A method for recovering lithium from lithium-ion battery electrolyte

Abstract

The application discloses a method for recovering lithium from lithium ion battery electrolyte, which comprises the following steps: mixing waste electrolyte and extractant, and then separating the mixture into upper organic phase and lower lithium-loaded phase; the density of the upper organic phase is not higher than 1.07 g / cm 3 , and the density of the lower lithium-loaded phase is 1.15-1.5 g / cm 3 ; the waste electrolyte comprises lithium ion and ester organic solvent; the extractant comprises aqueous solution of salt and solvent; the solvent comprises at least one of ethanol and methanol; the upper organic phase comprises the ester organic solvent; and the lithium-loaded phase comprises water. The method for recovering lithium solves the problem that carbonic ester is difficult to separate from water after mixing.

Description

Technical Field

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

[0002] Electrolyte is a key material in lithium-ion batteries, acting as a conductor between the positive and negative electrodes. It is essential for the normal operation of lithium-ion batteries and ensures their high voltage and high specific energy. Electrolytes are generally composed of high-purity organic solvents and lithium salts (lithium hexafluorophosphate, LiF6PO4), resulting in a large amount of waste lithium-ion battery electrolyte at the end of the battery's lifespan. During use, some lithium ions migrate into the electrolyte, leading to a lithium content of 7–14 g / L in the waste electrolyte. Furthermore, waste lithium-ion battery electrolyte absorbs moisture and deteriorates in the air, and contains toxic components. Leakage into the air can pollute the environment. If waste lithium-ion battery electrolyte is not properly disposed of, it will cause significant harm to the environment and human health.

[0003] The biggest problems with lithium-ion electrolyte recycling are: 1. In lithium-ion batteries, the electrolyte is distributed between the positive and negative electrodes and the separator. Electrolytes collected by directly crushing individual cells contain excessive impurities, most of which adhere to the crushed material, making electrolyte collection impossible. Although most of the carbonates in the electrolyte are insoluble in water, their density is close to that of water, making separation difficult after mixing. Therefore, good separation results cannot be achieved, and current literature lacks efficient and convenient methods for electrolyte collection. 2. Currently, lithium recovery directly uses alkaline solutions. However, ester organic solvents undergo varying degrees of hydrolysis in alkaline environments, making further recycling impossible.

[0004] Therefore, developing a method to recover lithium from lithium-ion battery electrolytes, which can solve the problem of the difficulty in separating ester organic solvents from water after mixing in waste lithium-ion battery electrolytes, is currently an urgent task. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for recovering lithium from lithium-ion battery electrolytes. This solves the problem of difficulty in separating carbonates and water after mixing in the electrolyte.

[0006] A method for recovering lithium from a lithium-ion battery electrolyte according to a first aspect of the present invention includes mixing waste electrolyte and an extractant, followed by stratification to obtain a solution with a density not exceeding 1.07 g / cm³. 3 The upper organic phase has a density of 1.15–1.5 g / cm³. 3 The lower layer loaded with lithium phase;

[0007] The waste electrolyte includes lithium ions and ester-based organic solvents;

[0008] The extractant comprises an aqueous solution of salt and a solvent;

[0009] The solvent includes at least one of ethanol and methanol;

[0010] The upper organic phase includes the ester-based organic solvent;

[0011] The lithium-loaded phase includes water.

[0012] A method for recovering lithium from lithium-ion battery electrolyte according to an embodiment of the present invention has at least the following beneficial effects:

[0013] This invention increases the density of the aqueous phase by preparing an aqueous salt solution, and then mixes it with at least one of ethanol and methanol in a certain proportion to extract lithium from the waste electrolyte. After standing for a period of time, the layers are separated, thus achieving the separation of ester organic solvents in the organic phase of the waste electrolyte from the loaded lithium phase. This solves the problem of the difficulty in separating ester organic solvents from water after mixing in the electrolyte.

[0014] According to some embodiments of the present invention, the ester organic solvent includes at least one of dimethyl carbonate and ethyl methyl carbonate.

[0015] According to some embodiments of the present invention, the mass concentration of the aqueous solution of the salt is 5-25%.

[0016] According to some embodiments of the present invention, the volume ratio of the waste electrolyte, the aqueous solution of the salt, and the solvent is 1-3:1-3:1-3.

[0017] According to some embodiments of the present invention, the volume ratio of the waste electrolyte, the aqueous solution of the salt, and the organic solvent is 1:1:1, 2:1:1, 2:2:1, 2:1:2, 1; 3:3, 3:1:1, 3:2:1, 3:3:1, or 3:1:3.

[0018] At the above volume ratio, the density of the upper organic phase is no higher than 1.07 g / cm³. 3 The density of the lower-layer supported lithium phase is approximately 1.15–1.5 g / cm³. 3 It can achieve the separation of the upper organic phase and the lower supported lithium phase.

[0019] According to some embodiments of the present invention, the layering time is 0.5 to 3 hours. The layering method includes standing.

[0020] According to some embodiments of the present invention, the aqueous solution of the salt includes at least one of an aqueous solution of a sulfate and an aqueous solution of a chloride.

[0021] According to some embodiments of the present invention, the solute in the aqueous solution of the sulfate includes at least one of potassium sulfate and sodium sulfate.

[0022] According to some embodiments of the present invention, the solute in the aqueous solution of the chloride salt includes at least one of sodium chloride and potassium chloride.

[0023] According to some embodiments of the present invention, the mixing temperature is 15–100°C.

[0024] According to some embodiments of the present invention, the mixing time is 5 to 30 minutes.

[0025] According to some embodiments of the present invention, the mixing is carried out by stirring at a stirring speed of 60 to 400 r / min.

[0026] According to some embodiments of the present invention, the method for recovering lithium further includes distilling the upper organic phase.

[0027] According to some embodiments of the present invention, the distillation includes batch distillation.

[0028] According to some embodiments of the present invention, the temperature of the batch distillation is 60-120°C, the pressure of the batch distillation is 10-50 kPa, and the time of the batch distillation is 10-30 min.

[0029] Under the above distillation conditions, dimethyl carbonate and ethyl methyl carbonate can be recovered.

[0030] According to some embodiments of the present invention, the method for recovering lithium further includes removing impurities from the lower layer of loaded lithium phase to obtain a liquid phase product.

[0031] According to some embodiments of the present invention, the impurity removal includes distillation.

[0032] According to some embodiments of the present invention, the distillation temperature is 15°C to 100°C, the distillation vacuum is 10 kPa to 70 kPa, and the distillation time is 10 to 45 min.

[0033] The distillation process collects distillate residue and fractions; the fraction recovery method includes condensation.

[0034] According to some embodiments of the present invention, the condensation temperature is 20–25°C.

[0035] According to some embodiments of the present invention, the method for recovering lithium further includes a solvent using the fraction as an extractant.

[0036] According to some embodiments of the present invention, the method for recovering lithium further includes mixing the distillation residue with an aqueous solution of carbonate.

[0037] According to some embodiments of the present invention, the mass concentration of the carbonate is 1% to 15%.

[0038] According to some embodiments of the present invention, the amount of carbonate added is based on a molar ratio of Li + CO3 2- The ratio is 2:1.2 to 1.4.

[0039] According to some embodiments of the present invention, the mixing time of the liquid phase product and the aqueous solution of carbonate is 20 to 30 minutes.

[0040] According to some embodiments of the present invention, after the liquid product and the aqueous solution of the carbonate are mixed, solid-liquid separation is performed, and the solid product and filtrate are collected separately.

[0041] According to some embodiments of the present invention, the filtrate is a pressure filtrate.

[0042] According to some embodiments of the present invention, after collecting the filtrate, acid is added to the filtrate.

[0043] According to some embodiments of the present invention, the pH value of the filtrate after acidification is 0.5 to 1.

[0044] The purpose of adding acid is to remove carbonate ions from the filtrate.

[0045] According to some embodiments of the present invention, the pH of the acidified filtrate is adjusted to 6-7 to obtain the salt solution as part of the extractant.

[0046] The aqueous solution of the salt obtained above can be recycled as part of the extractant.

[0047] According to some preferred embodiments of the present invention, the lower layer supported lithium phase further includes concentration before impurity removal, the concentration comprising the following steps:

[0048] S1. The solvent is added to the lower lithium-loaded phase and used as the extractant to extract the waste electrolyte, thereby obtaining the upper organic phase and the secondary lithium-loaded phase.

[0049] S2. After collecting the secondary loaded lithium phase, add the solvent and use it as an extractant again. Repeat step S1 until the lithium content in the resulting liquid phase is 16-20 g / L.

[0050] This increases the lithium content in the loaded lithium phase. When the solvent and salt aqueous solution are mixed with the waste electrolyte, a small amount of solvent will evaporate, and a small amount of solvent will also enter the upper organic phase (excluding the lithium electrolyte phase) during separation. Therefore, a certain amount of solvent needs to be added, but the salt aqueous solution does not need to be added.

[0051] According to some preferred embodiments of the present invention, in step S1, the waste electrolyte and the lower layer loaded lithium phase are added in a volume ratio of 1:1.

[0052] According to some preferred embodiments of the present invention, in step S1, the volume of the lower loaded lithium phase is denoted as V1, in step S2, the volume of the secondary loaded lithium phase is denoted as V2, and the amount of solvent added in step S2 is V2-V1.

[0053] After adding solvent and waste electrolyte to the separated lithium-loaded phase, the lithium concentration in the lithium-loaded phase gradually increases, which is beneficial for lithium ion precipitation. This invention achieves lithium enrichment in the lithium-loaded phase by adding waste electrolyte and solvent before impurity removal, which is beneficial for lithium recovery.

[0054] In this invention, waste electrolyte, brine, and ethanol are mixed evenly according to the above-mentioned addition amounts to extract lithium from the electrolyte. After standing for a period of time, the mixture is separated into layers to obtain an upper organic phase and a lower lithium-loaded phase. The lithium-loaded phase is subjected to low-temperature distillation to collect the solvent ethanol in the extractant, which can be recycled for extraction. Carbonate is added to the distillation residue, stirred and mixed, and filtered to obtain lithium carbonate and filtrate. Strong acid is added to the filtrate to remove carbonate ions, and the pH is adjusted to obtain an aqueous solution of the salt in the extractant, which can be recycled as the extractant. The upper organic phase is subjected to intermittent distillation to obtain dimethyl carbonate and ethyl methyl carbonate. Attached Figure Description

[0055] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0056] Figure 1 This is a process flow diagram of the lithium recovery method in Embodiment 2 of the present invention.

[0057] Figure 2 This is a process flow diagram of the lithium recovery method in Embodiment 1 of the present invention. Detailed Implementation

[0058] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0059] Example 1

[0060] This embodiment discloses a method for recovering lithium from lithium-ion battery electrolyte. The waste ternary lithium battery contains the following components by weight percentage: 30% dimethyl carbonate, 33% ethylene carbonate, 32% methyl ethyl carbonate, and 9 g / L lithium.

[0061] The specific steps are as follows:

[0062] S1. Take a used ternary lithium battery, discharge it completely, and collect 2000 ml of electrolyte (used lithium-ion battery) by punching a hole. Add it to 1000 ml of 15% sodium chloride saline solution, then add 1000 ml of 100% ethanol. Mix at 50°C and 400 rpm. Wash for 15 minutes, let stand for 0.5 hours, and allow to separate into layers. At this point, the density of the upper organic phase is 0.9 g / cm³. 3 The density of the lower-layer lithium-supported phase is 1.15 g / cm³. 3 The liquid was separated into a lower lithium-loaded phase and an upper lithium-free electrolyte phase.

[0063] S2. The upper lithium-removed electrolyte phase is subjected to batch distillation to obtain dimethyl carbonate and ethyl methyl carbonate. The batch distillation conditions are 80℃, 30kPa, and 20min.

[0064] S3. After adding 100 mL of ethanol and 1 L of electrolyte to the lower lithium-loaded phase, repeat step S1. The lithium concentration in the lithium-loaded phase will continue to increase, and the final lithium content in the lithium-loaded phase (secondary lithium-loaded phase) of the system will be 20 g / L.

[0065] S4. Evaporate the ethanol from the lithium-loaded phase in a rotary evaporator at 80℃ and 30kPa for 20min. Collect the solvent ethanol from the extractant at 20℃. Test the lithium content in the residual liquid after ethanol evaporation, according to the molar ratio of Li... + / CO3 2- Add 10% sodium carbonate solution to 2 / 1.2, stir and react for 20 min, then filter under pressure to obtain lithium carbonate precipitate and filtrate.

[0066] S5. Add hydrochloric acid to the filtrate from step S4 to adjust the pH to 1 to remove CO3. 2- After adjusting the pH to 7 with sodium hydroxide, an aqueous solution of the salt in the extractant is obtained. This allows for the recycling of the salt aqueous solution.

[0067] Figure 2 This is a process flow diagram of the lithium recovery method in Embodiment 1 of the present invention.

[0068] According to ICP elemental analysis, in step S1, the lithium content in the upper lithium-free electrolyte phase is 0.01 g / L. After obtaining lithium carbonate precipitate in the lower layer, the lithium extraction rate of this part is 99%, calculated as (9-0.01) / 9 = 99%.

[0069] The extraction rate is calculated as (lithium content in the electrolyte - lithium content in the upper lithium-free electrolyte phase after stratification in step S1) / lithium content in the electrolyte.

[0070] In step S2 of the test using GC-MS qualitative and quantitative analysis, the recovery rate of dimethyl carbonate was 80%, and the recovery rate of ethyl methyl carbonate was 75%.

[0071] Example 2

[0072] This embodiment discloses a method for recovering lithium from lithium-ion battery electrolyte. The waste ternary lithium battery contains the following components by weight percentage: 30% dimethyl carbonate, 33% ethylene carbonate, 32% methyl ethyl carbonate, and 9 g / L lithium.

[0073] S1. Take a used ternary lithium battery, discharge it completely, and collect 2000 ml of electrolyte by punching a hole. Add it to 1000 ml of 5% sodium chloride saline solution, then add 1000 ml of ethanol and mix. The mixing temperature is 50℃, the stirring speed is 400 r / min, and the mixture is washed for 15 min. After standing for 0.5 h, the layers are separated, and the lower lithium-loaded phase and the upper lithium-removed electrolyte phase are collected.

[0074] S2. The upper lithium-removed electrolyte phase is subjected to batch distillation to obtain dimethyl carbonate and ethyl methyl carbonate. The batch distillation conditions are 80℃, 30kPa, and 20min.

[0075] S4. Evaporate the ethanol from the lithium-loaded phase in a rotary evaporator under a vacuum of 30 kPa and a temperature of 60°C for 40 min. Collect the solvent ethanol from the extractant at 25°C and test the lithium content in the residual liquid after ethanol evaporation, according to the molar ratio of Li... + / CO3 2- Add 5% sodium carbonate solution to 2 / 1.2, stir and react for 20 min, then filter under pressure to obtain lithium carbonate precipitate and filtrate.

[0076] S5. Add hydrochloric acid to the filtrate from step S4 to adjust the pH to 1 to remove carbonate ions, and then add sodium hydroxide to adjust the pH to 7 to obtain an aqueous solution of the salt in the extractant.

[0077] According to ICP elemental analysis, in step S1, the lithium content in the upper lithium-free electrolyte phase is 0.01 g / L, and after obtaining lithium carbonate precipitate in the lower layer, the lithium extraction rate of this part is 99%.

[0078] In step S2 of the test using GC-MS qualitative and quantitative analysis, the recovery rate of dimethyl carbonate was 85%, and the recovery rate of ethyl methyl carbonate was 75%.

[0079] Figure 1 This is a process flow diagram of the lithium recovery method in Embodiment 2 of the present invention.

[0080] Example 3

[0081] This embodiment discloses a method for recovering lithium from lithium-ion battery electrolyte. The waste ternary lithium battery contains the following components by weight percentage: 30% dimethyl carbonate, 33% ethylene carbonate, 32% methyl ethyl carbonate; lithium 9 g / L. The specific steps are as follows:

[0082] S1. Take a used ternary lithium battery, discharge it completely, and collect 1000 ml of electrolyte by punching a hole. Add 1000 ml of the salt aqueous solution from step S5 of Example 1, and then add 1000 ml of ethanol recovered by condensation in step S4 of Example 1. Mix at 80°C and 400 r / min. Wash for 15 min, let stand for 0.5 h, and then separate the layers. At this point, the density of the upper organic phase is 0.9 g / cm³. 3 The density of the lower-layer lithium-supported phase is 1.3 g / cm³. 3 The liquid was separated into a lower lithium-loaded phase and an upper lithium-free electrolyte phase.

[0083] S2. The upper lithium-removed electrolyte phase is subjected to batch distillation to obtain dimethyl carbonate and ethyl methyl carbonate. The batch distillation conditions are 80℃, 30kPa, and 20min.

[0084] S3. After adding a certain volume of ethanol and electrolyte to the lower lithium-loaded phase, and washing it multiple times, the lithium concentration in the lithium-loaded phase continuously increases, allowing for subsequent ethanol recovery and lithium extraction.

[0085] S4. Evaporate the ethanol from the lithium-loaded phase in a rotary evaporator under a vacuum of 30 kPa and a temperature of 60°C for 40 min. Collect the solvent ethanol in the extractant at 20°C and test the lithium content in the residual liquid after ethanol evaporation, according to the molar ratio of Li... + / CO3 2- Add 10% sodium carbonate solution to 2 / 1.2, stir and react for 20 min, then filter under pressure to obtain lithium carbonate precipitate and filtrate.

[0086] S5. Add hydrochloric acid to the filtrate from step S4 to adjust the pH to 1 to remove carbonate ions, and then add sodium hydroxide to adjust the pH to 7 to obtain an aqueous solution of the salt in the extractant.

[0087] According to ICP elemental analysis, in step S1, the lithium content in the upper lithium-free electrolyte phase is 0.01 g / L, and after obtaining lithium carbonate precipitate in the lower layer, the lithium extraction rate of this part is 99%.

[0088] In step S2 of the test using GC-MS qualitative and quantitative analysis, the recovery rate of dimethyl carbonate was 80%, and the recovery rate of methyl ethyl carbonate was 70%.

[0089] Comparative Example 1

[0090] This comparative example discloses a method for recovering lithium from lithium-ion battery electrolyte. The difference between this comparative example and Example 1 is that ethanol, which was used in step S1 of Example 1, was not added in this comparative example, while the other conditions are the same as in Example 1.

[0091] The above steps did not yield lithium carbonate precipitate. The combined action of the salt aqueous solution and ethanol separates the electrolyte into layers and extracts lithium. Without ethanol, lithium cannot be extracted, thus preventing the formation of lithium carbonate precipitate in subsequent steps.

[0092] Comparative Example 2

[0093] This comparative example discloses a method for recovering lithium from lithium-ion battery electrolyte. The difference between this comparative example and Example 1 is that the 15% sodium chloride brine used in step S1 of Example 1 was not added in this comparative example; the other conditions are the same as in Example 1. Following the above steps, it is impossible to collect the lithium-loaded phase and the lithium-removed electrolyte phase. Under the combined action of the solution and ethanol, the ethanol extracts lithium from the electrolyte, while the brine mainly serves to separate the layers. Without the brine, the upper organic phase and the lower lithium-loaded phase have similar densities, making separation impossible, and therefore, it is impossible to collect the lithium-loaded phase and the lithium-removed electrolyte phase.

[0094] Comparative Example 3

[0095] This comparative example discloses a method for recovering lithium from lithium-ion battery electrolyte. The difference between this comparative example and Example 1 is that the density of the upper organic phase in this comparative example is 1.1, while the other conditions are the same as in Example 1.

[0096] Under these conditions, the upper organic phase and the lower lithium-loaded phase have similar densities, making it impossible to separate them into layers. Therefore, it is impossible to collect the lithium-loaded phase and the lithium-free electrolyte phase.

[0097] Comparative Example 5

[0098] This comparative example discloses a method for recovering lithium from lithium-ion battery electrolyte. The difference between this comparative example and Example 1 is that the density of the lower layer loaded lithium phase in this comparative example is 1.0, while the other conditions are the same as in Example 1.

[0099] Under these conditions, the upper organic phase and the lower lithium-loaded phase have similar densities, making it impossible to separate them into layers. Therefore, it is impossible to collect the lithium-loaded phase and the lithium-free electrolyte phase.

[0100] Comparative Example 6

[0101] This comparative example discloses a method for recovering lithium from lithium-ion battery electrolyte. The difference between this comparative example and Example 1 is that the density of the lower layer loaded lithium phase in this comparative example is 1.6, while the other conditions are the same as in Example 1.

[0102] According to ICP elemental analysis, in step S1, the lithium content in the upper lithium-free electrolyte phase is 0.12 g / L, and after obtaining lithium carbonate precipitate in the lower layer, the lithium extraction rate of this part is 98%.

[0103] In step S2 of the test using GC-MS qualitative and quantitative analysis, the recovery rate of dimethyl carbonate was 80%, and the recovery rate of methyl ethyl carbonate was 70%.

[0104] Under these conditions, the excessive amount of brine solution used resulted in unnecessary waste and increased the difficulty of subsequent brine solution treatment. The lithium removal efficiency decreased compared to the previous example.

[0105] 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. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for recovering lithium from lithium-ion battery electrolyte, characterized in that, This includes mixing the waste electrolyte and extractant, followed by stratification to obtain a solution with a density not exceeding 1.07 g / cm³. 3 The upper organic phase has a density of 1.15–1.5 g / cm³. 3 The lower layer loaded with lithium phase; The waste electrolyte includes lithium ions and ester-based organic solvents; The extractant comprises an aqueous solution of salt and a solvent, wherein the mass concentration of the aqueous solution of salt is 5-25%. The aqueous solution of the salt includes at least one of an aqueous solution of a sulfate and an aqueous solution of a chloride; The solvent includes at least one of ethanol and methanol; The upper organic phase includes the ester-based organic solvent; The lithium-loaded phase includes water; The volume ratio of the waste electrolyte, the aqueous solution of the salt, and the solvent is 1-3:1-3:1-3; The process also includes adding the lower lithium-loaded phase to waste electrolyte and the solvent, mixing them to form a layer, resulting in an upper organic phase and a lower lithium-loaded phase. The lower lithium-loaded phase is collected, and the waste electrolyte and the solvent are repeatedly added until the lithium content in the lower lithium-loaded phase reaches 16%. 20g / L.

2. The method according to claim 1, characterized in that, The mixing temperature is 15–100°C.

3. The method according to claim 1, characterized in that, The mixing time is 5 to 30 minutes.

4. The method according to claim 1, characterized in that, The method for recovering lithium also includes distilling the upper organic phase.

5. The method according to claim 1, characterized in that, The method for recovering lithium further includes removing impurities from the lower layer of loaded lithium phase to obtain a liquid phase product.

6. The method according to claim 5, characterized in that, The purification process includes distillation.

7. The method according to claim 6, characterized in that, The distillation temperature is 15℃~100℃, the distillation vacuum degree is 10kPa~70kPa, and the distillation time is 10~45min.

8. The method according to claim 5, characterized in that, The method for recovering lithium further includes mixing the liquid product with an aqueous solution of carbonate.

9. The method according to claim 8, characterized in that, The mass concentration of the carbonate is 1% to 15%.

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