Laser cleaning method for magnesium-based foil

Abstract

The invention discloses a laser cleaning method for a magnesium-based foil, and belongs to the technical field of magnesium ion battery manufacturing. According to the laser cleaning method for the magnesium-based foil, the magnesium-based foil is magnesium foil or magnesium alloy foil, and the method comprises the following steps that laser cleaning is conducted on the magnesium-based foil through a laser device, and a laser beam conducts 45-degree cross filling path scanning on the surface of the magnesium-based foil; monitoring a plasma spectral line of laser ablation in real time by using a plasma spectrometer; based on the dynamic change of the magnesium characteristic plasma spectral line intensity, the cleaning parameters of the laser are adjusted; and after cleaning is completed, an oxide layer on the surface of the magnesium-based foil is removed. 45-degree cross filling path scanning is adopted, heat accumulation of a repeated scanning area can be reduced, during 45-degree cross filling, adjacent scanning lines cover in a cross mode, heat distribution is more uniform, heat of the scanning area can be reduced, and therefore the problems of local overheating and negative plate perforation or structural damage caused by too high energy are avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnesium ion battery manufacturing, and particularly relates to a laser cleaning method for magnesium-based foil. BACKGROUND

[0002] As a new type of battery system developed in recent years, rechargeable magnesium secondary batteries are considered as a substitute for lithium ion batteries due to their excellent properties. Compared with the widely used lithium ion batteries, magnesium secondary batteries have the following advantages: (1) higher volumetric energy density (3833 mAh cm-3) and lower electrode potential (-2.37 V vs SHE); (2) the reserves of magnesium element in the earth's crust (2.3%) are much higher than those of lithium (0.0022%), and the price of magnesium resources is much lower than that of lithium resources, about 1 / 24 of lithium; (3) magnesium metal negative electrode is not prone to produce sharp dendrites during charging and discharging, and has intrinsic safety compared with existing lithium ion batteries and sodium ion batteries. Based on the above advantages, magnesium secondary batteries have gradually become a popular research field for the next generation of energy storage batteries.

[0003] When magnesium and its alloys are used as negative electrode materials for magnesium secondary batteries, a thin oxide film is easily generated on the surface due to poor corrosion resistance, and these oxidation products are important factors that affect the electrochemical performance. Manual polishing to remove the surface oxide is inefficient, and has problems such as environmental pollution and harm to the human body. With the improvement of environmental protection requirements, a green and efficient method for cleaning the oxide is needed. Laser cleaning, as a new technology, is widely studied due to its non-contact and non-pollution characteristics.

[0004] However, the existing cleaning method for magnesium-based foils has a high power, which can easily pierce or damage the magnesium-based foils, and is not suitable for thinner magnesium-based foils. SUMMARY

[0005] The purpose of the present application is to provide a laser cleaning method for magnesium-based foils to improve the problem of negative electrode sheet perforation or structural damage caused by excessive energy in the existing magnesium-based foil cleaning method.

[0006] The technical solution adopted by the present application is as follows: a laser cleaning method for magnesium-based foils, the magnesium-based foils being magnesium foils or magnesium alloy foils, the method comprising the following steps: The laser is used to clean the magnesium-based foils, and the laser beam is scanned on the surface of the magnesium-based foils at an angle of 45° intersecting the filling path; The plasma spectrometer is used to monitor the plasma spectrum of the laser ablation in real time; Based on the dynamic change of the intensity of the magnesium characteristic plasma spectrum, the cleaning parameters of the laser are adjusted; After cleaning, the oxide layer on the surface of the magnesium-based foils is removed.

[0007] Further, the output power of the laser is set to 8w-12w, the repetition frequency is 30kHz-50kHz, and the pulse width is 8ns-15ns; the scanning speed of the laser beam is 1800mm / s-2200mm / s.

[0008] Further, the laser beam performs 45° cross-filling path scanning on the surface of the magnesium-based foil, and the scanning path forms a 45° angle with the X-axis of the magnesium-based foil coordinate system; the scanning path is reciprocating scanning, and the scanning directions of adjacent two layers are opposite, forming a rhombic cross grid, and the scanning path constitutes a cross-filling path.

[0009] Further, the light signal intensity emitted by the neutral magnesium atom Mg I at 285.2nm ultraviolet wavelength is collected and obtained in real time, and a cleaning depth prediction model is established: wherein, is the actual cleaning depth, is the calibration coefficient fitted by experiment, is the characteristic spectral line intensity of the neutral magnesium atom, is the background spectral intensity; and the stop condition is set: when the irradiation of the laser beam is stopped; The defect detection is performed through the cleaning depth prediction model, and the detection result is fed back to the PC end in real time, and the scanning situation is judged by the PC end and the data is returned.

[0010] Further, the ratio of the scanning line spacing to the laser spot diameter is 0.3-0.6, and the spot overlap rate is 35%-45%, thereby forming a surface texture with energy density gradient distribution.

[0011] Further, the scanning line spacing is , the laser spot diameter is , and the laser spot focuses the focal point position deviation .

[0012] Further, the laser adopts a MOPA type fiber laser to emit a pulsed laser beam.

[0013] Further, the thickness of the magnesium-based foil is .

[0014] Further, after the magnesium-based foil is cleaned by laser, alcohol cleaning, vacuum drying are performed to remove the oxide layer on the surface of the magnesium-based foil.

[0015] Further, a heat diffusion model is established: wherein,​​ is the maximum temperature of the material surface, is the laser power, is the pi, is the laser spot radius, is the scanning speed, is the material absorption rate, is the thermal conductivity, is the thermal diffusivity.

[0016] Therefore, the present application has the following beneficial effects: The present application adopts 45° cross-filling path scanning, which can reduce the heat accumulation of repeated scanning areas. When 45° cross-filling is adopted, adjacent scanning lines cross cover, the heat distribution is more uniform, the heat of the scanning area can be reduced, thereby avoiding the problems of local overheating and negative plate perforation or structural damage caused by excessive energy. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the flow chart of the method of the present application; Figure 2 is the schematic diagram of the scanning path of the present application. DETAILED DESCRIPTION

[0018] The present application will be described in detail below with reference to the accompanying drawings.

[0019] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0020] The existing laser cleaning device and cleaning method has the following problems: single-layer linear scanning leads to single surface texture and cannot form a gradient structure; high laser power, i.e. high power greater than 15W, easily causes the molten pool effect of magnesium-based materials; lack of real-time process feedback, poor cleaning uniformity.

[0021] However, the existing magnesium battery negative electrode treatment mostly adopts acid pickling or dry etching, which has the following defects: high cost of chemical waste liquid treatment, high environmental protection pressure; isotropic corrosion leads to uncontrollable surface morphology; easy to cause excessive corrosion of magnesium alloy base.

[0022] And the existing magnesium alloy workpiece surface laser cleaning method before welding is suitable for cleaning thicker magnesium alloy workpieces. This method adjusts the laser power and cleaning speed to meet the surface preparation requirements before welding. However, the above method is not suitable for ultra-thin magnesium alloy because the laser cleaning power is too high, which can easily cause the magnesium foil to be damaged during the cleaning process, and the roughness consistency is poor, which can easily lose the electrochemical performance, and the cleaned magnesium foil cannot be used as a negative electrode material for magnesium batteries.

[0023] Therefore, the present application provides a laser cleaning method for magnesium-based foils, which is suitable for thinner magnesium foils, avoids negative electrode sheet perforation or structural damage due to excessive energy, improves surface roughness consistency, meets the requirements of electrochemical performance on substrate flatness, preserves the substrate activity of the negative electrode material under the premise of thorough cleaning, and ensures subsequent electrochemical performance.

[0024] Example 1 As shown in Figure 1 An embodiment of the present application is a laser cleaning method for magnesium-based foils. The magnesium-based foils are magnesium foils or magnesium alloy foils, which are thinner magnesium alloy workpieces. The method includes the following steps: Step S100: laser cleaning of the magnesium-based foils by a laser, and 45° cross-filling path scanning of the laser beam on the surface of the magnesium-based foils; Step S200: real-time monitoring of the plasma spectrum line of laser ablation by a plasma spectrometer; Real-time monitoring of the plasma spectrum establishes a quantitative relationship between the intensity of the magnesium characteristic plasma spectrum line and the cleaning depth, and adjusts the process parameters in real time. This realizes precise control, prevents substrate damage, avoids thermal damage or secondary oxidation of the substrate due to excessive energy or excessive cleaning time, adapts to the non-uniformity of the magnesium alloy surface state, ensures the consistency of the cleaning process, improves the micro-topography of pure magnesium and magnesium alloy surfaces, and improves the electrochemical performance of the battery after the pure magnesium and magnesium alloy after cleaning are used as negative electrode sheets to make the battery. The self-corrosion current density of the negative electrode sheet in the electrolyte can reach 0.02 μA / cm², which is 86.7% lower than the acid washing treatment of 0.15 μA / cm². Moreover, the consistency of the electrode sheet is improved. Experiments show that this method reduces the CV value within the batch from 8.7% to 2.3% (n=100). The CV value (coefficient of variation) is a statistical index used to measure the variability of spectral reflectance data; when the CV value is small, the relative variability of the data is small, and the data is stable; when the CV value is large, the relative variability of the data is large, and the data is less stable.

[0025] Step S300: adjusting the cleaning parameters of the laser based on the dynamic changes in the intensity of the magnesium characteristic plasma spectrum line; Step S400: removing the surface oxide layer of the magnesium-based foils after cleaning is completed.

[0026] The embodiment adopts 45° cross-filling path scanning, and has the following beneficial effects: Heat accumulation in the repeated scanning area can be reduced, the adjacent scanning lines cross cover when 45° cross-filling, the heat distribution is more uniform, the heat of the scanning area can be reduced, thereby avoiding the problems of local overheating and negative plate perforation or structure damage caused by excessive energy; The uniformity of the surface of the magnesium-based foil can be improved, the 45° scanning path makes the lap joint mode of the laser spot present a rhombus cross, and the surface texture of the cleaned magnesium-based foil is more uniform and does not have obvious parallel stripes; Complex geometric workpieces can be scanned, when the surface of the workpiece has a complex profile, 45° filling can better cover the profile edge and reduce the situation that the edge is not cleaned due to single scanning direction.

[0027] Embodiment 2 Another embodiment of the present application is that the output power of the laser is set to 8w-12w, the repetition frequency is 30kHz-50kHz, and the pulse width is 8ns-15ns; the scanning speed of the laser beam is 1800mm / s-2200mm / s.

[0028] The scanning speed is 1800mm / s-2200mm / s, and too low scanning speed will cause excessive heat input, so that the surface temperature is too high to melt and damage the substrate. Too high scanning speed makes the single pulse action time insufficient, and the removal rate of the oxide film is significantly reduced. The embodiment optimizes the scanning speed, which not only ensures the removal rate, but also protects the magnesium-based foil substrate. The laser adopts a MOPA type fiber laser to emit a pulsed laser beam, the wavelength is 1064nm, the peak power is greater than or equal to 20kW, the duty cycle is 50%, and the laser beam mode is .

[0029] Since the workpiece acted on by the laser of the embodiment is a magnesium-based foil, the corresponding parameters of the laser are limited, which not only ensures the completion of cleaning, but also avoids damaging the workpiece.

[0030] Embodiment 3 As shown in Figure 2 Another embodiment of the present application is that the laser beam performs 45° cross-filling path scanning on the surface of the magnesium-based foil, the scanning path forms a rhombus cross grid, and the scanning path constitutes a cross-filling path.

[0031] The scanning path is at an angle of 45° with the X axis of the magnesium-based foil coordinate system, and the laser beam emitted by the laser is at an angle of 45° or 135° with the plane where the magnesium-based foil is located. The selection of the angle of 45° or 135° is related to the position of the laser and the scanning direction. When the scanning path is from the negative direction of the X axis to the positive direction of the X axis, the scanning path is at an angle of 135° with the X axis of the magnesium-based foil coordinate system; when the scanning path is from the positive direction of the X axis to the negative direction of the X axis, the scanning path is at an angle of 45° with the X axis of the magnesium-based foil coordinate system.

[0032] The scanning path is reciprocating scanning, and at least two layers of scanning are required; if the scanning path angle of the first layer is 45°, the scanning path angle of the second layer is 135°. The two layers of scanning path form a rhombus-shaped intersecting grid-shaped intersecting filling path.

[0033] Due to the 45° scanning path, the overlapping mode of the laser spot is rhombus-shaped intersection, and the surface texture after cleaning is more uniform, and no obvious parallel stripes appear. Such stripes may appear due to the directionality of the scanning line when 0° filling; and when 45° filling, the overlapping between adjacent scanning lines is intersecting, so that under the condition of the same overlapping rate, the uncleaned area or over-cleaned area caused by mechanical positioning error can be reduced.

[0034] Embodiment 4 Another embodiment of the present application is to adjust the cleaning parameters of the laser based on the dynamic change of the intensity of the magnesium characteristic plasma spectrum line, specifically including the following: The light signal intensity emitted by the neutral magnesium atom Mg I at 285.2 nm ultraviolet wavelength is collected and acquired in real time, and a cleaning depth prediction model is established: ; Among them, is the actual cleaning depth, is the calibration coefficient, is the intensity of the characteristic spectrum line of the neutral magnesium atom, is the background spectrum intensity; and the stop condition is set: when , stop the irradiation of the laser beam, and adjust the cleaning parameters of the laser, such as the scanning line spacing, the laser spot diameter, etc., so that the actual cleaning depth is less than or equal to 0.8 ; Defect detection is performed through the cleaning depth prediction model, and the detection result is fed back to the PC end in real time. The PC end judges the scanning situation and performs data back transmission, thereby completing the cleaning of the magnesium-based foil.

[0035] The ratio of the scanning line spacing to the laser spot diameter is 0.3-0.6, and the spot overlap rate is 35%-45%, so that the surface texture with the energy density gradient distribution is formed. The scanning line spacing is The laser spot diameter is The laser spot passes through the dynamic focusing to make the deviation of the focal point position

[0036] The scanning line spacing is the distance between two adjacent scanning tracks when the mechanism (usually a galvanometer scanning system) that controls the movement of the light beam regularly scans the target surface in a laser processing or measuring system.

[0037] The laser spot is a bright spot formed on the target surface (workpiece, sample) after the laser beam passes through the optical system (mainly focusing mirror).

[0038] By optimizing the laser parameters, reducing the power density, limiting the scanning speed and scanning line spacing (0.05mm±5%), and using the energy gradient cross scanning strategy, the surface energy gradient distribution is realized, the oxidation layer removal efficiency and quality of the magnesium and magnesium alloy foil are improved, the surface oxidation layer removal rate is ≥98%, and the substrate damage depth is ≤0.5μm.

[0039] By controlling the ratio of the scanning line spacing to the laser spot diameter and the spot overlap rate, the high precision and efficiency of cleaning can be ensured, the energy waste is reduced on the basis of ensuring the processing quality, and the yield of cleaning is improved.

[0040] Embodiment 5 Another embodiment of the present application is that the thickness of the magnesium-based foil is .

[0041] When the thickness of the magnesium alloy workpiece satisfies , it is a relatively thin magnesium alloy workpiece, and the method of the embodiment is suitable.

[0042] Embodiment 6 Another embodiment of the present application is that after the magnesium-based foil is cleaned by laser, alcohol cleaning and vacuum drying are performed to remove the oxidation layer on the surface of the magnesium-based foil.

[0043] The alcohol cleaning uses the existing ultrasonic alcohol cleaning to remove the oxidation layer on the surface of the magnesium-based foil and complete the laser cleaning process. Through laser cleaning, the oxidation layer and impurities on the surface of the ultrathin magnesium alloy or magnesium foil are effectively removed, and the electrochemical performance of the magnesium secondary battery is improved.

[0044] Embodiment 7 Another embodiment of the present application is a system for laser cleaning of magnesium-based foils, the system comprising a pulsed laser, a scanning galvanometer, a high-precision five-axis moving platform, a motion control module, a laser control module, a plasma spectrum detection module, and a computer; The plasma spectrum detection module comprises a grating spectrometer and a CCD detector connected in sequence, the motion control module is connected to the five-axis moving platform to control the movement parameters of the five-axis moving platform, the laser control module is connected to the pulsed laser to control the parameters of the pulsed laser; the motion control module, the laser control module, and the CCD detector are all connected to the computer, the computer receives user instructions, transmits the instructions to the motion control module and the laser control module, and establishes a cleaning depth prediction model to adjust the cleaning parameters in real time through the laser control module according to the magnesium characteristic spectral line intensity fed back by the CCD detector. The pulsed laser is preferably a MOPA fiber laser, the positioning accuracy of the five-axis moving platform is ±2μm, and the scanning speed and power are adjusted in real time through a PID algorithm.

[0045] Example 8 The gradient energy laser cleaning parameter expansion verification experiment is as follows: Experimental conditions: Material: AZ61 magnesium alloy foil (thickness 30μm, surface oxide layer 2.0μm); Laser parameters: Power: 8W (duty cycle 40%), 10W (duty cycle 50%), 12W (duty cycle 60%); Scanning speed: 2000mm / s (gradient test); Scanning pitch line: 0.05mm (±45° bidirectional scanning); Frequency: 40kHz The experimental results are shown in Table 1: Table 1: Gradient energy laser cleaning experiment results

[0046] Experimental conclusion: when the power is increased to 12W, the HAZ depth increases significantly (0.65μm), exceeding the allowable limit (0.5μm), so this embodiment is suitable for using lower power, and high power is easy to cause damage to the substrate.

[0047] Example 9 The scanning speed boundary verification experiment is as follows: Experimental conditions: Material: AZ31 magnesium alloy (thickness 200μm, oxide layer 9.5μm); Laser parameters: power 10W, scanning pitch line 0.05mm, frequency 40kHz; The experimental results are shown in Table 2: Table 2 Scan speed boundary experiment results

[0048] Experimental conclusion: when the speed < 1800 mm / s, the heat input is excessive, resulting in melting; when the speed > 2200 mm / s, the single pulse action time is insufficient (t = d / v = 15 μs, = 2200 mm / s, when the scan speed v > 2200 mm / s, the pulse energy action time is insufficient (t < 15 μs), and the removal rate is significantly reduced. Therefore, the preferred scan speed of the present application is 1800 mm / s-2200 mm / s.

[0049] Example 10 The present application can also be implemented as follows: the selected magnesium-based foil material is AZ31 magnesium alloy foil with a thickness of 200 μm and an original oxide layer of 9.8 μm; the laser power is set to 10 W, the duty cycle is 50%, the scan speed is 2000 mm / s, the scan spacing line is 0.05 mm, and the repetition frequency is 40 kHz. A heat diffusion model is established to calculate the maximum temperature of the material surface during laser scanning. If the temperature is too low, it cannot effectively ablate the oxide layer, and if it is too high, it will melt the magnesium-based material. The melting point of magnesium alloy is about 650°C, and the oxide layer needs to reach a certain temperature (about 4.91 J / cm² threshold value) to break down. The temperature difference window is very narrow.

[0050] A heat diffusion model is established: ; wherein, T is the maximum temperature of the material surface, P is the laser power, π is the constant pi, r is the laser spot radius, v is the scan speed, α is the material absorption rate, k is the thermal conductivity coefficient, D is the thermal diffusion coefficient.

[0051] When the laser power (8-12 W), scan speed (1800-2200 mm / s), and other parameters are set, the maximum surface temperature is calculated by the heat diffusion model to ensure that it is lower than the melting point of the magnesium-based foil material (≈650°C), avoiding melting or perforation due to heat accumulation.

[0052] When performing 45° cross scanning, the energy input point is dispersed (diamond grid), the heat accumulation rate per unit area is reduced, and the maximum temperature of the material surface is controllable (compared to one-way scanning which easily leads to local overheating).

[0053] When the plasma spectrum is monitored in real time, if the spectral line intensity abnormally increases (reflecting a sudden increase in temperature), the thermal diffusion model can quickly deduce whether it is caused by local thermal runaway, and trigger parameter adjustment (such as reducing power or increasing speed).

[0054] By the method of the application, the oxide layer removal rate is 99.2% (XPS detection), and the surface roughness Ra is 1.32 μm (white light interferometer).

[0055] The comparative experiment of acid pickling treatment is set up: Experimental conditions: Acid solution formula: 0.5% + 1.5% HCl (volume ratio), room temperature soaking.

[0056] Treatment time: 15s, 30s, 60s; The experimental results are shown in Table 3: Table 3 Acid pickling treatment experimental results

[0057] Therefore, the corrosion is uncontrollable: the acid solution penetrates along the grain boundary to form etch pits with a depth of >2 μm; each treatment The pole produces 0.5L fluorine-containing waste liquid, and the treatment cost reaches 150 yuan / , the environmental pollution problem is more serious; surface passivation: XPS detects / By-product layer (thickness 30-50nm), resulting in a 3-fold increase in charge transfer impedance.

[0058] The results of the comparison between the laser cleaning of the application and the acid pickling treatment are shown in Table 4: Table 4 Comprehensive comparison table across processes

[0059] The AZ31 magnesium alloy foil cleaned in the example is used to prepare a magnesium secondary battery. A sulfur-carbon material is used as the positive electrode, copper foil is used as the current collector, and magnesium foil is used as the negative electrode. After cutting, the pieces are reserved, then the pieces are stacked, a suitable electrolyte is added, and finally a soft package battery is prepared.

[0060] The test is carried out using the new well system, the test environment temperature is 25℃, the 0.1C charge-discharge test battery has a first efficiency of 93%. As a comparison, the first efficiency of the magnesium secondary battery prepared by the mechanically polished negative electrode material is 68%, and the test results are shown in Table 5.

[0061] Table 5 New well system test results

[0062] Example 11 The metal universality verification experiment is as follows: The magnesium alloy and stainless steel control groups were set, the magnesium alloy: AZ31 (thickness 200 μm, oxide layer 9.5 μm), the stainless steel: SUS304 (thickness 200 μm, oxide layer 9.5 μm); Parameters: power: 10 W (duty cycle 50%); Scanning speed: 2000 mm / s (gradient test); Scanning interval line: 0.05 mm (± 45° bidirectional scanning); The experimental results are shown in Table 6: Table 6 Magnesium alloy and stainless steel control experiment

[0063] Experimental conclusion: the oxide layer removal rate of the magnesium alloy surface is larger, and the surface has no other attachments, and the removal effect is better.

[0064] The critical difference in the thermal physical properties of magnesium and aluminum alloy needs to adapt the laser parameters: Melting point of magnesium alloy: 650℃, thermal diffusivity: 57.8 mm² / s, oxide layer breakdown threshold: 4.91 J / cm²; Melting point of aluminum alloy: 660℃, thermal diffusivity: 97.6 mm² / s, oxide layer breakdown threshold: 9.52 J / cm².

[0065] Relationship between average power and single pulse energy: ; ; Wherein, is the oxide layer thickness, is the oxide layer density, is the specific heat capacity, is the melting point to room temperature temperature difference, is the latent heat of fusion, is the infrared laser reflectivity, is the spot area, is the average power threshold, is the single pulse energy, is the pulse frequency.

[0066] The values of each parameter of magnesium and aluminum alloy are as follows:

[0067] Experimental conclusion: according to the values of each parameter, the breakdown energy of magnesium is only 52% of that of aluminum, and the use of high power process will inevitably lead to overburning.

[0068] The above merely describes preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for laser cleaning of a magnesium-based foil, the magnesium-based foil being a magnesium foil or a magnesium alloy foil, characterized in that, The method comprises the following steps: The magnesium-based foil is subjected to laser cleaning by a laser, and the laser beam is subjected to 45° cross-filling path scanning on the surface of the magnesium-based foil; The plasma spectrum of laser ablation is monitored in real time by using a plasma spectrometer; Based on the dynamic change of the intensity of the magnesium characteristic plasma spectrum, the cleaning parameters of the laser are adjusted; After cleaning, the oxide layer on the surface of the magnesium-based foil is removed.

2. The method of claim 1, wherein the magnesium-based foil is a magnesium-based alloy foil. The output power of the laser is set to 8-12 W, the repetition frequency is 30-50 kHz, and the pulse width is 8-15 ns; the scanning speed of the laser beam is 1800-2200 mm / s.

3. The method of claim 2, wherein the laser cleaning is performed by a laser beam having a wavelength of 1,064 nm. The laser beam is subjected to 45° cross-filling path scanning on the surface of the magnesium-based foil, the scanning path is at an angle of 45° with the X-axis of the magnesium-based foil coordinate system; the scanning path is reciprocating scanning, and the scanning directions of adjacent two layers are opposite, forming a rhombic cross-grid shape, and the scanning path constitutes a cross-filling path.

4. The method of claim 3, wherein the laser cleaning is performed by a laser beam having a wavelength of 1,064 nm. The light signal intensity emitted by the neutral magnesium atom Mg I at 285.2 nm ultraviolet wavelength is collected and acquired in real time, and a cleaning depth prediction model is established: ； wherein, is the actual cleaning depth, is the calibration factor, is the neutral magnesium atomic characteristic spectral line intensity, is the background spectral intensity; and set a stop condition: when the irradiation of the laser beam is stopped; Defect detection is performed by the cleaning depth prediction model, and the detection result is fed back to the PC end in real time, and the scanning condition is judged by the PC end and the data is returned.

5. The method of claim 4, wherein the laser cleaning is performed by a laser beam having a wavelength of 1,064 nm. The ratio of the scanning line spacing to the laser spot diameter is 0.3-0.6, and the spot overlap rate is 35%-45%, thereby forming a surface texture with gradient distribution of energy density.

6. The method of claim 5, wherein the laser cleaning is performed at a power of 1 to 10 kW. The scanning line interval is , the laser spot diameter is , and the laser spot passes through dynamic focusing to make the deviation of the focal point position .

7. The method of claim 1, wherein the magnesium-based foil is a magnesium-based alloy foil. The laser adopts a MOPA type fiber laser to emit a pulsed laser beam.

8. The method of claim 1, wherein the magnesium-based foil is a magnesium-based alloy foil. The thickness of the magnesium-based foil is .

9. The method of claim 1, wherein the magnesium-based foil is a magnesium-based alloy foil. After the magnesium-based foil is cleaned by the laser, it is subjected to alcohol cleaning and vacuum drying to remove the oxide layer on the surface of the magnesium-based foil.

10. The method of claim 1, wherein the magnesium-based foil is a magnesium-based alloy foil. A thermal diffusion model is established: ； wherein, is the maximum temperature of the surface of the material, is the laser power, is the constant pi, is the radius of the laser spot, is the scanning speed, is the material absorption, is the thermal conductivity, is the thermal diffusivity.

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