Method for preparing battery-grade lithium carbonate by using silicon-based negative electrode material

Abstract

The invention discloses a method for preparing lithium carbonate by using a silicon-based negative electrode material. The method comprises the following steps: S1, roasting the silicon-based negative electrode material in a carbon dioxide-containing atmosphere; s2, the roasted product is mixed with water, and carbon dioxide is introduced for a carbonization reaction; and S3, after the reaction is finished, carrying out solid-liquid separation, collecting a liquid-phase part, carrying out pyrolytic reaction, after the reaction is finished, carrying out solid-liquid separation again, and collecting a solid-phase part, so as to obtain the lithium carbonate. According to the method, through direct carbonization and pyrolysis after roasting, preparation of high-purity lithium carbonate is achieved, no acid liquor is needed in the whole process, introduction of impurities is effectively avoided, the production process is greatly simplified, and the operability and efficiency of the process are improved.

Description

Technical Field

[0001] The present invention relates to the technical field related to lithium battery material recovery, and in particular to a method for preparing battery-grade lithium carbonate using silicon-based negative electrode materials. Background Art

[0002] Silicon-based anode materials are widely regarded as the star candidate for the next generation of high energy density lithium-ion battery anode materials due to their many significant advantages, such as high theoretical specific capacity, low delithiation potential, environmentally friendly properties, abundant natural resource reserves and relatively low cost. At present, the research on silicon-based anode materials is in a stage of vigorous development, and some research results have been successfully applied to the commercial production of lithium-ion batteries. In view of its ever-expanding application scope, the research on the recycling and utilization of waste silicon-based anode materials is particularly important.

[0003] In order to improve the performance of silicon-based negative electrode materials, researchers have explored a variety of modification methods, one of which is to prepare composite silicon-based negative electrode materials by doping lithium silicates. This type of composite material exhibits high ionic conductivity and ultra-high first charge and discharge efficiency. However, despite its superior performance, the current recycling of this type of negative electrode material is relatively scarce. It is worth noting that the lithium content contained in these materials is not low. With the rapid development of emerging fields such as new energy, nuclear industry, aerospace, etc., the global demand for lithium resources continues to rise. Especially in the context of the current new energy revolution, lithium-ion batteries, as core energy storage technology, are growing in demand at an unprecedented rate, which undoubtedly exacerbates the scarcity of lithium resources. Lithium carbonate, as one of the key raw materials for lithium-ion battery positive electrode materials, its purity and stability are directly related to the performance and safety of the battery. Therefore, recovering lithium from discarded silicon-based negative electrode materials and converting them into high-purity lithium carbonate products can not only significantly increase the added value of battery waste, but also open up new ways to ensure the stable supply of lithium resources.

[0004] Patent application document CN115557520A discloses a method for recovering lithium from lithium silicate waste residues. The method uses hydrofluoric acid to dissolve the waste residues, adds sulfuric acid and heats to volatilize HF to obtain a lithium sulfate solution. However, this method has limitations such as high environmental pollution risk, strong equipment corrosion, and no further preparation into specific lithium products. Therefore, it is not suitable for long-term industrial applications. In addition, most of the current processes for recycling battery materials to prepare battery-grade lithium carbonate generally involve complex acid treatment steps, such as acid leaching and pH adjustment, and the overall process is cumbersome and time-consuming.

[0005] Based on this, it is of great significance to develop a simple and efficient recycling strategy to prepare battery-grade lithium carbonate using silicon-based negative electrode materials. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing lithium carbonate using a silicon-based negative electrode material, which is simple, efficient and can produce lithium carbonate with high purity.

[0007] The method for preparing lithium carbonate using a silicon-based negative electrode material according to an embodiment of the present invention comprises the following steps:

[0008] S1, calcining the silicon-based negative electrode material in a carbon dioxide-containing atmosphere;

[0009] S2, mixing the roasted product with water, and introducing carbon dioxide to carry out a carbonization reaction;

[0010] S3. After the reaction is completed, the solid and liquid are separated, and the liquid phase is collected for pyrolysis reaction. After the reaction is completed, the solid and liquid are separated again, and the solid phase is collected to obtain lithium carbonate.

[0011] According to the method of the embodiment of the present invention, at least the following beneficial effects are achieved: the scheme of the present invention can efficiently and environmentally friendly recover and prepare battery-grade lithium carbonate from silicon-based negative electrode materials. The scheme of the present invention first places the silicon-based negative electrode material in an atmosphere containing carbon dioxide for roasting. The uniqueness of this process is that the lithium silicate in the material can be converted to directly generate lithium carbonate without adding any additives. More importantly, the selected raw materials are simple and do not contain divalent metal elements such as calcium (Ca), magnesium (Mg), nickel (Ni) and other impurities, and the introduction of other external impurities can be cleverly avoided in the entire conversion process, thereby meeting the process requirements for directly preparing high-quality battery-grade lithium carbonate. Compared with the traditional lithium extraction process, the present invention shows significant advantages. The traditional process usually includes a complex acid leaching step, followed by cumbersome impurity removal, pH adjustment, evaporation concentration, lithium precipitation and other links, and the overall process is lengthy and complicated to operate. The present invention realizes the preparation of high-purity lithium carbonate by direct carbonization pyrolysis after roasting, without the need to use acid solution throughout the process, effectively avoiding the introduction of impurities, greatly simplifying the production process, and improving the operability and efficiency of the process. In addition, compared with the related art, compared with the method of extracting lithium from lithium silicate waste residue using hydrofluoric acid (HF), the present invention not only significantly reduces the negative impact on the environment, is more in line with the principles of green chemistry, but is also more suitable for large-scale industrial production. This innovation not only provides a simple and efficient lithium recovery method for silicon-based negative electrode materials containing lithium silicates, but also opens up a new way to recycle such materials, which is of great significance for promoting resource recycling and promoting the sustainable development of the new energy industry.

[0012] According to some embodiments of the present invention, the method further comprises the step of grinding the calcined product.

[0013] According to some embodiments of the present invention, the grinding process is grinding to 50-400 meshes, such as 200 meshes.

[0014] According to some embodiments of the present invention, the lithium in the silicon-based negative electrode material exists in the form of lithium silicate.

[0015] According to some embodiments of the present invention, the lithium silicate comprises Li 2 SiO 3 , Li 2 Si 2 O 5 , Li 4 SiO 4 , Li 6 Si 2 O 7 At least one of .

[0016] According to some embodiments of the present invention, the carbon dioxide concentration in the carbon dioxide-containing atmosphere is 0.03-3% vol.

[0017] According to some embodiments of the present invention, the carbon dioxide-containing atmosphere is an air atmosphere or a mixture of carbon dioxide and other gases, wherein the other gases include at least one of nitrogen and argon. Air can also be directly used as the other gas.

[0018] According to some embodiments of the present invention, the calcination temperature is 200-700°C.

[0019] According to some embodiments of the present invention, the calcination temperature is 400-630°C.

[0020] According to some embodiments of the present invention, the calcination time is 1 to 20 hours.

[0021] According to some embodiments of the present invention, when the roasted product is mixed with water, the liquid-to-solid mass ratio is 5 to 11:1.

[0022] According to some embodiments of the present invention, the carbonization reaction process includes at least one of the following conditions:

[0023] 1) Carbon dioxide purity ≥ 99%;

[0024] 2) Flow rate is 1-5L / min;

[0025] 3) Carbonization time is 1-5h;

[0026] 4) Control the temperature range 20-40℃.

[0027] According to some embodiments of the present invention, the temperature of the pyrolysis reaction is 90-98° C.; and / or the time is 1-4 h.

[0028] According to some embodiments of the present invention, the method further comprises returning the liquid phase after solid-liquid separation in S3 to S2 to replace the water mixed with the roasted product. The filtrate after the pyrolysis reaction can be returned to the carbonization process for recycling, saving resources and being more environmentally friendly.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0031] Figure 1 It is the XRD diagram of the raw material of Example 1 of the present invention.

[0032] Figure 2 This is the XRD diagram of the raw material after calcination in Example 1 of the present invention.

[0033] Figure 3 This is the XRD diagram of the battery-grade lithium carbonate prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present invention. The test methods used in the embodiments are conventional methods unless otherwise specified; the materials, reagents, etc. used, unless otherwise specified, can be reagents and materials obtained from commercial channels. Unless otherwise specified, the same parameter in each embodiment has the same value. The embodiments described below are exemplary and are only used to explain the present invention, and cannot be understood as limitations on the present invention.

[0035] In the description of the present invention, the description with reference to the term "some embodiments" or the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0036] In the description of the present invention, if there is a description of first, second, etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0037] In some embodiments of the present invention, a method for preparing lithium carbonate using a silicon-based negative electrode material is provided, comprising the following steps:

[0038] S1, calcining the silicon-based negative electrode material in a carbon dioxide-containing atmosphere;

[0039] S2, mixing the roasted product with water, and introducing carbon dioxide to carry out a carbonization reaction;

[0040] S3. After the reaction is completed, the solid and liquid are separated, and the liquid phase is collected for pyrolysis reaction. After the reaction is completed, the solid and liquid are separated again, and the solid phase is collected to obtain lithium carbonate.

[0041] In some embodiments of the present invention, the method further comprises the step of grinding the calcined product.

[0042] In some embodiments of the present invention, the grinding process is grinding to 50-400 meshes, such as 200 meshes.

[0043] In some embodiments of the present invention, the lithium in the silicon-based negative electrode material exists in the form of lithium silicate.

[0044] In the composition of silicon-based negative electrode materials, lithium silicates play a pivotal role, and their ion conductivity is particularly outstanding. The innovation of this invention is that through a carefully designed chemical reaction process, the effective release of lithium elements is achieved, paving the way for subsequent convenient extraction and preparation of lithium carbonate. This solution profoundly enhances the recyclability of silicon-based negative electrode materials and significantly improves the efficiency of resource utilization.

[0045] In some embodiments of the present invention, the lithium silicate comprises Li 2 SiO 3 , Li 2 Si 2 O 5 , Li 4 SiO 4 , Li 6 Si 2 O 7 At least one of .

[0046] In some embodiments of the present invention, the volume concentration of carbon dioxide in the carbon dioxide-containing atmosphere is 0.03-3%, such as 0.03%, 0.04%, 0.06%, 0.09%, 1.2%, 1.6%, 1.8%, 2.1%, 2.6% or 3%.

[0047] In view of the differences in the characteristics of lithium silicates under different preparation processes, technicians in this field can flexibly adjust the concentration of carbon dioxide according to actual conditions. By mixing carbon dioxide with other gases (such as other gases in the air, nitrogen or argon), not only the stability of the gas environment during the roasting process is ensured, but also the safety risks that may be caused by the use of a single gas are effectively avoided. The introduction of an atmosphere containing carbon dioxide not only promotes the effective conversion of lithium silicates, but also significantly reduces the potential threat to the environment.

[0048] In some embodiments of the present invention, the carbon dioxide-containing atmosphere is an air atmosphere or a mixture of carbon dioxide and other gases, and the other gases include at least one of nitrogen and argon.

[0049] In some embodiments of the present invention, the calcination temperature is 200-700°C.

[0050] In some embodiments of the present invention, the calcination temperature is 400-630°C.

[0051] Even at room temperature, lithium silicate materials have the ability to capture carbon dioxide, but this process is relatively slow and requires a longer period to reach the saturation point of its adsorption capacity. In addition, the adsorption characteristics of lithium silicate are also affected by the different preparation methods, resulting in different temperature conditions required for the adsorption operation.

[0052] As for the specific conversion temperature of lithium silicate, it can be realized by precisely controlling the calcination temperature within a range of 200 to 700 degrees Celsius (preferably within a range of 400 to 630 degrees Celsius, specifically 420 degrees Celsius, 450 degrees Celsius, 480 degrees Celsius, 500 degrees Celsius, 520 degrees Celsius, 550 degrees Celsius, 480 degrees Celsius, 600 degrees Celsius, 620 degrees Celsius, etc.). Such a temperature setting ensures the conversion efficiency and effectively prevents the problem of excessive sintering or decomposition of the material due to excessive temperature. This sophisticated temperature control strategy not only improves the controllability of the process, but also significantly enhances the quality and stability of the product.

[0053] In some embodiments of the present invention, the calcination time is 1 to 20 hours.

[0054] The holding time can be adjusted according to actual conditions, such as 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, etc. The calcination time of 1 to 20h provides sufficient reaction time for the process and ensures the full conversion of lithium silicate. At the same time, this time range also adapts to the needs of different production scales and efficiencies, and improves the flexibility and applicability of the process.

[0055] In some embodiments of the present invention, when the roasted product is mixed with water, the liquid-to-solid mass ratio is 5 to 11:1, such as 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or 11:1.

[0056] In some embodiments of the present invention, the carbonization reaction process includes at least one of the following conditions:

[0057] 1) Carbon dioxide purity ≥ 99%;

[0058] 2) Flow rate is 1-5L / min;

[0059] 3) Carbonization time is 1-5h;

[0060] 4) Control the temperature range 20-40℃.

[0061] High-purity carbon dioxide means that the impurity content is extremely low, which can reduce the occurrence of side reactions, thereby increasing the yield and purity of the target product. By adjusting the flow rate of carbon dioxide, the rate of the carbonization reaction can be accurately controlled, thereby optimizing the reaction process and avoiding efficiency loss or product quality degradation caused by too fast or too slow. The appropriate flow rate helps to fully mix the reactants and ensure that the carbonization reaction is carried out evenly throughout the reaction system. At the same time, it also helps to optimize the energy consumption of the gas supply system, neither over-consuming resources nor extending the reaction time due to insufficient flow rate. Shorter carbonization time means higher production efficiency, which is conducive to reducing costs and speeding up product launch. Controlling the temperature range of 20-40 ° C can optimize the selectivity of the carbonization reaction, make the target product the main product, reduce the generation of other by-products, and at the same time, the temperature can be at room temperature, saving energy consumption, simplifying process requirements, and reducing production costs. In summary, the ingenious selection of the conditions of the scheme of the present invention helps to improve the efficiency, product quality, production safety, and overall economic and environmental benefits of the carbonization reaction.

[0062] In some embodiments of the present invention, the temperature of the pyrolysis reaction is 90-98°C; and / or the time is 1-4 hours. The pyrolysis reaction temperature is controlled at 90-98°C, which is neither too fast to cause uneven product distribution or increase of by-products, nor too slow to prolong the reaction time and increase energy consumption.

[0063] In some embodiments of the present invention, the method further comprises returning the liquid phase after solid-liquid separation in S3 to S2 to replace the water mixed with the roasted product. The filtrate after the pyrolysis reaction can be returned to the carbonization process for recycling, saving resources and being more environmentally friendly.

[0064] The silicon-based negative electrode powders used in the following examples are all recycled silicon-based negative electrode powders.

[0065] Example 1

[0066] This example provides a method for preparing battery-grade lithium carbonate using silicon-based negative electrode materials. The specific operations are as follows:

[0067] (1) Weigh 300 g of silicon-based negative electrode powder into a crucible, put it into a tube furnace and introduce air, the carbon dioxide concentration in the air is about 0.04% vol, and then roast it at a temperature of 500° C. for 12 h. After the roasting is completed, the material is cooled, taken out, and ground through a 200-mesh sieve;

[0068] (2) Weigh 200 g of the ground roasted material, add 1 L of pure water, stir, and introduce carbon dioxide (vol%>99%) at a flow rate of 1 L / min. The carbonization time is 5 h. The temperature is controlled at about 30°C, and the carbonized liquid is separated by filtration.

[0069] (3) The carbonized liquid is subjected to a pyrolysis reaction at 90° C. for 2 h, followed by solid-liquid separation, and the solid is dried to obtain battery-grade lithium carbonate.

[0070] Example 2

[0071] This example provides a method for preparing battery-grade lithium carbonate using a silicon-based negative electrode material, comprising the following steps:

[0072] (1) Weigh 300 g of silicon-based negative electrode powder into a crucible, put it into a tube furnace and introduce a mixture of carbon dioxide and nitrogen, with a carbon dioxide concentration of about 0.5% vol, and then calcine it at 500° C. for 6 h. After the calcination, take out the material after it cools down and grind it through a 200-mesh sieve;

[0073] (2) Weigh 200 g of the ground roasted material, add 1.2 L of pure water, stir, and introduce carbon dioxide (vol%>99%) at a flow rate of 3 L / min. The carbonization time is 2 h. The temperature is controlled at about 30°C, and the carbonized liquid is separated by filtration.

[0074] (3) The carbonized liquid is subjected to a pyrolysis reaction at 90° C. for 2 h, followed by solid-liquid separation, and the solid is dried to obtain battery-grade lithium carbonate.

[0075] Example 3

[0076] This example provides a method for preparing battery-grade lithium carbonate using a silicon-based negative electrode material, comprising the following steps:

[0077] (1) Weigh 300 g of silicon-based negative electrode powder into a crucible, put it into a tube furnace and introduce a mixture of carbon dioxide and nitrogen, with a carbon dioxide concentration of about 3% vol, and then calcine it at a temperature of 400° C. for 0.5 h. After the calcination, take out the material after it cools down and grind it through a 200-mesh sieve;

[0078] (2) Weigh 200 g of the ground roasted material, add 2 L of pure water, stir, and introduce carbon dioxide (vol%>99%) at a flow rate of 5 L / min. The carbonization time is 4 h. The temperature is controlled at about 30°C, and the carbonized liquid is separated by filtration.

[0079] (3) The carbonized liquid is subjected to a pyrolysis reaction at 95° C. for 3 h, followed by solid-liquid separation, and the solid is dried to obtain battery-grade lithium carbonate.

[0080] Test Case

[0081] 1) X-ray powder diffractometer (XRD)

[0082] The raw materials, intermediate products and final products of the above examples were characterized for structure. The XRD characterization results of the raw materials, calcined products and prepared lithium carbonate in Example 1 are as follows: Figures 1 to 3 As shown in the figure, it can be seen that the raw silicon-based negative electrode material used in the scheme of the present invention contains Li 2 SiO 3 and Si. In addition to some residual Li 2 SiO 3 In addition to Si, there are also converted lithium carbonate and silicon dioxide. The final product is high-purity lithium carbonate.

[0083] 2) Composition determination

[0084] The chemical components in the final product lithium carbonate were measured, and the results are shown in Table 1 below.

[0085] Table 1 Technical indicators of battery-grade lithium carbonate products (mass percentage)

[0086]

[0087]

[0088] As can be seen from Table 1, the purity of lithium carbonate prepared by the scheme of the present invention is as high as 99.7% and above, and the contents of other impurities also strictly meet the national standard requirements of YS / T 582-2013 "Battery Grade Lithium Carbonate". On this basis, in order to further make the particle size and other performance indicators of the product meet the standard requirements of YS / T 582-2013 "Battery Grade Lithium Carbonate", only existing conventional subsequent processing techniques such as crushing are required. After these processing steps, the obtained product can meet the high quality requirements of lithium battery manufacturing.

[0089] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A method for preparing lithium carbonate using a silicon-based negative electrode material, characterized in that: The steps include: S1, calcining the silicon-based negative electrode material in a carbon dioxide-containing atmosphere; S2, mixing the roasted product with water, and introducing carbon dioxide to carry out a carbonization reaction; S3. After the reaction is completed, the solid and liquid are separated, and the liquid phase is collected for pyrolysis reaction. After the reaction is completed, the solid and liquid are separated again, and the solid phase is collected to obtain lithium carbonate.

2. The method according to claim 1, characterized in that: The method further comprises the step of grinding the calcined product to a size of 50 to 400 meshes.

3. The method according to claim 1, characterized in that: The lithium in the silicon-based negative electrode material exists in the form of lithium silicate.

4. The method according to claim 3, characterized in that: The lithium silicate includes at least one of Li2SiO3, Li2Si2O5, Li4SiO4, and Li6Si2O7.

5. The method according to claim 1, characterized in that: The volume concentration of carbon dioxide in the carbon dioxide-containing atmosphere is 0.03-3%.

6. The method according to claim 1, characterized in that: The carbon dioxide-containing atmosphere is an air atmosphere or a mixed atmosphere of carbon dioxide and other gases, and the other gas is one of air, nitrogen and argon.

7. The method according to any one of claims 1 to 6, characterized in that: The calcination temperature is 200-700° C.; and / or the calcination time is 1-20 hours.

8. The method according to any one of claims 1 to 6, characterized in that: When the roasted product is mixed with water, the liquid-to-solid mass ratio is 5 to 11:

1.

9. The method according to any one of claims 1 to 6, characterized in that: The carbonization reaction process includes at least one of the following conditions: 1) Carbon dioxide purity ≥ 99%; 2) Flow rate is 1-5L / min; 3) Carbonization time is 1-5h; 4) Control the temperature range 20-40℃.

10. The method according to any one of claims 1 to 6, characterized in that: The temperature of the pyrolysis reaction is 90-98° C.; and / or the time is 1-4 hours.

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