electrode sheet are gasified and decomposed, reducing the separation difficulty between the negative electrode active material and the copper foil current collector. Combining with the subsequent water leaching to extract lithium treatment, the copper foil current collector and the main negative electrode material, graphite powder, can be easily separated. At the same time, it is also beneficial to improve the recovery rate of the copper foil current collector, reduce copper ion impurities in the lithium extraction solution, and improve the recovery rates and recovery efficiency of both. Moreover, the water leaching to extract lithium treatment can also convert the lithium elements (usually lithium metal) in the negative electrode sheet into a lithium extraction solution in the form of a solution (LiOH solution). The lithium extraction solution can remove fluorine elements and other metal ion impurities through defluorination treatment and cation exchange resin treatment, which is beneficial to obtaining a lithium-containing product with relatively high purity. At the same time, the lithium element treatment requires fewer processes, can avoid lithium element loss, and improve the recovery rate of lithium elements. Through the above method, the present application can obtain high-value graphite powder and lithium-containing products, and has the advantages of low cost, environmental friendliness and the like.

[0007] In the present application, the negative electrode sheet can be obtained by methods known in the art. For example, the lithium-ion battery is disassembled in an inert atmosphere to separate the negative electrode sheet. Among them, the present application has no special limitation on the state of charge of the lithium-ion battery before disassembly. For example, it can be any value within 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 can be understood that the types of inert atmosphere used for the disassembly of the lithium-ion battery, the roasting treatment and the water leaching to extract lithium treatment in Step S1 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 solution, including: adding a defluorinating agent to the lithium extraction solution to obtain a defluorination system, performing a second solid-liquid separation treatment on the defluorination system to obtain a defluorinated solution and a fluoride residue, and the defluorinated solution is the first treatment solution. In this application, water leaching lithium treatment is used to convert the lithium metal in the negative electrode sheet into lithium hydroxide, which exists in the lithium extraction solution. Among them, the fluorine-containing solvent contained in the electrolyte remaining in the negative electrode sheet will form fluorine element impurities in the lithium extraction solution. Through the defluorinating agent, the fluorine element impurities can be quickly and effectively removed in the form of solid phase, improving the purity of the lithium-containing product.

[0010] 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 solution, including: adding a defluorinating agent to the lithium extraction solution to obtain a defluorination system, performing a second solid-liquid separation treatment on the defluorination system to obtain a defluorinated solution and a fluoride residue, and then introducing carbon dioxide gas into the defluorinated solution to obtain a first treatment solution, wherein the first treatment solution contains lithium bicarbonate. After defluorination treatment, carbon dioxide is introduced to convert lithium hydroxide in the defluorinated solution into lithium bicarbonate, which is beneficial to improving the solubility of lithium ions, reducing the loss of lithium ions in the subsequent cation exchange resin, thereby improving the recovery rate of lithium element, and facilitating subsequent impurity removal in solution state.

[0011] In practical applications, lithium carbonate has more usage scenarios. Therefore, in this process, by using excessive carbon dioxide gas between defluorination and ion exchange resin, a lithium bicarbonate solution can be obtained, and further a lithium carbonate product can be obtained through heat treatment.

[0012] In some embodiments, the volume ratio of the defluorinated solution to the carbon dioxide gas is 1:(25 - 40), preferably 1:(28 - 33), and more preferably 1:30. In this application, excessive carbon dioxide is introduced into the defluorinated solution to carbonize lithium ions and convert them into a lithium bicarbonate solution with higher solubility than lithium carbonate, which can further improve the solubility of lithium ions, facilitate subsequent impurity removal treatment of lithium ions in solution state through cation exchange resin, reduce the loss of lithium ions, and improve the recovery rate of lithium element. In addition, when converted to lithium bicarbonate with higher solubility, compared with the lithium carbonate solution, the mass of the solvent contained in the lithium bicarbonate solution is less when dissolving the same mass of lithium ions. Therefore, it is beneficial to reduce the solvent evaporation amount during subsequent evaporation crystallization, reducing energy consumption and cost.

[0013] The method of this application can obtain LiOH products, or Li 2 CO 3 products. Those skilled in the art can select the recovery method according to actual needs under the teaching of this application, enriching the types of lithium products.

[0014] In some embodiments, in step S1, the temperature of the roasting treatment is T1 ℃, the roasting treatment time is t 1 h; 300 ≤ T 1 ≤ 400; 0.5 ≤ t 1 ≤ 3.0. For example, T 1 can be 300, 305, 313, 318, 327, 335, 341, 347, 359, 369, 374, 381, 387, 400 or a value within the range composed of any two of them; t 1 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 composed of any two of them. When the conditions of the roasting treatment are adjusted to meet the above range, the decomposition efficiency of the binder and the organic matter in the electrolyte can be improved, while reducing or avoiding the loss of graphite, and the recovery treatment efficiency and the yield of the graphite powder product can be improved.

[0015] In some embodiments, step S1 further includes: performing pressure swing adsorption recovery of molecular sieve on the hydrogen generated during the water leaching lithium treatment. The lithium metal in the negative electrode reacts with water to release hydrogen. Adopting pressure swing adsorption recovery of molecular sieve can reduce the risk brought by too high hydrogen concentration, and at the same time obtain a relatively pure hydrogen product, improving the resource utilization efficiency of the lithium-ion battery. Preferably, the molecular sieve is selected from at least one of A-type 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, separating to obtain the negative electrode current collector and the mixed system, and then sequentially performing the first filtration and the second filtration on the mixed system. After the first filtration, graphite powder is obtained, and after the second filtration, a lithium extraction solution is obtained; 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. In this application, the water leaching lithium treatment is used to convert the lithium metal into the form of a lithium ion solution, combined with the first filtration and the second filtration. The first filtration can separate the graphite powder and the lithium-containing solution to obtain a graphite powder product, and the second filtration can remove the remaining small amount of graphite in the lithium-containing solution to obtain a lithium extraction solution with higher purity.

[0017] Exemplarily, the pore size of the filter membrane 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 composed of any two of them. The pore size of the filter membrane for the second filtration is 0.01nm, 0.02nm, 0.03nm, 0.04nm, 0.05nm or a value within the range composed of any two of them. For example, the second filtration can be carried out 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 adjusted within the above range, the solid-liquid separation treatment efficiency can be improved, which is beneficial 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 sequentially subjected to the first filtration and the second filtration. After the first filtration, graphite powder is obtained, and after the second filtration, a lithium-extracted solution is obtained, including: performing the first filtration on the mixed system to obtain graphite powder and a lithium-containing solution; performing the second filtration on the lithium-containing solution to obtain a lithium-extracted solution; wherein, the second filtration is fine filtration. Fine filtration can remove a small amount of graphite, as well as suspended substances, colloids, 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 solution, and merging the washing solution into the mixed system for continuous lithium extraction by filtration. In this application, the washing treatment can be carried out in a manner known in the art. For example, countercurrent washing can be carried out using deionized water. For the obtained graphite product, drying treatment can also be carried out under a protective atmosphere, as well as dispersion and crushing treatment. 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 dispersing and grinding using a high-speed disperser, and the rotation speed can be adjusted to 8000rpm to 12000rpm, and the time for dispersion and grinding 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-extracted solution to the defluorinating agent is 1:(1.05 - 5). Exemplarily, the molar ratio of fluoride ions in the lithium-extracted 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. Using the above defluorinating agent can remove fluorine without introducing new impurity anions, which is beneficial to improving the purity of the lithium-containing product. On this basis, adjusting the molar amount of the defluorinating agent to satisfy the above relationship with the fluoride ions in the lithium-extracted solution can further improve the defluorination effect and enhance the purity of the lithium-containing product.

[0021] In some embodiments, in step S2, the cation exchange resin includes at least one of CH-93 resin and 732 cation exchange resin; preferably, the divalent and / or metal ions with a valence of more than divalent include at least one of calcium ion, magnesium ion, iron ion, and aluminum ion.

[0022] In some embodiments, in step S3, the temperature of the heat treatment is T 2 °C; 90 ≤ T 2 ≤ 180, for example, the value of T 2 can be 90, 94, 102, 108, 115, 121, 128, 133, 145, 146, 154, 164, 167, 176, 180 or a value within the range composed of any two of them. Through the heat treatment, a lithium-containing product and distilled water can be obtained, 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 heat-treated to obtain a lithium hydroxide product. By heating the second treatment liquid obtained after the water leaching lithium treatment and through the defluorination treatment, a lithium hydroxide product with higher purity can be obtained. For the second treatment liquid containing lithium hydroxide, heating is mainly for evaporation and crystallization.

[0024] In some embodiments, if the first treatment liquid contains lithium bicarbonate, then in step S3, the second treatment liquid is heat-treated to obtain a lithium carbonate product. By heat-treating the second treatment liquid after the water leaching lithium treatment, through the defluorination treatment and the reaction with carbon dioxide gas, the lithium bicarbonate is decomposed by heating to obtain a lithium carbonate product with higher purity.

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

[0026] Based on the lithium-ion battery anode material recovery method provided in this application, the beneficial effects are at least as follows:

[0027] In this application, under an inert atmosphere, a negative electrode sheet is obtained. Then, the binder, electrolyte, and other organic substances in the negative electrode sheet are decomposed and vaporized by high-temperature roasting. Next, lithium extraction treatment with water is carried out to react the lithium metal in the negative electrode sheet with water. After the first solid-liquid separation treatment, graphite powder and lithium extraction solution can be separated. Among them, through processes such as multiple-stage filtration and separation, the technical parameters of the recovered graphite powder reach the battery-grade graphite standard; the lithium extraction solution is obtained as a defluorinated solution after defluorination treatment. The defluorinated solution can obtain lithium hydroxide products through subsequent treatment, or lithium carbonate products can be obtained through subsequent treatment after introducing carbon dioxide into the defluorinated solution, which can meet different product requirements and obtain high-value graphite powder products and high-purity lithium-containing products. This method reduces the recycling process, can reduce the loss of lithium elements in different processes, and increases the recovery rate of lithium elements to more than 90%. In addition, processes such as adding a fluorinating agent for defluorination and using ion exchange resin to remove impurity elements such as calcium, magnesium, aluminum, and iron can improve the purity of lithium-containing products, and the purity of the recovered lithium hydroxide and lithium carbonate can reach more than 99.9%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow diagram of a method for recycling a negative electrode material of a lithium-ion battery provided in Embodiment 1 of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to make the objectives, technical solutions, and advantages of this application clearer, the following further elaborates on this application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application. Those skilled in the art should understand that unless otherwise specified, the raw materials used in the following embodiments are all from ordinary commercially available products, and the devices or equipment used are all purchased from conventional market sales channels.

[0030] The inventors of this application found in the research on the recycling of negative electrode materials of lithium-ion batteries that: heating the negative electrode sheet of the lithium-ion battery together with the separator to melt the separator to coat the negative electrode active material and form a secondary composite film on its surface, then tearing the secondary composite film in an aqueous solution to separate the negative electrode active material layer from the copper foil, and subsequently pyrolyzing and grinding the negative electrode active material layer. Although this method completes the recycling of the negative electrode active material of the lithium-ion battery, after tearing the secondary composite film in an aqueous solution to separate the negative electrode active material, the lithium in the negative electrode active material will react with water to generate hydrogen, and the concentration of hydrogen in the air exceeds 4% and there is a risk of explosion, and there are potential safety hazards if not properly handled. At the same time, this method also has problems such as the inability to recycle carbon and difficulty in removing impurities.

[0031] To solve the above problems, this application proposes a method for recycling a negative electrode material of a lithium-ion battery, including the following steps:

[0032] Step S1: Disassemble the obtained battery in an inert atmosphere (e.g., argon atmosphere) to obtain the negative electrode plate. Bake and decompose the obtained negative electrode plate in an inert atmosphere (e.g., argon atmosphere) to vaporize organic substances such as binders and electrolytes. Add deionized water to the baked negative electrode plate under an inert atmosphere (e.g., argon atmosphere) in a closed condition for lithium extraction by water leaching. Recover hydrogen gas generated by the reaction of the negative lithium source (i.e., lithium metal) with water through molecular sieve pressure swing adsorption. After the water leaching is completed, take out the negative copper foil to obtain a mixed system.

[0033] Perform the first filtration on the obtained mixed system to obtain graphite powder and a lithium-containing solution. Wash the obtained graphite powder with deionized water in a countercurrent manner, and then perform drying and dispersion and crushing processes under a protective atmosphere to obtain graphite products. The graphite washing water (washing liquid) is returned to the filtration process and filtered to become a part of the lithium-containing solution to recover the lithium element therein.

[0034] Remove the remaining small amount of graphite in the above-obtained lithium-containing solution through a precision filter (i.e., the second filtration).

[0035] Step S2: Add a defluorinating agent to the obtained refined filtrate (i.e., lithium extraction solution), and filter to remove the fluoride residue therein to obtain a defluorinated solution; different methods can be used for subsequent treatment of the defluorinated solution:

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

[0037] Step S3: Heat and decompose the above-obtained purified solution (i.e., the second treatment solution) to obtain lithium hydroxide or lithium carbonate and distilled water. The distilled water is returned to the water immersion section (i.e., lithium extraction by water leaching) for recycling. The obtained lithium hydroxide or lithium carbonate is obtained through countercurrent washing and drying processes to obtain high-purity lithium hydroxide or lithium carbonate products.

[0038] In this process, specifically, the negative electrode material in Step S1 includes graphite and lithium metal (i.e., lithium metal). Lithium metal is left when lithium ions are deintercalated during the discharge of the lithium-ion battery and intercalated during charging. The charge and discharge processes are shown as follows.

[0039] During charging: xLi + +xe - +6C→Li x C 6 ; During discharging: Li x C 6 →xLi+ +xe - +6C。

[0040] In this application, the anode material may further include other materials such as silicon-carbon materials and oxide materials.

[0041] In some embodiments, after the roasting treatment, the roasted product is leached with water under an inert atmosphere. The inert atmosphere can be an argon atmosphere under closed conditions. During the lithium leaching process, hydrogen gas generated by the reaction of lithium metal in the anode with water can be recovered by pressure swing adsorption using molecular sieves.

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

[0043] In this application, the used lithium-ion battery anode plate is roasted at a high temperature under an inert atmosphere to decompose and gasify organic substances such as binders and electrolytes, reduce the difficulty of separating the anode active material from the copper foil, and improve the recovery rates of the copper foil and the main anode material graphite powder. During the lithium leaching treatment, hydrogen gas generated by the reaction of lithium metal in the anode with water can be recovered by pressure swing adsorption using molecular sieves, reducing potential safety hazards and increasing the recovery benefits. Through the reaction of lithium metal in the anode with water, lithium metal can be converted into lithium hydroxide products, or further converted into lithium carbonate products by introducing carbon dioxide, so as to recover the lithium element in the lithium-ion battery, reduce the recycling process, and improve the recovery rate of the lithium element. By adding a fluorinating agent to remove fluorine and using ion exchange resins to remove impurity elements such as calcium, magnesium, aluminum, and iron, the purity of the lithium-containing products recovered from the anode can be improved.

[0044] In some embodiments, the time for the lithium leaching treatment is 0.1 - 2 h, 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 any value within the range composed of any two of them.

[0045] In some embodiments, step S1 further includes: washing the graphite powder to obtain a graphite product and a washing solution, and incorporating the washing solution into the mixed system for continuous lithium extraction by filtration. In the present application, the washing treatment can be carried out in a manner known in the art. For example, countercurrent washing can be carried out using deionized water. Further, the number of times of countercurrent washing of the graphite powder is 2 to 10 times.

[0046] Example 1

[0047] For the recovery method of the negative electrode material of the lithium-ion battery in this embodiment, please refer to Figure 1 the process flow chart shown below, which includes the following steps:

[0048] Step S1: Disassemble the lithium iron phosphate battery in an argon glove box, and collect 200 g of the negative electrode sheet. The initial ratio of the negative electrode active material layer in the negative electrode sheet of this 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 221 g / m 2 . The thickness of the copper foil in the negative electrode sheet is 6.8 μm, and the areal density of the copper foil is 60.6 g / m 2 , and the mass of the copper foil in 200 g of the negative electrode material is 41.4 g. Use inductively coupled plasma spectroscopy (ICP) to test the lithium content in the negative electrode active material layer. After calculation, it is obtained that 200 g of the negative electrode sheet contains 7.48 g of lithium element. Then, calculate the theoretical content of artificial graphite and natural graphite in the negative electrode sheet as (200 - 41.4 - 7.48)×(55% + 41%) = 145.08 g.

[0049] Roast the negative electrode sheet in an argon atmosphere. The roasting temperature T 1 °C is 350 °C, and the roasting time t 1 h is 2.5 h. After the roasting treatment is completed, after the sheet cools, add deionized water in an argon protection atmosphere for lithium extraction by water leaching, and then recover the hydrogen generated by the reaction of lithium metal and water in the negative electrode by molecular sieve pressure swing adsorption. The molecular sieve is A-type zeolite molecular sieve. After the lithium extraction by water leaching is completed, take out the negative electrode copper foil. After washing and drying the copper foil, weigh the obtained copper foil mass, which is 40.88 g. The copper foil recovery rate Q Cu1 = 40.88 / 41.4 × 100% = 98.73%. First filter the remaining mixed system. The pore size of the filter membrane used for the first filtration is 50 μm to obtain a lithium-containing solution and graphite powder. Then, the lithium-containing solution is secondarily filtered using a precision filter to obtain a lithium-extracted solution. The main material of the precision filter is a Dow PVDF membrane, and the pore size of the filter membrane is 0.03 nm.

[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 320 g of the negative electrode material is 66.5 g. The lithium content in the negative electrode active material layer was measured using inductively coupled plasma spectroscopy (ICP). After calculation, it was found that 320 g of the negative electrode sheet contained 10.62 g of lithium element. Then, the theoretical content of artificial graphite and natural graphite in the negative electrode sheet was calculated as (320 - 66.5 - 10.62)×(57% + 39%) = 233.165 g.

[0056] The negative electrode sheet was calcined under an argon atmosphere. The temperature T 1 of the calcination was 350 °C, and the time t 1 h of the calcination was 2.5 h. After the calcination, after the sheet cooled, deionized water was added for lithium extraction by water leaching under an argon protection atmosphere. Then, the hydrogen gas generated by the reaction of lithium metal and water in the negative electrode was recovered by pressure swing adsorption using molecular sieve, where the molecular sieve was type A zeolite molecular sieve. After the lithium extraction by water leaching was completed, the negative electrode copper foil was taken out. After washing and drying the copper foil, the mass of the obtained copper foil was weighed as 65.7 g, and the copper foil recovery rate Q Cu1 = 65.7 / 66.5×100% = 98.8%. The remaining mixed system was subjected to a first filtration. The pore size of the filter membrane used for the first filtration was 50 μm, and a lithium-containing solution and graphite powder were obtained. Then, the lithium-containing solution was subjected to a second filtration using a precision filter to obtain a lithium-extracted solution. The main material of the precision filter was a Dow PVDF membrane, and the pore size of the filter membrane was 0.03 nm.

[0057] The graphite powder was washed countercurrently 5 times, and the washing liquid was combined into the above-mentioned mixed system for continuous filtration and lithium extraction. Then, it was dried at 220 °C under a nitrogen atmosphere. The dried graphite powder was transported to a high-speed disperser and dispersed and ground at a rotation speed of 10,000 rpm for 3 h. After that, a graphite powder product was obtained. The mass of the obtained graphite powder was 217.49 g, and the 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, meeting the battery-grade standard.

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

[0059] Step S3: Heat the second treatment liquid at 160°C for evaporation to obtain distilled water, which can be recycled back to the lithium extraction process by water leaching. Meanwhile, lithium bicarbonate is decomposed during the heating treatment to obtain lithium carbonate products. The obtained lithium carbonate products are washed countercurrently three times and then dried at 110°C for 2 hours to obtain 54.60 g of lithium carbonate products with a purity of 99.97%. The comprehensive recovery rate of lithium element is calculated to be 96.56%.

[0060] Example 3

[0061] The method for recycling the negative electrode material of the lithium-ion battery in this example is only different from that in Example 1 in that after the defluorination treatment in Step S2, carbon dioxide gas is not introduced into the defluorinated liquid, and the defluorinated liquid is directly used as the first treatment liquid for subsequent treatment with CH-93 resin to obtain the second treatment liquid.

[0062] In Step S3, the second treatment liquid is heated at 160°C for evaporation to obtain distilled water, which can be recycled back to the lithium extraction process by water leaching. After the heating treatment, lithium hydroxide products are obtained. The obtained lithium hydroxide products are washed countercurrently three times and then dried at 120°C for 2 hours to obtain 34.64 g of lithium hydroxide products with a purity of 99.95%. The comprehensive recovery rate of lithium element is calculated to be 97.72%.

[0063] The methods for recycling the negative electrode materials of lithium-ion batteries in Examples 4 to 8 are only different from that in Example 1 in that the relevant parameters are adjusted according to Table 1, and the purity of the obtained lithium carbonate products and the comprehensive recovery rate of lithium element are shown in Table 1.

[0064] Table 1

[0065]

[0066] As can be seen from the above examples, through the above recycling method, the present application can efficiently recycle and separate the copper foil current collector, graphite powder products and lithium-containing products. This method can reduce the recycling process, reduce the loss of lithium element in different processes, increase the recovery rate of lithium element to more than 90%, and obtain high-purity lithium-containing products with a purity of more than 99.9% and graphite powder products meeting the battery-grade standards, which can improve the added value of the recycled products and meet the requirements for different lithium-containing products in industrial actual production.

[0067] Specifically, the volume ratio of the defluorination liquid to the carbon dioxide gas regulated in this application is 1:(25-40). Lithium ions are carbonized and converted into a lithium bicarbonate solution with a relatively high solubility. Compared with lithium carbonate, the solubility of lithium ions can be further increased, the loss of lithium ions can be reduced, and the recovery rate of lithium elements can be increased (about 95%). In particular, when the volume ratio of the two is regulated to 1:(28-33), the recovery rate of lithium elements can be further increased and the recovery efficiency can be improved (about 97%).

[0068] The above are only the preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the principles of this application shall be included within the protection scope of this 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; Wherein, the negative electrode material includes graphite and lithium; The temperature of the calcination treatment is T1°C, 300≤T1≤400; The step S1 further comprises: recovering the hydrogen generated in the water leaching lithium process by molecular sieve pressure swing adsorption; 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).

4. The recycling method according to claim 3, characterized in that: The volume ratio of the defluorination liquid to the carbon dioxide gas is 1:(28-33).

5. The recovery method according to any one of claims 1 to 4, characterized in that: In the step S1, the calcination time is t1 h, 0.5≤t1≤3.

0.

6. The recovery method according to any one of claims 1 to 4, characterized in that: The molecular sieve is at least one of type A zeolite molecular sieve, faujasite, and mordenite.

7. The recovery method according to any one of claims 1 to 4, 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.

8. The recycling method according to claim 7, 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.

9. The recycling method according to claim 8, characterized in that: 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.

10. The recovery method according to any one of claims 1 to 4, 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).

11. The recycling method according to any one of claims 1 to 4, characterized in that: In step S2, the cation exchange resin comprises At least one of CH-93 resin and 732 cation exchange resin; and / or the divalent and / or higher-valent metal ions include at least one of calcium ions, magnesium ions, iron ions, and aluminum ions.

12. 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.

13. 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.

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