Lithium battery negative electrode comprehensive recovery method based on carbon thermal shock and oxidation impurity removal

Abstract

The invention discloses a lithium battery negative electrode comprehensive recovery method based on carbon thermal shock and oxidation impurity removal, and relates to the technical field of lithium battery negative electrode comprehensive recovery. According to the method, carbon thermal shock is applied to negative electrode graphite powder in an inert atmosphere, so that intercalated lithium is converted into a water-soluble lithium compound; the method comprises the following steps: carrying out multistage countercurrent water leaching to obtain a lithium-containing water leaching solution, separating coarse graphite, adding carbonate ions into the water leaching solution to obtain a lithium carbonate primary precipitate, carrying out hydrotreating to convert the lithium carbonate primary precipitate into soluble lithium bicarbonate, and carrying out heating decomposition to obtain a high-purity lithium carbonate secondary precipitate; introducing sodium fluoride into the mother liquor after the two times of lithium carbonate precipitation to precipitate and recover residual lithium; carrying out oxidation impurity removal on the coarse graphite under a weak acid condition; and finally, the pH value of the impurity removal liquid is adjusted, and metal copper is replaced and recycled through reduced iron powder. The method gives consideration to the purity of the lithium carbonate product and the recovery rate of lithium, obtains high-purity graphite and the byproduct copper, and has the advantages of high recovery efficiency, low water consumption, high material utilization rate and the like.

Description

Technical Field

[0001] This invention relates to the field of comprehensive recycling technology for lithium battery anodes, and in particular to a comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal. Background Technology

[0002] Currently, the recycling of spent lithium-ion batteries mainly focuses on the high-value cathode metals, while the recycling of anode materials is mostly limited to copper foil, with insufficient attention paid to the regeneration and utilization of graphite resources. Efficient recycling of graphite materials from retired batteries could significantly reduce energy consumption and carbon dioxide emissions in primary graphite production, achieving resource recycling.

[0003] In recent years, carbothermal shock, a Joule-based processing method, has shown significant advantages in battery recycling and material processing by instantaneously heating the conductive framework with electricity, enabling materials to heat up ultrafastly within milliseconds to seconds. This method preferentially converts lithium in graphite into soluble lithium compounds, achieving selective separation of lithium resources from graphite and providing new possibilities for the integrated recycling of graphite anodes. However, the application of carbothermal shock in retired lithium-ion batteries primarily focuses on graphite regeneration, but the release of the lithium-intercalated phase and the subsequent integration of water leaching for lithium extraction and acid leaching for impurity removal remain insufficient. Furthermore, the copper current collector in the graphite of retired batteries also needs to be recovered independently. Traditional oxidation-acid leaching systems are highly oxidizing under acidic conditions, exhibiting non-selective oxidation of graphite. This easily etches the substrate and edges, induces interlayer delamination and increases defects, weakens the orderliness of layered stacking and the continuity of current-carrying channels, thereby reducing conductivity and structural integrity, which is detrimental to obtaining high-quality, consistent regenerated graphite.

[0004] Therefore, there is an urgent need to introduce a mild and stable oxidant to replace traditional strong oxidants such as hydrogen peroxide, to assist acid leaching in the efficient removal of metallic impurities from graphite while maintaining the structural integrity of the graphite. This would allow for the development of a green recycling process that integrates selective lithium separation, efficient impurity removal, and graphite regeneration. To address these issues, we have designed a comprehensive lithium battery anode recycling method based on carbon thermal shock and oxidation impurity removal. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation removal, which is efficient, convenient, low-energy, and can maintain the layered order and conductivity continuity of graphite. By combining Joule thermal carbon thermal shock (CTS) with water immersion for preferential lithium extraction, combined with selective oxidant removal and copper current collector recovery, the main process of lithium priority recovery, subsequent impurity removal, and copper metal recovery is achieved, and lithium, copper resources and high-quality recycled graphite are obtained simultaneously.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal includes the following steps:

[0008] Step S1: Apply carbon thermal shock to the graphite powder of the negative electrode of waste lithium battery, add the graphite powder after carbon thermal shock treatment to deionized water at a certain liquid-solid ratio, continuously stir and leach, and obtain lithium-containing water leachate and coarse graphite solid after solid-liquid separation.

[0009] Step S2: The lithium-containing water leaching solution is treated using a multi-stage countercurrent water leaching process. The lithium-containing water leaching solution is passed sequentially through the nth to the 1st stage leaching unit. The filtrate from each leaching unit is returned to the previous higher-order leaching unit in the opposite direction. Fresh water is added to the nth stage leaching unit to form a concentration gradient drive.

[0010] Step S3: Sodium carbonate is added to the lithium-containing aqueous leaching solution to allow lithium ions to combine with carbonate ions to form a primary lithium carbonate precipitate. The primary lithium carbonate precipitate is then converted into lithium bicarbonate by hydrogenation and further decomposed by heating to obtain a secondary lithium carbonate precipitate.

[0011] Step S4: Immerse the crude graphite solid in a weak acid solution and add an oxidant to remove iron and copper impurities, thereby obtaining a purified graphite solid phase and a leachate.

[0012] Step S5: Add an alkaline solution to the leachate to adjust the pH of the leachate to 3.5~4.5, so that the ferric ions are hydrolyzed and precipitated and filtered. Then, add reduced iron powder to the filtrate to replace the metallic copper. After liquid-solid separation and acid washing, remove the remaining reduced iron powder.

[0013] As a further preferred embodiment of the present invention, the method of applying carbon thermal shock to the graphite powder of the negative electrode of waste lithium batteries is as follows:

[0014] In an inert atmosphere, a heating method based on the Joule heating effect is used, with a heating rate of no less than 1000 degrees Celsius / second, to heat the graphite powder of the negative electrode of waste lithium batteries to 800 degrees Celsius to 1200 degrees Celsius and hold it for 5 to 30 seconds.

[0015] As a further preferred embodiment of the present invention, the graphite powder treated with carbon thermal shock is added to deionized water at a certain liquid-to-solid ratio, wherein the liquid-to-solid ratio of graphite powder to deionized water is […]. The temperature of the deionized water is 60 degrees Celsius, and the stirring time is 120 minutes.

[0016] As a further preferred embodiment of the present invention, the lithium-containing water immersion solution is treated using a multi-stage countercurrent water immersion process, including:

[0017] An n-stage leaching unit is used, in which the lithium-containing aqueous solution is passed sequentially through the nth to the 1st stage leaching unit. After each stage leaching unit comes into contact with the lithium-containing aqueous solution, liquid-solid separation is performed. The filter residue obtained from each stage leaching unit is sent to the next lower-numbered leaching unit for continued countercurrent washing. Fresh water is added to the nth stage leaching unit. The filtrate from each stage leaching unit flows back to the previous higher-numbered leaching unit in the opposite direction, forming a concentration gradient to drive the dilution of soluble lithium ions in the lithium-containing aqueous solution and reduce the residual lithium in the lithium-containing aqueous solution during liquid-solid separation.

[0018] As a further preferred embodiment of the present invention, the addition of sodium carbonate to the lithium-containing aqueous leaching solution, wherein lithium ions combine with carbonate ions to form a primary lithium carbonate precipitate, comprises:

[0019] Under stirring conditions, sodium carbonate was added to a lithium-containing aqueous leaching solution, with a molar ratio of lithium ions to carbonate ions of 1:1.2. The reaction temperature was controlled at 60 degrees Celsius and the reaction time was controlled at 60 minutes, so that lithium ions and carbonate ions could combine to form a primary precipitate of lithium carbonate.

[0020] As a further preferred embodiment of the present invention, the lithium carbonate primary precipitate is converted into lithium bicarbonate by hydrogenation treatment, and the lithium carbonate secondary precipitate is obtained by heating decomposition as follows:

[0021] After collecting the primary lithium carbonate precipitate through solid-liquid separation, it is added to deionized water to prepare a suspension. Carbon dioxide gas is then introduced under stirring conditions for chemical treatment, converting lithium carbonate into lithium bicarbonate. The resulting lithium bicarbonate solution is then separated by standing or filtration, and the unreacted residue in the lithium bicarbonate solution is discarded to obtain a clear filtrate containing lithium bicarbonate. The clear filtrate is then heated and evaporated, causing the lithium bicarbonate in the clear filtrate to decompose and generate a secondary lithium carbonate precipitate.

[0022] As a further preferred embodiment of the present invention, in step S3, sodium fluoride is added to the lithium removal mother liquor generated during the production of primary and secondary lithium carbonate precipitation reactions. The amount of sodium fluoride added is 1.2 to 1.5 times the theoretical amount of the lithium removal mother liquor, so that the residual lithium in the lithium removal mother liquor is precipitated and recovered in the form of lithium fluoride.

[0023] As a further preferred embodiment of the present invention, the crude graphite solid is soaked in a weak acid solution with a pH value of 1.5 to 2.5;

[0024] The oxidant is a soluble ferric salt, which oxidizes and removes copper and iron impurities from the crude graphite solid, obtaining a purified graphite solid phase and a leachate.

[0025] As a further preferred embodiment of the present invention, the soluble trivalent iron salt is any one of ferric chloride, ferric sulfate, or ferric nitrate.

[0026] As a further preferred embodiment of the present invention, in step S5, the alkaline solution added to the leachate is any one of sodium hydroxide solution, potassium hydroxide solution, or ammonia water.

[0027] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses ferric salts as the impurity removal oxidant. Due to its weak oxidizing properties, it avoids the excessive generation of oxygen-containing functional groups on the surface of graphite particles, replacing traditional strong oxidants such as hydrogen peroxide. It assists in the efficient removal of metallic impurities from graphite through acid leaching. It exhibits higher stability under acidic conditions, enabling it to continuously exert its oxidizing effect, thus improving impurity removal efficiency and process stability. Simultaneously, it avoids the damage to the graphite structure caused by hydrogen peroxide and the bubble generation and safety hazards resulting from its decomposition, thus possessing better industrial applicability. This invention uses carbothermal shock to convert the lithium phase in graphite into soluble lithium compounds, followed by preferential recovery of lithium through neutral or near-neutral water leaching. Then, under mild conditions, metallic impurities are selectively removed and the copper current collector is recovered. This design provides an environmentally friendly recycling method that can selectively separate lithium, remove impurities, and recycle graphite. It achieves process separation of "lithium recovery first, impurity removal later," ensuring that the two stages do not interfere with each other, improving the purity of lithium salts and the consistency of recovery. At the same time, the process is simple, easy to control, and helps maintain the structural integrity of graphite. Attached Figure Description

[0028] Figure 1 This is a flowchart of the comprehensive recycling method for lithium battery anode based on carbon thermal shock and oxidation impurity removal in the embodiments of the present invention; Figure 2 This is a bar chart of lithium ion leaching rate under different impact temperatures in the embodiments of the present invention; Figure 3 This is a bar chart showing the lithium ion leaching rate under different heat preservation times in the embodiments of the present invention; Figure 4 This is a graph showing the effect of different temperatures on the purity of lithium carbonate precipitation in embodiments of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the specific embodiments of this invention will be described in detail below with reference to the accompanying drawings. These embodiments are merely preferred examples of this invention, used to aid in understanding the inventive concept, and do not constitute a limitation on the scope of protection.

[0030] Graphite has become the primary anode material for commercial lithium-ion batteries due to its low cost, excellent conductivity, low operating voltage, and high theoretical capacity. With the rapid development of the electric vehicle industry, it is estimated that approximately 4 million tons of waste graphite anode material will be generated from retired lithium-ion batteries by 2030. However, the preparation of battery-grade graphite (purity >99.5%) still relies on traditional processes that are energy-intensive and highly polluting. Therefore, the comprehensive recycling of lithium-ion battery anodes urgently requires the development of green and efficient regeneration methods.

[0031] Example 1

[0032] This embodiment proposes a comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal. The recycling method includes the following steps:

[0033] Step S1: Apply carbon thermal shock to the graphite powder of the waste lithium battery negative electrode to promote lithium intercalation (… The inorganic lithium phase (such as LiF) in the SEI layer decomposes or transforms into water-soluble lithium compounds and accumulates on the particle surface, so as to facilitate subsequent selective lithium extraction by water leaching.

[0034] Graphite powder treated with carbothermal shock was added to deionized water at a certain liquid-to-solid ratio and continuously stirred for leaching. After solid-liquid separation, lithium-containing aqueous solution and coarse graphite solid were obtained.

[0035] The method for applying carbon thermal shock to graphite powder from the negative electrode of spent lithium batteries is as follows:

[0036] Under an inert atmosphere (nitrogen atmosphere), a heating method based on the Joule heating effect is used to rapidly heat the material in a very short time and maintain it at a high temperature for a set time. The heating rate used is no less than 1000 degrees Celsius / second, which heats the graphite powder of waste lithium battery negative electrode to 800 degrees Celsius to 1200 degrees Celsius and holds it for 5 to 30 seconds, thereby achieving rapid phase transition of lithium compounds.

[0037] Graphite powder treated with carbothermal shock was added to deionized water at a specific liquid-to-solid ratio. The liquid-to-solid ratio of graphite powder to deionized water was: The temperature of the deionized water was 60℃, and the stirring time was 120 minutes. After solid-liquid separation, lithium-containing water immersion solution and crude graphite solid were obtained.

[0038] Step S2: The lithium-containing water leaching solution is treated using a multi-stage countercurrent water leaching process. The lithium-containing water leaching solution is passed sequentially through the nth to the 1st stage leaching unit. The filtrate from each leaching unit is returned to the next higher-numbered leaching unit in the opposite direction. Fresh water is added to the nth stage leaching unit so that the fresh water is always in contact with the solid with the lowest lithium concentration, forming a concentration gradient to drive the maximum dissolution of residual lithium salts.

[0039] In this step, the lithium-containing water immersion solution is treated using a multi-stage countercurrent water immersion process, which includes:

[0040] An n-stage leaching unit (n = 3 to 6, preferably 4 to 5) is used. The lithium-containing aqueous leaching solution is passed sequentially through the nth to the 1st stage leaching unit. After contact with the lithium-containing aqueous leaching solution, liquid-solid separation is performed in each leaching unit. The filter residue obtained from each leaching unit is sent to the next lower-numbered leaching unit for continued countercurrent washing. Fresh water is added to the nth stage leaching unit. The filtrate from each leaching unit flows back to the previous higher-numbered leaching unit in the opposite direction, forming a concentration gradient. This can fully dilute the soluble lithium ions in the lithium-containing aqueous leaching solution, reduce the residual lithium in the lithium-containing aqueous leaching solution during liquid-solid separation, and thus improve the lithium recovery rate.

[0041] Step S3: Add sodium carbonate to the lithium-containing aqueous leaching solution to reduce lithium ions ( ) and carbonate ions ( ) combine to form lithium carbonate ( Primary precipitation, followed by lithium carbonate ( The primary precipitate is converted into a soluble intermediate, lithium bicarbonate, through hydrogenation. High-purity lithium carbonate is obtained through heating and decomposition. Secondary precipitation;

[0042] It should be noted that adding sodium carbonate to a lithium-containing aqueous leaching solution will reduce the lithium ion concentration (...). ) and carbonate ions ( ) combine to form lithium carbonate ( Primary precipitation, the operation of which includes:

[0043] Under stirring conditions, sodium carbonate is added to a lithium-containing aqueous leaching solution, and lithium ions ( ) and carbonate ions ( The molar ratio of lithium ions to carbonate ions was 1:1.2, and the reaction temperature was controlled at 60 degrees Celsius and the reaction time was controlled at 60 minutes, so that lithium ions and carbonate ions could combine to form lithium carbonate. Primary precipitation.

[0044] Lithium carbonate ( The primary precipitate is converted into a soluble intermediate, lithium bicarbonate, through hydrogenation. High-purity lithium carbonate is obtained through heating and decomposition. The procedure for secondary precipitation is as follows:

[0045] Lithium carbonate ( After the primary precipitate is collected through solid-liquid separation, deionized water is added to the separated liquid to prepare a suspension. Carbon dioxide gas is then introduced under stirring to treat the suspension, converting lithium carbonate into soluble lithium bicarbonate. The resulting soluble lithium bicarbonate solution is then separated by standing or filtration, and unreacted residues are discarded, yielding a clear filtrate containing lithium bicarbonate. This clear filtrate is then heated and evaporated (or decomposed by blowing in air), causing the lithium bicarbonate in the clear filtrate to decompose and generate high-purity lithium carbonate. Secondary precipitation yields lithium carbonate ( ) Primary precipitation and lithium carbonate ( After filtration, washing and drying, the secondary precipitate can be used to obtain high-purity lithium carbonate products.

[0046] In the production of lithium carbonate ( Primary precipitation and lithium carbonate ( Sodium fluoride (NaF) is added to the lithium removal mother liquor produced during the secondary precipitation reaction. The amount of sodium fluoride (NaF) added is 1.2 to 1.5 times (molar ratio) of the theoretical amount of lithium removal mother liquor. This causes the residual lithium in the lithium removal mother liquor to precipitate and be recovered as lithium fluoride (LiF), thereby achieving battery-grade lithium carbonate (LiF). Preparation and efficient recovery of residual lithium.

[0047] Step S4: Immerse the crude graphite solid in a weak acid solution and add an oxidant to remove iron and copper impurities, thereby obtaining a purified graphite solid phase and a leachate.

[0048] Crude graphite solid is soaked in a weakly acidic solution with a pH of 1.5-2.5; the oxidant is a soluble ferric salt, which oxidizes and removes copper and iron impurities from the crude graphite solid, obtaining a purified graphite solid phase and a leachate. The soluble ferric salt can be any one of ferric chloride, ferric sulfate, or ferric nitrate; the oxidant, using a soluble ferric salt, can oxidize and remove copper and iron impurities from the crude graphite solid; the graphite after the above acid leaching purification is subjected to multi-stage water washing and liquid-solid separation to obtain high-purity graphite; simultaneously, ferric ions (… Due to its weak oxidizing properties, it avoids the formation of a large number of oxygen-containing functional groups on the surface of graphite particles, thereby maintaining the integrity of the graphite structure.

[0049] Step S5: Add an alkaline solution to the leachate. The alkaline solution can be any one of sodium hydroxide solution (NaOH), potassium hydroxide solution (KOH), or ammonia water. Adjust the pH of the leachate to 3.5~4.5 to hydrolyze and precipitate ferric ions and filter. Then add reduced iron powder to the filtrate to replace the metallic copper. After liquid-solid separation and acid washing to remove the remaining reduced iron powder, high-purity copper is recovered.

[0050] Example 2

[0051] A pulsed current was applied to the graphite negative electrode of spent lithium batteries in an inert atmosphere, raising the material temperature to 800°C–1200°C within 5 seconds and maintaining it at that temperature for 20 seconds; subsequently, a pulsed current was applied at a temperature ≥ The cooling rate is reduced to room temperature. During this process, residual lithium compounds (such as LiC6, LiF, ...) in the negative electrode graphite are removed. Some of these species are converted into easily soluble species.

[0052] The graphite powder after carbothermal shock treatment was categorized according to the liquid-solid ratio. The sample was added to deionized water at 60℃ and leached with continuous stirring for 120 minutes. After solid-liquid separation, a lithium-containing aqueous solution and coarse graphite solid were obtained. The results of lithium-ion leaching rates under different impact temperatures are as follows: Figure 2 As shown, the lithium ion leaching rate in the leachate reached 98.13%.

[0053] Impurity removal treatment for coarse graphite solids: A dilute sulfuric acid solution was used as the main component, with the addition of 0.03 mol of ferric chloride. The reaction was carried out at 80℃ for 240 min to remove impurity ions such as copper (Cu) and iron (Fe). After washing and drying, the purified graphite was digested. The test results are shown in Table 1. The iron content in the graphite powder was less than 20 ppm, and the copper content was completely removed.

[0054] Table 1. Detection results of metallic impurities in graphite powder after purification and digestion under reaction conditions at 80℃.

[0055]

[0056] Example 3

[0057] A pulsed current was applied to the graphite anode material of spent lithium-ion batteries in an inert atmosphere, causing the temperature of the graphite material to rise to 1000°C within no more than 5 seconds, and maintaining this temperature for 10 to 60 seconds; subsequently, a pulsed current was applied at a temperature ≥ The cooling rate is reduced to room temperature. During this process, residual lithium compounds (such as LiC6, LiF, ...) in the negative electrode graphite are removed. Some of these species are converted into easily soluble species.

[0058] The graphite powder after carbothermal shock treatment was categorized according to the liquid-solid ratio. The solution was added to deionized water at 60℃ and stirred for 120 minutes. After solid-liquid separation, a lithium-containing leachate and crude graphite solid were obtained. The lithium-ion leaching rates under different holding times are shown below. Figure 3 As shown, the leaching rate of lithium ions in the leachate reached 95%.

[0059] Coarse graphite solids A dilute sulfuric acid solution was used, with the addition of 0.02 mol of ferric chloride, and the reaction was carried out at 60℃ for 240 min to remove metallic impurities such as copper and iron. After washing and drying, the purified graphite was digested, and the test results are shown in Table 2. The content of metallic iron in the graphite powder was less than 50 ppm, and metallic copper was completely removed.

[0060] Table 2. Detection results of impurities in graphite powder after purification and digestion under reaction conditions at 60℃.

[0061]

[0062] Example 4

[0063] A pulsed current was applied to the graphite anode of spent lithium batteries in an inert atmosphere, raising the material temperature to 1200°C within 5 seconds and maintaining it at that temperature for 10 seconds; subsequently, a pulsed current was applied at a rate ≥ The cooling rate drops to room temperature.

[0064] The graphite powder after carbothermal shock treatment was categorized according to the liquid-solid ratio. Add to 60℃ deionized water, stir and leach for 120 min, and separate the solid and liquid to obtain lithium-containing aqueous leachate and crude graphite solid.

[0065] coarse graphite solids A dilute sulfuric acid solution was prepared, and 0.05 mol of ferric chloride was added. The mixture was reacted at 70°C for 240 min to remove impurities such as copper (Cu) and iron (Fe). After washing and drying, the purified graphite was digested. The test results are shown in Table 3. The content of metallic iron in the graphite powder was less than 80 ppm, and metallic copper was completely removed.

[0066] Table 3. Detection results of impurities in graphite powder after purification and digestion under reaction conditions at 70℃.

[0067]

[0068] Example 5

[0069] Take the lithium-containing aqueous solution obtained through the aforementioned process step S2, and add sodium carbonate to the solution under stirring conditions, so that... and The molar ratio was approximately 1:1.2, and the reaction temperature was controlled at 60°C for 60 minutes, allowing lithium ions to react with carbonate ions to form lithium carbonate precipitate. Testing showed that the precipitation rate of the obtained lithium carbonate reached approximately 92.25%.

[0070] The primary lithium carbonate precipitate was separated into solid and liquid components to obtain filter residue, which was then prepared into a homogeneous suspension using deionized water; the suspension was maintained at a liquid-to-solid ratio of 25:1 and a stirring speed of [missing information]. At a temperature of 20°C, carbon dioxide is introduced to partially hydrogenate lithium carbonate to form soluble lithium bicarbonate. + + → 2 The conversion rate was approximately 87.28%. After the reaction was completed, unreacted residues were removed by standing or filtration to obtain a clear filtrate containing lithium bicarbonate. Subsequently, the clear filtrate was heated and evaporated, causing the lithium bicarbonate to thermally decompose and redefine high-purity lithium carbonate as a secondary precipitate, while releasing carbon dioxide and water. The secondary lithium carbonate precipitate was filtered, washed, and dried to obtain the high-purity lithium carbonate product.

[0071] To further improve product purity, the clarified filtrate of lithium bicarbonate was... Pyrolysis was carried out under stirring at temperatures of 60°C, 70°C, 80°C, 90°C, and 95°C for 60 min, respectively (2) → ↓ + ↑ + ).like Figure 4 As shown, temperature has a significant impact on the purity of lithium carbonate precipitation; under the conditions of this study, the purity of lithium carbonate precipitation reached its highest level of 99.77% at 90℃. After pyrolysis, high-purity lithium carbonate can be obtained through solid-liquid separation, washing, and drying.

[0072] The above embodiments detail the specific process flow and preferred conditions of the present invention, including steps such as stripping of waste lithium-ion battery negative electrode sheets, carbon thermal shock conversion, selective leaching in water, lithium precipitation in lithium-containing solution, and graphite impurity removal and repair. Examples of different processing parameters (temperature, time, leaching conditions, impurity removal methods, etc.) demonstrate that the method of the present invention is applicable to various retired battery negative electrode materials and can achieve high lithium-ion leaching rates and graphite repair effects.

[0073] Although the steps in the above embodiments are described in the above order, those skilled in the art will understand that in order to achieve the effect of this embodiment, different steps do not need to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple variations are all within the protection scope of this invention.

[0074] Those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims of this invention, any of the claimed embodiments can be used in any combination.

[0075] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it should be noted that the parts not covered in this invention are the same as or can be implemented using existing technology. It will be readily understood by those skilled in the art that the scope of protection of this invention is obviously not limited to these specific embodiments. Without departing from the principles of this invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions resulting from these changes or substitutions will all fall within the scope of protection of this invention.

Claims

1. A comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal, characterized in that, The steps include the following: Step S1: Apply carbon thermal shock to the graphite powder of the negative electrode of waste lithium battery, add the graphite powder after carbon thermal shock treatment to deionized water at a certain liquid-solid ratio, continuously stir and leach, and obtain lithium-containing water leachate and coarse graphite solid after solid-liquid separation. Step S2: The lithium-containing water leaching solution is treated using a multi-stage countercurrent water leaching process. The lithium-containing water leaching solution is passed sequentially through the nth to the 1st stage leaching unit. The filtrate from each leaching unit is returned to the previous higher-order leaching unit in the opposite direction. Fresh water is added to the nth stage leaching unit to form a concentration gradient drive. Step S3: Sodium carbonate is added to the lithium-containing aqueous leaching solution to allow lithium ions to combine with carbonate ions to form a primary lithium carbonate precipitate. The primary lithium carbonate precipitate is then converted into lithium bicarbonate by hydrogenation and further decomposed by heating to obtain a secondary lithium carbonate precipitate. Step S4: Immerse the crude graphite solid in a weak acid solution and add an oxidant to remove iron and copper impurities, thereby obtaining a purified graphite solid phase and a leachate. Step S5: Add an alkaline solution to the leachate to adjust the pH of the leachate to 3.5~4.5, so that the ferric ions are hydrolyzed and precipitated and filtered. Then, add reduced iron powder to the filtrate to replace the metallic copper. After liquid-solid separation and acid washing, remove the remaining reduced iron powder.

2. The comprehensive recycling method for lithium battery negative electrodes based on carbon thermal shock and oxidation impurity removal according to claim 1, characterized in that, The method for applying carbon thermal shock to the graphite powder of the negative electrode of waste lithium batteries is as follows: In an inert atmosphere, a heating method based on the Joule heating effect is used, with a heating rate of no less than 1000 degrees Celsius / second, to heat the graphite powder of the negative electrode of waste lithium batteries to 800 degrees Celsius to 1200 degrees Celsius and hold it for 5 to 30 seconds.

3. The comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal according to claim 1, characterized in that, The graphite powder, after carbon thermal shock treatment, is added to deionized water at a certain liquid-to-solid ratio, wherein the liquid-to-solid ratio of graphite powder to deionized water is: The temperature of the deionized water is 60 degrees Celsius, and the stirring time is 120 minutes.

4. The comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal according to claim 1, characterized in that, The lithium-containing water immersion solution is treated using a multi-stage countercurrent water immersion process, including: An n-stage leaching unit is used, in which the lithium-containing aqueous solution is passed sequentially through the nth to the 1st stage leaching unit. After each stage leaching unit comes into contact with the lithium-containing aqueous solution, liquid-solid separation is performed. The filter residue obtained from each stage leaching unit is sent to the next lower-numbered leaching unit for continued countercurrent washing. Fresh water is added to the nth stage leaching unit. The filtrate from each stage leaching unit flows back to the previous higher-numbered leaching unit in the opposite direction, forming a concentration gradient to drive the dilution of soluble lithium ions in the lithium-containing aqueous solution and reduce the residual lithium in the lithium-containing aqueous solution during liquid-solid separation.

5. The comprehensive recycling method for lithium battery negative electrodes based on carbon thermal shock and oxidation impurity removal according to claim 1, characterized in that, The addition of sodium carbonate to the lithium-containing aqueous leaching solution, where lithium ions combine with carbonate ions to form a primary lithium carbonate precipitate, includes: Under stirring conditions, sodium carbonate was added to a lithium-containing aqueous leaching solution, with a molar ratio of lithium ions to carbonate ions of 1:1.

2. The reaction temperature was controlled at 60 degrees Celsius and the reaction time was controlled at 60 minutes, so that lithium ions and carbonate ions could combine to form a primary precipitate of lithium carbonate.

6. The comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal according to claim 1, characterized in that, The operation method for converting the primary lithium carbonate precipitate into lithium bicarbonate through hydrogenation and obtaining the secondary lithium carbonate precipitate through thermal decomposition is as follows: After collecting the primary lithium carbonate precipitate through solid-liquid separation, it is added to deionized water to prepare a suspension. Carbon dioxide gas is then introduced under stirring conditions for chemical treatment, converting lithium carbonate into lithium bicarbonate. The resulting lithium bicarbonate solution is then separated by standing or filtration, and the unreacted residue in the lithium bicarbonate solution is discarded to obtain a clear filtrate containing lithium bicarbonate. The clear filtrate is then heated and evaporated, causing the lithium bicarbonate in the clear filtrate to decompose and generate a secondary lithium carbonate precipitate.

7. The comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal according to claim 1, characterized in that, In step S3, sodium fluoride is added to the lithium removal mother liquor generated during the primary and secondary precipitation reactions of lithium carbonate. The amount of sodium fluoride added is 1.2 to 1.5 times the theoretical amount of the lithium removal mother liquor, so that the residual lithium in the lithium removal mother liquor is precipitated and recovered in the form of lithium fluoride.

8. The comprehensive recycling method for lithium battery negative electrodes based on carbon thermal shock and oxidation impurity removal according to claim 1, characterized in that, The coarse graphite solid was soaked in a weak acid solution with a pH of 1.5 to 2.5; The oxidant is a soluble ferric salt, which oxidizes and removes copper and iron impurities from the crude graphite solid, obtaining a purified graphite solid phase and a leachate.

9. A comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal according to claim 8, characterized in that, The soluble ferric salt is any one of ferric chloride, ferric sulfate, or ferric nitrate.

10. A comprehensive recycling method for lithium battery anodes based on carbon thermal shock and oxidation impurity removal according to claim 1, characterized in that, In step S5, the alkaline solution added to the leachate is any one of sodium hydroxide solution, potassium hydroxide solution, or ammonia solution.

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