Method for improving coating bulging edge of negative pole piece and negative pole piece

Abstract

The invention provides a method for improving coating edge bulging of a negative pole piece and the negative pole piece, and relates to the technical field of negative pole pieces. The method for improving the coating bulging edge of the negative pole piece comprises the following steps: polishing the surface of a current collector to obtain a polished current collector; performing ultrasonic treatment on the polished current collector to obtain a treated current collector; and coating the treated current collector to obtain the negative pole piece. According to the method for improving the coating bulging edge of the negative pole piece, real-time surface treatment can be carried out on the current collector before coating, the operation is convenient and simple, and the cost is low.

Description

Technical Field

[0001] The present application relates to the technical field of negative electrode plates, and in particular to a method for improving the coating drum edge of a negative electrode plate and a negative electrode plate. Background Art

[0002] Coating is one of the most important links in the production process of lithium-ion batteries and sodium-ion batteries, and the surface parameters of the current collector determine the coating quality.

[0003] As one of the materials of the current collector, the foil has a small dyne value, so it is difficult to coat on the foil, and defects such as foil leakage, edge bulging, and edge material shrinkage are prone to occur.

[0004] Therefore, there is an urgent need to solve the problems of foil leakage, edge bulging, and edge material shrinkage that occur when foil is used as a current collector. Summary of the invention

[0005] The purpose of the present application is to provide a method for improving the coating drum edge of a negative electrode plate and a negative electrode plate to solve the above-mentioned problems.

[0006] To achieve the above objectives, the first aspect of the present application provides a method for improving the coating bulge of a negative electrode sheet, comprising:

[0007] Polishing the surface of the current collector to obtain a polished current collector;

[0008] subjecting the polished current collector to ultrasonic treatment to obtain a treated current collector;

[0009] The treated current collector is coated to obtain a negative electrode sheet.

[0010] Optionally, the surface of the current collector has scratches after polishing, satisfying at least one of the following conditions:

[0011] A. The width of the scratch on the surface of the current collector after polishing is 0.1 μm-100 μm;

[0012] B. The ratio of the thickness of the current collector to the depth of the scratch is 1:(5-150).

[0013] Optionally, the method for improving the coating drum edge of the negative electrode sheet satisfies at least one of the following conditions:

[0014] A. The polishing is done with a soft-bristled steel wire brush;

[0015] B. The polishing includes: rotating the soft-bristled steel wire brush on the surface of the current collector in a parallel direction to the coating.

[0016] Optionally, the relative rotation speed of the soft-bristled wire brush and the coating is 1 rpm-100 rpm.

[0017] Optionally, the ultrasonic treatment includes: immersing the polished current collector in a solvent;

[0018] Or the solvent is sprayed on the surface of the polished current collector.

[0019] Optionally, the method for improving the coating drum edge of the negative electrode sheet satisfies at least one of the following conditions:

[0020] A. The power of the ultrasound is 5Hz-50000Hz;

[0021] B. The ultrasound time is 5-30min;

[0022] C. The temperature of the ultrasound is 30°C-50°C;

[0023] D. The solvent includes ethanol and / or water.

[0024] Optionally, before the coating is performed, the treated current collector is also subjected to a dehumidification treatment.

[0025] Optionally, the method for improving the coating drum edge of the negative electrode sheet satisfies at least one of the following conditions:

[0026] A. The temperature of the dehumidification treatment is 25°C-35°C;

[0027] B. After the dehumidification treatment, the treated current collector is further subjected to an air blowing treatment.

[0028] Optionally, the method for improving the coating drum edge of the negative electrode sheet satisfies at least one of the following conditions:

[0029] A. The negative electrode plate includes a sodium ion negative electrode plate;

[0030] B. the coating slurry includes hard carbon;

[0031] C. The current collector comprises aluminum foil.

[0032] A second aspect of the present application provides a negative electrode plate, which is prepared by the method for improving the coating drum edge of the negative electrode plate.

[0033] Compared with the prior art, the beneficial effects of this application include:

[0034] The method for improving the coating drum edge of the negative electrode plate provided in the present application first performs polishing to remove the oxide film and impurities on the surface of the current collector, thereby increasing the dyne value of the current collector and improving the adhesion of the current collector surface, and then uses ultrasound to remove the metal powder on the surface of the current collector after polishing, and can also cause serious plastic deformation of the impacted metal surface through the accumulation of high-frequency ultrasonic impact, causing lattice distortion inside the material, dislocation proliferation and slip, thereby changing the microstructure of the foil surface after polishing and improving the adhesion of the foil; the method for improving the coating drum edge of the negative electrode plate can perform real-time surface treatment on the current collector before coating, and is convenient and simple to operate at a low cost.

[0035] The edge of the negative electrode sheet provided in the present application will not bulge after being coated with the slurry, which is beneficial to the subsequent winding of the electrode sheet, reduces the winding defects caused by the bulging edge of the electrode sheet, and improves the winding core yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0037] Figure 1 This is a physical picture of the treated aluminum foil prepared in Example 1;

[0038] Figure 2 This is a physical picture of the negative electrode sheet prepared in Example 1. DETAILED DESCRIPTION

[0039] As used herein:

[0040] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0041] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0042] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0043] In these examples, parts and percentages are by mass unless otherwise indicated.

[0044] "Parts by mass" refers to the basic unit of measurement for expressing the mass ratio of multiple components. 1 part can represent any unit mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass of all components is not limited to 100 parts.

[0045] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0046] The first aspect of the present application provides a method for improving the coating bulge of a negative electrode sheet, comprising:

[0047] Polishing the surface of the current collector to obtain a polished current collector;

[0048] subjecting the polished current collector to ultrasonic treatment to obtain a treated current collector;

[0049] The treated current collector is coated to obtain a negative electrode sheet.

[0050] In some embodiments, the surface of the current collector has scratches after polishing, satisfying at least one of the following conditions:

[0051] A. The width of the scratch on the surface of the current collector after polishing is 0.1 μm-100 μm;

[0052] Optionally, the width of the scratches on the surface of the current collector after polishing may be 0.1 μm, 1 μm, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm or any value between 0.1 μm and 100 μm;

[0053] It should be noted that the width of the scratch on the surface of the current collector after polishing is 0.1μm-100μm, and the scratch width should not be too large. If the scratch width is greater than 100μm, part of the negative electrode slurry will be at the bottom of the scratch, and the other part of the negative electrode slurry will be on the surface of the current collector, resulting in uneven coating. When the width is less than 0.1μm, the current collector width is relatively small and the cost is relatively high.

[0054] B. The ratio of the thickness of the current collector to the depth of the scratch is 1:(5-150).

[0055] Optionally, the ratio of the thickness of the current collector to the depth of the scratch can be 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, 1:110, 1:120, 1:130, 1:140, 1:150 or any value between 1:(5-150).

[0056] It should be noted that when the scratch depth is deep, it will cause the foil to wrinkle.

[0057] In some optional embodiments, the scratch depth is 0.1 μm-1 μm, and the thickness of the current collector is 5 μm-15 μm.

[0058] Optionally, the method for improving the coating drum edge of the negative electrode sheet satisfies at least one of the following conditions:

[0059] A. The polishing is done with a soft-bristled steel wire brush;

[0060] It should be noted that the cost of using a soft-bristled steel wire brush for polishing is low, and the soft-bristled steel wire brush has a soft structure and will not cause damage to the current collector.

[0061] B. The polishing includes: rotating the soft-bristled steel wire brush on the surface of the current collector in a parallel direction to the coating.

[0062] It should be noted that the soft-bristled steel wire brush is rotated on the surface of the current collector in a direction parallel to the coating, mainly to prevent the negative electrode slurry from flowing perpendicular to the coating direction after being coated on the negative electrode plate. The soft-bristled steel wire brush is rolled parallel to the coating direction, and scratches parallel to the coating direction are produced on the surface of the current collector, which hinders the flow of slurry perpendicular to the coating direction.

[0063] In some embodiments, the relative rotation speed of the soft-bristled wire brush and the coating is 1 rpm-100 rpm.

[0064] Optionally, the relative rotation speed may be 1 rpm, 10 rpm, 20 rpm, 40 rpm, 60 rpm, 80 rpm, 100 rpm or any value between 1 rpm and 100 rpm.

[0065] It should be noted that the relative rotation speed is greater than 100 rpm. Too fast a rotation speed will cause wrinkles on the current collector.

[0066] In some embodiments, the ultrasonication includes: immersing the polished current collector in a solvent;

[0067] Or the solvent is sprayed on the surface of the polished current collector.

[0068] It should be noted that when the solvent is sprayed on the surface of the polished current collector for ultrasonic treatment, the accumulation of high-frequency ultrasonic shock causes severe plastic deformation of the impacted metal surface, causing lattice distortion inside the material, dislocation proliferation and slip, thereby changing the microstructure of the current collector surface, increasing the dyne value and improving wettability.

[0069] In some embodiments, the method for improving the coating drum edge of the negative electrode sheet satisfies at least one of the following conditions:

[0070] A. The power of the ultrasound is 5Hz-50000Hz;

[0071] Optionally, the power of the ultrasound can be 5 Hz, 10 Hz, 50 Hz, 100 Hz, 1000 Hz, 5000 Hz, 10000 Hz, 50000 Hz or any value between 5 Hz and 50000 Hz;

[0072] B. The ultrasonic time is 5min-30min;

[0073] Optionally, the ultrasonic time can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min or any value between 5 min and 30 min;

[0074] C. The temperature of the ultrasound is 30°C-50°C;

[0075] Optionally, the temperature of ultrasound can be 30°C, 35°C, 40°C, 45°C, 50°C or any value between 30°C and 50°C;

[0076] D. The solvent includes ethanol and / or water.

[0077] In some embodiments, before the coating, the treated current collector is further subjected to a dehumidification treatment.

[0078] It should be noted that dehumidification can accelerate the volatilization of solvents.

[0079] In some embodiments, the method for improving the coating drum edge of the negative electrode sheet satisfies at least one of the following conditions:

[0080] A. The temperature of the dehumidification treatment is 25°C-35°C;

[0081] Optionally, the temperature of the dehumidification treatment may be 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C or any value between 25°C and 35°C;

[0082] B. After the dehumidification treatment, the treated current collector is further subjected to an air blowing treatment.

[0083] It should be noted that the air blast treatment can remove the metal powder remaining on the current collector after treatment.

[0084] In some embodiments, the method for improving the coating drum edge of the negative electrode sheet satisfies at least one of the following conditions:

[0085] A. The negative electrode plate includes a sodium ion negative electrode plate;

[0086] B. the coating slurry includes hard carbon;

[0087] C. The current collector comprises aluminum foil.

[0088] It should be noted that the negative electrode of the sodium ion battery mainly adopts hard carbon. The specific surface area of ​​the hard carbon negative electrode is twice that of the graphite negative electrode. Therefore, its current collector is usually set to aluminum foil. The dyne value of aluminum foil is smaller than that of copper foil. Therefore, it is difficult to coat the slurry made of the sodium ion hard carbon negative electrode on the aluminum foil, and it is easy to have defects such as foil leakage, edge bulging, and edge material shrinkage. The method of improving the bulging edge of the negative electrode plate coating in this application can effectively improve the dyne value of the aluminum foil (current collector), improve the wettability of hard carbon on the surface of the aluminum foil, and reduce defects such as foil leakage, edge bulging, and edge material shrinkage.

[0089] A second aspect of the present application provides a negative electrode plate, which is prepared by the method for improving the coating drum edge of the negative electrode plate.

[0090] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0091] Example 1

[0092] A first aspect of this embodiment provides a method for improving the coating bulge of a negative electrode plate, comprising:

[0093] A soft-bristled steel wire brush is used to polish the surface of the aluminum foil. The rotation speed of the soft-bristled steel wire brush is 20 rpm, and the rotation speed of the aluminum foil is 15 m / min. The aluminum foil after the brushing roller is obtained. The scratch on the surface of the aluminum foil after the brushing roller is 0.1 μm, and the ratio of the thickness of the aluminum foil to the depth of the scratch is 1:5;

[0094] The aluminum foil after brushing is subjected to ultrasound in ethanol, the power of ultrasound is 1000 Hz, and the time is 0.25 h to obtain the treated aluminum foil;

[0095] The treated aluminum foil is coated by continuous extrusion to obtain a negative electrode sheet for a sodium ion battery. The coated slurry includes hard carbon, a binder (PVDF), and a conductive agent (CNT).

[0096] The actual aluminum foil after treatment is as follows Figure 1 shown.

[0097] A second aspect of this embodiment provides a negative electrode plate, which is prepared by the above-mentioned method for improving the coating drum edge of the negative electrode plate.

[0098] The negative electrode is as follows Figure 2 shown.

[0099] Example 2

[0100] A first aspect of this embodiment provides a method for improving the coating bulge of a negative electrode plate, comprising:

[0101] The carbon-coated aluminum foil surface was polished by a soft-bristled steel wire brush at a rotation speed of 30 rpm and a rotation speed of 10 m / min. The carbon-coated aluminum foil was polished by a brush roller. The scratch on the surface of the carbon-coated aluminum foil was 0.1 μm, and the ratio of the thickness of the carbon-coated aluminum foil to the depth of the scratch was 1:5.

[0102] The carbon-coated aluminum foil after brushing was subjected to ultrasonic treatment in ethanol at a power of 500 Hz for 1 h.

[0103] The carbon-coated aluminum foil after ultrasonic treatment is then dehumidified using a dehumidifier at a temperature of 25° C. to obtain the treated carbon-coated aluminum foil;

[0104] The treated carbon-coated aluminum foil is coated with a slurry including hard carbon to obtain a negative electrode sheet for a sodium ion battery.

[0105] A second aspect of this embodiment provides a negative electrode plate, which is prepared by the above-mentioned method for improving the coating drum edge of the negative electrode plate.

[0106] Example 3

[0107] A first aspect of this embodiment provides a method for improving the coating bulge of a negative electrode plate, comprising:

[0108] Use a soft-bristled steel wire brush to perform brush roller polishing on the surface of the aluminum foil, and rotate it on the surface of the aluminum foil in the parallel direction of the coating. The rotation speed of the soft-bristled steel wire brush is 20 rpm, and the rotation speed of the carbon-coated aluminum foil is 15 m / min. The aluminum foil after brush roller polishing is obtained. The scratch on the surface of the aluminum foil after brush roller polishing is 100 μm, and the ratio of the thickness of the aluminum foil to the depth of the scratch is 1:150;

[0109] The aluminum foil after brushing the roller was subjected to ultrasound in ethanol, with the power of ultrasound being 50000 Hz and the time being 0.5 h;

[0110] The aluminum foil after ultrasonic treatment is then dehumidified using a dehumidifier at a temperature of 30° C. to obtain a treated aluminum foil;

[0111] The treated aluminum foil is processed in a blast zone and then coated with a slurry including hard carbon to obtain a negative electrode sheet for a sodium ion battery.

[0112] A second aspect of this embodiment provides a negative electrode plate, which is prepared by the above-mentioned method for improving the coating drum edge of the negative electrode plate.

[0113] Comparative Example 1

[0114] The first aspect of this comparative example provides a method for improving the bulging edge of the negative electrode plate coating, which is different from Example 1 in that polishing is not performed in this comparative example, and other conditions are consistent with Example 1.

[0115] The second aspect of this comparative example provides a method for improving the coating drum edge of a negative electrode plate, which is prepared by the above-mentioned method for improving the coating drum edge of a negative electrode plate.

[0116] Comparative Example 2

[0117] The first aspect of this comparative example provides a method for improving the bulging edge of the negative electrode plate coating, which is different from Example 1 in that ultrasound is not performed in this comparative example, and other conditions are consistent with Example 1.

[0118] The second aspect of this comparative example provides a method for improving the coating drum edge of a negative electrode plate, which is prepared by the above-mentioned method for improving the coating drum edge of a negative electrode plate.

[0119] Comparative Example 3

[0120] The first aspect of this comparative example provides a method for improving the coating bulge of the negative electrode plate, which is different from Example 1 in that this comparative example first performs ultrasound and then polishing, and other conditions are consistent with Example 1.

[0121] The second aspect of this comparative example provides a method for improving the coating drum edge of a negative electrode plate, which is prepared by the above-mentioned method for improving the coating drum edge of a negative electrode plate.

[0122] The performance of the negative electrode sheets prepared in the above embodiments and comparative examples was tested, and the specific test results are shown in Table 1.

[0123] Table 1 Negative electrode performance test

[0124] sample Adhesion Example 1 Through the steel needle with a diameter of 3 Example 2 Through the steel needle with a diameter of 3 Example 3 Through the steel needle with a diameter of 3 Comparative Example 1 Through the diameter of 5 steel needle Comparative Example 2 Through the diameter of 5 steel needle Comparative Example 3 Through the steel needle with a diameter of 4

[0125] As shown in Table 1, polishing and ultrasonic treatment of the negative electrode current collector can increase the dyne value of the foil, improve wettability, and increase the adhesion of the electrode sheet, while the sequential effect of the two is relatively small.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0127] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present application and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for improving the coating bulge of a negative electrode plate, characterized in that: include: Polishing the surface of the current collector to obtain a polished current collector; subjecting the polished current collector to ultrasonic treatment to obtain a treated current collector; The treated current collector is coated to obtain a negative electrode sheet.

2. The method for improving the coating bulge of the negative electrode sheet according to claim 1, characterized in that: The surface of the current collector has scratches after polishing, which satisfies at least one of the following conditions: A. The width of the scratch on the surface of the current collector after polishing is 0.1 μm-100 μm; B. The ratio of the thickness of the current collector to the depth of the scratch is 1:5-1:

150.

3. The method for improving the coating bulge of the negative electrode sheet according to claim 1, characterized in that: At least one of the following conditions is met: A. The polishing is done with a soft-bristled steel wire brush; B. The polishing includes: rotating the soft-bristled steel wire brush on the surface of the current collector in a parallel direction to the coating.

4. The method for improving the coating bulge of the negative electrode sheet according to claim 3, characterized in that: The relative rotation speed of the soft-bristled steel wire brush and the coating is 1 rpm-100 rpm.

5. The method for improving the coating bulge of the negative electrode sheet according to claim 1, characterized in that: The ultrasonic treatment comprises: immersing the polished current collector in a solvent; Or the solvent is sprayed on the surface of the polished current collector.

6. The method for improving the coating bulge of the negative electrode sheet according to claim 5, characterized in that: At least one of the following conditions is met: A. The power of the ultrasound is 5Hz-50000Hz; B. The ultrasound time is 5-30min; C. The temperature of the ultrasound is 30°C-50°C; D. The solvent includes ethanol and / or water.

7. The method for improving the coating bulge of the negative electrode sheet according to claim 1, characterized in that: Before the coating is performed, the treated current collector is further subjected to a dehumidification treatment.

8. The method for improving the coating bulge of the negative electrode sheet according to claim 7, characterized in that: At least one of the following conditions is met: A. The temperature of the dehumidification treatment is 25°C-35°C; B. After the dehumidification treatment, the treated current collector is further subjected to an air blowing treatment.

9. The method for improving the coating bulge of negative electrode sheet according to any one of claims 1 to 8, characterized in that: At least one of the following conditions is met: A. The negative electrode plate includes a sodium ion negative electrode plate; B. the coating slurry includes hard carbon; C. The current collector comprises aluminum foil.

10. A negative electrode plate, characterized in that: The negative electrode is prepared by the method for improving the coating drum edge of the negative electrode sheet according to any one of claims 1 to 9.

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