A method for recovering lithium carbonate from waste lithium-ion battery electrolyte

Abstract

This invention belongs to the field of lithium-ion batteries and discloses a method for recovering lithium carbonate from waste lithium-ion battery electrolytes. The method involves adding an electrolyte containing lithium hexafluorophosphate to a reaction system containing an aqueous solution of soluble carbonates, continuously stirring and dispersing the mixture to ensure continuous mixing of the oil and water phases, and injecting micro-nano bubbles from the bottom of the reaction system. During or after the reaction, a precipitate is separated. After the reaction, the aqueous and oil phases are separated. This method utilizes the characteristic of micro-nano bubbles to stably distribute at the water-oil interface, and simultaneously uses the energy generated by their bursting to disrupt the water-oil interface, achieving high-speed mixing of oil and water at the micro-interface. This facilitates the combination of carbonate and Li ions, resulting in the precipitation of lithium carbonate. Using this method, the lithium carbonate yield can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a method for recovering lithium carbonate from the electrolyte of waste lithium-ion batteries. Background Technology

[0002] CN202210601906.3 discloses a method for recycling waste electrolyte from lithium-ion batteries, wherein the waste electrolyte contains lithium hexafluorophosphate. The method includes the following steps: S1: Adding a saline aqueous solution as an extractant to the collected waste electrolyte for extraction, separating the lower organic solution and the upper aqueous solution, and recovering the lower organic solution to obtain an organic solvent; S2: Adding water-soluble carbonates and / or water-soluble phosphates to the upper aqueous solution from step S1, filtering, and separating to obtain lithium precipitate. This method requires multiple extractions to achieve a high recovery rate and purity.

[0003] The technical problem addressed in this case is: how to simplify the process for recovering lithium salts from electrolytes. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recovering lithium carbonate from waste lithium-ion battery electrolyte. This method utilizes the characteristic of micro-nano bubbles to be stably distributed at the water-oil interface, and at the same time utilizes the energy generated by the bursting to destroy the water-oil interface, achieving high-speed mixing of oil and water at the water-oil micro interface, realizing the combination of carbonate ions and Li ions, and obtaining lithium carbonate precipitation. Using the method of this invention, the lithium carbonate yield can be significantly improved.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for recovering lithium carbonate from waste lithium-ion battery electrolyte, wherein an electrolyte containing lithium hexafluorophosphate is added to a reaction system, the reaction system containing an aqueous solution of soluble carbonates, and the mixture is continuously stirred and dispersed to continuously mix the oil phase and the aqueous phase, and micro-nano bubbles are injected from the bottom of the reaction system; precipitate is separated during or after the reaction; and the aqueous phase and oil phase are separated after the reaction.

[0006] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, 50-2000L of electrolyte is added to each cubic meter of aqueous solution; the electrolyte contains 1-20wt% lithium hexafluorophosphate.

[0007] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, the reaction system includes a reaction vessel, a filter, a dissolved gas pump, a dissolved gas tank, and a micro / nano bubble generator connected in sequence; the micro / nano bubble generator is located at the bottom of the reaction vessel; the filter is connected to the middle or upper part of the reaction vessel; and a gas supply pipe is connected to the dissolved gas pump.

[0008] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, the volume ratio of oil-water mixture flowing through the dissolved air pump to water-gas volume ratio of the gas injected through the gas filling pipe is 100:2-10.

[0009] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, the particle size of the micro-nano bubbles is 10nm-10μm.

[0010] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, the particle size of the micro-nano bubbles is 100-500 nm.

[0011] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, the reaction temperature in the reactor is from room temperature to 90°C.

[0012] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, the soluble carbonate is sodium carbonate, potassium carbonate, or ammonium carbonate; the ratio of the molar amount of lithium ions to the molar amount of carbonate ions in the soluble carbonate solution is 2:1.1~10; and the concentration of the solute of the soluble carbonate in the aqueous solution is 1wt%~30wt%.

[0013] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, the soluble carbonate is sodium carbonate, potassium carbonate, or ammonium carbonate.

[0014] In the above-mentioned method for recovering lithium carbonate from waste lithium-ion battery electrolyte, the micro-nano bubbles are one of air bubbles, carbon dioxide bubbles, nitrogen bubbles, oxygen bubbles, and ozone bubbles.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] This invention utilizes the characteristic of micro- and nano-bubbles to be stably distributed at the water-oil interface, and at the same time utilizes the energy generated by the bursting to destroy the water-oil interface, thereby achieving high-speed mixing of oil and water at the water-oil micro-interface, realizing the combination of carbonate and Li ions, and obtaining lithium carbonate precipitation. Using the method of this invention, the lithium carbonate yield can be significantly improved. Attached Figure Description

[0017] Figure 1 This is a pipeline flow diagram of an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Introduction to the reaction system

[0020] refer to Figure 1 The reaction system of the present invention includes a reaction vessel 1, a filter 2, a dissolved gas pump 3, a dissolved gas tank 4, and a micro / nano bubble generator 5 connected in sequence; the micro / nano bubble generator is located at the bottom of the reaction vessel; the filter is connected to the middle or upper part of the reaction vessel; and a gas supply pipe 6 is connected to the dissolved gas pump.

[0021] The bottom of the reactor is equipped with a discharge pipe 7, and the reactor is equipped with a stirrer; the lower part of the stirrer consists of three oblique blades 8; the upper part is connected to three evenly arranged blades and vertical blades 9 with overlapping blade surfaces; the oblique blades propel the fluid downwards, and the vertical blades increase the mixing force of the liquid in the upper part; this type of blade is more suitable for mixing oil and water phases.

[0022] The following examples and comparative examples were all implemented using this system.

[0023] Example 1

[0024] A method for recovering lithium carbonate from waste lithium-ion battery electrolyte, specifically comprising:

[0025] An electrolyte containing lithium hexafluorophosphate was added to a reaction vessel containing an aqueous solution of sodium carbonate. The mixture was continuously stirred and dispersed to ensure continuous mixing of the oil and aqueous phases. Micro-nano bubbles were injected from the bottom of the reaction vessel. The reaction temperature was 50°C. Precipitation was separated by a filter during the reaction process. After the reaction, the aqueous and oil phases were separated. The reaction endpoint was characterized by virtually no precipitate in the reaction system, with a reaction time of approximately 4 hours.

[0026] The concentrations of each substance in the electrolyte are: LiPF6 15wt%, EC 28wt%, DMC 28wt%, EMC 28wt%, VC 1wt%; the sodium carbonate concentration in the aqueous solution is 5wt%; 80L of electrolyte is added per cubic meter of aqueous solution.

[0027] The reactor volume is 3.89 m³. 3 The total volume of the oil and water phases is approximately 2.5 m³. 3 The dissolved air pump returns the gas at a speed of 6m / s. 3 / h; head 40m; the micro-nano bubbles are oxygen bubbles with a particle size mainly distributed in 100-500nm; the water-water mixture flowing through the dissolved air pump and the water-gas volume ratio of the gas injected through the gas filling pipe are 100:5, and the pressure of the dissolved air tank is 4bar.

[0028] Example 2

[0029] A method for recovering lithium carbonate from waste lithium-ion battery electrolyte, specifically comprising:

[0030] An electrolyte containing lithium hexafluorophosphate was added to a reaction vessel containing an aqueous solution of sodium carbonate. The mixture was continuously stirred and dispersed to ensure constant mixing of the oil and aqueous phases. Micro-nano bubbles were injected from the bottom of the reaction vessel. The reaction temperature was 70°C. Precipitation was separated by a filter during the reaction process. After the reaction, the aqueous and oil phases were separated. The reaction endpoint was characterized by virtually no precipitate in the reaction system, with a reaction time of approximately 3 hours.

[0031] The concentrations of each substance in the electrolyte are: LiPF6 15wt%, EC 28wt%, DMC 28wt%, EMC 28wt%, VC 1wt%; the sodium carbonate concentration in the aqueous solution is 3wt%; 80L of electrolyte is added per cubic meter of aqueous solution.

[0032] The reactor volume is 3.89 m³. 3 The total volume of the oil and water phases is approximately 2.5 m³. 3 The dissolved air pump returns the gas at a speed of 6m / s. 3 / h; head 40m; the micro-nano bubbles are oxygen bubbles with a particle size mainly distributed in 100-500nm; the water-water mixture flowing through the dissolved air pump and the water-gas volume ratio of the gas injected through the gas filling pipe are 100:3, and the pressure of the dissolved air tank is 4bar.

[0033] Example 3

[0034] A method for recovering lithium carbonate from waste lithium-ion battery electrolyte, specifically comprising:

[0035] An electrolyte containing lithium hexafluorophosphate was added to a reaction vessel containing an aqueous solution of sodium carbonate. The mixture was continuously stirred and dispersed to ensure continuous mixing of the oil and aqueous phases. Micro-nano bubbles were injected from the bottom of the reaction vessel. The reaction temperature was 80°C. Precipitation was separated by a filter during the reaction process. After the reaction, the aqueous and oil phases were separated. The reaction endpoint was characterized by virtually no precipitate in the reaction system, with a reaction time of approximately 6 hours.

[0036] The concentrations of each substance in the electrolyte are: LiPF6 15wt%, EC 28wt%, DMC 28wt%, EMC 28wt%, VC 1wt%; the sodium carbonate concentration in the aqueous solution is 1wt%; 80L of electrolyte is added per cubic meter of aqueous solution.

[0037] The reactor volume is 3.89 m³. 3 The total volume of the oil and water phases is approximately 2.5 m³. 3 The dissolved air pump returns the gas at a speed of 6m / s. 3 / h; head 40m; the micro-nano bubbles are oxygen bubbles, with particle sizes mainly distributed in the range of 100-500nm; the water-to-gas volume ratio of the oil-water mixture flowing through the dissolved air pump and the gas injected through the gas filling pipe is 100:8, and the pressure of the dissolved air tank is 4bar.

[0038] Example 4

[0039] Similar to Example 1, except that the micro-nano bubbles are nitrogen bubbles.

[0040] Example 5

[0041] Similar to Example 1, except that the micro-nano bubbles are air bubbles.

[0042] Example 6

[0043] Similar to Example 1, except that the micro-nano bubbles are carbon dioxide bubbles and the reaction temperature is 80°C.

[0044] Example 7

[0045] A method for recovering lithium carbonate from waste lithium-ion battery electrolyte, specifically comprising:

[0046] An electrolyte containing lithium hexafluorophosphate was added to a reaction vessel containing an aqueous solution of sodium carbonate. The mixture was continuously stirred and dispersed to ensure continuous mixing of the oil and aqueous phases. Micro-nano bubbles were injected from the bottom of the reaction vessel. The reaction temperature was 50°C. Precipitation was separated by a filter during the reaction process. After the reaction, the aqueous and oil phases were separated. The reaction endpoint was characterized by virtually no precipitate in the reaction system, with a reaction time of approximately 4 hours.

[0047] The concentrations of each substance in the electrolyte are: LiPF6 15wt%, EC 28wt%, DMC 28wt%, EMC 28wt%, VC 1wt%; the sodium carbonate concentration in the aqueous solution is 30wt%; the volume ratio of the aqueous solution to the electrolyte is 1:2.

[0048] The reactor volume is 3.89 m³. 3 The total volume of the oil and water phases is approximately 2.5 m³. 3 The dissolved air pump returns the gas at a speed of 6m / s. 3 / h; head 40m; the micro-nano bubbles are oxygen bubbles, with particle sizes mainly distributed in the range of 100-500nm; the water-to-gas volume ratio of the oil-water mixture flowing through the dissolved air pump and the gas injected through the gas filling pipe is 100:10, and the pressure of the dissolved air tank is 5bar.

[0049] Comparative Example 1

[0050] A method for recovering lithium carbonate from waste lithium-ion battery electrolyte, specifically comprising:

[0051] An electrolyte containing lithium hexafluorophosphate was added to a reaction vessel containing an aqueous solution of sodium carbonate. The mixture was continuously stirred and dispersed to ensure continuous mixing of the oil and aqueous phases. The reaction temperature was 50°C. During the reaction, the precipitate was separated using a filter. After the reaction, the aqueous and oil phases were separated. The reaction endpoint was defined as the absence of substantial precipitate in the reaction system, with a reaction time of approximately 12 hours.

[0052] The concentrations of each substance in the electrolyte are: LiPF6 15wt%, EC 28wt%, DMC 28wt%, EMC 28wt%, VC 1wt%; the sodium carbonate concentration in the aqueous solution is 5wt%; 80L of electrolyte is added per cubic meter of aqueous solution.

[0053] Results Analysis

[0054] The lithium carbonate collected from the filters of each embodiment and comparative example was weighed, and the yield of Li was calculated.

[0055] The results are shown in Table 1 below.

[0056] Table 1. Yield results of the examples and comparative examples

[0057]

[0058] Based on the above analysis, we can conclude that:

[0059] 1. By comparing Example 1 and Comparative Example 1, it can be seen that using micro-nano bubbles is better than not using micro-nano bubbles.

[0060] 2. By comparing Examples 1-3, it can be seen that the more carbonate ions used, the higher the concentration, the higher the temperature, and the smaller the water-to-gas ratio, the higher the lithium carbonate yield and the shorter the reaction time.

[0061] 3. A comparison of Examples 1 and 4-6 shows that the effects of using various micro-nano bubbles are similar, with carbon dioxide micro-nano bubbles showing a slightly better effect. It should be noted that if carbon dioxide is used, the reaction temperature should be higher than 70°C, otherwise the yield will be significantly lower. This differs from the reaction results using a pipeline reactor based on micro-nano bubbles. The advantage of using a pipeline reactor is that the oil-water mixing is better, so the advantage of carbon dioxide micro-nano bubbles is more obvious. In a conventional reactor, it is difficult to achieve sufficient oil-water mixing.

[0062] In addition, this invention has tried adding emulsifiers and found that the advantages of micro-nano bubbles cannot be brought into play after adding emulsifiers. We believe that emulsifiers will form a shell at the oil-water interface, which is not conducive to the full play of the advantages of micro-nano bubbles.

[0063] 4. By comparing Example 1 and Example 7, it can be found that the recovery efficiency is better when the oil-water ratio is higher after adjusting the oil-water ratio. Considering that lithium carbonate is slightly soluble in aqueous solution, reducing the water-oil ratio will increase the precipitation efficiency.

Claims

1. A method for recovering lithium carbonate from waste lithium-ion battery electrolyte, characterized in that, An electrolyte containing lithium hexafluorophosphate is added to a reaction system containing an aqueous solution of soluble carbonates. The mixture is continuously stirred and dispersed to continuously mix the oil and water phases. Micro-nano bubbles are injected from the bottom of the reaction system. During or after the reaction, a precipitate is separated. After the reaction, the aqueous and oil phases are separated. The electrolyte is composed of lithium hexafluorophosphate, EC, DMC, EMC, and VC.

2. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to claim 1, characterized in that, 50-2000L of electrolyte is added to each cubic meter of aqueous solution; the electrolyte contains 1-20wt% lithium hexafluorophosphate.

3. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to claim 1, characterized in that, The reaction system includes a reaction vessel, a filter, a dissolved gas pump, a dissolved gas tank, and a micro / nano bubble generator connected in sequence; the micro / nano bubble generator is located at the bottom of the reaction vessel; the filter is connected to the middle or upper part of the reaction vessel; and a gas supply pipe is connected to the dissolved gas pump.

4. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to claim 3, characterized in that, The volume ratio of the oil-water mixture flowing through the dissolved air pump to the water-gas volume ratio of the gas injected through the gas filling pipe is 100:2-10.

5. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to any one of claims 1-4, characterized in that, The micro-nano bubbles have a particle size of 10 nm to 10 μm.

6. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to claim 5, characterized in that, The particle size of the micro-nano bubbles is 100-500 nm.

7. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to claim 3, characterized in that, The reaction temperature in the reactor ranges from room temperature to 90°C.

8. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to claim 1, characterized in that, The soluble carbonate is sodium carbonate, potassium carbonate, or ammonium carbonate; the ratio of the molar amount of lithium ions to the molar amount of carbonate ions in the soluble carbonate solution is 2:1.1~10; the concentration of the solute in the soluble carbonate solution is 1wt%~30wt%.

9. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to claim 1, characterized in that, The soluble carbonate is sodium carbonate, potassium carbonate, or ammonium carbonate.

10. The method for recovering lithium carbonate from waste lithium-ion battery electrolyte according to claim 1, characterized in that, The micro-nano bubbles are one of the following: air bubbles, carbon dioxide bubbles, nitrogen bubbles, oxygen bubbles, and ozone bubbles.

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