Method for preparing battery-grade lithium carbonate based on continuous flow dynamic coupling micro-reaction system

Abstract

The invention discloses a method for preparing battery-grade lithium carbonate based on a continuous flow coupling micro-reaction system. The method adopts an ammonia process path and comprises the following steps: firstly, introducing carbon dioxide into a micro-channel reactor to react with ammonia water to generate an ammonium carbonate solution; and continuously injecting the ammonium carbonate solution and the lithium chloride solution into an autonomously designed continuous flow dynamic microreactor. The continuous flow dynamic micro-reactor effectively crushes separated solid particles through shearing force generated by high-speed stirring inside, the problem that a traditional micro-reactor is easy to block is solved, and long-term stable continuous operation of a solid-containing system is realized. The particle size distribution and the impurity content of lithium carbonate can be accurately controlled by adjusting the reaction temperature, the stirring speed, the anti-solvent proportion and the raw material ratio. The purity of the prepared lithium carbonate is higher than 99.5 wt%, sodium ion pollution is avoided, and the method has the advantages of being efficient, high in automation degree, environmentally friendly and the like and has remarkable industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of lithium battery material preparation and microchemical technology, specifically to a method for the efficient and continuous synthesis of battery-grade lithium carbonate using an ammonia-based route and an anti-clogging microfluidic system. Background Technology

[0002] Battery-grade lithium carbonate, as a high-value-added lithium salt, requires extremely high purity (>99.5 wt%). Currently, the main industrial method is precipitation, where sodium carbonate is added as a precipitant to concentrated brine or ore leachate. However, due to the similar chemical properties of sodium ions (Na⁺) and lithium ions (Li⁺), sodium impurities easily accumulate during precipitation, requiring multi-stage recrystallization purification, resulting in high production costs and complex processes. Furthermore, to obtain the desired particle size distribution, energy-intensive post-processing technologies such as jet milling are typically employed. Microreactors, due to their superior mixing efficiency and mass and heat transfer performance, exhibit significant advantages in chemical synthesis. However, in lithium carbonate synthesis, microchannels are prone to particle bridging, deposition, and scaling, leading to system blockage, which limits the application of microreactor technology in solid precipitation reactions. Therefore, a continuous flow synthesis process that can maintain the high mixing efficiency of microreactors while effectively preventing solid blockage is urgently needed.

[0003] With the rapid development of new energy vehicles and energy storage, high-purity battery-grade lithium carbonate, as a core raw material, has become a focus of industry attention due to its efficient and low-cost preparation technology. Currently, the commonly used sodium salt precipitation method in industry easily introduces sodium impurities during precipitation because sodium ions and lithium ions have similar chemical properties. This makes it difficult for the product purity to directly meet battery-grade standards, requiring multiple cumbersome recrystallization purification processes, which significantly increases production energy consumption and process costs. In contrast, the "ammonia method," which uses ammonia to absorb carbon dioxide (CO2) to generate an intermediate that reacts with lithium salts, has significant advantages: this route avoids the introduction of alkali metal ions at the source, significantly improving product purity. Simultaneously, it converts greenhouse gas carbon dioxide into high-value-added industrial lithium salts, aligning with the development goals of green chemistry and "carbon neutrality." Furthermore, the reaction byproduct ammonium chloride can be recycled, possessing extremely high environmental value and economic benefits.

[0004] However, the ammonia-based synthesis of lithium carbonate is a complex reaction process, and precise control of its crystallization kinetics is crucial for the particle size distribution of the product. Traditional batch reactors, due to low mass transfer efficiency and uneven mixing, often result in a wide particle size distribution and inconsistent morphology of the product. While microreactor technology can achieve precise control of the crystallization process due to its superior mass transfer performance and extremely high mixing efficiency, lithium carbonate, as a typical strongly crystalline system, is prone to crystal bridging and solid deposition during precipitation within microchannels, leading to severe system blockage. Therefore, developing an anti-clogging continuous flow dynamic microreactor that can leverage the advantages of microscale mass transfer while effectively preventing particle aggregation and adhesion through dynamic mechanical shearing is a core technology that urgently needs to be solved to achieve continuous and large-scale production of battery-grade lithium carbonate. Summary of the Invention

[0005] This invention addresses the shortcomings of existing lithium carbonate production technologies, such as low purity, susceptibility to sodium contamination, complex processes, and easy clogging of microreactors. It proposes a method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreactor system. Specifically, the continuous flow coupled microreactor system consists of a capillary microchannel reactor coupled with a continuous flow dynamic microreactor.

[0006] According to one aspect of the present invention, a method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreactor system is provided. The method includes the following steps: (1) passing carbon dioxide gas into a capillary microchannel reactor containing ammonia water for absorption reaction to generate an ammonium carbonate intermediate solution; (2) continuously injecting the ammonium carbonate intermediate solution and an inorganic lithium salt solution into a continuous flow dynamic microreactor for precipitation reaction to obtain a slurry containing lithium carbonate solid; (3) performing solid-liquid separation, washing and drying of the slurry to obtain a battery-grade lithium carbonate product.

[0007] This invention employs a microchannel reactor in the carbon dioxide absorption reaction stage, which significantly improves the mass transfer efficiency and reaction efficiency of the gas-liquid two-phase reaction, suppresses side reactions and ammonia volatilization, and can also maintain the stability of reaction system parameters through an online flow closed-loop control system, enabling ammonia and carbon dioxide to complete a highly efficient reaction in the microchannel reactor, thereby improving the selectivity and purity of ammonium carbonate.

[0008] In some embodiments, the capillary microchannel reactor has an inner diameter of 0.5-2.0 mm and a length of 1.2-20 m. With these characteristic dimensions, its specific surface area can reach 2000-8000 m² / m³, which is 1-2 orders of magnitude higher than that of traditional reaction towers (100-500 m² / m³). This enables instantaneous and efficient mixing and rapid interface renewal of the gas-liquid two phases (ammonia and CO2), and the mass transfer coefficient (kLa) is increased by 10-100 times compared to traditional processes. This allows the reaction to shift from mass transfer control to kinetic control, and the reaction time is shortened from minutes to seconds in traditional processes, significantly improving production efficiency. For example, the inner diameter of the capillary microchannel reactor can be 0.5 mm, 0.75 mm, 1.0 mm, 1.5 mm or 2.0 mm, or any two of the above values ​​as endpoints. The length of the capillary microchannel reactor can be 1.2 m, 1.25 m, 2.2 m, 5 m, 12 m or 20 m, or any two of the above values ​​as endpoints.

[0009] In some embodiments, in step (1), gaseous carbon dioxide and liquid ammonia form a Taylor flow in a microchannel reactor, wherein the flow rate of carbon dioxide is 80-140 ml / min, the flow rate of ammonia is 1-15 ml / min, and the molar concentration of ammonia is 0.5 mol / L-15 mol / L; the molar ratio of carbon dioxide gas to ammonia in ammonia, n(NH3):n(CO2), is 1.8:1 to 3.1:1.

[0010] The fluid flow within the microchannel reactor is very close to plug flow in engineering terms, with extremely low backmixing and a narrow residence time distribution (RTD≤0.1). This allows all materials to undergo a consistent reaction time, temperature, and concentration process, avoiding insufficient or excessive reaction caused by backmixing and dead zones in traditional reaction towers. It significantly improves the crystallinity, particle size distribution uniformity, and batch-to-batch stability of the product, making it suitable for the stringent standards of consistency of precursor materials in lithium battery materials.

[0011] Microchannel reactors can precisely maintain the n(NH3):n(CO2) molar ratio within the optimal range of 1.8:1 to 3.1:1, especially 2.0-2.5:1, through online closed-loop flow control. For example, the n(NH3):n(CO2) molar ratio can be 1.8:1, 2.1:1, 2.5:1, 3.1:1, or any two of these values ​​as endpoints. This molar ratio range allows for a stable Taylor flow between the gas and liquid phases within the tube, ensuring a carbon dioxide absorption rate of 92% or 99.5% or higher. The product is predominantly pure ammonium carbonate with a selectivity ≥95%, significantly superior to the product composition fluctuations caused by uneven gas-liquid distribution in traditional reaction towers, meeting the stringent purity requirements of lithium battery materials for precursors.

[0012] The molar ratio of ammonia to carbon dioxide is achieved by adjusting the concentration and flow rate of ammonia and the flow rate of carbon dioxide. For example, the concentration of ammonia can be 0.5 mol / L, 1.5 mol / L, 5 mol / L, 8 mol / L, 10 mol / L, 15 mol / L, or any range with any two of these values ​​as endpoints. The ammonia concentration should preferably not exceed 15 mol / L; otherwise, it can easily lead to significant volatilization, difficult exhaust gas treatment, and localized salting-out crystallization that can clog microchannels. For example, the flow rate of ammonia can be 1 ml / min, 2 ml / min, 5 ml / min, 10 ml / min, 12 ml / min, 15 ml / min, or any range with any two of these values ​​as endpoints. This flow rate range ensures the smooth progress of the carbon dioxide absorption reaction in actual experimental operations and engineering practice. If the ammonia flow rate is too low, it can easily lead to stratification of the reaction system, unstable flow patterns, and excessively long residence times; conversely, if the flow rate is too high, it will result in insufficient residence time and a reduced carbon dioxide absorption rate. For example, the flow rate of the carbon dioxide can be 80 ml / min, 100 ml / min, 120 ml / min, 140 ml / min, or a range of values ​​with any two of the above values ​​as endpoints, thereby ensuring the formation of a stable gas-liquid Taylor flow within the microchannel.

[0013] The formation of ammonium carbonate is a strongly exothermic reaction, but excessively high temperatures can lead to ammonia volatilization. Therefore, during the carbon dioxide absorption stage, the reaction temperature needs to be maintained between 20-40℃. The microscale structure of the microchannel reactor endows it with an extremely high heat transfer coefficient (10⁻⁶). 3 -10 4 (W / m²・K) can remove the heat of reaction in real time, achieve near isothermal operation in all channels, maintain reaction temperature fluctuation ≤±1℃, effectively avoid the volatilization of NH3, decrease in CO2 solubility and generation of by-products (such as ammonium bicarbonate and ammonium carbamate) caused by local overheating in traditional reaction towers, and ensure product purity and stability from the source.

[0014] In some embodiments, in step (1), the carbonate concentration in the intermediate solution at the outlet is adjusted to 1.0-4.5 mol / L by adjusting the gas-liquid flow ratio. For example, the carbonate concentration can be 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 4.0 mol / L, or a range of values ​​with any two of the above values ​​as endpoints. The product is mainly pure ammonium carbonate, with almost no detectable bicarbonate ion concentration, meeting the stringent purity requirements of lithium battery materials for precursors. It can be directly used in the second-stage lithium precipitation reaction of ammonium carbonate and inorganic lithium salts.

[0015] During the lithium precipitation reaction of ammonium carbonate and lithium salt, crystal bridging and solid deposition easily occur during lithium carbonate crystallization, leading to severe system blockage. This invention employs a continuous-flow dynamic microreactor with a built-in stirring magnet. On one hand, it leverages the superior mass transfer performance and extremely high mixing efficiency at the microscale to achieve precise control of the crystallization process. On the other hand, it effectively prevents particle aggregation and adhesion to the wall through dynamic mechanical shearing, ultimately producing battery-grade lithium carbonate particles with a narrow particle size distribution and uniform morphology.

[0016] In some embodiments, in step (2), a magnetic stirring device is installed inside the continuous flow dynamic microreactor, and the stirring speed during the reaction process is controlled at 500-1500 rpm. For example, the stirring speed can be 500 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1500 rpm, or any two of the above values ​​as endpoints. At the above stirring speeds, a single micro-circular channel tends towards a fully mixed flow model, where fluid micro-particles are continuously sheared, broken, and torn, achieving extremely short diffusion distances, huge specific surface areas, and near-ideal micro-mixing efficiency under the combined effect of microscale effects.

[0017] In some embodiments, in step (2), the inorganic lithium salt is lithium chloride or lithium sulfate, and the concentration of the inorganic lithium salt solution is 1.0-5.0 mol / L. For example, the concentration of the inorganic lithium salt solution can be 1.0 mol / L, 3.0 mol / L, 5 mol / L, or a range of values ​​with any two of the above values ​​as endpoints.

[0018] In some embodiments, in step (2), the inorganic lithium salt solution contains an antisolvent, which is one or more of methanol, ethanol, or isopropanol; the volume percentage of the antisolvent in the inorganic lithium salt solution is 0-30%. For example, the concentration of the inorganic lithium salt solution can be 0%, 10%, 20%, 25%, 30%, or a range of values ​​with any two of the above values ​​as endpoints. Adding an appropriate amount of antisolvent can significantly increase the supersaturation of the reaction, improving the yield while effectively refining and homogenizing the crystal particle size. However, an excessively high proportion of antisolvent can lead to premature precipitation of the inorganic lithium salt, resulting in poor system fluidity and uneven particle size distribution.

[0019] In some embodiments, in step (2), the molar ratio of the ammonium carbonate intermediate to the inorganic lithium salt, n(CO3) 2- The molar ratio of Li⁺ is 0.5:1 to 1.5:1. For example, the molar ratio can be 0.8:1, 1:1, 1.2:1, 1.5:1, or a range of values ​​with any two of these values ​​as endpoints. If the molar ratio is too small, then Li⁺ will... +Excessive amounts can lead to serious losses. If the molar ratio of feed is too high, the excessive amount of ammonium carbonate will cause the ammonia content in the wastewater to exceed the standard, affecting subsequent treatment.

[0020] In some embodiments, the reaction temperature in step (2) is controlled at 20-60°C, and the total residence time of the material in the continuous flow dynamic microreactor is 1-20 min. For example, the reaction temperature can be 20°C, 30°C, 40°C, 50°C, 60°C, or any two of the above values ​​as endpoints. The precipitation reaction of ammonium carbonate with inorganic lithium salt involves rapid ion exchange. Appropriately increasing the temperature can enhance the ion exchange reaction rate, but the reaction temperature should not exceed 60°C. Otherwise, it can easily lead to a sharp increase in supersaturation, causing a large amount of lithium carbonate to crystallize and block the microreactor outlet. Simultaneously, the reactant ammonium carbonate may undergo thermal decomposition, leading to a decrease in the carbonate concentration in the reaction system and affecting the lithium carbonate yield.

[0021] According to another aspect of the present invention, battery-grade lithium carbonate prepared based on a continuous flow coupled microreactor system is provided, wherein the battery-grade lithium carbonate is in the form of uniform particles or flakes, and the median particle size D is [missing information]. 50 The median particle size is 4-20 μm. For example, the median particle size D... 50 The micrometer size can be 4.2μm, 7.9μm, 8.5μm, 9.4μm, 9.5μm, 9.8μm, 10.2μm, 11.4μm, 12.1μm, 14.3μm, 15.4μm, or a range of values ​​with any two of the above values ​​as endpoints. All indicators of the battery-grade lithium carbonate product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001wt%, which is superior to the YS / T582-2013 battery-grade lithium carbonate standard.

[0022] In some embodiments, the battery-grade lithium carbonate prepared based on a continuous flow coupled microreaction system has Na and Mg contents of less than 0.001 wt%, and Ca and Fe contents of less than 0.0005 wt%, which is superior to the YS / T582-2013 standard for battery-grade lithium carbonate.

[0023] In some embodiments, the XRD diffraction characteristic peaks of battery-grade lithium carbonate prepared based on a continuous flow coupled microreaction system perfectly match the characteristic peaks of standard lithium carbonate (Li₂CO₃, PDF#22-1141), indicating it belongs to pure-phase Li₂CO₃. Battery-grade lithium carbonate exhibits uniformly shaped, plate-like particles. Its XRD diffraction pattern shows a main peak with a full width at half maximum (FWHM) of approximately 0.35° near 2θ=30°, a small average grain size, and a larger specific surface area, making it more advantageous in battery material applications and suitable as a raw material for large-scale industrial production.

[0024] Compared with the prior art, this application has the following significant technical advantages: (1) The present invention uses a microchannel reactor to carry out the absorption reaction of carbon dioxide in ammonia water. By controlling key process parameters such as the flow rate, molar ratio, reaction temperature and reaction residence time of the two-phase reactants of ammonia water and carbon dioxide, and by adjusting the molar ratio of the two-phase reactants to form Taylor flow in the microchannel, the reaction efficiency is significantly improved, the carbon dioxide absorption rate is increased to more than 99.5%, the ammonium carbonate in the product has very high purity and almost no ammonium bicarbonate byproduct, and can be directly used for the precipitation reaction of inorganic lithium salts.

[0025] (2) The continuous flow dynamic microreactor of the present invention has a magnetic stirrer built into a micro reaction tank, thereby actively forming a high specific surface area and strong shear flow field in the microreactor. On the one hand, it can make use of the excellent mass transfer performance and extremely high mixing efficiency at the microscale to achieve precise control of the crystallization process. On the other hand, it can effectively prevent particle aggregation and wall adhesion through dynamic mechanical shearing, and finally prepare battery-grade lithium carbonate particles with narrow particle size distribution and uniform morphology.

[0026] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of the embodiments of this application are described below. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the continuous flow dynamic coupling microreaction system for preparing battery-grade lithium carbonate according to the present invention; Figure 2 This is a schematic diagram of a continuous flow dynamic microreactor structure used to prepare battery-grade lithium carbonate; Figure 3 shows the lithium carbonate outlet conditions of different reactors. Figure 3a The lithium carbonate outlet of the 1mm inner diameter microchannel reactor is in its final state. Figure 3b The lithium carbonate outlet of the 2mm inner diameter microchannel reactor is in lithium carbonate state. Figure 3c The lithium carbonate state at the outlet of the continuous flow dynamic microreactor; Figure 4 The XRD patterns of battery-grade lithium carbonate and reagent-grade lithium carbonate prepared by a continuous flow dynamic microreactor are compared. Figure 5 This is a SEM image of the battery-grade lithium carbonate particles prepared in Example 1 of the present invention. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0029] To keep the drawings concise, only the parts relevant to the invention are shown schematically, and they do not represent the actual structure of the device. Furthermore, for ease of understanding, some drawings show only one or a few components with the same structure or function. In this document, "a few" includes both "two" and "more than two".

[0030] In this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 a physical or electrical connection between different components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or component 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 present invention.

[0032] Figure 1 A schematic diagram illustrating the preparation of battery-grade lithium carbonate using the continuous flow dynamically coupled microreaction system of the present invention is shown. Figure 1 As shown, the continuous flow dynamic coupled microreactor system is composed of a capillary microchannel reactor (tube) coupled with a continuous flow dynamic microreactor (CSTR). First, a carbon dioxide absorption stage is carried out in the capillary microchannel reactor. High-purity carbon dioxide (99.99% purity) and 2.5wt%-28wt% ammonia water are injected separately into the PFA microchannel reactor with an inner diameter of 0.5mm-2.0mm via metering pumps, generating an ammonium carbonate intermediate solution through gas-liquid mass transfer.

[0033] Subsequently, the precipitation reaction of lithium carbonate was carried out in a continuous flow dynamic microreactor. The ammonium carbonate solution generated in the previous step and the 1.0-5.0 mol / L inorganic lithium salt solution were separately injected into the reactor using metering pumps. Figure 2 The ion exchange reaction, as shown, takes place in a continuous flow dynamic microreactor to produce lithium carbonate. Figure 2As shown, the continuous flow dynamic microreactor is a miniature plate reactor made of titanium alloy, consisting of a cover plate 1, a reaction chamber module 2, and a sealing ring (not shown in the figure). The cover plate 1 is equipped with an ammonium carbonate solution inlet 101, an inorganic lithium salt solution inlet 102, and an outlet 103. The inorganic lithium salt solution may contain an antisolvent or a solvent. The resulting lithium carbonate and ammonium salt solutions flow out of the continuous flow dynamic microreactor through the outlet 103. Furthermore, the cover plate 1 is also equipped with a heat dissipation zone 105 to facilitate rapid heat dissipation.

[0034] The reaction chamber module 2 contains multiple micro-reaction tanks 201 connected in series. Each micro-tank contains a magnetic stir bar (not shown in the figure), with a stirring speed of 500-1500 rpm, preferably 800-1200 rpm. The total effective reaction volume of the microreactor is 10 mL, and the connecting pipelines are made of PFA material. The multiple micro-reaction tanks 201 are connected by flow channels 202, and the reaction tanks are also connected to the feed inlet via flow channels 202.

[0035] To ensure the airtightness of the microreactor, the reaction chamber module 2 is also provided with an annular sealing groove 203, in which a sealing ring can be installed. The cover plate 1 is provided with several connection holes 104, which correspond one-to-one with the connection holes 204 provided on the reaction chamber module 2. The cover plate 1 and the reaction chamber module 2 are fastened together by bolts through the connection holes 104 and 204 to form a closed microfluidic system.

[0036] During the precipitation reaction Figure 2 The continuous flow dynamic microreactor shown effectively prevents lithium carbonate particles from agglomerating and adhering to the walls, causing blockage, through dynamic mechanical shearing. Furthermore, by precisely controlling the feed concentration, flow rate, and molar ratio, the system is kept in a metastable state. Thus, the rapidly flowing feed and high shear force effectively suppress the aggregation and adhesion of microcrystal nuclei. The lithium carbonate solution observed at the microreactor outlet is clear, as shown... Figure 3c As shown.

[0037] After the reaction is complete, the lithium carbonate product undergoes post-processing, including aging, filtration, washing, and drying, to obtain battery-grade lithium carbonate. For example... Figure 4 As shown, the X-ray diffraction pattern of the battery-grade lithium carbonate perfectly matches the characteristic peaks of reagent-grade lithium carbonate, belonging to pure-phase Li₂CO₃. The full width at half maximum (FWHM) of the main peak near 2θ=30° in the XRD diffraction pattern is approximately 0.35°. Figure 5 As shown, the battery-grade lithium carbonate prepared by this invention consists of uniformly shaped flake-like particles with a smooth and flat surface, clear edges, small average grain size, and large specific surface area, which gives it a greater advantage in battery material applications and makes it suitable as a raw material for large-scale industrial production.

[0038] Example of ammonium carbonate preparation Preparation Example 1 A PFA microchannel with an inner diameter of 1.0 mm and a length of 5 m was used as the carbon dioxide absorption reactor. A 5 mol / L ammonia solution and high-purity carbon dioxide gas were introduced into the microchannel reactor, and the n(NH3):n(CO2) molar ratio was changed to 2.5:1 by adjusting the inlet gas flow rate. The absorption temperature was maintained at 25℃, the liquid phase ammonia flow rate was 2 ml / min, and the gas phase CO2 flow rate was 89.6 ml / min. The carbon dioxide was almost completely absorbed, and a clear ammonium carbonate solution of about 2 mol / L was obtained at the outlet.

[0039] Preparation Example 2 Preparation Example 2 is similar to Preparation Example 1, except that the ammonia concentration is 10 mol / L, the ammonia flow rate is 1.5 ml / min, the gas phase CO2 flow rate is 134.4 ml / min, the n(NH3):n(CO2) molar ratio is 2.5:1, the carbon dioxide absorption rate reaches more than 99.5%, and a clear ammonium carbonate solution of about 4 mol / L is obtained at the outlet.

[0040] Preparation Example 3 Preparation Example 3 is similar to Preparation Example 1, except that the ammonia flow rate is 4 ml / min, the gas phase CO2 flow rate is 85 ml / min, the n(NH3):n(CO2) molar ratio is 2.1:1, the carbon dioxide absorption rate reaches more than 99.5%, and a clear ammonium carbonate solution of about 2.0 mol / L is obtained at the outlet.

[0041] Preparation Example 4 Preparation Example 4 was similar to Preparation Example 1, except that the gas phase CO2 flow rate was 124 ml / min, the n(NH3):n(CO2) molar ratio was reduced to 1.8:1, carbon dioxide was in relative excess, the pipeline pressure fluctuation increased and the absorption rate dropped to about 92%, and a clear ammonium carbonate solution of about 1.8 mol / L was obtained at the outlet.

[0042] Preparation Example 5 Preparation Example 5 is similar to Preparation Example 3, except that a PFA microchannel with an inner diameter of 0.5 mm and a length of 20 m is used as a carbon dioxide absorption reactor. The gas and liquid phases form a stable Taylor flow inside the tube, and the carbon dioxide absorption rate reaches more than 99.5%. A clear ammonium carbonate solution of about 2.0 mol / L is obtained at the outlet.

[0043] Preparation Example 6 Preparation Example 6 is similar to Preparation Example 3, except that a PFA microchannel with an inner diameter of 0.75 mm and a length of 12 m is used as a carbon dioxide absorption reactor. The gas and liquid phases form a stable Taylor flow inside the tube, and the carbon dioxide absorption rate reaches more than 99.5%. A clear ammonium carbonate solution of about 2.0 mol / L is obtained at the outlet.

[0044] Preparation Example 7 Preparation Example 7 is similar to Preparation Example 3, except that a PFA microchannel with an inner diameter of 1.5 mm and a length of 2.2 m is used as a carbon dioxide absorption reactor. The gas and liquid phases form a stable Taylor flow inside the tube, and the carbon dioxide absorption rate reaches more than 99.5%. A clear ammonium carbonate solution of about 2.0 mol / L is obtained at the outlet.

[0045] Preparation Example 8 Preparation Example 8 is similar to Preparation Example 3, except that a PFA microchannel with an inner diameter of 2.0 mm and a length of 1.25 m is used as a carbon dioxide absorption reactor. The gas and liquid phases form a stable Taylor flow inside the tube, and the carbon dioxide absorption rate reaches more than 99.5%. A clear ammonium carbonate solution of about 2.0 mol / L is obtained at the outlet.

[0046] Examples of lithium carbonate precipitation reaction Example

[0047] The reaction temperature was controlled at 20℃ using a constant-temperature oil bath. A magnetic stirrer was turned on, rotating at 800 rpm. A metering pump was simultaneously started, injecting 3.0 mol / L LiCl solution and the ammonium carbonate solution obtained in the preparation example, respectively. The flow rates of both the lithium chloride solution and the ammonium carbonate solution were 1.0 ml / min, with a n(CO3²⁻):n(Li⁺) molar ratio of 1:2. The LiCl solution contained the antisolvent ethanol, with a water-to-ethanol volume ratio of 80:20. The reaction solution remained in the micro-reaction tank for 5 minutes. After the reaction was complete, the lithium carbonate product was aged, filtered, washed, and dried to obtain battery-grade lithium carbonate. The yield of lithium carbonate was calculated to be 72.4%.

[0048] like Figure 4 As shown, the X-ray diffraction (XRD) pattern of battery-grade lithium carbonate in Example 1 perfectly matches the characteristic peaks of reagent-grade lithium carbonate, belonging to pure-phase Li₂CO₃. The full width at half maximum (FWHM) of the main peak near 2θ=30° in the XRD diffraction pattern is approximately 0.35°. Figure 5 The SEM images of battery-grade lithium carbonate show that the obtained product consists of uniformly shaped flaky particles. The particle size was measured using a Mastersizer 3000 laser particle size analyzer via laser diffraction, and the median particle size D of the lithium carbonate particles was detected. 50 Approximately 8.5 μm. ICP-OES analysis showed that all indicators (content of impurities such as Na, Ca, Mg, and Fe) in the product were below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0049] Example 2 Example 2 is similar to Example 1, except that the reaction temperature is 30℃, and the yield of Li₂CO₃ reaches 82.1%. The XRD pattern of lithium carbonate in Example 2 is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating that it belongs to pure-phase Li₂CO₃. The obtained product is uniformly shaped plate-like particles, and the median particle size D of the lithium carbonate particles is... 50 Approximately 9.4 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0050] Example 3 Example 3 is similar to Example 1, except that the reaction temperature is 40℃, and the yield of Li₂CO₃ is 78.5%. The XRD pattern of lithium carbonate in Example 3 is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating that it belongs to pure-phase Li₂CO₃. The obtained product is uniformly shaped flaky particles, with a median particle size D of lithium carbonate particles. 50 Approximately 10.2 μm. All indicators in the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0051] Example 4 Example 4 is similar to Example 1, except that the reaction temperature is 50℃, and the yield of Li₂CO₃ is 71.2%. The XRD pattern of lithium carbonate in Example 4 is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating that it belongs to pure-phase Li₂CO₃. The obtained product is uniformly shaped plate-like particles, and the median particle size D of the lithium carbonate particles is... 50 Approximately 11.5 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0052] Example 5 Example 5 is similar to Example 1, except that the reaction temperature is 60°C. Due to the thermal decomposition of the reactant ammonium carbonate, the concentration decreases, and the yield of Li₂CO₃ drops to 60.5%. The XRD pattern of lithium carbonate in Example 5 is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belongs to pure-phase Li₂CO₃. The obtained product is uniformly shaped flaky particles, with a median particle size D of lithium carbonate. 50 Approximately 12.2 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0053] Example 6 Example 6 is similar to Example 2, except that a constant temperature water bath was used to control the temperature at 30°C, and the magnetic stirring speed was 1000 rpm. The LiCl solution did not contain an antisolvent, and the ethanol content was 0 vol% (pure aqueous phase). After the reaction was completed, the Li₂CO₃ yield was calculated to be 70.2% after drying and weighing. The XRD pattern of lithium carbonate in Example 6 was completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating that it belonged to pure phase Li₂CO₃. The obtained product was uniformly shaped plate-like particles, and the median particle size D of the lithium carbonate particles was... 50 The particle size is 15.4 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is better than the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0054] Example 7 Example 7 is similar to Example 6, except that the ethanol content in the LiCl solution is 10 vol%. With increasing ethanol volume ratio, the Li₂CO₃ yield increases to 75.8%. The XRD pattern of the product is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belongs to pure-phase Li₂CO₃. The obtained product consists of uniformly shaped plate-like particles, with a median particle size D of lithium carbonate particles. 50 The particle size was reduced to 12.1 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) were below 0.001 wt%, which is better than the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0055] Example 8 Example 8 is similar to Example 6, except that the ethanol content in the LiCl solution is 20 vol%. Ethanol further increases the supersaturation of the reaction, increasing the Li₂CO₃ yield to 82.1%. The XRD pattern of the product is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belongs to pure-phase Li₂CO₃. The obtained product consists of uniformly shaped plate-like particles, with a median particle size D of lithium carbonate particles. 50 The particle size was reduced to 8.5 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) were below 0.001 wt%, which is better than the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0056] Example 9 Example 9 is similar to Example 6, except that the ethanol content in the LiCl solution is 25 vol%, the Li₂CO₃ yield is 80.6%, and the XRD pattern of the product is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating that it belongs to pure phase Li₂CO₃. The obtained product consists of relatively uniform flaky particles, with a median particle size D of lithium carbonate particles. 50The particle size is 9.5 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is better than the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0057] Example 10 Example 10 is similar to Example 2, except that the rotation speed of the magnetic stirrer in the continuous flow dynamic microreactor is set to 500 rpm. During the reaction, the system maintains stable operation, and broken lithium carbonate particles can be observed flowing uniformly out of the reactor with the liquid phase at the outlet of the continuous flow dynamic microreactor. After the reaction, the Li₂CO₃ yield is approximately 80%, and the XRD pattern of the product is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belongs to pure-phase Li₂CO₃. The obtained product consists of uniformly shaped plate-like particles, with a median particle size D of lithium carbonate. 50 Approximately 9.8 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0058] Example 11 Example 11 is similar to Example 2, except that the rotation speed of the magnetic stirrer in the continuous flow dynamic microreactor was set to 1500 rpm. The system maintained stable operation, and fragmented lithium carbonate particles were observed flowing uniformly out of the reactor with the liquid phase at the outlet. After the reaction, the Li₂CO₃ yield was approximately 83.5%, and the XRD pattern of the product was completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belonged to pure-phase Li₂CO₃. The obtained product consisted of uniformly shaped plate-like particles, with a median particle size D of lithium carbonate. 50 Approximately 7.9 μm. All indicators in the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0059] Example 12 Example 12 is similar to Example 2, except that n(CO3) in the continuous flow dynamic microreactor is different. 2- ):n(Li⁺) is set to 0.8:1, Li⁺ is insufficient while CO₃²⁻ is insufficient. 2- Excessive amounts, in the form of CO3 2- The yield reached 90%. The XRD pattern of the product was completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belonged to pure-phase Li₂CO₃. The obtained product consisted of uniformly shaped flaky particles, with a median particle size D of lithium carbonate. 50 Approximately 10.0 μm. All indicators in the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0060] Example 13 Example 13 is similar to Example 2, except that n(CO3) in the continuous flow dynamic microreactor is different. 2- ):n(Li⁺) is set to 1.2:1, CO₃²⁻ 2- With a larger excess, the Li₂CO₃ yield reached 88.5%. The XRD pattern of the product was completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belonged to pure-phase Li₂CO₃. The obtained product consisted of uniformly shaped plate-like particles, with a median particle size D of lithium carbonate particles. 50 Approximately 12.2 μm. All indicators in the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0061] Example 14 Example 14 is similar to Example 2, except that n(CO3) in the continuous flow dynamic microreactor... 2- ):n(Li⁺) is set to 1.5:1, CO₃²⁻ 2- With a larger excess, the Li₂CO₃ yield was further increased to 89.2%. The XRD pattern of the product was completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belonged to pure-phase Li₂CO₃. The obtained product consisted of uniformly shaped plate-like particles, with a median particle size D of lithium carbonate particles. 50 Approximately 14.3 μm. All indicators of the product (content of impurities such as Na, Ca, Mg, and Fe) are below 0.001 wt%, which is superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0062] Example 15 Example 15 is similar to Example 13, except that the rotation speed of the magnetic stirrer in the continuous flow dynamic microreactor is set to 1000 rpm. After the reaction is complete, ICP-OES analysis shows that the main component Li₂CO₃ content is 99.58 wt%, and the impurity content is: Na < 0.001 wt%, Fe < 0.0005 wt%, Ca < 0.005 wt%, all of which are superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013). The XRD pattern of the product is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, belonging to pure phase Li₂CO₃. Its particle size distribution D 10 =3.2μm, D 50 =8.5μm, D 90 =18.2μm, exhibiting a normal distribution, with regular plate-like crystals, requiring no further ball milling.

[0063] Example 16 Compared to Example 15, this example uses isopropanol and methanol as antisolvents, while maintaining other operating conditions. The XRD pattern of the product is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, indicating it belongs to pure-phase Li₂CO₃. The addition of isopropanol restricts crystal growth, resulting in a plate-like aggregate of the product. The particle size distribution still exhibits a normal distribution, with a median particle size D. 50 The particle size was reduced to 4.2 μm. This demonstrates that the microstructure of battery-grade lithium carbonate can be precisely controlled by changing the type of antisolvent. Due to the high polarity of methanol, the precipitation rate of lithium carbonate was relatively slow, resulting in a slight decrease in yield to 78.2%. The lithium carbonate crystals were well-developed, with a purity of 99.70 wt%. Impurity content was: Na < 0.001 wt%, Fe < 0.0005 wt%, Ca < 0.005 wt%, all of which are superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0064] Example 17 Compared to Example 15, this example replaces LiCl with 1.5 mol / L Li₂SO₄, and the concentration of n(CO₃) in the continuous flow dynamic microreactor is [not specified]. 2- The ratio of Li⁺ to its ionization (Li⁺) is 1:2. In this example, the lithium carbonate reaction yield reaches 88.9%. This indicates that the process is not significantly affected by the type of anion, and the lithium source used can be adjusted according to the price of raw materials. The XRD pattern of the product is completely consistent with the characteristic peaks of reagent-grade lithium carbonate, belonging to pure-phase Li₂CO₃. Sulfate (SO₄²⁻) 2- As a typical "crystal plane inhibitor," it adsorbs onto the surface of Li2CO3 crystals, preventing the formation of new crystal nuclei and allowing existing crystal nuclei to grow sufficiently, thus reducing the median grain size D. 50 Even when the particle size increases to 9.5 μm, the particle size distribution still exhibits a normal distribution. The main impurity contents in the product are: Na < 0.001 wt%, Fe < 0.0005 wt%, Ca < 0.005 wt%, and all indicators are superior to the industrial battery-grade lithium carbonate standard (YS / T582-2013).

[0065] Example 18 In this embodiment, multiple sets of continuous flow dynamic microreactors are used in series, with the internal volume of each reactor scaled up to 50 mL through similar methods. In this embodiment, a constant-temperature oil bath is used to control the temperature at 30°C, the stirring speed is set to 1000-1200 rpm, the residence time is 5 min, the LiCl concentration is 3.0 mol / L, the ethanol content is 20 vol%, and the n(CO3) content in the continuous flow dynamic microreactor is... 2- The ratio of Li⁺ to Li⁺ is 1:2. This system enables stable continuous production with a daily output of up to 5.5 kg. Testing showed that the XRD pattern of lithium carbonate in this embodiment is the same as that in Example 1, indicating it belongs to pure-phase Li₂CO₃ with a median particle size D. 50=8.5μm, exhibiting a normal distribution, with regular plate-like crystals, requiring no further ball milling. All product indicators (impurity content such as Na, Ca, Mg, and Fe) are below 0.001wt%, exceeding the YS / T582-2013 battery-grade lithium carbonate standard.

[0066] Comparative Example Comparative Example 1 Comparative Example 1 was similar to Example 2, but the stirring speed of the continuous flow dynamic microreactor was set to 0 rpm. 15 seconds after the start of the reaction, particle accumulation occurred in the internal channels of the continuous flow dynamic microreactor, and complete blockage occurred within 3 minutes.

[0067] Comparative Example 2 Comparative Example 2 used a microchannel reactor with an inner diameter of 1.0 mm and fed with the same reactant concentration as in Example 18. After 30 seconds of feeding, crystal bridging blockage occurred at the mixer joint, preventing continuous production. Figure 3a As shown.

[0068] Comparative Example 3 Comparative Example 3 used a microchannel reactor with an inner diameter of 2.0 mm and fed with the same reactant concentration as in Example 18. After 30 seconds of feeding, crystal bridging blockage occurred at the mixer joint, making continuous production impossible. Figure 3b As shown.

[0069] The specific implementations described above can be locally adjusted by those skilled in the art in different ways without departing from the principles and spirit of this invention. The scope of protection of this invention is defined by the claims and is not limited to the specific implementations described above; all implementations within the scope of these claims are bound by this invention. This invention addresses the shortcomings of existing lithium carbonate production technologies, such as low purity, susceptibility to sodium contamination, complex processes, and easy clogging of microreactors. It proposes a method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreactor system. Specifically, the continuous flow coupled microreactor system consists of a capillary microchannel reactor coupled with a continuous flow dynamic microreactor.

Claims

1. A method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system, characterized in that, Includes the following steps: (1) Carbon dioxide gas is introduced into a capillary microchannel reactor containing ammonia water for absorption reaction to generate an ammonium carbonate intermediate solution; (2) The ammonium carbonate intermediate solution and the inorganic lithium salt solution are continuously injected into a continuous flow dynamic microreactor for precipitation reaction to obtain a slurry containing lithium carbonate solid. (3) The slurry is subjected to solid-liquid separation, washing and drying to obtain battery-grade lithium carbonate product.

2. The method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system according to claim 1, characterized in that: The capillary microchannel reactor has an inner diameter of 0.5-2.0 mm and a length of 1.2-20 m.

3. The method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system according to claim 1, characterized in that, In step (1), gaseous carbon dioxide and liquid ammonia react in a microchannel reactor. The flow rate of carbon dioxide is 80-140 ml / min, the flow rate of ammonia is 1-15 ml / min, and the molar concentration of ammonia is 0.5 mol / L-15 mol / L. The molar ratio of carbon dioxide gas to ammonia in ammonia water, n(NH3):n(CO2), is 1.8:1 to 3.1:

1.

4. The method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system according to claim 1, characterized in that, In step (1), the concentration of carbonate in the intermediate solution at the outlet is made to reach 1.0-4.5 mol / L by adjusting the gas-liquid flow ratio.

5. The method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system according to claim 1, characterized in that: In step (2), the inorganic lithium salt is lithium chloride, lithium sulfate or lithium nitrate, and the concentration of the inorganic lithium salt solution is 1.0-5.0 mol / L.

6. The method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system according to claim 1, characterized in that: The continuous flow dynamic microreactor is equipped with a magnetic stirring device, and the stirring speed during the reaction process is controlled at 500-1500 rpm.

7. The method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system according to claim 1, characterized in that: In step (2), the inorganic lithium salt solution contains an antisolvent, which is one or more of methanol, ethanol or isopropanol; the volume percentage of the antisolvent in the inorganic lithium salt solution is 0-30%.

8. The method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system according to claim 1, characterized in that: In step (2), the molar ratio of the ammonium carbonate intermediate to the inorganic lithium salt, n(CO3) 2- ):n(Li⁺) ranges from 1:2 to 1.5:

1.

9. The method for preparing battery-grade lithium carbonate based on a continuous flow coupled microreaction system according to claim 1, characterized in that: The reaction temperature in step (2) is controlled at 20-60℃, and the total residence time of the material in the continuous flow dynamic microreactor is 1-20 min.

10. Battery-grade lithium carbonate prepared by any one of claims 1-9, characterized in that: The battery-grade lithium carbonate is in the form of uniform granules or flakes, with a median particle size D50 of 4-20 μm and Na, Mg, Ca and Fe contents of less than 0.001 wt%.

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