Functional current collector surface modification method

Abstract

The invention relates to the technical field of current collector surface treatment, and particularly discloses a functional current collector surface modification method which is characterized in that after an aluminum-based film is preheated, magnesium powder is subjected to laser cladding on the surface of the aluminum-based film to form a magnesium-aluminum alloy layer, so that the purpose of modifying the surface of the functional current collector is achieved. The magnesium-aluminum alloy layer subjected to laser cladding is firmly combined with the aluminum-based film, the overall corrosion resistance and oxidation resistance of the material are improved, local modification of specific parts of the surface of the current collector is achieved by accurately controlling laser beams through the laser cladding technology, different requirements of different parts for material performance can be met, and the service life of the current collector is prolonged. And materials and cost can be saved, and production efficiency and economic benefits can be further improved after the device is combined with an automatic production line.

Description

Technical Field

[0001] The present invention relates to the technical field of current collector surface treatment, and specifically to a method for surface modification of a functional current collector. Background Art

[0002] In the production of functional aluminum current collectors, the outer surfaces of the aluminum films produced by the first-generation equipment (multiple film formations) and the second-generation equipment (one-time double-sided film formation) are granular: the outer surface of the aluminum layer has a granular morphology formed by the arrangement of aluminum metal particles. The vertical projection length of the particles is 5 - 500 nm, and the spacing is 0 - 300 nm. Its structure can be composed of several types such as sheet-like and columnar, and the arrangement on the outer surface of the aluminum layer can be regular or irregular, and there are gaps between these arrangements.

[0003] During the immersion in the electrolyte, some organic solvents may chemically react with aluminum, destroying the passivation film on the aluminum surface, and thus accelerating corrosion. Taking carbonate solvents as an example, under certain conditions, they may react with aluminum, dissolving the oxide film on the aluminum surface, exposing the fresh aluminum surface, increasing the corrosion sensitivity, and the aluminum layer then delaminates from the PET substrate, resulting in a reduction in the effective area of the aluminum current collector and an increase in resistance, affecting the performance and lifespan of the battery. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for surface modification of a functional current collector to improve the wear resistance and corrosion resistance of the material, and solve the problems that the aluminum film on the surface of the current collector is easily corroded, resulting in a reduction in the effective area and an increase in resistance.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for surface modification of a functional current collector, specifically:

[0007] Step 1: Pre-clean the surface of the aluminum-based film to wash away the oil and impurities on the surface;

[0008] Step 2: Perform preheating treatment on the aluminum-based film after cleaning;

[0009] Step 3: Use laser cladding to clad magnesium powder on the surface of the aluminum-based film;

[0010] Step 4: Perform cooling treatment after laser cladding to obtain a surface-modified functional current collector.

[0011] Selecting a base film with a larger width can improve production efficiency and reduce the number of splicing times. Based on the current situation, a 1650 mm wide aluminum-based film is commonly used.

[0012] As a limitation of the present invention, the preheating treatment and laser cladding are carried out in a vacuum environment to keep the environment clean, and the environmental humidity is controlled at 40 - 60%.

[0013] The preheating treatment and laser cladding are carried out under vacuum to keep the heating environment clean and minimize pollutants that may adhere to the surface of the base film, hinder the tight bonding between the magnesium alloy and the base film, and reduce the bonding strength. The environmental humidity should also be controlled within a certain range. If the humidity is too high, moisture may condense on the surface of the base film, affecting the bonding between the magnesium alloy and the base film. If the humidity is too low, static electricity may be generated on the base film, adsorbing impurities, which is also not conducive to bonding.

[0014] As a limitation of the present invention, an infrared heating device is used during the preheating treatment. The distance between the infrared heating device and the surface of the aluminum base film is 10 - 30 cm, the film feeding speed is 1 - 5 m / min, the preheating temperature is 50 - 120 °C, and the temperature is increased step by step at a rate of 10 °C / min. During the heating process, the temperature uniformity on the surface of the base film is ensured to be within ±5 °C. The infrared heating working device is always on and stops heating until the laser cladding is completed.

[0015] If the distance of the infrared heating device is too close, it may cause local overheating of the base film. If the distance is too far, it will lead to low heating efficiency and unable to reach the expected preheating temperature. The aluminum film moves at a low speed to prevent baking at a fixed position for a long time, which may cause the film to deform due to heat or even break. If the preheating temperature of the base film is too low, it cannot effectively improve the activity of the film and is difficult to achieve the purpose of enhancing the bonding. If the temperature is too high, it may cause changes in the performance of the base film. Maintaining for a period of time at each stepped temperature point can make the temperatures of all parts in the system evenly distributed, ensure the stability and consistency of the overall temperature, is conducive to improving the repeatability of the process and the stability of product quality, enables the object or system to gradually adapt to temperature changes, and avoids problems such as excessive thermal stress, thermal deformation, and thermal fatigue caused by a sharp rise in temperature, which is very important for protecting the performance and lifespan of the equipment and materials. During the heating process, the temperature on the surface of the base film needs to be ensured to be uniform. A large temperature difference will cause inconsistent expansion degrees of different parts of the base film, thereby affecting the adhesion effect of the magnesium alloy and resulting in uneven bonding force problems. The temperature uniformity can be controlled by adjusting the power distribution, heating distance of the infrared heating device, and increasing the temperature monitoring points. The infrared heating device should maintain an appropriate distance from the base film. If the distance is too close, it may cause local overheating of the base film. If the distance is too far, it will lead to low heating efficiency and unable to reach the expected preheating temperature.

[0016] As a limitation of the present invention, the particle size of the magnesium powder used during laser cladding is 45 - 105 μm, the purity is ≥99%, the sphericity is 0.8 - 1, and the Hall flow rate is 2 - 5 g / min.

[0017] When selecting the powder particle size for laser cladding, finer powders have a larger specific surface area, can better absorb laser energy, have a fast melting speed, and can obtain a finer-grained cladding layer structure. However, overly fine powders are prone to agglomeration, which affects the uniformity of powder feeding. Coarser powders, on the other hand, have better fluidity, are not easily agglomerated, and can improve the cladding efficiency to a certain extent. However, if the particle size is too coarse, it will lead to incomplete melting and affect the quality of the cladding layer. The purity of the powder should be as high as possible to reduce the influence of impurity elements on the properties of the cladding layer. Impurity elements may change the microstructure and phase composition of the cladding layer, reducing its corrosion resistance and wear resistance. Powders with good sphericity have better fluidity and spreading properties, which are beneficial to forming a uniform cladding layer during the laser cladding process. Good fluidity is the key to stable and uniform powder feeding during the laser cladding process.

[0018] As a limitation of the present invention, in step 3, the process parameters during laser cladding are as follows: the laser power is 1000 - 3000 W, the spot diameter is 2 - 5 mm, the scanning speed is 10 - 20 m / min, the powder feeding rate is 2 - 5 g / min, and the argon gas flow rate is 5 - 10 L / min.

[0019] During the laser cladding process, select a suitable laser cladding device and adjust the laser power, spot size, and scanning speed according to the material properties of the PET aluminum-based film and magnesium. A lower laser power may result in incomplete melting of the powder and insufficient bonding force of the cladding layer, while an excessive laser power may cause the cladding layer to overheat, generating defects such as cracks and pores, and at the same time causing significant thermal damage to the PET aluminum-based film. A slower scanning speed during the laser speed can allow the powder to melt fully and obtain a thicker cladding layer, but it will reduce the production efficiency and is prone to overheating of the cladding layer. A faster scanning speed can improve the production efficiency, but may result in uneven cladding layer thickness and decreased bonding force. A smaller spot diameter can concentrate the laser energy, which is beneficial to improving the hardness and wear resistance of the cladding layer, but the cladding width is relatively narrow and multiple scans are required to cover a large area. A larger spot diameter can obtain a wider cladding layer, but the laser energy distribution is relatively dispersed, which may affect the quality of the cladding layer. The powder feeding rate should be matched with the laser power and scanning speed. An overly fast powder feeding rate will cause powder accumulation and incomplete melting, affecting the quality of the cladding layer, while an overly slow powder feeding rate will result in uneven cladding layer thickness and even powder shortage.

[0020] As a limitation of the present invention, in step 4, the cooling treatment is carried out by installing a cooling drum, the cooling temperature is 0 - 10 °C, and the cooling temperature is adjusted according to the surface temperature of the film. After cooling, the surface temperature of the film is 18 - 25 °C.

[0021] As a limitation of the present invention, the aluminum-based film used is a DC-etched aluminum-based film, and the preparation method is as follows:

[0022] The pre-treated aluminum-based film is immersed in a pre-etching solution, with the solution temperature controlled at 50 - 60°C and the current density at 45 - 55 mA / cm 2 , and it is pre-etched for 5 - 15 s. After pre-etching, the aluminum-based film is taken out and immersed in a cyclodextrin acid solution, with the solution temperature controlled at 45 - 55°C and the current density at 1 mA / cm 2 , and etched for 60 - 70 s. After etching is completed, it is taken out and dried to obtain a direct current etched aluminum-based film.

[0023] As a limitation of the present invention, the pre-etching solution contains hydrochloric acid, sulfuric acid, and sodium sulfite. The concentration of hydrochloric acid in the pre-etching solution is 0.8 - 1.2 mol / L, the concentration of sulfuric acid is 0.8 - 1.2 mol / L, and the concentration of sodium sulfite is 0.4 - 0.6 mol / L.

[0024] As a limitation of the present invention, the concentration of cyclodextrin in the cyclodextrin acid solution is 0.4 - 0.5 g / L.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The present invention uses laser cladding to clad a layer of magnesium alloy on the surface of the aluminum-based film of the current collector, and through good metallurgical bonding, the aluminum-based film is combined with the cladding material. This metallurgical bonding interface can effectively transfer stress, avoid coating peeling or flaking, ensure high bonding strength between the magnesium element and the current collector matrix, and improve the overall stability and reliability of the material; forming a dense magnesium-aluminum coating structure also effectively blocks the erosion of oxygen, moisture and other media in the external environment on the current collector, improves the corrosion resistance and oxidation resistance of the material, and extends the service life of the material.

[0027] The laser cladding method adopted by the present invention has the characteristics of high energy density, fast heating and cooling rates, so that the heat affected zone of the current collector matrix during the cladding process is small; by precisely controlling the process parameters of laser cladding, such as laser power, scanning speed, powder feeding rate, etc., the composition and microstructure of the magnesium alloy layer can be accurately controlled, so as to customize alloy layers with different magnesium-aluminum ratios according to specific performance requirements and achieve precise regulation of material properties; by precisely controlling the scanning path and action area of the laser beam, local modification of specific parts on the surface of the current collector is realized, which can not only meet the different requirements of different parts for material properties, but also save materials and costs, and avoid unnecessary treatment of the entire current collector; in addition, the laser cladding technology also has a high processing speed and automation degree, which can be combined with an automated production line to achieve large-scale and high-efficiency production, improving production efficiency and economic benefits.

[0028] The present invention uses a DC etching method to treat the surface of the aluminum-based film, improving the interfacial properties of the current collector, facilitating the adhesion of the alloy layer during laser cladding treatment, improving the electrochemical performance of the current collector, and enhancing the overall stability and reliability of the material. Detailed implementation manners

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Composite aluminum finished base film (6μm PET film + 1μm aluminum layer on each side, width 1650mm), magnesium powder (purity: 99%) 。

[0031] Embodiment 1: A method for surface modification of a functional current collector, specifically:

[0032] Step 1: Prepare materials

[0033] Prepare a composite aluminum finished base film with sufficient length (width 1650mm) and a clean surface without oil stains, impurities, etc., and prepare magnesium powder as the cladding material. The particle size of the magnesium powder is 45 - 75μm, the sphericity is 1, and the Hall flow rate is 3.5g / min.

[0034] Step 2: Load materials

[0035] Load the film roll and sufficient magnesium powder, evacuate in a vacuum winding machine, click the evacuation button on the screen, observe the vacuum value and record it, and reach a background vacuum of 5.0E-3pa.

[0036] Step 3: Set parameters

[0037] Set the distance between the infrared heating device and the surface of the aluminum-based film to 20cm, the temperature of the cold drum for post-treatment to 5°C, the cryogenic temperature to -140°C, the temperature of the film after cooling to 22°C, the tension for winding to 180N, the tension for unwinding to 160N, control the environmental humidity at 45%, wait for the vacuum to reach the set vacuum degree of 5.0E-3pa, and turn on the automatic process preheating mode for preheating and cladding, etc.

[0038] Step 4: Start preheating

[0039] Gradually increase the infrared heating power in a stepped manner to 1000W, turn on the low-speed running of the base film at 1m / min, and the preheating temperature of the aluminum-based film gradually rises to 70°C. Adjust the laser power to 1000W, the scanning speed to 10m / min, the spot diameter to 2mm, the powder feeding speed to 2g / min, and the protective gas to 5L / min.

[0040] Step 5: Laser cladding

[0041] When all preheating reaches the cladding set standard, start to increase the speed of the base film by 15 m / min, observe the magnesium powder cladding process, and manually adjust the process parameters individually according to the actual on-site situation to change the cladding effect. When the winding speed reaches the process set speed, start cladding, and record parameters such as laser power, laser speed, and spot size. After the cladding is completed at this time, the post-treatment cooling is also working synchronously.

[0042] Step 6: Rewinding

[0043] When the set reel diameter and meterage parameters are reached, the equipment automatically stops; when the winding automatically stops, the laser equipment automatically stops, the infrared equipment automatically stops, etc.; click the "Inflate" button on the control panel, automatically stop vacuum pumping, and automatically deflate; after the vacuum in the vacuum chamber is exhausted, press and hold the "Interlock protection" and "Open" buttons on the control panel at the same time to open the vacuum chamber, obtain the surface-modified functional current collector, and record the rewinding meterage, out-of-warehouse time, etc.

[0044] Example 2: A method for surface modification of a functional current collector, specifically as follows:

[0045] Step 1: Prepare materials

[0046] Prepare a composite aluminum finished base film with a sufficient length (width 1650 mm) and a clean surface without oil stains, impurities, etc., and prepare magnesium powder as the cladding material. The particle size of the magnesium powder is 45 - 75 μm, the sphericity is 1, and the Hall flow rate is 3.5 g / min.

[0047] Step 2: Loading

[0048] Load the film roll and sufficient magnesium powder, evacuate in a vacuum winding machine, click the air extraction button on the screen, observe the vacuum value, and record it until the background vacuum reaches 5.0E-3 pa.

[0049] Step 3: Parameter setting

[0050] Set the distance between the infrared heating device and the surface of the aluminum base film to 20 cm, the temperature of the cold drum for post-treatment to 5°C, the cryogenic temperature to -140°C, the temperature of the cooled film to 22°C, the tension for winding to 180 N, the tension for unwinding to 160 N, control the environmental humidity at 45%, wait for the vacuum to reach the set vacuum degree of 5.0E-3 pa, and turn on the automatic process preheating mode for preheating and cladding, etc.

[0051] Step 4: Preheating start

[0052] Gradually increase the infrared heating power in a stepped manner to 1000 W, start the low-speed running of the base film at a speed of 1 m / min, and gradually increase the preheating temperature of the aluminum base film to 70 °C. Adjust the laser power to 1500 W, the scanning speed to 13 m / min, the spot diameter to 2.5 mm, the powder feeding speed to 2.5 g / min, and the shielding gas to 5 L / min.

[0053] Step 5: Laser cladding

[0054] When all preheating reaches the cladding set standard, start to increase the speed of the base film to 15 m / min, observe the magnesium powder cladding process, and manually adjust the process parameters individually according to the actual on-site situation to change the cladding effect. When the winding speed reaches the process set speed, start cladding, and record parameters such as laser power, laser speed, and spot size. After the cladding is completed at this time, the post-treatment cooling is also working synchronously.

[0055] Step 6: Rewinding

[0056] When the set reel diameter and meterage parameters are reached, the equipment automatically stops; when the winding automatically stops, the laser equipment automatically stops, the infrared equipment automatically stops, etc.; click the "Inflate" button on the control panel, automatically stop vacuum pumping, and automatically deflate; after the vacuum in the vacuum chamber is exhausted, press and hold the "Interlock protection" and "Open" buttons on the control panel at the same time to open the vacuum chamber, obtain the surface-modified functional current collector, and record the rewinding meterage, out-of-chamber time, etc.

[0057] Example 3: A method for surface modification of a functional current collector, specifically:

[0058] Step 1: Prepare materials

[0059] Prepare a composite aluminum finished base film with a sufficient length (width 1650 mm) and a clean surface without oil stains, impurities, etc., and prepare magnesium powder as the cladding material. The particle size of the magnesium powder is 45 - 75 μm, the sphericity is 1, and the Hall flow rate is 3.5 g / min.

[0060] Step 2: Loading

[0061] Load the film roll and sufficient magnesium powder, evacuate in a vacuum winding machine, click the air extraction button on the screen, observe the vacuum value, and record it until the background vacuum reaches 5.0E-3 pa.

[0062] Step 3: Parameter setting

[0063] Set the distance between the infrared heating device and the surface of the aluminum base film to 20 cm, the temperature of the cold drum for post-treatment to 5 °C, the cryogenic temperature to -140 °C, the temperature of the cooled film to 22 °C, the tension for winding to 180 N, the tension for unwinding to 160 N, control the environmental humidity at 45%, wait for the vacuum to reach the set vacuum degree of 5.0E-3 pa, and turn on the automatic process preheating mode for preheating, cladding, etc.

[0064] Step 4: Preheating starts

[0065] Gradually increase the infrared heating power in a stepped manner to 1000 W, start the low-speed running of the base film at a speed of 1 m / min, and the preheating temperature of the aluminum base film gradually rises to 70 °C. Adjust the laser power to 2000 W, the scanning speed to 16 m / min, the spot diameter to 3 mm, the powder feeding speed to 3 g / min, and the protective gas to 5 L / min.

[0066] Step 5: Laser cladding

[0067] When all preheating reaches the cladding set standard, start to increase the speed of the base film to 15 m / min, observe the magnesium powder cladding process, and manually adjust the process parameters individually according to the actual on-site situation to change the cladding effect. When the winding speed reaches the process set speed, start cladding, and record parameters such as laser power, laser speed, and spot size. After the cladding is completed at this time, the post-treatment cooling also works synchronously.

[0068] Step 6: Rewinding

[0069] When the set reel diameter and meterage parameters are reached, the equipment automatically stops; when the winding automatically stops, the laser equipment automatically stops, the infrared equipment automatically stops, etc.; click the "Inflate" button on the control panel, automatically stop vacuum pumping, and automatically deflate; after the vacuum in the vacuum chamber is exhausted, press and hold the "Interlock protection" and "Open" buttons on the control panel at the same time to open the vacuum chamber, obtain the surface-modified functional current collector, and record the rewinding meterage, out-of-chamber time, etc.

[0070] Example 4: A method for surface modification of a functional current collector, specifically:

[0071] Step 1: Material preparation

[0072] Prepare a composite aluminum finished base film with a sufficient length (width 1650 mm) and a clean surface without oil stains, impurities, etc., and prepare magnesium powder as the cladding material. The particle size of the magnesium powder is 45 - 75 μm, the sphericity is 1, and the Hall flow rate is 3.5 g / min.

[0073] Step 2: Loading

[0074] Load the film roll and sufficient magnesium powder, evacuate in a vacuum winding machine, click the air extraction button on the screen, observe the vacuum value, and record it until the base vacuum reaches 5.0E-3 pa.

[0075] Step 3: Parameter setting

[0076] Set the distance between the infrared heating device and the surface of the aluminum-based film to 20 cm, the temperature of the cold drum for post-treatment to 5 °C, the cryogenic temperature to -140 °C, the temperature of the cooled film to 22 °C, the winding tension to 180 N, the unwinding tension to 160 N, control the environmental humidity at 45%, wait for the vacuum to reach the set vacuum degree of 5.0E-3 pa, and turn on the automatic process preheating mode for preheating cladding, etc.

[0077] Step 4: Preheating starts

[0078] Gradually increase the infrared heating power in a stepped manner to 1000 W, turn on the low-speed running of the base film at a speed of 1 m / min, and the preheating temperature of the aluminum-based film gradually rises to 70 °C. Adjust the laser power to 2500 W, the scanning speed to 18 m / min, the spot diameter to 4 mm, the powder feeding speed to 4 g / min, and the shielding gas to 5 L / min.

[0079] Step 5: Laser cladding

[0080] When all preheating reaches the cladding set standard, start to increase the speed of the base film to 15 m / min, observe the magnesium powder cladding process, and manually adjust the process parameters individually according to the actual on-site situation to change the cladding effect. When the winding speed reaches the process set speed, start cladding, and record parameters such as laser power, laser speed, and spot size. After the cladding is completed at this time, the post-treatment cooling is also working synchronously.

[0081] Step 6: Winding

[0082] When the set reel diameter and meterage parameters are reached, the equipment automatically stops; when the winding automatically stops, the laser equipment automatically stops, and the infrared equipment automatically stops, etc.; click the "Inflate" button on the control panel, automatically stop vacuum pumping and automatically release the gas; after the vacuum in the vacuum chamber is exhausted, simultaneously press the "Interlock protection" and "Open" buttons on the control panel to open the vacuum chamber, obtain the surface-modified functional current collector, and record the winding meterage, out-of-chamber time, etc.

[0083] Example 5: A method for surface modification of a functional current collector, specifically:

[0084] Step 1: Prepare materials

[0085] Prepare a composite aluminum finished base film with a sufficient length (width 1650 mm) and a clean surface without oil stains, impurities, etc., and prepare magnesium powder as the cladding material. The particle size of the magnesium powder is 45 - 75 μm, the sphericity is 1, and the Hall flow rate is 3.5 g / min.

[0086] Step 2: Loading

[0087] Load the film roll and sufficient magnesium powder, evacuate in the vacuum winding machine, click the air extraction button on the screen, observe the vacuum value, record it, and reach the background vacuum of 5.0E-3 pa.

[0088] Step 3: Parameter Setting

[0089] Set the distance between the infrared heating device and the surface of the aluminum-based film to 20 cm, the temperature of the cold drum for post-treatment to 5 °C, the cryogenic temperature to -140 °C, the temperature of the cooled film to 22 °C, the winding tension to 180 N, the unwinding tension to 160 N, control the ambient humidity at 45%, wait for the vacuum to reach the set vacuum degree of 5.0E-3 pa, turn on the automatic process preheating mode, and preheat the cladding, etc.

[0090] Step 4: Start Preheating

[0091] Gradually increase the infrared heating power in a stepped manner to 1000 W, turn on the low-speed running of the base film at a speed of 1 m / min, and the preheating temperature of the aluminum-based film gradually rises to 70 °C. Adjust the laser power to 3000 W, the scanning speed to 20 m / min, the spot diameter to 5 mm, the powder feeding speed to 5 g / min, and the shielding gas to 5 L / min.

[0092] Step 5: Laser Cladding

[0093] When all preheating reaches the cladding set standard, start to increase the speed of the base film to 15 m / min, observe the magnesium powder cladding process, and manually adjust the process parameters individually according to the actual on-site situation to change the cladding effect. When the winding speed reaches the process set speed, start cladding, and record parameters such as laser power, laser speed, spot size, etc. At this time, after the cladding is completed, the post-treatment cooling is also working synchronously.

[0094] Step 6: Winding

[0095] When the set reel diameter and meterage parameters are reached, the equipment automatically stops; when the winding automatically stops, the laser equipment automatically stops, the infrared equipment automatically stops, etc.; click the "Inflate" button on the control panel, automatically stop vacuum pumping, and automatically vent; after the vacuum in the vacuum chamber is exhausted, press and hold the "Interlock Protection" and "Open" buttons on the control panel at the same time to open the vacuum chamber, obtain the surface-modified functional current collector, and record the winding meterage, out-of-chamber time, etc.

[0096] Example 6: A method for surface modification of a functional current collector, specifically:

[0097] Step 1: Prepare Materials

[0098] Prepare a composite aluminum finished base film with a sufficient length (width: 1650 mm) and a clean surface without oil, impurities, etc., and perform DC etching to obtain a DC-etched aluminum-based film. Prepare magnesium powder as the cladding material, with the particle size of the magnesium powder being 45 - 75 μm, the sphericity being 1, and the Hall flow rate being 3.5 g / min.

[0099] Step 2: Loading

[0100] The upper film roll and a sufficient amount of magnesium powder are placed in a vacuum winding machine to evacuate the air. Click the air extraction button on the screen, observe the vacuum value and record it until the background vacuum reaches 5.0E-3 pa.

[0101] Step 3: Parameter setting

[0102] Set the distance between the infrared heating device and the surface of the aluminum-based film to 20 cm, the temperature of the cold drum for post-treatment to 5 °C, the cryogenic temperature to -140 °C, the temperature of the cooled film to 22 °C, the winding tension to 180 N, the unwinding tension to 160 N, and control the environmental humidity at 45%. Wait for the vacuum to reach the set vacuum degree of 5.0E-3 pa, then turn on the automatic process preheating mode to preheat the cladding, etc.

[0103] Step 4: Start preheating

[0104] Gradually increase the infrared heating power step by step to 1000 W, start the low-speed running of the base film at 1 m / min, and the preheating temperature of the aluminum-based film gradually rises to 70 °C. Adjust the laser power to 1000 W, the scanning speed to 10 m / min, the spot diameter to 6 mm, the powder feeding speed to 4.5 g / min, and the protective gas flow rate to 5 L / min.

[0105] Step 5: Laser cladding

[0106] After all preheating reaches the cladding set standard, start to increase the speed of the base film to 15 m / min, observe the magnesium powder cladding process, and manually adjust the process parameters individually according to the actual on-site situation to change the cladding effect. When the winding speed reaches the process set speed, start the cladding, and record parameters such as laser power, laser speed, and spot size. After the cladding is completed, the post-treatment cooling also works synchronously.

[0107] Step 6: Winding

[0108] After reaching the set reel diameter and meterage parameters, the equipment automatically stops; when the winding automatically stops, the laser equipment automatically stops, the infrared equipment automatically stops, etc.; click the "Inflate" button on the control panel to automatically stop the vacuum pumping and automatically release the air; after the vacuum in the vacuum chamber is exhausted, press and hold the "Interlock protection" and "Open" buttons on the control panel simultaneously to open the vacuum chamber to obtain the surface-modified functional current collector, and record the winding meterage, out-of-chamber time, etc.

[0109] Among them, the preparation method of the DC-etched aluminum-based film is as follows:

[0110] Mix hydrochloric acid, sulfuric acid, sodium sulfite and deionized water to prepare a pre-etching solution. The concentration of hydrochloric acid in the pre-etching solution is 1 mol / L, the concentration of sulfuric acid is 1 mol / L, and the concentration of sodium sulfite is 0.5 mol / L. Mix cyclodextrin, hydrochloric acid and deionized water to prepare a cyclodextrin acid solution. The concentration of hydrochloric acid in the cyclodextrin acid solution is 1 mol / L, and the concentration of cyclodextrin is 0.45 g / L. Immerse the aluminum foil in the pre-etching solution at 55 °C, control the current density to be 50 mA / cm 2 , pre-etch for 10 s. After pre-etching, take out the aluminum foil and immerse it in the cyclodextrin acid solution at 50 °C, control the current density to be 1 mA / cm 2 , etch for 65 s. After etching is completed, a DC-etched aluminum-based film is obtained.

[0111] Detection experiment: Prepare functional current collector samples according to the preparation methods in Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6 respectively, and use the unmodified wide-width 1650 mm composite aluminum finished base film as a comparative example to conduct tensile strength tests and peel force tests.

[0112] Tensile strength test: Overlap and lay flat the A4 paper and the prepared sample on the desktop. After covering the upper part with a cutting template, press the sample with the left hand and quickly cut down with an aluminum foil cutter in the right hand to complete the production of the specimen. The size of the specimen is 15 mm × 150 mm. Cut 5 specimens each time for each sample during the test. Place the cut specimens vertically on both sides of the chuck of the Testometric universal testing machine, set the test reference distance to 50 mm, clamp and conduct the test to measure the tensile strength and elongation of the specimen.

[0113] Peeling force test: Overlap and lay flat an A4 paper and the prepared sample on the tabletop. After covering the upper part with a cutting template, press the sample with the left hand, and quickly cut downward with a craft knife in the right hand to complete the production of the test specimen. The size of the test specimen is 60 mm × 80 mm, and 3 test specimens are cut for each sample each time. After putting the cut test specimens into an aluminum-plastic film bag, inject 10 mL of the electrolyte of a ternary lithium battery into the aluminum-plastic film bag to fully immerse the test specimens in the electrolyte. Set the soaking times to 1 day, 3 days, and 7 days respectively. After sealing the aluminum-plastic bag, place it in a thermostatic and humidistatic chamber for heat preservation. The temperature of the thermostatic and humidistatic chamber is at room temperature, and the moisture standard is 10 ppm. After reaching the set soaking time, take out the test specimens, wipe dry the electrolyte on the surface of the test specimens, and conduct peeling force tests. After trimming the test specimens to a size of 60 mm × 50 mm, stick the test specimens flat on the steel plate with 2 double-sided tapes 15 mm wide, and use a 2-kg roller to press back and forth on the sample piece from right to left 2 times. Then take 1 3M transparent tape about 22 cm long and 12.7 mm wide and stick it on the sample piece from right to left, and use a 2-kg roller to press back and forth on the transparent tape from right to left 2 times. Attach a piece of paper about 5 cm long and folded 3 times to the left end of the transparent tape to obtain the processed test specimen. Turn on the electronic peeling force testing machine, and fix the processed test specimen on the electronic peeling force testing machine to conduct peeling force tests.

[0114]

[0115] Conclusion: According to the test data, it can be seen that the tensile strength of the surface-modified functional current collector processed by the processing technology of Example 1 is higher than that of the unmodified functional current collector as the comparative example, and the tensile strength does not decay; after electrolyte soaking, the peeling force of the surface-modified functional current collector processed by the processing technology of Example 1 is higher than that of the unmodified functional current collector as the comparative example. During the experimental test process, the peeling force will have a certain slow decay as the electrolyte soaking time increases until it tends to be stable.

[0116] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A method for modifying the surface of a functional fluid collector, characterized in that: Specifically: Step 1: Pre-clean the surface of the aluminum base film to remove oil and impurities on the surface; Step 2: Preheat the aluminum base film after cleaning; Step 3: Use laser cladding to clad magnesium powder on the surface of the aluminum base film; Step 4: Cooling treatment after laser cladding to obtain a surface-modified functional current collector.

2. A method for surface modification of a functional fluid collector according to claim 1, characterized in that: The preheating treatment and laser cladding are carried out in a vacuum environment, the environment is kept clean, and the environmental humidity is controlled at 40-60%.

3. A method for surface modification of a functional fluid collector according to claim 1, characterized in that: An infrared heating device is used for preheating treatment. The distance between the infrared heating device and the surface of the aluminum base film is 10 to 30 cm, the film feeding speed is 1 to 5 m / min, the preheating temperature is 50 to 120°C, and the temperature is increased in steps of 10°C / min. During the heating process, the temperature uniformity of the base film surface is ensured to be within ±5°C. The infrared heating working device is always on until the heating is stopped after the laser cladding is completed.

4. A method for surface modification of a functional fluid collector according to claim 1, characterized in that: The particle size of the magnesium powder used in laser cladding is 45-105 μm, the purity is ≥99%, the sphericity is 0.8-1, and the Hall flow rate is 2-5 g / min.

5. The method for surface modification of a functional fluid collector according to claim 1, characterized in that: In step 3, the process parameters during laser cladding are: laser power of 1000-3000 W, spot diameter of 2-5 mm, scanning speed of 10-20 m / min, powder feeding rate of 2-5 g / min, and argon flow rate of 5-10 L / min.

6. A method for surface modification of a functional fluid collector according to claim 1, characterized in that: The cooling treatment adopts the cooling drum installation method, the cooling temperature is 0-10°C, and the cooling temperature is adjusted according to the membrane surface temperature. After cooling, the membrane surface temperature is 18-25°C.

7. The method for surface modification of a functional fluid collector according to claim 1, characterized in that: The aluminum-based film used is a direct current etched aluminum-based film, and the preparation method is as follows: Immerse the pretreated aluminum substrate in the pre-etching solution, control the solution temperature to 50-60°C, and the current density to 45-55 mA / cm 2 , pre-etch for 5 to 15 seconds, remove the aluminum base film after pre-etching, immerse it in a cyclodextrin acid solution, control the solution temperature to 45 to 55 ° C, and the current density to 1 mA / cm 2 , etch for 60 to 70 seconds, take it out after etching is completed, dry it, and obtain a DC etched aluminum base film.

8. A method for surface modification of a functional fluid collector according to claim 7, characterized in that: The pre-etching solution contains hydrochloric acid, sulfuric acid and sodium sulfite. The concentration of hydrochloric acid in the pre-etching solution is 0.8-1.2 mol / L, the concentration of sulfuric acid is 0.8-1.2 mol / L, and the concentration of sodium sulfite is 0.4-0.6 mol / L.

9. A method for surface modification of a functional fluid collector according to claim 7, characterized in that: In the cyclodextrin acid solution, the concentration of cyclodextrin is 0.4-0.5 g / L.

Images