Method for efficient recovery of electrolyte from spent lithium-ion batteries

Abstract

The application discloses a kind of waste lithium ion battery electrolyte efficient recovery method, waste lithium ion battery is broken, and the electrolyte is obtained with broken material, the broken material is washed in salt solution, after washing, solid-liquid separation is obtained with filtrate, the filtrate is stratified, and water phase and organic phase are obtained, organic phase is mixed with methanol, under the condition that temperature is 60-100 DEG C, vacuum degree is 10-80kPa, dimethyl carbonate crude product is distilled out.The application utilizes salt solution washing, and the solute that does not react with electrolyte is dissolved in salt solution, so that the density of water phase is larger, electrolyte can be stratified with water phase and float on water phase, realize electrolyte and water stratification, part of metal cation in part of salt enters organic phase during salt solution washing process, under the catalysis of metal cation, ester exchange reaction occurs between carbonate and methanol to generate dimethyl carbonate, temperature control is steamed out dimethyl carbonate crude product, and the purity of distillated carbonate product is high, which can be sold on market.

Description

Technical Field

[0001] This invention belongs to the field of battery material recycling technology, specifically relating to a method for efficient recycling of waste lithium-ion battery electrolyte. Background Technology

[0002] The electrolyte accounts for about 17% of the weight of a lithium-ion battery. It is generally composed of carbonate organic solvents such as ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC), lithium electrolyte salt lithium hexafluorophosphate (LiPF6), and additives. During use, some lithium ions migrate into the electrolyte. The lithium content in the electrolyte of waste lithium-ion batteries can reach 7-14 g / L, which has high recycling value.

[0003] The biggest problems with lithium-ion electrolyte recycling are: 1. Electrolyte collection: In lithium-ion batteries, the electrolyte is distributed between the positive and negative electrodes and the separator. When the electrolyte is poured out of the battery, most of it remains between the electrodes and the separator, leaving very little that can be poured directly out. Current literature lacks efficient and convenient methods for electrolyte collection. 2. Carbonate recycling: Current literature reports on carbonates obtained through direct vacuum distillation. However, the carbonate products obtained through vacuum distillation are not single carbonates but mixtures of several carbonates, making them difficult to reuse and market. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for efficient recycling of waste lithium-ion battery electrolyte, which can economically and efficiently collect electrolyte and produce a high-purity carbonate product from distillation.

[0005] According to one aspect of the present invention, a method for efficient recycling of waste lithium-ion battery electrolyte is provided, comprising the following steps:

[0006] S1: The waste lithium-ion battery is crushed to obtain crushed material containing electrolyte. The crushed material is washed in a salt solution. After washing, solid and liquid are separated to obtain filtrate.

[0007] S2: The filtrate is allowed to stand and separate into layers to obtain an aqueous phase and an organic phase;

[0008] S3: The organic phase is mixed with methanol, and the crude dimethyl carbonate product is distilled off under conditions of 60-100℃ and 10-80kPa.

[0009] In some embodiments of the present invention, in step S1, the electrolyte comprises the following components: lithium salt 1-2 mol / L, dimethyl carbonate 40-60 v%, methyl ethyl carbonate 5-25 v%, ethylene carbonate 10-25 v%, and propylene carbonate 0-10 v%. The lithium salt is lithium hexafluorophosphate.

[0010] In some embodiments of the present invention, in step S1, the salt solution is a neutral salt solution. Further, the salt in the salt solution is selected from one or more of sodium chloride, sodium sulfate, potassium chloride, or potassium sulfate.

[0011] In some embodiments of the present invention, in step S1, the mass concentration of the salt solution is 5-25%, and the liquid-to-solid ratio of the salt solution to the crushed material is (2-8):1L / kg.

[0012] In some embodiments of the present invention, in step S1, the washing is carried out at a stirring speed of 60-400 r / min.

[0013] In some embodiments of the present invention, the washing time in step S1 is 5-30 minutes.

[0014] In some embodiments of the present invention, in step S2, the aqueous phase is returned to step S1 for the washing process.

[0015] In some embodiments of the present invention, in step S2, the settling time is 0.5-3 hours.

[0016] In some embodiments of the present invention, in step S3, the volume ratio of the organic phase to methanol is 1:(0.2-1).

[0017] In some embodiments of the present invention, in step S3, the crude dimethyl carbonate product is subjected to freeze crystallization, and then the resulting dimethyl carbonate crystals are heated and melted to obtain pure dimethyl carbonate. Further, the freeze crystallization temperature is -5 to 3°C.

[0018] In some embodiments of the present invention, in step S3, before distillation, the temperature is raised to 55-80°C at atmospheric pressure and reacted for 1-3 hours.

[0019] In some embodiments of the present invention, in step S3, the distillate residue proceeds to the next lithium extraction process. The distillate residue can also be purified by fractional distillation to separate and purify byproducts such as ethylene glycol and propylene glycol.

[0020] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved:

[0021] The main component of the electrolyte in lithium-ion batteries is carbonate. Several types of carbonate are insoluble in water, and the density of carbonate is very close to that of water. They are miscible with water but neither dissolve in water nor separate into layers. They form small droplets in water and are difficult to separate from water. This invention utilizes a salt solution of a certain concentration for washing. The salt solution contains solutes that do not react with the electrolyte, increasing the density of the aqueous phase. Since the electrolyte density is lower than that of the aqueous phase, the electrolyte can separate into layers with the aqueous phase and float on top, achieving stratification between the electrolyte and water. Simultaneously, during the salt washing process, some metal cations from the salt enter the organic phase. Under the catalysis of these metal cations, carbonates undergo transesterification with methanol to produce dimethyl carbonate. Some of the reaction formulas are as follows: (CH2O)2CO (ethylene carbonate) + 2CH3OH → (CH3O)2CO + HOCH2CH2OH, C4H6O3 (propylene carbonate) + 2CH3OH → (CH3O)2CO + CH3CHOHCH2OH. The ethylene glycol and propylene glycol produced, along with other carbonates, have boiling points above 100℃, while dimethyl carbonate has a boiling point of only 90℃. Therefore, crude dimethyl carbonate can be distilled off at a controlled temperature, and subsequently purified by freeze crystallization. This invention enables economical and efficient collection of electrolyte, and the distilled carbonate product has high purity and can be sold on the market. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0023] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0024] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0025] Example 1

[0026] A method for efficient recycling of waste lithium-ion battery electrolyte, referring to Figure 1 The specific process is as follows:

[0027] Take 5 kg of waste ternary lithium batteries, discharge them completely, and then crush them using a crusher to release the electrolyte from the lithium-ion batteries. Add the crushed battery fragments containing electrolyte to 20 L of 10% sodium sulfate saline solution and wash at room temperature with stirring for 10 min. After washing, use a coarse sieve to remove and drain the coarse battery fragments, then filter to remove fine residue. Let the filtered solution stand in a separatory bucket for 0.5 h to separate the aqueous phase and electrolyte. Return the aqueous phase to the previous step to wash the battery fragments. Collect 600 mL of electrolyte. 200 mL of methanol was added to the liquid, and the mixture was heated to 60 °C under normal pressure in a rotary evaporator for 2 h. Distillation was carried out for 1 h under a vacuum of 30 kPa and a distillation temperature of 80 °C to obtain 500 mL of distillate. The distillation residue was then sent to the next lithium extraction process. The distillate was placed in a refrigerator and frozen at 0 °C for 1 h. After centrifugation and filtration at 0 °C, dimethyl carbonate crystals were obtained. The dimethyl carbonate crystals were then melted at room temperature to obtain 400 mL of dimethyl carbonate product. GC-MS analysis showed that the purity of dimethyl carbonate was 99%.

[0028] Example 2

[0029] A method for efficient recycling of waste lithium-ion battery electrolyte, the specific process of which is as follows:

[0030] Take 5 kg of waste ternary lithium batteries, discharge them completely, and then crush them using a crusher to release the electrolyte from the lithium-ion batteries. Add the crushed battery fragments containing electrolyte to 15 L of 15% sodium chloride saline solution and wash at room temperature with stirring for 20 min. After washing, use a coarse sieve to remove and drain the coarse battery fragments, then filter to remove fine residue. Let the filtered solution stand in a separatory bucket for 1 h to separate the aqueous phase and electrolyte. Return the aqueous phase to the previous step to wash the battery fragments. Collect 540 mL of electrolyte. 150 mL of methanol was added to the liquid, and the mixture was heated to 60 °C under normal pressure in a rotary evaporator for 2 h. Distillation was carried out for 1 h under a vacuum of 40 kPa and a distillation temperature of 80 °C to obtain 420 mL of distillate. The distillation residue was then sent to the next lithium extraction process. The distillate was placed in a refrigerator and frozen at 0 °C for 1 h. After centrifugation and filtration at 0 °C, dimethyl carbonate crystals were obtained. The dimethyl carbonate crystals were then melted at room temperature to obtain 340 mL of dimethyl carbonate product. GC-MS analysis showed that the purity of dimethyl carbonate was 99%.

[0031] Example 3

[0032] A method for efficient recycling of waste lithium-ion battery electrolyte, the specific process of which is as follows:

[0033] Take 5 kg of waste ternary lithium batteries, discharge them completely, and then crush them using a crusher to release the electrolyte from the lithium-ion batteries. Add the crushed battery fragments containing electrolyte to 25 L of 20% potassium sulfate saline solution and wash with stirring at room temperature for 20 min. After washing, use a coarse sieve to remove and drain the coarse battery fragments, then filter to remove fine residue. Let the filtered solution stand in a separatory bucket for 0.5 h to separate the aqueous phase and electrolyte. Return the aqueous phase to the previous step to wash the battery fragments. Collect 620 mL of electrolyte. 200 mL of methanol was added to the solution, and the mixture was heated to 60 °C under normal pressure in a rotary evaporator for 2 h. Distillation was carried out for 1 h under a vacuum of 20 kPa and a distillation temperature of 80 °C to obtain 540 mL of distillate. The distillation residue was then sent to the next lithium extraction process. The distillate was placed in a refrigerator and frozen at 0 °C for 1 h. After centrifugation and filtration at 0 °C, dimethyl carbonate crystals were obtained. The dimethyl carbonate crystals were then melted at room temperature to obtain 420 mL of dimethyl carbonate product. GC-MS analysis showed that the purity of dimethyl carbonate was 99%.

[0034] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

[0035] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail. When a mass, concentration, temperature, time, or other value or parameter is expressed as a range, preferred range, or a series of upper and lower preferred values, this shall be understood to specifically disclose all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. For example, a range of 1-50 should be understood to include selections from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36 Any number, combination of numbers, or subrange of numbers between the integers 1, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, and all decimal values ​​between these integers, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider “nested subranges” extending from any endpoint of the range. For example, nested subranges of the exemplary range 1-50 could include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in another direction.

Claims

1. A method for efficient recycling of waste lithium-ion battery electrolyte, characterized in that, Includes the following steps: S1: The waste lithium-ion battery is crushed to obtain crushed material containing electrolyte. The crushed material is washed in a salt solution. After washing, solid and liquid are separated to obtain filtrate. S2: The filtrate is allowed to stand and separate into layers to obtain an aqueous phase and an organic phase; S3: The organic phase is mixed with methanol, and the crude dimethyl carbonate product is distilled off under conditions of 60-100℃ and 10-80kPa. In step S1, the salt solution is a neutral salt solution; the salt in the salt solution is selected from one or more of sodium chloride, sodium sulfate, potassium chloride, or potassium sulfate; the mass concentration of the salt solution is 5-25%, and the liquid-to-solid ratio of the salt solution to the crushed material is (2-8):1 L / kg; the washing is carried out at 60°C. The washing process is carried out at a stirring speed of 400 r / min, and the washing time is 5-30 min. In step S3, the volume ratio of the organic phase to methanol is 1:(0.2-1); before distillation, the temperature is first raised to 55°C at atmospheric pressure. 80℃ reaction 1 3h.

2. The method according to claim 1, characterized in that, In step S1, the washing is carried out at a stirring speed of 60-400 r / min.

3. The method according to claim 1, characterized in that, In step S1, the washing time is 5-30 minutes.

4. The method according to claim 1, characterized in that, In step S2, the aqueous phase is returned to step S1 for the washing process.

5. The method according to claim 1, characterized in that, In step S2, the settling time is 0.5-3 hours.

6. The method according to claim 1, characterized in that, In step S3, the crude dimethyl carbonate product is frozen and crystallized, and then the resulting dimethyl carbonate crystals are heated and melted to obtain pure dimethyl carbonate.

7. The method according to claim 1, characterized in that, In step S3, the residual liquid after distillation enters the next lithium extraction process.

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