Method and device for rapidly preparing high-purity lithium carbonate based on waste lithium battery positive electrode material

Abstract

This application relates to a method and apparatus for rapidly preparing high-purity lithium carbonate from waste lithium-ion battery cathode materials. The method includes the following steps: mixing waste lithium-ion battery cathode materials with a sulfate agent to form a pretreated material, subjecting it to Joule heat treatment to obtain an activating material; mixing the activating material with deionized water, filtering and separating to obtain a leachate; adjusting the pH of the leachate to 11-13, heating and stirring to precipitate, and then drying the resulting precipitate. This invention utilizes the synergistic effect of Joule heating and sulfation to achieve highly selective and preferential extraction of lithium, simultaneously achieving second-level reaction, significantly reduced energy consumption, and large-scale continuous production, yielding a high-purity lithium carbonate product with a purity ≥99.99%.

Description

Technical Field

[0001] This application relates to the field of high-purity lithium carbonate preparation, and more specifically, to a method and apparatus for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode materials. Background Technology

[0002] Lithium, as a strategic and critical resource in the new energy industry, requires a stable supply that is essential for the security of the industrial chain. The lithium content in spent lithium batteries is far higher than that in natural ores, and the energy consumption and carbon emissions during recycling are significantly lower than those from ore extraction, thus making it a highly promising secondary lithium resource. However, existing recycling methods struggle to efficiently and effectively recover the lithium from these batteries. Hydrometallurgy involves acid leaching and co-dissolving lithium with nickel, cobalt, and manganese, with lithium recovered at the end of the process, resulting in significant dispersion losses after multi-stage separation. Direct regeneration is only suitable for waste materials with a single composition and minimal structural degradation, making industrial-scale application difficult.

[0003] The ammonium sulfate roasting-water leaching route has become a research hotspot due to its relatively simple process, and existing technologies are mainly divided into two categories. One category is characterized by full-element leaching, such as CN119208790A and CN108767354A. In this method, the cathode material is mixed with ammonium sulfate (or ammonium bisulfate) and roasted to convert Li, Ni, Co, and Mn into soluble sulfates. After water leaching, all metals enter the solution together, and the cathode material is then regenerated through stepwise separation using a precipitant or direct co-precipitation. Although this method avoids the use of acid, lithium is leached simultaneously with nickel, cobalt, and manganese, resulting in lengthy subsequent separation processes. Furthermore, in CN108767354A, the leaching rates of nickel, cobalt, and manganese are all higher than 98%, and lithium suffers significant dispersion loss during stepwise precipitation. Another approach aims at selective lithium extraction, such as the two-step roasting method proposed in CN202311097108. This method involves precisely controlling the amount of ammonium sulfate to partially sulfatize the cathode material, then heating it to 800-840 °C to allow the transition metal sulfate to react with the unreacted cathode material, converting lithium into water-soluble lithium sulfate while the transition metal remains in the slag phase as oxides. However, this method still requires a high-temperature roasting period of 100-120 minutes. Traditional muffle furnaces rely on external radiation heat transfer, resulting in slow heating rates and uneven temperature fields. Lithium is prone to volatilization and loss or the formation of insoluble complex phases with transition metals during prolonged high-temperature processing, thus limiting the actual improvement in selectivity.

[0004] In recent years, Flash Joule Heating (FJH) technology has been introduced into the field of waste battery recycling. It utilizes current to directly generate bulk Joule heating through a conductive sample, achieving rapid heating and precise temperature control within seconds. This non-equilibrium thermal process drives directional phase transformations that are difficult to achieve with traditional high-temperature treatments. He et al. (Journal of Cleaner Production, 2026) reported an FJH-driven selective lithium extraction strategy using chlorination. Waste NCM811 was mixed with NaCl and carbon black and pulsed at >1500 °C for 3 s. Carbothermic reduction released lithium as Li₂O, which then reacted with NaCl to form water-soluble LiCl. The lithium leaching rate reached 92.4%, and the purity of the obtained Li₂CO₃ was 99.6%. This study demonstrates the feasibility of FJH in the field of lithium recovery, but it still has the following limitations: the reaction temperature needs to be >1500 ℃, and the risk of lithium volatilization increases significantly at high temperatures; a large amount of NaCl (4 times that of the cathode material) and 20% carbon black need to be added, resulting in high material consumption and a complex system; the purity of the obtained lithium carbonate is 99.6%, which has not yet reached the high purity level (≥99.99%); and it does not involve a continuous production scheme, making it difficult to directly support large-scale applications.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The primary objective of this application is to provide a method for rapidly preparing high-purity lithium carbonate from waste lithium battery cathode materials. By utilizing the synergistic effect of Joule heating and sulfation reaction, highly selective and preferential extraction of lithium is achieved, while simultaneously achieving the goals of second-level reaction, significantly reduced energy consumption, and large-scale continuous production, resulting in high-purity lithium carbonate products with a purity ≥99.99%.

[0007] The second objective of this application is to provide an apparatus for rapidly preparing high-purity lithium carbonate using the aforementioned waste lithium battery cathode material. This apparatus is simple in structure, easy to operate, well-matched with the method, and widely applicable.

[0008] To achieve the above objectives, the present invention provides a method for preparing high-purity lithium carbonate based on waste lithium battery cathode materials, comprising the following steps: Waste lithium battery cathode material is mixed with sulfate agent to form a pretreated material, which is then subjected to Joule heat treatment to obtain an activator material. The activating material is mixed with deionized water and then filtered to obtain an extract. The pH of the leachate was adjusted to 11-13, and after heating and stirring to induce precipitation, the precipitate was dried.

[0009] Preferably, as a further feasible option, the waste lithium battery cathode material is a layered cathode material, including waste ternary cathode materials (such as NCM811, NCM622, NCM111) or waste lithium cobalt oxide cathode materials.

[0010] Preferably, as a further feasible option, the sulfate agent is (NH4)2SO4, and the amount of ammonium sulfate added is n((NH4)2SO4) / n(2Li) = 0.5~1.5 based on lithium element.

[0011] Lithium is an alkali metal, while nickel, cobalt, and manganese are transition metals, and their sulfate thermal stability differs significantly. This invention uses SO3, generated from the high-temperature decomposition of (NH4)2SO4, as a sulfating agent. Lithium preferentially forms water-soluble Li2SO4, while the transition metals are converted into insoluble oxides (NiO, Co3O4, Mn3O4). This is achieved by controlling the SO4... 2- Due to the specific molar ratio of lithium to soluble sulfate and the Joule heating temperature, lithium is selectively converted into soluble sulfate, while nickel, cobalt, and manganese remain stably in oxide form. After water leaching, lithium enters the liquid phase, while the transition metals remain in the residue. A high-purity lithium-containing solution can be obtained without complex separation, which can be directly used to prepare high-purity lithium carbonate.

[0012] Preferably, as a further feasible option, n((NH4)2SO4) / n(2Li) = 0.9~1.1. When the amount of ammonium sulfate is insufficient (<0.9), the lithium sulfation reaction is incomplete, and the leaching rate decreases; when the amount is excessive (>1.1), nickel, cobalt, and manganese are prone to over-sulfation and enter the liquid phase with water leaching, reducing the selectivity of lithium. Controlling this ratio at 0.9~1.1 can ensure a high lithium leaching rate while maximally suppressing the co-leaching of transition metals, achieving the best balance between the two.

[0013] Preferably, as a further feasible option, the ball milling rotation speed is 200~300 r / min, and the time is 3~10 min. More uniform ball milling is beneficial to improving the purity of the final prepared lithium carbonate.

[0014] Preferably, as a further feasible option, the Joule heat treatment temperature is 750~1150 ℃ and the time is 2~60 s.

[0015] Preferably, as a further feasible option, the Joule heat treatment is carried out at a temperature of 850~950 °C for a time of 4~10 s.

[0016] The Joule heat treatment temperature and time are controlled within the aforementioned range because if the Joule heat treatment temperature is too low, the transition metal sulfate decomposes incompletely, resulting in a significant decrease in selectivity; if the Joule heat treatment temperature is too high, energy consumption is wasted and sample sintering is likely to occur. If the Joule heat treatment time is too short, the reaction will not proceed sufficiently, resulting in insufficient lithium conversion; if the Joule heat treatment is too long, the converted lithium sulfate may be lost due to localized overheating, while also reducing processing efficiency. Therefore, controlling the Joule heat treatment temperature and time within the aforementioned preferred range ensures that the reaction proceeds fully while balancing selectivity and process economy.

[0017] The reaction mechanism of Joule heat treatment can be summarized as a two-stage mechanism: (1) Initial indiscriminate sulfation stage (extremely short reaction time, approximately 2 s): Under Joule heating transient temperature rise conditions, ammonium sulfate rapidly decomposes to produce active SO3, which undergoes a non-selective sulfation reaction with the waste ternary cathode material. Li, Ni, Co, and Mn are simultaneously converted into water-soluble sulfates (Li2SO4, NiSO4, CoSO4, and MnSO4). In this stage, the difference in sulfation rate among the metal oxides is insufficient to produce macroscopic selectivity on a millisecond timescale.

[0018] (2) Directed migration of sulfate ions and precipitation of transition metal oxides (reaction time extended to 4-10 s or temperature increased to 850-950℃): As the reaction enters the high-temperature maintenance stage, the system gradually moves from kinetic control to thermodynamic equilibrium. The thermal stability of transition metal sulfates (NiSO4, CoSO4, MnSO4) is significantly lower than that of Li2SO4, and they gradually decompose into insoluble oxides (NiO, CoO, MnO) under sustained high temperature. x The lithium (including the MnCo2O4 spinel phase) is extracted and SO3 is released. The released SO3 further combines with the residual Li2O in the system, preferentially transforming into the more thermodynamically stable Li2SO4. At the same time, the generated transition metal sulfates can also undergo solid-phase reactions with the unreacted cathode material, "transferring" sulfate ions to Li and transforming themselves into oxides. The common result of the above pathways is that Li2SO4 becomes the only water-soluble sulfate phase in the product, while Ni, Co, and Mn remain stably in the solid residue in the form of oxides / composite oxides, thereby establishing a highly selective lithium extraction mechanism.

[0019] Although both Joule thermal shock and conventional muffle furnace sintering can reach a peak temperature of 950 °C, their heating modes, heating rates, and mass transfer efficiencies are drastically different. Joule heating utilizes internal heating sources, achieving heating rates of up to 10... 3At ℃ / s, the sample reaches the target temperature instantaneously and synchronously across the entire range, with no significant temperature gradient. Ultrafast heating effectively suppresses the gradual decomposition of ammonium sulfate at low temperatures, promoting its concentrated and intense decomposition at high temperatures. This instantaneously creates a high-pressure reaction atmosphere within the powder pores, forcibly penetrating the NCM particles and greatly accelerating the solid-gas interface reaction rate. Simultaneously, the thermal stress generated by the instantaneous thermal shock causes slight particle cracking and increased porosity, preventing the product layer from passivating and hindering the reaction. In contrast, the muffle furnace relies on external radiative heat conduction, with a heating rate of only 5~20 ℃ / min. Heat transfer from the sample is slow from the surface inwards, resulting in significant temperature lag inside. Slow heating leads to the premature decomposition and volatilization of most ammonium salts at low temperatures, resulting in a low effective gas phase concentration at high temperatures. The dense sulfate product layer generated by the reaction encapsulates unreacted crystals, making solid-phase diffusion a rate-controlling step. Several hours of isothermal control are necessary to compensate for losses due to uneven heat transfer, reagent loss, and slow diffusion. Therefore, Joule heating is a process dominated by high-temperature instantaneous kinetics, while the muffle furnace is limited by both heat transfer and diffusion. The time required for the two to reach the same degree of phase transformation can differ by hundreds of times.

[0020] In summary, the method of this invention overcomes the technical bottleneck of insufficient selectivity caused by the easy volatilization and loss of lithium and the easy formation of insoluble complex phases with transition metals in traditional muffle furnace roasting from both thermodynamic and kinetic perspectives.

[0021] Preferably, as a further feasible option, the solid-liquid ratio of the activating material to the deionized water is 1:(1~50) (g / mL), and the leaching time is 1-60 min. In actual operation, the Joule heating activation reaction and leaching process can be completed within 2 min, greatly improving the reaction efficiency.

[0022] Preferably, as a further feasible option, the pH of the leachate is adjusted to 11-13, the temperature of the heated and stirred precipitation is 40-60 °C, the precipitant solution is slowly added dropwise to precipitate the leachated Li element, and after the addition is completed, stirring is continued until the precipitate is completely formed, and the precipitate is obtained by filtration.

[0023] Preferably, as a further feasible option, the precipitant is at least one of NH4HCO3, (NH4)2CO3 or Na2CO3, and the concentration of the precipitant solution is 1.7~3 mol / L.

[0024] Preferably, as a further feasible option, the dropping rate of the precipitant is 2~4 mL / min.

[0025] Preferably, as a further feasible option, the drying temperature for drying the precipitate is 80~120 ℃, and the drying time is 2~12 h.

[0026] Preferably, as a further implementable solution, the addition amount of the precipitant is 1.05 to 1.4 times the theoretical amount. There is an essential difference in the precipitation behavior of lithium and impurity metals such as nickel, cobalt and manganese in the carbonate system: the carbonate of lithium has a low solubility product, and is easy to crystallize and precipitate as regular lithium carbonate crystals under alkaline conditions; while impurity metal ions tend to form colloidal hydroxide precipitates or basic carbonates under similar conditions, and their precipitation pH range can be effectively separated from the controllable crystallization range of lithium carbonate. The present invention uses the precipitant to gradually release carbonate ions and buffer the pH of the system, so that lithium ions are preferentially and stably crystallized and precipitated in the form of lithium carbonate, while impurities remain in the solution or form an easily separable solid phase. By precisely regulating parameters such as the addition amount of the precipitant, the dropping rate and the heating temperature, highly selective precipitation of lithium and efficient removal of impurities can be realized, and high-purity lithium carbonate can be directly obtained through simple solid-liquid separation, washing and drying. Starting from the precipitation chemistry difference between lithium and impurity metals, this process provides a simple and controllable technical path for efficient purification and high-value transformation of lithium sulfate leachate.

[0027] The present invention also provides a device matching the above method for preparing high-purity lithium carbonate based on spent lithium battery cathode materials, comprising: A material mixing device: configured to mix the spent lithium battery cathode material with a sulfate agent; A conductive conveyor belt, the input end of which receives the mixed material output from the material mixing device; A strickle device, arranged above the conductive conveyor belt, configured to strickle the mixed material on the conductive conveyor belt into a uniform thin layer; A Joule heat activation zone, arranged in the middle section of the conductive conveyor belt, comprising a capacitor bank, a conductive plate and a ceramic heat insulation plate; A water leaching reaction tank, configured to mix the activated material with deionized water for water leaching to extract lithium, wherein the water leaching reaction tank is provided with a feed port, a leachate discharge port and a discharge port.

[0028] Further, in the above device, the actual dimensions of the conductive conveyor belt in application are 10 m in length and 1.2 m in width; the dimensions of the conductive plate are 1 m in length, 1 m in width and 0.5 cm in thickness; the thickness of the material layer formed after the mixed material on the conductive conveyor belt is strickled by the strickle device is 0.1 cm; the running speed of the conductive conveyor belt is 0.1 m / s, the residence time of the mixed material in the Joule heat activation zone is 10 s, and the daily continuous treatment capacity is 7.8 tons.

[0029] Compared with the prior art, the technical effects of the present invention are as follows: 1. This invention introduces Joule heating rapid thermal shock and bulk heating effect into the sulfation reaction process. It utilizes the chemical differences between alkali metals (lithium) and transition metals (nickel, cobalt, manganese) in the cathode material of waste lithium-ion batteries to drive lithium to preferentially convert into water-soluble lithium sulfate within seconds, while simultaneously converting nickel, cobalt, and manganese into stable oxides that are difficult to dissolve in water in situ.

[0030] 2. This invention utilizes direct electrothermal drive via Joule heating, significantly reducing the reaction time from 0.5–2.5 h (1800–9000 s) of traditional roasting to ≤10 s. Combined with a continuous belt-type Joule heat treatment system, the activation reaction and water leaching lithium extraction are integrated into the same production line, enabling a leap from small-batch laboratory production to continuous industrial production. The lithium-containing solution obtained from water leaching undergoes rapid carbonation precipitation, allowing for the continuous preparation of high-purity lithium carbonate with a purity ≥99.99%.

[0031] 3. Compared with traditional methods, the preparation method of this invention significantly reduces energy consumption. Based on the processing of 1 kg of NCM811 cathode material, the actual operating power of the equipment is calculated at 80% of its rated power. A traditional muffle furnace has a rated power of 8 kW and can process 1 kg of sample at a time, calcining at 950 ℃ for 2.5 h. Its power consumption is approximately: 8 kW × 2.5 h × 0.8 = 16 kWh. The Joule heat treatment equipment used in this invention (based on the parameters of commercially available equipment) has a rated power of 60 kW, a single processing capacity of 300 g, and activation at 950 ℃ for 10 s. Processing 1 kg of sample requires 4 batches, and its total power consumption is approximately: 4 × (10 s / 3600) × 60 kW × 0.8 ≈ 0.53 kWh. Based on this calculation, the method of the present invention can reduce energy consumption by about 96.7% compared with traditional muffle furnace roasting, significantly reducing the energy cost and carbon emissions of the recycling process, which meets the needs of green and low-carbon sustainable development.

[0032] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A schematic diagram of the process flow for preparing high-purity lithium carbonate according to Example 1 of the present invention; Figure 2Comparison of leaching efficiencies of various metal elements in Examples 1-4 of this invention (a: different n((NH4)2SO4) / n(2Li); b: different Joule activation temperatures; c: different activation times; d: different cathode materials). Figure 3 This is a comparison diagram of lithium selectivity between Joule thermal sulfidation thermal shock and conventional muffle furnace roasting samples in the embodiments and comparative examples of the present invention. Figure 4 XRD phase analysis of NCM811 cathode materials under different treatment methods (a: original NCM811 cathode material; b: 811-SH-950-1.0-10s and 811-CR-950-1.0-2.5h). Figure 5 TEM-EDS morphology and elemental distribution analysis of NCM811 cathode materials under different treatment methods (a: original NCM811 cathode material; b: 811-SH-750-1.0-2s; c: 811-SH-750-1.0-10s). Figure 6 Phase analysis (XRD) of the recovered lithium carbonate product 811-SH-950-1.0-10s in Example 2; Figure 7 Schematic diagram of a continuous belt Joule heat treatment system. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of the present invention, not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0036] The numbering rules for the sample numbers in the following embodiments and comparative examples are as follows: Taking 811-SH-750-1.0-10s in Example 2 as an example, "811" refers to the waste NCM811 cathode material, "SH" refers to the Joule heating stage temperature rise treatment, "750" refers to the treatment temperature of 750 ℃, "1" refers to n((NH4)2SO4) / n(2Li) = 1, and "10 s" refers to the reaction time of 10 s; Taking 811-CR-750-1-0.5h in Comparative Example 2 as an example, "811" refers to waste NCM811 cathode material, "CR" refers to muffle furnace treatment, "750" refers to the treatment temperature of 750 ℃, "1" refers to n((NH4)2SO4) / n(2Li) = 1, and "0.5 h" refers to the reaction time of 0.5 h. Selectivity = (total amount of (Li+Ni+Co+Mn) in the liquid phase / total amount of (Ni+Co+Mn) in the liquid phase); The apparatus used in the following embodiments is as follows: Figure 7 As shown: The mixing device is used to mix waste lithium battery cathode materials with sulfate agents to form a pretreated mixture. A conductive conveyor belt, whose input end receives the mixture output from the mixing device, is used to carry the mixture and move it slowly in the horizontal direction; A leveling device is disposed above the conductive conveyor belt and is used to level the mixture on the conductive conveyor belt into a uniform thin layer. The Joule heating activation zone, located in the middle section of the conductive conveyor belt, includes a capacitor bank, a conductive plate, and a ceramic heat insulation plate. The conductive plate is used to discharge instantaneously when the mixture passes through, so that the current passes vertically through the material layer to generate bulk Joule heating. The ceramic heat insulation plate is wrapped around the Joule heating activation zone for heat preservation. The water immersion reaction tank is used to receive activated materials and perform water immersion lithium extraction. The water immersion reaction tank is equipped with a feed inlet, a leachate outlet, and a discharge outlet.

[0037] The conductive conveyor belt is 10 m long and 1.2 m wide; the conductive plate is 1 m long, 1 m wide, and 0.5 cm thick; the material layer formed after the mixture is leveled on the conductive conveyor belt by a leveling device is 0.1 cm thick; the operating speed of the conductive conveyor belt is 0.1 m / s; the residence time of the mixture in the Joule heat activation zone is 10 s; and the daily continuous processing capacity is 7.8 tons.

[0038] Example 1 like Figure 1 As shown, the method for preparing high-purity lithium carbonate is carried out according to the following steps: This embodiment aims to investigate the effect of ammonium sulfate addition on lithium leaching rate and selectivity.

[0039] S1. Waste lithium battery cathode material NCM811 and sulfate agent (NH4)2SO4 are mixed at different molar ratios, wherein the amount of ammonium sulfate added is based on lithium elemental content, and n((NH4)2SO4) / n(2Li) is set as follows: 0.5、1.0、1.3、1.5After being uniformly ground by ball milling at a rotation speed of 200 r / min for 10 min, four pretreated materials were obtained.

[0040] S2. Each pretreated material is wrapped in a graphite felt and placed in a Joule heating reactor. Joule heating is performed at an activation temperature of 750 ℃ ​​and an activation time of 10 s to obtain four activated materials, corresponding to the numbers 811-SH-750-0.5-10s, 811-SH-750-1.0-10s, 811-SH-750-1.3-10s and 811-SH-750-1.5-10s.

[0041] S3. Mix each activator with deionized water at a solid-liquid ratio of 1:10 (g / mL), leach at 25 ℃ for 30 min, filter and separate to obtain the leachate. Dilute the leachate and determine the contents of Li, Ni, Co, and Mn to evaluate the effect of different ammonium sulfate additions on the lithium leaching rate. See details below. Figure 2 Figure a in the diagram.

[0042] S4. Adjust the pH of the leachate obtained in step S3 to 11-13, heat it to 40 ℃ under stirring, and then slowly add (NH4)2CO3 solution as a precipitant. The concentration of the precipitant solution is 1.7 mol / L, and the dropping rate of the precipitant is 2 mL / min, in order to precipitate Li in the leachate. + After the addition is complete, continue stirring until the precipitate is fully formed, then filter to obtain lithium carbonate precipitate.

[0043] S5. Wash the precipitate obtained in step S4 with hot water at 70~100 ℃ 1~3 times, and then place it in a vacuum drying oven to dry at 80 ℃ for 12 h to obtain high-purity lithium carbonate product.

[0044] Example 2 The method for preparing high-purity lithium carbonate is carried out according to the following steps: This embodiment aims to investigate the effect of Joule thermal activation temperature on lithium leaching rate.

[0045] S1. The waste lithium battery cathode material NCM811 is mixed with sulfate agent (NH4)2SO4, wherein the amount of ammonium sulfate added is based on lithium element, and n((NH4)2SO4) / n(2Li) = 1.0 is fixed. After being ball-milled uniformly, the ball milling speed is 300 r / min and the time is 3 min to obtain the pretreated material.

[0046] S2. Wrap the pretreated material in graphite felt and place it in a Joule heating reactor. The activation time for Joule heating is 10 seconds, and the activation temperature is set to [temperature value missing]. 750、950、1150 ℃Joule heat treatment was performed to obtain three types of activating materials, with corresponding numbers 811-SH-750-1.0-10s, 811-SH-950-1.0-10s, and 811-SH-1150-1.0-10s.

[0047] S3. Mix each activator with deionized water at a solid-liquid ratio of 1:10 (g / mL), leach at 25℃ for 30 min, filter and separate to obtain the leachate. Determine the contents of Li, Ni, Co, and Mn in the leachate to evaluate the effect of different activation temperatures on the lithium leaching rate. See details below. Figure 2 Figure b in the diagram.

[0048] S4. Adjust the pH of the leachate obtained in step S3 to 11-13, heat it to 60 ℃ under stirring, and then slowly add NH4HCO3 solution. The concentration of the precipitant solution is 3 mol / L, and the dropping rate of the precipitant is 4 mL / min, in order to precipitate Li in the leachate. + After the addition is complete, continue stirring until the precipitate is fully formed, then filter to obtain lithium carbonate precipitate.

[0049] S5. Wash the precipitate obtained in step S4 with hot water at 70-100 °C 1-3 times, then dry it in a vacuum drying oven at 120 °C for 2 h to obtain high-purity lithium carbonate product. The phase analysis (XRD) diagram of the recovered lithium carbonate product (811-SH-950-1.0-10s) is shown below. Figure 6 As shown.

[0050] Taking the experimental group with an activation temperature of 950 °C in Example 2 as an example, based on the Li, Ni, Co, and Mn contents measured in the leachate in step S3, its selectivity (defined as the ratio of the total amount of (Li+Ni+Co+Mn) to (Ni+Co+Mn) in the liquid phase) is as high as 330605, which is far superior to the following comparative examples 2 and 3.

[0051] Example 3 The method for preparing high-purity lithium carbonate is carried out according to the following steps: This embodiment aims to investigate the effect of Joule thermal activation time on lithium leaching rate.

[0052] S1. The waste lithium battery cathode material NCM811 is mixed with sulfate agent (NH4)2SO4. The amount of ammonium sulfate added is based on the lithium element. The ratio of n((NH4)2SO4) / n(2Li) is fixed at 1.0. After being ball-milled evenly, the ball milling speed is 250 r / min and the time is 5min to obtain the pretreated material.

[0053] S2. Wrap the pretreated material in graphite felt and place it in a Joule heating reactor. Set the activation temperature to 750℃ and the activation time to [time value missing]. 2、10、40、60 s Joule heat treatment was performed to obtain four types of activating materials, with corresponding numbers 811-SH-750-1.0-2s, 811-SH-750-1.0-10s, 811-SH-750-1.0-40s, and 811-SH-750-1.0-60s.

[0054] S3. Mix each activator with deionized water at a solid-liquid ratio of 1:30 (g / mL), leach at 25℃ for 40 min, filter and separate to obtain the leachate. Determine the contents of Li, Ni, Co, and Mn in the leachate to evaluate the effect of different activation times on the lithium leaching rate. See details below. Figure 2 Figure c in the diagram.

[0055] S4. Adjust the pH of the leachate obtained in step S3 to 11-13, heat it to 50°C under stirring, and then slowly add (NH4)2CO3 solution. The concentration of the precipitant solution is 2 mol / L, and the dropping rate of the precipitant is 3 mL / min, in order to precipitate Li in the leachate. + After the addition is complete, continue stirring until the precipitate is fully formed, then filter to obtain lithium carbonate precipitate.

[0056] S5. Wash the precipitate obtained in step S4 with hot water at 70~100 ℃ 1~3 times, and then place it in a vacuum drying oven to dry at 90 ℃ for 10 hours to obtain high-purity lithium carbonate product.

[0057] Example 4 The method for preparing high-purity lithium carbonate is carried out according to the following steps: This embodiment aims to examine the universality of the method of the present invention for different types of waste cathode materials.

[0058] S1. Take waste lithium battery positive electrode materials separately. NCM622, NCM111 and LCO Each of the three pretreated materials was mixed with a sulfate agent (NH4)2SO4. The amount of ammonium sulfate added was based on lithium element, and n((NH4)2SO4) / n(2Li) = 1.0 was fixed. After being ball-milled uniformly, the ball milling speed was 300 r / min and the time was 3 min, resulting in three pretreated materials.

[0059] S2. Each pretreatment material was wrapped in graphite felt and placed in a Joule heating reactor. All materials were subjected to Joule heating at an activation temperature of 950 ℃ and an activation time of 10 s to obtain three types of activating materials, with corresponding numbers 622-SH-950-1.0-10s, 111-SH-950-1.0-10s and LCO-SH-950-1.0-10s.

[0060] S3. Mix each activator with deionized water at a solid-liquid ratio of 1:10 (g / mL), leach at 25°C for 30 min, filter and separate to obtain the leachate. Dilute the leachate to an appropriate concentration and determine the contents of Li, Ni, Co, and Mn to evaluate the treatment effect of Joule thermal sulfidation on different waste lithium battery cathode materials. See details below. Figure 2 The d-graph in the image.

[0061] S4. Adjust the pH of the leachate obtained in step S3 to 11-13, heat it to 55 ℃ under stirring, and then slowly add (NH4)2CO3 solution. The concentration of the precipitant solution is 2.6 mol / L, and the dropping rate of the precipitant is 3.5 mL / min, in order to precipitate Li in the leachate. + After the addition is complete, continue stirring until the precipitate is fully formed, then filter to obtain lithium carbonate precipitate.

[0062] S5. Wash the precipitate obtained in step S4 with hot water at 70~100 ℃ 1~3 times, and then place it in a vacuum drying oven to dry at 95 ℃ for 5 h to obtain high-purity lithium carbonate product.

[0063] Comparative Example 1 The difference between this comparative example and Example 1 is that step S1 is omitted, i.e., ammonium sulfate is not added, and the waste NCM811 cathode material is directly used as the pretreatment material. The remaining implementation conditions are exactly the same as in Example 1, and the resulting activated sample is numbered 811-SH-750-0-10s.

[0064] Comparative Example 2 The difference between this comparative example and Example 1 lies in step S2: the pretreated materials are placed in a muffle furnace and calcined at 750 °C. 0.5、1.5、2.5 h Three comparative samples with different treatment times were obtained, corresponding to the numbers 811-CR-750-1-0.5h, 811-CR-750-1-1.5h, and 811-CR-750-1-2.5h. The remaining implementation conditions were the same as in Example 1.

[0065] Comparative Example 3 The difference between this comparative example and Example 1 lies in step S2: the pretreated materials are placed in a muffle furnace and calcined at 950 °C. 0.5、1.5、2.5 h Three comparative samples with different treatment times were obtained, corresponding to the numbers 811-CR-950-1-0.5h, 811-CR-950-1-1.5h, and 811-CR-950-1-2.5h. The remaining implementation conditions were the same as in Example 1.

[0066] Among them, under the condition of calcination at 950 ℃ for 2.5 h (sample 811-CR-950-1-2.5h), the selectivity was 24111, which is the best value in this comparative example series.

[0067] Experimental conclusion: Figure 3 The figure shows a comparison of lithium selectivity between Joule heat treatment (sulfidation) and conventional muffle furnace roasting samples in the examples and comparative examples. The ratio of the total amount of (Li+Ni+Co+Mn) to (Ni+Co+Mn) in the liquid phase is used as the selectivity evaluation index. The higher the ratio, the greater the preferential leaching of lithium relative to nickel, cobalt, and manganese, and the better the selective separation effect. Under comparable lithium extraction rates, the optimal selectivity of Joule heat treatment (811-SH-950-1-10s) can reach 330605, while the optimal selectivity of conventional muffle furnace roasting (811-CR-950-1-2.5h) is 24111, with the former being about 14 times higher than the latter. If the worst operating condition of the muffle furnace (811-CR-750-1-2.5h, with a selectivity of 8.9) is used as the benchmark, the optimal selectivity of Joule heat treatment is about 37146 times higher. The above results show that the Joule thermal shock treatment method of the present invention is significantly superior to the traditional muffle furnace roasting in different comparative dimensions. It can achieve one-step high-selectivity separation of lithium with only simple water leaching, with a lithium extraction rate of more than 90%. Nickel, cobalt and manganese are almost all left in the leaching residue, thus avoiding the complex separation problems caused by multi-metal co-leaching in the traditional "total leaching-step separation" route from the source.

[0068] Figure 4-5 The phase evolution of NCM811 and ammonium sulfate under two treatment methods—conventional long-term muffle furnace roasting and Joule heat shock treatment—was analyzed by XRD and TEM-EDS. The results showed that both treatments effectively destroyed the original layered ternary structure of NCM811, with NiO and soluble metal sulfates as the main products. However, significant differences existed in the reaction pathways, intermediate products, and final phase composition between the two methods. After Joule heat shock treatment, the lithium selectivity was improved by 14–37,146 times compared to muffle furnace roasting.

[0069] In summary, the present invention, based on the chemical differences between alkali metals and transition metals in the cathode material, introduces a sulfate agent and combines Joule heating rapid thermal shock with bulk heating effects to selectively convert lithium into water-soluble lithium sulfate within seconds (≤10 s), while simultaneously converting nickel, cobalt, and manganese into insoluble stable oxides. The energy consumption is reduced by more than 96% compared to traditional pyrometallurgical roasting. Through the synergistic effect of Joule heating-induced rapid phase change and selective sulfation, highly selective one-step separation of lithium can be achieved solely through water leaching, with a lithium leaching rate greater than 90%. Almost all nickel, cobalt, and manganese remain in the leaching residue. The lithium selectivity is 14 to 37,146 times higher than that of traditional roasting methods, and the recovered lithium carbonate purity is ≥99.99%.

[0070] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0071] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode materials, characterized in that, Includes the following steps: Waste lithium battery cathode material is mixed with sulfate agent to form a pretreated material, which is then subjected to Joule heat treatment to obtain an activator material. The activating material is mixed with deionized water and then filtered to obtain an extract. The pH of the leachate was adjusted to 11-13, and after heating and stirring to induce precipitation, the precipitate was dried.

2. The method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode material according to claim 1, characterized in that, The Joule heat treatment temperature is 750~1150 ℃, and the time is 2~60 s.

3. The method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode material according to claim 1, characterized in that, The precipitant is at least one of NH4HCO3, (NH4)2CO3 or Na2CO3, and the concentration of the precipitant solution is 1.7~3 mol / L.

4. The method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode material according to claim 3, characterized in that, The dropping rate of the precipitant is 2~4 mL / min.

5. The method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode material according to claim 1, characterized in that, The solid-liquid ratio of the activator to the deionized water is 1:(1~50) (g / mL), and the leaching time is 1-60 min.

6. The method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode material according to claim 1, characterized in that, The Joule heat treatment temperature is 850~950 ℃, and the time is 4~10 s.

7. The method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode material according to claim 1, characterized in that, The drying temperature for the precipitate is 80~120 ℃, and the drying time is 2~12 h.

8. The method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode material according to claim 1, characterized in that, The sulfate agent is (NH4)2SO4, and the amount of ammonium sulfate added, calculated based on lithium element, is n((NH4)2SO4) / n(2Li) = 0.5~1.

5.

9. The method for rapidly preparing high-purity lithium carbonate based on waste lithium battery cathode material according to claim 8, characterized in that, n((NH4)2SO4) / n(2Li) = 0.9~1.

1.

10. The apparatus for the rapid preparation of high-purity lithium carbonate based on waste lithium battery cathode material according to any one of claims 1-9, characterized in that, include: Mixing device: used to mix waste lithium battery cathode materials with sulfate agent; Conductive conveyor belt: its input end receives the mixture output from the mixing device; Scraping device: disposed above the conductive conveyor belt, used to scrape the mixture on the conductive conveyor belt into a uniform thin layer; Joule thermal activation zone: located in the middle section of the conductive conveyor belt, including capacitor bank, conductive plate and ceramic heat insulation plate; Water immersion reaction tank: used for mixing activator material with deionized water to extract lithium by water immersion. The water immersion reaction tank is equipped with a feed inlet, a leachate outlet and a discharge outlet.

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