Method for extracting lithium from negative electrode of waste lithium ion battery

Abstract

The invention provides a method for extracting lithium from a negative electrode of a waste lithium ion battery, and relates to the technical field of waste battery treatment.The method comprises the steps that 1, the waste negative electrode is subjected to first water leaching and solid-liquid separation, and negative electrode process water, a graphite-containing solid phase and a current collector sheet are obtained; (2) crystallizing the negative electrode process water obtained in the step (1) through a concentration scraper to obtain a lithium-containing concentrated mixture; (3) carbonizing the lithium-containing concentrated mixture obtained in the step (2) to obtain a lithium-containing carbonized material; and (4) carrying out second water leaching and solid-liquid separation on the lithium-containing carbonized material obtained in the step (3) to obtain a lithium hydroxide-containing solution. According to the method, leaching of the lithium element can be achieved only through water leaching, and the lithium leaching recovery rate reaches 95% or above.

Description

Technical Field

[0001] This invention relates to the field of waste battery recycling technology, and in particular to a method for extracting lithium from the negative electrode of waste lithium-ion batteries. Background Technology

[0002] The lithium battery dismantling and recycling process includes a crushing and pulverizing method, which comprises: cell discharge—whole crushing—material pyrolysis (pyrolysis and incineration of electrolyte, separator, and binder)—sorting of casing materials—mixing and pulverizing of electrode sheets—gravity sorting of copper foil, aluminum foil, and graphite powder. However, this process cannot separate the positive and negative electrode sheets, resulting in the mixed recycling of positive and negative electrode materials. The electrolyte and separator are not recycled, and the classification and recycling rate of lithium battery structural materials is less than 62%.

[0003] The refined dismantling and recycling process for lithium batteries, characterized by the dismantling of lithium batteries while they are in use, the separate processing of positive and negative electrode sheets, the full classification and recycling of positive and negative electrode materials, and the recycling and reuse of separators and electrolytes, represents a superior technical route for lithium battery recycling. Its classification and recycling rate of lithium battery structural materials reaches over 95%, and the water separation process for negative electrode materials can recover graphite powder and copper foil micro-flakes with a material recovery rate and purity of over 98%, significantly improving the resource recycling rate of lithium batteries.

[0004] However, the treatment of water used in the negative electrode material recycling process has brought new challenges: the recycling of process water used in the negative electrode material separation process and the resource utilization of process water.

[0005] Since the process of refining and recycling lithium batteries is still in the research stage, the water separation process of negative electrode materials is only one part of the process. The problem of resource recovery and water recycling without discharge in the treatment of negative electrode process water is a brand new challenge. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for extracting lithium from waste lithium-ion battery anodes, which can achieve efficient recovery of lithium from waste anodes at low cost and obtain battery-grade lithium carbonate.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for extracting lithium from the negative electrode of a spent lithium-ion battery, the recycling method comprising:

[0009] (1) The waste negative electrode is subjected to a first water immersion and solid-liquid separation to obtain negative electrode process water, graphite-containing solid phase and current collector sheet;

[0010] (2) The negative electrode process water in step (1) is subjected to a concentrated scraper crystallization treatment to obtain a lithium-containing concentrated mixture;

[0011] (3) The lithium-containing concentrated mixture described in step (2) is subjected to carbonization treatment to obtain lithium-containing carbonized material;

[0012] (4) The lithium-containing carbonized material in step (3) is subjected to a second water immersion and solid-liquid separation to obtain a lithium hydroxide solution.

[0013] The method for lithium extraction from waste lithium-ion battery negative electrodes provided by this invention has the following advantages:

[0014] 1. This recycling method only uses water immersion, without the need for acid or alkali immersion, which not only saves acid or alkali consumption, but also avoids the problem of difficult treatment of waste liquid after acid or alkali immersion.

[0015] 2. The present invention performs carbonization treatment on lithium-containing concentrated mixture, which can carbonize the organic matter in lithium-containing concentrated mixture. After carbonization, the carbonized carbide powder is subjected to a second water immersion in step (4) to obtain a lithium hydroxide solution that no longer contains organic matter, thereby realizing the preparation of lithium hydroxide solution in waste negative electrode. The lithium hydroxide solution can be used to prepare lithium carbonate or lithium hydroxide products.

[0016] It is worth noting that the source of the waste negative electrode in this invention can be the waste negative electrode disassembled from waste batteries.

[0017] The present invention does not have any special limitation on the disassembly. It can be done manually or by an automated machine to disassemble the negative electrode of the waste lithium-ion battery.

[0018] Preferably, the waste negative electrode in step (1) includes current collector sheet, adhesive, graphite and lithium.

[0019] It is worth noting that this invention does not have special requirements for the adhesive, and can use adhesives well known to those skilled in the art, such as polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), sodium alginate, polyaniline, polyimide (PI), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), or carboxymethyl cellulose (CMC). Generally, water-soluble adhesives are used.

[0020] It is worth noting that the binder in the negative electrode sheet is water-soluble, which allows the negative electrode graphite to separate from the current collector sheet in water. The binder in the negative electrode material dissolves in water, and the negative electrode graphite precipitates as powder. At the same time, since the lithium embedded in the negative electrode graphite is an active lithium ion, regardless of whether it is converted into lithium oxide, lithium nitride, lithium carbide or reduced to metallic lithium during the cell disassembly process, it can react spontaneously with water to generate lithium hydroxide solution, which dissolves into the negative electrode process water, forming a mixed solution for the negative electrode sheet water separation process.

[0021] In this invention, the lithium in the waste negative electrode can be lithium embedded in the graphite negative electrode.

[0022] Preferably, the current collector is made of copper or aluminum, with copper being the preferred material.

[0023] Preferably, the solid-liquid separation in step (1) includes first rinsing the mixture after the first water immersion and collecting the fluid sheet; then periodically cyclically performing pressure filtration and water immersion to obtain negative electrode process water and graphite-containing solid phase, respectively.

[0024] After a lithium battery is scrapped, it is usually in a charged state. Due to the working principle of lithium batteries, the lithium content in the negative electrode material is about 2.4wt% to 3.5wt% at this time. After the battery cell is disassembled, the negative electrode sheet is separated into three materials in water: graphite precipitate powder, copper foil micro-flakes, and negative electrode material separation process water containing dissolved binders (SBR+CMC, etc.) and lithium (hereinafter referred to as negative electrode process water). The graphite powder and copper foil micro-flakes are recovered after rinsing, filtering, and drying, respectively. However, the recovery of lithium resources in the negative electrode process water and the recycling of process water have become key technical links that urgently need to be solved.

[0025] It is worth noting that the number of cyclic filtration and water leaching cycles in this invention is not specifically limited, as long as the graphite-containing solid phase and the negative electrode process water are completely separated. For example, the material after collecting the fluid sheet is first subjected to primary filtration, the resulting primary filtration solid phase is then subjected to primary water leaching, the resulting mixture is then subjected to secondary filtration, and the resulting secondary filtration solid phase is then subjected to secondary water leaching. This can improve the lithium leaching rate from the graphite and reduce the proportion of lithium leaching water used, thereby obtaining negative electrode process water with a high lithium content and free of copper foil and graphite powder. The primary and secondary water leaching cycles are preferably performed using countercurrent leaching.

[0026] Preferably, the pH of the negative electrode process water in step (1) is 13~14, for example, it can be 13, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.8, 13.9 or 14, etc.

[0027] Preferably, the concentration of COD in the negative electrode process water in step (1) is 75,000~100,000 mg / L, for example, it can be 75,000 mg / L, 76,000 mg / L, 77,000 mg / L, 78,000 mg / L, 79,000 mg / L, 80,000 mg / L, 85,000 mg / L, 90,000 mg / L, 95,000 mg / L, 98,000 mg / L or 100,000 mg / L, etc.

[0028] Preferably, the lithium content in the negative electrode process water in step (1) is 15~22g / L, for example, it can be 15g / L, 16g / L, 17g / L, 18g / L, 19g / L, 20g / L, 21g / L or 22g / L, etc.

[0029] The negative electrode process water of this invention has a high COD concentration and a relatively low lithium content, making it impossible to directly recover lithium products.

[0030] In the concentrated scraper crystallization process of this invention, the evaporated water is simultaneously condensed and recovered. Approximately 80-90 wt% of the water is evaporated, condensed, and reused, approximately 5-10 wt% of the water vapor is volatilized, and the remaining approximately 5-10 wt% of the semi-solid first lithium-containing concentrated mixture is recovered.

[0031] Preferably, the temperature of the concentrated scraper crystallization process in step (1) is 40~60℃, for example, it can be 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃ or 60℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, in the concentrated scraper crystallization process, the lithium content in the lithium-containing concentrated mixture in step (1) is 10~15wt%, for example, it can be 10wt%, 10.6wt%, 11.2wt%, 11.7wt%, 12.3wt%, 12.8wt%, 13.4wt%, 13.9wt%, 14.5wt%, or 15wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the mass content of organic matter in the lithium-containing concentrated mixture in step (1) is 10~20wt%, for example, it can be 10wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] After the concentration scraper crystallization process, the mass content of organic matter in the lithium-containing concentrated mixture is within the above range. This indicates that during the concentration process, the concentration of organic matter continuously increases, which leads to a gradual increase in the viscosity of the overall material. The present invention uses the concentration scraper crystallization process to achieve continuous low-energy production.

[0035] Preferably, the organic matter in the lithium-containing concentrated mixture includes styrene-butadiene rubber and / or sodium carboxymethyl cellulose.

[0036] Preferably, the preparation method further includes mixing a lithium-containing concentrated mixture and a calcium source before the carbonization treatment in step (3).

[0037] In this application, to improve the subsequent lithium leaching rate, 5-15% calcium hydroxide or calcium oxide is added during the pyrolysis of the lithium-containing concentrated mixture, so that the small amount of lithium carbonate and lithium fluoride are causticized into lithium hydroxide. The possible chemical reaction equations are as follows:

[0038] 4LiOH + 2F₂ = 4LiF + O₂↑ + H₂O;

[0039] 4Li + 3CO₂ = 2Li₂CO₃ + C;

[0040] Li2CO3+Ca(OH)2→2LiOH+CaCO3↓;

[0041] 2LiF + Ca(OH)₂ → 2LiOH + CaF₂;

[0042] Adding a calcium source can increase the lithium extraction rate from around 90% to over 95%.

[0043] Preferably, the mass ratio of the calcium source to the lithium-containing concentrated mixture is 5 to 15 wt%, for example, it can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the calcium source includes calcium hydroxide and / or calcium oxide.

[0045] Preferably, the carbonization temperature in step (3) is 400~800℃, for example, it can be 400℃, 445℃, 480℃, 530℃, 570℃, 620℃, 660℃, 710℃, 750℃ or 800℃, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable. In this carbonization process, the organic matter is completely carbonized, and after a weight reduction of about 50% of the water content, a lithium-containing carbonized material is obtained.

[0046] Preferably, the carbonization process is carried out under an inert atmosphere.

[0047] Preferably, the inert atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium, wherein typical but non-limiting combinations are combinations of nitrogen and argon, helium and argon, nitrogen and helium, or helium, nitrogen, and argon.

[0048] Preferably, the lithium content in the lithium-containing carbide material in step (3) is 20~30wt%, for example, it can be 20wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt% or 30wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, in step (4), the mass ratio of lithium-containing carbide material to water in the second water immersion is 1:5 to 1:10, for example, it can be 1:5, 1:5.2, 1:5.3, 1:5.4, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or 1:10, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. During the second water immersion process, the lithium salt reacts fully with water to generate a lithium hydroxide solution for leaching. Since the organic matter of the negative electrode binder is carbonized and insoluble in water, a high-purity lithium hydroxide solution can be obtained after solid-liquid separation and impurity removal.

[0050] In this invention, the lithium hydroxide solution can be directly extracted to obtain battery-grade lithium carbonate without the addition of any substances, or the lithium hydroxide solution can be purified and concentrated into lithium hydroxide product in one step.

[0051] Preferably, the second immersion time is 0.5 to 2 hours, for example, it can be 0.5 hours, 0.7 hours, 0.9 hours, 1 hour, 1.2 hours, 1.4 hours, 1.5 hours, 1.7 hours, 1.9 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the second water immersion includes stirring and soaking.

[0053] Preferably, the stirring speed of the second water immersion is 100~400 r / min, for example, it can be 100 r / min, 120 r / min, 140 r / min, 150 r / min, 160 r / min, 170 r / min, 180 r / min, 200 r / min, 220 r / min, 250 r / min, 300 r / min, 320 r / min, 350 r / min or 400 r / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] Preferably, the second water immersion is carried out using multi-stage countercurrent immersion.

[0055] Preferably, the solid-liquid separation in step (4) further yields a second solid phase, which includes carbonized powder.

[0056] Preferably, the recovery method further includes: (5) sequentially extracting and back-extracting the lithium hydroxide solution to obtain a lithium bicarbonate solution, and then dehydrogenating and drying the lithium bicarbonate solution to obtain lithium carbonate.

[0057] The present invention does not impose any special limitations on the specific process flow and process parameters of the dehydrogenation precipitation, extraction and back-extraction, and process flow and parameters well known to those skilled in the art can be used.

[0058] For example, the dehydrogenation precipitation step in this invention includes: heating and stirring a lithium bicarbonate solution at 50-100°C at a stirring speed of 100-300 rpm to allow hydrogen to continuously evaporate and form lithium carbonate precipitate.

[0059] As a preferred embodiment of the present invention, the recycling method includes:

[0060] (1) Disassemble the waste battery to obtain the waste negative electrode. The waste negative electrode is first soaked in water. The resulting mixture is then rinsed and returned to the fluid collection plate. The mixture after returning to the fluid collection plate is then periodically circulated for pressure filtration and water soaking to obtain negative electrode process water with pH of 13~14 and graphite-containing solid phase, respectively. The COD concentration of the negative electrode process water is 75000~100000 mg / L and the lithium content is 15~22 g / L.

[0061] (2) The negative electrode process water in step (1) is subjected to a concentration scraper crystallization treatment at a temperature of 40~60℃ to obtain a lithium-containing concentrated mixture; the lithium-containing concentrated mixture contains 10~15wt% lithium and 10~20wt% organic matter.

[0062] (3) Mix the calcium source and the lithium-containing concentrated mixture in step (2), wherein the mass ratio of the calcium source to the lithium-containing concentrated mixture is 5 to 15 wt%, and carbonize the mixture at 400 to 800°C under an inert atmosphere to obtain a lithium-containing carbonized material with a lithium mass content of 20 to 30 wt%.

[0063] (4) The lithium-containing carbide material in step (3) is soaked in water for 0.5 to 2 hours. The mass ratio of the lithium-containing carbide material to water is 1:5 to 1:10. The second water soaking is carried out by multi-stage countercurrent soaking under stirring conditions of 100 to 400 r / min. Then, solid-liquid separation is performed to obtain a lithium hydroxide solution and carbide powder.

[0064] (5) The lithium hydroxide solution is extracted and back-extracted sequentially to obtain a lithium bicarbonate solution, and the lithium bicarbonate solution is dehydrogenated and dried to obtain lithium carbonate.

[0065] The present invention does not impose any special restrictions on the solid-liquid separation in the above process. Any device and method known to those skilled in the art for solid-liquid separation can be used. It can also be adjusted according to the actual process. For example, it can be filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0066] The present invention does not impose any special restrictions on the drying process described above. Any device and method known to those skilled in the art for drying can be used. Adjustments can also be made according to the actual process. For example, it can be air drying, vacuum drying, oven drying, or freeze drying, or a combination of different methods.

[0067] Compared with the prior art, the present invention has at least the following beneficial effects:

[0068] (1) The waste negative electrode recycling method provided by the present invention fully grasps the unique electrochemical characteristic of "embedded lithium ions" of negative electrode materials. It can quickly achieve lithium leaching by soaking in pure water. The lithium leaching process does not require the addition of acid or alkali. The process is simple, green and environmentally friendly, and easy to realize industrial production. Its lithium leaching recovery rate of negative electrode materials is ≥95%.

[0069] (2) In the waste negative electrode recycling method provided by the present invention, the negative electrode sheet water separation process removes copper foil by filtration and removes graphite powder by pressure filtration. After treatment, clear negative electrode process water is obtained. In addition to mainly using circulating distilled water and supplementing some industrial pure water, no other substances are used or added in this process. It can be called pure water lithium leaching, which avoids the introduction of other impurities besides the negative electrode material components. This lays a good foundation for simplifying the lithium extraction process and improving the lithium extraction quality.

[0070] (3) The carbonization treatment in the method for extracting lithium from the negative electrode of waste lithium-ion batteries provided by the present invention can completely carbonize the water-soluble binder in the lithium-containing concentrated mixture, and obtain lithium-containing carbonized material that no longer contains soluble organic matter, thus creating sufficient and necessary conditions for the implementation of subsequent water immersion lithium extraction process and direct extraction of battery-grade lithium carbonate from lithium hydroxide solution.

[0071] (4) The method for extracting lithium from the negative electrode of a spent lithium-ion battery provided by this invention can produce a pure lithium hydroxide refined solution using only the negative electrode material and water without adding any acid or alkali reagents. The lithium carbonate that meets battery-grade standards can be obtained in one step through an extraction process. The entire process route is simple, easy to operate and controllable, and suitable for large-scale industrial production. It has great significance in both the lithium battery dismantling, recycling and reuse industry and the lithium carbonate production industry. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of a method for extracting lithium from the negative electrode of a waste lithium-ion battery according to a specific embodiment of the present invention. Detailed Implementation

[0073] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0074] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0075] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0076] Those skilled in the art should understand that the present invention necessarily includes the necessary pipelines, conventional valves and general pump equipment for achieving complete process, but the above content is not the main inventive point of the present invention. Those skilled in the art can add layouts based on process flow and equipment structure selection, and the present invention does not make any special requirements or specific limitations in this regard.

[0077] As a specific embodiment of the present invention, a method for extracting lithium from the negative electrode of waste lithium-ion batteries is provided, such as... Figure 1 As shown, the method includes:

[0078] (1) Disassemble the waste battery to obtain the waste negative electrode. The waste negative electrode is first soaked in water. The resulting mixture is then rinsed and returned to the fluid collection plate. The mixture after returning to the fluid collection plate is then periodically circulated for pressure filtration and water soaking to obtain negative electrode process water with pH of 13~14 and graphite-containing solid phase, respectively. The COD concentration of the negative electrode process water is 75000~100000 mg / L and the lithium content is 15~22 g / L.

[0079] (2) The negative electrode process water in step (1) is subjected to a concentration scraper crystallization treatment at a temperature of 40~60℃ to obtain a lithium-containing concentrated mixture; the lithium-containing concentrated mixture contains 10~15wt% lithium and 10~20wt% organic matter.

[0080] (3) Mix the calcium source and the lithium-containing concentrated mixture in step (2), wherein the mass ratio of the calcium source to the lithium-containing concentrated mixture is 5 to 15 wt%, and carbonize the mixture at 400 to 800°C under an inert atmosphere to obtain a lithium-containing carbonized material with a lithium mass content of 20 to 30 wt%.

[0081] (4) The lithium-containing carbide material in step (3) is soaked in water for 0.5 to 2 hours. The mass ratio of the lithium-containing carbide material to water is 1:5 to 1:10. The second water soaking is carried out by multi-stage countercurrent soaking under stirring conditions of 100 to 400 r / min. Then, solid-liquid separation is performed to obtain a lithium hydroxide solution and carbide powder.

[0082] (5) The lithium hydroxide solution is extracted and back-extracted sequentially to obtain a lithium bicarbonate solution, and the lithium bicarbonate solution is dehydrogenated and dried to obtain lithium carbonate.

[0083] Example 1

[0084] This embodiment provides a method for lithium extraction from the negative electrode of a lithium-ion battery, the method comprising:

[0085] (1) Disassemble the waste battery to obtain the waste negative electrode. The waste negative electrode (lithium content is 3wt%) is first soaked in water. The resulting mixture is first rinsed and returned to the fluid collection plate. The mixture after returning to the fluid collection plate is then periodically circulated for pressure filtration and water immersion (first-stage pressure filtration, first-stage water immersion, second-stage pressure filtration and second-stage water immersion in sequence) to obtain negative electrode process water with pH 13.5 and graphite-containing solid phase, respectively. The COD concentration of the negative electrode process water is 75000mg / L and the lithium content is 15g / L.

[0086] (2) The negative electrode process water in step (1) is subjected to a concentration scraper crystallization treatment at a temperature of 40°C to obtain a lithium-containing concentrated mixture; the lithium-containing concentrated mixture contains 12 wt% lithium and 15 wt% organic matter.

[0087] (3) Mix calcium source (calcium hydroxide) and lithium-containing concentrated mixture from step (2), wherein the mass ratio of calcium source to lithium-containing concentrated mixture is 10 wt%, and carbonize at 500 °C under nitrogen atmosphere to obtain lithium-containing carbonized material with a lithium mass content of 20 wt%.

[0088] (4) The lithium-containing carbide material in step (3) is soaked in water for 1.5 hours. The mass ratio of the lithium-containing carbide material to water is 1:8. The second water soaking is carried out under the stirring condition of 100r / min using a 4-stage countercurrent soaking method. Then, it is filtered to obtain a lithium hydroxide solution and carbide powder.

[0089] (5) The lithium hydroxide solution is extracted and back-extracted sequentially to obtain a lithium bicarbonate solution, and the lithium bicarbonate solution is dehydrogenated and dried to obtain lithium carbonate.

[0090] Example 2

[0091] This embodiment provides a method for lithium extraction from the negative electrode of a lithium-ion battery, the method comprising:

[0092] (1) Disassemble the waste battery to obtain the waste negative electrode. The waste negative electrode (lithium content is 5wt%) is first soaked in water. The resulting mixture is first rinsed and returned to the fluid collection plate. The mixture after returning to the fluid collection plate is then periodically circulated for pressure filtration and water immersion (first-stage pressure filtration, first-stage water immersion, second-stage pressure filtration, second-stage water immersion, third-stage pressure filtration and third-stage water immersion in sequence) to obtain negative electrode process water with pH of 13.0 and graphite-containing solid phase respectively. The COD concentration of the negative electrode process water is 85000mg / L and the lithium content is 18g / L.

[0093] (2) The negative electrode process water in step (1) is subjected to a concentration scraper crystallization treatment at a temperature of 45°C to obtain a lithium-containing concentrated mixture; the lithium-containing concentrated mixture contains 10 wt% lithium and 11 wt% organic matter.

[0094] (3) Mix calcium source (calcium hydroxide) and the lithium-containing concentrated mixture in step (2), wherein the mass ratio of calcium source to lithium-containing concentrated mixture is 15wt%, and carbonize at 400°C under helium atmosphere to obtain lithium-containing carbonized material with a lithium mass content of 22wt%.

[0095] (4) The lithium-containing carbide material in step (3) is soaked in water for 0.5 hours. The mass ratio of the lithium-containing carbide material to water is 1:5. The second water soaking is carried out by three-stage countercurrent soaking under stirring conditions of 150 r / min. Then it is filtered to obtain a lithium hydroxide solution and carbide powder.

[0096] (5) The lithium hydroxide solution is extracted and back-extracted sequentially to obtain a lithium bicarbonate solution, and the lithium bicarbonate solution is dehydrogenated and dried to obtain lithium carbonate.

[0097] Example 3

[0098] This embodiment provides a method for lithium extraction from the negative electrode of a lithium-ion battery, the method comprising:

[0099] (1) Disassemble the waste battery to obtain the waste negative electrode. The waste negative electrode (lithium content is 6.5wt%) is subjected to a first water immersion. The resulting mixture is first rinsed and returned to the fluid collection plate. The mixture after returning to the fluid collection plate is then periodically circulated for pressure filtration and water immersion (first-stage pressure filtration, first-stage water immersion, second-stage pressure filtration and second-stage water immersion in sequence) to obtain negative electrode process water with pH 14.0 and graphite-containing solid phase, respectively. The COD concentration of the negative electrode process water is 90000mg / L and the lithium content is 20g / L.

[0100] (2) The negative electrode process water in step (1) is subjected to a concentration scraper crystallization treatment at a temperature of 55°C to obtain a lithium-containing concentrated mixture; the lithium-containing concentrated mixture contains 15 wt% lithium and 20 wt% organic matter.

[0101] (3) Mix calcium source (calcium oxide) and the lithium-containing concentrated mixture in step (2), wherein the mass ratio of calcium source to lithium-containing concentrated mixture is 5 wt%, and carbonize at 800°C under helium atmosphere to obtain lithium-containing carbonized material with a lithium mass content of 25 wt%.

[0102] (4) The lithium-containing carbide material in step (3) is soaked in water for 2 hours. The mass ratio of the lithium-containing carbide material to water is 1:10. The second water soaking is carried out under the stirring condition of 220r / min using a three-stage countercurrent soaking method. Then it is filtered to obtain a lithium hydroxide solution and carbide powder.

[0103] (5) The lithium hydroxide-containing solution is evaporated and concentrated to obtain the lithium hydroxide product.

[0104] Example 4

[0105] This embodiment provides a method for lithium extraction from the negative electrode of a lithium-ion battery. Except for step (3), in which a calcium source is not added, the method is the same as that in embodiment 1.

[0106] Comparative Example 1

[0107] This comparative example provides a method for extracting lithium from the negative electrode of a waste lithium-ion battery. The method is the same as in Example 1 except that steps (2) to (5) are omitted, and carbon dioxide is directly introduced into the negative electrode process water obtained in step (1) until the pH drops to 9 in order to prepare a precipitate containing lithium carbonate.

[0108] Both Li and the binder (such as SBR+CMC) in the negative electrode are soluble in water: the Li content is approximately 15~22 g / L, and the COD content is approximately 75000~100000 mg / L. The chemical reaction equations occurring in the system are as follows: 2Li + 2H2O = 2LiOH + H2↑; Li2O + H2O = 2LiOH; Li3N + 3H2O = 3LiOH + NH3↑; LiF + H2O ↔ HF + LiOH.

[0109] Since the ratio of Li content to binder content in the separated water is approximately 1:1, it is difficult to initiate the reaction of low-concentration lithium hydroxide to lithium carbonate precipitate by introducing carbon dioxide into the negative electrode process water containing a large amount of organic matter. Even if a trace amount of lithium carbonate precipitate occurs, the recovery rate of lithium in the filtrate and the purity of extracted lithium carbonate are not of practical application value.

[0110] Test methods: The lithium content in the waste negative electrode is tested according to YS / T1342.4-2019, and the lithium content in the lithium hydroxide solution is tested according to GB / T17413.1-2010. The lithium recovery rate is recorded as the ratio of the lithium content (absolute mass) in the lithium hydroxide solution to the lithium content (absolute mass) in the waste negative electrode. The purity of the lithium hydroxide solution is tested according to GB / T11064.2-2023. Substances other than lithium hydroxide and water in the lithium hydroxide solution are considered impurities.

[0111] The test results of the above embodiments are shown in Table 1.

[0112] Table 1

[0113]

[0114] As can be seen from Table 1:

[0115] (1) As can be seen from the comprehensive examples 1 to 3, the method for extracting lithium from the negative electrode of waste lithium-ion batteries provided by the present invention has a simple process route, is easy to operate and controllable, and is suitable for large-scale industrial production. It has great significance in the lithium battery dismantling, recycling and reuse industry and the lithium carbonate production industry. Moreover, the lithium recovery rate is above 95%, and the purity of lithium hydroxide monohydrate in the lithium hydroxide solution is above 98%.

[0116] (2) As can be seen from the combined examples 1 and 4, the present invention can further improve the lithium recovery rate by preferentially adding calcium source.

[0117] Table 2 shows a comparison between the cost of preparing lithium carbonate using the waste negative electrode recycling method provided by this invention and the existing lithium carbonate preparation costs.

[0118] Table 2

[0119]

[0120] The processes of the present invention in Table 2 are calculated based on Examples 1-3. The process for extracting lithium from ore is based on the sulfuric acid process, and the process for extracting lithium from salt lakes is based on the solvent extraction process.

[0121] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for extracting lithium from a spent lithium-ion battery negative electrode, characterized in that, The recycling method comprises: (1) the waste negative electrode is subjected to first water immersion and solid-liquid separation to obtain negative electrode process water, graphite-containing solid phase and current collector sheet; (2) the negative electrode process water in step (1) is subjected to concentrated scraper crystallization treatment to obtain lithium-containing concentrated mixture; (3) the lithium-containing concentrated mixture in step (2) is subjected to carbonization treatment to obtain lithium-containing carbonized material; (4) the lithium-containing carbonized material in step (3) is subjected to second water immersion and solid-liquid separation to obtain lithium hydroxide-containing solution.

2. The method of claim 1, wherein, The waste negative electrode in step (1) comprises current collector sheet, adhesive, graphite and lithium; Preferably, the solid-liquid separation in step (1) comprises first rinsing the mixture after first water immersion to recover the current collector sheet, and then periodically and cyclically performing filter pressing and water immersion to obtain negative electrode process water and graphite-containing solid phase, respectively.

3. The method according to claim 1 or 2, characterized in that, The pH of the negative electrode process water in step (1) is 13-14.

4. The method of claim 1, wherein, The temperature of the concentrated scraper crystallization treatment in step (1) is 40-60℃.

5. The method of claim 1, wherein, The mass content of lithium in the lithium-containing concentrated mixture in step (1) is 10-15wt%.

6. The method according to claim 1 or 5, characterized in that, The mass content of organic matter in the lithium-containing concentrated mixture in step (1) is 10-20wt%.

7. The method according to claim 1 or 5, characterized in that, The preparation method further comprises, before the carbonization treatment in step (3): mixing the lithium-containing concentrated mixture and calcium source; Preferably, the mass ratio of the calcium source to the lithium-containing concentrated mixture is 5-15wt%; Preferably, the calcium source comprises calcium hydroxide and / or calcium oxide; Preferably, the temperature of the carbonization treatment in step (3) is 400-800℃; Preferably, the carbonization treatment is performed in inert atmosphere.

8. The method of claim 1, wherein, The mass content of lithium in the lithium-containing carbonized material in step (3) is 20-30wt%.

9. The method of claim 1, wherein, The mass ratio of the lithium-containing carbonized material to water in the second water immersion in step (4) is 1:5-1:10; The second water immersion is performed for 0.5-2h. Preferably, the second water immersion comprises stirring immersion; Preferably, the stirring speed of the second water immersion is 100-400r / min; Preferably, the second water immersion is performed by multi-stage countercurrent immersion; Preferably, the solid-liquid separation in step (4) further obtains second solid phase, and the second solid phase comprises carbonized powder.

10. The method of claim 1, wherein, The recycling method further comprises: (5) sequentially performing extraction and back extraction on the lithium hydroxide-containing solution to obtain lithium bicarbonate solution, and performing dehydrogenation precipitation and drying on the lithium bicarbonate solution to obtain lithium carbonate.

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