A defluorination agent for recovering lithium salts and its preparation method and application method

Abstract

The present invention provides a defluorinating agent for recovering lithium salts and a preparation method and application method thereof. Based on the total mass of the defluorinating agent, the defluorinating agent includes the following components: 0-25.3% and not 0 Ca, 0-10.6% and not 0 Li, 34.2-40.9% Al, and 40.5-48.5% O. In the defluorinating agent, Ca forms a CaF2 precipitate with F in the defluorinating lithium solution, and Al is hydrolyzed to form Al(OH)3 colloid to wrap the generated CaF2 precipitate, which also has an adsorption effect, and Al(OH)3 colloid further adsorbs F in the solution, and the effect of defluorination of lithium-containing solution is achieved by the dual effects of CaF2 precipitation and Al(OH)3 colloid. In addition, in order to adjust the ratio of Ca and Al in the defluorinating agent, Li is added to the defluorinating agent for charge balance, and the Li element in the defluorinating agent will not introduce other impurities into the solution, so the defluorination effect is good.

Description

Technical Field

[0001] The invention belongs to the field of hydrometallurgy, and in particular relates to a defluorinating agent for recovering lithium salts and a preparation method and an application method thereof. Background Art

[0002] As the number of retired power batteries increases, achieving efficient and clean recycling is not only a practical guarantee for the safe supply of resources, but also a strategic requirement for the construction of ecological civilization. Waste lithium batteries contain metal elements such as lithium, nickel, cobalt, manganese, copper, and aluminum. The recycling of these metals is of great significance to environmental protection and resource security. The recycling of ternary lithium batteries is technically difficult and has low product purity. The F in the binder and electrolyte enters the ternary black powder after crushing, sorting, and reduction. Therefore, the preparation of battery-grade lithium carbonate requires deep separation of F and Li.

[0003] At present, there are two main technical routes for preparing battery-grade lithium carbonate from ternary black powder. The first is the lithium sulfate route: the ternary black powder is acid-leached to dissolve all the valuable metals, and the fluorine-containing lithium sulfate solution is obtained after separation of Ni, Co, and Mn. After defluorination, the solution is precipitated and refined to obtain battery-grade lithium carbonate. This route has obvious defects such as long process, high processing cost, and low lithium yield, and has poor production economy. The second is the lithium carbonate or lithium hydroxide route: the ternary battery converts Li into soluble lithium hydroxide by hydrogen reduction or converts Li into lithium carbonate phase by carbon thermal reduction. After reduction, the material is water-leached to migrate Li to the aqueous phase, and F enters the aqueous phase in large quantities. The lithium carbonate obtained by further preparation has the problem of high fluorine content. This route has a short process and low processing cost as a whole, so it has good production economy and has good application prospects in the future. However, it is necessary to develop defluorination agents and methods in the lithium carbonate preparation process to improve the purity of lithium carbonate, and finally realize the efficient recovery of ternary black powder to prepare battery-grade lithium carbonate.

[0004] CN117105248A discloses a method for producing battery-grade lithium carbonate using waste NCM ternary battery powder. The invention obtains battery-grade lithium carbonate through reduction roasting, bicarbonation reaction to remove impurities, fluorine and phosphorus, and thermal decomposition. In order to achieve the purpose of removing fluorine and phosphorus, zirconium hydroxide is added to the liquid after the carbonization reaction to remove fluorine and phosphorus. The amount of zirconium hydroxide used is 20-100 times the total mass of fluorine in the liquid after the reaction, the temperature for removing fluorine and phosphorus is 20-95°C, the level of fluorine and phosphorus removal is 1-3, and the time for removing fluorine and phosphorus is 1-4h. The defluorination agent used in this patent is zirconium hydroxide, which has a large amount and is expensive. It also has the defects of high defluorination temperature, many levels, and long time. It is currently difficult to use in production. CN117125728A discloses a device and method for recycling lithium carbonate from waste ternary lithium batteries. The invention obtains lithium carbonate products through reduction roasting process, grinding and water immersion process, cyclic reaction process, impurity removal and filtration process, pyrolysis and lithium extraction process, washing process, and drying process. This invention uses resin to remove calcium, magnesium and fluoride ion impurities. The preparation process of fluorine removal resin is immature, the adsorption capacity decays quickly, and it is difficult to apply in industrial production. The above-mentioned prior art uses zirconium hydroxide or resin to remove fluorine from lithium-containing solutions, but has the disadvantages of large dosage, high price, and fast decay, and is difficult to apply in industrial production.

[0005] Based on this, there is an urgent need to develop a defluorination agent that has good defluorination effect, is simple to prepare, does not introduce other impurities during use, and has low preparation cost, so as to meet the demand for preparing battery-grade lithium carbonate from retired ternary lithium batteries. Summary of the invention

[0006] In view of the deficiencies of the prior art, the object of the present invention is to provide a defluorinating agent for recovering lithium salts and a preparation method and application method thereof. In the defluorinating agent provided by the present invention, Ca can form a CaF2 precipitate with F in the defluorinated lithium solution, and Al can be hydrolyzed to form an Al(OH)3 colloid to wrap the generated CaF2 precipitate, and the Al(OH)3 colloid wrapped on its surface also has an adsorption effect, and the Al(OH)3 colloid further adsorbs F in the solution, and the defluorination effect of the lithium-containing solution is achieved through the dual effects of the CaF2 precipitate and the Al(OH)3 colloid. In addition, in order to adjust the ratio of Ca and Al in the defluorinating agent, Li is added to the defluorinating agent for charge balance, and the Li element in the defluorinating agent will not introduce other impurities into the solution. Therefore, the defluorination effect is good, and the preparation method of the defluorinating agent is simple and the preparation cost is low; the defluorinating agent effectively solves the problem that the impurity fluorine is difficult to remove in the process of recycling retired ternary lithium batteries to prepare battery-grade lithium carbonate, and other impurities will not be introduced during the application process, and the efficiency is high.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a defluorinating agent for recovering lithium salts. Based on the total mass of the defluorinating agent, the defluorinating agent comprises the following components:

[0009] 0-25.3% (not 0) Ca, 0-10.6% (not 0) Li, 34.2-40.9% Al, 40.5-48.5% O.

[0010] In the defluorinating agent provided by the present invention, Ca can form CaF2 precipitation with F in the defluorinating lithium solution, and Al can be hydrolyzed to form Al(OH)3 colloid to wrap the generated CaF2 precipitation, and the Al(OH)3 colloid wrapped on its surface also has an adsorption effect, and the Al(OH)3 colloid further adsorbs F in the solution, and the defluorination effect of the lithium-containing solution is achieved by the dual effects of the CaF2 precipitation and the Al(OH)3 colloid. In addition, in order to achieve the adjustment of the ratio of Ca and Al in the defluorinating agent, Li is added to the defluorinating agent for charge balance, and the Li element in the defluorinating agent will not introduce other impurities into the solution. In summary, the defluorinating agent has a good defluorination effect, and the preparation method of the defluorinating agent is simple, and the preparation cost is low, which effectively solves the problem that the impurity fluorine is difficult to remove in the process of recycling and preparing battery-grade lithium carbonate from retired ternary lithium batteries, and other impurities will not be introduced during the application process, and the efficiency is high.

[0011] In the present invention, 0-25.3% of Ca and not 0 may be, for example, 5%, 10%, 15%, 20% or 25%; 0-10.6% of Li and not 0 may be, for example, 2%, 4%, 6%, 8% or 10%; 34.2-40.9% of Al may be, for example, 35%, 36%, 37%, 38%, 39% or 40%; 40.5-48.5% of O may be, for example, 41%, 43%, 45% or 48%;

[0012] The present invention adopts the above-mentioned specific content of multiple elements to cooperate with each other, which is helpful to achieve the deep removal of fluorine in different fluorine-containing lithium solutions, and achieves the purpose of minimizing the amount of defluorination agent by adjusting the proportions of multiple elements.

[0013] Preferably, based on the total mass of the defluorinating agent, the defluorinating agent comprises the following components:

[0014] 5-15% Ca, 2-7% Li, 35-37% Al, 43-46% O.

[0015] Preferably, the particle size D99 of the defluorinating agent is ≤38 μm, for example, it may be 38 μm, 36 μm, 34 μm, 32 μm, 30 μm, 25 μm, 20 μm or 15 μm.

[0016] It should be noted that D99 is a parameter used to describe the particle size distribution. It indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 99% in a particle system. In simple terms, 99% of the particles have a particle size smaller than this value.

[0017] In the present invention, the defluorinating agent with a suitable particle size is helpful to increase the reaction contact area between the defluorinating agent and the fluorine-containing lithium solution, thereby improving the reaction kinetics rate.

[0018] In a second aspect, the present invention provides a method for preparing a defluorinating agent for recovering lithium salts as described in the first aspect, the preparation method comprising the following steps:

[0019] The calcium source, the lithium source and the aluminum source are mixed to obtain a mixed material.

[0020] The mixed material is melted to obtain a melt, and then the melt is calcined to obtain a calcined material.

[0021] The calcined material is cooled and post-processed to obtain the defluorinating agent for recovering lithium salt.

[0022] The raw materials of the preparation method provided by the invention are easy to obtain and the preparation process is simple.

[0023] Preferably, the calcium content in the calcium source is n1 mol, the lithium content in the lithium source is n2 mol, and the aluminum content in the aluminum source is n3 mol, where n3=2n 1+ n2.

[0024] In the present invention, the calcium content in the calcium source, the lithium content in the lithium source and the aluminum content in the aluminum source satisfy the above relationship, and the dual effects of precipitation defluorination and adsorption defluorination can be achieved. The optimal defluorination effect is achieved by regulating the ratio of the two.

[0025] Preferably, the calcium source includes at least one of calcium oxide, calcium hydroxide and metallic calcium.

[0026] Preferably, the lithium source includes at least one of lithium carbonate, lithium hydroxide and metallic lithium.

[0027] Preferably, the aluminum source includes at least one of aluminum hydroxide, aluminum oxide and metallic aluminum.

[0028] Preferably, the temperature of the melt treatment is 330-790°C, for example, it can be 330°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C.

[0029] In the present invention, the purpose of carrying out the melting treatment at the above temperature is to achieve sufficient reaction and uniform distribution of each element in the molten state.

[0030] Preferably, the constant temperature time of the melt treatment is 20-150 min, for example, 20 min, 50 min, 100 min or 150 min.

[0031] Preferably, the atmosphere of the melting treatment is an inert atmosphere, for example, argon or nitrogen.

[0032] Preferably, the calcination temperature is 330-790°C, for example, 330°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C.

[0033] In the present invention, the purpose of performing the calcination treatment at the above temperature is to promote further sufficient reaction of the melt.

[0034] Preferably, the constant temperature time of the calcination treatment is 10-30 min, for example, 10 min, 20 min or 30 min.

[0035] Preferably, the calcination treatment is carried out in an oxidizing atmosphere, for example, oxygen or air.

[0036] Preferably, during the cooling process, the cooling rate is 50-200°C / min, for example, 50°C / min, 100°C / min, 150°C / min or 200°C / min.

[0037] In the present invention, the effect of cooling the calcined material at a cooling rate of 50-200°C / min is to form a metastable glass phase in the calcined material, thereby increasing the reaction activity of the defluorinating agent in the solution defluorination process.

[0038] Preferably, the temperature of the calcined material after cooling is ≤100°C, for example, it may be 100°C, 80°C, 60°C, 40°C or 20°C.

[0039] Preferably, the post-processing step comprises crushing, grinding and screening performed in sequence.

[0040] In a third aspect, the present invention provides an application method of the defluorination agent for recovering lithium salts as described in the first aspect, the application method comprising the following steps:

[0041] The fluorine-containing lithium solution and the defluorinating agent are mixed to obtain a slurry.

[0042] The slurry is subjected to a defluorination reaction, and then solid-liquid separation is performed to obtain a defluorinated lithium-containing liquid and a defluorinated slag.

[0043] The defluorinated lithium-containing liquid is subjected to heat treatment, and then solid-liquid separation is performed to obtain a mother liquor and a lithium carbonate material. The lithium carbonate material is post-treated to obtain battery-grade lithium carbonate.

[0044] The defluorination agent provided by the present invention effectively solves the problem that the impurity fluorine is difficult to remove during the process of recycling retired ternary lithium batteries to prepare battery-grade lithium carbonate, and other impurities will not be introduced during the application process, and the efficiency is high.

[0045] Preferably, the mass ratio of fluoride ions in the fluorine-containing lithium solution to the defluorinating agent is 1:(5-30), for example, it can be 1:5, 1:10, 1:15, 1:20, 1:25 or 1:30.

[0046] In the present invention, if the mass ratio of fluoride ions to defluoridation agent in the fluoride-containing lithium solution is too small, that is, the amount of defluoridation agent used is too much, the production cost is increased, and the synergistic defluorination effect is weakened; if the mass ratio of fluoride ions to defluoridation agent in the fluoride-containing lithium solution is too large, that is, the amount of defluoridation agent used is too small, it is difficult to achieve deep removal of fluorine in the fluoride-containing lithium solution, and the fluorine content in the lithium salt product increases.

[0047] Preferably, the defluorination reaction is carried out at 10-30°C, for example, 10°C, 20°C or 30°C.

[0048] Preferably, the defluorination reaction time is 20-80 min, for example, it can be 20 min, 30 min, 40 min, 50 min, 60 min, 70 min or 80 min.

[0049] Preferably, the heat treatment temperature is 80-100°C, for example, 80°C, 90°C or 100°C.

[0050] In the present invention, the heat treatment is carried out at 80-100° C., the purpose of which is to thermally decompose the lithium bicarbonate in the solution and fully convert it into lithium carbonate.

[0051] Preferably, the heat treatment time is 40-150 min, for example, 40 min, 50 min, 100 min or 150 min.

[0052] Preferably, the application method comprises the following steps:

[0053] (1) The reduced ternary black powder and a solvent (such as water) are mixed at a solid-liquid ratio of 1g:(3-20)mL (such as 1g:3mL, 1g:5mL, 1g:10mL, 1g:15mL or 1g:20mL) to obtain a slurry, and then the slurry is mixed with a carbon source to perform a carbonization reaction to obtain a carbonized slurry. The carbonized slurry is filtered to obtain a fluorine-containing lithium solution and a filter residue.

[0054] Wherein, the carbon source includes carbon dioxide gas, and the pH value of the carbonized slurry is ≤9 (for example, it can be 9, 8, 7, 6 or 5, etc.).

[0055] (2) Mixing the fluorine-containing lithium solution and a defluorinating agent to obtain a slurry; wherein the mass ratio of fluorine ions in the fluorine-containing lithium solution to the defluorinating agent is 1:(5-30).

[0056] (3) performing a defluorination reaction on the slurry at 10-30° C. for 20-80 min, filtering after the reaction to obtain a defluorinated lithium-containing liquid and defluorinated slag.

[0057] (4) heat-treating the defluorinated lithium-containing liquid at 80-100° C. for 40-150 min, filtering the liquid after heat treatment to obtain a mother liquor and a lithium carbonate material, and drying, crushing and dehydrating the lithium carbonate material to obtain battery-grade lithium carbonate.

[0058] It should be noted that the reduced ternary black powder is obtained by hydrogen reduction or carbon thermal reduction of the ternary black powder obtained after the crushing and sorting of retired ternary batteries or ternary pole pieces.

[0059] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] In the defluorinating agent provided by the present invention, Ca can form CaF2 precipitation with F in the defluorinating lithium solution, and Al can be hydrolyzed to form Al(OH)3 colloid to wrap the generated CaF2 precipitation, and the Al(OH)3 colloid wrapped on its surface also has an adsorption effect, and the Al(OH)3 colloid further adsorbs F in the solution, and the defluorination effect of the lithium-containing solution is achieved through the dual effects of CaF2 precipitation and Al(OH)3 colloid. In addition, in order to adjust the ratio of Ca and Al in the defluorinating agent, Li is added to the defluorinating agent for charge balance, and the Li element in the defluorinating agent will not introduce other impurities into the solution, so the defluorination effect is good. In addition, the preparation method of the defluorinating agent is simple and the preparation cost is low; the defluorinating agent effectively solves the problem that the impurity fluorine is difficult to remove in the process of recycling retired ternary lithium batteries to prepare battery-grade lithium carbonate, and other impurities will not be introduced during the application process, and the efficiency is high. DETAILED DESCRIPTION

[0062] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0063] Example 1

[0064] This embodiment provides a defluorinating agent for recovering lithium salts. Based on the total mass of the defluorinating agent, the defluorinating agent includes the following components:

[0065] 14% Ca, 5% Li, 37% Al, 44% O.

[0066] The particle size D99 of the defluorinating agent is 20 μm.

[0067] This embodiment also provides a method for preparing the above-mentioned defluorination agent for recovering lithium salts, and the preparation method comprises the following steps:

[0068] (1) Calcium oxide, lithium carbonate and aluminum hydroxide are mixed to obtain a mixture.

[0069] The calcium content n1 in the calcium oxide is 3.5 mol, the lithium content n2 in the lithium carbonate is 7.1 mol, and the aluminum content n3 in the aluminum hydroxide is 14.1 mol, n3=2n 1+ n2.

[0070] (2) in a nitrogen atmosphere, melting the mixture at a temperature of 560° C. for 90 min to obtain a melt;

[0071] The melt was calcined in an oxygen atmosphere at a temperature of 700° C. for 20 min to obtain a calcined material.

[0072] (3) Cooling the calcined material at a cooling rate of 100° C. / min to a temperature of 50° C., and then crushing, grinding and screening in sequence to obtain the defluorination agent for recovering lithium salt.

[0073] Example 2

[0074] This embodiment provides a defluorinating agent for recovering lithium salts. Based on the total mass of the defluorinating agent, the defluorinating agent includes the following components:

[0075] 3% Ca, 9% Li, 40% Al, 48% O.

[0076] The particle size D99 of the defluorination agent is 25 μm.

[0077] This embodiment also provides a method for preparing the above-mentioned defluorination agent for recovering lithium salts, and the preparation method comprises the following steps:

[0078] (1) Calcium hydroxide, lithium hydroxide and aluminum oxide are mixed to obtain a mixture.

[0079] The calcium content n1 in the calcium hydroxide is 0.65 mol, the lithium content n2 in the lithium hydroxide is 13.5 mol, and the aluminum content n3 in the aluminum oxide is 14.8 mol, n3=2n 1+ n2.

[0080] (2) melting the mixture in an argon atmosphere at a temperature of 330° C. for 150 min to obtain a melt;

[0081] The melt was calcined in an air atmosphere at a temperature of 560° C. for 30 min to obtain a calcined material.

[0082] (3) Cooling the calcined material at a cooling rate of 50° C. / min to a temperature of 100° C., and then crushing, grinding and screening in sequence to obtain the defluorination agent for recovering lithium salt.

[0083] Example 3

[0084] This embodiment provides a defluorinating agent for recovering lithium salts. Based on the total mass of the defluorinating agent, the defluorinating agent includes the following components:

[0085] 23% Ca, 1% Li, 35% Al, 41% O.

[0086] The particle size D99 of the defluorination agent is 15 μm.

[0087] This embodiment also provides a method for preparing the above-mentioned defluorination agent for recovering lithium salts, and the preparation method comprises the following steps:

[0088] (1) Metallic calcium, metallic lithium and metallic aluminum are mixed to obtain a mixture.

[0089] The calcium content n1 in the calcium oxide is 5.8 mol, the lithium content n2 in the lithium carbonate is 1.5 mol, and the aluminum content n3 in the aluminum hydroxide is 13.1 mol, n3=2n 1+ n2.

[0090] (2) melting the mixture in a nitrogen atmosphere at a temperature of 700° C. for 20 min to obtain a melt;

[0091] The melt was calcined in an oxidizing atmosphere at a temperature of 790° C. for 10 min to obtain a calcined material.

[0092] (3) Cooling the calcined material at a cooling rate of 200° C. / min to a temperature of 50° C., and then crushing, grinding and screening in sequence to obtain the defluorination agent for recovering lithium salt.

[0093] Example 4

[0094] The difference between this embodiment and embodiment 1 is that the particle size D50 of the defluorinating agent is 40 μm by adjusting the parameters of crushing, grinding and screening in step (3).

[0095] The rest of the preparation methods and parameters were the same as those in Example 1.

[0096] Example 5

[0097] The difference between this embodiment and embodiment 1 is that the amount of aluminum hydroxide added in step (1) is adjusted so that n3≠2n 1+ n2.

[0098] The rest of the preparation methods and parameters were the same as those in Example 1.

[0099] Example 6

[0100] The difference between this embodiment and embodiment 1 is that the temperature of the melting treatment in step (2) is 300°C.

[0101] The rest of the preparation methods and parameters were the same as those in Example 1.

[0102] Example 7

[0103] The difference between this embodiment and embodiment 1 is that the temperature of the melting treatment in step (2) is 800°C.

[0104] The rest of the preparation methods and parameters were the same as those in Example 1.

[0105] Example 8

[0106] The difference between this embodiment and embodiment 1 is that the temperature of the calcination treatment in step (2) is 300°C.

[0107] The rest of the preparation methods and parameters were the same as those in Example 1.

[0108] Example 9

[0109] The difference between this embodiment and embodiment 1 is that the temperature of the calcination treatment in step (2) is 800°C.

[0110] The rest of the preparation methods and parameters were the same as those in Example 1.

[0111] Example 10

[0112] The difference between this embodiment and embodiment 1 is that the cooling rate in step (3) is 250°C / min.

[0113] The rest of the preparation methods and parameters were the same as those in Example 1.

[0114] Comparative Example 1

[0115] The difference between this comparative example and Example 1 is that the amount of calcium oxide added in step (1) is adjusted so that the content of Ca in the defluoridating agent is 27%.

[0116] The rest of the preparation methods and parameters were the same as those in Example 1.

[0117] Comparative Example 2

[0118] The difference between this comparative example and Example 1 is that the amount of lithium carbonate added in step (1) is adjusted so that the content of Li in the defluorination agent is 12%.

[0119] The rest of the preparation methods and parameters were the same as those in Example 1.

[0120] Comparative Example 3

[0121] The difference between this comparative example and Example 1 is that the amount of aluminum hydroxide added in step (1) is adjusted so that the content of Al in the defluorination agent is 32%.

[0122] The rest of the preparation methods and parameters were the same as those in Example 1.

[0123] Comparative Example 4

[0124] The difference between this comparative example and Example 1 is that the amount of aluminum hydroxide added in step (1) is adjusted so that the content of Al in the defluorination agent is 42%.

[0125] The rest of the preparation methods and parameters were the same as those in Example 1.

[0126] Application Example 1

[0127] This application example provides an application method of a defluorination agent for recovering lithium salts, and the application method comprises the following steps:

[0128] (I) reducing the ternary black powder obtained by crushing and sorting retired ternary batteries with hydrogen to obtain reduced ternary black powder;

[0129] The reduced ternary black powder and water are mixed at a solid-liquid ratio of 1g:10mL to obtain a slurry, and then carbon dioxide gas is introduced into the slurry for carbonization reaction to obtain a carbonized slurry with a pH value of 7. The carbonized slurry is filtered to obtain a fluorine-containing lithium solution and a filter residue.

[0130] (II) adding the defluorinating agent for recovering lithium salts prepared in Example 1 to the fluorine-containing lithium solution to obtain a slurry; wherein the mass ratio of fluoride ions in the fluorine-containing lithium solution to the defluorinating agent for recovering lithium salts is 1:15;

[0131] (III) subjecting the slurry to a defluorination reaction at 20° C. for 50 min, with stirring during the reaction, and filtering after the reaction to obtain a defluorinated lithium-containing liquid and a defluorinated slag;

[0132] (IV) The defluorinated lithium-containing liquid is subjected to heat treatment at 90° C. for 100 min, and then filtered to obtain a mother liquor and a lithium carbonate material. The lithium carbonate material is dried, crushed and dehydrated to obtain battery-grade lithium carbonate.

[0133] Application Example 2-10

[0134] The difference between Application Example 2-10 and Application Example 1 is that the defluorination agent used for recovering lithium salt in step (II) comes from Examples 2-10.

[0135] The rest of the application methods and parameters are the same as those in Application Example 1.

[0136] Application Example 11

[0137] The difference between this application example and application example 1 is that the mass ratio of fluoride ions in the fluorine-containing lithium solution to the defluorination agent for recovering lithium salts is 1:2.

[0138] The rest of the application methods and parameters are the same as those in Application Example 1.

[0139] Application Example 12

[0140] The difference between this application example and application example 1 is that the mass ratio of fluoride ions in the fluorine-containing lithium solution to the defluorination agent for recovering lithium salts is 1:35.

[0141] The rest of the application methods and parameters are the same as those in Application Example 1.

[0142] Application Comparative Examples 1-4

[0143] The difference between Application Comparative Examples 1-4 and Application Example 1 is that the defluorination agent used for recovering lithium salt in step (II) comes from Comparative Examples 1-4 respectively.

[0144] The rest of the application methods and parameters are the same as those in Application Example 1.

[0145] Application Comparative Example 5

[0146] The difference between this comparative application example and application example 1 is that the defluorination agent used to recover lithium salt is replaced by calcium hydroxide.

[0147] The rest of the application methods and parameters are the same as those in Application Example 1.

[0148] Performance Testing

[0149] The fluorine content of the battery-grade lithium carbonate prepared in the above application examples and application comparison examples was tested using a fluoride ion electrode test method.

[0150] The test results are shown in Table 1.

[0151] Table 1

[0152]

[0153]

[0154] analyze:

[0155] It can be seen from the above table that the preparation method of the defluorinating agent provided by the present invention is simple and has low preparation cost. The defluorinating agent effectively solves the problem that the impurity fluorine is difficult to remove during the recycling of retired ternary lithium batteries to prepare battery-grade lithium carbonate, and other impurities will not be introduced during the application process, and the efficiency is high.

[0156] From the comparison between Application Example 1 and Application Example 4, it can be seen that if the particle size D50 of the defluorinating agent is too large, it is not conducive to the full contact between the defluorinating agent and the fluorine in the solution, and the defluorinating effect is poor.

[0157] From the comparison between Application Example 1 and Application Example 5, we can see that if n3≠2n 1+ n2 is not conducive to the formation of Ca-Al-Li-O compounds, the defluorination process cannot achieve in-situ reaction, and the defluorination effect is poor.

[0158] By comparing Application Example 1 with Application Examples 6-7, it can be seen that if the temperature of the melt treatment is too low, the reaction kinetics will deteriorate, the components will not react fully, and the defluorination effect will be poor; if the temperature of the melt treatment is too high, the components will sinter during the reaction process to form a stable phase, and the defluorination effect will be poor.

[0159] By comparing Application Example 1 with Application Examples 8-9, it can be seen that if the calcination temperature is too low, the reaction kinetics will deteriorate, the components will not react fully, and the defluorination effect will be poor; if the calcination temperature is too high, the components will sinter to form a stable phase during the reaction and some components will volatilize, making it difficult to control the proportion of the elements in the defluorination agent, resulting in a poor defluorination effect.

[0160] By comparing Application Example 1 with Application Example 10, it can be seen that if the cooling rate is too large, it is not conducive to the formation of a metastable glass phase, the defluorination agent has low reactivity in the solution defluorination process, and the defluorination effect is poor.

[0161] By comparing Application Example 1 with Application Examples 11-12, it can be seen that if the mass ratio of fluoride ions in the fluoride-containing lithium solution to the defluoridation agent for recovering lithium salt is too small, the synergistic defluoridation effect will be weakened; if the mass ratio of fluoride ions in the fluoride-containing lithium solution to the defluoridation agent for recovering lithium salt is too large, there will be insufficient calcium in the defluoridation agent to combine with fluorine and insufficient aluminum to form colloidal adsorption to remove fluorine, and it will be difficult to achieve deep removal of fluorine in the fluoride-containing lithium solution, and the fluorine content in the lithium salt product will increase.

[0162] By comparing Application Example 1 with Application Comparative Examples 1-4, it can be seen that if the Ca content in the defluorinating agent is too large, the formed calcium fluoride precipitate is difficult to be wrapped by the aluminum hydroxide colloid, and the calcium fluoride is gradually converted into calcium carbonate and it is difficult to achieve the defluorination effect; if the Li content in the defluorinating agent is too large, the excess lithium is difficult to combine with aluminum calcium to form a metastable glass phase, and the single lithium salt phase has no defluorination effect, resulting in a decrease in the overall defluorination effect; if the Al content in the defluorinating agent is too small, the calcium fluoride precipitate cannot be wrapped; if the Al content in the defluorinating agent is too large, an aluminum oxide phase exists in the defluorinating agent, and this phase has no defluorination effect.

[0163] By comparing Application Example 1 with Application Comparative Example 5, it can be seen that if the defluoridating agent used to recover lithium salts is replaced by calcium hydroxide, only calcium fluoride precipitation has a defluoridation effect. As the carbonate concentration increases during the heat treatment process, calcium fluoride is gradually converted into calcium carbonate, fluorine is released, and deep defluoridation cannot be achieved.

[0164] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A defluorinating agent for recovering lithium salts, characterized in that: Based on the total mass of the defluorinating agent, the defluorinating agent includes the following components: 0-25.3% (not 0) Ca, 0-10.6% (not 0) Li, 34.2-40.9% Al, 40.5-48.5% O.

2. The defluorinating agent for recovering lithium salt according to claim 1, characterized in that: Based on the total mass of the defluorinating agent, the defluorinating agent includes the following components: 5-15% Ca, 2-7% Li, 35-37% Al, 43-46% O; Preferably, the particle size D99 of the defluorination agent is ≤38 μm.

3. A method for preparing a defluorinating agent for recovering lithium salts as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: mixing a calcium source, a lithium source and an aluminum source to obtain a mixture; Melting the mixed material to obtain a melt, and then calcining the melt to obtain a calcined material; The calcined material is cooled and post-processed to obtain the defluorinating agent for recovering lithium salt.

4. The preparation method according to claim 3, characterized in that: The calcium content in the calcium source is n1 mol, the lithium content in the lithium source is n2 mol, and the aluminum content in the aluminum source is n3 mol, where n3=2n 1+ n2; Preferably, the calcium source includes at least one of calcium oxide, calcium hydroxide and metallic calcium; Preferably, the lithium source includes at least one of lithium carbonate, lithium hydroxide and metallic lithium; Preferably, the aluminum source includes at least one of aluminum hydroxide, aluminum oxide and metallic aluminum.

5. The preparation method according to claim 3 or 4, characterized in that: The temperature of the melt treatment is 330-790°C; Preferably, the constant temperature time of the melt treatment is 20-150 min; Preferably, the atmosphere of the melt treatment is an inert atmosphere.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The calcination temperature is 330-790°C; Preferably, the constant temperature time of the calcination treatment is 10-30min; Preferably, the calcination treatment is carried out in an oxidizing atmosphere.

7. The preparation method according to any one of claims 3 to 6, characterized in that: During the cooling process, the cooling rate is 50-200°C / min; Preferably, the temperature of the calcined material after cooling is ≤100°C; Preferably, the post-processing step comprises crushing, grinding and screening performed in sequence.

8. A method for using the defluorination agent for recovering lithium salts as claimed in claim 1 or 2, characterized in that: The application method comprises the following steps: mixing the fluorine-containing lithium solution and the defluorinating agent to obtain a slurry; The slurry is subjected to a defluorination reaction, and then solid-liquid separation is performed to obtain a defluorinated lithium-containing liquid and a defluorinated slag; The defluorinated lithium-containing liquid is subjected to heat treatment, and then solid-liquid separation is performed to obtain a mother liquor and a lithium carbonate material. The lithium carbonate material is post-treated to obtain battery-grade lithium carbonate.

9. The application method according to claim 8, characterized in that: The mass ratio of fluoride ions in the fluorine-containing lithium solution to the defluorination agent is 1:(5-30); Preferably, the defluorination reaction is carried out at 10-30°C; Preferably, the defluorination reaction time is 20-80 min; Preferably, the temperature of the heat treatment is 80-100°C; Preferably, the heat treatment time is 40-150 min.

10. The application method according to claim 8 or 9, characterized in that: The application method comprises the following steps: (1) mixing the reduced ternary black powder and a solvent at a solid-liquid ratio of 1 g:(3-20) mL to obtain a slurry, then mixing the slurry with a carbon source to perform a carbonization reaction to obtain a carbonized slurry, and filtering the carbonized slurry to obtain a fluorine-containing lithium solution and a filter residue; Wherein, the carbon source includes carbon dioxide gas, and the pH value of the carbonized slurry is ≤9; (2) mixing the fluorine-containing lithium solution and a defluorinating agent to obtain a slurry; wherein the mass ratio of fluorine ions in the fluorine-containing lithium solution to the defluorinating agent is 1:(5-30); (3) performing a defluorination reaction on the slurry at 10-30° C. for 20-80 min, filtering after the reaction to obtain a defluorinated lithium-containing liquid and a defluorinated slag; (4) heat-treating the defluorinated lithium-containing liquid at 80-100° C. for 40-150 min, filtering the liquid after heat treatment to obtain a mother liquor and a lithium carbonate material, and drying, crushing and dehydrating the lithium carbonate material to obtain battery-grade lithium carbonate.

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