A functional current collector production process for reducing residual stress in an electroplating process

Abstract

The present application relates to the technical field of functional current collector, and particularly relates to a production process of functional current collector for reducing residual stress in electroplating process. Specifically, the production process comprises the following steps: S1: performing magnetron sputtering treatment on a base film, sputtering target material to both surfaces of the base film, depositing a seed layer on the surface of the base film, and obtaining a composite foil; S2: performing laser impact treatment on the composite foil while performing water electroplating treatment on the composite foil, and obtaining a functional current collector. The present application introduces a laser impact treatment method in the water electroplating process, reduces the residual stress in the functional current collector, and improves the performance of the functional current collector in the battery through the reduction of the residual stress in the functional current collector, thereby improving the cycle life, energy density and safety and other key performances of the battery.

Description

Technical Field

[0001] This invention relates to the field of functional current collector technology, specifically a production process for functional current collectors that reduces residual stress during electroplating. Background Technology

[0002] With the rapid development of new energy and electronic technology, battery performance such as cycle life, safety, and energy density have become paramount in battery development. Current collectors, as a crucial component of a battery, collect the current generated by the battery's active materials to form a larger output current; their performance directly impacts the battery's cycle life, energy density, and safety.

[0003] Currently, most current collectors used in the battery industry are made of copper or aluminum foil. Current collectors made of pure metals have higher costs and lower quality, and their performance in battery safety is often unsatisfactory. Furthermore, pure metal current collectors have a high "dead weight," which is detrimental to improving battery energy density. For these reasons, composite conductive foil materials (functional current collectors) have begun to be widely used, showing significant advantages over traditional current collectors. Functional current collectors typically have a "sandwich" structure, with an inner polymer layer and metal conductive layers on both sides. The metal layer on the surface of the functional current collector is thinner, and the density of the polymer layer in the middle is significantly lower than that of pure metal, thus significantly reducing the weight of the current collector and improving the battery's energy density. In the event of thermal runaway, functional current collectors are easier to disconnect than traditional current collectors, thereby isolating the active material from the current collector and preventing further thermal runaway.

[0004] Although functional current collectors have the advantages of low cost and high safety, various internal stresses are often generated during the production process of functional current collectors. In addition, a large amount of heat is generated during battery cycling, causing the functional current collector to undergo volume changes. If the thermal shrinkage is too large, the functional current collector will have a large thermal deformation, which will seriously reduce the cycle life of the battery and also bring incalculable safety problems to the battery.

[0005] Therefore, it is essential and of great significance to develop a new process to reduce the residual stress of functional current collectors. Summary of the Invention

[0006] The purpose of this invention is to provide a production process for functional current collectors that reduces residual stress during electroplating, thereby solving the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A process for producing functional current collectors that reduces residual stress during electroplating includes the following steps:

[0009] S1: The base film is subjected to magnetron sputtering to sputter the target material onto both surfaces of the base film, and a seed layer is deposited on the surface of the base film to obtain a composite foil.

[0010] Furthermore, the base film is a PP film with a thickness of 3~5μm; the target material is pure copper with a purity of ≥99.99%.

[0011] Furthermore, the magnetron sputtering process is performed in a high-vacuum winding magnetron sputtering apparatus, with the following process parameters: vacuum degree of 5 × 10⁻⁶. -3 ~5×10 -2 Pa, working gas is Ar, gas flow rate is 50~150 sccm, sputtering power is 5~8KW, sputtering main roller cooling temperature is -35~0℃, target power is 10~15KW, and winding speed is 7~10m / min.

[0012] Furthermore, the thickness of the seed layer is 30~80nm.

[0013] S2: While performing electroplating on the composite foil, laser shock treatment is also applied to obtain a functional current collector.

[0014] Furthermore, the electroplating process is carried out on a DC temperature-controlled winding electroplating line, and the electroplating solution used includes the following concentration components: CuSO4 50~70g / L, HCl 40~90mg / L, H2SO4 120~150g / L, SPS (sodium polydithiopropane sulfonate) 0.01~0.04g / L, and the solvent is deionized water.

[0015] Furthermore, the process parameters for the electroplating treatment are as follows: electroplating temperature ≤26℃, winding speed 5~10m / min, sheet resistance ≤22μΩ, and current density gradually increasing from electroplating tank 1 to electroplating tank 8, with the current density variation range being 0~8A / dm. 3 .

[0016] Furthermore, the copper layer thickness obtained by the electroplating process is 1~3μm.

[0017] Furthermore, the specific process of the laser shock treatment is as follows: the composite foil is immersed in the electroplating solution, and a laser constraint layer and a laser absorption layer are sequentially set from top to bottom at a space of 8 cm above the composite foil; then, a laser is emitted by a pulsed laser, which passes through the laser constraint layer to impact the laser absorption layer, thereby acting on the composite foil.

[0018] Furthermore, the process parameters for the laser shock treatment are: laser wavelength of 1000~1600nm, pulse energy of 5~10J, and shock spot diameter of 2~5mm. In this invention, the residual stress of the composite foil is reduced and improved by controlling the laser wavelength. The laser wavelength intensity should not be too low, as a low wavelength will generate a smaller shock wave, resulting in less compressive stress on the composite foil and thus less impact on the residual stress. Conversely, the laser wavelength intensity should not be too high, as a high wavelength will generate a larger shock wave, leading to greater compressive stress on the composite foil. While reducing the original residual stress, it will also generate new residual stress within the composite foil.

[0019] Furthermore, the laser absorption layer is 5-10 cm away from the composite foil.

[0020] Furthermore, the laser confinement layer is made of transparent plexiglass with a thickness of 0.5~1cm.

[0021] The laser confinement layer is PMMA (polymethyl methacrylate) acrylic glass.

[0022] Furthermore, the laser absorption layer is a black organic thin film with a thickness of 150~250μm.

[0023] The laser absorption layer is specifically a black PU film.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention utilizes a laser shock treatment method during the electroplating process, employing a high power density (10) 9 A powerful laser beam with short pulses (on the order of nanoseconds) is used to laser-shock a black PU film. When the PU film absorbs energy, it rapidly vaporizes and ionizes into high-temperature plasma. During the laser action, the plasma continues to absorb energy and eventually expands and explodes between the PU film and PMMA plexiglass. The explosion generates a shock wave, which then propagates through the electroplating solution to the composite foil, generating a certain compressive stress on the composite foil and thus improving the overall residual stress distribution on the surface of the composite foil.

[0026] 2. This method does not add to the production process and can reduce residual stress without subsequent treatment;

[0027] 3. By reducing the residual stress inside the functional current collector, its performance in the battery can be improved, thereby improving the battery's cycle life, energy density, safety, and other key performance characteristics. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating a specific implementation of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] It should be noted that there are no special restrictions on the manufacturers from which all the raw materials involved in this invention can be purchased; they are all commercially available.

[0031] Example 1: A production process for functional current collectors that reduces residual stress during electroplating:

[0032] S1: Using a high-vacuum winding magnetron sputtering device, a pure copper target (99.99% purity) is sputtered onto both surfaces of a 4.5μm thick PP film. A seed layer with a thickness of 50nm is deposited on the surface of the PP film to obtain a composite foil.

[0033] The magnetron sputtering process parameters are as follows: the magnetron sputtering process is carried out in a high-vacuum winding magnetron sputtering equipment, and its process parameters are: vacuum degree of 5×10 -3 Pa, working gas is Ar, gas flow rate is 130 sccm, sputtering power is 6KW, sputtering main roller cooling temperature is -20℃, target power is 12KW, winding speed is 8m / min;

[0034] S2: The composite foil is placed on a DC temperature-controlled winding electroplating line for water electroplating treatment, and simultaneously subjected to laser shock treatment. A 1μm thick copper layer is electroplated and deposited on the composite foil to obtain a functional current collector.

[0035] The electroplating solution contains the following components at the following concentrations: CuSO4 60g / L, HCl 60mg / L, H2SO4 130g / L, SPS 0.02g / L, and deionized water as the solvent.

[0036] The parameters for the electroplating process are: plating temperature ≤ 26℃, winding speed 9m / min, sheet resistance ≤ 22μΩ, and current density gradually increasing from plating tank 1 to plating tank 8, with the current density in plating tank 1 being 0.8A / dm³. 2 The current density in electroplating tank 2 is 1.8 A / dm². 2 The current density in the three electroplating tanks is 2.8 A / dm³. 2 The current density of the four electroplating tanks is 3.8 A / dm³. 2 The current density of the five electroplating tanks is 4.8 A / dm³. 2 The current density of the 6 electroplating tanks is 5.8 A / dm³. 2The current density of the 7 electroplating tanks is 6.8 A / dm³. 2 The current density of the 8 electroplating tanks is 7.8 A / dm³. 2 .

[0037] Simultaneously with the electroplating process, laser shock treatment is applied. The specific process involves immersing the composite foil in the electroplating solution, and then, from top to bottom, placing a 0.8cm thick PMMA acrylic glass layer and a 200μm thick black PU film at a distance of 8cm above the composite foil. (Details follow...) Figure 1 As shown; then a laser is emitted by a pulsed laser, which passes through the PMMA organic glass to impact the black PU film, thereby acting on the composite foil;

[0038] The parameters for laser shock treatment are: laser wavelength of 1300nm, pulse energy of 6.5J, and shock spot diameter of 3mm.

[0039] Based on Example 1, Examples 2-3 and Comparative Examples 1-3 are added below, as detailed below:

[0040] Example 2: Example 2 is based on Example 1, with the following adjustment: the laser wavelength is 1100nm, while other processes remain unchanged.

[0041] Example 3: Example 3 is based on Example 1, with the following adjustment: the laser wavelength is 1500nm, while other processes remain unchanged.

[0042] Comparative Example 1: Comparative Example 1 is based on Example 1, with the following adjustment: the laser wavelength is 900nm, while other processes remain unchanged.

[0043] Comparative Example 2: Comparative Example 2 is based on Example 1, with the following adjustment: during the production process, the composite foil is not subjected to laser impact treatment, while other processes remain unchanged;

[0044] Comparative Example 3: Comparative Example 3 is based on Example 1, with the following adjustment: after electroplating, annealing is performed, while other processes remain unchanged.

[0045] Performance testing: Residual stress tests were conducted on the functional current collectors obtained in Examples 1-3 and Comparative Examples 1-3. The specific residual stress test results for each product are shown in Table 1 below:

[0046] Table 1

[0047]

[0048] Results Analysis: As can be seen from the data in Table 1 above, compared with the comparative examples and Comparative Example 2, the present invention greatly reduces the residual stress inside the functional current collector by performing laser shock treatment on it. Compared with Examples 1, 2-3 and Comparative Example 1, the present invention reduces the residual stress inside the functional current collector to the maximum extent by controlling the laser wavelength and using laser shock treatment. In Example 1, the residual stress of the functional current collector is the lowest, at 3 MPa, when the laser wavelength is 1300 nm. Compared with the comparative examples and Comparative Example 3, it is shown that the annealing method cannot further reduce the residual stress of the functional current collector.

[0049] In summary, this invention significantly reduces the internal residual stress of functional current collectors through laser shock treatment, which can improve key performance characteristics such as cycle life, energy density, and safety of batteries after they are subsequently fabricated.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A process for producing functional current collectors that reduces residual stress during electroplating, characterized in that: Specifically, the following steps are included: S1: The base film is subjected to magnetron sputtering to sputter the target material onto both surfaces of the base film, and a seed layer is deposited on the surface of the base film to obtain a composite foil. S2: While performing electroplating on the composite foil, laser shock treatment is also applied to obtain a functional current collector; The process parameters for the laser shock treatment are: laser wavelength of 1000~1600nm, pulse energy of 5~10J, and shock spot diameter of 2~5mm; The specific process of the laser shock treatment is as follows: the composite foil is immersed in the electroplating solution, and a laser constraint layer and a laser absorption layer are sequentially set from top to bottom at a space of 8cm above the composite foil; then, a laser is emitted by a pulsed laser, which passes through the laser constraint layer to impact the laser absorption layer, thereby acting on the composite foil. The laser confinement layer is a transparent organic glass with a thickness of 0.5~1cm; the laser absorption layer is a black organic thin film with a thickness of 150~250μm. The laser absorption layer is a black PU film; The electroplating process is carried out on a DC temperature-controlled winding electroplating line; the electroplating solution used includes the following concentration components: CuSO4 50~70g / L, HCl 40~90mg / L, H2SO4 120~150g / L, SPS 0.01~0.04g / L, and the solvent is deionized water.

2. The production process of a functional current collector for reducing residual stress during electroplating according to claim 1, characterized in that: The process parameters for the electroplating treatment are as follows: electroplating temperature ≤26℃, winding speed 5~10m / min, and current density gradually increasing from electroplating tank 1 to electroplating tank 8, with the current density variation range being 0~8A / dm. 2 .

3. The production process of a functional current collector for reducing residual stress during electroplating according to claim 1, characterized in that: The base film is a PP film with a thickness of 3~5μm; the target material is pure copper with a purity of ≥99.99%.

4. The production process of a functional current collector for reducing residual stress during electroplating according to claim 1, characterized in that: The magnetron sputtering process is performed in a high-vacuum winding magnetron sputtering apparatus, with the following process parameters: vacuum degree of 5 × 10⁻⁶. -3 ~5×10 -2 Pa, working gas is Ar, gas flow rate is 50~150 sccm, sputtering power is 5~8KW, sputtering main roller cooling temperature is -35~0℃, target power is 10~15KW, and winding speed is 7~10m / min.

5. The production process of a functional current collector for reducing residual stress during electroplating according to claim 1, characterized in that: In S1, the thickness of the seed layer is 30~80nm; in S2, the thickness of the copper layer obtained by the electroplating process is 1~3μm.

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