Laser cleaning method for negative electrode tab of solid-state battery

Abstract

The invention discloses a solid-state battery negative electrode tab laser cleaning method, which comprises the following steps: after a rolling process, introducing an oxidizing atmosphere into the surface of a tab of a negative electrode piece, carrying out laser cleaning on the surface of the tab at the same time, and carrying out first-time laser cleaning by regulating and controlling laser power and controlling the temperature of the surface of the tab; and introducing a reducing atmosphere into the surface of the tab, carrying out laser cleaning on the surface of the tab, and carrying out secondary laser cleaning by regulating and controlling the laser power and controlling the surface temperature of the tab. The specific atmosphere is added in the negative electrode tab laser cleaning process, and a corrosion product Cu2S generated by corrosion on the sulfide solid-state battery negative electrode tab can be completely eliminated, so that the internal resistance of the tab is reduced, the welding performance of the tab is improved, and dangers such as pseudo soldering, damage or fracture are avoided; in addition, the negative electrode tab subjected to the rolling process is subjected to laser cleaning and annealing treatment at the same time, so that residual stress caused by pole piece rolling can be eliminated, tab wrinkles are eliminated, and subsequent procedures are facilitated.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, and more specifically, this invention relates to a laser cleaning method for the negative electrode tab of a solid-state battery. Background Technology

[0002] Sulfide solid-state batteries are considered a core technology for next-generation high-energy-density and high-safety energy storage devices due to their high ionic conductivity, wide electrochemical window, and good interfacial contact characteristics. However, their industrialization faces severe challenges, with sulfide contamination of the negative electrode surface during cell manufacturing being one of the key bottlenecks.

[0003] The negative electrode of a sulfide solid-state battery typically uses carbon-coated copper foil, such as... Figure 1 As shown, the electrode is divided into two areas: carbon-coated area B and foil area A. Foil area A (without carbon coating) is located on both sides of the foil. This area is not covered by the active material during the preparation of the negative electrode sheet and is used as a tab for welding to conduct current. The preparation methods for the negative electrode sheet of sulfide solid-state batteries include dry and wet methods. Wet-process electrodes typically involve mixing the negative electrode active material, conductive agent, sulfide electrolyte, binder, and solvent to prepare a slurry of a certain viscosity, which is then coated onto the carbon-coated area B and processed through baking and rolling to form the negative electrode sheet.

[0004] However, during the coating and baking of the electrode, the sulfide electrolyte usually volatilizes some corrosive gases such as H2S, causing corrosion of the bright foil area of ​​the carbon-coated copper foil and generating gray-black corrosion products such as Cu2S. The resulting hazards are: (1) the internal resistance of the copper foil increases, causing the battery cell to generate heat and leading to a decrease in cycle performance; (2) the appearance of corrosion products such as Cu2S in the bright foil area will lead to a decrease in the mechanical properties of the electrode tab, resulting in hazards such as false welding, damage or breakage during ultrasonic welding.

[0005] Current methods for cleaning electrode tabs include laser cleaning and chemical cleaning. Chemical cleaning is costly, polluting, and has inconsistent results. While laser cleaning is a mature method, it is suitable for liquid battery electrodes. Using it for sulfide solid-state battery electrodes results in low efficiency, poor cleaning effect, and easy electrode ablation. For example, patents CN202410423323.5 ("A Lithium Battery Electrode Tab Cleaning Device and Method") and CN202211244692.5 ("A Method for Laser Cleaning of Lithium Battery Electrodes") are applicable to liquid batteries. However, there is no corresponding solution for cleaning Cu2S and other corrosion products in the field of sulfide solid-state battery negative electrode tabs. Therefore, there is an urgent need to develop a laser cleaning method suitable for sulfide solid-state battery negative electrode tabs. Summary of the Invention

[0006] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0007] To achieve these objectives and other advantages of the present invention, a method for laser cleaning of the negative electrode tabs of a solid-state battery is provided. After the rolling process, the tabs of the negative electrode sheet are subjected to two laser cleaning processes, specifically including the following steps: Step 1: Introduce an oxidizing atmosphere onto the surface of the electrode tab while simultaneously performing laser cleaning on the surface of the electrode tab. Control the surface temperature of the electrode tab by adjusting the laser power to perform the first laser cleaning. Step 2: Introduce a reducing atmosphere onto the surface of the electrode tab and simultaneously perform laser cleaning on the surface of the electrode tab. By adjusting the laser power, control the surface temperature of the electrode tab and perform a second laser cleaning.

[0008] Preferably, the negative electrode sheet is prepared from carbon-coated copper foil; the carbon-coated copper foil includes a carbon-coated area and a bare foil area; the bare foil area is disposed on both sides of the carbon-coated copper foil and is used as an electrode tab; the carbon-coated area is disposed between the bare foil areas and is used to coat a negative electrode slurry containing a sulfide electrolyte.

[0009] Preferably, the process steps for preparing the negative electrode sheet include: coating a negative electrode slurry containing a sulfide electrolyte onto the carbonized area of ​​the carbonized copper foil, drying it, and then performing a rolling process.

[0010] Preferably, in step one, the oxidizing atmosphere is a mixture of O2 and dry air.

[0011] Preferably, the mass concentration of O2 in the oxidizing atmosphere is 30% to 80%.

[0012] Preferably, in step one, the surface temperature of the electrode tab is controlled to be 500℃~700℃.

[0013] Preferably, in step one, the laser cleaning process parameters are: spot diameter of 30-50 micrometers, laser scanning speed of 1000-3000 mm / s, and power of 500-700 W.

[0014] Preferably, in step two, the reducing atmosphere is a mixture of CO and dry air.

[0015] Preferably, the mass concentration of CO in the reducing atmosphere is 30% to 60%.

[0016] Preferably, in step two, the surface temperature of the electrode tab is controlled to be 300℃~400℃.

[0017] Preferably, in step two, the laser cleaning process parameters are: spot diameter of 30-50 micrometers, laser scanning speed of 1000-3000 mm / s, and power of 300-400 W.

[0018] Preferably, the method for preparing the negative electrode slurry includes: mixing the negative electrode active material, sulfide electrolyte, conductive agent and binder, adjusting the solid content to 40-50% using a solvent, and mixing the slurry at a speed of 500-1500 rpm for 20-50 minutes to obtain the negative electrode slurry.

[0019] Preferably, the negative electrode active material includes graphite, silicon carbide, or silicon; the sulfide electrolyte includes Li6PS5Cl; the conductive agent includes carbon nanofiber (VGCF); the binder includes polyvinylidene fluoride (PVDF); and the solvent includes butyl butyrate.

[0020] Preferably, the mass ratio of the negative electrode active material, sulfide electrolyte, conductive agent and binder is (60~80):(20~30):(1~3):(2~5).

[0021] The present invention has at least the following beneficial effects: By adding a specific atmosphere during the laser cleaning process of the negative electrode tab, the corrosion product Cu2S generated by the corrosion on the negative electrode tab of the sulfide solid battery can be completely eliminated, thereby achieving the following effects: (1) reducing the internal resistance of the tab; (2) improving the welding performance of the tab and avoiding dangers such as false welding, damage or breakage; (3) after the rolling process, the negative electrode tab is laser cleaned and annealed at the same time, which can eliminate the residual stress caused by the rolling of the electrode sheet, eliminate the wrinkles of the tab, and facilitate the subsequent processes.

[0022] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the carbon-coated copper foil used in the negative electrode sheet of the solid-state battery of the present invention, wherein A is the bare foil area and B is the carbon-coated area. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0025] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0026] Figure 1This is a schematic diagram of the structure of the carbon-coated copper foil used in the solid-state battery negative electrode sheet of the present invention, including a bare foil region A and a carbon-coated region B; the wet preparation method of the sulfide solid-state battery negative electrode sheet includes: mixing the negative electrode active material, conductive agent, sulfide electrolyte, binder and solvent to prepare a negative electrode slurry of a certain viscosity, and coating it in the carbon-coated region B of the carbon-coated copper foil; the bare foil region A (without carbon coating) is located on both sides of the copper foil. This region is not covered by the negative electrode slurry when preparing the negative electrode sheet and is used as a tab for welding to conduct current.

[0027] When the negative electrode sheet of a sulfide solid-state battery is coated with negative electrode slurry, during oven drying (50℃~100℃), the sulfide electrolyte in the slurry will volatilize corrosive gases such as H2S, which will chemically react with the bright foil area A coated with carbon copper foil. ; The formation of gray-black Cu2S products on the surface of the foil region A causes an increase in the internal resistance of the copper foil and a decrease in the mechanical properties of the tabs. The coated negative electrode sheet needs to undergo a rolling process to obtain a negative electrode sheet of the designed thickness. After the rolling process, in order to remove the Cu2S products on the surface of the foil region A, laser cleaning is required. The electrode laser cleaning method designed in this invention consists of two steps. First, an oxidizing atmosphere with an O2 concentration of 30%~80% is introduced onto the electrode surface, while laser cleaning is performed simultaneously. By adjusting the laser power, the electrode surface temperature is controlled at 500℃~700℃. Cu2O and CuO are mainly generated on the electrode surface, and the chemical reaction formula is as follows: ; ; If Cu₂S is directly reduced to Cu through laser cleaning, the copper foil will melt through very easily because Cu has a melting point of 1083℃, while the temperature at which Cu₂S is reduced to Cu is >1100℃. The chemical reaction formula is as follows: ; Therefore, this invention introduces an oxidizing atmosphere to lower the reaction temperature and improve the process yield; After Cu₂O and CuO are mainly formed on the electrode surface, a second laser cleaning is required. Simultaneously, a reducing atmosphere with a CO concentration of 30%–60% is introduced. By adjusting the laser power, the electrode surface temperature is controlled at 300℃–400℃, reducing the Cu₂O and CuO on the electrode surface to elemental Cu. The chemical reaction formula is as follows: ; ; The two-step laser cleaning method of this invention successfully reduces Cu2S products on the electrode tab surface to Cu. In addition, during the laser cleaning of Cu2S, the negative electrode tab is simultaneously annealed (the annealing temperature of copper material is 500℃~700℃), which eliminates residual stress caused by electrode rolling and removes electrode tab wrinkles, which is beneficial to the subsequent processes.

[0028] In this invention, when the coated negative electrode sheet is rolled in a roll press, the parameters are set as follows: unwinding tension 30~80N, winding tension 50~130N, and belt speed 500~900mm / s. Two laser cleaning devices are set up sequentially between the roll press and the roll to complete the first and second laser cleaning. The laser head is aligned with the negative electrode tab of the roll press, and laser cleaning is performed with a spot diameter of 30~50 micrometers, a laser scanning speed of 1000~3000mm / s, and a power of 300~700W.

[0029] The cleaning head of this invention integrates the laser beam path and the gas delivery pipeline. The laser is focused and emitted from a central lens group, while a specific gas is injected coaxially and directly onto the laser spot area on the electrode surface through an annular nozzle surrounding the laser beam. Before or simultaneously with laser emission, the gas nozzles begin to operate, forming a stable local gas atmosphere zone with a diameter of only a few millimeters to tens of millimeters on the electrode surface. This "gas hood" effectively isolates air, ensuring the reaction takes place in the required atmosphere; simultaneously, real-time blowing: the high-speed flowing gas can promptly blow away reaction products and debris generated during laser cleaning from the surface, preventing their redeposition, thereby ensuring cleaning quality and process stability.

[0030] The preparation method of the negative electrode slurry used in this invention includes: weighing the negative electrode active material Si / C-450 (purchased from BTR Corporation, model DXB5), sulfide electrolyte Li6PS5Cl, conductive agent VGCF and binder PVDF in a mass ratio of 70:25:2:3, adjusting the solid content to 43% using butyl butyrate, and mixing the slurry using a vibrating ball mill at a speed of 1000 rpm for 30 min to obtain the negative electrode slurry.

[0031] The specific concentrations of oxidizing and reducing atmospheres used in this invention can be produced in-house or purchased directly.

[0032] The laser cleaning equipment used in this invention integrates a miniature infrared temperature probe, whose optical path is parallel to or at a small angle to the laser optical path, to achieve real-time, online temperature monitoring and determine the surface temperature of the electrode tab.

[0033] In addition, when adjusting the equipment parameters, the tabs after cleaning in steps one and two can be tested on an XRD device, and the cleaning status can be determined by observing the diffraction peaks of different phases.

[0034] Example 1 A method for laser cleaning of the negative electrode tabs of a solid-state battery includes the following steps: Step 1: The coated negative electrode sheet is rolled in a roll press. A laser die is aligned with the rolled negative electrode tab, and an oxidizing atmosphere (40% O2 mass concentration, the remainder being dry air at -60℃) is introduced onto the tab surface. Simultaneously, laser cleaning is performed on the tab surface. By adjusting the laser power, the tab surface temperature is controlled at 500℃. Cu2O and CuO are mainly generated on the tab surface, completing the first laser cleaning. The rolling parameters are set as follows: unwinding tension 60N, winding tension 100N, and belt speed 700mm / s. The laser cleaning parameters are set as follows: spot diameter 40 micrometers, laser scanning speed 2000mm / s, and power 500W. XRD analysis shows that Cu2O and CuO are mainly generated on the tab surface. Step 2: A reducing atmosphere is introduced onto the surface of the electrode tab, with a CO mass concentration of 30% and the remainder being dry air at -60°C. Simultaneously, laser cleaning is performed on the electrode tab surface. By adjusting the laser power, the surface temperature of the electrode tab is controlled at 300°C, causing Cu2O and CuO on the electrode tab surface to be reduced to elemental Cu, completing the second laser cleaning. The laser cleaning parameters are set as follows: spot diameter of 40 micrometers, laser scanning speed of 2000 mm / s, and power of 300 W. XRD is used to detect the reduction of Cu2O and CuO to elemental Cu on the electrode tab surface.

[0035] Example 2 This embodiment is basically the same as that of embodiment 1, except that the mass concentration of O2 in embodiment 2 is 60%.

[0036] Example 3 This embodiment is basically the same as that of embodiment 1, except that the mass concentration of O2 in embodiment 3 is 80%.

[0037] Example 4 This embodiment is basically the same as that of embodiment 1, except that the mass concentration of O2 in embodiment 4 is 60% and the mass concentration of CO is 40%.

[0038] Example 5 This embodiment is basically the same as that of embodiment 1, except that the mass concentration of O2 in embodiment 5 is 60% and the mass concentration of CO is 50%.

[0039] Example 6 This embodiment is basically the same as that of embodiment 1, except that the mass concentration of O2 in embodiment 6 is 60% and the mass concentration of CO is 60%.

[0040] Example 7 This embodiment is basically the same as embodiment 1, except that: in step one of embodiment 7, the surface temperature of the electrode is controlled at 700°C by adjusting the laser power; the laser cleaning parameters are set as follows: the spot diameter is 40 micrometers, the laser scanning speed is 2000mm / s, and the power is 700W.

[0041] Example 8 This embodiment is basically the same as embodiment 1, except that in step two of embodiment 8, the surface temperature of the electrode is controlled at 400°C by adjusting the laser power; the laser cleaning parameters are set as follows: the spot diameter is 40 micrometers, the laser scanning speed is 2000mm / s, and the power is 400W.

[0042] Comparative Example 1 This comparative example is basically the same as Example 1, except that the mass concentration of O2 in Comparative Example 1 is 20% and the mass concentration of CO is 80%.

[0043] Comparative Example 2 This comparative example is basically the same as Example 1, except that the mass concentration of O2 in Comparative Example 2 is 90%.

[0044] Comparative Example 3 This comparative example is basically the same as Example 1, except that the mass concentration of CO in Comparative Example 3 is 80%.

[0045] Comparative Example 4 This comparative example is basically the same as Example 1, except that the mass concentration of CO in Comparative Example 4 is 20%.

[0046] Comparative Example 5 This comparative example is basically the same as Example 1, except that in step one of Comparative Example 5, the surface temperature of the electrode is controlled at 800°C by adjusting the laser power; the laser cleaning parameters are set as follows: spot diameter is 40 micrometers, laser scanning speed is 2000 mm / s, and power is 800 W.

[0047] Comparative Example 6 This comparative example is basically the same as Example 1, except that in step one of Comparative Example 6, the surface temperature of the electrode is controlled at 450°C by adjusting the laser power; the laser cleaning parameters are set as follows: spot diameter is 40 micrometers, laser scanning speed is 2000 mm / s, and power is 450 W.

[0048] Comparative Example 7 This comparative example is basically the same as Example 1, except that in step two of Comparative Example 7, the surface temperature of the electrode is controlled at 500°C by adjusting the laser power; the laser cleaning parameters are set as follows: spot diameter is 40 micrometers, laser scanning speed is 2000mm / s, and power is 500W.

[0049] Comparative Example 8 This comparative example is basically the same as Example 1, except that in step two of Comparative Example 8, the surface temperature of the electrode is controlled at 200°C by adjusting the laser power; the laser cleaning parameters are set as follows: spot diameter is 40 micrometers, laser scanning speed is 2000 mm / s, and power is 200 W.

[0050] Performance tests were conducted on the tabs of the examples and comparative examples. The thickness of the carbon-coated copper foil in region A was 6 μm. The specific test steps are as follows: (1) Cut the copper foil that has undergone two laser cleanings into circular pieces with a diameter of 10 mm and measure the internal resistance in the thickness direction; (2) Cut the copper foil that has been laser cleaned twice into rectangular samples of 50mm*100mm and overlap them 40 times. Then perform ultrasonic welding and then use a tensile testing machine to measure the tensile force at 1 / 2 of the thickness direction.

[0051] The results are shown in Table 1. It can be seen that when the O2 concentration and CO concentration of Comparative Examples 1 to 4 do not meet the requirements of the present invention, the internal resistance of the single-layer copper foil increases and the tension between the tabs decreases. When the surface temperature of the tabs of Comparative Examples 5 to 8 does not meet the requirements of the present invention, the internal resistance of the single-layer copper foil increases and the tension between the tabs decreases. Examples 1 to 8 achieved the lowest internal resistance and the highest tension between the tabs by reasonably setting the O2 concentration, CO concentration and temperature.

[0052] Table 1 Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method of laser cleaning of a solid-state battery negative tab, characterized by, After the rolling process, the tabs of the negative electrode sheet undergo two laser cleaning processes, specifically including the following steps: Step 1: Introduce an oxidizing atmosphere onto the surface of the electrode tab and simultaneously perform laser cleaning on the surface of the electrode tab. Control the surface temperature of the electrode tab by adjusting the laser power to perform the first laser cleaning. Step 2: Introduce a reducing atmosphere onto the surface of the electrode tab and simultaneously perform laser cleaning on the surface of the electrode tab. By adjusting the laser power, control the surface temperature of the electrode tab and perform a second laser cleaning.

2. A method of laser cleaning of a solid-state battery negative tab according to claim 1, wherein, The negative electrode sheet is prepared from carbon-coated copper foil; the carbon-coated copper foil includes a carbon-coated area and a bare foil area; the bare foil area is located on both sides of the carbon-coated copper foil and is used as an electrode tab; the carbon-coated area is located between the bare foil areas and is used to coat a negative electrode slurry containing sulfide electrolyte.

3. The laser cleaning method for the negative electrode tab of a solid-state battery as described in claim 2, characterized in that, The process steps for preparing the negative electrode sheet include: coating a negative electrode slurry containing sulfide electrolyte onto the carbonized area of ​​the carbonized copper foil, drying it, and then performing a rolling process.

4. The laser cleaning method for the negative electrode tab of a solid-state battery as described in claim 1, characterized in that, In step one, the oxidizing atmosphere is a mixture of O2 and dry air.

5. The laser cleaning method for the negative electrode tab of a solid-state battery as described in claim 4, characterized in that, In the oxidizing atmosphere, the mass concentration of O2 is 30% to 80%.

6. The laser cleaning method for the negative electrode tab of a solid-state battery as described in claim 1, characterized in that, In step one, the surface temperature of the electrode tab is controlled to be 500℃~700℃.

7. The laser cleaning method for the negative electrode tab of a solid-state battery as described in claim 1, characterized in that, In step one, the laser cleaning process parameters are: spot diameter of 30-50 micrometers, laser scanning speed of 1000-3000 mm / s, and power of 500-700 W.

8. The laser cleaning method for the negative electrode tab of a solid-state battery as described in claim 1, characterized in that, In step two, the reducing atmosphere is a mixture of CO and dry air.

9. The laser cleaning method for the negative electrode tab of a solid-state battery as described in claim 8, characterized in that, In the reducing atmosphere, the mass concentration of CO is 30% to 60%.

10. The method for laser cleaning of the negative electrode tab of a solid-state battery as described in claim 1, characterized in that, In step two, the surface temperature of the electrode tab is controlled at 300℃~400℃; the process parameters for laser cleaning are: spot diameter of 30~50 micrometers, laser scanning speed of 1000~3000mm / s, and power of 300~400W.

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