Appearance protection method of lithium ion battery and lithium ion battery

Abstract

The invention discloses an appearance protection method of a lithium ion battery, which comprises the following steps: spraying: spraying on the surface of the lithium ion battery to form a protection layer; detecting and post-processing: detecting the appearance of the sprayed lithium ion battery, and if the lithium ion battery is detected to be qualified, enabling the lithium ion battery to enter the next process; if the lithium ion battery is detected to be unqualified, reworking laser cleaning is carried out on the lithium ion battery to remove the protective layer, the spraying step and the detection and aftertreatment step are carried out again until the lithium ion battery with the qualified protective layer is obtained, and according to reworking laser cleaning, the cleaning power is 68-72%, the cleaning frequency is 235-245Hz, the cleaning time is 10.88-13.56 seconds, and the linear speed is 0.55-0.81 m / min. Through the method, when laser cleaning needs to be reworked after spraying, water ripples are prevented from appearing on the surface of the shell, the appearance quality of the battery is improved, and the long-term stable performance of the battery is ensured. The invention also discloses a lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a method for protecting the appearance of a lithium ion battery and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries are important energy storage units in modern consumer electronics, industrial applications, and electric vehicles. With the growing global demand for environmentally friendly and high-performance technologies, the application range of lithium ion batteries is becoming more and more extensive. In addition to its core performance, the appearance quality also plays a crucial role in the safety, performance, and market competitiveness of the battery. Good appearance is a symbol of high-quality batteries, and the appearance of lithium ion batteries is also directly related to the safety of the battery. Specifically, the battery shell protects the internal structure (such as positive and negative materials, electrolyte, etc.) from external physical damage, chemical corrosion, or environmental factors. However, during production, transportation, and use, the shell of lithium ion batteries is prone to scratches, rust, discoloration, and other appearance defects due to factors such as friction, collision, acid and base corrosion. These defects not only affect the appearance and market acceptance of the product, but also may damage the integrity of the shell, for example, scratches on the metal shell may become a channel for corrosion medium to invade, gradually eroding the shell and threatening the sealing of the internal structure; the wear of plastic or composite shell may reduce its insulation performance and increase the risk of short circuit.

[0003] Therefore, it is necessary to protect the appearance of lithium ion. Compared with traditional film coating technology, anodic oxidation, and heat shrink sleeve, etc., spraying a protective layer (such as UV spraying and paint spraying process) on the surface of the lithium ion battery not only has simple process, high applicability, and strong flexibility, but also can provide more uniform and less defective appearance protection, and the protective layer has a relatively longer service life, which can adapt to various different working conditions. The external coating can prevent the battery surface from oxidizing, corroding, and providing certain thermal insulation performance, thereby delaying the heat conduction between the inside and outside of the battery, helping the battery to maintain a stable working temperature. In addition, it can effectively prevent scratches, wear and dirt accumulation on the surface of the battery, thereby prolonging the service life of the battery.

[0004] In the appearance protection process of forming a protective layer by spraying, laser cleaning is an important surface treatment method. Before the spraying process, laser cleaning is mainly used in the pretreatment link. The battery shell is easy to contaminate with oil stains, dust and other impurities during manufacturing and handling, which can seriously affect the adhesion and uniformity of the subsequent protective layer. Laser cleaning can accurately and efficiently remove such contaminants, while increasing the surface roughness of the shell, greatly improving the adhesion of the coating and ensuring the long-term stable performance of the protective layer. When the protective layer needs to be reworked due to defects, laser cleaning also has obvious advantages. For example, in UV spraying or painting process, if the protective layer is unqualified, the surface of the unqualified protective layer needs to be removed and resprayed. Laser cleaning can strip the coating layer by layer to provide a clean surface for respraying, and can realize full-process automation, greatly improving the efficiency and accuracy of rework.

[0005] However, when the lithium ion battery needs to be reworked after spraying, the conventional laser cleaning parameters commonly used in the art will inevitably cause the surface of the metal shell (such as steel shell or aluminum shell) of the lithium ion battery to have a "water ripple" pattern (as shown in Figure 3 This water ripple not only affects the appearance quality of the battery, but also may affect the adhesion of the protective layer, reducing the overall performance and market competitiveness of the battery. SUMMARY

[0006] To solve the above technical problems, the embodiments of the present application disclose a method for appearance protection of a lithium ion battery, comprising the following steps:

[0007] Spraying: spraying on the surface of the lithium ion battery to form a protective layer;

[0008] Detection and post-processing: detecting the appearance of the lithium ion battery after spraying. If the detection is qualified, the lithium ion battery enters the next process; if the detection is unqualified, the lithium ion battery is reworked by laser cleaning to remove the protective layer and respraying, detection and post-processing steps until a qualified lithium ion battery with a protective layer is obtained, wherein the cleaning power of the rework laser cleaning is 68-72%, the cleaning frequency is 235-245 Hz, the cleaning time is 10.88-13.56 seconds, and the linear speed is 0.55-0.81 m / min.

[0009] By using the above technical solution, when rework laser cleaning is needed after spraying, water ripples can be avoided on the surface of the shell, the appearance quality of the battery can be improved, and its long-term stable performance can be ensured.

[0010] Optionally, the cleaning power is 70-72%, and the cleaning frequency is 240-245 Hz.

[0011] Optionally, the cleaning time is 11.58-12.91 seconds, and the linear speed is 0.61-0.74 m / min.

[0012] Optionally, before the spraying step is performed for the first time, a first laser cleaning step is further included, in which the cleaning power is 88-92% and the cleaning frequency is 275-285 Hz.

[0013] Optionally, in the first laser cleaning step, the cleaning duration is 5.43-8.47 seconds and the linear speed is 1.0-1.3 m / min.

[0014] Optionally, the protective layer comprises a light-cured material.

[0015] Optionally, the spraying step is performed on the surface of the lithium ion and is cured by ultraviolet light to form the protective layer.

[0016] Embodiments of the present application also disclose a lithium ion battery based on the appearance protection method of the lithium ion battery.

[0017] The above technical solution can avoid water ripples on the shell of the lithium ion battery, and obtain a lithium ion battery with high appearance quality and stable appearance performance.

[0018] Embodiments of the present application also disclose a lithium ion battery, and the appearance of the lithium ion battery is protected.

[0019] The above technical solution guarantees the surface quality and aesthetic degree of the lithium ion battery.

[0020] Optionally, the lithium ion battery obtains a protective layer after the appearance protection, and the protective layer is free of defects such as spots, mura and color unevenness. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A photograph of the surface of the shell of the battery after the first laser cleaning of Example 1 of the present application is shown.

[0022] Figure 2 A photograph of the surface of the shell of the battery after the rework laser cleaning of Example 1 of the present application is shown.

[0023] Figure 3 A photograph of the surface of the shell of the battery after the rework laser cleaning of Comparative Example 1 of the present application is shown. DETAILED DESCRIPTION

[0024] The following description will be made to the embodiments of the present application by specific examples, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure of the present application. Although the description of the present application will be introduced in combination with the preferred embodiments, it does not mean that the features of the present application are limited to the embodiments. On the contrary, the purpose of introducing the present application in combination with the embodiments is to cover other options or modifications which can be extended based on the claims of the present application. In order to provide a deep understanding of the present application, many specific details will be included in the following description. The present application can also be implemented without using these details. In addition, in order to avoid confusion or obscure the focus of the present application, some specific details will be omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0025] It should be noted that in the present specification, similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0026] The terms "first", "second", and the like are only used to distinguish description, and cannot be understood as indicating or implying relative importance.

[0027] In the embodiments of the present application, the "cleaning power" refers to the ratio of the actual output power of the laser device to the rated maximum power of the device. It reflects the relative intensity of the output energy of the laser per unit time in the cleaning process. For example, if the rated maximum power of the laser device is 1000W, 70% means that the actual cleaning power is 700W.

[0028] In the embodiments of the present application, the "cleaning frequency" refers to the number of laser pulses emitted by the laser device per unit time (per second). For example, 240Hz means that 240 laser pulses are emitted per second.

[0029] In the embodiments of the present application, the "linear speed" refers to the speed of the laser beam when scanning and moving on the surface of the lithium ion battery. For example, 0.81m / min represents that the distance through by the laser beam per minute is 0.81 meters when the laser beam moves along the preset scanning path on the surface of the lithium ion battery.

[0030] In order to make the purpose, technical solutions and advantages of the present application more clear, the embodiments of the present application will be further described in detail below in combination with the drawings.

[0031] The first aspect of the present application discloses a method for protecting the appearance of a lithium ion battery, comprising the following steps:

[0032] Spraying: spraying on the surface of the lithium ion battery to form a protective layer, wherein the surface of the lithium ion battery is specifically the surface of the outermost shell of the lithium ion battery, such as a metal shell, an aluminum shell, etc.

[0033] Detection and post-processing: the appearance of the sprayed lithium ion battery is detected, if the detection is qualified, the lithium ion battery enters the next process; if the detection is unqualified, the lithium ion battery is reworked laser cleaning to remove the protective layer and re-spraying and detection and post-processing steps until a qualified lithium ion battery is obtained, wherein the cleaning power of the rework laser cleaning is 68-72%, the cleaning frequency is 235-245Hz, the cleaning time is 10.88-13.56 seconds, and the linear speed is 0.55-0.81m / min.

[0034] In the field, the appearance of lithium ion battery is prevented from rework laser cleaning process, the setting of various laser cleaning parameters always follows the traditional experience parameters accumulated in the field for a long time, but in actual production application, due to the limited thickness and strong heat sensitivity of the metal shell, and the need for a certain laser intensity and cleaning time to remove the unqualified protective layer on the surface, it is found that under these conventional cleaning parameters, the local heat distribution of the shell is uneven or the local stress is concentrated, and then the obvious "water ripple" concave-convex morphology is formed on the surface. This water ripple not only destroys the flatness of the shell, making it difficult for the protective layer to adhere uniformly after re-spraying, but also exacerbates the stress concentration during battery use, causing the protective layer to crack, affecting product quality, and resulting in products that can only be used as substandard products, with low product yield. At the same time, the laser cleaning effect is affected by multiple factors such as power, frequency, and line speed, and if a single parameter is adjusted, it will cause mismatch between parameters, not only unable to solve the water ripple problem, but also affect the cleaning effect. Therefore, the workload of adjusting laser cleaning parameters is huge, and it is necessary to gradually explore the laser cleaning parameters, considering not only the influence of a single parameter, but also the mutual influence between parameters, and finding the best match of parameter combination. For example, in terms of a single parameter, the control of laser power directly affects the cleaning effect, and too high power may cause local overheating of the surface, causing water ripple or coating damage, and too low power may result in incomplete cleaning, therefore, by accurately adjusting the laser power within a reasonable range, the surface cleaning effect can be ensured while avoiding unnecessary damage. For example, laser cleaning speed also has a significant impact on cleaning effect, faster cleaning speed may result in uneven cleaning, local pressure difference, and water ripple, and slower speed may cause excessive heat accumulation and thermal stress, and the cleaning speed is related to cleaning power, cleaning frequency, and cleaning time, therefore, the matching relationship between parameters needs to be adjusted to find the best cleaning speed. The present application forms a matching relationship between various cleaning parameters, which can effectively eliminate the water ripple phenomenon during laser rework cleaning, improve the appearance quality of the battery, ensure the long-term stable performance of the battery, and is beneficial to the production of high-quality batteries. Through the adjustment of rework laser cleaning parameters, the yield of batteries that need to be re-sprayed reaches 98.7%.

[0035] In the embodiment of the present application, the detection process in the detection and post-processing step, specifically after the protective layer is formed, the protective layer is observed by the naked eye. The unqualified battery of the protective layer may have defects such as spots, mura and uneven color. Among them, the spots include black spots (black or dark brown spot-shaped, patch-shaped defects) and / or white spots (white or light gray spot-shaped, patch-shaped defects), and the black and white spots are usually caused by the influence of environmental dust. Mura refers to the periodic light and dark stripes or ring patterns appearing on the surface of the protective layer, which is usually caused by unstable spraying parameters or other parameters. These problems seriously affect the appearance of the battery and the insulation voltage performance of the protective layer. The battery after spraying does not have defects such as spots, mura, uneven color, etc., which belongs to the qualified lithium ion battery of the protective layer.

[0036] In the embodiment of the present application, specifically, in the spraying step, a spraying process is used to spray the coating that can form the protective layer on the surface of the lithium ion battery. The spraying process includes electrostatic spraying, air spraying, spin coating and other different spraying processes.

[0037] In the embodiment of the present application, specifically, in the spraying step, a spraying process is used to spray the coating that can form the protective layer on the surface of the lithium ion battery. The coating forms the protective layer after drying or curing and other steps.

[0038] In the embodiment of the present application, specifically, the protective layer includes various materials such as resin materials or polyurethane materials.

[0039] In the embodiment of the present application, preferably, the protective layer includes a light-curing material, for example, a light-curing resin material, which can be cured under light conditions such as ultraviolet light. Specifically, the light-curing material is, for example, a material such as silicone acrylate, fluorine propylene acrylate, or polyimide.

[0040] In the embodiment of the present application, preferably, in the spraying step, UV spraying technology is used to form the protective layer. After spraying the coating containing light-curing material, photoinitiator, crosslinking agent and other components on the surface of the lithium ion battery, the protective layer is formed by curing with ultraviolet light. Compared with traditional appearance protection measures, UV spraying technology has significant advantages, especially in the surface treatment process of lithium ion batteries. UV spraying technology uniformly sprays the coating containing light-curing material to the surface of the battery through precise spraying equipment, and then cures the coating by ultraviolet irradiation to form a firm and uniform protective layer. It has strong applicability, fast curing speed, does not pollute the environment, and the formed protective layer has stable performance and good appearance.

[0041] In the embodiment of the present application, preferably, the cleaning power is 70-72%, the cleaning frequency is 240-245 Hz, and / or the cleaning time is 11.58-12.91 seconds, and the linear speed is 0.61-0.74 m / min, which further balances the cooperation between the parameters, ensures the cleaning effect of the protective layer, avoids the generation of water ripples, improves the cleaning efficiency, and reduces the risk of damage to the shell.

[0042] In the embodiment of the present application, further, before the first spraying step, a first laser cleaning step is further included, in which the cleaning power is 88-92% and the cleaning frequency is 275-285 Hz. The first laser cleaning step can pretreat the surface of the battery shell, remove stains, dust and the like attached to the battery shell, improve the adhesion of the shell to the protective layer, and reduce the possibility of defects in the subsequent protective layer. By setting the cleaning power to 88-92% and the cleaning frequency to 275-285 Hz, on the one hand, the appearance quality and stability of the protective layer formed after spraying can be improved, and the possibility of rework can be reduced, and on the other hand, the rework laser cleaning can be matched, forming a whole-process parameter coordination system of "pretreatment-spraying-rework repair", improving the production efficiency and reducing the energy consumption, while avoiding the cumulative thermal damage caused by multiple treatments, and improving the yield of spraying after rework.

[0043] In the embodiment of the present application, further, in the first laser cleaning step, the cleaning time is 5.43-8.47 seconds, and the linear speed is 1.0-1.3 m / min. The first cleaning only needs to remove surface contaminants and form moderate roughening, without the need for layer-by-layer fine peeling of unqualified coating as in rework cleaning, so the efficiency can be improved by increasing the linear speed and shortening the time; and the rework cleaning needs to reduce the linear speed and extend the time to accurately control the energy input in order to avoid damaging the substrate. This parameter difference further strengthens the cooperation of the whole process of "pretreatment-spraying-rework repair", balances the production efficiency and energy consumption while ensuring the effect of each link, and further avoids surface damage.

[0044] In the embodiment of the present application, the appearance protection method of the lithium ion battery is that the shell of the lithium ion battery is first laser cleaned, that is, surface pretreated, then sprayed, for example, UV sprayed, to form a protective layer, and then the protective layer is quality inspected. If the protective layer is qualified, it enters the next process. If the protective layer is unqualified, it is reworked and laser cleaned to remove the unqualified protective layer, then resprayed to form a new protective layer, and then continuously inspected. If it is qualified, it enters the next process. If it is unqualified, it is continuously reworked until a qualified protective layer is obtained. After the rework laser cleaning parameters of the present application are used, the lithium ion battery with a qualified protective layer can usually be obtained after the first rework and respraying, and the yield is high. The laser cleaning parameters of the present application are also particularly suitable for being combined with the UV spraying process, and the production efficiency is high, the cleaning effect is good, and the high-quality lithium ion battery can be prepared.

[0045] The second aspect of the present application discloses a lithium ion battery, which has a protective layer on the surface, and the protective layer is obtained by the appearance protection method of the lithium ion battery of each embodiment described above. The lithium ion battery has excellent appearance performance, and the stability and reliability of the protective layer are strong, and the quality of the battery is guaranteed.

[0046] The third aspect of the present application discloses a lithium ion battery, and the appearance of the lithium ion battery is protected. The appearance protection includes rework laser cleaning treatment. After the rework laser cleaning treatment, the surface of the lithium ion battery does not appear water ripples.

[0047] Further, the lithium ion battery obtains a protective layer after the appearance protection. The protective layer does not have defects such as spots, Moire circles and color unevenness.

[0048] Further, the appearance protection of the lithium ion battery is the appearance protection method of each embodiment of the present application. After the rework laser cleaning treatment, the surface of the lithium ion battery does not appear water ripples.

[0049] The more specific embodiments will be described below.

[0050] The present application has carried out a large number of experiments on the selection of each cleaning parameter in the laser cleaning stage and the cooperation between the cleaning parameters. It is finally found that when the cleaning power of the rework laser cleaning is 68-72%, the cleaning frequency is 235-245 Hz, the cleaning time is 10.88-13.56 seconds, and the line speed is 0.55-0.81 m / min, the water ripples of the shell of the lithium ion battery can be removed, the battery has good appearance, and the subsequent protective layer can be attached. Some experimental data will be described below.

[0051] Example 1:

[0052] The lithium ion battery with metal shell was firstly laser cleaned (the specific cleaning parameters were: cleaning power was 90%, cleaning frequency was 280 Hz, cleaning time was 8.37 seconds, and linear velocity was 1.2 m / min), the surface condition of the shell after the first laser cleaning was as shown in Figure 1 , then UV spraying was performed to form a protective layer, and then rework laser cleaning was performed to remove the surface protective layer, the cleaning parameters were: cleaning power was 70%, cleaning frequency was 240 Hz, cleaning time was 12.49 s, and linear velocity was 0.69 m / min. The surface condition of the shell after the rework laser cleaning of Example 1 was as shown in Figure 2 .

[0053] Comparative Example 1

[0054] The difference from Example 1 was only that the cleaning parameters of the rework laser cleaning were conventional cleaning parameters, specifically: cleaning power was 90%, cleaning frequency was 280 Hz, cleaning time was 8.37 seconds, and linear velocity was 1.2 m / min. The surface condition of the shell after the rework laser cleaning of Comparative Example 1 was as shown in Figure 3 .

[0055] As can be seen from Figure 2 and Figure 3 , when the rework cleaning uses conventional cleaning parameters, water ripples will appear on the surface of the shell, affecting the appearance of the battery, and thus will also cause poor adhesion of the protective layer, while when the rework cleaning uses the cleaning parameters of the present application, the surface condition of the shell is good and no water ripples appear, the appearance is high, and the quality of the lithium ion battery is ensured.

[0056] Although the present application has been illustrated and described with reference to certain preferred embodiments thereof, it should be understood by those skilled in the art that the foregoing is a description of the present application in terms of preferred embodiments only and is not intended to limit the scope of the present application, which is defined by the appended claims. Various modifications to the preferred embodiments can be made by those skilled in the art without departing from the spirit and scope of the present application.

Claims

1. A method for protecting the appearance of a lithium-ion battery, characterized in that, Includes the following steps: Spray coating: A protective layer is formed by spraying a coating onto the surface of the lithium-ion battery; Inspection and post-processing: The appearance of the coated lithium-ion battery is inspected. If the inspection is qualified, the lithium-ion battery proceeds to the next process. If the inspection is unqualified, the lithium-ion battery is reworked by laser cleaning to remove the protective layer and the coating and inspection and post-processing steps are repeated until a lithium-ion battery with a qualified protective layer is obtained. The reworked laser cleaning has a cleaning power of 68-72%, a cleaning frequency of 235-245Hz, a cleaning time of 10.88-13.56 seconds, and a linear speed of 0.55-0.81m / min.

2. The method for protecting the appearance of a lithium-ion battery as described in claim 1, characterized in that, The cleaning power is 70-72%, and the cleaning frequency is 240-245Hz.

3. The method for protecting the appearance of a lithium-ion battery as described in claim 1, characterized in that, The cleaning time is 11.58-12.91 seconds, and the linear velocity is 0.61-0.74 m / min.

4. The method for protecting the appearance of a lithium-ion battery as described in claim 1, characterized in that, Before the first spraying step, a first laser cleaning step is also included, in which the cleaning power is 88-92% and the cleaning frequency is 275-285Hz.

5. The method for protecting the appearance of a lithium-ion battery as described in claim 4, characterized in that, In the initial laser cleaning step, the cleaning time is 5.43-8.47 seconds and the linear speed is 1.0-1.3 m / min.

6. The method for protecting the appearance of a lithium-ion battery as described in claim 1, characterized in that, The protective layer includes a photocurable material.

7. The method for protecting the appearance of a lithium-ion battery as described in claim 6, characterized in that, The spraying step is as follows: spraying the coating onto the surface of the lithium ions and curing it with ultraviolet light to form the protective layer.

8. A lithium-ion battery, characterized in that, The surface of the lithium-ion battery has a protective layer, which is obtained by the appearance protection method of the lithium-ion battery according to any one of claims 1-7.

9. A lithium-ion battery, characterized in that, The lithium-ion battery is subjected to external protection, which includes rework laser cleaning treatment. After the rework laser cleaning treatment, no water ripples will appear on the surface of the lithium-ion battery.

10. The lithium-ion battery as described in claim 9, characterized in that, The lithium-ion battery obtains a protective layer after the external protection, and the protective layer is free from defects such as spots, moiré rings, and uneven color.

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