WO2023109096A1

WO2023109096A1 - Method for stripping coating layer on metal substrate and use thereof

Info

Publication number: WO2023109096A1
Application number: PCT/CN2022/103295
Authority: WO
Inventors: 孙永明; 陈子和; 陆荣华; 刘书源; 赵建智; 聂瑞超; 冯睿康
Original assignee: 华中科技大学; 武汉蔚能电池资产有限公司
Priority date: 2021-12-17
Filing date: 2022-07-01
Publication date: 2023-06-22
Also published as: CN114628808B; CN114628808A

Abstract

The present invention belongs to the field of coating stripping, and specifically relates to a method for stripping a coating layer on a metal substrate and the use thereof. In the present invention, a metal substrate is soaked in an acid solution for an acid treatment, such that the interface bonding between the metal substrate and the coating layer fails, and the coating layer is then stripped off, so that the metal substrate and the coating layer material can be obtained, wherein the acid solution comprises a chelating agent. According to the present invention, the surface of the metal substrate is damaged in an acidic environment, such that bonding between the metal and the coating layer fails; in addition, at the moment where the interface between the metal substrate and the coating layer is damaged, the chelating agent can chelate dissolved metal ions, and a dense passivation layer is formed on the metal surface, such that continuous dissolution of the metal substrate can be avoided, and the metal substrate can thus be efficiently separated from the coating layer.

Description

A method for stripping coating layer on metal substrate and its application

【Technical field】

The invention belongs to the field of coating stripping, and in particular relates to a method for stripping a coating layer on a metal substrate and an application thereof.

【Background technique】

Coating other materials on metal substrates is widely used in various fields, such as lithium battery technology, the active material and conductive agent are bonded and uniformly coated on aluminum/copper foil through a binder to achieve battery energy stability Output; In the area of metal anti-corrosion, the purpose of metal anti-corrosion is achieved by coating polyurethane, fluororesin, and silicone; in the field of metal high-temperature resistance, the purpose of metal high-temperature resistance is achieved through epoxy resin and liquid rubber coating; in the field of metal insulation , through water-based insulating varnish coating, insulating ceramic coating to achieve the purpose of metal insulation.

However, during use, the coating layer on the outer surface has a limited service life. For example, the performance of the electrode material will decline with the increase in the number of times the battery is used. Anti-corrosion coatings, high-temperature resistant coatings and insulating coatings located on the metal surface are inevitable. Friction and scratching will lead to a decrease in the overall service life of the firmware. Therefore, after the coating layer that has reached the end of its service life is peeled off, the two are further efficiently recycled, which has become a key step for secondary utilization under the premise of environmental protection.

CN107464963 discloses a method of detaching the coating layer from the pole piece through organic solvents such as styrene, acetone, and tetrachlorethylene after the pole piece is crushed. The method utilizes an organic agent with high solubility to the binder to dissolve the binder , so that the active material and conductive carbon black fall off freely, but this type of method is often limited to the electrode coating process. With the continuous improvement of the compactness of the positive electrode material, the degree of infiltration of the organic solvent on the electrode is limited. At present, this method It has been difficult to achieve the desired separation effect.

CN107706481A discloses a method based on hollow microsphere solid-phase recovery lithium battery positive electrode material, wherein the separation process is: soak the lithium ion battery pole piece in alkaline solution for 10-13 hours, and dissolve the copper/aluminum current collector to obtain filter residue of electrode material. This method can effectively separate electrode materials, but just like using acid to directly dissolve copper/aluminum foil, the completely dissolved aluminum ions in the solution will be adsorbed by the conductive carbon black in the electrode material, so it is difficult to be removed in the electrode material recovery stage, reducing the Batch consistency of materials.

CN112442296A discloses a stripping composition containing ethers, esters, amines, alcohols and glycosides to remove coatings from surfaces and methods. However, the method of relaxing or dissolving the coating by a solvent has certain limitations, and it is easy to cause peeling residue due to the difference in the bonding strength/corrosion degree of the coating to the substrate material. As stated in the patent, even under optimal conditions There will be less than 10% of the material that is difficult to peel off. CN113522596A discloses a closed spraying hanger coating physical removal machine, which realizes the drop/peeling of the coating layer by continuously colliding with the metal material coated with the coating layer. Obviously, the method of scraping off with physical violence can be used to a certain extent. Avoiding contamination, but avoiding damage to metal substrates and coating materials and improving stripping efficiency are all major challenges.

CN111313120A discloses a method for recovering cobalt and lithium metal in waste lithium ion batteries, comprising: dismantling waste lithium ion batteries to obtain positive electrodes; The separation liquid of the positive plate is placed in an ultrasonic environment for a period of time, and then the aluminum foil is taken out to obtain a mixed liquid; the mixed liquid is obtained by rotary evaporation to obtain a solid substance, and the solid substance is dried to obtain a lithium-ion battery positive electrode material; after mixing the positive electrode material with a chelating agent The mechanical activation treatment is performed to obtain an activation mixture; the obtained activation mixture is subjected to acid leaching treatment to obtain an enrichment solution containing cobalt and lithium. Although this technical solution uses a chelating agent for treatment, so that the ions are leached and precipitated to allow different elements to be recovered separately, it does not promote the separation of the metal substrate and the coating layer.

To sum up, the prior art still lacks a method for efficiently separating the metal substrate and the coating layer.

【Content of invention】

In view of the above defects or improvement needs of the prior art, the present invention provides a method for peeling off the coating layer on the metal substrate, which uses a chelating agent to form passivation on the surface of the current collector while destroying the interface between the metal substrate and the coating layer in an acidic environment layer, which not only realizes the efficient separation of the electrode material layer but also avoids the continuous dissolution of the metal substrate. The method is reasonable in design, easy to implement, environmentally friendly and low in cost, can be applied to modern industrial production, and has extremely high economic and social benefits.

In order to achieve the above object, according to one aspect of the present invention, a method for peeling off the coating layer on the metal substrate is provided, the metal substrate is soaked in an acid solution for acid treatment, and the interface bonding between the metal substrate and the coating layer is invalidated, Then peel off to obtain the metal base and coating material, wherein the acid solution includes a chelating agent.

Preferably, the chelating agent contains more than two multidentate ligands, and the functional groups of the multidentate ligands include -H ₂ PO ₄ , -H ₂ PO ₃ , -Na ₂ PO ₄ , -K ₂ PO ₄ , -Na One or more of ₂ PO ₃ , -COONa, -COOH, -SH and -SK.

Preferably, the chelating agent contains more than 4 multidentate ligands, and the functional group of the multidentate ligands is one of -H ₂ PO ₄ , -H ₂ PO ₃ , -COOH and -SH.

Preferably, the chelating agent includes phytic acid, hydroxyethylidene-1,1-diphosphonic acid (HEDP), sodium ethylenediaminetetramethylenephosphonate (EDTMPS), ethylenediaminetetraacetic acid (EDTA), amino Trimethylenephosphonic acid (ATMP), diethylenetriaminepentamethylenephosphonic acid (BNHMTPMP), triethylenetetraminehexamethylenephosphonic acid (TETHMP), bis(1,6-hexamethylene)triaminepentamethylene At least one of methylphosphonic acid (BNHMTPMP), polyaminopolyether tetramethylenephosphonic acid (PAPEMP), dimercaptopropanol, sodium gluconate and sodium phytate.

Preferably, the mass proportion of the chelating agent in the acid solution is more than 10%; preferably, the content of the chelating agent is 20-75%.

Preferably, the pH of the acid solution is ≤5.

Preferably, the solvent in the acid solution includes water, methanol, ethanol, ethylene glycol, acetone, dimethylsulfoxide, ethylenediamine, N,N-dimethylformamide, dimethylacetamide, phosphoric acid at least one of triethyl esters.

Preferably, the acid solution is an aqueous solution of phytic acid.

According to another aspect of the present invention, there is provided a kind of application of the method for stripping the coating layer on the metal substrate, the application includes the stripping of the current collector and the electrode material in the pole piece of the decommissioned lithium battery, and the metal polymer coating peeling, peeling of metal insulating coating or peeling of metal corrosion-resistant layer.

As preferably, the stripping of the current collector and the electrode material in the decommissioned lithium battery pole piece in the application includes the following steps:

(1) Disassemble the decommissioned lithium battery to get the decommissioned electrode pole piece, the decommissioned electrode pole piece includes the current collector and the electrode material layer coated on the current collector;

(2) Soak the decommissioned electrode pole pieces in acid solution for acid treatment, so that the bonding between the electrode material layer and the current collector becomes invalid;

(3) Separating the decommissioned electrode pole piece after acid treatment to obtain active material and current collector;

Preferably, the compacted density of the electrode material layer is 1.0-4.0 g/cm ³ , and the composition includes active material, binder and conductive agent;

Preferably, the active material includes ternary nickel-cobalt-manganese material, ternary nickel-cobalt-aluminum material, lithium iron phosphate material, lithium cobalt oxide material, lithium manganate material, lithium nickel manganese oxide material, lithium titanate material, niobic acid One of titanium material, silicon-based material and graphite;

Preferably, the conductive agent comprises one of conductive carbon black, conductive graphite, Super P Li, Ketjen Black and carbon nanotubes;

Preferably, the binder includes polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyvinyl alcohol ( PVA), lithium polyvinyl alcohol (Li-PVA);

Preferably, the current collector is an aluminum current collector or a copper current collector.

Among them, Super P Li conductive carbon black is a carbon black with high porosity, which can form a carbon black network structure at a very low addition amount, and endow the product with excellent electrical conductivity.

The beneficial effects of the present invention have:

(1) The present invention destroys the surface of the metal substrate in an acidic environment, while the hydrogen ion dissolves the metal, the chelating agent will passivate the metal substrate, and will continuously drive the unexposed metal protected by the coating layer to continue to react with the hydrogen ion, Destroy the bonding between the coating layer and the metal material, and finally make the bond between the metal substrate and the coating layer invalid. At the same time, the chelating agent will protect the dissolved metal ions, avoid the continuous dissolution of the metal substrate, and finally achieve high Efficient separation and high quality extraction.

(2) The present invention can complete the separation of the electrode material layer in a short time, and can realize the efficient separation of the metal substrate and the coating layer, especially in the stripping process of the decommissioned lithium battery pole piece, which has more obvious advantages, namely Its good peeling effect is hardly affected by the compaction density of the pole piece, and has a high tolerance.

(3) While the present invention destroys the interface between the metal substrate and the coating layer through an acidic solution, the chelating agent chelates the dissolved metal ions to form a dense passivation film on the surface of the metal substrate to avoid continuous dissolution of the metal substrate. The test results of the generator (ICP) show that the content of impurity metal ions in the solution after stripping is at least 0.000%, which shows that this method effectively eliminates the generation of impurity metal elements during the stripping process, greatly improves the purity of the separated product, and effectively saves the subsequent complicated steps. Purification process.

【Description of drawings】

Fig. 1 is the separation effect diagram of the decommissioned LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode sheet with a compacted density of 3.8g/ ^cm in Example 1;

Fig. 2 is an actual view of the lithium titanate negative electrode sheet with a compacted density of 2.2 g/cm ³ in Example 2 when the electrode material layer is peeled off and the electrode material layer is not dried.

Fig. 3 is the physical figure of aluminum foil and coating layer after direct drying in embodiment 2.

【Detailed ways】

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

Example 1

A pole piece was isolated from a decommissioned single crystal LiNi _0.5 Co _0.2 Mn _0.3 O ₂ battery: its coating layer consisted of 4% PVDF, 4% conductive carbon black and 92% LiNi _0.5 Co _0.2 Mn _0.3 O ₂ and consisted of PVDF Bonded on aluminum foil, the characterized compaction density is 3.8g/cm ³ . Soak it in an aqueous solution with phytic acid content of 75%, 50%, 35%, and 10% at 25°C for 60 seconds, and then stir the solution at 60r/min. After the coating layer and the current collector are separated, they are washed with water for 60 The product was obtained by drying at °C for 1 hour, and the separation results are shown in Table 1.

Table 1 Example 1 separation result table

植酸质量比Phytic acid mass ratio	10％10%	35％35%	50％50%	75％75%
剥离时长Stripping time	30分17秒30 minutes and 17 seconds	15分22秒15 minutes and 22 seconds	7分20秒7 minutes 20 seconds	5分18秒5 minutes and 18 seconds
溶液中铝含量Aluminum content in solution	0.000％0.000%	0.000％0.000%	0.006％0.006%	0.012％0.012%
涂覆层剥离率Coating Peeling Rate	98.65％98.65%	99.73％99.73%	99.98％99.98%	99.98％99.98%
集流体剥离率Current collector stripping rate	100％100%	100％100%	99.99％99.99%	99.97％99.97%

It can be seen from Table 1 that the decommissioning single crystal LiNi _0.5 Co _0.2 Mn _0.3 O ₂ pole piece coating layer and aluminum metal peeling time shortens with the solution acidity (phytic acid content) increases, when the phytic acid content is 75wt%, to achieve 99.98% coating The peeling of the coating only takes 5 minutes and 18 seconds, but the low acidity will cause a small amount of aluminum metal to dissolve, but it meets the requirements of industrial applications. In general, 35% phytic acid separation effect is ideal.

Fig. 1 is a separation effect diagram of the decommissioned LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode sheet in Example 1.

It can be seen from Figure 1 that the decommissioned single crystal LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode piece can be soaked in an aqueous solution with a phytic acid content of 75% for 5 minutes and 18 seconds to complete the peeling of 99.97% of the aluminum foil and 99.98% of the coating layer. Both maintained good integrity after drying.

The surface of the aluminum foil was smooth and clean, and the electrode material layer was successfully peeled off in large flakes, with a peeling rate of 99.98%. Tested by an inductively coupled plasma spectrometer, the Al content in the electrode material layer is only 0.012%.

Example 2

Disassemble the decommissioned lithium iron phosphate battery, separate the lithium titanate negative electrode sheet with a compacted density of 2.2g/cm ³ , soak it in 50% hydroxyethylidene-1,1-diphosphonic acid at 25°C (HEDP), polyamino polyether tetramethylene phosphonic acid (PAPEMP), bis (1,6-hexamethylene) triamine pentamethylene phosphonic acid (BNHMTPMP) water/ethanol mixed solution (v/v= In 1), adjust the Ph to 1.0 with sulfuric acid, then stir the solution at 100r/min for 2 minutes at room temperature, wash the stripped current collector and electrode material layer with water, and dry at 80°C for 1 hour to obtain the product. The results are as follows Table 2 shows.

Table 2 Example 2 separation result table

HEDP, PAPEMP, BNHMTPMP, and phytic acid molecules have 2, 4, 5, and 6 chelating ligands, respectively. From Table 2, it can be seen that the decommissioned lithium iron phosphate pole piece is soaked in different chelating agent acid solutions with a pH of 1.0, and the chelating ligands The more complex ligands, the poorer the chelating ability, and more metal ions will be dissolved in the solution, but the faster the stripping process will be. Of course, even the less effective HEDP still has some peeling effect.

Fig. 2 is an actual view of the lithium titanate negative electrode sheet with a compacted density of 2.2 g/cm ³ in Example 2 when the electrode material layer is peeled off and the electrode material layer is not dried. After stirring, the undried electrode material layer is peeled off, which has a good integrity, and its mechanical strength is not broken when it is taken with tweezers. The undried electrode material layer peeled off from the decommissioned pole piece has better integrity and mechanical strength.

Fig. 3 is the physical picture of the aluminum foil and the coating layer after direct drying without stirring in Example 2. Due to the failure of the bond and the volume shrinkage during the drying process, the electrode material layer can be naturally detached after drying.

Example 3

Soak the steel with polyurethane coating as anti-corrosion coating to 10°C, hydrochloric acid and acetic acid with pH of 1.0, 1.5 and 2.0 respectively for 20% ethylenediaminetetraacetic acid (EDTA), 20% sodium phytate and 5% phytic acid In the mixed aqueous solution, after the surface of the coated layer has obvious wrinkles, it is washed with water and dried. The peeling results after drying are shown in Table 3 below.

Table 3 Example 3 separation result table

It can be seen from Tables 2 and 3 that since the anti-corrosion coating is relatively dense, the peeling of the anti-corrosion coating takes longer than the peeling of the coating layer in the pole piece, and a higher pH helps to shorten the separation time.

Comparative Example 1

The decommissioned single-crystal LiNi _0.5 Co _0.2 Mn _0.3 O ₂ battery was disassembled, and the positive electrode sheet with a compacted density of 3.8 g/cm ³ was separated and soaked in N-methylpyrrolidone (NMP) solution at 25 °C for 1 hour. Subsequently, the solution was stirred at 60 r/min, and there was no obvious observation of the falling off of the electrode material.

Comparative Example 2

The decommissioned single-crystal LiNi _0.5 Co _0.2 Mn _0.3 O ₂ battery was disassembled, and the positive electrode sheet with a compacted density of 3.8 g/cm ³ was separated and soaked in water at 25 °C for 1 hour, and then the solution was stirred at 60 r/min. The exfoliation of the electrode material was clearly observed.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims

A method for peeling off a coating layer on a metal substrate, which is characterized in that the metal substrate is soaked in an acid solution for acid treatment to make the interface bonding between the metal substrate and the coating layer invalid, and then peeled off to obtain the metal substrate and the coating layer. The coating layer material, wherein the acid solution includes a chelating agent.
The method according to claim 1, wherein the chelating agent contains more than two multidentate ligands, and the functional groups of the multidentate ligands include -H 2 PO 4 , -H 2 PO 3 , -Na 2 PO 4 , one or more of -K 2 PO 4 , -Na 2 PO 3 , -COONa, -COOH, -SH and -SK.
The method according to claim 1, wherein the chelating agent contains more than 4 multidentate ligands, and the functional groups of the multidentate ligands are -H 2 PO 4 , -H 2 PO 3 , -COOH and - One of the SH.
The method according to claim 2 or 3, wherein the chelating agent comprises phytic acid, hydroxyethylidene-1,1-diphosphonic acid, sodium ethylenediamine tetramethylene phosphonate, ethylenediamine tetra Acetic acid, aminotrimethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, triethylenetetraminehexamethylenephosphonic acid, bis(1,6-hexamethylene)triaminepentamethylenephosphonic acid, poly At least one of amino polyether tetramethylene phosphonic acid, dimercaptopropanol, sodium gluconate and sodium phytate.
The method according to claim 2 or 3, characterized in that, the mass ratio of the chelating agent in the acid solution is more than 10%; preferably, the content of the chelating agent is 20-75%.
The method according to claim 1, characterized in that the pH of the acid solution is ≤5.
The method according to claim 2, wherein the solvent in the acid solution comprises water, methanol, ethanol, ethylene glycol, acetone, dimethylsulfoxide, ethylenediamine, N,N-dimethyl At least one of formamide, dimethylacetamide, and triethyl phosphate.
The method according to claim 1, wherein the acid solution is an aqueous solution of phytic acid.
According to the application of the method for peeling off the coating layer on the metal substrate according to any one of claims 1-8, it is characterized in that the application includes the stripping of current collectors and electrode materials in the pole pieces of decommissioned lithium batteries, metal polymer coating Layer peeling, peeling of metal insulating coating or peeling of metal corrosion-resistant layer.
The application according to claim 9, wherein the stripping of the current collector and the electrode material in the decommissioned lithium battery pole piece in the application comprises the following steps:

(1) Disassemble the decommissioned lithium battery to get the decommissioned electrode pole piece, the decommissioned electrode pole piece includes the current collector and the electrode material layer coated on the current collector;

(2) Soak the decommissioned electrode pole pieces in acid solution for acid treatment, so that the bonding between the electrode material layer and the current collector becomes invalid;

(3) Separating the decommissioned electrode pole piece after acid treatment to obtain active material and current collector;

Preferably, the electrode material layer has a compacted density of 1.0-4.0 g/cm 3 , including active material, binder and conductive agent;

Preferably, the active material includes ternary nickel-cobalt-manganese material, ternary nickel-cobalt-aluminum material, lithium iron phosphate material, lithium cobalt oxide material, lithium manganate material, lithium nickel manganese oxide material, lithium titanate material, niobic acid One of titanium material, silicon-based material and graphite;

Preferably, the conductive agent comprises one of conductive carbon black, conductive graphite, Super P Li, Ketjen Black and carbon nanotubes;

Preferably, the binder includes polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polyvinyl alcohol, lithiated polyvinyl alcohol;

Preferably, the current collector is an aluminum current collector or a copper current collector.