Battery piece cutting method and half battery piece

Abstract

The invention provides a battery piece cutting method and a half battery piece, the battery piece comprises a first surface and a second surface which are opposite, a first cutting line is located on the first surface, a second cutting line is located on the second surface, and the projection of the first cutting line on the second surface is overlapped with the second cutting line. The method comprises the steps that the position where a first cutting line is located is preheated; performing laser scanning on the position of the first cutting line of the preheated battery piece; and cooling the position where the second cutting line of the scanned battery piece is located by using a cooling process, so that the cooled battery piece is split, and a half battery piece is obtained. According to the invention, the problem that the thermal damage of the surface and the cross section of the silicon wafer caused by the laser effect seriously affects the carrier transmission efficiency and further affects the overall performance of the cell in the preparation process of the half cell in the existing laser scribing technology is solved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for cutting a battery cell and a half-cell battery cell. Background Art

[0002] In the currently known half-cell preparation technology, the temperature rise on the laser scanning path and the uneven temperature field on the silicon wafer, and then the temperature gradient generates thermal stress. When the tensile stress generated reaches the fracture limit of the silicon material, the silicon wafer stably cracks and the purpose of cutting is achieved. It mainly uses high-power thermal cracking laser heating and heat conduction from the inside of the battery to the back of the battery to provide a temperature gradient field to form thermal stress. The temperature difference between the upper and lower surfaces must reach the range of 150°-250°; since the (100), (110), and (111) crystal planes of silicon material are the main fracture surfaces, the fracture toughness difference between the three is small. When crack control laser cutting is performed, as a whole, under the action of thermal stress, the material cracks and expands along the laser scanning direction; locally, the thermal stress exceeds the corresponding fracture strength in the three crystal directions, resulting in regular ripples on the fracture surface; the generation of such ripples greatly affects the contour flatness and surface roughness of the silicon wafer fracture surface, greatly affecting the composite density at this position and the subsequent passivation film formation effect, so it needs to be solved in a certain way.

[0003] During the cutting process of existing laser scribing technology, the high-power laser causes thermal damage to the surface and cross-section, which affects the battery's composite density and carrier transport effect, thereby reducing the opening voltage and fill factor. Summary of the invention

[0004] The main purpose of the present application is to provide a cell cutting method and a half-cell cell, so as to solve the problem that in the process of preparing half-cell cells with the existing laser scribing technology, the thermal damage to the surface and cross-section of the silicon wafer caused by the laser seriously affects the transmission efficiency of the carriers, thereby affecting the overall performance of the battery.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a method for cutting a battery cell is provided, the battery cell comprising a first surface and a second surface relative to each other, a first cutting line located on the first surface, a second cutting line located on the second surface, and a projection of the first cutting line on the second surface overlapping with the second cutting line, the method comprising: preheating the position where the first cutting line is located; performing a laser scanning on the position where the first cutting line is located on the preheated battery cell; and using a cooling process to cool the position where the second cutting line is located on the scanned battery cell, so that the cooled battery cell is split to obtain a half-cell battery cell.

[0006] Optionally, the position where the first cutting line is located is preheated, including: using a heating device to preheat the position where the first cutting line is located at a temperature of 80°C~90°C, and using a cooling process to cool the position where the second cutting line of the scanned battery cell is located at a temperature of -10°C~10°C, so that the cooled battery cell forms a temperature gradient field in a predetermined direction, and the predetermined direction represents at least one of the three crystal directions corresponding to the battery cell.

[0007] Optionally, laser scanning is performed on the position of the first cutting line of the preheated battery cell, including: using a laser with a laser power of 300W~600W, a laser frequency of 50Khz~200Khz, a scanning speed of 500mm / s~800mm / s and a circular spot diameter of 1mm~2mm to scan the position of the first cutting line of the preheated battery cell.

[0008] Optionally, before preheating the position where the first cutting line is located, the method further includes: laser grooving two ends of the first cutting line to form end grooves.

[0009] Optionally, performing laser grooving on both ends of the first cutting line includes: using a laser with a laser power of 30W-100W and a laser frequency of 50Khz-200Khz to perform grooving on both ends of the first cutting line.

[0010] Optionally, laser scanning is performed on the position of the first cutting line of the preheated battery cell, including: laser scanning the position of the first cutting line after preheating at a first incident angle, wherein the first incident angle represents the angle between the scanning laser and the first surface; laser grooves are performed on both ends of the first cutting line, including: laser grooves are performed on both ends of the first cutting line at a second incident angle, wherein the second incident angle represents the angle between the grooved laser and the first surface, and the first incident angle is the same as the second incident angle.

[0011] Optionally, preheating the position where the first cutting line is located includes: controlling a heating device to preheat the position where the first cutting line is located according to a heating angle, wherein the heating angle represents an angle between the heating device and the first surface, and the heating angle is the same as the first incident angle.

[0012] Optionally, a cooling process is used to cool the position of the second cutting line of the scanned battery cell, including: controlling a cooling device to cool the position of the second cutting line of the scanned battery cell according to a cooling angle, wherein the cooling angle represents an angle between the cooling device and the second surface, and the cooling angle is the same as the heating angle.

[0013] Optionally, laser grooving is performed on both ends of the first cutting line, including: using a red laser to laser grooving the two ends of the first cutting line.

[0014] According to another aspect of the present application, a half-cell battery cell is provided, wherein the half-cell battery cell is prepared by any of the above-mentioned cell cutting methods, and the depth of the cross-sectional crack of the half-cell battery cell is 0.1 μm to 0.5 μm, and the direction of the depth is perpendicular to the cross-sectional direction of the half-cell battery cell.

[0015] By applying the technical solution of the present application, the position where the first cutting line is located is first preheated, and then the position where the first cutting line of the preheated battery cell is laser scanned. Finally, using a cooling process, the position where the second cutting line of the scanned battery cell is cooled, so that the cooled battery cell is split to obtain a half-cell battery cell. Compared with the existing laser scribing technology, in the process of preparing half-cut cells, the thermal damage to the surface and cross-section of the silicon wafer caused by the laser seriously affects the carrier transmission efficiency, thereby affecting the overall performance of the battery. Before using the thermal cracking laser to laser scan the battery cell, the present application first performs a preheating process (i.e., preheating the position where the first cutting line is located), so that the first surface of the battery cell can be preheated in advance. When the thermal cracking laser is subsequently used for laser scanning, a lower-power laser can be used for scanning. After the laser scanning, the back side (i.e., the second surface) of the battery cell is cooled by a cooling process, so that the cooled battery cell is split to obtain a half-cut battery cell. The front preheating and back cooling processes are combined, and the temperature gradient field is assisted by changing the external process temperature, thereby reducing the thermal cracking laser power and reducing the impact of thermal damage on the battery cell surface, which helps to improve the carrier transmission efficiency and battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0017] Figure 1 A schematic diagram of a process of cutting a battery cell provided in accordance with an embodiment of the present application is shown;

[0018] Figure 2A schematic structural diagram of a battery cell provided according to an embodiment of the present application is shown;

[0019] Figure 3 A schematic diagram of a front view structure of preheating a battery cell by using a heating device according to an embodiment of the present application is shown;

[0020] Figure 4 A schematic diagram of a front view structure of cooling a battery cell using a cooling device according to an embodiment of the present application is shown;

[0021] Figure 5 A schematic structural diagram of a half-cell obtained by cutting a cell according to an embodiment of the present application is shown;

[0022] Figure 6 A schematic diagram of a structure for grooving a battery cell according to an embodiment of the present application is shown.

[0023] The above drawings include the following reference numerals:

[0024] 10. Battery cell; 101. First surface; 102. Second surface; 11. First cutting line; 12. Second cutting line; 13. Hollow platform; 14. Heating device; 15. Cooling device; 16. Half battery cell; 103. End groove. DETAILED DESCRIPTION

[0025] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0026] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0027] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be intermediate elements. Moreover, in the specification and claims, when it is described that an element is "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element through a third element.

[0028] As introduced in the background technology, in the process of preparing half-cut cell by conventional laser scribing technology, thermal damage to the surface and cross-section of the silicon wafer caused by the laser seriously affects the carrier transmission efficiency, thereby affecting the overall performance of the cell. To solve the above problems, the embodiments of the present application provide a cell cutting method and a half-cut cell.

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0030] Figure 1 FIG. 1 is a flow chart of a method for cutting a battery cell according to an embodiment of the present application. Figures 2 to 6 As shown, the battery cell 10 includes a first surface 101 and a second surface 102 opposite to each other, a first cutting line 11 is located on the first surface 101, a second cutting line 12 is located on the second surface 102, and a projection of the first cutting line 11 on the second surface 102 overlaps with the second cutting line 12. Figure 1 As shown, the method comprises the following steps:

[0031] Step S101, as Figure 2 and Figure 3 As shown, the position where the first cutting line 11 is located is preheated;

[0032] Step S102, performing laser scanning on the position of the first cutting line of the preheated battery cell;

[0033] Step S103, as Figure 2 , Figure 4 and Figure 5 As shown, the position of the second cutting line 12 of the scanned battery cell 10 is cooled by a cooling process, so that the cooled battery cell 10 is split to obtain a half battery cell 16 .

[0034] Through this embodiment, the position where the first cutting line is located is first preheated, and then the position where the first cutting line of the preheated battery cell is laser scanned, and finally the position where the second cutting line of the scanned battery cell is cooled using a cooling process, so that the cooled battery cell is split to obtain a half-cell battery cell. Compared with the existing laser scribing technology, in the process of preparing half-cut cells, the thermal damage to the surface and cross-section of the silicon wafer caused by the laser seriously affects the carrier transmission efficiency, thereby affecting the overall performance of the battery. Before using the thermal cracking laser to laser scan the battery cell, the present application first performs a preheating process (i.e., preheating the position where the first cutting line is located), so that the first surface of the battery cell can be preheated in advance. When the thermal cracking laser is subsequently used for laser scanning, a lower-power laser can be used for scanning. After the laser scanning, the back side (i.e., the second surface) of the battery cell is cooled by a cooling process, so that the cooled battery cell is split to obtain a half-cut battery cell. The front preheating and back cooling processes are combined, and the temperature gradient field is assisted by changing the external process temperature, thereby reducing the thermal cracking laser power and reducing the impact of thermal damage on the battery cell surface, which helps to improve the carrier transmission efficiency and battery performance.

[0035] Specifically, the coverage width of the preheating area and the cooling area on the battery cell is greater than the radiation width of the laser scanning, and the direction of the width is perpendicular to the thickness of the battery cell.

[0036] In an optional solution, the position where the first cutting line is located is preheated, including: using a heating device to preheat the position where the first cutting line is located at a temperature of 80°C to 90°C, and using a cooling process to cool the position where the second cutting line of the scanned battery cell is located, including: using a cooling device to cool the position where the second cutting line of the scanned battery cell is located at a temperature of -10°C to 10°C, so that the cooled battery cell forms a temperature gradient field in a predetermined direction, and the predetermined direction represents at least one of the three crystal directions corresponding to the battery cell. In this embodiment, by controlling the preheating and cooling temperatures, the temperature gradient inside the battery cell can be accurately adjusted, thereby further guiding the crack to develop along the predetermined direction, thereby improving the cutting accuracy of the half-cell battery cell.

[0037] Specifically, a preheating process of 80°C to 90°C can be performed by spraying or other heating methods before the energy center of the thermal cracking laser (i.e., near the first cutting line). Other heating methods can be infrared preheating, laser preheating, hot air preheating, etc., which are not specifically limited in this application.

[0038] Specifically, cooling can be performed using a back refrigeration table, or water cooling, air cooling, gas cooling, etc., and this application does not impose any specific restrictions on this.

[0039] Specifically, Figure 3 and Figure 4 As shown, a hollow platform 13 is provided, and a hollow portion exists on the upper surface of the hollow platform 13; Figure 3 As shown, during preheating, the battery cell 10 can be placed inside the hollow platform, the position of the first cutting line (not shown) on the first surface 101 is aligned with the hollow portion, the heating device 14 is arranged on the upper part of the hollow platform 13, and the position of the first cutting line is preheated by the heating device 14; Figure 4 As shown, during cooling, the position of the second cutting line (not shown) on the second surface 102 is aligned with the hollow portion, and the cooling device 15 is disposed on the upper portion of the hollow platform 13, and the cooling device 15 is used to cool the position of the second cutting line.

[0040] According to some exemplary embodiments of the present application, laser scanning is performed on the position of the first cutting line of the preheated battery cell, including: using a laser with a laser power of 300W~600W, a laser frequency of 50Khz~200Khz, a scanning speed of 500mm / s~800mm / s and a circular spot diameter of 1mm~2mm to scan the position of the first cutting line of the preheated battery cell. In this embodiment, by optimizing the laser parameters, efficient and accurate cutting can be further achieved, while further reducing the heat-affected area of ​​the thermal cracking laser on the battery cell, further avoiding thermal damage, and improving the yield and reliability of half-cell batteries.

[0041] Specifically, the thermal cracking laser is a laser that performs laser scanning on the preheated battery cell.

[0042] In other embodiments, before preheating the position where the first cutting line is located, the method further includes: Figure 6 As shown, both ends of the first cutting line (not shown) are laser grooved to form end grooves 103. In this embodiment, by forming end grooves at both ends of the cutting line in advance, the starting position of the crack can be guided, so that the crack develops more stably along the predetermined path, further improving the cutting accuracy and the quality of the half-cell.

[0043] Specifically, the two ends of the first cutting line are two end points along the extending direction of the first cutting line.

[0044] Specifically, Figure 6As shown, the depth of the end groove 103 is 30% to 50% of the thickness of the battery cell 10, the length of the end groove 103 in the first direction is 1.2 mm to 2 mm, and the length of the end groove 103 in the second direction is 0.5 mm to 1.5 mm. The first direction is a direction perpendicular to the thickness of the battery cell 10, and the second direction is a direction perpendicular to the thickness of the battery cell 10. The first direction and the second direction are perpendicular to each other.

[0045] According to some other exemplary embodiments of the present application, laser grooving is performed on both ends of the first cutting line, including: using a laser with a laser power of 30W to 100W and a laser frequency of 50Khz to 200Khz to groove both ends of the first cutting line. In this embodiment, by controlling the laser power and frequency, it can be ensured that the formation of the end grooves will neither damage the battery cell nor affect the subsequent cutting process, thereby ensuring the continuity and stability of the cutting.

[0046] In some other optional schemes of the present application, laser scanning is performed on the position of the first cutting line of the preheated battery cell, including: laser scanning is performed on the position of the first cutting line after preheating according to a first incident angle, wherein the first incident angle represents the angle between the scanning laser and the first surface, and laser grooving is performed on both ends of the first cutting line, including: laser grooving is performed on both ends of the first cutting line according to a second incident angle, wherein the second incident angle represents the angle between the grooving laser and the first surface, and the first incident angle is the same as the second incident angle. In this embodiment, the first incident angle is the same as the second incident angle. By setting the same incident angle, it can be ensured that the direction of the force of the laser beam on the battery cell is consistent, which helps to further form a uniform thermal stress distribution.

[0047] Specifically, the second incident angle is 30°~60°.

[0048] In some other optional schemes of the present application, the position where the first cutting line is located is preheated, including: controlling the heating device to preheat the position where the first cutting line is located according to the heating angle, the heating angle represents the angle between the heating device and the first surface, and the heating angle is the same as the first incident angle. In this embodiment, the preheating angle is set to be the same as the laser cutting angle, so that the preheating and laser cutting are coordinated in the direction of energy action, and the heat energy in the preheating process is consistent with the subsequent laser energy action direction on the battery cell, which can more efficiently utilize the temperature gradient generated by the preheating, promote the precise expansion of the crack along the predetermined direction of the laser cutting path, and reduce the generation of cracks in unexpected directions. Preheating and laser cutting are performed at the same angle, which can more accurately control the cutting process. The consistency of the temperature gradient and the direction of the laser energy helps to ensure the controllability and cutting accuracy of the crack, avoids the different directions of the cracks caused by angle differences, and further improves the predictability of the cutting and the stability of the process.

[0049] In other embodiments, a cooling process is used to cool the position of the second cutting line of the scanned battery cell, including: controlling a cooling device to cool the position of the second cutting line of the scanned battery cell according to a cooling angle, wherein the cooling angle represents the angle between the cooling device and the second surface, and the cooling angle is the same as the heating angle. In this embodiment, by setting the cooling angle to be the same as the heating angle, a directional temperature gradient field can be formed on the front and rear surfaces of the battery cell. This temperature gradient field is established along the direction of the laser cutting path, which helps to accurately control the direction of crack expansion, ensure that the crack develops along the preset cutting line, and further reduce the generation of unexpected cracks.

[0050] Specifically, if the cooling method is gas cooling, the cooling angle is the angle between the gas outlet direction of the cooling device and the second surface.

[0051] Specifically, the angles of the thermal cracking laser and the preheating and cooling processes are all set to be consistent with the groove angle. By increasing the temperature gradient in a predetermined direction, the silicon wafer (i.e., the cell) reaches the fracture strength first along the predetermined direction, so that the silicon wafer first breaks and releases energy along this direction. By ensuring that thermal stress is released preferentially along the desired direction, the cross-sectional crack depth can be reduced from 3μm~5μm in the existing process to 0.1μm~0.5μm, reducing cross-sectional cracks, greatly improving cross-sectional morphology, reducing lattice defects, reducing composite density, improving carrier transport effects (increasing filling factor), improving cross-sectional flatness, enhancing cross-sectional passivation effects (increasing open circuit voltage), facilitating subsequent passivation film growth, and reducing cross-sectional recombination.

[0052] Specifically, the depth of the cross-sectional crack of the half-cell of the present application is 0.1 μm to 0.5 μm, and the direction of the depth is perpendicular to the cross-sectional direction of the half-cell, and the direction of the depth is perpendicular to the thickness of the cell.

[0053] Specifically, the battery cell of the present application may be of various types of battery structures, including but not limited to Topcon structure.

[0054] Specifically, the preparation process of the Topcon cell includes: providing an N-type silicon substrate; forming a P+ emitter on the upper surface of the silicon substrate; forming a tunneling layer on the lower surface of the silicon substrate; forming a passivation layer on the upper surface of the P+ emitter; forming an n+poly layer on the lower surface of the tunneling layer; forming a first anti-reflection film on the upper surface of the passivation layer; forming a second anti-reflection film on the lower surface of the n+poly layer; forming a plurality of first metal electrodes spaced apart on the upper surface of the first anti-emission layer; forming a plurality of second metal electrodes spaced apart on the lower surface of the second anti-reflection film. The first metal electrode is electrically connected to the P+ emitter, and the second metal electrode is electrically connected to the n+poly layer; the material of the passivation layer includes aluminum oxide, and the materials of the first anti-reflection film and the second anti-reflection film both include one of silicon oxide, silicon nitride or silicon oxynitride; the passivation layer and the anti-reflection film may be a single-layer structure or a multi-layer structure. For a multi-layer structure, the materials of different layers may be different from each other, or the materials of a part of the number of layers may be the same and different from the materials of other layers. Specifically, cutting can be performed after providing the N-type silicon substrate, or after forming the second metal electrode (i.e., preparing a complete Topcon battery), and the present application does not impose any specific restrictions on this; when cutting is performed after preparing a complete Topcon battery, the cutting line needs to be set at a position where no metal electrode exists.

[0055] In summary, the preheating and cooling technology of the present application assists in forming a temperature gradient field to achieve the thermal stress release conditions required for slicing, reduce the thermal cracking laser power, and reduce thermal damage; the temperature gradient field is formed in a direction so that the silicon wafer first reaches the fracture strength along the required specific direction, and preferentially releases thermal stress along this direction, reducing interface cracks and improving cross-sectional morphology, which is conducive to passivation. It should be noted that the existing cell cutting process generally grooves first, and then directly uses the thermal cracking laser to laser scan the cutting position of the cell. After scanning, the coolant mist is directly sprayed at the cutting position along the same trajectory to complete the cutting. The performance parameters of the half-cell obtained by the existing cutting process and the cell cutting method of the present application are shown in Table 1.

[0056] Table 1

[0057]

[0058] Specifically, in the performance parameters of Table 1, PMPP is the photovoltaic module power, Voc is the open circuit voltage, Isc is the short circuit current, and FF is the fill factor.

[0059] In other embodiments, laser grooving is performed on both ends of the first cutting line, including: laser grooving is performed on both ends of the first cutting line using a red laser.

[0060] Specifically, green lasers, green nano lasers, purple lasers, etc. with finer precision can also be used to make grooves, and this application does not make any specific restrictions on this.

[0061] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the implementation process of the battery cell cutting method of the present application will be described in detail below in combination with specific embodiments.

[0062] This embodiment relates to a specific method for cutting a battery cell, wherein the battery cell comprises a first surface and a second surface opposite to each other, a first cutting line is located on the first surface, a second cutting line is located on the second surface, and a projection of the first cutting line on the second surface overlaps with the second cutting line, comprising the following steps:

[0063] Step S1: using a laser with a laser power of 30W to 100W and a laser frequency of 50Khz to 200Khz to groove both ends of the first cutting line;

[0064] Step S2: After the slotting, the position where the first cutting line is located is preheated at a temperature of 80°C to 90°C using a heating device;

[0065] Step S3: Scan the position of the first cutting line of the preheated battery cell using a laser with a laser power of 300W to 600W, a laser frequency of 50Khz to 200Khz, a scanning speed of 500mm / s to 800mm / s, and a circular spot diameter of 1mm to 2mm;

[0066] Step S4: Use cooling equipment to cool the position of the second cutting line of the scanned battery cell at a temperature of -10°C to 10°C, so that the cooled battery cell is split to obtain a half-cell cell. The angles of laser scanning, preheating and cooling are all consistent with the slotting angle.

[0067] An embodiment of the present application also provides a half-cell battery cell, which is prepared by any of the above-mentioned battery cell cutting methods, and the depth of the cross-sectional crack of the above-mentioned half-cell battery cell is 0.1μm~0.5μm, and the direction of the above-mentioned depth is perpendicular to the cross-sectional direction of the above-mentioned half-cell battery cell.

[0068] In the above embodiment, a half-cell is prepared by a cell cutting method, wherein in the cell cutting method, the position where the first cutting line is located is first preheated, and then the position where the first cutting line of the preheated cell is laser scanned, and finally the position where the second cutting line of the scanned cell is cooled by a cooling process, so that the cooled cell is split to obtain a half-cell. Compared with the existing laser scribing technology, in the process of preparing half-cut cells, the thermal damage to the surface and cross-section of the silicon wafer caused by the laser seriously affects the carrier transmission efficiency, thereby affecting the overall performance of the battery. Before using the thermal cracking laser to laser scan the battery cell, the present application first performs a preheating process (i.e., preheating the position where the first cutting line is located), so that the first surface of the battery cell can be preheated in advance. When the thermal cracking laser is subsequently used for laser scanning, a lower-power laser can be used for scanning. After the laser scanning, the back side (i.e., the second surface) of the battery cell is cooled by a cooling process, so that the cooled battery cell is split to obtain a half-cut battery cell. The front preheating and back cooling processes are combined, and the temperature gradient field is assisted by changing the external process temperature, thereby reducing the thermal cracking laser power and reducing the impact of thermal damage on the battery cell surface, which helps to improve the carrier transmission efficiency and battery performance.

[0069] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0070] In the battery cell cutting method of the present application, the position where the first cutting line is located is first preheated, and then the position where the first cutting line of the preheated battery cell is laser scanned, and finally the position where the second cutting line of the scanned battery cell is cooled using a cooling process, so that the cooled battery cell is split to obtain a half-cell battery cell. Compared with the existing laser scribing technology, in the process of preparing half-cut cells, the thermal damage to the surface and cross-section of the silicon wafer caused by the laser seriously affects the carrier transmission efficiency, thereby affecting the overall performance of the battery. Before using the thermal cracking laser to laser scan the battery cell, the present application first performs a preheating process (i.e., preheating the position where the first cutting line is located), so that the first surface of the battery cell can be preheated in advance. When the thermal cracking laser is subsequently used for laser scanning, a lower-power laser can be used for scanning. After the laser scanning, the back side (i.e., the second surface) of the battery cell is cooled by a cooling process, so that the cooled battery cell is split to obtain a half-cut battery cell. The front preheating and back cooling processes are combined, and the temperature gradient field is assisted by changing the external process temperature, thereby reducing the thermal cracking laser power and reducing the impact of thermal damage on the battery cell surface, which helps to improve the carrier transmission efficiency and battery performance.

[0071] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for cutting a battery cell, characterized in that: The battery cell includes a first surface and a second surface opposite to each other, a first cutting line is located on the first surface, a second cutting line is located on the second surface, and a projection of the first cutting line on the second surface overlaps with the second cutting line. The method includes: Preheating the location of the first cutting line; Performing laser scanning on the position of the first cutting line of the preheated battery sheet; The position of the second cutting line of the scanned battery cell is cooled by a cooling process, so that the cooled battery cell is split to obtain a half battery cell.

2. The method for cutting a battery cell according to claim 1, characterized in that: Preheating the position where the first cutting line is located includes: using a heating device to preheat at a temperature of 80° C. to 90° C., The position of the second cutting line of the scanned battery cell is cooled using a cooling process, including: using a cooling device to cool at a temperature of -10°C to 10°C so that the cooled battery cell forms a temperature gradient field in a predetermined direction, and the predetermined direction represents at least one of the three crystal directions corresponding to the battery cell.

3. The method for cutting a battery cell according to claim 1, characterized in that: Performing laser scanning on the position of the first cutting line of the preheated battery sheet, comprising: The position of the first cutting line of the preheated battery cell is scanned by using a laser with a laser power of 300W-600W, a laser frequency of 50Khz-200Khz, a scanning speed of 500mm / s-800mm / s and a circular spot diameter of 1mm-2mm.

4. The method for cutting a battery cell according to claim 1, characterized in that: Before preheating the position where the first cutting line is located, the method further includes: Laser grooves are formed at two ends of the first cutting line to form end grooves.

5. The method for cutting a battery cell according to claim 4, characterized in that: Laser grooving is performed on both ends of the first cutting line, comprising: The two ends of the first cutting line are grooved by using a laser with a laser power of 30W-100W and a laser frequency of 50Khz-200Khz.

6. The method for cutting a battery cell according to claim 4, characterized in that: Performing laser scanning on the position of the first cutting line of the preheated battery cell, comprising: performing laser scanning at a first incident angle, wherein the first incident angle represents an angle between the scanning laser and the first surface, Laser grooving is performed on both ends of the first cutting line, including: laser grooving is performed according to a second incident angle, wherein the second incident angle represents an angle between a grooving laser and the first surface, and the first incident angle is the same as the second incident angle.

7. The method for cutting a battery cell according to claim 6, characterized in that: Preheating the position where the first cutting line is located includes: The heating device is controlled to perform preheating according to a heating angle, where the heating angle represents an angle between the heating device and the first surface, and the heating angle is the same as the first incident angle.

8. The method for cutting a battery cell according to claim 7, characterized in that: The scanning process is used to cool the position of the second cutting line of the battery sheet, including: The cooling device is controlled to perform cooling according to a cooling angle, where the cooling angle represents an angle between the cooling device and the second surface, and the cooling angle is the same as the heating angle.

9. The method for cutting a battery cell according to claim 4, characterized in that: Laser grooving is performed on both ends of the first cutting line, comprising: Laser grooving is performed using a red nano laser.

10. A half-cell battery cell, characterized in that: The half-cell battery cell is prepared by the cell cutting method according to any one of claims 1 to 8, the depth of the cross-sectional crack of the half-cell battery cell is 0.1 μm to 0.5 μm, and the direction of the depth is perpendicular to the cross-sectional direction of the half-cell battery cell.

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