Efficient and environmentally friendly lithium ion battery recycling process

Abstract

The application discloses a kind of efficient environmental protection lithium ion battery recycling process, it is related to lithium battery recycling processing technical field, including the following steps: (1) after shelling lithium battery is mixed with dry ice, under inert gas, after centrifugation, electrolyte is obtained;(2) in electrolyte is placed in airtight container, after adding hydroxypropyl methyl cellulose and stirring uniformly, then adding sodium alginate solution, guar gum is stirred uniformly, heating and keeping warm to obtain electrolyte gel, subsequently electrolyte gel is placed in liquid nitrogen and frozen;(3) in frozen electrolyte gel, add calcium chloride solution, after standing, reduce pressure heating, after keeping warm and stirring, gel precipitate is obtained;(4) gel precipitate is mixed with water and dispersed, filter, in filtrate, add sodium carbonate, after stirring uniformly, filter, obtain treated electrolyte, the electrolyte in lithium battery is recycled, reduce the emission of toxic gas or toxic substance in recycling process, realize harmless treatment.

Description

Technical Field

[0001] This invention relates to the field of battery recycling technology, and in particular to a highly efficient and environmentally friendly lithium-ion battery recycling process. Background Technology

[0002] With the development of new energy vehicles, the lithium battery industry has developed rapidly. However, the limited lifespan of these vehicles inevitably generates a large number of waste lithium batteries. These waste lithium batteries pose serious safety hazards; if not properly disposed of, they can harm the surrounding environment and then affect nearby organisms and humans, negatively impacting the ecological and social environment. Waste lithium batteries are rich in precious metals such as cobalt (Co), copper (Cu), lithium (Li), aluminum (Al), and iron (Fe), which can alleviate the current resource shortage. Rational and efficient battery recycling technology is conducive to the sustainable development of lithium batteries. Recycling lithium batteries can reduce their pollution to the environment and is one way to promote green and environmentally friendly practices and achieve resource recycling.

[0003] The main components of lithium-ion batteries are: positive electrode material, negative electrode material, separator, electrolyte, and casing. Currently, lithium-ion battery recycling technologies can be categorized into pyrometallurgical, hydrometallurgical, and biological methods. Pyrometallurgical methods involve the volatilization or combustion of the organic solvents in the electrolyte into water vapor and carbon dioxide. Hydrometallurgical methods utilize supercritical carbon dioxide extraction or alkaline absorption. Biological methods utilize microorganisms to convert useful components into soluble compounds and selectively separate them. However, none of these methods consider the recycling of the electrolyte. Electrolytes contain toxic and harmful substances and are highly susceptible to side reactions in the natural environment, causing secondary pollution. Therefore, their recycling and disposal are crucial. For example, lithium salts in the electrolyte can undergo hydrolysis, decomposition, and combustion reactions in the environment, producing fluorine, arsenic, and phosphorus-containing compounds, causing fluorine, arsenic, and phosphorus pollution. Organic solvents, through hydrolysis, combustion, and decomposition, generate small-molecule organic compounds such as formaldehyde, methanol, acetaldehyde, ethanol, and formic acid, which, when dissolved in water, cause water pollution. Therefore, the purpose of this invention is to provide a novel method for recycling and treating lithium-ion battery electrolytes. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a highly efficient and environmentally friendly lithium-ion battery recycling process, especially for recycling the electrolyte in lithium batteries, reducing the emission of toxic gases or substances during the recycling process, and achieving harmless treatment.

[0005] The present invention solves the above-mentioned technical problems through the following technical means:

[0006] A highly efficient and environmentally friendly lithium-ion battery recycling process includes the following steps:

[0007] (1) The lithium battery after shell removal is mixed with dry ice, crushed under inert gas, and centrifuged to obtain electrolyte;

[0008] (2) Place the electrolyte in a sealed container, add hydroxypropyl methylcellulose and stir evenly, then add sodium alginate solution and guar gum and stir evenly. Heat and keep warm to obtain electrolyte gel, and then place the electrolyte gel in liquid nitrogen to freeze.

[0009] (3) Add calcium chloride solution to the frozen electrolyte gel, let it stand, heat under reduced pressure, keep warm and stir to obtain gel precipitate;

[0010] (4) Mix and disperse the gel precipitate with water, filter, add sodium carbonate to the filtrate, stir evenly and filter to obtain the treated electrolyte.

[0011] After removing the positive and negative electrodes and the casing, the electrolyte in a lithium battery is cooled and frozen using dry ice. This, along with an inert gas, prevents reactions that could occur if the internal electrolyte is crushed, thus avoiding potential hazards. It also prevents the introduction of new substances that could come into contact with highly reactive lithium hexafluorophosphate or organic matter, generating highly toxic hydrofluoric acid gas or organic vapors. After centrifuging the lithium battery, the dry ice evaporates, collecting a high-purity electrolyte. This electrolyte, along with hydroxypropyl methylcellulose and sodium alginate, is heated and kept at a constant temperature in a sealed space. This forms a gel that encapsulates the phosphorus pentafluoride generated from lithium hexafluorophosphate and maintains close contact with the sodium alginate, preventing and slowing its hydrolysis into hydrogen fluoride gas. This reduces the emission of toxic gases, which are then centrally processed in the next stage. The gel was then frozen in liquid nitrogen to solidify it, which was then added directly to a calcium chloride solution. Calcium ions reacted with sodium alginate and guar gum to form a calcium alginate gel. Simultaneously, after static cooling and heating under reduced pressure, fluoride ions detached from the gel and reacted with calcium ions within the gel to form calcium fluoride precipitate. Furthermore, the hydrogen fluoride gas, after static cooling and reduced pressure, completely reacted with the calcium ions, resulting in no hydrogen fluoride gas in the volatilized gas, further reducing the emission of toxic gases during the recovery process. The remaining gases consisted entirely of volatile organic solvents, which were subsequently recovered through spraying for secondary treatment. After treatment, the gel precipitate contained no volatile gases. After dispersion with water, the calcium fluoride was filtered off, yielding a lithium-containing solution. This solution reacted with sodium carbonate to form lithium carbonate precipitate, which was then recovered for further processing.

[0012] Furthermore, the mass ratio of the electrolyte to hydroxypropyl methylcellulose is 1:(0.5-1), and the gelation temperature of the hydroxypropyl methylcellulose is 50-60℃.

[0013] The optimal gelation temperature for hydroxypropyl methylcellulose is 50-60℃. Excessive temperature can cause the electrolyte to decompose before gelation, resulting in the volatilization of toxic gases.

[0014] Furthermore, the mass ratio of the electrolyte to sodium alginate solution and guar gum is 1:(1-1.2):0.1, and the mass ratio of the electrolyte to calcium chloride solution is 1:(2-3).

[0015] Furthermore, the concentration of the sodium alginate solution is 45-55 wt%, and the concentration of the calcium chloride solution is 10-15 wt%.

[0016] Furthermore, the mass ratio of the electrolyte to sodium carbonate is 1:0.5.

[0017] Furthermore, in step (2), after adding sodium alginate solution, heat to 50-60℃ and keep warm for 30-40 minutes.

[0018] Furthermore, in step (3), after standing for 10-20 minutes, the pressure is reduced to 30-40 kPa, heated to 70-90°C, and stirred for 1-2 hours.

[0019] Furthermore, in step (4), after the gel precipitate is mixed with water and dispersed and filtered, the filtrate is heated to 75-80°C and stirred for 20-30 minutes. Then, a saturated sodium carbonate solution made of sodium carbonate is added to the filtrate.

[0020] Beneficial effects:

[0021] This invention uses sodium alginate and hydroxypropyl methylcellulose gel to treat the electrolyte, reducing the emission of toxic gases or toxic substances such as hydrogen fluoride during the recycling process, reducing harm to the human body, reducing equipment stress, saving costs, and achieving harmless treatment. The prepared calcium fluoride or lithium carbonate is then subjected to secondary treatment to recover fluoride and lithium ions, achieving green circular development. Detailed Implementation

[0022] The present invention will be described in detail below with reference to the embodiments:

[0023] Example 1:

[0024] (1) Mix the decased lithium battery with dry ice at a mass ratio of 1:0.3, crush it under inert gas, centrifuge it to obtain electrolyte, and weigh the electrolyte, 200g.

[0025] (2) Place the electrolyte in a sealed container, add 100g of hydroxypropyl methylcellulose with a gel temperature of about 50°C, stir evenly, then add 200g of sodium alginate solution with a concentration of 45wt% and 20g of guar gum, stir evenly, heat to 50°C, keep warm for 40min, and let stand to cool to obtain electrolyte gel. Then place the electrolyte gel in liquid nitrogen to freeze.

[0026] (3) Add 400g of 10wt% calcium chloride solution to the frozen electrolyte gel, let stand for 10min, reduce the pressure to 30Kpa, heat to 70℃, keep warm and stir for 1h to obtain gel precipitation.

[0027] (4) The gel precipitate was mixed and dispersed with water, filtered to obtain calcium fluoride precipitate, the filtrate was heated to 75°C, stirred for 20 min and then 100 g of sodium carbonate was added. After stirring evenly, the filtrate was filtered to obtain lithium carbonate. The remaining solution was the electrolyte after treatment.

[0028] Example 2:

[0029] (1) Mix the decased lithium battery with dry ice at a mass ratio of 1:0.3, crush it under inert gas, centrifuge it to obtain electrolyte, and weigh the electrolyte, 200g.

[0030] (2) Place the electrolyte in a sealed container, add 160g of hydroxypropyl methylcellulose with a gel temperature of about 60°C, stir evenly, then add 240g of sodium alginate solution with a concentration of 50wt% and 20g of guar gum, stir evenly, heat to 60°C, keep warm for 35min, and let stand to cool to obtain electrolyte gel. Then place the electrolyte gel in liquid nitrogen to freeze.

[0031] (3) Add 500g of 12wt% calcium chloride solution to the frozen electrolyte gel, let stand for 15min, reduce the pressure to 35Kpa, heat to 80℃, keep warm and stir for 1.5h to obtain gel precipitation.

[0032] (4) Mix and disperse the gel precipitate with water, filter, heat the filtrate to 75°C, stir for 25 min, add 100g of sodium carbonate, stir evenly, and filter to obtain the treated electrolyte.

[0033] Example 3:

[0034] (1) Mix the decased lithium battery with dry ice at a mass ratio of 1:0.3, crush it under inert gas, centrifuge it to obtain electrolyte, and weigh the electrolyte, 200g.

[0035] (2) Place the electrolyte in a sealed container, add 200g of hydroxypropyl methylcellulose with a gel temperature of about 50°C, stir evenly, then add 200g of sodium alginate solution with a concentration of 50wt% and 20g of guar gum, stir evenly, heat to 50°C, keep warm for 40min, and let stand to cool to obtain electrolyte gel. Then place the electrolyte gel in liquid nitrogen to freeze.

[0036] (3) Add 600g of 15wt% calcium chloride solution to the frozen electrolyte gel, let stand for 20min, reduce the pressure to 30Kpa, heat to 90℃, keep warm and stir for 2h to obtain gel precipitate.

[0037] (4) Mix and disperse the gel precipitate with water, filter, heat the filtrate to 80°C, stir for 20 minutes, add 100g of sodium carbonate, stir evenly, and filter to obtain the treated electrolyte.

[0038] Comparative Example 1:

[0039] This comparative example is compared with Example 1, the only difference being that the gelation temperature of the hydroxypropyl methylcellulose selected in step (2) is 90°C, and the specific steps are as follows:

[0040] Step (1) is the same as in Example 1;

[0041] (2) Place the electrolyte in a sealed container, add 100g of hydroxypropyl methylcellulose with a gel temperature of about 90°C, stir evenly, then add 200g of sodium alginate solution with a concentration of 45wt% and 20g of guar gum, stir evenly, heat to 90°C, keep warm for 40min, and let stand to cool to obtain electrolyte gel. Then place the electrolyte gel in liquid nitrogen to freeze.

[0042] Steps (3) and (4) are the same as in Example 1.

[0043] Comparative Example 2:

[0044] This comparative example is compared with Example 1, the only difference being that hydroxypropyl methylcellulose is not used. The specific steps are as follows:

[0045] (1) Mix the decased lithium battery with dry ice at a mass ratio of 1:0.3, crush it under inert gas, centrifuge it to obtain electrolyte, and weigh the electrolyte, 200g.

[0046] (2) Place the electrolyte in a sealed container, add 200g of 45wt% sodium alginate solution and 20g of guar gum, stir well, let stand and cool, and then freeze in liquid nitrogen.

[0047] (3) Add 400g of 10wt% calcium chloride solution to the frozen electrolyte gel, let stand for 10min, reduce the pressure to 30Kpa, heat to 70℃, keep warm and stir for 1h to obtain gel precipitation.

[0048] (4) Mix and disperse the gel precipitate with water, filter, heat the filtrate to 75°C, stir for 20 minutes, add 100g of sodium carbonate, stir evenly, and filter to obtain the treated electrolyte.

[0049] Comparative Example 3:

[0050] This comparative example is compared with Example 1, and its specific steps are as follows:

[0051] Step (1) is the same as in Example 1;

[0052] (2) Pour the electrolyte into a sealed container, add 20g of water, reduce the pressure to 1KPa, heat to 100℃, keep warm and stir for 1h, and at the same time pass the vaporized gas into a 10wt% calcium chloride solution through a pipe to obtain calcium fluoride precipitate and a solution containing organic solvent.

[0053] (3) After filtering the solution, add 100g of sodium carbonate, stir evenly, and then filter to obtain the treated electrolyte.

[0054] During the experiments of Example 1, Comparative Examples 1 and 2, an external pipe was connected to a sealed container, and a 10 wt% calcium chloride solution was passed through the pipe. Finally, the amount of hydrogen fluoride vaporization and escape was characterized by measuring the mass of calcium fluoride precipitate. For Comparative Example 3, the mass of calcium fluoride was directly weighed. The data obtained are shown in Table 1:

[0055] Table 1

[0056] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Mass of calcium fluoride (g) 0.01 4.6 5.7 9.52

[0057] The calcium fluoride precipitates prepared in step (4) of Example 1 and Comparative Example 1, and the calcium fluoride precipitates prepared in step (3) of Comparative Example 2 were weighed. The data obtained are shown in Table 2.

[0058] Table 2

[0059] Example 1 Comparative Example 1 Comparative Example 2 Mass of calcium fluoride (g) 9.87 5.06 3.95

[0060] According to the data in Tables 1 and 2, Example 1 showed a significantly lower amount of hydrogen fluoride gas emitted during electrolyte treatment. After combining with calcium ions, only 0.13g of calcium fluoride precipitate was formed, with most of the hydrogen fluoride precipitating within the gel. This significantly reduced the emission of toxic gases and achieved harmless treatment. In contrast, Comparative Examples 1 and 2, due to the use of hydroxypropyl methylcellulose (HPMC) with a higher gelation temperature or the absence of HPMC, could not be directly treated within the gel, resulting in the emission of large amounts of hydrogen fluoride gas. This required external treatment equipment, increasing treatment costs and increasing the risk of hydrogen fluoride gas leakage, which could harm worker health. Comparative Example 3 used a traditional method to directly vaporize the hydrogen fluoride, requiring high levels of equipment sealing and pressure resistance; the greater the pressure reduction, the more resources were consumed.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A highly efficient and environmentally friendly lithium-ion battery recycling process, characterized in that, Includes the following steps: (1) The lithium battery after shell removal is mixed with dry ice, crushed under inert gas, and centrifuged to obtain electrolyte; (2) Place the electrolyte in a sealed container, add hydroxypropyl methylcellulose and stir evenly, then add sodium alginate solution and guar gum and stir evenly. Heat and keep warm to obtain electrolyte gel, and then place the electrolyte gel in liquid nitrogen to freeze. (3) Add calcium chloride solution to the frozen electrolyte gel, let it stand, heat under reduced pressure, keep warm and stir to obtain gel precipitate; (4) Mix and disperse the gel precipitate with water, filter, add sodium carbonate to the filtrate, stir evenly and filter to obtain the treated electrolyte.

2. The efficient and environmentally friendly lithium-ion battery recycling process according to claim 1, characterized in that, The mass ratio of the electrolyte to hydroxypropyl methylcellulose is 1:(0.5-1), and the gel temperature of the hydroxypropyl methylcellulose is 50-60℃.

3. The efficient and environmentally friendly lithium-ion battery recycling process according to claim 2, characterized in that, The mass ratio of the electrolyte to sodium alginate solution and guar gum is 1:(1-1.2):0.1, and the mass ratio of the electrolyte to calcium chloride solution is 1:(2-3).

4. The efficient and environmentally friendly lithium-ion battery recycling process according to claim 3, characterized in that, The concentration of the sodium alginate solution is 45-55 wt%, and the concentration of the calcium chloride solution is 10-15 wt%.

5. The efficient and environmentally friendly lithium-ion battery recycling process according to claim 3, characterized in that, The mass ratio of the electrolyte to sodium carbonate is 1:0.

5.

6. The efficient and environmentally friendly lithium-ion battery recycling process according to claim 5, characterized in that, In step (2), after adding sodium alginate solution, heat to 50-60℃ and keep warm for 30-40 minutes.

7. The efficient and environmentally friendly lithium-ion battery recycling process according to claim 6, characterized in that, In step (3), after standing for 10-20 minutes, the pressure is reduced to 30-40 kPa, heated to 70-90°C, and stirred for 1-2 hours.

8. The efficient and environmentally friendly lithium-ion battery recycling process according to claim 1, characterized in that, In step (4), after the gel precipitate is mixed with water and dispersed and filtered, the filtrate is heated to 75-80℃ and stirred for 20-30 minutes. Then, a saturated sodium carbonate solution made of sodium carbonate is added to the filtrate.