Organic solvent and battery cell recovery method

Abstract

The invention discloses an organic solvent and a battery cell recovery method in the technical field of power batteries. The organic solvent comprises the following components in parts by weight: 20-25 parts of isoparaffin, 10-20 parts of methyl ether acetate, 40-50 parts of methylene chloride, 5-10 parts of a corrosion inhibition aid, 5-10 parts of a volatilization inhibitor and 10-15 parts of an active agent. The battery cell recovery method comprises the following steps: soaking a to-be-recovered battery cell and glue on the surface of the to-be-recovered battery cell by using the organic solvent, and removing the soaked battery cell after the organic solvent completely infiltrates the interior of the glue and the solvent on the surface is completely volatilized. The structural strength of the structural adhesive can be effectively reduced, the shearing force between the structural adhesive and a battery cell is reduced, the structural adhesive is normally stripped from the adhesive, and the dismounting difficulty is reduced; the integrity of the battery cell structure in the battery cell dismounting process is ensured, the battery cell yield in the battery cell recycling process is improved, and the aluminum shell at the bottom of the battery cell is prevented from bulging.

Description

Technical Field

[0001] The present invention belongs to the technical field of power batteries, and more specifically, relates to an organic solvent and a battery cell recycling method. Background Art

[0002] In the current new energy battery technology on the market, the bonding method for modules and boxes is mainly based on structural adhesives and thermal conductive adhesives. Among them, structural adhesives have the characteristics of high shear force and high structural strength, which makes them difficult to remove after curing and has a high cell damage rate.

[0003] At present, the mainstream dismantling method is low-temperature modification. The battery is placed in an environment of about -5-10℃ for more than 48 hours to make the internal structure of the structural adhesive brittle and achieve the dismantling effect. However, in this case, the dismantling of the battery cell requires high operating experience of the personnel. There is still a strong shear force between the bottom of the battery cell and the structural adhesive. During the dismantling process, the battery cell is highly damaged and the yield is low, with a yield of less than 60%.

[0004] The main materials of the battery's structural adhesive are polyol polyurethane and isocyanate, which are organic polymer structures and can be infiltrated and dissolved by low-molecular organic solvents. The current mainstream lipid solvents such as DMF and NMP are toxic to a certain extent, and long-term contact operations will cause certain damage to the human body. Summary of the invention

[0005] The purpose of the present invention is to address the above shortcomings and provide an organic solvent and a battery cell recycling method. By soaking the battery cells and glue with the organic solvent, the structural strength of the structural glue can be effectively reduced to soften it, and the shear force between the structural glue and the battery cells can be reduced, so that they can be normally peeled off from the glue, reducing the difficulty of dismantling; ensuring the integrity of the battery cell structure during battery cell dismantling, improving the battery cell yield during battery cell recycling, and avoiding bulging of the aluminum shell at the bottom of the battery cell.

[0006] To achieve the above object, the present invention is implemented by the following technical solutions: In a first aspect, the present invention provides an organic solvent, which comprises the following components in parts by weight: 20 to 25 parts of isoparaffin, 10 to 20 parts of methyl ether acetate, 40 to 50 parts of methylene chloride, 5 to 10 parts of corrosion inhibitor, 5 to 10 parts of volatilization inhibitor, and 10 to 15 parts of activator.

[0007] The small molecule organic solvent prepared by the above formula has a strong ability to clean lipid organic matter and can effectively reduce the structural strength of the structural adhesive; it also has low toxicity and effectively reduces harm to the human body.

[0008] Preferably, the isoalkane includes isodecane, isododecane, isotridecane or isohexadecane.

[0009] The above-mentioned isoalkanes are highly branched, have a high degree of isomerization, low impurity content, stable quality, contain almost no aromatic hydrocarbons and sulfur, are green and environmentally friendly, have a low freezing point, little odor, low toxicity, good stability, and are easily biodegradable.

[0010] Preferably, the corrosion inhibitor is a pickling corrosion inhibitor, including any one of methyl benzotriazole, anhydrous ethanol or indium hydroxide, preferably methyl benzotriazole.

[0011] Since the solvent will show different pH values ​​due to its own components in the actual application process, the pH of the solvent in the above formula is between 4 and 6, which is a certain acidity. At this time, it is necessary to add a certain amount of hydrochloric acid pickling corrosion inhibitor as a corrosion inhibitor to reduce its corrosive effect on metal materials and reduce damage to the battery cells. Using methyl benzotriazole as a corrosion inhibitor can better protect metal materials and form a more uniform protective film.

[0012] Preferably, the volatility inhibitor is a styrene volatility inhibitor, such as BYK volatility inhibitor commonly used, preferably BYK-S 750.

[0013] In the actual operation process, since the solvent always has a certain volatility under a certain temperature environment, it is necessary to add some substances that inhibit volatility for protection. The present invention uses BYK-S 750 to inhibit volatility, forming a small diaphragm layer in the solvent to reduce the contact between the solvent and the air, so as to achieve the effect of inhibiting volatility; and while reducing the volatility of styrene, it will not affect the interlayer adhesion of the resin, and can effectively reduce the emission of harmful gases while ensuring product quality, protecting the environment and human health.

[0014] Preferably, the active agent is any one of cyclohexanone or ethanol.

[0015] The use of small molecule alcohol and ketone solvents such as cyclohexanone or ethanol can fully mix methylene chloride, methyl ether acetate, and isoparaffins, improve the mixing effect and wetting effect of organic solvents, and achieve full wetting of the structural adhesive of the battery cell.

[0016] In a second aspect, the present invention provides a method for recycling battery cells, which comprises soaking the battery cells to be recycled and the glue on their surface with the organic solvent described in the first aspect, and removing the soaked battery cells after the organic solvent completely permeates the glue and the surface solvent completely evaporates.

[0017] The battery pack body and the surface of the battery cell are mostly made of metal, which is difficult to cut and the sealing inside the body is good. The degumming process by solvent immersion can reduce the difficulty of disassembly. By adding small molecule organic solvents to cover the glue, the solvent is allowed to fully penetrate into the bonding area after standing, and the hydrogen atoms or oxygen atoms in the small molecules are used to destroy the bonding method between the metal and the glue, causing it to dissolve in the solvent. The shear force on the joint surface is reduced, and the metal and glue are easier to separate, achieving the degumming effect on the contact surface of the battery cell, thereby reducing the difficulty of disassembly of the battery cell.

[0018] Preferably, the organic solvent soaking the battery cells to be recycled and the glue on their surfaces comprises: pouring the organic solvent into the battery pack to be processed until the organic solvent covers the bottom of the module of the battery pack and all the glue is immersed.

[0019] This method can ensure that the organic solvent fully covers and submerges all the glue at the bottom of the battery pack module, so that the glue can be fully dissolved by the organic solvent, reducing the shear force between the structural glue and the battery cell, which helps to easily remove the glue in subsequent steps and facilitates the disassembly and recycling of the battery cell.

[0020] Preferably, the organic solvent is poured into the battery pack along a module tank body in a fixed clockwise or counterclockwise direction.

[0021] Pouring the organic solvent along a fixed route can prevent the organic solvent from leaking, make the liquid level of the organic solvent more uniform, and improve the wetting effect of the organic solvent.

[0022] Preferably, when the organic solvent is soaked in the battery cells to be recycled and the glue on their surfaces, the cells are placed in an open and ventilated area or in a closed area equipped with an air circulation purification system and left to stand for more than 48 hours.

[0023] Placing the batteries in an open and ventilated area or in a closed area equipped with an air circulation and purification system can help accelerate the volatilization of surface solvents, reduce harm to the human body and the environment, and reduce the risk of fire and explosion. Leaving the batteries to stand for more than 48 hours can ensure that the organic solvent fully dissolves the glue on the surface of the battery cells, weakening the bonding force between the battery cells and the glue, making it easier to separate and handle them later.

[0024] Preferably, the soaked battery cell is removed using an insulating wedge.

[0025] The battery cells are removed one by one using wedge-shaped tools, which can fit the gaps during the removal process, reduce damage to the surface of the battery cells, and use insulating materials to avoid the risk of electric shock.

[0026] Compared with the prior art, the present invention has the following beneficial effects: The organic solvent described in the present application can destroy the chemical bonds such as NH and CH inside the structural adhesive, dissolve the grease and polar chemical bonds in the structural adhesive in the organic solvent, weaken the internal structural strength, and make the glue structure brittle, which saves time and effort when personnel dismantle the adhesive, and is not easy to damage the material; at the same time, the organic solvent has low toxicity, which effectively reduces the harm to the personnel; The battery cell recycling method described in the present application adds a small molecule organic solvent to cover the structural adhesive of the battery cell and fully infiltrate it into the bonding area, and uses the hydrogen atoms or oxygen atoms in the small molecules to destroy the bonding mode between the metal and the glue, so that they are dissolved in the solvent, thereby reducing the shear force at the bonding surface between the structural adhesive and the battery cell, making it easier for the metal and the structural adhesive to separate, achieving the debonding effect of the battery cell contact surface, thereby reducing the difficulty of disassembling the battery cell; optimizing the industry pain point of bulging of the aluminum shell at the bottom of the battery cell during battery cell recycling, and ensuring the integrity of the battery cell structure during battery cell dismantling. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the surface structure of the metal material of the battery cell and the principle of structural adhesive penetration; Figure 2 This is a comparison chart of shear force changes when degumming using various solvent samples in the degumming verification test described in the embodiment; Figure 3 This is a schematic diagram of the structure of the battery pack described in Example 3; Figure 4 This is a schematic diagram of disassembling a battery cell as described in Example 3.

[0028] In the figure: 1. Battery pack; 2. Battery cell; 3. Module slot; 4. Module; 5. Insulating wedge. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention will be described in more detail below in conjunction with the accompanying drawings and specific examples.

[0030] The battery box and the surface of the battery cell are mostly made of metal. The main materials of the structural adhesive of existing batteries are polyol polyurethane and isocyanate. Since the surface of the metal material has strong tension, the presence of isocyanate is conducive to the infiltration of glue. There are grooves on the surface of the metal material at the microscopic level. The glue will fill the grooves after immersion. After the glue is completely cured, the force is formed to combine the glue and the metal surface together, such as Figure 1 On the other hand, as shown in the following chemical formula: RNCO + HO-R-OH → RNHCOOR + H2O Oxides or small water molecules on the metal surface will form hydrogen bonds with O&H in the glue, increasing the bonding strength between the metal and the glue; therefore, stronger polar bonds and stronger penetration capabilities are needed in the solvent to allow the glue to absorb a large amount of solvent and swell and denature.

[0031] In order to reduce the shear force between the structural adhesive and the battery cell, peel the battery cell from the structural adhesive, optimize the problem of bulging of the aluminum shell at the bottom of the battery cell during battery cell recycling, and ensure the integrity of the battery cell structure during battery cell dismantling, the present invention provides an organic solvent that can effectively reduce the structural strength of the structural adhesive, and a battery cell recycling method using the organic solvent.

[0032] Example 1 This embodiment provides an organic solvent, whose raw materials include: 40 kg of methylene chloride, 10 kg of methyl ether acetate, 20 kg of isododecane, 5 kg of tolutriazole, 5 kg of BYK-S 750, and 10 kg of cyclohexanone.

[0033] The preparation method of the organic solvent comprises the following steps: Mix cyclohexanone and methylene chloride, stir at 120 rpm for 10 minutes, then add methyl ether acetate and isododecane in sequence, continue stirring for 10 minutes, then add methyl benzotriazole and BYK-S 750 in sequence, stir for 120 minutes, remove the solvent and seal for storage.

[0034] Example 2 The present embodiment provides an organic solvent, whose raw materials include: 50 kg of methylene chloride, 20 kg of methyl ether acetate, 25 kg of isodecane, 10 kg of indium hydroxide, 10 kg of BYK-S 750, and 15 kg of ethanol; the organic solvent is prepared by mixing the above raw materials and stirring them evenly.

[0035] The preparation method of the organic solvent comprises the following steps: Mix ethanol and methylene chloride, stir at 120 rpm for 10 minutes, then add methyl ether acetate and isodecane in sequence, continue stirring for 10 minutes, then add methyl benzotriazole and BYK-S 750 in sequence, stir for 120 minutes, remove the solvent and seal it for storage.

[0036] The organic solvent prepared in the above embodiment is subjected to degumming verification, and the verification method is as follows: Experimental materials: aluminum bar, AB glue; Solvent samples: the solvent obtained in Example 1, the solvent obtained in Example 2, DMF (N,N-dimethylformamide), CYC, NMP (N-methylpyrrolidone), alcohol, butanone, and toluene.

[0037] Experimental steps: 1: After the aluminum strips are bonded with AB glue, bake them at 80℃ for 8 hours to allow the glue to cure.

[0038] 2: Take 8 groups of beakers and introduce the above solvent samples in turn, and then put the cured aluminum strips into them one by one and soak them for 24 hours.

[0039] 3: Take out the soaked aluminum strip and measure the shear force.

[0040] The experimental results are shown in Table 1 and Figure 2 shown.

[0041] Table 1 Comparison of the effects of various solvent samples on shear force

[0042] from Figure 2 As can be seen from Table 1, the shear force between AB glue and the aluminum strip gradually decays, and the shear force changes the most when most solvent samples are immersed for 24 hours; the degumming effect of the solvent described in the present invention is significant, and degumming can be achieved after 48 hours, and the solvent described in Example 2 can be degummed within 24 hours.

[0043] Example 3 This embodiment provides a battery cell recycling method for Figure 3 The battery pack shown includes the following steps: The organic solvent prepared in Example 1 is poured into the battery pack 1. The pouring method is to pour the organic solvent clockwise along the module tank 3 until the organic solvent completely covers the bottom of the module 4 and all the structural adhesive is immersed. Place the battery pack with organic solvent in a closed area equipped with an air circulation purification system and let it stand for more than 48 hours; After the surface liquid has completely evaporated, use the insulating wedge 5 to remove the battery cells 2 one by one. Figure 4 shown.

[0044] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Without departing from the scope and technical principles of the described embodiments, many modifications and changes are obvious to those of ordinary skill in the art, and these modifications and changes should also be regarded as the scope of protection of the present invention.

Claims

1. An organic solvent, characterized in that The organic solvent comprises the following components in parts by weight: 20-25 parts of isoparaffin, 10-20 parts of methyl ether acetate, 40-50 parts of methylene chloride, 5-10 parts of corrosion inhibitor, 5-10 parts of volatilization inhibitor, and 10-15 parts of activator.

2. The organic solvent according to claim 1, characterized in that The corrosion inhibitor is a pickling corrosion inhibitor, including any one of toluene triazole, anhydrous ethanol or indium hydroxide.

3. The organic solvent according to claim 1, characterized in that The volatilization inhibitor is a styrene volatilization inhibitor.

4. The organic solvent according to claim 1, characterized in that The active agent is any one of cyclohexanone or ethanol.

5. A battery cell recycling method, characterized in that: The method comprises soaking the battery cell to be recycled and the glue on its surface with the organic solvent described in any one of claims 1 to 4, and removing the soaked battery cell after the organic solvent completely permeates the inside of the glue and the surface solvent completely evaporates.

6. The battery cell recycling method according to claim 5, characterized in that: The organic solvent soaking the battery cells to be recycled and the glue on their surfaces comprises: pouring the organic solvent into the battery pack to be processed until the organic solvent covers the bottom of the module of the battery pack and all the glue is immersed.

7. The battery cell recycling method according to claim 6, characterized in that: The method for pouring the organic solvent is to pour it along the module tank of the battery pack in a fixed clockwise or counterclockwise direction.

8. The battery cell recycling method according to claim 5, characterized in that: When the organic solvent soaks the battery cells to be recycled and the glue on their surfaces, the cells are placed in an open and ventilated area or in a closed area equipped with an air circulation purification system for more than 48 hours.

9. The battery cell recycling method according to claim 5, characterized in that: The soaked battery cells are removed using insulating wedges.

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