Method for underwater crushing and recycling electrolyte of waste lithium-ion batteries

Abstract

The present invention discloses a method for underwater crushing and recovering electrolyte from waste lithium-ion batteries. The method comprises adding a calcium chloride mixed solution and waste lithium-ion batteries to a crusher for underwater crushing. The crushed filtrate is distilled, and the liquid layers after distillation are separated to obtain an electrolyte and an aqueous phase. The aqueous phase is extracted with carbon tetrachloride, and the raffinate is separated through a nanofiltration membrane to obtain a lithium salt solution and a calcium chloride solution. The present invention utilizes the calcium chloride mixed solution to prevent a sharp temperature rise, reducing safety hazards, and allows the electrolyte to be completely dissolved. Furthermore, the different water solubilities of the electrolytes are utilized to separate the water-insoluble and water-soluble electrolytes for separate treatment, thereby reducing the pressure of subsequent distillation.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery recycling, and particularly relates to a method for underwater crushing of waste lithium ion batteries to recover electrolyte. Background Art

[0002] Lithium-ion batteries, with their high energy density, lack of memory effect, and excellent electrical performance, have been widely used in electronics, new energy vehicles, energy storage, and other fields. However, with a typical service life of three to eight years, lithium-ion batteries are gradually entering a period of widespread retirement, creating an urgent need for recycling and disposal.

[0003] Currently, my country's recycling methods for used lithium-ion batteries primarily rely on processes such as disassembly, crushing, sorting, and element extraction to recycle valuable resources such as nickel, cobalt, manganese, and lithium. These processes first require the safe crushing or discharge of used lithium-ion batteries under a live battery charge. Traditional saltwater discharge processes, however, produce gases such as chlorine, hydrogen, and oxygen, which are both environmentally unfriendly and pose safety concerns. Physical discharge, on the other hand, suffers from low discharge efficiency and safety issues during the discharge process. Both chemical and physical discharge methods present various challenges. Therefore, to improve battery processing efficiency, live battery crushing is a crucial requirement for the current large-scale processing of used batteries.

[0004] However, safe crushing under charge is still in the research stage. In the current process, during the crushing process under charge, the battery is subjected to physical processes such as squeezing and shearing, which causes the positive and negative electrodes in the battery to short-circuit. The residual electricity in the battery will be released rapidly, causing heat release, fire, explosion and other phenomena during the crushing process, affecting the safety of the crushing process.

[0005] If the battery is crushed directly, the electrolyte in the battery will leak out, which will not only pollute the environment, but may also cause damage to the skin if it comes into contact with the skin. In the case of incomplete discharge, direct crushing is more likely to cause fire and explosion, which poses a greater safety risk. In the existing technology, although the disclosed liquid nitrogen freezing crushing can reduce the risk factor of the crushing process, the presence of lithium embedded in the negative electrode means that the crushed material still has the risk of combustion and explosion; although the injection of inert gas can isolate the air, it cannot cool down or isolate the heated battery material, and cannot completely achieve safe crushing; although underwater crushing can achieve safe crushing, the electrolyte leaks into the water. The properties of electrolytes in water are different. Some are insoluble in water, while others are soluble in water, making it difficult to effectively separate them. In addition, a large amount of organic wastewater is generated, which pollutes the environment and is difficult to treat.

[0006] Therefore, there is an urgent need for a method that can recover and process the electrolyte while crushing underwater to achieve safe crushing and efficient utilization of resources. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for underwater crushing of waste lithium-ion batteries to recover electrolyte.

[0008] According to one aspect of the present invention, a method for underwater crushing and recovering electrolyte from waste lithium-ion batteries is proposed, comprising the following steps:

[0009] S1: adding a calcium chloride mixed solution and waste lithium-ion batteries into a crusher for underwater crushing, during which the temperature in the crusher is controlled below 40° C.; wherein the calcium chloride mixed solution is a mixed solution of calcium chloride solution and an organic solvent;

[0010] S2: After the crushing in step S1 is completed, the obtained solid-liquid mixture is subjected to solid-liquid separation to obtain a filtrate;

[0011] S3: distilling the filtrate to separate the organic solvent to obtain a distilled liquid, and allowing the distilled liquid to stand for separation to obtain an upper electrolyte phase and a lower aqueous phase;

[0012] S4: extracting the lower aqueous phase with carbon tetrachloride to separate an organic phase and a raffinate;

[0013] S5: The raffinate is subjected to a nanofiltration membrane to extract and separate lithium to obtain a lithium salt solution and a calcium chloride solution.

[0014] In some embodiments of the present invention, in step S1, the concentration of the calcium chloride solution is 0.1-1 mol / L, and the volume ratio of the calcium chloride solution to the organic solvent is (1-1.5):1.

[0015] In some embodiments of the present invention, in step S1, the organic solvent is at least one of methanol, ethanol, or acetone. The organic solvent is a water-soluble organic solvent.

[0016] In some embodiments of the present invention, in step S1, the amount of the waste lithium-ion batteries added is 10-20% of the volume of the calcium chloride mixed solution.

[0017] In some embodiments of the present invention, in step S1, the temperature in the crusher is controlled by the following method: a circulating pump is used to send the calcium chloride mixed solution from the upper part of the crusher into a condenser, and then return it to the crusher from the lower part of the crusher.

[0018] In some embodiments of the present invention, in step S3, the distillation temperature is 50-85°C.

[0019] In some embodiments of the present invention, in step S3, the volume content of the organic solvent in the distilled liquid is less than 5%.

[0020] In some embodiments of the present invention, in step S3, the standing time is 0.5-1 h.

[0021] In some embodiments of the present invention, in step S4, the volume ratio of the carbon tetrachloride to the lower aqueous phase is (0.5-2):1.

[0022] In some embodiments of the present invention, in step S4, the organic phase enters a distillation process for refinement.

[0023] In some embodiments of the present invention, in step S5, the separated calcium chloride solution is used to prepare the calcium chloride mixed solution described in step S1.

[0024] According to a preferred embodiment of the present invention, there are at least the following beneficial effects:

[0025] 1. The present invention utilizes a calcium chloride mixed solution to perform underwater crushing of waste lithium-ion batteries. On the one hand, the calcium chloride solution has a good refrigeration effect and can absorb more heat, thereby ensuring that the temperature in the crusher does not rise sharply, thereby avoiding potential safety hazards. On the other hand, the electrolyte after the waste lithium-ion batteries are crushed is dissolved, and the electrolyte salt lithium hexafluorophosphate reacts with calcium chloride to generate lithium salt, calcium phosphate, and calcium fluoride. Due to the different water solubilities of electrolyte solvents such as carbonates, they can be completely dissolved under the mixed action of organic solvents and water, thereby facilitating the subsequent recovery of the electrolyte.

[0026] 2. After the crushing is completed, solid-liquid separation is carried out to recover the valuable substances and elements therein. The low-boiling-point organic solvent is extracted through distillation, and the water-insoluble electrolyte (such as diethyl carbonate, ethyl methyl carbonate, etc.) will precipitate. The density of the calcium chloride solution is greater than that of the electrolyte, and the filtrate is separated into layers, thereby separating the water-insoluble electrolyte; the water-soluble electrolyte is then extracted into the carbon tetrachloride solution through carbon tetrachloride extraction, and then sent to the distillation process for refining; the remaining raffinate contains a large amount of calcium chloride and lithium chloride, and the calcium and lithium are separated by nanofiltration membrane to obtain lithium salt. The calcium chloride solution can be mixed with the organic solvent and recycled.

[0027] 3. The present invention utilizes the different water solubility characteristics of electrolyte solvents to separate water-insoluble electrolyte and water-soluble electrolyte for separate treatment, thereby reducing the pressure of subsequent unified distillation. The distillation temperature is low, which reduces the hydrolysis of esters and improves the yield of the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0029] Figure 1 This is a process flow chart of Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for underwater crushing and recycling electrolyte of waste lithium-ion batteries, referring to Figure 1 The specific process is:

[0033] Step 1: mixing a 1 mol / L calcium chloride solution with methanol in a volume ratio of 1.5:1 to obtain a calcium chloride mixed solution;

[0034] Step 2: Add the calcium chloride mixed solution into a crusher. The crusher is provided with a holding box, and the holding box is provided with crushing rollers running in opposite directions. The amount of calcium chloride mixed solution added must cover the crushing rollers and must not overflow the holding box.

[0035] Step 3: Start the crusher and the circulating pump, and add the waste lithium-ion batteries into the crusher. The amount of waste lithium-ion batteries added is 20% of the volume of the calcium chloride mixed solution in the holding box. After the waste lithium-ion batteries are crushed by the crushing rollers of the crusher, they enter the bottom of the crusher. The circulating pump sends the calcium chloride mixed solution from the upper part of the crusher to the condenser and returns it from the lower part of the crusher. The temperature in the crusher is always controlled to be below 40° C. During this process, no gas escapes;

[0036] Step 4: After the crushing in step 3 is completed, a solid-liquid mixture is obtained, and the material discharged from the bottom of the crusher is filtered, the obtained solid residue enters the pyrolysis system, and the filtrate enters the distillation process;

[0037] Step 5, distilling the filtrate under stirring at 70° C. until the methanol volume content is less than 5%, thereby separating the methanol;

[0038] Step 6: Stop stirring and let stand for 0.5 h. The filtrate is separated into two layers. After separation, an upper electrolyte layer and a lower aqueous phase are obtained;

[0039] Step 7, extracting the lower aqueous phase with carbon tetrachloride at a volume ratio of 1:1, allowing the mixture to stand and separate to obtain an organic phase and a raffinate, with the organic phase entering a rectification process;

[0040] In step 8, the raffinate obtained in step 7 is subjected to a nanofiltration membrane to extract lithium and separate to obtain a lithium salt solution and a calcium chloride solution. The calcium chloride solution is mixed with the methanol obtained in step 5 to prepare a new calcium chloride mixed solution. The total recovery rate of the electrolyte in this embodiment reaches 91.2%.

[0041] Example 2

[0042] A method for underwater crushing and recovering electrolyte from waste lithium-ion batteries, the specific process is as follows:

[0043] Step 1, mixing 0.5 mol / L calcium chloride solution and ethanol in a volume ratio of 1.3:1 to obtain a calcium chloride mixed solution;

[0044] Step 2: Add the calcium chloride mixed solution into a crusher. The crusher is provided with a holding box, and the holding box is provided with crushing rollers running in opposite directions. The amount of calcium chloride mixed solution added must cover the crushing rollers and must not overflow the holding box.

[0045] Step 3: Start the crusher and the circulating pump, and add the waste lithium-ion batteries into the crusher. The amount of waste lithium-ion batteries added is 15% of the volume of the calcium chloride mixed solution in the holding box. After the waste lithium-ion batteries are crushed by the crushing rollers of the crusher, they enter the bottom of the crusher. The circulating pump sends the calcium chloride mixed solution from the upper part of the crusher to the condenser and returns it from the lower part of the crusher. The temperature in the crusher is always controlled to be below 40° C. During this process, no gas escapes;

[0046] Step 4: After the crushing in step 3 is completed, a solid-liquid mixture is obtained, and the material discharged from the bottom of the crusher is filtered, the obtained solid residue enters the pyrolysis system, and the filtrate enters the distillation process;

[0047] Step 5, distilling the filtrate under stirring at 80° C. until the ethanol volume content is less than 5%, thereby separating the ethanol;

[0048] Step 6: Stop stirring and let stand for 0.8 h. The filtrate is separated into two layers. After separation, an upper electrolyte layer and a lower aqueous phase are obtained;

[0049] Step 7, extracting the lower aqueous phase with carbon tetrachloride at a volume ratio of 1:1, allowing the mixture to stand and separate to obtain an organic phase and a raffinate, with the organic phase entering a rectification process;

[0050] In step 8, the raffinate obtained in step 8 is subjected to a nanofiltration membrane to extract lithium and separate to obtain a lithium salt solution and a calcium chloride solution. The calcium chloride solution is mixed with the organic solvent obtained in step 5 to prepare a new calcium chloride mixed solution. The total recovery rate of the electrolyte in this embodiment reaches 90.4%.

[0051] Example 3

[0052] A method for underwater crushing and recovering electrolyte from waste lithium-ion batteries, the specific process is as follows:

[0053] Step 1, mixing 0.1 mol / L calcium chloride solution and acetone in a volume ratio of 1:1 to obtain a calcium chloride mixed solution;

[0054] Step 2: Add the calcium chloride mixed solution into a crusher. The crusher is provided with a holding box, and the holding box is provided with crushing rollers running in opposite directions. The amount of calcium chloride mixed solution added must cover the crushing rollers and must not overflow the holding box.

[0055] Step 3: Starting a crusher and a circulating pump, and adding waste lithium-ion batteries into the crusher, wherein the amount of waste lithium-ion batteries added is 10% of the volume of the calcium chloride mixed solution in the holding box. After being crushed by the crushing rollers of the crusher, the waste lithium-ion batteries enter the bottom of the crusher. The circulating pump sends the calcium chloride mixed solution from the upper part of the crusher to a condenser and then returns it from the lower part of the crusher. The temperature in the crusher is always controlled to be below 40° C., and no gas escapes during this process.

[0056] Step 4: After the crushing in step 3 is completed, a solid-liquid mixture is obtained, and the material discharged from the bottom of the crusher is filtered, the obtained solid residue enters the pyrolysis system, and the filtrate enters the distillation process;

[0057] Step 5, distilling the filtrate under stirring at 60° C. until the acetone volume content is less than 5%, thereby separating the acetone;

[0058] Step 6: Stop stirring and let it stand for 1 hour. The filtrate is separated into two layers. After separation, an upper electrolyte layer and a lower aqueous phase are obtained;

[0059] Step 7, extracting the lower aqueous phase with carbon tetrachloride at a volume ratio of 1:1, allowing the mixture to stand and separate to obtain an organic phase and a raffinate, with the organic phase entering a rectification process;

[0060] In step 8, the raffinate obtained in step 8 is subjected to a nanofiltration membrane for lithium extraction and separation to obtain a lithium salt solution and a calcium chloride solution. The calcium chloride solution is mixed with the organic solvent obtained in step 5 to prepare a new calcium chloride mixed solution. The total recovery rate of the electrolyte in this embodiment reaches 89.3%.

[0061] Comparative Example 1

[0062] A method for underwater crushing and recovering electrolyte from waste lithium-ion batteries, which differs from Example 1 in that the liquid used for crushing is water. The specific process is as follows:

[0063] Step 1: Add water to the crusher. The crusher is equipped with a holding box, which contains crushing rollers that rotate in opposite directions. The amount of water added must cover the crushing rollers and must not overflow the holding box.

[0064] Step 2: Start the crusher and the circulating pump, and add waste lithium-ion batteries into the crusher. The amount of waste lithium-ion batteries added is 20% of the volume of the water in the holding tank. After being crushed by the crushing rollers of the crusher, the waste lithium-ion batteries enter the bottom of the crusher. The circulating pump sends water from the upper part of the crusher to the condenser and returns it from the lower part of the crusher. The temperature in the crusher is always controlled to be below 40°C. During this process, gas escapes, which is phosphorus pentafluoride.

[0065] Step 3: After the crushing in step 2 is completed, a solid-liquid mixture is obtained, and the material discharged from the bottom of the crusher is filtered, the obtained solid residue enters the pyrolysis system, and the filtrate enters the distillation process;

[0066] Step 4: let the filtrate stand and if there is no stratification, directly send it to the distillation process.

[0067] The crushing liquid used in this comparative example is water, which causes the overflow of phosphorus pentafluoride, which has a pungent and foul odor, during the crushing process. Furthermore, because the water and electrolyte undergo vigorous mixing during the crushing stage, and the carbonate and water have similar densities, the filtrate cannot be separated into separate layers. Therefore, the filtrate cannot be graded and must be uniformly distilled, which increases the distillation pressure. The total recovery rate of the electrolyte in this comparative example is only 70.6%. The main reasons for the electrolyte loss are: (1) the water does not sufficiently dissolve some water-insoluble electrolyte during the crushing process, leaving a small amount of electrolyte remaining in the solid residue; and (2) the filtrate is directly fed into the distillation process, which easily causes hydrolysis of the electrolyte.

[0068] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for underwater crushing and recovering electrolyte from waste lithium-ion batteries, characterized in that: The following steps are involved: S1: adding a calcium chloride mixed solution and waste lithium-ion batteries into a crusher for underwater crushing, during which the temperature in the crusher is controlled below 40° C.; wherein the calcium chloride mixed solution is a mixed solution of calcium chloride solution and an organic solvent; S2: After the crushing in step S1 is completed, the obtained solid-liquid mixture is subjected to solid-liquid separation to obtain a filtrate; S3: distilling the filtrate to separate the organic solvent to obtain a distilled liquid, and allowing the distilled liquid to stand for separation to obtain an upper electrolyte phase and a lower aqueous phase; S4: extracting the lower aqueous phase with carbon tetrachloride to separate an organic phase and a raffinate; S5: The raffinate is subjected to a nanofiltration membrane to extract lithium and separate to obtain a lithium salt solution and a calcium chloride solution; In step S1, the concentration of the calcium chloride solution is 0.1-1 mol / L, and the volume ratio of the calcium chloride solution to the organic solvent is (1-1.5):1; The organic solvent is at least one of methanol, ethanol or acetone.

2. The method according to claim 1, characterized in that In step S1, the amount of the waste lithium-ion batteries added is 10-20% of the volume of the calcium chloride mixed solution.

3. The method according to claim 1, characterized in that In step S1, the temperature in the crusher is controlled by the following method: a circulating pump is used to send the calcium chloride mixed solution from the upper part of the crusher into a condenser, and then the solution is returned to the crusher from the lower part of the crusher.

4. The method according to claim 1, wherein In step S3, the distillation temperature is 50-85°C.

5. The method according to claim 1, wherein In step S3, the volume content of the organic solvent in the distilled liquid is less than 5%.

6. The method according to claim 1, characterized in that In step S4, the volume ratio of the carbon tetrachloride to the lower aqueous phase is (0.5-2):

1.

7. The method according to claim 1, characterized in that In step S4, the organic phase enters the distillation process for refinement.

8. The method according to claim 1, wherein In step S5, the separated calcium chloride solution is used to prepare the calcium chloride mixed solution described in step S1.

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