Molten salt and application thereof, and recovery method of waste lithium battery positive electrode material

Abstract

The invention relates to the field of waste lithium battery recovery, and discloses a molten salt which comprises oxysulfate and a urea compound, in the molten salt, the molar ratio of the oxysulfate in terms of acid radical to the urea compound in terms of ureido is (1-10): 1. The molten salt comprises oxysulfate and a urea compound, the lithium extraction rate of the positive electrode material is high through synergism of the oxysulfate and the urea compound, the purity of the obtained lithium salt product is high, and the consumption of the oxysulfate and the roasting temperature during recovery of the waste lithium battery can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of waste lithium battery recycling, in particular to a molten salt and its application and a waste lithium battery positive electrode material recycling method. BACKGROUND

[0002] Sulfidation roasting is a commonly used method for preferential lithium recovery in current lithium ion battery recycling. By adding sulfuric acid or sulfate mixture for roasting, lithium ions are preferentially reduced in this process and separated from insoluble transition metal ions by water immersion, thereby achieving the purpose of preferential lithium extraction. However, sulfidation roasting still needs to be carried out at medium-high temperature. For example, CN106505270A uses an excess amount of sulfate (2.0-2.5 times the amount of positive electrode material) to reduce lithium and cobalt in the positive electrode sheet at medium-high temperature (550-650℃). CN117965906A uses sodium sulfate to reduce and roast waste positive electrode powder at a higher temperature (800℃). The excess amount of sulfate participates in the reaction, resulting in more polluting gases, and long-term constant temperature at medium-high temperature also increases energy consumption. SUMMARY

[0003] In order to overcome the problems of large amount of sulfate and high roasting temperature in existing waste lithium battery recycling technology, the present application provides a molten salt and its application and a waste lithium battery positive electrode material recycling method. The molten salt has a high lithium extraction rate for positive electrode materials, the obtained lithium salt product has high purity, and the amount of sulfate and the roasting temperature during waste lithium battery recycling can be reduced.

[0004] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a molten salt, which comprises a sulfur-containing oxygen acid salt and a urea compound. In the molten salt, the molar ratio of the sulfur-containing oxygen acid salt calculated as the acid radical to the urea compound calculated as the ureido group is 1-10:1.

[0005] The second aspect of the present application provides an application of the molten salt provided in the first aspect of the present application in waste lithium battery positive electrode material recycling.

[0006] The third aspect of the present application provides a waste lithium battery positive electrode material recycling method, which comprises mixing the waste lithium battery positive electrode material with the molten salt provided in the first aspect of the present application and roasting.

[0007] The present application has the following advantages: The molten salt provided by the present application comprises a sulfur-containing oxygen acid salt and a urea compound, which have a high lithium extraction rate for positive electrode materials in cooperation, the obtained lithium salt product has high purity, and the amount of sulfur-containing oxygen acid salt and the roasting temperature during waste lithium battery recycling can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1XRD patterns of lithium-containing solids obtained for different examples, comparative examples, wherein 1# is an XRD pattern of a lithium-containing solid obtained in Example 13, 2# is an XRD pattern of a lithium-containing solid obtained in Comparative Example 3, 3# is an XRD pattern of a lithium-containing solid obtained in Example 1, and 4# is a PDF card of Li2SO4. DETAILED DESCRIPTION

[0009] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not, in some cases, critical to the invention. Any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges, for example, "1 to 5", "5.1 to 10", "5.1 to 9.9", and "7.1 to 10", and so forth. Also, the terms in the claims have their plain, ordinary meaning.

[0010] The first aspect of the present application provides a molten salt, the molten salt comprising a sulfur oxyacid salt and a urea compound. The molar ratio of the sulfur oxyacid salt, calculated as the acid radical, to the urea compound, calculated as the urea radical, in the molten salt is 1-10:1.

[0011] In the present application, the molten salt is obtained by compounding the sulfur oxyacid salt and the urea compound, and the decomposition under calcination can produce a reducing substance, and the two can synergistically increase the lithium extraction rate of the positive electrode material, and the obtained lithium salt product has high purity, and can reduce the amount of sulfur oxyacid salt and the calcination temperature during the recycling of waste lithium batteries.

[0012] According to a preferred embodiment of the present application, the molar ratio of the sulfur oxyacid salt, calculated as the acid radical, to the urea compound, calculated as the urea radical, in the molten salt is 3-7:1.

[0013] In the present application, when the ratio of the sulfur oxyacid salt to the urea compound is within the above range, the amount of sulfur oxyacid salt and the calcination temperature during the recycling of waste lithium batteries can be further reduced.

[0014] According to a preferred embodiment of the present application, the urea compound is a sulfonyl urea compound.

[0015] In the present application, when the urea compound is a sulfonyl urea compound, the melting point of the molten salt can be further reduced.

[0016] More preferably, the urea compound is at least one selected from chlorsulfuron, metsulfuron-methyl, tribenuron, and pyridyl sulfuron.

[0017] According to a particularly preferred embodiment of the present application, the urea compound is chlorsulfuron and metsulfuron-methyl.

[0018] Further preferably, the molar ratio of chlorsulfuron to metsulfuron-methyl is 0.5-2:1.

[0019] According to a preferred embodiment of the present application, the sulfur-containing oxygen acid salt is at least one selected from the group consisting of sulfate, bisulfate, pyrosulfate, persulfate and thiosulfate.

[0020] More preferably, the sulfur-containing oxygen acid salt is ammonium sulfate and / or sodium bisulfate, and further preferably is ammonium sulfate and sodium bisulfate.

[0021] When the sulfur-containing oxygen acid salt is ammonium sulfate and sodium bisulfate, the molten salt is more stable.

[0022] In the present application, the sulfur-containing oxygen acid salt is ammonium sulfate, which has a better synergistic effect with urea compounds, especially sulfonylurea compounds, and can further reduce the melting point of the molten salt and thus reduce the reaction temperature.

[0023] According to a preferred embodiment of the present application, the melting point of the molten salt is 180-400℃.

[0024] In the present application, when the melting point of the molten salt is within the above range, the calcination temperature during the recovery of the positive electrode material can be further reduced.

[0025] More preferably, the melting point of the molten salt is 200-350℃.

[0026] According to the present application, preferably, the average particle size of the molten salt is not more than 150μm.

[0027] In the present application, when the average particle size of the molten salt is within the above range, the components of the molten salt can be further mixed more fully.

[0028] More preferably, the average particle size of the molten salt is not more than 100μm.

[0029] In the present application, the molten salt can be obtained by mechanically mixing and grinding the sulfur-containing oxygen acid salt and the urea compound. The present application does not particularly limit the specific method of mechanical mixing, which can be routinely selected by those skilled in the art.

[0030] According to a specific embodiment of the present application, the preparation method of the molten salt comprises mixing the sulfur-containing oxygen acid salt and the urea compound, then placing them in a planetary ball mill at a revolution speed of 150-450rpm and a rotation speed of 300-900rpm for ball milling for 120-300min, and then sieving through a 100-150 mesh sieve to obtain the molten salt from the undersize.

[0031] The second aspect of the present application provides an application of the molten salt provided in the first aspect of the present application in the recovery of positive electrode materials from waste lithium batteries.

[0032] The third aspect of the present application provides a method for recycling waste lithium battery cathode material, which comprises mixing the waste lithium battery cathode material with the molten salt provided in the first aspect of the present application and calcining.

[0033] The mixing method of the waste lithium battery cathode material and the molten salt is not particularly limited in the present application, and can be routinely selected by those skilled in the art.

[0034] According to a specific embodiment of the present application, the mixing method of the waste lithium battery cathode material and the molten salt comprises placing in a planetary ball mill and ball milling at a revolution speed of 150-450 rpm and a rotation speed of 300-900 rpm for 120-300 min.

[0035] According to a preferred embodiment of the present application, the waste lithium battery cathode material is a waste ternary lithium ion battery cathode material.

[0036] According to a preferred embodiment of the present application, the mass ratio of the waste lithium battery cathode material to the molten salt is 3-10:1.

[0037] In the present application, when the mass ratio of the waste lithium battery cathode material to the molten salt is within the above range, the extraction rate of lithium from the cathode material can be further improved, and the calcination temperature can be reduced.

[0038] More preferably, the mass ratio of the waste lithium battery cathode material to the molten salt is 1-10:1.

[0039] According to a preferred embodiment of the present application, the calcination conditions comprise a calcination temperature of 400-550℃ and a calcination time of 1-7 h. The calcination time refers to the time after reaching the calcination temperature.

[0040] In the present application, when the calcination temperature and time are within the above range, the lithium recovery rate can be further improved.

[0041] More preferably, the calcination conditions comprise a calcination temperature of 400-500℃ and a calcination time of 1-5 h.

[0042] According to a preferred embodiment of the present application, the temperature is raised to the calcination temperature at a rate of 5-10℃ / min during calcination.

[0043] The present application will be described in detail below through examples.

[0044] In the following examples, the melting point of the molten salt is determined by differential scanning calorimetry; The average particle size of the molten salt and the cathode material is determined by a laser particle size analyzer; The phase composition of the recovered solid is determined by XRD; The lithium content in the recovered solid was determined by inductively coupled plasma optical emission spectrometry (ICP-OES); The waste positive electrode material was dissolved in acid, and the insoluble substance was filtered. The lithium content of the waste positive electrode material was determined by ICP-OES.

[0045] Unless otherwise specified, all reagents and raw materials are commercially available.

[0046] Examples and comparative examples The sulfur oxoacid salt and the urea compound were mixed, and then ball-milled in a planetary ball mill at a revolution speed of 450 rpm and a rotation speed of 900 rpm for 150 min. After sieving, the undersize was obtained, and the molten salt was obtained. The average particle size of the molten salt was 100 μm.

[0047] The waste positive electrode material was crushed and sieved, and the average particle size of the crushed waste positive electrode material was 100 μm. The molten salt and 20 g of the sieved positive electrode material were placed in a planetary ball mill, and ball-milled at a revolution speed of 450 rpm and a rotation speed of 900 rpm for 120 min.

[0048] The ball-milled positive electrode material and the molten salt were placed in a corundum crucible, covered, and placed in a tube furnace. Nitrogen was introduced for 5 min. After heating to the calcination temperature at a rate of 5 ℃ / min, the temperature was kept constant for calcination. After the calcination was completed, the product was naturally cooled to room temperature.

[0049] The composition and melting point of the molten salt, the type and theoretical lithium content of the positive electrode material, the mass ratio of the molten salt to the sieved positive electrode material, and the calcination temperature and constant temperature time are shown in Table 1.

[0050] Table 1

[0051] Table 1 (continued)

[0052] The cooled calcination product was centrifuged at 900 r / min, washed with water, and filtered. The process was repeated twice, and the filtrate was collected. The filtrate was evaporated and crystallized at 120 ℃ to obtain a solid. The mass and lithium content of the solid were determined, and the lithium recovery rate was calculated. The mass, composition, lithium content, and lithium recovery rate of the recovered solid are shown in Table 2.

[0053] Table 2

[0054] As can be seen from the results in Table 1 and Table 2, the molten salt provided by the present application has a lower melting point, and when used for recovering waste lithium battery positive electrode material, a lithium salt with higher purity is obtained, and the lithium recovery rate is higher.

[0055] The lithium-containing solids obtained in the above examples and comparative examples were characterized by XRD, as shown in Figure 1, wherein 1# is the XRD spectrum of the lithium-containing solid obtained in Example 13, 2# is the XRD spectrum of the lithium-containing solid obtained in Comparative Example 3, 3# is the XRD spectrum of the lithium-containing solid obtained in Example 1, and 4# is the PDF card of Li2SO4. Figure 1

[0056] It can be seen that the phase composition of the lithium-containing solid obtained in Example 1 and Comparative Example 3 is mainly Li2SO4, while the phase composition of the lithium-containing solid obtained in Example 13 is Li2CO3 and a small amount of LiF.

[0057] The above describes preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.​

Claims

1. A molten salt, characterized in that, The molten salt comprises a sulfur-containing oxyacid salt and a urea compound; The molten salt comprises a sulfur-containing oxyacid salt and a urea compound; 2. The molten salt of claim 1, wherein, The molten salt comprises a sulfur-containing oxyacid salt and a urea compound; 3. The molten salt according to claim 1 or 2, characterized in that, The urea compound is a sulfonyl urea compound.

4. The molten salt according to any one of claims 1 to 3, characterized in that, The urea compound is at least one selected from chlorimuron-ethyl, metsulfuron-methyl, tribenuron and pyridate.

5. The molten salt according to any one of claims 1 to 4, wherein, The sulfur-containing oxyacid salt is at least one selected from sulfate, bisulfate, pyrosulfate, persulfate and thiosulfate; Preferably, the sulfur-containing oxyacid salt is ammonium sulfate.

6. The molten salt according to any one of claims 1 to 5, wherein, The melting point of the molten salt is 180-400℃. Preferably, the average particle size of the molten salt is not more than 150μm.

7. Use of the molten salt of any one of claims 1-6 in recycling of waste lithium battery cathode material.

8. A method for recycling a positive electrode material of a waste lithium battery, characterized by, The method comprises mixing the waste lithium battery cathode material with the molten salt of any one of claims 1-6 and calcining. Preferably, the waste lithium battery cathode material is a waste ternary lithium ion cathode material.

9. The method of claim 8, wherein, The mass ratio of the waste lithium battery cathode material to the molten salt is 3-10:

1.

10. The method according to claim 8 or 9, characterized in that, The calcination conditions comprise a calcination temperature of 400-550℃ and a calcination time of 1-7h. Preferably, the temperature is raised to the calcination temperature at a rate of 5-10℃ / min.

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