Method for preparing single-sided pole piece for button cell by using double-sided coated pole piece

Abstract

The invention belongs to the field of preparation of a single-sided pole piece for a button cell, and particularly relates to a method for preparing the single-sided pole piece for the button cell by using a double-sided coated pole piece. The method comprises the following steps: (1) bonding a double-sided adhesive tape on the surface of a substrate, and bonding the surface of a coating layer on one side of a double-sided coated pole piece on the double-sided adhesive tape of the substrate; and (2) placing the double-sided coated pole piece and the substrate up and down, pre-stripping the coating layer and the current collector layer on the double-sided adhesive side of the pole piece, uncovering the free end of the pre-stripped pole piece from the substrate, and separating the coating layer from the current collector to form a single-sided pole piece. On one hand, damage to the pole piece in the stripping process is reduced, the qualified rate is increased, on the other hand, the treatment efficiency is also improved, and the treatment time is reduced to be within 2 min from 40 min or above (the adhesive tape repeated stripping mode) or above.

Description

Technical Field

[0001] The invention belongs to the field of preparation of single-sided pole pieces for buckle switches, and in particular relates to a method for preparing the single-sided pole piece for buckle switches by utilizing a double-sided coated pole piece. Background Art

[0002] Lithium-ion batteries are widely used in mobile electronic devices, electric vehicles, backup energy storage, smart grids, etc. As an important analytical method in the development of lithium-ion batteries, button cell testing plays a vital role in raw material performance evaluation, new material development, process optimization, battery design evaluation, cycle life testing, temperature adaptability testing, and safety testing.

[0003] In some cases, the samples used to make buckle batteries are usually taken from formed batteries or double-sided coated pole pieces, and the pole pieces obtained from the disassembly of formed battery cells are also double-sided coated. In order to make the current collector (usually foil) in the pole piece fully contact with the buckle battery shell, the battery material on one side of the pole piece needs to be wiped off with a solvent or repeatedly peeled off with tape during the sample pre-treatment stage until the foil of the double-sided coated battery pole piece is exposed.

[0004] Since the material of the electrode is relatively soft, the above two common processing methods have the following problems: the repeated peeling method using tape can easily cause the electrode to bend, and the number of repeated peelings is large (more obvious when the coating layer has high cohesion), and such repeated peeling methods often make it difficult to clean and properly handle the battery materials. Once the foil leaks out, it cannot be peeled off further, otherwise the tape will adhere to the current collector and damage the electrode due to the peeling action. In addition, the electrode resistance will be increased due to the residual glue. The solvent erasing method can easily damage the electrode during the erasing process, causing the surface of the electrode to be tested to be subjected to physical friction, the solvent to leak sideways or penetrate into the surface to be tested, and the adhesive of the coating layer of the surface to be tested to swell or dissolve under the action of the solvent. During the erasing process, the coating layer of the surface to be tested is easily damaged or even falls off from the current collector, making the surface to be tested unusable.

[0005] The Chinese invention patent with the authorization announcement date of May 3, 2024 and the authorization announcement number of CN 113777491 B discloses a method for detecting the gram capacity of failed lithium-ion battery negative electrode materials. After disassembling the battery and removing the negative electrode sheet, the negative electrode sheet is fixed, and a wiping solvent is dripped on the non-edge part (wiping position) of the negative electrode sheet and wiped until a clean current collector is exposed, thereby obtaining a single-sided negative electrode sheet at the wiping position and double-sided negative electrode sheets around. The electrode sheet is punched out at the wiping position to obtain a single-sided negative electrode unit sheet. This method essentially erases the electrode material in the center area and then punches and produces sheets. The production efficiency is low, and the adaptability to the electrode sheets with strong adhesion of some coating layers is poor. Wiping is laborious and easy to damage the electrode sheets. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a single-sided electrode for buckle connection by using a double-sided coated electrode, so as to solve the problems of low processing efficiency and easy damage to the electrode in the existing method.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: A method for preparing a single-sided pole piece for buckle current by using a double-sided coated pole piece, comprising the following steps: (1) bonding double-sided tape on the surface of the substrate, bonding the coating surface on one side of the double-sided coated electrode to the double-sided tape of the substrate; (2) The double-sided coated electrode and substrate are placed up and down, the coating layer and the current collector layer on the double-sided adhesive side of the electrode are pre-peeled off, and the free end of the pre-peeled electrode is lifted off from the substrate, and the coating layer and the current collector are separated to form a single-sided electrode.

[0008] The present invention is an improved invention, in which the pole piece coating layer is integrally bonded to the substrate with the help of double-sided tape, and the substrate applies a downward force to the pole piece coating layer. By pre-stripping the coating layer and the current collector layer, there is no adhesion at the pre-stripping position, and the subsequent lifting process is completed in one go, and the single-side coating of the double-sided coated pole piece is stripped off at one time. On the one hand, the damage to the pole piece during the stripping process is reduced, and the qualified rate is improved. On the other hand, the processing efficiency is also improved, and the processing time is reduced from more than 40 minutes (repeated tape stripping method) to less than 2 minutes.

[0009] This method also enhances the compatibility of the double-sided electrode sheet preparation method, and is still applicable to electrodes with strong cohesion, while the existing wiping method or single-sided tape stripping method requires multiple wiping or stripping, and the processing effect is poor. At the same time, the production of single-sided electrode sheets can be completed by one stripping, which also avoids damage to the electrode sheets caused by multiple wiping or stripping.

[0010] Preferably, the length of the pre-stripping in step (2) is ≥1 mm. There should be no adhesion at the pre-stripping site, so as to facilitate the overall stripping of the coating layer and reduce the damage to the electrode during the stripping process.

[0011] Preferably, the lifting in step (2) is performed at an angle not greater than 90°. Controlling the lifting angle within this range can further ensure that the pole piece is flat and the structure is not damaged.

[0012] Preferably, in step (1), when the double-sided adhesive is bonded to the surface of the coating layer, the width of the double-sided adhesive is within the width range of the corresponding coating layer on the electrode; the length of the double-sided adhesive covers the length range of the corresponding coating layer on the electrode. At this time, the double-sided adhesive cannot be bonded to the edge of the electrode, and the area of ​​the electrode in the peeling area is generally larger than the area of ​​the double-sided adhesive, thereby reducing the damage to the electrode.

[0013] Preferably, after one side of the double-sided adhesive tape is bonded to the substrate and the other side is bonded to the surface of the coating layer, a roller is used to roll the bonding area. Rolling with a roller can eliminate air residue at the bonding position to ensure a firm bond.

[0014] Further preferably, the width of the roller is greater than the width of the double-sided tape; and the rolling pressure of the roller is 1-10 kgf.

[0015] Preferably, the peeling strength of the double-sided adhesive to the substrate and the electrode coating layer after bonding is not less than 15N / 25mm.

[0016] Preferably, if there is a coating layer residue after the separation in step (2), the coating layer residue is wiped off with a solvent. The solvent here can generally be selected from one or more of deionized water, anhydrous ethanol, and N-methylpyrrolidone.

[0017] Generally speaking, the leakage area of ​​the double-sided coated battery pole piece foil after single-sided treatment is ≥70%. In most cases, only a small amount of coating layer remains or no coating layer remains. For the case of a small amount of coating layer remaining, the coating layer residue is easy to clean. After solvent wiping and cleaning, the leakage area of ​​the foil is ≥95%. This method can effectively shorten the pre-processing time even for pole pieces with strong cohesion and improve the success rate of the buckle test, which has high application value.

[0018] Further preferably, the double-sided coated electrode is obtained by disassembling the battery cell, and the erased electrode is immersed in an organic solvent, and then dried and stamped to obtain an electrode that can be used to make a buckle. For the double-sided coated electrode obtained by disassembling the battery, this method can be used to remove the lithium salt and residual electrolyte on the surface of the electrode, and finally obtain a clean single-sided electrode without glue or other foreign matter residue.

[0019] More preferably, the organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and ethylene carbonate; and the immersion time is 6 to 8 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an operation structure diagram of the method for preparing a single-sided electrode for buckling by using a double-sided coated electrode of the present invention; wherein, 1-current collector; 2-coating layer; 3-double-sided adhesive; 4-steel plate; Figure 2 The measured data of the buckle power produced by the method of the present invention is Figure 1 ; Figure 3 The measured data of the buckle power produced by the method of the present invention is Figure 2 . DETAILED DESCRIPTION

[0021] The technical concept of the present invention is to bond the electrode coating layer to a substrate (such as a steel plate, etc.) with the help of double-sided tape, and to complete the single-sided processing of the double-coated electrode at one time while achieving pre-stripping of the coating layer and the current collector layer, thereby greatly improving the compatibility of the method for preparing the electrode sheet with double-sided coated electrode sheets, shortening the pre-processing time, and improving the success rate of the buckle test.

[0022] Since an overall one-time stripping method is adopted, the relative sizes of the double-sided tape and the pole piece, as well as the upward lifting angle of the free end of the pole piece formed after the pole piece is pre-stripped are further optimized, which can effectively avoid damage to the pole piece during the processing process and improve the qualified rate of single-sided pole piece production.

[0023] For some coating layers with strong cohesion, such as some positive electrodes, conventional wiping methods or single-sided tape stripping methods require multiple wiping or stripping, and the treatment effect is not ideal. The method of the present invention can make the leakage area of ​​the double-sided coated battery electrode foil after single-sided treatment ≥70%. Even if a small amount of coating material remains on the treated surface, it can be removed by simply wiping with a solvent. For the double-sided coated electrode obtained by disassembly, the double-coated battery electrode after single-sided treatment can be further placed in an organic solution for immersion cleaning, drying, cooling, and stamping to complete the production of single-sided electrode for buckle power.

[0024] The implementation process of the present invention is described in detail below in conjunction with specific embodiments.

[0025] The specific embodiment of the method for preparing a single-sided electrode sheet for buckle current by using a double-sided coated electrode sheet of the present invention is as follows: The method of preparing a single-sided electrode sheet for buckle current by using a double-sided coated electrode sheet of this embodiment comprises the following steps: S1: Bond the double-sided tape on the surface of the steel plate, and use a roller to roll the double-sided tape to remove the air residue between the steel plate and the double-sided tape. The surface of the steel plate is required to be flat and smooth, polished, and the surface needs to be cleaned before use. The peel strength of the double-sided tape used after bonding the steel plate and the electrode coating layer is ≥15N / 25mm. This type of double-sided tape can be selected from conventional commercial products, such as 3M brand acrylic foam double-sided tape.

[0026] The width of the roller should be greater than the width of the double-sided tape, and the rolling pressure can be 1-10 kgf, for example, 1 kgf, 3 kgf, 5 kgf, 7 kgf, 10 kgf, so that the double-sided tape and the steel plate are firmly adhered.

[0027] S2: The coating surface on one side of the double-sided coated battery electrode is adhered to the double-sided adhesive of the above-mentioned back-bonded steel plate, and the double-sided adhesive is rolled on the electrode area corresponding to the electrode, and the coating layer and the current collector layer on the double-sided adhesive side of the electrode are manually pre-peeled off. The free end of the electrode after pre-peeling is lifted up at an angle of (0°~90°) to the steel plate, and the coating layer and the current collector are separated, exposing the electrode foil. The single-sided processing of the double-coated electrode can be completed by one peeling.

[0028] The overall structure of the steel plate, double-sided tape, and pole piece is shown in the figure below. Figure 1 As shown. The double-sided coated pole piece includes a current collector 1 and a coating layer 2 coated on both sides of the current collector 1. The double-sided coated pole piece, the double-sided adhesive 3, and the steel plate 4 are stacked together from top to bottom, and the double-sided adhesive 3 is used to firmly bond the coating layer 2 and the steel plate 4 on one side of the double-sided coated pole piece. During bonding, the width of the double-sided adhesive is within the width range of the corresponding coating layer on the pole piece. Preferably, the width of the double-sided adhesive is 70-100% of the width of the coating layer, and the length of the double-sided adhesive covers the length range of the corresponding coating layer on the pole piece, but falls within the length range of the pole piece. In this way, the area of ​​the pole piece is larger than the area of ​​the double-sided adhesive. When the pole piece is lifted up, the edge of the pole piece does not contact the double-sided adhesive, thereby preventing the pole piece from being damaged by the peeling action.

[0029] The double-sided coated battery pole piece in this step can be a positive pole piece or a negative pole piece. When manually pre-peeling the coating layer and the current collector layer on the double-sided adhesive side of the pole piece, the adhesive force of the double-sided adhesive can be directly used or the bonding area of ​​the coating layer and the current collector layer can be further manually separated. The pre-peeling length is ≥1mm, for example, the pre-peeling length is about 1~3mm, and no adhesion is allowed in the pre-peeling part. The upward angle does not exceed 90°, for example, 30°, 45°, 60°, etc., to ensure that the pole piece is flat and the structure is not damaged.

[0030] In this step, the width requirement of the roller and the rolling pressure of the roller are the same as those in step S1, and the purpose is to drive out the air at the bonding position and enhance the bonding firmness.

[0031] To increase the safety of the operation, step S2 is performed in a non-atmospheric exposure environment. The leakage area of ​​the double-sided coated battery pole piece foil obtained after single-sided treatment in S2 is ≥70%. At this time, the foil position that meets the requirements of neatness can be selected for stamping (stamping into a circle) to obtain the pole piece for making buckle electricity.

[0032] In order to further increase the number of single-sided electrode sheets for buckling that can be produced and improve the utilization rate of double-sided coated battery electrode sheets, step S3 can be further performed.

[0033] S3: After single-side treatment, the double-sided coated battery electrode is wiped off with a solvent to remove the coating residue.

[0034] At this time, simply wipe with solvent to remove the coating residue. After the solvent is wiped, the foil leakage area is ≥95%. The wiping solvents used here are mainly deionized water, anhydrous ethanol, N-methylpyrrolidone, etc.

[0035] For the disassembled battery pole pieces, the wiped pole pieces can be further placed in an organic solution for soaking, cleaning and drying, so that there is no glue or other foreign matter left on the treated surface. Then the exposed foil is punched into a circle to obtain a single-sided pole piece for buckle power. The organic solvent here is mainly used to remove the lithium salt and residual electrolyte on the surface of the pole piece. The type of organic solvent is selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, etc., which can dissolve the lithium salt and remove the electrode liquid. The soaking and cleaning time can be selected as 6~8h, such as 6h, 7h, 8h, etc. The drying temperature can be selected as 100~110℃, and the time can be 1~2h.

[0036] The preparation method of the present invention exhibits the following advantages: 1. The stripping efficiency of the coating layer is greatly improved, and the single-side treatment can be completed in one stripping, reducing the time from more than 40 minutes to less than 2 minutes; 2. This method has good compatibility and is still applicable to electrodes with strong cohesion, while the existing wiping method or single-sided tape peeling method requires multiple wiping or peeling, and the effect is not obvious; 3. The peeling can be completed in one time, avoiding the damage to the electrode caused by multiple wiping or peeling; 4. The leakage area of ​​the treated single-sided double-coated electrode foil is high, and there is no glue or other foreign matter left; 5. Use the pre-stripping method to reduce the damage to the electrode during the stripping process.

[0037] Figure 2 , Figure 3 The measured data of the buckle power produced by the method of the present invention are shown in blue for the voltage-time curve and red for the current-time curve. Figure 2 Lithium manganate, Figure 3 The relevant power-off data conform to the standard power-off curve of the corresponding material, indicating that the manufacturing method of the present invention has good stability and reliability.

Claims

1. A method for preparing a single-sided electrode sheet for buckle power using a double-sided coated electrode sheet, characterized in that: The following steps are involved: (1) bonding double-sided tape on the surface of the substrate, bonding the coating surface on one side of the double-sided coated electrode to the double-sided tape of the substrate; (2) The double-sided coated electrode and substrate are placed up and down, the coating layer and the current collector layer on the double-sided adhesive side of the electrode are pre-peeled off, and the free end of the pre-peeled electrode is lifted off from the substrate, and the coating layer and the current collector are separated to form a single-sided electrode.

2. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 1, characterized in that: The length of the pre-stripping in step (2) is ≥1 mm.

3. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 1, characterized in that: When lifting in step (2), lift the cover upwards at an angle not greater than 90°.

4. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 1, characterized in that: When the double-sided tape in step (1) is adhered to the surface of the coating layer, the width of the double-sided tape is within the width range of the corresponding coating layer on the electrode piece; and the length of the double-sided tape covers the length range of the corresponding coating layer on the electrode piece.

5. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 1, characterized in that: After one side of the double-sided adhesive tape is bonded to the substrate and the other side is bonded to the surface of the coating layer, a roller is used to roll the bonding area.

6. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 5, characterized in that: The width of the roller is greater than the width of the double-sided tape; the rolling pressure of the roller is 1-10 kgf.

7. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 1, characterized in that: The peeling strength of the double-sided adhesive to the substrate and the electrode coating layer after bonding is not less than 15N / 25mm.

8. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 1, characterized in that: If there is any coating layer residue after the separation in step (2), the coating layer residue is wiped off with a solvent.

9. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 8, characterized in that: The double-sided coated electrode piece is obtained by disassembling the battery cell, and the erased electrode piece is immersed in an organic solvent, and then dried and stamped to obtain the electrode piece that can be used to make a buckle battery.

10. The method for preparing a single-sided electrode sheet for buckle connection by using a double-sided coated electrode sheet as claimed in claim 9, characterized in that: The organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and ethylene carbonate; and the soaking time is 6 to 8 hours.

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