A lithium-ion sieve and its preparation method

Abstract

This invention discloses a lithium-ion sieve and its preparation method, belonging to the field of lithium-ion sieve technology. The molecular formula of this lithium-ion sieve is Li. 1.33 R x Mn 1.67‑x O4, wherein 0.05≤x≤0.25, and R includes at least three doping elements; the lithium-ion sieve has a spinel structure. This lithium-ion sieve has a compact and stable crystal structure, exhibiting superior cycling performance, low manganese dissolution rate, high lithium-ion selectivity, and long service life. The preparation method of this lithium-ion sieve includes: mixing a manganese source and a lithium source according to the predetermined proportions of elements in the molecular formula, and then calcining the mixture; the manganese source contains Mn and R. This preparation method is simple, easy to operate, and can effectively prepare lithium-ion sieves with the above-mentioned effects, making it suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion sieve technology, and more specifically, to a lithium-ion sieve and its preparation method. Background Technology

[0002] Adsorption is an emerging lithium extraction technology with high selectivity, high recovery rate, and simple process. It can separate impurities while extracting lithium, and its core technology lies in the performance of the adsorbent. Currently, the most promising adsorbents are manganese-based, titanium-based, and aluminum-based lithium-ion sieve adsorbents. Aluminum-based adsorbents are not suitable for highly alkaline solutions. Titanium-based adsorbents have been studied extensively for lithium extraction from lithium precipitation mother liquor recently, but they easily introduce titanium impurities. Furthermore, titanium-based adsorbents have slow ion exchange rates, resulting in long adsorption-desorption processes. Generally, heating is required to shorten the adsorption-desorption time, leading to high energy consumption. During desorption, the ion sieve crystal structure gradually changes, reducing selectivity for lithium, and performance gradually deteriorates during cycling. Loading the lithium-ion sieve onto a matrix can suppress this transformation to some extent. However, because titanium-based lithium-ion sieves themselves have slow ion exchange rates, loading and molding further slows down the ion exchange rate, introducing other impurities and resulting in excessively long process times.

[0003] Manganese-based lithium ion sieves possess both high adsorption capacity and adsorption depth, along with extremely fast ion exchange rates. These rates can be further increased under heating conditions, resulting in short adsorption-desorption processes. However, existing manganese-based lithium ion sieve materials suffer from poor cycleability and short lifespan due to the thermal migration of lithium ions during desorption, which disrupts the sieve's crystal structure and leads to significant manganese loss. This limits their application.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium-ion sieve and its preparation method to solve or improve the above-mentioned technical problems.

[0006] This application can be implemented as follows:

[0007] Firstly, this application provides a lithium-ion sieve with the molecular formula Li. 1.33 R x Mn 1.67-x O4, wherein 0.05≤x≤0.25, and R includes at least three doping elements; the lithium ion sieve has a spinel structure.

[0008] In an optional implementation, R includes at least three elements selected from Zn, Cu, Co, Fe, Cr, Ni, and Mg.

[0009] In an optional implementation, R includes at least Zn, Cu, and Co.

[0010] In an optional implementation, the molar ratio of Zn, Cu and Co in R is from 1:0.1:0.03 to 1:0.2:0.06.

[0011] In an optional embodiment, the lithium-ion sieve further includes at least one of the following features:

[0012] Feature 1: In lithium-ion sieves, the molar ratio of Mn to R is 1:0.03 to 1:0.25;

[0013] Feature 2: The average particle size of the lithium-ion sieve is 3-30 μm;

[0014] Feature 3: The actual saturated adsorption capacity of the lithium ion sieve is 13-22 mg / g;

[0015] Feature 4: The adsorption capacity of the lithium ion sieve after 2 minutes of adsorption at room temperature is not less than 90% of the saturation capacity;

[0016] Feature 5: The total manganese loss rate of the lithium-ion screen after 15 cycles does not exceed 0.54%;

[0017] Feature 6: After 15 cycles of use, the total loss rate of R ions in the lithium ion sieve does not exceed 0.02%;

[0018] Feature 7: The lithium elution rate of the lithium ion sieve is not less than 90%.

[0019] Secondly, this application provides a method for preparing a lithium-ion sieve as described in any of the foregoing embodiments, comprising the following steps: mixing a manganese source and a lithium source according to the proportion of each element in a preset molecular formula, and then calcining the mixture; the manganese source contains Mn and R.

[0020] In an optional embodiment, the molar ratio of Li in the lithium source to Mn in the manganese source is 0.9:1 to 1.1:1.

[0021] In an optional embodiment, the ratio of the total molar amount of manganese and R elements in the manganese source to the molar amount of lithium elements in the lithium source is 1:0.9 to 1:1.1.

[0022] In an optional implementation, the ratio of the total molar amount of manganese and R elements in the manganese source to the molar amount of lithium elements in the lithium source is 1:1.

[0023] In an optional embodiment, the lithium source includes at least one of lithium hydroxide and lithium carbonate, preferably lithium carbonate.

[0024] In optional implementations, the mixing method includes dry mixing or wet mixing.

[0025] In an optional implementation, the mixing method is wet mixing.

[0026] In an optional embodiment, the solvent used for wet mixing includes at least one of water and ethanol, preferably ethanol.

[0027] In an optional embodiment, the total mass of the manganese and lithium sources is related to the volume of the solvent in a ratio of 30g:100mL to 50g:100mL.

[0028] In an optional embodiment, calcination includes at least one of the following features:

[0029] Feature 1: The roasting temperature is 450-550℃, preferably 500℃;

[0030] Feature 2: The roasting time is 6-10 hours, preferably 8 hours;

[0031] Feature 3: The heating rate is 3-8℃ / min, preferably 5℃ / min.

[0032] In an optional embodiment, the mixture is further pre-roasted before roasting;

[0033] Pre-baked includes at least one of the following characteristics:

[0034] Feature 1: The pre-calcination temperature is 180-230℃, preferably 200℃;

[0035] Feature 2: The pre-calcination time is 1-3 hours, preferably 2 hours;

[0036] Feature 3: The heating rate is 8-10℃ / min, preferably 10℃ / min.

[0037] In an optional embodiment, the roasted product is further eluted.

[0038] In an optional embodiment, the eluent used for elution is an acid; preferably, the acid used includes at least one of hydrochloric acid and sulfuric acid.

[0039] In an optional implementation, the elution temperature is 25-60°C.

[0040] In an optional implementation, the elution method is dynamic acid replenishment elution; preferably, the pH of the eluent is maintained at 1.5-2.0 during the elution process.

[0041] In an optional implementation, the eluted solids may also be washed with water and dried.

[0042] In an optional implementation, the drying temperature does not exceed 80°C.

[0043] The beneficial effects of this application include:

[0044] This application utilizes a small amount of at least three elements to dope a lithium-ion sieve. Through the complementary interaction of dopant elements, structural deformation is suppressed while ion stability is improved, and the loss of dopant ions is reduced, significantly extending the sieve's lifespan. Furthermore, this sieve maximizes capacity retention while increasing the ion diffusion rate. Consequently, the lithium-ion sieve exhibits low dissolution rate, high lithium-ion selectivity, excellent cycle performance and stability, and a long lifespan. The preparation method of this lithium-ion sieve is simple, easy to operate, and suitable for industrial production. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, 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 the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is the XRD pattern of the lithium carbonate source ion sieve precursor in Example 2 of this application;

[0047] Figure 2 This is a particle size distribution diagram of the ion sieve precursor in Example 2 of this application;

[0048] Figure 3 This is a graph showing the cycling performance of the manganese-based lithium ion sieve in Example 2 of this application;

[0049] Figure 4 The XRD pattern of the ion sieve precursor in Comparative Example 1 of this application;

[0050] Figure 5 This is a particle size distribution diagram of the ion sieve precursor in Comparative Example 1 of this application;

[0051] Figure 6 The diagram shows the cycle performance of the manganese-based lithium ion sieve in Comparative Example 1 of this application.

[0052] Figure 7 This is a particle size distribution diagram of the ion sieve precursor in Comparative Example 3 of this application. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0054] The lithium-ion sieve and its preparation method provided in this application are described in detail below.

[0055] This application proposes a lithium-ion sieve with the molecular formula Li. 1.33 R x Mn 1.67-x O4, wherein 0.05≤x≤0.25, and R includes at least three doping elements; the lithium ion sieve has a spinel structure.

[0056] It should be noted that currently, three common methods are used to mitigate the manganese loss problem in manganese-based lithium ion sieve materials: molding (granulation, film formation, etc.), ion doping, and loading. However, molding significantly reduces the adsorption capacity and ion exchange rate, while loaded materials suffer from severe powder shedding and short service life. This application improves the ion sieve cell parameters by employing ion doping, utilizing inter-element interactions and element substitution to stabilize the ion sieve lattice and thus extend the material's service life.

[0057] The inventors proposed that, in the case of conventional spinel-type manganese-based ion sieves, the tetrahedral and octahedral voids are not filled, and most of the voids are not occupied by metal ions, which provide favorable conditions for ion doping.

[0058] In the lithium-ion sieve proposed in this application, the doping amount of element R is relatively small, which effectively ensures that the doped ions enter the main phase lattice of the material, change the lattice parameters, and create vacancies in the lattice, thus enabling the lithium-ion sieve to provide lithium for lithium production. + The diffusion of ions provides more or wider channels, reducing ion diffusion resistance and increasing ion transport rate. However, excessive doping can severely affect the main phase structure, easily causing lattice collapse, and also easily generating impurity phases.

[0059] Furthermore, improper selection or combination of doping elements can not only reduce the adsorption capacity of the ion sieve, but also easily lead to the loss of doped ions during the recycling process.

[0060] In this application, the dopant element R includes at least three elements selected from Zn, Cu, Co, Fe, Cr, Ni, and Mg. Each of these elements has a different ionic radius, and the difference in ionic size leads to variations in bond length and bond angle, resulting in different changes to the lattice parameters.

[0061] For reference, in the aforementioned lithium-ion sieve, the molar ratio of Mn to R can be from 1:0.03 to 1:0.25, such as 1:0.03, 1:0.05, 1:0.09, 1:0.1, 1:0.15, 1:0.18, 1:0.2, 1:0.22, or 1:0.25, or any other value within the range of 1:0.03 to 1:0.25. Doping with elements within this ratio range can generate sufficient vacancies without causing lattice distortion and can effectively reduce the amount of impurity phases generated.

[0062] In some alternative implementations, R includes at least Zn, Cu, and Co. That is, R may consist only of Zn, Cu, and Co, or other doping elements may be added to Zn, Cu, and Co. When R includes Zn, Cu, and Co simultaneously, the molar ratio of Zn, Cu, and Co can be from 1:0.1:0.03 to 1:0.2:0.06, such as 1:0.1:0.03, 1:0.1:0.04, 1:0.1:0.05, 1:0.1:0.06, 1:0.15:0.03, 1:0.15:0.04, 1:0.15:0.05, 1:0.15:0.06, 1:0.2:0.03, 1:0.2:0.04, 1:0.2:0.05, or 1:0.2:0.06, or any other value within the range of 1:0.1:0.03 to 1:0.2:0.06.

[0063] By using a zinc-copper-cobalt multi-ion composite doping method, appropriate proportions of zinc, copper, and cobalt ions can complement each other structurally through interaction. This suppresses crystal structure deformation while improving ion stability and reducing dopant ion loss, thus significantly extending the service life of the ion sieve. Furthermore, this ion sieve maximizes capacity retention while also increasing the ion diffusion rate.

[0064] In some embodiments, the average particle size of the lithium-ion sieve is 3-30 μm, such as 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm or 30 μm, or any other value in the range of 3-30 μm.

[0065] If the average particle size of the lithium-ion sieve is too large, the specific surface area of ​​the lithium-ion sieve will be smaller, and the exchange capacity will be lower.

[0066] In some implementations, the actual saturated adsorption capacity of the lithium-ion sieve is 13-22 mg / g.

[0067] In some embodiments, the adsorption capacity of the lithium ion sieve after adsorption for 2 minutes at room temperature is not less than 90% of the saturation capacity.

[0068] In some implementations, the total manganese loss rate of the lithium-ion screen after 15 cycles does not exceed 0.54%.

[0069] In some implementations, after 15 cycles of use, the total dissolution rate of R ions in the lithium ion sieve does not exceed 0.02%, with almost no capacity loss.

[0070] In some embodiments, the lithium elution rate of the lithium-ion sieve is not less than 90%. Here, "lithium elution rate" can also be understood as "lithium desorption rate." This lithium elution rate is specific to Li... + The lithium ion sieve was continuously stirred at 25°C, and acid was added to maintain the pH of the solution at around 1.5 until the pH stabilized. The elution rate corresponding to an elution time of 10 minutes was recorded.

[0071] Building upon the above, the lithium-ion sieve provided in this application has a compact and stable crystal structure, which reduces changes in lattice gaps caused by lithium-ion thermal migration. This results in a high lithium-ion elution rate and good adsorption capacity, ensuring high selectivity for lithium-ions and improving ion diffusion and exchange rates. Furthermore, the stable structural framework formed by multi-ion doping reduces the loss rate of dopant ions while maintaining a low manganese ion dissolution rate. This allows the ion sieve to retain relatively stable performance even after repeated use, greatly improving its recyclability, increasing its lifespan, and reducing production costs for enterprises.

[0072] Accordingly, this application also provides a method for preparing the above-mentioned lithium-ion sieve, which may include the following steps: mixing manganese source and lithium source according to the proportion of each element in the preset molecular formula, and then calcining the mixture.

[0073] The manganese source contains Mn and R.

[0074] In some embodiments, the manganese source is workshop manganese slag containing trace amounts of zinc, copper, and cobalt ions (the main component is MnCO3). In other embodiments, the use of other forms of manganese- and R-containing materials as manganese sources is not excluded.

[0075] It should be noted that the short service life of manganese-based lithium ion sieve materials is usually due to the instability of the ion sieve structure. On the one hand, Mn 3+ This causes the oxygen octahedral structure formed by the surrounding oxygen atoms to elongate, transforming from a cubic phase to a tetragonal phase, resulting in structural distortion. This structural deformation alters the original lithium-ion insertion / extraction sites and migration channels, hindering reversible lithium-ion transport. On the other hand, as lithium ions are extracted and inserted, the crystal lattice undergoes a certain degree of contraction and expansion, gradually changing the lattice hole spacing and gradually reducing the selectivity for lithium.

[0076] This application stabilizes the ion sieve lattice by utilizing the interaction between the transition element ions zinc, copper, and cobalt contained in manganese slag. On the one hand, the addition of Zn, Cu, and Co does not alter the original crystal structure, but rather replaces a portion of the Mn. 3+ Effectively reduced Mn 3+ The disproportionation reaction inhibits the Jahn-Teller effect, increases the average strength of Mn-O bonds, strengthens the material's framework structure, and makes Mn... 3+ The disproportionation of ions improves structural instability, thus significantly reducing manganese dissolution. On the other hand, the addition of Zn and Cu lowers the lattice constant by changing the ionic radius, making the cubic structure more stable. Simultaneously, the binding energy of the Li-O bonds weakens, reducing the likelihood of Li dissolution. + Diffusion resistance in the crystal lattice is beneficial to the lithium-ion insertion / extraction process. Furthermore, ion doping reduces the mixing of Li and Mn, minimizing obstacles to Li... + The number of Mn ions extracted / intercalated significantly promoted the extraction / intercalation of the ion sieve. Taking Li... 1.33 Mn 1.67 Taking the O4-type ion sieve as an example, the multi-element doping scheme of this application can increase the Li / H reverse exchange process, which was originally only about 60%, to about 92%, making the lithium-ion migration channel more stable and greatly improving the ion diffusion rate while increasing lithium-ion selectivity. Moreover, the multi-ion doping provided by this application also solves the problem of easy ion loss in single-phase ion doping, and improves the stability of the ion sieve crystal structure.

[0077] In this application, the lithium source may, by way of example but not by way of limitation, include at least one of lithium hydroxide and lithium carbonate. In some more typical embodiments, lithium carbonate may be used as the lithium source.

[0078] For reference, the molar ratio of Li in the lithium source to Mn in the manganese source is 0.9:1 to 1.1:1, such as 0.9:1, 0.95:1, 1:1, 1.05:1 or 1.1:1, or any other value in the range of 0.9:1 to 1.1:1.

[0079] If the molar ratio of Li in the lithium source to Mn in the manganese source is inappropriate, it will cause the crystal form of the ion sieve to change, making it impossible to obtain a spinel crystal form with high purity.

[0080] In some embodiments, the ratio of the total molar amount of manganese and R elements in the manganese source to the molar amount of lithium elements in the lithium source can be from 1:0.9 to 1:1.1, such as 1:0.9, 1:0.95, 1:1, 1:1.05, or 1:1. In some more typical embodiments, the ratio of the total molar amount of manganese and R elements in the manganese source to the molar amount of lithium elements in the lithium source is 1:1.

[0081] In this application, the mixing method of lithium source and manganese source may include dry mixing or wet mixing.

[0082] Dry mixing can involve grinding and mixing manganese and lithium sources.

[0083] Wet mixing can involve mixing the lithium source in a solvent, then adding the manganese source and stirring until homogeneous, followed by filtration, drying, crushing, and grinding.

[0084] The particle size of the product after grinding is not less than 100 mesh.

[0085] The solvent used for wet mixing may, by way of example but not limitation, include at least one of water and ethanol. In some more typical embodiments, the solvent used for wet mixing is ethanol. The relationship between the total mass of the manganese and lithium sources and the volume of the solvent is 30 g:100 mL to 50 g:100 mL, such as 30 g:100 mL, 35 g:100 mL, 40 g:100 mL, 45 g:100 mL, or 50 g:100 mL, etc. If the liquid-to-solid ratio is too high, it will increase the filtration throughput; if the liquid-to-solid ratio is too low, it will cause uneven mixing of the lithium and manganese sources.

[0086] Of the above mixing methods, dry mixing is simple to operate; wet mixing requires the use of solvents and is relatively more complicated to operate, but wet mixing can make the lithium source and manganese source mix more evenly.

[0087] In this application, the calcination temperature can be 450-550℃, such as 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, or 550℃, or any other value within the range of 450-550℃. In some typical embodiments, the calcination temperature is 500℃.

[0088] If the calcination temperature is below 450℃, it is easy to prevent the formation of spinel structure; if the calcination temperature is above 550℃, it will affect the crystal form of the product after calcination, and the product after calcination will easily become a mixture of layered structure and spinel structure. At the same time, it is easy to cause the crystal to grow too large and cause serious agglomeration, which will deteriorate its performance (such as structural stability, cycle performance, service life, etc.).

[0089] The roasting time can be 6-10 hours, such as 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, or any other value within the range of 6-10 hours. In some typical embodiments, the roasting time is 8 hours.

[0090] The heating rate during the above-mentioned roasting process can be 3-8℃ / min, such as 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, or 8℃ / min, or any other value within the range of 3-8℃ / min. If the heating rate is too slow, the heating time will be too long, and the material will begin to react before reaching the target temperature, reducing the performance of the roasted product. If the heating rate is too fast, the roasted material is prone to uneven internal and external and local temperature distribution, resulting in uneven performance of the roasted product. In some typical embodiments, the heating rate during the roasting process is 5℃ / min.

[0091] The above-mentioned calcination process involves a slow heating rate and a long reaction time, which allows the lithium and manganese sources to react fully, forming a calcined product with a well-formed crystal structure and stable structure.

[0092] In some embodiments, the mixture may be pre-roasted before roasting.

[0093] The pre-calcination temperature can be 180-230℃, such as 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, 220℃, 225℃, or 230℃, or any other value within the range of 180-230℃. In some typical embodiments, the pre-calcination temperature is 200℃.

[0094] The pre-calcination time can be 1-3 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, or any other value within the range of 1-3 hours. In some typical embodiments, the pre-calcination time is 2 hours.

[0095] The heating rate during the pre-calcination process can be 8-10℃ / min, such as 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, or 10℃ / min, or any other value within the range of 8-10℃ / min. In some typical embodiments, the heating rate during the pre-calcination process is 10℃ / min.

[0096] Pre-calcining in the manner described above results in a rapid heating rate and a long reaction time, which facilitates the rapid and uniform mixing of the lithium and manganese sources, thereby improving the subsequent calcination effect.

[0097] As mentioned above, this application uses a two-stage roasting process that combines pre-roasting and roasting, which is sufficient to allow the manganese source and lithium source to react fully. This process is less likely to generate impurity phases than multi-stage roasting (such as three-stage roasting) and is also less time-consuming.

[0098] Further, the roasted product is eluted.

[0099] For reference, the eluent used for elution is an acid, which may include at least one of hydrochloric acid and sulfuric acid.

[0100] The elution temperature can be 25-60℃, such as 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃, or any other value within the range of 25-60℃.

[0101] The higher the elution temperature, the better the Li + The faster the exchange rate, but the higher the temperature, the higher the manganese loss rate.

[0102] The solid-liquid ratio during elution should not exceed 1g:10mL (e.g., 5g:10mL). If the solid-liquid ratio is too high, the lithium concentration in the eluent will be too high, thus inhibiting lithium elution. The elution time can be 10min-180min.

[0103] In some implementations, the elution method is dynamic acid replenishment elution, or the pH value of the eluent can be maintained at 1.5-2.0 during the elution process.

[0104] Through elution, the H in the acid is removed. + Li in the calcination product + Replace it.

[0105] Further, the eluted solids are washed with water and dried.

[0106] Wash with water until the washing solution is neutral.

[0107] The drying temperature should not exceed 80℃, and can be 80℃, 75℃, 70℃, 65℃, 60℃, 55℃, 50℃, etc. If the drying temperature exceeds 80℃, it can easily lead to a decrease in the material's cycle performance.

[0108] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0109] Example 1

[0110] S1: Take 12.43g of lithium hydroxide and mix it in 10mL of ethanol. Add 60.00g of manganese slag (Zn:Cu:Co=20.78:3.36:1) and stir again. Filter and dry to obtain the mixture.

[0111] The manganese slag contains 90.95% Mn, 7.48% Zn, 1.21% Cu, and 0.36% Co. The total molar ratio of Mn, Zn, Cu, and Co in the manganese slag to the molar ratio of Li in lithium hydroxide is 1:1.

[0112] S2: The mixture is pre-calcined in a muffle furnace at a temperature of 200℃, a heating rate of 10℃ / min, and a pre-calcination time of 2h to obtain the pre-calcined product.

[0113] S3: The pre-calcined product was calcined at 500℃ with a heating rate of 5℃ / min for 8 hours to obtain an ion sieve precursor with the molecular formula Li. 1.33 (Zn 0.125 Cu 0.02 Co 0.006 Mn 1.519 O4.

[0114] S4: Grind the ion sieve precursor and pass it through a 100-mesh sieve. Take 10g of the ground and sieved precursor into 200mL of water, stir continuously at 25℃, and add acid to maintain the pH of the solution at about 1.5 until the pH stabilizes. The elution time is 10min to achieve an elution rate of about 91.84% and a manganese loss rate of 0.29%.

[0115] S5: After elution, filter the solid obtained by filtration and wash it with water until the washing solution is nearly neutral. Then filter and dry the washed solid (60℃), grind it through a 100-mesh sieve to obtain a manganese-based lithium ion sieve with an average particle size of 10μm.

[0116] The saturated adsorption capacity of the manganese-based lithium ion sieve is 14.63 mg / g; the adsorption capacity measured after adsorption at 25℃ for 2 min is 13.46 mg / g, which is about 92% of the saturated capacity; after 15 cycles of use, the total manganese dissolution rate of the lithium ion sieve is 0.44%, and the total dissolution rate of doped ions is 0.014%.

[0117] Manganese-based lithium ion sieves that were not circulated and those that were circulated 15 times were used to measure their selectivity for lithium and sodium. Specifically, they were adsorbed in lithium solution containing 20 g / L sodium (Na:Li = 40:1) for 2 min, and the adsorption capacity of each for lithium and sodium was measured. The results are shown in Table 1.

[0118] Table 1 Selectivity before and after cycling

[0119]

[0120] Example 2

[0121] S1: Take 19.13g of lithium carbonate and mix it in 20mL of ethanol. Add 60.00g of manganese slag (Zn:Cu:Co=22.33:2.9:1) and stir again. Filter and dry to obtain the mixture.

[0122] The manganese slag contains 89.51% Mn, 8.93% Zn, 1.16% Cu, and 0.40% Co. The total molar ratio of Mn, Zn, Cu, and Co in the manganese slag to the molar ratio of Li in lithium carbonate is 1:1.

[0123] S2: The mixture was pre-calcined in a muffle furnace at a temperature of 200℃, a heating rate of 10℃ / min, and a pre-calcination time of 2 hours to obtain a pre-calcined product with the molecular formula Li. 1.33 (Zn 0.143 Cu 0.02 Co 0.007 Mn 1.50 O4.

[0124] S3: The pre-calcined product was calcined at 500℃, with a heating rate of 5℃ / min, for 8 hours to obtain the ion sieve precursor. Its XRD pattern is shown below. Figure 1 As shown, the particle size distribution diagram is as follows: Figure 2 As shown.

[0125] S4: Grind the ion sieve precursor and pass it through a 100-mesh sieve. Take 10g of the ground and sieved precursor into 200mL of water, stir continuously at 25℃, and add acid to maintain the pH of the solution at about 1.5 until the pH stabilizes. The elution time is 10min to achieve an elution rate of about 92.26% and a manganese loss rate of 0.14%.

[0126] S5: After elution, filter the solid obtained by filtration and wash it with water until the washing solution is nearly neutral. Then filter and dry the washed solid (60℃), grind it through a 100-mesh sieve to obtain a manganese-based lithium ion sieve with an average particle size of 10.74μm.

[0127] The manganese-based lithium ion sieve has a particle size range of 3-40 μm and a uniform particle size distribution.

[0128] The circulation performance diagram of this manganese-based lithium ion sieve is shown below. Figure 3 As shown, the saturated adsorption capacity of this manganese-based lithium ion sieve is 21.03 mg / g, and the adsorption capacity measured after adsorption at 25℃ for 2 min is 19.45 mg / g, which is approximately 92.5% of the saturated capacity. It maintains a stable adsorption capacity after 15 cycles, with a total manganese dissolution rate of 0.35% and a total dopant ion dissolution rate of 0.011%, demonstrating excellent regeneration capabilities.

[0129] Manganese-based lithium ion sieves that were not circulated and those that were circulated 15 times were used to measure their selectivity for lithium and sodium. Specifically, they were adsorbed in lithium solution containing 20 g / L sodium (Na:Li = 40:1) for 2 min, and the adsorption capacity of each for lithium and sodium was measured. The results are shown in Table 2.

[0130] Table 2 Selectivity before and after cycling

[0131]

[0132] As can be seen from Table 2, the manganese-based lithium ion sieve provided in this embodiment still has high selectivity for lithium after multiple cycles.

[0133] Example 3

[0134] S1: Take 17.22g of lithium carbonate and mix it in 20mL of ethanol. Add 60.00g of manganese slag (Zn:Cu:Co=1:0.1:0.03) and stir again. Filter and dry to obtain the mixture.

[0135] The manganese slag contains 91.74% Mn, 7.31% Zn, 0.73% Cu, and 0.22% Co. The molar ratio of Mn to R(Zn+Cu+Co) in the manganese slag is 1:0.09, and the ratio of the total molar amount of Mn, Zn, Cu, and Co in the manganese slag to the molar amount of Li in lithium carbonate is 1:0.9.

[0136] S2: The mixture is pre-calcined in a muffle furnace at a temperature of 180°C, a heating rate of 8°C / min, and a pre-calcination time of 3 hours to obtain the pre-calcined product.

[0137] S3: The pre-calcined product was calcined at 450℃ with a heating rate of 3℃ / min for 10 hours to obtain an ion sieve precursor with the molecular formula Li. 1.33 (Zn 0.137 Cu 0.018 Co 0.005 Mn 1.51 O4.

[0138] S4: Grind the ion sieve precursor and pass it through a 100-mesh sieve. Take 10g of the ground and sieved precursor into 200mL of water, stir continuously at 40℃, add acid to maintain the pH of the solution at around 2.0 until the pH stabilizes, and the elution time is 10min to achieve an elution rate of about 90.41% and a manganese loss rate of 0.28%.

[0139] S5: After elution, filter the solid obtained by filtration and wash it with water until the washing solution is nearly neutral. Then filter and dry the washed solid (70℃), grind it through a 100-mesh sieve to obtain a manganese-based lithium ion sieve with an average particle size of 8.4μm.

[0140] The saturated adsorption capacity of this manganese-based lithium ion sieve is 15.73 mg / g. After adsorption at 25℃ for 2 min, the adsorption capacity measured is 14.52 mg / g, which is approximately 92.34% of the saturated capacity. It maintains a stable adsorption capacity after 15 cycles, with a total manganese dissolution rate of 0.52% and a total dopant ion dissolution rate of 0.008%.

[0141] Manganese-based lithium ion sieves that were not circulated and those that were circulated 15 times were used to measure their selectivity for lithium and sodium. Specifically, they were adsorbed in lithium solution containing 20 g / L sodium (Na:Li = 40:1) for 2 min, and the adsorption capacity of each for lithium and sodium was measured. The results are shown in Table 3.

[0142] Table 3 Selectivity before and after cycling

[0143]

[0144] Example 4

[0145] S1: Take 21.02g of lithium carbonate and mix it in 20mL of ethanol. Add 60.00g of manganese slag (Zn:Cu:Co=1:0.2:0.06) and stir again. Filter and dry to obtain the mixture.

[0146] The manganese slag contains 88.50% Mn, 9.14% Zn, 1.82% Cu, and 0.54% Co. The molar ratio of Mn to R(Zn+Cu+Co) in the manganese slag is 1:0.13. The ratio of the total molar amount of Mn, Zn, Cu, and Co in the manganese slag to the molar amount of Li in lithium carbonate is 1:1.1.

[0147] S2: The mixture is pre-calcined in a muffle furnace at a temperature of 230°C, a heating rate of 9°C / min, and a pre-calcination time of 1 h to obtain the pre-calcined product.

[0148] S3: The pre-calcined product is calcined at a temperature of 550℃, a heating rate of 8℃ / min, and a calcination time of 6h to obtain the ion sieve precursor.

[0149] S4: Grind the ion sieve precursor and pass it through a 100-mesh sieve. Take 10g of the ground and sieved precursor into 200mL of water, stir continuously at 60℃, and add acid to maintain the pH of the solution at about 1.8 until the pH stabilizes. The elution time is 10min to achieve an elution rate of about 93.65% and a manganese loss rate of 0.29%.

[0150] S5: After elution, filter the solid obtained by filtration. Wash the solid with water until the washing solution is nearly neutral. Then filter and dry the washed solid (at 80°C), grind it through a 100-mesh sieve, and obtain a manganese-based lithium ion sieve with an average particle size of 10.17 μm and a molecular formula of Li. 1.33 (Zn 0.092 Cu 0.021 Co 0.007 Mn 1.55 O4.

[0151] The saturated adsorption capacity of this manganese-based lithium ion sieve is 17.97 mg / g. After adsorption at 25℃ for 2 min, the measured adsorption capacity is 17.24 mg / g, which is approximately 95.94% of the saturated capacity. It maintains a stable adsorption capacity after 15 cycles, with a total manganese dissolution rate of 0.48% and a total dopant ion dissolution rate of 0.011%.

[0152] Manganese-based lithium ion sieves that were not circulated and those that were circulated 15 times were used to measure their selectivity for lithium and sodium. Specifically, they were adsorbed in lithium solution containing 20 g / L sodium (Na:Li = 40:1) for 2 min, and the adsorption capacity of each for lithium and sodium was measured. The results are shown in Table 4.

[0153] Table 4 Selectivity before and after cycling

[0154]

[0155] Comparative Example 1

[0156] The difference between this comparative example and Example 2 is that commercial manganese carbonate is used instead of manganese slag, while all other supplements and conditions are the same as in Example 2.

[0157] In this method, the XRD pattern of the lithium-ion sieve precursor obtained by S3 is as follows: Figure 4 As shown, the particle size distribution diagram is as follows: Figure 5 As shown in Figure S4, an elution time of 10 minutes achieved an elution rate of approximately 87.12%, with a manganese loss rate of 2.84%.

[0158] The manganese-based lithium ion sieves prepared in this comparative example have a particle size range of 1-400 μm and are not uniform in size.

[0159] The circulation performance diagram of this manganese-based lithium ion sieve is shown below. Figure 6 As shown, the saturated adsorption capacity of this manganese-based lithium ion sieve is 20.05 mg / g, and the adsorption capacity measured after 10 min of adsorption is 19.31 mg / g, which is about 83.95% of the saturated capacity. After 15 cycles, the adsorption capacity is only 42.65% of the initial capacity, and the total manganese loss rate is 3.73%, indicating low recycling capacity.

[0160] Manganese-based lithium ion sieves that were not circulated and those that were circulated 15 times were used to measure their selectivity for lithium and sodium. Specifically, they were adsorbed in lithium solution containing 20 g / L sodium (Na:Li = 40:1) for 2 min, and the adsorption capacity of each for lithium and sodium was measured. The results are shown in Table 5.

[0161] Table 5 Selectivity before and after cycling

[0162]

[0163] As can be seen from Table 5, the selectivity of the manganese-based lithium ion sieve provided in this comparative example to lithium is significantly reduced after multiple cycles.

[0164] Comparative Example 2

[0165] The difference between this comparative example and Example 2 is that manganese slag A is used instead of the manganese slag used in Example 2, while all other additions and conditions are the same as in Example 2. The molecular formula of the resulting manganese-based lithium ion sieve is H. 1.33 (Zn 0.21 Cu 0.019 Co 0.001 Mn 1.44 O4.

[0166] The metal composition of the aforementioned manganese slag A includes 86.20% Mn, 12.24% Zn, 1.56% Cu, and 0.001% Co.

[0167] That is, the Co content of the above-mentioned manganese slag A is too low compared to the manganese slag used in Example 2.

[0168] In this method, in S4, the elution time is 10 minutes to achieve an elution rate of approximately 92.26%, with a manganese dissolution rate of 0.57%. After 15 cycles, the total manganese dissolution rate is 1.72%.

[0169] Manganese-based lithium ion sieves that were not circulated and those that were circulated 15 times were used to measure their selectivity for lithium and sodium. Specifically, they were adsorbed in lithium solution containing 20 g / L sodium (Na:Li = 40:1) for 2 min, and the adsorption capacity of each for lithium and sodium was measured. The results are shown in Table 6.

[0170] Table 6 Selectivity before and after cycling

[0171]

[0172] As can be seen from Table 6, compared with Example 2, the low proportion of Co doping ions has limited effect on improving the regeneration performance of the ion sieve.

[0173] Comparative Example 3

[0174] The difference between this comparative example and Example 2 is that manganese slag B is used instead of the manganese slag used in Example 2, while all other additions and conditions are the same as in Example 2. The molecular formula of the resulting manganese-based lithium ion sieve is Li. 1.33 (Zn 0.27 Cu 0.004 Co 0.009 Mn 1.45 O4.

[0175] The metal composition of manganese slag B includes 87.05% Mn, 12.23% Zn, 0.22% Cu and 0.50% Co.

[0176] That is, the Cu content in the above-mentioned manganese slag B is too low compared to the manganese slag used in Example 2.

[0177] In this method, the particle size distribution diagram of the lithium-ion sieve precursor is as follows: Figure 7 As shown in Figure S4, an elution time of 10 minutes achieved an elution rate of approximately 90.58%, with a manganese loss rate of 0.46%. After 15 cycles, the total manganese loss rate was 2.84%.

[0178] Manganese-based lithium ion sieves that were not circulated and those that were circulated 15 times were used to measure their selectivity for lithium and sodium. Specifically, they were adsorbed in lithium solution containing 20 g / L sodium (Na:Li = 40:1) for 2 min, and the adsorption capacity of each for lithium and sodium was measured. The results are shown in Table 7.

[0179] Table 7 Selectivity before and after cycling

[0180]

[0181] As can be seen from Table 7, compared with Example 2, a low Cu ratio leads to insufficient lattice stability, and some ion sieves agglomerate (e.g. Figure 7 As shown in the figure, the regeneration performance has not been effectively improved.

[0182] In summary, this application uses manganese carbonate containing a certain proportion of zinc, copper, and cobalt ions as raw material and employs a combination of pre-calcination and calcination to prepare a multi-ion-doped manganese-based lithium-ion sieve with a spinel structure. This ion sieve has a small particle size and uniform particle size distribution, and exhibits high lithium-ion elution rate, low ion loss, high selectivity for lithium in a high-sodium environment, fast ion exchange rate, and excellent recyclability.

[0183] Compared to existing ion-doped manganese-based lithium-ion sieves, this multi-ion-doped manganese-based lithium-ion sieve uses manganese slag containing zinc, copper, and cobalt ions as raw material. This not only saves the manganese source and ion doping steps but also provides a method for transforming and utilizing the manganese slag. Furthermore, the uniform distribution of doping elements in this material avoids impurity phase sintering during the calcination process, resulting in a more intact crystal structure for the prepared ion sieve. Moreover, the incorporation of zinc, copper, and cobalt into the ion sieve lattice in a specific ratio improves the structural stability of the ion sieve, solving the problems of easy dissolution and short service life in traditional manganese-based lithium-ion sieve materials, while significantly increasing the lithium-ion diffusion rate. In addition, the complementary effects of the multiple dopants enhance the ion sieve structure, making the doped ions more stable in the lattice voids, thus solving the problem of easy dopant loss and limited improvement in cycle performance in single-element doped ion sieves.

[0184] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium-ion sieve, characterized in that, The molecular formula of the lithium-ion sieve is Li 1.33 R x Mn 1.67-x O4, wherein 0.05≤x≤0.25, and R includes at least three doping elements; the lithium-ion sieve has a spinel structure; R includes at least Zn, Cu and Co, and the molar ratio of Zn, Cu and Co in R is from 1:0.1:0.03 to 1:0.2:0.

06.

2. The lithium-ion sieve according to claim 1, characterized in that, The lithium-ion sieve further includes at least one of the following features: Feature 1: The average particle size of the lithium-ion sieve is 3-30 μm; Feature 2: The actual saturated adsorption capacity of the lithium ion sieve is 13-22 mg / g.

3. A method for preparing a lithium-ion sieve as described in claim 1 or 2, characterized in that, Includes the following steps: According to the preset proportions of each element in the molecular formula, the manganese source and the lithium source are mixed, and then the mixture is calcined. The manganese source contains Mn and R.

4. The preparation method according to claim 3, characterized in that, The lithium source includes at least one of lithium hydroxide and lithium carbonate.

5. The preparation method according to claim 4, characterized in that, The lithium source is lithium carbonate.

6. The preparation method according to claim 3, characterized in that, The mixing methods include dry mixing or wet mixing.

7. The preparation method according to claim 6, characterized in that, The mixing method is wet mixing.

8. The preparation method according to claim 7, characterized in that, The solvent used in wet mixing includes at least one of water and ethanol.

9. The preparation method according to claim 8, characterized in that, The solvent used in the wet mixing process is ethanol.

10. The preparation method according to claim 8, characterized in that, The total mass of the manganese source and the lithium source is related to the volume of the solvent in a ratio of 30g:100mL to 50g:100mL.

11. The preparation method according to claim 3, characterized in that, Calcination includes at least one of the following characteristics: Feature 1: The roasting temperature is 450-550℃; Feature 2: The roasting time is 6-10 hours; Feature 3: The heating rate is 3-8℃ / min.

12. The preparation method according to claim 11, characterized in that, The roasting temperature is 500℃.

13. The preparation method according to claim 11, characterized in that, The roasting time is 8 hours.

14. The preparation method according to claim 11, characterized in that, The heating rate for roasting is 5℃ / min.

15. The preparation method according to claim 11, characterized in that, Prior to roasting, the mixture is also pre-roasted; Pre-baked includes at least one of the following characteristics: Feature 1: Pre-baking temperature is 180-230℃; Feature 2: Pre-roasting time is 1-3 hours; Feature 3: The heating rate is 8-10℃ / min.

16. The preparation method according to claim 15, characterized in that, The pre-baking temperature is 200℃.

17. The preparation method according to claim 15, characterized in that, The pre-calcination time is 2 hours.

18. The preparation method according to claim 15, characterized in that, The heating rate for pre-calcination is 10℃ / min.

19. The preparation method according to claim 3, characterized in that, It also includes washing the roasted products after roasting.

20. The preparation method according to claim 19, characterized in that, The eluent used for elution is acid.

21. The preparation method according to claim 20, characterized in that, The acid used for elution includes at least one of hydrochloric acid and sulfuric acid.

22. The preparation method according to claim 19, characterized in that, The elution temperature is 25-60℃.

23. The preparation method according to claim 19, characterized in that, The elution method is dynamic acid replenishment elution.

24. The preparation method according to claim 23, characterized in that, Maintain the pH of the eluent at 1.5-2.0 during the elution process.

25. The preparation method according to claim 19, characterized in that, It also includes washing and drying the eluted solids.

26. The preparation method according to claim 25, characterized in that, The drying temperature should not exceed 80℃.

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