A method for recycling waste electrolyte of lithium ion battery

Abstract

The present application provides a method for recovering waste electrolyte of lithium-ion batteries, wherein the waste electrolyte contains lithium hexafluorophosphate, comprising the following steps: S1: adding a saline solution as an extractant to the collected waste electrolyte for extraction, separating a lower organic solution and an upper aqueous solution, and recovering the lower organic solution to obtain an organic solvent; S2: adding a water-soluble carbonate and / or a water-soluble phosphate to the upper aqueous solution in step S1, filtering, and separating to obtain a lithium precipitate. The recovery method can achieve efficient separation and recovery of organic solvents and lithium elements in waste electrolytes, is simple and easy to operate, is economical and environmentally friendly, has strong applicability, and can be prepared and produced on a large scale.

Description

Technical Field

[0001] The present application relates to the technical field of waste resource recycling, and in particular to a method for recycling waste electrolyte of lithium-ion batteries. Background Art

[0002] With the rapid development and large-scale application of lithium-ion batteries, the number of waste lithium-ion batteries is also increasing exponentially, so the reuse and harmless treatment of resources have become the top priority at present. If they cannot be recycled in a timely and effective manner, it will cause waste of resources and environmental pollution. However, large-scale recycling and reuse technologies at home and abroad are in their infancy. Their research mainly focuses on metal elements that are easier to operate and have higher economic value, such as nickel, cobalt, aluminum, copper, etc., and there is less research on other components of the battery. Especially for electrolytes, due to their complex composition and easy hydrolysis, they cause serious environmental pollution, are difficult to recycle, and have high costs. In order to meet environmental protection requirements, they are usually only treated simply during the recycling process, and resource recovery is not achieved.

[0003] The electrolyte recovery processes that are currently being studied more include: supercritical extraction, vacuum distillation, alkali absorption and mechanical methods. Supercritical extraction generally uses supercritical CO2 to extract electrolytes from lithium-ion batteries. This method does not destroy the molecular structure of the electrolyte and is green and environmentally friendly, but the process is complex, the conditions are harsh, the cost is high, and it is not suitable for large-scale recovery of waste electrolytes. The product obtained by vacuum distillation has high purity and a relatively high recovery rate, but its process is relatively complex, energy consumption is high, and the recovery profit is low. Compared with other methods, the alkali absorption process is relatively simple, but more wastewater and waste gas will be generated during the recovery process, causing secondary pollution to the environment. The mechanical method is generally complicated to operate and has a low recovery rate, and is not suitable for large-scale industrial production. Therefore, the development of a simple, effective and low-cost electrolyte recovery method has important research significance and application value. Summary of the invention

[0004] In order to solve the above problems, the present application provides a method for recycling waste electrolyte of lithium-ion batteries.

[0005] An embodiment of the present application provides a method for recycling waste electrolyte of lithium ion batteries, wherein the waste electrolyte contains lithium hexafluorophosphate, comprising the following steps:

[0006] S1: adding a saline solution as an extractant to the collected waste electrolyte to perform extraction, separating a lower organic solution and an upper aqueous solution, and recovering the lower organic solution to obtain an organic solvent;

[0007] S2: Add water-soluble carbonate and / or water-soluble phosphate to the upper aqueous solution in step S1, filter, and separate to obtain lithium precipitate.

[0008] In some embodiments, the volume ratio of the saline solution to the spent electrolyte is 1-10.

[0009] In some embodiments, the salt in the saline solution is at least one of sodium chloride, potassium chloride, sodium phosphate, sodium sulfate or potassium sulfate.

[0010] In some embodiments, the concentration of the saline solution is 10% to 100%.

[0011] In some embodiments, the water-soluble carbonate is sodium carbonate, and the water-soluble phosphate is sodium phosphate.

[0012] In some embodiments, after step S1, the method further includes: adding the upper aqueous solution as an extractant into new waste electrolyte for cyclic extraction.

[0013] Furthermore, the upper aqueous solution obtained after multiple cycles of extraction is heated, and after sufficient reaction, quicklime water or calcium hydroxide aqueous solution is added, filtered, and separated to obtain precipitates of phosphate and fluoride salts.

[0014] Furthermore, the heating temperature is 100-150°C.

[0015] In some embodiments, the step S1 of “recovering the lower organic solution to obtain an organic solvent” includes:

[0016] A desiccant is added to the upper organic liquid to remove water, and after standing for a period of time, the organic solvent is purified by distillation.

[0017] In some embodiments, the extraction rate of lithium in the spent electrolyte is greater than 90%.

[0018] Compared with the prior art, the beneficial effects of this application are:

[0019] The recovery method provided by the present application can achieve efficient separation of the solution and solute in the electrolyte by adding a saline solution to the waste electrolyte, the organic solvent obtained after separation can be purified and reused, and the lithium element in the upper aqueous solution can be efficiently extracted. The method is simple and easy to implement, economical and environmentally friendly, and has strong applicability, and can be prepared and produced on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of a method for recycling waste electrolyte from lithium-ion batteries provided in one embodiment of the present application.

[0021] Figure 2 This is an optical image when the saline solution described in Examples 1-3 was extracted 5 times repeatedly. DETAILED DESCRIPTION

[0022] The present application is further described below in conjunction with examples. These examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods in the following examples that do not specify specific conditions are usually carried out in accordance with conventional conditions in the art or in accordance with the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present application are within the scope of protection claimed in the present application.

[0023] An embodiment of the present application provides a method for recovering waste electrolyte of lithium ion batteries, wherein the waste electrolyte contains lithium hexafluorophosphate, comprising the following steps:

[0024] S1: adding a saline solution as an extractant to the collected waste electrolyte to perform extraction, separating a lower organic solution and an upper aqueous solution, and recovering the lower organic solution to obtain an organic solvent;

[0025] S2: Add water-soluble carbonate and / or water-soluble phosphate to the upper aqueous solution in step S1, filter, and separate to obtain lithium precipitate.

[0026] The lithium-ion battery described in the present application can be a battery of any chemical type, such as waste lithium iron phosphate batteries, waste ternary material batteries (containing lithium, nickel, cobalt, manganese or aluminum), etc. The waste electrolyte includes the electrolyte remaining in the waste lithium-ion battery and the failed electrolyte generated in the production process of the enterprise. The waste electrolyte mainly contains organic solvents and electrolyte lithium salts, wherein the organic solvent is usually carbonate esters, such as dimethyl carbonate, potassium ethyl carbonate or ethylene carbonate, and the electrolyte lithium salt is usually lithium hexafluorophosphate (LiPF6).

[0027] This application utilizes the difference in solubility of organic solvents in electrolytes and electrolyte lithium salts in water, and efficiently separates and recycles its components by adding a saline solution to waste electrolytes. The upper organic solution obtained after separation can be stably stored in the air, while the lithium element in the electrolyte can be selectively extracted into the saline solution. Lithium elements can be efficiently extracted from a large amount of electrolytes by precipitation. The method is simple to operate, economical and environmentally friendly, and can achieve maximum recycling of resources in waste electrolytes, and is suitable for large-scale production and processing by enterprises.

[0028] In this embodiment, the volume ratio of the saline solution to the waste electrolyte is 1-10.

[0029] In this embodiment, the salt in the saline solution is at least one of sodium chloride, potassium chloride, sodium sulfate or potassium sulfate.

[0030] In this embodiment, the concentration of the saline solution is 10% to 100%.

[0031] The study found that when pure water is added to the waste electrolyte, when the volume ratio of pure water to waste electrolyte is 1:1, the waste electrolyte will be completely miscible with pure water. When the volume ratio is higher than 1:1, only a small amount of waste electrolyte precipitates. When a certain amount of salt substances is added to pure water, that is, a saline solution is added to the waste electrolyte, the waste electrolyte and the saline solution are completely separated, and most of the highest value lithium in the waste electrolyte is concentrated in the saline solution. This may be because the addition of salt substances to the aqueous solution can effectively increase the ionic strength in the aqueous phase, increase the polarity, and promote the separation of the aqueous phase and the organic phase. At the same time, the electrolyte lithium salt replaces lithium into the saline solution due to the action of the salt solution.

[0032] It is understandable that when the concentration of the saline solution is high (high saturation), the lithium precipitate obtained by separation and recovery may contain a portion of salt substances precipitated from the saturated saline solution, and pure lithium precipitate may be obtained by simple water dissolution and precipitation separation.

[0033] In this embodiment, the water-soluble carbonate is sodium carbonate, and the water-soluble phosphate is sodium phosphate.

[0034] In this embodiment, after step S1, the method further includes: adding the upper aqueous solution as an extractant into new waste electrolyte for cyclic extraction.

[0035] Furthermore, the upper aqueous solution obtained after multiple cycles of extraction is heated, and after sufficient reaction, quicklime water or calcium hydroxide aqueous solution is added, filtered, and separated to obtain precipitates of phosphate and fluoride salts.

[0036] Furthermore, the heating temperature is 100-150°C.

[0037] In the present application, the upper aqueous solution can be recycled as an extractant to extract the waste electrolyte multiple times. When the concentration of fluorine and phosphorus in the solution reaches a certain level, the upper aqueous solution is heated to above 100°C, and the fluorine and phosphorus in the waste electrolyte can be completely hydrolyzed into HF and H3PO4, so that the fluorine and phosphorus can be separated and recovered by precipitation, thereby achieving efficient separation and recovery of lithium, fluorine and phosphorus in the waste electrolyte.

[0038] In this embodiment, the step S1 of "recovering the lower layer organic solution to obtain an organic solvent" includes:

[0039] A desiccant is added to the lower organic solution to remove water, and after standing for a period of time, the organic solvent is purified by distillation.

[0040] Wherein, the desiccant can be anhydrous sodium sulfate and dry molecular sieve; and the standing time can be 12 hours.

[0041] In this embodiment, the extraction rate of lithium element in the waste electrolyte is greater than 90%.

[0042] In the present application, the same batch of waste electrolyte can be extracted multiple times by a saline solution. In the first extraction, the saline solution absorbs a small amount of electrolyte solution, so that the separation rate of the organic solution is about 90%, and the separated organic solution contains a certain amount of lithium salt. After multiple extractions, the lithium concentration in the separated lower organic solution is less than 5ppm, and the extraction rate of lithium in the entire waste electrolyte can be as high as 99.93%.

[0043] The following specific examples are used to describe in detail the method for recycling waste electrolyte of lithium-ion batteries of the present application.

[0044] It can be understood that the concentration and dosage of the sodium carbonate solution and the calcium hydroxide solution in the examples of the present application are not specifically limited, and the dosage can be changed according to specific experiments.

[0045] Example 1

[0046] This embodiment provides a method for recycling waste electrolyte of lithium ion batteries, and its flow chart is as follows: Figure 1 As shown, the specific steps include:

[0047] S1: Add 100% saturated sodium chloride deionized water solution (i.e., the volume ratio is 1:1) to the collected waste electrolyte in a volume ratio of 1:1, stir and mix evenly, and then let it stand to separate the layers, and separate the lower organic solution and the upper aqueous solution.

[0048] S2: Add a new 100% saturated sodium chloride deionized water solution to the lower organic solution obtained in step S1 at a volume ratio of 1:1, repeat 3 times, add anhydrous sodium sulfate and dry molecular sieves to the final lower organic solution, let it stand for half a day, and then purify it by distillation to obtain pure dimethyl carbonate, ethyl potassium carbonate and ethylene carbonate.

[0049] S3: adding the upper aqueous solution obtained in step S1 to the new waste electrolyte at a volume ratio of 1:1, repeating the extraction and separation 5 times, adding a certain amount of sodium carbonate solution to the upper aqueous solution finally obtained, filtering, and separating to obtain lithium carbonate precipitate and filtrate; then adding a certain amount of calcium hydroxide solution to the filtrate and heating to 140° C., after sufficient reaction, filtering, and separating to obtain a mixture precipitate of calcium phosphate and calcium fluoride.

[0050] Example 2

[0051] This embodiment provides a method for recovering waste electrolyte of lithium ion batteries. The concentration of the saturated sodium chloride deionized water solution is 60%, and the remaining steps are the same as those in Embodiment 1.

[0052] Example 3

[0053] This embodiment provides a method for recovering waste electrolyte of lithium ion batteries. The concentration of the saturated sodium chloride deionized water solution is 30%, and the remaining steps are the same as those in Embodiment 1.

[0054] Results Analysis

[0055] The lithium salt concentration in the waste electrolyte in Example 1 was monitored by an inductively coupled plasma emission spectrometer. The initial lithium salt concentration in the waste electrolyte was about 7000 ppm. As shown in Table 1, it was subjected to cyclic extraction three times. After the first extraction, the lithium salt concentration in the separated lower organic solution dropped to 510 ppm. After the third extraction separation, the lithium salt concentration dropped to 5 ppm. It can be seen that after multiple extractions, the lithium ion concentration in the separated organic solution is lower than 5 ppm, and the extraction rate of lithium ions in the entire waste electrolyte can be as high as 99.93%.

[0056] Table 1 Lithium salt concentration when the same waste electrolyte was extracted 3 times in Example 1

[0057] Extraction times Lithium salt concentration (ppm) 1 510 2 78 3 5

[0058] In Examples 1 to 3, saline solutions of different concentrations were used to extract the waste electrolyte. Figure 2 This is an optical picture of different waste electrolytes extracted five times with the same saline solution. Figure 2 It can be seen from the table that after the same saline solution is reused for 5 times, it can still be clearly separated from the lower organic solution in the waste electrolyte, thus achieving efficient recovery. It can be further seen from Table 2 that after each extraction, the lithium concentration in the saline solution increases exponentially, indicating that the same saline solution can still be used to efficiently extract lithium salts after being reused for 5 times.

[0059] Table 2 Lithium salt concentration after repeated extraction 5 times in the saline solution described in Examples 1-3

[0060]

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A method for recovering waste electrolyte of lithium ion batteries, wherein the waste electrolyte contains lithium hexafluorophosphate, and the waste electrolyte comprises electrolyte remaining in waste lithium ion batteries and spent electrolyte generated in the production process of an enterprise, characterized in that: The following steps are involved: S1: adding a saline solution as an extractant to the collected waste electrolyte to perform extraction, separating a lower organic solution and an upper aqueous solution, and recovering the lower organic solution to obtain an organic solvent; S2: Add water-soluble carbonate and / or water-soluble phosphate to the upper aqueous solution in step S1, filter, and separate to obtain lithium precipitate.

2. The method for recycling waste electrolyte of lithium ion batteries according to claim 1, characterized in that: The volume ratio of the saline solution to the waste electrolyte is 1-10.

3. The method for recycling waste electrolyte of lithium ion batteries according to claim 1, characterized in that: The salt in the saline solution is at least one of sodium chloride, potassium chloride, sodium phosphate, sodium sulfate or potassium sulfate.

4. The method for recycling waste electrolyte of lithium ion batteries according to claim 1, characterized in that: The concentration of the saline solution is 10% to 100%.

5. The method for recycling waste electrolyte of lithium ion batteries as claimed in claim 1, characterized in that: The water-soluble carbonate is sodium carbonate, and the water-soluble phosphate is sodium phosphate.

6. The method for recycling waste electrolyte of lithium ion batteries according to claim 1, characterized in that: After step S1, the method further includes: adding the upper aqueous solution as an extractant into new waste electrolyte for cyclic extraction.

7. The method for recycling waste electrolyte of lithium ion batteries as claimed in claim 6, characterized in that: Add water-soluble carbonate and / or water-soluble phosphate to the upper aqueous solution obtained after multiple cycles of extraction, filter, separate to obtain lithium precipitate and filtrate, then add quicklime water or calcium hydroxide aqueous solution to the filtrate, heat, fully react, filter, separate to obtain phosphate and fluoride salt precipitates.

8. The method for recycling waste electrolyte of lithium ion batteries as claimed in claim 7, characterized in that: The heating temperature is 100-150°C.

9. The method for recycling waste electrolyte of lithium ion batteries according to claim 1, characterized in that: The step S1 of "recovering the lower layer organic solution to obtain an organic solvent" includes: A desiccant is added to the lower organic solution to remove water, and after standing for a period of time, the organic solvent is purified by distillation.

10. The method for recycling waste electrolyte of lithium ion batteries according to claim 1, characterized in that: The extraction rate of lithium element in the waste electrolyte is greater than 90%.

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