Method for recycling all components of waste lithium ion battery electrolyte and application

Abstract

The application discloses a kind of whole component recovery method and application of waste lithium ion battery electrolyte, belong to lithium ion battery resource utilization technical field.The method includes disassembling waste battery in light mineral oil environment, realizes safe and efficient electrolyte collection;Subsequently, weak base solution is added to electrolyte for reaction, selectively precipitates and recovers high-purity lithium salt;Finally, organic solvent components are separated and purified by two-step vacuum distillation, to obtain dimethyl carbonate, methyl ethyl carbonate and ethylene carbonate.The application does not need inert gas protection, process flow is simple, cost is low, safety is high, effectively solves the problems, such as volatile, flammable, easy to pollute and resource waste, etc.in traditional recovery process, valuable components in electrolyte are efficiently recovered and high-value utilization, can be used for preparation of regenerated electrolyte, with good economic benefit and environmental benefit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of waste lithium ion battery recycling, in particular to a method for recycling all components of electrolyte of waste lithium ion battery and application thereof. BACKGROUND

[0002] With the wide application of new energy vehicles, consumer electronics (such as mobile phones and notebook computers) and energy storage systems, the global production of lithium ion batteries continues to rise, and the number of waste batteries increases rapidly. The recycling of waste batteries has become increasingly important. As a key component of lithium ion batteries, electrolyte mainly includes organic solvents (such as ethylene carbonate, dimethyl carbonate, etc.) and lithium salts (such as LiPF6). Among them, LiPF6 is easy to hydrolyze to generate toxic HF, and organic solvents are volatile and flammable. If discarded directly, the electrolyte may pollute the soil and groundwater, and the volatilization of its organic matter may also cause air pollution. Lithium and phosphorus in LiPF6 are important resources, and their recycling and utilization are of great significance to alleviate the supply pressure of raw materials. Therefore, efficient and safe recycling and resource utilization of electrolyte have become a key challenge in the field of lithium battery recycling.

[0003] Currently, the recycling of waste lithium ion batteries in the industry focuses on the positive and negative electrode materials, while the treatment of electrolyte still has obvious shortcomings. In order to avoid the risk of combustion and explosion during disassembly, the operation of the existing process usually requires a large amount of nitrogen to be introduced to ensure an inert gas environment, which not only makes the equipment complex and costly, but also difficult to scale up. More notably, electrolyte is not effectively separated and extracted for individual recycling in most recycling processes, and often enters the high-temperature roasting link together with the battery components, resulting in decomposition and volatilization of organic solvents, conversion of lithium salts into low-value products, and causing resource waste and secondary pollution.

[0004] Therefore, it is urgent to develop a process for safely and efficiently recycling all components (lithium salt and organic solvent) of electrolyte, which is of great significance to improve the economy and environmental protection of lithium battery recycling. SUMMARY

[0005] In view of the technical problems of waste lithium battery recycling process, such as easy fire during live disassembly, electrolyte not easy to collect, low purity of recycled lithium salt, and difficulty in purifying electrolyte components, the present application provides a method for recycling all components of electrolyte of waste lithium ion battery and application thereof. By disassembling the battery in light mineral oil, oxygen can be effectively isolated, and electrolyte volatilization and combustion can be prevented, so that safe and low-cost electrolyte enrichment and collection can be achieved without nitrogen protection. Then, through step-by-step precipitation and precision distillation technology, high-purity lithium salt and organic solvent components are recovered respectively, realizing efficient and high-quality recycling of waste lithium ion battery electrolyte, and providing a novel and feasible technical path for the full resource recycling of electrolyte.

[0006] The technical scheme of the present application is:

[0007] A full-component recovery method of waste lithium ion battery electrolyte, comprising the following steps:

[0008] S1. The waste lithium battery is placed in light mineral oil for disassembly, obtaining a mixed liquid containing electrolyte and light mineral oil, and the solid parts are fished out and drained;

[0009] S2. The mixed liquid obtained in step S1 is subjected to static stratification or / and extraction separation, and the upper light mineral oil and the lower electrolyte are recovered;

[0010] S3. A weak base solution is added to the electrolyte obtained in step S2 for reaction to generate lithium salt precipitate, which is filtered, washed and dried to obtain a high-purity lithium salt product;

[0011] S4. The filtrate obtained in step S3 is subjected to extraction separation to separate the salt solution and the organic phase;

[0012] S5. The organic phase obtained in step S4 is subjected to two-step vacuum distillation, the first stage of vacuum distillation recovers dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) mixed solvent, and the second stage of vacuum distillation recovers ethylene carbonate (EC).

[0013] Further, in step S1, without nitrogen protection, the battery shell is first removed in light mineral oil, then the positive plate, negative plate and separator are peeled off, and then the solid parts are fished out and fully drained, the solid parts including the positive plate, negative plate, shell and separator.

[0014] Further, in step S1, the light mineral oil is preferably industrial-grade white oil or / and liquid paraffin oil, with a flash point higher than 160℃.

[0015] Further, in step S3, the weak base solution is a carbonate solution or a phosphate solution, with a concentration of 5.0-20.0g / L, a reaction temperature of 25-100℃, and a reaction time of 30-120min.

[0016] Further, the carbonate is ammonium carbonate or sodium carbonate, and the phosphate is ammonium phosphate, diammonium hydrogen phosphate, disodium hydrogen phosphate or sodium phosphate.

[0017] Further, in step S3, the lithium salt product is lithium fluoride or / and lithium phosphate, with a purity not less than 98%.

[0018] Further, in step S5, the first stage of the reduced pressure distillation is performed under the conditions of a distillation temperature of 90-130 DEG C, a distillation time of 90-150 min, and a pressure of -0.10 to -0.08 MPa; and the second stage of the reduced pressure distillation is performed under the conditions of a distillation temperature of 285-300 DEG C, a distillation time of 90-150 min, and a pressure of -0.1 to -0.08 MPa.

[0019] Further, in step S5, the recovered ethylene carbonate has a purity of not less than 99%.

[0020] Further, in step S5, the recovered dimethyl carbonate and the mixed solvent of methyl ethyl carbonate have a volume ratio of dimethyl carbonate to methyl ethyl carbonate of 1:1.5-2.5.

[0021] The ethylene carbonate, the mixed solvent of dimethyl carbonate and methyl ethyl carbonate, and the lithium salt product obtained by the above method can be used to prepare a lithium ion battery electrolyte.

[0022] The present application has the following beneficial effects:

[0023] (1) The present application can significantly reduce the safety risks such as fire and explosion by disassembling the waste lithium battery in a light mineral oil environment without relying on nitrogen protection, while realizing safe and efficient collection of electrolyte, and effectively avoiding resource waste and environmental pollution caused by electrolyte entering the fire recovery process with battery materials.

[0024] (2) The present application can realize selective precipitation and efficient separation of lithium salt by accurately adding different alkali solutions to lithium electrolyte, significantly improve the recovery rate and purity of lithium resources, and support diversified recovery of various high-value lithium salt products (such as lithium fluoride and lithium phosphate), and enhance the economy of resource recycling.

[0025] (3) The present application uses reduced pressure distillation technology to separate and purify organic solvent components, and can recover high-purity dimethyl carbonate, methyl ethyl carbonate and ethylene carbonate (purity ≥ 99%), which is green and efficient, low in cost, and the product can be directly used for electrolyte regeneration, promoting the sustainable development of waste lithium battery resource recycling industry.

[0026] In summary, the present application can realize complete separation and recovery of waste lithium battery electrolyte, which is high in processing efficiency, low in cost, and high in product quality, and is helpful to promote the green development of waste lithium battery resource recycling industry. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a flowchart of the present application;

[0028] Figure 2 is the XRD result of Example 1;

[0029] Figure 3 XRD results of Example 2;

[0030] Figure 4 XRD results of Example 3. DETAILED DESCRIPTION

[0031] The application will be further described in conjunction with the accompanying drawings and specific examples, but the application is not limited thereto.

[0032] In the application, unless specified, the raw materials and equipment used are commercially available or commonly used in the art. The methods in the examples are conventional methods in the art, unless specified otherwise.

[0033] As shown in Figure 1 The application provides a flowchart of a recycling method for waste lithium-ion battery electrolyte based on a light mineral oil system. The recycling method specifically includes:

[0034] The waste lithium battery electrolyte is placed in a tank containing light mineral oil. After the battery is finely disassembled, solid-liquid separation is performed, an alkali solution is added to the liquid part, efficient precipitation recovery of lithium salt is achieved, and then the filtrate is extracted. The separated organic phase is transferred to a distillation flask, and vacuum distillation is performed under a nitrogen atmosphere. The vacuum circulation pump is connected to the condenser tube, and high-purity different organic components are collected by vacuum distillation.

[0035] Example 1

[0036] (1) The battery shell is disassembled in white oil, and then the positive plate, negative plate, shell, and separator are disassembled in turn. The recovery rates of the four are 98.90%, 99.25%, 98.77%, and 99.24%, respectively. The liquid containing electrolyte and white oil is obtained by draining the liquid adhering to the solid surface.

[0037] (2) An ammonium phosphate aqueous solution with a concentration of 5.0 g / L is added to the mixed liquid, stirred at 30°C for 30 min, and then the reaction liquid is filtered. The filter residue is washed with water and placed in an 80°C oven for 4 h to obtain high-purity lithium phosphate (its XRD pattern is shown in Figure 2

[0038] ​(3) The organic phase was subjected to a reduced pressure distillation operation, the temperature was set to 130 °C, the distillation time was 90 min, the pressure was -0.09 MPa, the distillation components were collected, and it was found by gas chromatography detection that DMC:EMC = 1:2, the recovery rate was as high as 95.0%, and the purity was 99.75%. Then the temperature was raised to 285 °C, the distillation time was 90 min, the pressure was -0.09 MPa, and a high-purity EC solution was obtained, with a recovery rate of 91.0% and a purity of 99.45%.

[0039] Example 2

[0040] (1) The battery shell was disassembled in paraffin oil, and then the positive plate, negative plate, shell and separator were sequentially disassembled, with recovery rates of 99.34%, 99.65%, 98.50% and 99.12% respectively. The liquid containing electrolyte and paraffin oil was obtained by draining the liquid adhering to the solid surface;

[0041] (2) An ammonium carbonate aqueous solution with a concentration of 10.0 g / L was added to the mixed liquid, stirred at 80 °C for 60 min, and then the reaction liquid was filtered. The filter residue was washed with water and placed in an 80 °C oven for 4 h to obtain high-purity lithium fluoride (its XRD pattern is shown in Figure 3 ), with a recovery rate of 92.75% and a purity of 99.40%. The filtrate was extracted to separate the aqueous phase and the organic phase.

[0042] (3) The organic phase was subjected to a reduced pressure distillation operation, the temperature was set to 130 °C, the distillation time was 90 min, the pressure was -0.09 MPa, the distillation components were collected, and it was found by gas chromatography detection that DMC:EMC = 1:2, the recovery rate was as high as 95.0%, and the purity was 99.75%. Then the temperature was raised to 285 °C, the distillation time was 90 min, the pressure was -0.09 MPa, and a high-purity EC solution was obtained, with a recovery rate of 91.0% and a purity of 99.45%.

[0043] Example 3

[0044] (1) The same as Example 1.

[0045] (2) An ammonium carbonate aqueous solution with a concentration of 10.0 g / L was added to the mixed liquid, stirred at 80 °C for 60 min, and then the reaction liquid was filtered. The filter residue was washed with water and placed in an 80 °C oven for 4 h to obtain high-purity lithium fluoride (its XRD pattern is shown in Figure 4 ), with a recovery rate of 92.75% and a purity of 99.40%. The filtrate was extracted to separate the aqueous phase and the organic phase.

[0046] (3) The organic phase was subjected to a reduced pressure distillation operation, with the temperature set to 130°C, the distillation time being 90 min, and the pressure being -0.09 MPa, the distillate being collected, and gas chromatography detection finding DMC:EMC = 1.05:1.9, the recovery being as high as 95.0%, and the purity being 99.50%. The temperature was then raised to 280°C, the distillation time being 120 min, and the pressure being -0.1 MPa, to obtain a high-purity EC solution, the recovery being 89.0%, and the purity being 99.20%.

[0047] Example 4

[0048] (1) Same as Example 1.

[0049] (2) A 20.0 g / L aqueous solution of diammonium hydrogen phosphate was added to the mixture, which was stirred at 30°C for 40 min, and then the reaction liquid was filtered, the filter residue was washed with water, and placed in an 80°C oven for 4 h to obtain high-purity lithium phosphate, the recovery being 91.20%, and the purity being 97.50%. The filtrate was extracted to separate the water phase and the organic phase.

[0050] (3) The organic phase was subjected to a reduced pressure distillation operation, with the temperature set to 130°C, the distillation time being 90 min, and the pressure being -0.09 MPa, the distillate being collected, and gas chromatography detection finding DMC:EMC = 1.05:1.9, the recovery being as high as 95.0%, and the purity being 99.50%. The temperature was then raised to 280°C, the distillation time being 120 min, and the pressure being -0.1 MPa, to obtain a high-purity EC solution, the recovery being 89.0%, and the purity being 99.20%.

[0051] Example 5

[0052] (1) Same as Example 1.

[0053] (2) A 12.0 g / L aqueous solution of sodium hydrogen phosphate was added to the mixture, which was stirred at 30°C for 50 min, and then the reaction liquid was filtered, the filter residue was washed with water, and placed in an 80°C oven for 4 h to obtain high-purity lithium phosphate, the recovery being 90.0%, and the purity being 98.30%. The filtrate was extracted to separate the water phase and the organic phase.

[0054] (3) The organic phase was subjected to a reduced pressure distillation operation, with a temperature setting of 125°C, a distillation time of 80 min, and a pressure of -0.1 MPa. The distilled components were collected, and gas chromatography detection found that DMC:EMC = 1.10:2.0, with a recovery rate of up to 94.0% and a purity of 99.0%. The temperature was then increased to 280°C, the distillation time was 120 min, and the pressure was -0.1 MPa, obtaining a high-purity EC solution, with a recovery rate of 88.40% and a purity of 99.0%.

[0055] Comparative Example 1

[0056] The waste lithium-ion battery was disassembled in a glove box filled with high-purity nitrogen (purity ≥ 99.999%) and nitrogen was continuously introduced to maintain an inert atmosphere. After disassembly, the positive electrode sheet, negative electrode sheet, shell and separator were separated, the attached liquid was drained, and the electrolyte and residual solvent mixture was collected. 1.0 g / L of sodium hydroxide aqueous solution was added to the mixture, and reacted at 60°C for 60 min. The precipitate was filtered and washed with water, and then dried at 80°C to obtain a lithium salt product. The main components were lithium fluoride and lithium oxide mixture, the lithium recovery rate was 78.35%, and the purity was 89.50%. The filtrate was subjected to atmospheric distillation, the temperature was set to 285°C, and the fraction was collected. Gas chromatography analysis showed that the fraction was a mixture of dimethyl carbonate, methyl ethyl carbonate and ethylene carbonate, and component separation could not be achieved. The total solvent recovery rate was 82.57%, the purity was only 91.26%, and it contained water and degradation products.

[0057] Comparative Example 2

[0058] The waste lithium-ion battery was directly disassembled in air, and the obtained electrolyte and battery components were collected and sent into a rotary kiln for high-temperature calcination. The temperature was set to 600°C, and the calcination time was 2 h. After calcination, the residue was collected, and a lithium-containing solution was obtained by water immersion and filtration. Lithium carbonate was precipitated by adding sodium carbonate solution, the lithium recovery rate was 65.85%, and the purity was 92.20%. The organic solvent components were completely decomposed and burned during the calcination process, and were not recovered. The waste gas treatment system detected HF and VOCs emissions, and additional purification devices needed to be added. The overall process had high energy consumption and significant environmental pollution risk.

[0059] Comparative Example 3

[0060] The battery was disassembled in white oil and the mixed solution was collected. After standing and separating the lower electrolyte, excess concentrated sodium hydroxide solution (5.0 g / L) was directly added and reacted at 90°C for 120 min, producing a large amount of amorphous precipitate, which was difficult to filter. The obtained lithium salt product had a complex composition, with the main components being lithium hydroxide and lithium phosphate mixture. The lithium recovery rate was 80.10%, and the purity was only 86.40%. The filtrate was subjected to single-stage vacuum distillation, with the temperature set at 150°C, the pressure at -0.09 MPa, and the time at 120 min. The obtained fraction was a mixed solvent of carbonates, and DMC, EMC and EC could not be effectively separated. The overall recovery rate was 88.25%, and the purity was 93.50%. The content of EC was significantly reduced due to partial decomposition.

Claims

1. A method for recovering all components of an electrolyte of a waste lithium ion battery, characterized by, The method comprises the following steps: S1. Disassembling the waste lithium battery in light mineral oil to obtain a mixed solution containing electrolyte and light mineral oil, and solid components are fished out and drained; S2. Static stratification or / and extraction separation is performed on the mixed solution obtained in step S1 to recover the upper light mineral oil and the lower electrolyte; S3. Adding a weak base solution to the electrolyte obtained in step S2 to generate lithium salt precipitate, and then filtering, washing and drying to obtain a high-purity lithium salt product; S4. Extractive separation is performed on the filtrate obtained in step S3 to separate a salt solution and an organic phase; S5. Two-step vacuum distillation is performed on the organic phase obtained in step S4, the first stage being vacuum distillation to recover dimethyl carbonate and methyl ethyl carbonate mixed solvent, and the second stage being vacuum distillation to recover ethylene carbonate.

2. The method according to claim 1, wherein the method is characterized by, In step S1, the solid components include positive electrode sheets, negative electrode sheets, shells and separators. 3.The method according to claim 1, wherein, In step S1, the light mineral oil is industrial-grade white oil or / and liquid paraffin oil with a flash point higher than 160℃. 4.The method of claim 1, wherein the method is characterized by, In step S3, the weak base solution is a carbonate solution or a phosphate solution, the concentration of which is 5.0-20.0 g / L, the reaction temperature is 25-100 ℃, and the reaction time is 30-120 min. 5.The method of claim 4, wherein the method further comprises, after the step of separating the electrolyte from the cathode active material, a step of separating the cathode active material from the anode active material. The carbonate is ammonium carbonate or sodium carbonate, and the phosphate is ammonium phosphate, diammonium hydrogen phosphate or disodium hydrogen phosphate. 6.The method of claim 1, wherein the method is characterized by, In step S3, the lithium salt product is lithium fluoride or / and lithium phosphate, the purity of which is not less than 98%. 7.The method of claim 1, wherein the method is characterized by, In step S5, the first stage of vacuum distillation is performed under the following conditions: distillation temperature is 90-130 ℃, distillation time is 90-150 min, and pressure is-0.10~-0.08 MPa; the second stage of vacuum distillation is performed under the following conditions: distillation temperature is 285-300 ℃, distillation time is 90-150 min, and pressure is-0.1~-0.08 MPa. 8.The method of claim 1, wherein the method is characterized by, In step S5, the recovered ethylene carbonate has a purity of not less than 99%. 9.The method of claim 1, wherein the method is characterized by, In step S5, the recovered dimethyl carbonate and methyl ethyl carbonate mixed solvent has a volume ratio of dimethyl carbonate to methyl ethyl carbonate of 1:1.5-2.

5.

10. Use of the ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate mixed solvent, and lithium salt product obtained by the method of any one of claims 1 to 9 in preparing lithium ion battery electrolyte.

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