Welding method of negative electrode current collector of lithium battery and lithium battery

Abstract

This application discloses a welding method for a negative electrode current collector of a lithium battery and a lithium battery. The welding method for the negative electrode current collector of a lithium battery includes: pre-treating the negative electrode tabs of a cylindrical cell to make the negative electrode tabs on the same end of the cylindrical cell adhere to each other; fixing the cylindrical cell and the negative electrode current collector so that the surfaces of the negative electrode tabs of the cylindrical cell and the negative electrode current collector are adhered; the negative electrode current collector is a copper negative electrode current collector with a cleaned surface; and welding the negative electrode tabs and the negative electrode current collector using a green laser according to a preset welding speed, preset welding power, preset welding frequency, and preset welding trajectory. The welding method for the negative electrode current collector of this application can directly weld copper negative electrode current collectors, eliminating the nickel plating process of the negative electrode current collector, thus simplifying the welding process and reducing welding costs.

Description

TECHNICAL FIELD

[0001] The present application relates to the welding technology field of the current collector disc of a lithium battery, in particular to a welding method of a negative current collector disc of a lithium battery and a lithium battery. BACKGROUND

[0002] As a widely used battery type, the cylindrical lithium battery has a very broad development prospect. The negative current collector disc of the cylindrical lithium battery is generally made of copper material. The welding of the negative current collector disc is one of the key difficulties in the manufacturing process of the cylindrical lithium battery.

[0003] At present, the negative current collector disc is usually welded by laser welding. In the welding process of the negative current collector disc, the traditional laser welding is easy to cause the damage of the isolation film in the cylindrical battery cell due to the thin thickness of the negative current collector disc. In the existing welding method, the copper negative current collector disc is first plated with metal, and then a lower laser energy is used to increase the welding effect, for example, nickel plating treatment is performed on the copper negative electrode. However, the plating metal treatment on the copper negative electrode makes the overall welding process more complex and the cost is higher. SUMMARY

[0004] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a welding method of a negative current collector disc of a lithium battery, which can simplify the welding process and reduce the welding cost.

[0005] The present application also provides a lithium battery.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] The welding method of the negative current collector disc of the lithium battery according to the first aspect of the present application comprises:

[0008] The negative tabs of the cylindrical battery cell are pretreated to make the negative tabs on the same end of the cylindrical battery cell adhere to each other;

[0009] The cylindrical battery cell and the negative current collector disc are fixed so that the negative tabs of the cylindrical battery cell adhere to the surface of the negative current collector disc, and the negative current collector disc is a copper material negative current collector disc with a cleaned surface;

[0010] According to the preset welding speed, the preset welding power, the preset welding frequency and the preset welding trajectory, the negative tabs and the negative current collector disc are welded by green laser.

[0011] The welding method of the negative current collector disc of the lithium battery of the present application has the following advantages:

[0012] In the above-mentioned welding method for the negative electrode current collector of a lithium battery, firstly, the negative electrode tabs of the cylindrical cell are pre-treated to ensure that the negative electrode tabs on the same end of the cylindrical cell are in contact with each other. Then, the cylindrical cell is fixed to the negative electrode current collector, and the surfaces of the negative electrode tabs of the cylindrical cell and the negative electrode current collector are brought into contact to facilitate welding. This avoids incomplete welding between the negative electrode tabs and the negative electrode current collector, improving the welding quality between the negative electrode tabs of the cylindrical cell and the negative electrode current collector. After fixing the cylindrical cell and the negative electrode current collector, the welding is performed according to a preset welding speed, preset welding power, and preset welding frequency. The negative electrode tab and negative current collector are welded using a green laser along a preset welding trajectory. Since the negative current collector is made of cleaned copper, and copper absorbs green laser light much more readily than infrared laser light at room temperature, and the heat input of green laser light is much lower than that of near-infrared laser light to achieve the same weld penetration depth, welding directly onto the negative current collector with a green laser can avoid damaging the cylindrical battery cell. Therefore, there is no need to plate other metals onto the surface of the negative current collector. Thus, the above-mentioned welding method for the negative current collector of lithium batteries simplifies the welding process and reduces welding costs.

[0013] According to the welding method of the negative electrode current collector of the lithium battery according to the first aspect of the present application, the preset welding speed is V, which satisfies: 50mm / s≤V≤2000mm / s.

[0014] According to the welding method of the negative electrode current collector of the lithium battery according to the first aspect of the present application, the preset welding power is P, which satisfies: 50w≤P≤2000w.

[0015] According to the welding method of the negative electrode current collector of the lithium battery according to the first aspect of the present application, the preset welding trajectory is a spiral continuous curve trajectory, a spiral point trajectory, or a sine curve trajectory.

[0016] According to the welding method of the negative electrode current collector of the lithium battery according to the first aspect of the present application, the green laser is a nanosecond green laser or a continuous green laser, and the wavelength of the green laser is λ, which satisfies: 510nm≤λ≤540nm.

[0017] According to the welding method of the negative electrode current collector of the lithium battery according to the first aspect of the present application, the green laser is a nanosecond green laser, and the nanosecond green laser welds the negative electrode tab and the negative electrode current collector according to a preset pulse width, wherein the preset pulse width is W, which satisfies: 2ns≤W≤2000ns.

[0018] According to the welding method for the negative electrode current collector of a lithium battery according to the first aspect of this application, the pretreatment of the negative electrode tab of the cylindrical battery cell includes:

[0019] The negative tab of the cylindrical battery cell is either flattened or pressed flat.

[0020] According to the welding method of the negative electrode current collector of the lithium battery according to the first aspect of the present application, the negative electrode tab and the negative electrode current collector are welded according to a preset welding frequency, wherein the preset welding frequency is f, which satisfies: 100kHz≤f≤10000kHz.

[0021] The lithium battery according to the second aspect of this application is manufactured using the welding method described in any of the above schemes, and includes: a cylindrical cell, wherein the two ends of the cylindrical cell have a positive electrode tab and a negative electrode tab respectively; a current collector, wherein the current collector includes a positive current collector and a negative current collector, the negative electrode tab is attached to the surface of the negative current collector, and the negative electrode tab and the negative current collector are welded together by green laser.

[0022] The lithium battery of this application has the following advantages:

[0023] In the lithium battery of this application, the welding method of the negative current collector of the lithium battery described above can simplify the welding process and reduce the welding cost when welding the negative current collector and the negative electrode tab. Therefore, the manufacturing process of the lithium battery of this application is simple and the cost is low. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the welding method for the negative electrode current collector of the lithium battery in this application is shown.

[0026] Figure 2 A schematic diagram of the cylindrical battery cell in this application is shown.

[0027] Explanation of key component symbols:

[0028] 100 - Cylindrical cell; 110 - Tab;

[0029] 200-collector disk. Detailed Implementation

[0030] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0031] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0033] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0034] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0035] Reference Figure 1As shown, the welding method for the negative electrode current collector 200 of the lithium battery involved in this application embodiment includes:

[0036] S100: Pre-process the negative tab 110 of the cylindrical cell 100 so that the negative tabs 110 on the same end of the cylindrical cell are in contact with each other;

[0037] Specifically, according to Figure 2 As shown, the negative tab 110 of the cylindrical cell 100 is a multi-tab 110 or a full-tab 110, that is, there are multiple tabs 110. When welding the multiple tabs 110 to the negative current collector 200, the multiple tabs 110 are folded over to fit against the end surface of the cylindrical cell 100, and any two adjacent tabs 110 are tightly fitted without gaps, so that the multiple tabs can be welded to the current collector 200.

[0038] S200: Fix the cylindrical cell 100 and the negative current collector 200 so that the negative electrode tab 110 of the cylindrical cell 100 is in contact with the surface of the negative current collector 200. The negative current collector 200 is a negative current collector 200 made of cleaned copper material.

[0039] Specifically, during the process of fixing the cylindrical battery cell 100 and the negative current collector 200, the cylindrical battery cell 100 and the negative current collector 200 are fixed by a welding fixture. The welding fixture needs to be designed according to the structural characteristics of the cylindrical battery cell 100 and the negative current collector 200 and the welding requirements. By adjusting the fixture for fixing the negative current collector 200, the negative electrode tab 110 of the cylindrical battery cell 100 is made to fit with the surface of the negative current collector 200 to meet the welding requirements.

[0040] Although copper has relatively low reactivity, the surface of the copper manifold 200 is usually pre-cleaned to improve the soldering effect. For example, alcohol is used to wipe away dirt from the surface of the copper manifold 200.

[0041] Specifically, during the welding process, the negative electrode tab 110 of the cylindrical battery cell 100 needs to be welded to the negative electrode current collector 200 to achieve the welding of the negative electrode current collector 200, thereby realizing the conductive function of the negative electrode current collector 200.

[0042] S300: Based on the preset welding speed, preset welding power, preset welding frequency and preset welding trajectory, green laser is used to weld the negative electrode tab 110 and the negative electrode current collector 200.

[0043] Specifically, before welding, preset welding speed, preset welding power and preset welding frequency are input into the control system, and preset welding trajectory is selected to meet the welding requirements of negative electrode tab 110 and negative electrode current collector 200.

[0044] In the above-mentioned welding method for the negative electrode current collector 200 of the lithium battery, firstly, the negative electrode tabs 110 of the cylindrical cell 100 are pre-treated to make the negative electrode tabs 110 on the same end of the cylindrical cell fit together. Then, the cylindrical cell 100 and the negative electrode current collector 200 are fixed together, and the surfaces of the negative electrode tabs 110 of the cylindrical cell 100 and the negative electrode current collector 200 are made to fit together, so as to facilitate welding between the cylindrical cell 100 and the negative electrode current collector 200, avoid the phenomenon of incomplete welding between the negative electrode tabs 110 and the negative electrode current collector 200, and improve the welding quality between the negative electrode tabs 110 of the cylindrical cell 100 and the negative electrode current collector 200.

[0045] After fixing the cylindrical battery cell 100 and the negative current collector 200, the negative electrode tab 110 and the negative current collector 200 are welded using a green laser according to the preset welding speed, preset welding power, preset welding frequency, and preset welding trajectory. Since the negative current collector 200 is made of cleaned copper, and copper's absorption rate of green laser light at room temperature is much higher than its absorption rate of infrared laser light, and given the same weld penetration depth, the heat input of green laser light is much lower than that of near-infrared laser light, welding directly onto the negative current collector 200 with a green laser avoids damage to the cylindrical battery cell 100. Therefore, there is no need to plate other metals onto the surface of the negative current collector 200. This simplifies the welding process and reduces welding costs.

[0046] Specifically, the preset welding speed is V, which satisfies: 50mm / s≤V≤2000mm / s.

[0047] Specifically, the welding speed is the length of weld completed per unit time. The preset welding speed V can be 50mm / s, 100mm / s, 500mm / s, 1000mm / s, 1500mm / s, 2000mm / s, etc.

[0048] In this embodiment, if V < 50 mm / s, the welding speed will be too slow, increasing the residence time of the high-temperature welding on the negative electrode current collector 200, thus increasing the width of the heat-affected zone and resulting in an excessively wide weld. This not only affects the aesthetics of the weld but also increases the deformation of the negative electrode current collector 200. If V > 2000 mm / s, the welding speed will be too fast, resulting in insufficient molten pool temperature and shallow weld penetration, which can easily lead to defects such as incomplete penetration, lack of fusion, poor weld formation, and cold welds. When 5 mm / s ≤ V ≤ 2000 mm / s, both the deformation of the negative electrode current collector 200 and the welding quality can be reduced.

[0049] Specifically, the preset welding power is P, which satisfies: 50w≤P≤2000w.

[0050] Specifically, welding power is the energy output by welding equipment per unit time. The preset welding power P can be 50W, 100W, 500W, 1000W, 1500W, 2000W, etc.

[0051] In this embodiment, if P < 50W, the welding power will be too low, resulting in insufficient output energy during the welding process. This will further lead to shallow weld penetration, insufficient weld strength, and poor weld quality. If P > 2000W, the welding power will be too high, resulting in excessive output energy during the welding process. This may cause deformation of the negative current collector 200, or even burn-through. When 50W ≤ P ≤ 2000W, the output energy during the welding process can be guaranteed to meet the welding requirements, ensuring both welding strength and quality, while also preventing deformation of the negative current collector 200 and avoiding burn-through.

[0052] Specifically, the preset welding trajectory is a spiral continuous curve trajectory, a spiral point trajectory, or a sine curve trajectory.

[0053] Specifically, during welding, there should be no welding gap between any two adjacent weld points to improve welding quality. Furthermore, during welding, the welding trajectory can be either a lattice of dots or a continuous line.

[0054] In this embodiment, when the preset welding trajectory is a spiral continuous curve trajectory, a spiral point trajectory, or a sine curve trajectory, the weld length and welding area between the negative electrode tab 110 and the negative electrode current collector 200 can be increased, thereby strengthening the welding strength between the negative electrode tab 110 and the negative electrode current collector 200.

[0055] Specifically, the green laser is a nanosecond green laser or a continuous green laser, and the wavelength of the green laser is λ, which satisfies: 510nm≤λ≤540nm.

[0056] Specifically, the wavelength λ of green laser can be 510nm, 520nm, 530nm, 540nm, etc.

[0057] In this embodiment, green laser welding features low heat input, low reflectivity, high absorptivity, and minimal heat-affected zone, resulting in a stable welding process. This avoids damage to the internal structure of the cylindrical cell 100, prevents spatter, and minimizes impact on battery performance. Nanosecond lasers can generate nanosecond-level pulses, continuously charging and releasing energy as pulsed laser light over a period of time, resulting in a lattice-like welding trajectory. Continuous lasers can continuously output laser beams, and these beams are continuous and stable, resulting in a continuous linear welding trajectory.

[0058] Furthermore, in this embodiment, if the wavelength λ of the green laser is less than 510 nm, the laser wavelength will be too short, making it more prone to vaporization and material damage. If the wavelength λ of the green laser is greater than 540 nm, the laser wavelength will be too long, increasing the weld width and affecting the weld aesthetics and welding quality. When the wavelength λ of the green laser satisfies the condition 510 nm ≤ λ ≤ 540 nm, it can both reduce material damage and improve welding quality.

[0059] Specifically, in this embodiment, the green laser is a nanosecond green laser. The nanosecond green laser welds the negative electrode tab 110 and the negative electrode current collector 200 according to a preset pulse width. The preset pulse width is W, which satisfies: 2ns≤W≤2000ns.

[0060] In this embodiment, the nanosecond green laser has the advantage of high energy density, so its output energy is more concentrated and powerful, which enables the negative electrode tab 110 and the negative electrode current collector 200 to have better welding quality.

[0061] Specifically, the preset pulse width W can be 2ns, 50ns, 500ns, 1000ns, 1500ns, 2000ns, etc.

[0062] In this embodiment, if W < 2ns, the output energy density of the nanosecond green laser will be too low, resulting in a shallow weld penetration, insufficient weld strength, and poor weld quality. If W > 2000ns, the output energy density of the nanosecond green laser will be too high, potentially causing deformation of the negative electrode current collector 200 or even burn-through. When 2ns ≤ W ≤ 2000ns, the output energy during the welding process can be guaranteed to meet the welding requirements, ensuring both weld strength and quality while preventing deformation of the negative electrode current collector 200 and avoiding burn-through.

[0063] Reference Figure 2 As shown, in the welding method of the negative electrode current collector 200 of the lithium battery, the pretreatment of the negative electrode tab 110 of the cylindrical cell 100 includes:

[0064] The negative tab 110 of the cylindrical battery cell 100 is either flattened or pressed flat.

[0065] In this embodiment, during the pretreatment of the negative electrode tab 110 of the cylindrical cell 100, the negative electrode tab 110 is either flattened or pressed flat to ensure a tight fit between any two adjacent negative electrode tabs 110 without gaps. Simultaneously, the flatness of the welding surface between the negative electrode tab 110 and the negative current collector 200 meets the welding requirements, allowing multiple negative electrode tabs 110 to be welded to the negative current collector 200. This ensures the welding quality between the negative electrode tabs 110 and the negative current collector 200, thereby guaranteeing the product quality of the lithium battery.

[0066] Specifically, the negative electrode tab 110 and the negative electrode current collector 200 are welded according to the preset welding frequency f, which satisfies: 200kHz≤f≤10000kHz.

[0067] Specifically, in some embodiments, the laser used to emit green light is a conventional laser, in which the pulse width is inversely proportional to the welding frequency. In other embodiments, the laser used to emit green light is a MOPA laser, in which the pulse width and welding frequency can be modulated separately, meaning the welding frequency can be adjusted independently.

[0068] Specifically, the influence of welding frequency on welding strength is mainly reflected in the vibration amplitude. The higher the frequency, the greater the vibration amplitude of the welding head. The preset welding frequency f can be 200kHz, 500kHz, 2000kHz, 5000kHz, 8000kHz, 10000kHz, etc.

[0069] In this embodiment, if f < 100kHz, the welding frequency will be too low. A low frequency leads to excessively flat vibration amplitude, resulting in slow heat transfer and a slow welding speed. This increases the residence time of the high-temperature welding on the negative electrode current collector 200, increasing the width of the heat-affected zone and causing an excessively wide weld. This not only affects the aesthetics of the weld but also increases the deformation of the negative electrode current collector 200. If f > 10000kHz, the welding frequency will be too high. An excessively high frequency leads to excessive vibration amplitude during the welding process, resulting in an excessively fast welding speed. This results in insufficient molten pool temperature, leading to shallow weld penetration and defects such as incomplete penetration, lack of fusion, poor weld formation, and cold welds. When 200kHz ≤ f ≤ 10000kHz, both the deformation of the negative electrode current collector 200 and the welding quality can be reduced.

[0070] Reference Figure 2 As shown, the lithium battery involved in the embodiments of this application is manufactured using the welding method described in any of the above schemes. The lithium battery includes: a cylindrical cell 100 and a current collector 200.

[0071] Specifically, the cylindrical battery cell 100 has a positive tab 110 and a negative tab 110 at its two ends; the current collector 200 includes a positive current collector 200 and a negative current collector 200, the negative tab 110 is attached to the surface of the negative current collector 200, and the negative tab 110 and the negative current collector 200 are welded together by green laser.

[0072] In the lithium battery of this application, the welding process of welding the negative current collector 200 and the negative electrode tab 110 by the welding method of the negative current collector 200 of the lithium battery described above can be simplified and the welding cost can be reduced. Therefore, the manufacturing process of the lithium battery of this application is simple and the cost is low.

[0073] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A welding method for the negative electrode current collector of a lithium battery, characterized in that, include: The negative tabs of the cylindrical battery cell are pre-treated to ensure that the negative tabs on the same end of the cylindrical battery cell fit together. A cylindrical battery cell is fixed to a negative current collector, such that the negative tab of the cylindrical battery cell is in contact with the surface of the negative current collector. The negative current collector is a copper current collector with a cleaned surface and is not plated with metal. According to the preset welding speed, preset welding power, preset welding frequency and preset welding trajectory, green laser is used to weld the negative electrode tab and the negative electrode current collector. The preset welding power is P, which satisfies: 50w≤P≤500w; The laser that emits green light is a MOPA laser; The green laser is a nanosecond green laser, and the wavelength of the green laser is λ, which satisfies: 510nm≤λ≤540nm; The nanosecond green laser welds the negative electrode tab and the negative electrode current collector according to a preset pulse width, wherein the preset pulse width is W, which satisfies: 2ns≤W≤2000ns; The negative electrode tab and the negative electrode current collector are welded according to a preset welding frequency, wherein the preset welding frequency is f, and satisfies: 100kHz≤f≤10000kHz.

2. The welding method for the negative electrode current collector of a lithium battery according to claim 1, characterized in that, The preset welding speed is V, which satisfies the following condition: 50mm / s≤V≤2000mm / s.

3. The welding method for the negative electrode current collector of a lithium battery according to claim 1, characterized in that, The preset welding trajectory is a spiral continuous curve trajectory, a spiral point trajectory, or a sine curve trajectory.

4. The welding method for the negative electrode current collector of a lithium battery according to claim 1, characterized in that, Pre-treatment of the negative tab of cylindrical battery cells includes: The negative tab of the cylindrical battery cell is either flattened or pressed flat.

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