Secondary battery preparation method, secondary battery, energy storage system and electrical equipment

Abstract

The present application relates to the field of battery technology, and discloses a method for preparing a secondary battery, a secondary battery, an energy storage system, and an electrical device. The method for preparing a secondary battery of the present application comprises: providing an electrode, which is a positive electrode or a negative electrode, and which is a electrode after a rolling operation; obtaining an actual porosity of the electrode; judging whether the electrode is qualified based on the actual porosity; if the electrode is qualified, sequentially rolling, blanking, cell assembly, liquid injection, and packaging the electrode to form a secondary battery; if the electrode is unqualified, laser processing the electrode to form laser pores; repeating the steps of obtaining the actual porosity of the electrode and judging whether the electrode is qualified based on the actual porosity until the electrode is qualified, thereby improving the uniformity of the electrode porosity, enhancing the wettability of the electrode, and improving the electrical performance of the secondary battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method for preparing a secondary battery, a secondary battery, an energy storage system, and electrical equipment. Background Art

[0002] In the manufacturing process of secondary batteries, electrode sheet preparation is a key step. The wettability of the electrode sheet plays an important role in improving the electrical performance of secondary batteries. The current secondary battery electrode sheet manufacturing process mainly includes electrode sheet loading, unwinding, electrode sheet rolling, thickness testing, and winding and unwinding.

[0003] However, the current manufacturing process of secondary batteries still has the problem of poor wettability of the electrode, which reduces the electrical performance of the secondary battery. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a method for preparing a secondary battery, a secondary battery, an energy storage system and an electrical device, thereby improving the uniformity of the porosity of the electrode, enhancing the wettability of the electrode, and improving the electrical performance of the secondary battery.

[0005] In order to solve the technical problem of poor electrical performance of secondary batteries caused by poor wettability of the above-mentioned electrode sheets, an embodiment of the present application provides a method for preparing a secondary battery, including: providing an electrode sheet, wherein the electrode sheet is a positive electrode sheet or a negative electrode sheet, and the electrode sheet is a electrode sheet after a rolling operation; obtaining the actual porosity of the electrode sheet; judging whether the electrode sheet is qualified based on the actual porosity; if the electrode sheet is qualified, the electrode sheet is sequentially rolled, blanked, assembled into a battery cell, injected with liquid, and packaged to form a secondary battery; if the electrode sheet is unqualified, the electrode sheet is laser processed to form laser pores; repeating the steps of obtaining the actual porosity of the electrode sheet and judging whether the electrode sheet is qualified based on the actual porosity until the electrode sheet is qualified.

[0006] An embodiment of the present application further provides a secondary battery, which is prepared by the above-mentioned method for preparing a secondary battery.

[0007] An embodiment of the present application further provides an energy storage system, comprising: a plurality of the above-mentioned secondary batteries.

[0008] An embodiment of the present application further provides an electrical device, including: the energy storage system as described above.

[0009] In some embodiments, judging whether the electrode is qualified based on the actual porosity includes: calculating the deviation between the actual porosity and the target porosity, the calculation formula of the deviation δ1 is: δ1=|δ-δ0|, wherein δ is the actual porosity, and δ0 is the target porosity; when the deviation is less than or equal to a preset threshold, the electrode is judged to be qualified; when the deviation is greater than the preset threshold, the electrode is judged to be unqualified, and the preset threshold is greater than 0 and less than or equal to 10%.

[0010] In some embodiments, the step of obtaining the actual porosity of the electrode piece includes: obtaining an image of the electrode piece; obtaining an area S of the electrode piece according to the image; total And the area S of the particle region in the pole piece solid According to the area S of the pole piece total , the area S of the particle region solid Obtain the actual porosity δ, the calculation formula of the actual porosity δ is: δ=1-S solid / S total .

[0011] In some embodiments, the step of acquiring the image of the pole piece includes: acquiring the image of the pole piece using a surface array CCD image sensor or a linear array CCD image sensor; the image is an image of a local area in the pole piece; and acquiring the area S of the pole piece according to the image. total And the area S of the particle region in the pole piece solid , including: obtaining the entire area of ​​the image as the area S of the pole piece total , and use the grayscale algorithm to calculate the area S of the particle region in the image solid .

[0012] In some embodiments, the laser aperture is a circular hole; before the laser processing of the pole piece to form the laser aperture, the method includes: obtaining the radius of the circular hole according to the deviation and the total area of ​​the pole piece, and the calculation formula of the radius r of the circular hole is: r=sqrt(3×δ1× S total / Pi); Pi is pi; S total is the total area of ​​the pole piece; the laser processing of the pole piece to form the laser aperture comprises: laser processing of the pole piece according to the radius r of the circular hole to form the laser aperture.

[0013] In some embodiments, the laser aperture is a long strip groove; before the laser processing of the pole piece to form the laser aperture, the method includes: obtaining the size of the long strip groove according to the deviation and the total area of ​​the pole piece; the size of the long strip groove includes the length and width of the long strip groove, and the calculation formula of the length L of the long strip groove is: L=3×δ1×S total / W,S total is the area of ​​the pole piece, W is the width of the long strip groove, and W is in the range of 0.05μm to 0.1μm; the laser processing of the pole piece to form the laser aperture includes: laser processing the pole piece according to the size of the long strip groove to form the laser aperture.

[0014] In some embodiments, before the pole piece is laser processed to form a laser pore, the method includes: obtaining the thickness of the pole piece, and determining the parameters of the laser processing according to the thickness, the parameters including power, pulse width, laser speed, laser temperature, and laser frequency; when the pole piece is a positive pole piece, the power is 10W to 50W, the pulse width is 10ps to 100ns, the laser speed is 500mm / s to 2800mm / s, the laser temperature is 100°C to 300°C, and the laser frequency is 180kHz to 400kHz; when the pole piece is a negative pole piece, the power is 5W to 30W, the pulse width is 10ps to 100ns, the laser speed is 400mm / s to 800mm / s, the laser temperature is 80°C to 200°C, and the laser frequency is 180kHz to 400kHz; the laser processing of the pole piece to form a laser pore includes: laser processing the pole piece according to the parameters of the laser processing to form the laser pore.

[0015] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0016] The embodiment of the present application detects the actual porosity of the electrode after the rolling operation, and determines whether the electrode is qualified based on the actual porosity of the electrode. If the electrode is determined to be qualified, the electrode is subsequently rolled, blanked, assembled, injected, and packaged to form a secondary battery. If the electrode is determined to be unqualified, the electrode is laser-processed to form laser pores to adjust the porosity of the electrode, and the actual porosity of the electrode is re-tested until the electrode is qualified. This can effectively identify and compensate for the defect of insufficient porosity in the electrode, improve the uniformity of the electrode porosity, enhance the wettability of the electrode, thereby improving the ion transmission performance of the electrode and improving the electrical performance of the secondary battery. In addition, the porosity detection and adjustment method added in the embodiment of the present application has a low process cost and high safety. While improving the wettability of the electrode, it also takes into account the process cost and safety of secondary battery preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0018] Figure 1 is a schematic flow chart of a method for preparing a secondary battery according to an embodiment of the present application;

[0019] Figure 2 It is a process flow chart of preparing a secondary battery according to the related art;

[0020] Figure 3 is a process flow chart for preparing a secondary battery according to an embodiment of the present application;

[0021] Figure 4 is a schematic flow chart of a method for preparing a secondary battery according to another embodiment of the present application;

[0022] Figure 5 is a schematic flow chart of a method for preparing a secondary battery according to another embodiment of the present application;

[0023] Figure 6 is a process flow chart of a method for preparing a secondary battery according to yet another embodiment of the present application;

[0024] Figure 7 is a schematic flow chart of a method for preparing a secondary battery according to another embodiment of the present application;

[0025] Figure 8 It is a schematic flow chart of a method for preparing a secondary battery according to another embodiment of the present application. DETAILED DESCRIPTION

[0026] As can be seen from the background art, the current manufacturing process of secondary batteries still has the problem of poor wettability of electrode pieces, thereby reducing the electrical performance of the secondary batteries.

[0027] Through analysis and research, it was found that in the preparation process of secondary batteries, when both the surface density and the rolling thickness fluctuate, there will inevitably be a problem of uneven pore structure in local areas of the electrode. The uneven pore structure will lead to local electrolyte drying up at the end of the cycle, and local failure will drive the overall failure of the battery cell, resulting in poor wettability of the electrode, thereby reducing the electrical performance of the secondary battery.

[0028] In order to solve the problem of poor wettability of the electrode in the secondary battery, the related art usually improves the wettability of the electrode by optimizing the injection process and optimizing the electrolyte formula. However, this method cannot improve the local wettability of the electrode, resulting in poor wettability of the electrode, and will also increase the process cost in the secondary battery preparation process and reduce the safety in the secondary battery preparation process. In order to solve the above technical problems, the embodiment of the present application provides a method for preparing a secondary battery, including: providing an electrode, the electrode is a positive electrode or a negative electrode, and the electrode is a electrode after a rolling operation; obtaining the actual porosity of the electrode; judging whether the electrode is qualified according to the actual porosity; if the electrode is qualified, the electrode is sequentially rolled, blanked, assembled, injected, and packaged to form a secondary battery; if the electrode is unqualified, the electrode is laser processed to form laser pores; repeating the steps of obtaining the actual porosity of the electrode and judging whether the electrode is qualified according to the actual porosity until the electrode is qualified.

[0029] The embodiment of the present application detects the actual porosity of the electrode after the rolling operation, and determines whether the electrode is qualified based on the actual porosity of the electrode. If the electrode is determined to be qualified, the electrode is subsequently rolled, blanked, assembled, injected, and packaged to form a secondary battery. If the electrode is determined to be unqualified, the electrode is laser-processed to form laser pores to adjust the porosity of the electrode, and the actual porosity of the electrode is re-tested until the electrode is qualified. This can effectively identify and compensate for the defect of insufficient porosity in the electrode, improve the uniformity of the electrode porosity, enhance the wettability of the electrode, thereby improving the ion transmission performance of the electrode and improving the electrical performance of the secondary battery. In addition, the porosity detection and adjustment method added in the embodiment of the present application has a low process cost and high safety. While improving the wettability of the electrode, it also takes into account the process cost and safety of secondary battery preparation.

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, each embodiment of the present application will be described in detail below with reference to the accompanying drawings. However, it will be understood by those skilled in the art that in each embodiment of the present application, many technical details are proposed to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can be implemented. The division of the following embodiments is for convenience of description and should not constitute any limitation on the specific implementation of the present application. The various embodiments can be combined and referenced with each other under the premise of no contradiction.

[0031] One embodiment of the present application relates to a method for preparing a secondary battery. The flow chart of the specific method for preparing a secondary battery is as follows: Figure 1 As shown, the method for preparing a secondary battery includes the following steps:

[0032] Step 101: providing a pole piece.

[0033] Specifically, the electrode sheet of this embodiment is a positive electrode sheet or a negative electrode sheet, and the electrode sheet is a electrode sheet after a rolling operation.

[0034] In the preparation process of secondary batteries, the preparation of pole pieces is one of the key links, such as Figure 2 The figure shows a process flow chart for the preparation of secondary batteries in the related art. The electrode preparation process in the related art includes electrode loading, unwinding, electrode rolling, thickness detection, and winding and unloading. Electrode loading is to place the prepared electrode or electrode roll onto the production line. The electrode roll needs to be installed on the unwinding device to ensure that the electrode can be smoothly unfolded. Unwinding is to unfold the electrode roll through the unwinding device and convey the electrode to the subsequent process through a conveyor belt or roller system. During the unwinding process, the tension of the electrode needs to be controlled to prevent the electrode from deformation or breakage. Pole rolling is to compact the electrode and the electrode coating through one or more pairs of rollers to prevent peeling during electrolyte immersion and battery use, thereby improving the density and mechanical strength of the electrode. Thickness detection After the electrode roll is rolled, the thickness detection is to detect the thickness of the electrode to ensure that the thickness of the electrode meets the process requirements. This embodiment simultaneously detects the thickness of the electrode sheet and the porosity of the electrode sheet, that is, simultaneously obtains the electrode sheet through the image sensor to improve the efficiency of secondary battery production. The electrode sheet winding is carried out by continuously processing the coiled material and gradually winding the coiled material into a large roll using a winder, thereby achieving efficient and low-loss storage and transportation of lithium battery electrode sheet coils. In fully automated production, the automatic guided vehicle will automatically receive the unloading shaft of the winding machine and transport the completed electrode sheet coil to the designated location.

[0035] The electrode provided in this embodiment is at least a electrode that has been subjected to a rolling operation. In order to further improve the electrode detection efficiency and avoid the subsequent porosity detection of electrode pieces with unqualified thickness, which reduces the electrode detection efficiency, the electrode provided in this embodiment can also be an electrode that has passed the thickness test, thereby improving the electrode detection efficiency and improving the secondary battery preparation efficiency. Figure 3 As shown, this is a process flow chart for preparing the secondary battery of this embodiment. In this embodiment, porosity detection is added after the electrode rolling and thickness detection. If qualified, the subsequent winding and unloading operation is carried out. If unqualified, the porosity is adjusted so that the subsequent winding and unloading operation can be carried out after the porosity of the electrode is qualified.

[0036] Step 102: Obtain the actual porosity of the electrode.

[0037] The actual porosity of the electrode of this embodiment refers to the actual porosity of a local area in the electrode. Since the entire electrode surface of the secondary battery includes multiple local areas, in actual applications, the porosity of each local area is detected separately, so that the porosity of the local area with unqualified porosity is adjusted to improve the uniformity of the electrode porosity. Due to the fluctuation of the surface density and rolling thickness of the electrode, the porosity of each local area in the electrode will be uneven, that is, the porosity of some areas is normal and the porosity of some areas is small, which leads to the problem of local electrolyte drying up and local failure leading to the failure of the entire battery cell at the end of the cycle of the secondary battery. Therefore, this embodiment detects the corresponding actual porosity of the local area of ​​the electrode, so as to detect the abnormal porosity area of ​​the electrode for subsequent porosity adjustment, improve the uniformity of the electrode porosity, improve the wettability of the electrode, and improve the performance of the prepared secondary battery.

[0038] Step 103: determine whether the electrode is qualified based on the actual porosity.

[0039] After obtaining the actual porosity of a local area in the electrode, this embodiment determines whether the electrode is qualified based on the actual porosity. If the actual porosity of the electrode satisfies a preset condition, the electrode is judged to be unqualified. If the actual porosity of the electrode satisfies a preset condition, the electrode is judged to be qualified. The preset condition is that the deviation between the actual porosity and the target porosity is less than or equal to a preset threshold.

[0040] Specifically, when the electrode includes multiple local areas, the porosity test is performed on each local area in the electrode. In the process of performing the porosity test on one of the local areas, if the actual porosity of the local area of ​​the electrode meets the preset conditions, the local area of ​​the electrode is judged to be qualified. If the actual porosity of the local area of ​​the electrode does not meet the preset conditions, the local area of ​​the electrode is judged to be unqualified. Thereafter, the porosity test is performed on the next local area of ​​the electrode, and the process is repeated in sequence until the porosity test is performed on multiple local areas of the electrode. In the process of performing the porosity test on each local area, as long as the actual porosity corresponding to a local area in the electrode does not meet the preset conditions, it will cause the problem of uneven porosity of the electrode, affecting the wettability of the electrode. Therefore, it is necessary to adjust the actual porosity of the local area that does not meet the preset conditions, thereby improving the actual porosity of the local area, making the porosity of each local area in the electrode uniform, and improving the wettability of the electrode.

[0041] Specifically, this embodiment performs different treatments when a local area of ​​the electrode is qualified or a local area of ​​the electrode is unqualified. When the local area of ​​the electrode is qualified, this embodiment enters step 104, i.e., the electrode is rolled, blanked, assembled with cells, injected, and packaged in sequence to form a secondary battery. When the local area of ​​the electrode is unqualified, the embodiment enters step 105, i.e., the electrode is laser-processed to form laser pores, i.e., the local area of ​​the electrode is laser-processed to form laser pores, thereby increasing the porosity of the local area, increasing the uniformity of the electrode porosity, and increasing the wettability of the electrode.

[0042] Specifically, in the case where the electrode includes multiple local areas, the porosity of each local area in the electrode is tested separately. If the porosity of each local area meets the preset conditions, that is, each local area is qualified, the subsequent steps of winding, unloading, cell assembly, liquid injection, and packaging the electrode are carried out in sequence to form a secondary battery. If the porosity of any local area does not meet the preset conditions, that is, any local area is unqualified, the local area is laser treated to form laser pores, thereby increasing the porosity of the local area, improving the uniformity of the electrode porosity, and improving the wettability of the electrode.

[0043] Step 104 , the electrode sheets are sequentially rolled, cut, assembled, injected, and packaged to form a secondary battery.

[0044] Specifically, in this embodiment, if the electrode sheet is qualified, subsequent winding and blanking operations are performed on the electrode sheet, and then the battery cell is assembled, injected, and packaged to form a secondary battery.

[0045] Cell assembly includes lamination or winding, center pin insertion, and cell encapsulation. Lamination or winding involves alternately stacking or winding the positive electrode sheets, separators, and negative electrode sheets into a cell, depending on the design of the secondary battery. The separator is used to separate the positive and negative electrodes to prevent short circuits. Center pin insertion is used to secure the cell structure in wound cells. Cell encapsulation involves placing the assembled cell into the battery casing and placing insulators on both sides. Electrolyte injection involves injecting electrolyte into the battery casing to fully saturate the cell. The electrolyte typically consists of electrolyte salts, solvents, and additives. Encapsulation involves sealing the battery casing and lid by welding or other means to ensure a tight seal.

[0046] Step 105 , performing laser processing on the pole piece to form a laser aperture.

[0047] In this embodiment, laser processing is performed on the pole piece to form laser pores, that is, laser processing is performed on a local area of ​​the pole piece to form laser pores. The local area is a local area where the actual porosity does not meet the preset conditions. Therefore, it is necessary to laser process the local area to increase the porosity of the local area, thereby improving the uniformity of the overall porosity of the pole piece and improving the wettability of the pole piece.

[0048] The laser used in this embodiment can be a nanosecond laser, a picosecond laser, a femtosecond laser, etc. Laser processing is performed by the laser perpendicular to the pole piece to form laser pores, thereby improving the porosity of the local area.

[0049] In this embodiment, after the electrode is laser processed to form laser pores, step 102, i.e., the step of re-obtaining the actual porosity of the local area in the electrode, and step 103, i.e., the step of judging whether the electrode is qualified based on the actual porosity of the local area, are repeated until the electrode is qualified, i.e., the local area of ​​the electrode is qualified.

[0050] Specifically, the electrode is in the shape of a long strip, for example, the length of the electrode is 800 mm and the width is 50 mm. The local area of ​​this embodiment is a partial area of ​​the electrode. For example, the electrode is divided into multiple local areas only in the length direction, and the length of each local area is 50 mm and the width is 50 mm. Alternatively, the electrode is divided into two equal parts in the width direction and divided into multiple local areas in the length direction, and the length of each local area is 25 mm and the width is 25 mm.

[0051] This embodiment detects and adjusts the porosity of each local area, so that when the porosity of each local area does not meet the requirements, the local area is laser treated to improve the porosity of the local area, and the uniformity of the porosity of multiple local areas in the electrode is improved, thereby improving the wettability of the electrode.

[0052] In actual applications, if the porosity is very uneven, that is, the porosity of some local areas is larger, the porosity of some local areas is smaller, and the deviation between the actual porosity of the local areas with larger porosity and the target porosity exceeds the preset threshold, the porosity of the area cannot be reduced. Therefore, this type of electrode cannot be formed into a qualified product through laser processing and can be directly screened out for scrapping.

[0053] This embodiment detects the actual porosity of the electrode sheet after the electrode sheet is rolled, and determines whether the electrode sheet is qualified based on the actual porosity of the electrode sheet. If the electrode sheet is determined to be qualified, the electrode sheet is subsequently rolled, blanked, assembled, injected, and packaged to form a secondary battery. If the actual porosity of any area of ​​the electrode sheet does not meet the preset conditions, if the electrode sheet is determined to be unqualified, the electrode sheet is laser-processed to form laser pores to adjust the porosity of the electrode sheet, and the actual porosity of the electrode sheet is re-detected until the electrode sheet is qualified. This can effectively identify and compensate for the defect of insufficient porosity in the electrode sheet, improve the uniformity of the electrode sheet porosity, enhance the wettability of the electrode sheet, thereby improving the ion transmission performance of the electrode sheet and improving the electrical performance of the secondary battery. In addition, the porosity detection and adjustment method added in the embodiment of the present application has a low process cost and high safety. While improving the wettability of the electrode sheet, it also takes into account the process cost and safety of the secondary battery preparation.

[0054] Figure 2 The related technology shown is Comparative Example 1 of the present embodiment. The preparation method of the secondary battery of the present embodiment, namely Example 1, has a significant improvement in performance relative to the process of Comparative Example 1. Referring to the technical effect comparison table shown in Table 1, it can be seen that the cell soaking time of the secondary battery in Comparative Example 1 is 24 hours, and the 0.5P cycle life-capacity retention rate of the secondary battery is 95.7%@500 weeks. 95.7%@500 weeks means that after the secondary battery completes 500 complete charge and discharge cycles under standard conditions, the remaining capacity is 95.7% of the initial capacity, and the fully charged interface of the secondary battery occasionally has brown spots. The cell soaking time of the present embodiment, namely Example 1, is 16 hours, and the cell soaking time is shortened by 8 hours. The 0.5P cycle life-capacity retention rate of the secondary battery is 96.5%@500 weeks. 96.5%@500 weeks means that after the secondary battery completes 500 complete charge and discharge cycles under standard conditions, the remaining capacity is 96.5% of the initial capacity, and the fully charged interface of the secondary battery has no brown spots.

[0055] It can be seen that compared with Comparative Example 1, the cell soaking time, 0.5P cycle life-capacity retention rate, and full charge interface of Example 1 are all improved, thereby improving the wettability of the electrode and improving the performance of the cell.

[0056] Table 1

[0057]

[0058] Another embodiment of the present application relates to a method for preparing a secondary battery. This embodiment further defines the preset condition as the deviation between the actual porosity and the target porosity is less than or equal to a preset threshold, and further refines the above step 103, that is, judging whether the electrode is qualified according to the actual porosity. The flow chart of the method for preparing a secondary battery of this embodiment is as follows: Figure 4 As shown, the method for preparing the secondary battery of this embodiment includes the following steps:

[0059] Step 201: providing a pole piece.

[0060] Step 202: Obtain the actual porosity of the electrode.

[0061] Step 203: Calculate the deviation between the actual porosity and the target porosity.

[0062] After obtaining the actual porosity of a local region of the electrode, this embodiment calculates the deviation between the actual porosity of that local region and the target porosity. In some embodiments, the deviation δ1 is calculated as: δ1 = |δ - δ0|, where δ is the actual porosity and δ0 is the target porosity. For example, if the actual porosity δ is 35% and the target porosity is set to 40%, the calculated deviation δ1 is |35% - 40%| = 5%.

[0063] Step 204: determine whether the electrode is qualified based on the deviation.

[0064] This embodiment determines whether the electrode is qualified by the deviation corresponding to the local area. That is, as long as the deviation corresponding to a local area in the electrode is greater than the preset threshold, it will cause the porosity of the electrode to be uneven, affecting the wettability of the electrode. Therefore, it is necessary to adjust the actual porosity of the area where the deviation is greater than the preset threshold, so as to increase the actual porosity of the area, make the porosity of each local area in the electrode uniform, and improve the wettability of the electrode.

[0065] In some embodiments, the preset threshold is greater than 0 and less than or equal to 10%, such as 2%, 4%, 6%, 8%, or 10%. Specifically, the preset threshold can be in the range of 0 to 6%, or in the range of 0 to 4%. For example, the target porosity is set to 40%, and the preset threshold is set to 10%. By calculating the actual porosity of a local area of ​​the electrode, if the actual porosity of a local area of ​​the electrode is 35%, the deviation between the actual porosity of 35% of the local area and the target porosity of 40% is 5%, which is less than the preset threshold of 10%, then the local area of ​​the electrode is determined to be qualified; if the actual porosity of a local area of ​​the electrode is 25%, the deviation between the actual porosity of the area and the target porosity of 40% is 15%, which is greater than the preset threshold of 10%, then the local area of ​​the electrode is determined to be unqualified. Subsequently, the local area is laser treated to form laser pores, thereby increasing the actual porosity of the local area, increasing the uniformity of the electrode porosity, and increasing the wettability of the electrode.

[0066] Specifically, if the electrode is qualified, the process proceeds to step 205, i.e. the electrode is rolled, blanked, assembled, injected, and packaged in sequence to form a secondary battery. If the electrode is unqualified, the process proceeds to step 206, i.e. the electrode is laser processed to form laser pores, thereby increasing the actual porosity of the local area of ​​the electrode, improving the uniformity of the electrode porosity, and improving the wettability of the electrode.

[0067] Step 205 , winding, cutting, cell assembly, liquid injection, and packaging the electrode sheets in sequence to form a secondary battery.

[0068] Step 206 , performing laser processing on the pole piece to form a laser aperture.

[0069] In this embodiment, after the electrode is laser processed to form laser pores, step 202, i.e., obtaining the actual porosity of the electrode, step 203, i.e., calculating the deviation between the actual porosity and the target porosity, and step 204, i.e., determining whether the electrode is qualified based on the deviation, are repeated until the electrode is qualified.

[0070] The above steps 201, 202, 205 and 206 of this embodiment are substantially the same as steps 101, 102, 104 and 105 of the previous embodiment, and will not be described again to avoid repetition.

[0071] This embodiment calculates the deviation between the actual porosity of the electrode and the target porosity, and determines whether the electrode is qualified based on the deviation. If the electrode is qualified, the electrode is sequentially rolled, blanked, assembled into battery cells, injected with liquid, and packaged to form a secondary battery. If the electrode is unqualified, the electrode is laser processed to form laser pores, thereby improving the uniformity of the electrode porosity and improving the wettability of the electrode.

[0072] Another embodiment of the present application relates to a method for preparing a secondary battery. This embodiment further defines a method for obtaining the actual porosity of the electrode. The flow chart of the method for preparing a secondary battery of this embodiment is as follows: Figure 5 As shown, the method for preparing the secondary battery of this embodiment includes the following steps:

[0073] Step 301: providing a pole piece.

[0074] Step 302: Acquire an image of the electrode.

[0075] Step 303: Obtain the area S of the electrode according to the image total And the area S of the particle region in the pole piece solid .

[0076] Step 304: Based on the area S of the electrode total , the area of ​​the particle region S solid Get the actual porosity δ.

[0077] Specifically, this embodiment obtains the actual porosity of a local area in the electrode. In order to obtain the actual porosity of a local area in the electrode, the image corresponding to the electrode is first obtained. The image is an image of the local area in the electrode. Then, the area S of the local area of ​​the electrode is obtained according to the image. total And the area S of the particle area in the local area of ​​the pole piece solid , according to the area S of the local area of ​​the pole piece total , the area of ​​the particle region S solid Obtain the actual porosity δ corresponding to the local area of ​​the electrode. The calculation formula of the actual porosity δ is: δ=1-S solid / S total .

[0078] In some embodiments, step 302, namely acquiring an image of the pole piece, is achieved by using an area array CCD (Charge-Coupled Device) image sensor or a linear array CDD image sensor to acquire an image corresponding to a local area in the pole piece.

[0079] The pixels of the area array CCD image sensor are arranged in a two-dimensional matrix form, which can simultaneously capture the image of each local area in the electrode. The area array CCD image sensor of this embodiment can be a frame transfer area array CCD or an interline transfer area array CCD. The two have different working modes. After exposure, the frame transfer area array CCD transfers the charge accumulated in the photosensitive unit to the storage unit and then reads it. After exposure, the interline transfer area array CCD transfers the charge from the photosensitive unit to the adjacent storage unit, and at the same time, the next row of photosensitive units are ready for exposure.

[0080] The pixels of a linear array CCD image sensor are arranged in a straight line, and can only capture one row of pixels at a time. The linear array CCD image sensor captures images through a line-by-line scanning method, which allows for faster image acquisition. The linear array CCD image sensor of this embodiment can be either a single-channel linear array CCD or a dual-channel linear array CCD. The dual-channel linear array CCD has higher transfer efficiency, which is more conducive to increasing image acquisition speed and improving the efficiency of porosity detection.

[0081] Correspondingly, step 303 of this embodiment is to obtain the area of ​​the electrode piece and the area of ​​the particle region in the electrode piece according to the image, which is achieved by: obtaining the overall area of ​​the image as the area S of the local area of ​​the electrode piece total , and use the grayscale algorithm to calculate the area S of the particle area in the local area solid That is, for each local area image in the pole piece, the area S of the local area corresponding to the image is obtained. total And the area S of the particle region in the image solid , according to the calculation formula of actual porosity δ = 1-S solid / S total The actual porosity δ of the local area is calculated.

[0082] Step 305: determine whether the electrode is qualified based on the actual porosity.

[0083] Specifically, after obtaining the actual porosity of the local area of ​​the electrode, this embodiment calculates the deviation between the actual porosity and the target porosity, judges whether the electrode is qualified based on the deviation, and adjusts the actual porosity of the local area where the deviation is greater than the preset threshold, thereby improving the actual porosity of the local area of ​​the electrode, improving the uniformity of the electrode porosity, and improving the wettability of the electrode.

[0084] Specifically, if the electrode is qualified, the process proceeds to step 306, i.e. the electrode is rolled, blanked, assembled, injected, and packaged in sequence to form a secondary battery. If the electrode is unqualified, the process proceeds to step 307, i.e. the electrode is laser processed to form laser pores, thereby improving the uniformity of the electrode porosity and improving the wettability of the electrode.

[0085] In step 306 , the electrode sheets are sequentially rolled, cut, assembled, injected, and packaged to form a secondary battery.

[0086] Step 307 : performing laser processing on the pole piece to form a laser aperture.

[0087] In this embodiment, after the electrode is laser processed to form a laser aperture, the process re-enters step 302, which is the step of obtaining an image of the electrode, and step 303, which is the step of obtaining the area S of the electrode according to the image. total And the area S of the particle region in the pole piece solid Step 304 is based on the area S of the electrode total , the area of ​​the particle region S solid The step of obtaining the actual porosity δ, step 305 , is the step of judging whether the electrode piece is qualified according to the actual porosity, and this process is continued until the electrode piece is qualified.

[0088] The above steps 301, 305, 306 and 307 of this embodiment are substantially the same as steps 101, 103, 104 and 105 of the previous embodiment, and will not be described again to avoid repetition.

[0089] Another embodiment of the present application relates to a method for preparing a secondary battery, which further defines the laser aperture as a circular hole; before laser processing the pole piece to form the laser aperture, the method includes: obtaining the radius of the circular hole based on the deviation and the area of ​​the pole piece, and laser processing the pole piece to form the laser aperture, including: laser processing the pole piece according to the radius r of the circular hole to form the laser aperture.

[0090] The schematic flow chart of the method for preparing the secondary battery of this embodiment is as follows: Figure 6 As shown, the method for preparing the secondary battery of this embodiment includes the following steps:

[0091] Step 401: providing a pole piece.

[0092] Step 402: Acquire an image of the electrode.

[0093] Step 403: Obtain the area S of the electrode according to the image total And the area S of the particle region in the pole piece solid .

[0094] Step 404: Based on the area S of the electrode total, the area of ​​the particle region S solid Get the actual porosity δ.

[0095] Step 405 : Calculate the deviation between the actual porosity and the target porosity.

[0096] Step 406: Determine whether the electrode is qualified based on the deviation.

[0097] Specifically, if the electrode piece is qualified, the process proceeds to step 407 , and if the electrode piece is unqualified, the process proceeds to step 408 .

[0098] Step 407 , winding, cutting, cell assembly, liquid injection, and packaging the electrode sheets in sequence to form a secondary battery.

[0099] Step 408 : Obtain the radius of the circular hole according to the deviation and the area of ​​the electrode.

[0100] Step 409 : laser processing the pole piece according to the radius of the circular hole to form a laser aperture.

[0101] After the electrode is deemed unqualified, this embodiment requires laser treatment of a local area of ​​the electrode to form laser porosity. The purpose of laser treatment is to increase the actual porosity of the local area, so that the deviation between the actual porosity of the local area and the target porosity is less than or equal to a preset threshold. However, the actual porosity of different local areas varies. If the same laser treatment parameters are used, the porosity of the local area with a smaller actual porosity cannot be effectively improved, thereby reducing the efficiency and accuracy of porosity adjustment.

[0102] In order to further improve the efficiency and accuracy of porosity adjustment, the laser pores processed by the laser are set as circular holes. The radius of the circular hole is obtained according to the deviation corresponding to the local area and the total area of ​​the local area. The calculation formula of the radius r of the circular hole is: r = sqrt (3 × δ1 × S total / Pi), δ1 is the deviation between the actual porosity and the target porosity, Pi is the pi, S total is the area of ​​the pole piece, that is, the area of ​​the local area in the pole piece; then, the local area in the pole piece is laser processed according to the radius r of the circular hole to form a laser aperture, that is, a circular hole, so that the corresponding laser parameters are set according to the actual situation of the local area, thereby adjusting the porosity of the local area, thereby improving the efficiency and accuracy of the porosity adjustment.

[0103] In this embodiment, after laser processing is performed on a local area of ​​the electrode to form a laser aperture, the process re-enters step 402, i.e., obtaining an image of the electrode, and step 403, i.e., obtaining the area S of the electrode according to the image. total And the area S of the particle region in the pole piece solid Step 404 is based on the area S of the electrodetotal , the area of ​​the particle region S solid The steps of obtaining the actual porosity δ, step 405 ie calculating the deviation between the actual porosity and the target porosity, and step 406 ie judging whether the electrode piece is qualified according to the deviation are repeated until the electrode piece is qualified.

[0104] The above steps 401 to 404 of this embodiment are substantially the same as steps 301 to 304 of the previous embodiment, and the above steps 405 to 407 are substantially the same as steps 203 to 205 of the above embodiment. To avoid repetition, they are not described again here.

[0105] This embodiment sets the laser aperture as a circular hole, obtains the radius of the circular hole based on the deviation corresponding to the local area of ​​the pole piece and the area of ​​the local area, and performs laser processing on the local area in the pole piece according to the radius of the circular hole to form a laser aperture, thereby setting the corresponding laser parameters according to the actual situation of the local area, thereby adjusting the porosity of the local area and improving the efficiency and accuracy of the porosity adjustment.

[0106] The optimization liquid injection process and electrolyte formulation of the related technology are comparative example 2 of this embodiment. Referring to the technical effect comparison table shown in Table 2, it can be seen that in comparative example 2, the battery cell immersion time of the secondary battery is 20 hours, and the 0.5P cycle life-capacity retention rate of the secondary battery is 95.8%@500 weeks. 95.8%@500 weeks means that after the secondary battery completes 500 complete charge and discharge cycles under standard conditions, the remaining capacity is 95.8% of the initial capacity, and the interface of the fully charged interface of the secondary battery is uniform and free of brown spots; while the battery cell immersion time of the secondary battery of this embodiment, i.e., Example 2, is 16 hours, and the 0.5P cycle life-capacity retention rate of the secondary battery is 96.5%@500 weeks. 96.5%@500 weeks means that after the secondary battery completes 500 complete charge and discharge cycles under standard conditions, the remaining capacity is 96.5% of the initial capacity, and the interface of the fully charged interface of the secondary battery is uniform and free of brown spots.

[0107] It can be seen that compared with Comparative Example 2, there is no obvious change in the full charge interface of Example 2, but the cell infiltration time is significantly reduced, and the 0.5P cycle life-capacity retention rate is also improved, which improves the wettability of the electrode and improves the performance of the battery cell.

[0108] Table 2

[0109]

[0110] Another embodiment of the present application relates to a method for preparing a secondary battery, which further defines the laser aperture as a long strip groove; before laser processing the pole piece to form the laser aperture, it includes: obtaining the size of the long strip groove based on the deviation and the area of ​​the pole piece; laser processing the pole piece to form the laser aperture includes: laser processing the pole piece according to the size of the long strip groove to form the laser aperture.

[0111] The schematic flow chart of the method for preparing the secondary battery of this embodiment is as follows: Figure 7 As shown, the method for preparing the secondary battery of this embodiment includes the following steps:

[0112] Step 501: providing a pole piece.

[0113] Step 502: Acquire an image of the electrode.

[0114] Step 503: Obtain the area S of the electrode according to the image total And the area S of the particle region in the pole piece solid .

[0115] Step 504: Based on the area S of the electrode total , the area of ​​the particle region S solid Get the actual porosity δ.

[0116] Step 505 : Calculate the deviation between the actual porosity and the target porosity.

[0117] Step 506: Determine whether the electrode is qualified based on the deviation.

[0118] If the electrode is qualified, the process goes to step 507 ; if the electrode is unqualified, the process goes to step 508 .

[0119] Step 507 , winding, cutting, cell assembly, liquid injection, and packaging the electrode sheets in sequence to form a secondary battery.

[0120] Step 508 : Obtain the size of the long strip groove according to the deviation and the area of ​​the pole piece.

[0121] Step 509 : Laser process the pole piece according to the size of the long strip groove to form a laser aperture.

[0122] After the electrode is deemed unqualified, this embodiment requires laser treatment of a local area of ​​the electrode to form laser porosity. The purpose of laser treatment is to increase the actual porosity of the local area, so that the deviation between the actual porosity of the local area and the target porosity is less than or equal to a preset threshold. However, the actual porosity of different layout areas varies. If the same laser treatment parameters are used, the porosity of the local area with a smaller actual porosity cannot be effectively improved, reducing the efficiency and accuracy of porosity adjustment.

[0123] In order to further improve the efficiency and accuracy of porosity adjustment in this embodiment, the laser-processed laser pores are set as long strip grooves, and the size of the long strip grooves is obtained according to the deviation corresponding to the local area and the total area of ​​the local area.

[0124] The size of the long strip groove includes the length and width of the long strip groove. The calculation formula of the length L of the long strip groove is: L=3×δ1×S total / W, δ1 is the deviation between the actual porosity and the target porosity, S total is the area of ​​the pole piece, that is, the area of ​​the local area in the pole piece, W is the width of the long strip groove, W is a fixed value in the range of 0.05μm to 0.1μm, for example, 0.05μm, 0.06μm, 0.07μm, 0.08μm, 0.09μm, 0.1μm.

[0125] Afterwards, the local area in the pole piece is laser processed according to the size of the long strip groove to form a laser pore, i.e., a long strip groove, so that the corresponding laser parameters are set according to the actual situation of the local area, thereby adjusting the porosity of the local area, thereby improving the efficiency and accuracy of the porosity adjustment.

[0126] In this embodiment, after the electrode is laser processed to form a laser aperture, the process re-enters step 502, which is the step of obtaining an image of the electrode, and step 503, which is the step of obtaining the area S of the electrode according to the image. total And the area S of the particle region in the pole piece solid Step 504 is based on the total area S of the electrode total , the area of ​​the particle region S solid The steps of obtaining the actual porosity δ, step 505 ie calculating the deviation between the actual porosity and the target porosity, and step 506 ie judging whether the electrode piece is qualified according to the deviation are repeated until the electrode piece is qualified.

[0127] The above steps 501 to 507 of this embodiment are substantially the same as steps 401 to 407 of the previous embodiment, and are not described again here to avoid repetition.

[0128] This embodiment sets the laser aperture as a long strip groove, obtains the size of the long strip groove according to the deviation corresponding to the local area of ​​the pole piece and the total area of ​​the local area, and performs laser processing on the local area of ​​the pole piece according to the size of the long strip groove to form a laser aperture, thereby setting the corresponding laser parameters according to the actual situation of the layout area, thereby adjusting the porosity of the local area, and improving the efficiency and accuracy of the porosity adjustment.

[0129] The optimization liquid injection process and electrolyte formulation of the related technology are comparative example 2 of this embodiment. Referring to the technical effect comparison table shown in Table 3, it can be seen that in comparative example 2, the battery cell immersion time of the secondary battery is 20 hours, and the 0.5P cycle life-capacity retention rate of the secondary battery is 95.8%@500 weeks. 95.8%@500 weeks means that after the secondary battery completes 500 complete charge and discharge cycles under standard conditions, the remaining capacity is 95.8% of the initial capacity, and the interface of the fully charged interface of the secondary battery is uniform and free of brown spots; while the battery cell immersion time of the secondary battery of this embodiment, i.e., Example 3, is 16 hours, and the 0.5P cycle life-capacity retention rate of the secondary battery is 96.4%@500 weeks. 96.4%@500 weeks means that after the secondary battery completes 500 complete charge and discharge cycles under standard conditions, the remaining capacity is 96.4% of the initial capacity, and the interface of the fully charged interface of the secondary battery is uniform and free of brown spots.

[0130] It can be seen that compared with Example 2, the full charge interface of Example 3 has no obvious change, but the cell infiltration time is significantly reduced, and the 0.5P cycle life-capacity retention rate is improved, which improves the wettability of the electrode and improves the performance of the battery cell.

[0131] Table 3

[0132]

[0133] Another embodiment of the present application relates to a method for preparing a secondary battery. This embodiment further defines that before laser processing the electrode to form a laser aperture, the thickness of the electrode is obtained, and the parameters of the laser processing are determined according to the thickness. The flow diagram of the method for preparing a secondary battery in this embodiment is as follows: Figure 8 As shown, the method for preparing the secondary battery of this embodiment includes the following steps:

[0134] Step 601: providing a pole piece.

[0135] Step 602: Obtain the actual porosity of the electrode.

[0136] Step 603: Determine whether the electrode is qualified based on the actual porosity.

[0137] In step 604 , the electrode sheets are sequentially rolled, cut, assembled, injected, and packaged to form a secondary battery.

[0138] Step 605: Obtain the thickness of the electrode and determine the parameters of the laser processing according to the thickness.

[0139] In this embodiment, the parameters of the laser processing include power, pulse width, laser speed, laser temperature, and laser frequency.

[0140] Wherein, when the electrode is a positive electrode, the power is 10W to 50W, for example, 10W, 20W, 30W, 40W, 50W; the pulse width is 10ps to 100ns, for example, 10ps, 20ps, 30ps, 40ps, 50ps, 60ps, 70ps, 80ps, 90ps, 100ps; the laser speed is 500mm / s to 2800mm / s, for example, 500mm / s, 800mm / s, 1 000mm / s, 1500mm / s, 2000mm / s, 2500mm / s, 2800mm / s; the laser temperature is 100°C to 300°C, for example, 100°C, 150°C, 200°C, 250°C, 300°C; the laser frequency is 180kHz to 400kHz, for example, 180kHz, 200kHz, 250kHz, 300kHz, 350kHz, 400kHz.

[0141] When the electrode is a negative electrode, the power is 5W to 30W, for example, 5W, 15W, 20W, 25W, 30W; the pulse width is 10ps to 100ns, for example, 10ps, 20ps, 30ps, 40ps, 50ps, 60ps, 70ps, 80ps, 90ps, 100ps; the laser speed is 400mm / s to 800mm / s, for example, 400mm / s, 500mm / s , 600mm / s, 700mm / s, 800mm / s; the laser temperature is 80°C to 200°C, for example, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C; the laser frequency is 180kHz to 400kHz, for example, 180kHz, 200kHz, 250kHz, 300kHz, 350kHz, 400kHz.

[0142] The electrode thickness obtained in this embodiment can directly obtain the electrode thickness recorded during the electrode thickness detection process, thereby improving the efficiency of laser processing and improving the efficiency of porosity adjustment.

[0143] Step 606 , performing laser processing on the pole piece according to the laser processing parameters to form a laser aperture.

[0144] If the same laser processing parameters are used for pole pieces of different thicknesses, there is a risk of reduced laser processing efficiency and inability to effectively adjust the porosity. Therefore, this embodiment determines the laser processing parameters, including power, pulse width, laser speed, and laser temperature, based on the thickness of the pole piece. The pole piece is laser processed according to the laser processing parameters to form laser pores, thereby improving the laser processing efficiency and the accuracy of porosity adjustment.

[0145] In this embodiment, after the electrode is laser processed to form the laser aperture, the process re-enters step 602 and step 603 until the electrode is qualified.

[0146] The above steps 601 to 604 of this embodiment are substantially the same as steps 101 to 104 of the above embodiment, and will not be described again to avoid repetition.

[0147] On the other hand, the present application provides a secondary battery, which is prepared by the secondary battery preparation method of the above embodiment.

[0148] The secondary battery of this embodiment is prepared by the preparation method of the secondary battery of the above embodiment. The secondary battery is a qualified secondary battery that has passed the porosity test, which improves the wettability of the electrode in the secondary battery, thereby improving the ion transmission performance of the electrode of the secondary battery and improving the electrical performance of the secondary battery.

[0149] Specifically, the electrode of the secondary battery of this embodiment undergoes electrode loading, unwinding, electrode rolling, thickness detection, porosity detection, and winding and unloading. After the electrode winding and unloading are completed, the electrode is subjected to subsequent winding and unloading operations, and then the battery cell is assembled, injected, and packaged to form a secondary battery.

[0150] In another aspect, the present application provides an energy storage system, comprising: a plurality of secondary batteries according to the above embodiments.

[0151] The energy storage system of this embodiment includes multiple secondary batteries of the above embodiments, wherein the secondary batteries are qualified secondary batteries that have passed the porosity test, which improves the wettability of the electrodes in the secondary batteries, thereby improving the electrical performance of the secondary batteries and improving the performance of the energy storage system.

[0152] Specifically, after the secondary battery is packaged, it undergoes operations such as cell stacking, tab processing, module packaging, system assembly, and energy storage system integration to form an energy storage system, which can be used in a variety of scenarios, including power storage, grid peak regulation, and renewable energy support.

[0153] On the other hand, the present application provides an electrical device, including: the energy storage system of the above embodiment.

[0154] The electrical equipment of this embodiment includes the energy storage system of the above embodiment, wherein the secondary battery in the energy storage system is a qualified secondary battery that has passed the porosity test, and the secondary battery has high electrical performance, thereby improving the performance of electricity consumption.

[0155] The electrical equipment of this embodiment may be a portable terminal, a pure electric vehicle, a hybrid electric vehicle, an electric ship, a smart home appliance, etc.

[0156] Those skilled in the art will appreciate that the above embodiments are specific embodiments for implementing the present application, and that in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present application.

Claims

1. A method for preparing a secondary battery, characterized in that: include: Providing a pole piece, wherein the pole piece is a positive pole piece or a negative pole piece, and the pole piece is a pole piece after a rolling operation; Obtaining the actual porosity of each local area of ​​the pole piece; Determining whether each of the local areas of the electrode sheet is qualified according to the actual porosity of each of the local areas; If each of the local areas of the electrode sheet is qualified, the electrode sheet is sequentially rolled, blanked, assembled into a battery cell, injected with liquid, and packaged to form a secondary battery; In the case that the local area of ​​the electrode piece is unqualified, performing laser processing on the local area of ​​the electrode piece to form laser pores; repeating the steps of obtaining the actual porosity of each local area of ​​the electrode piece and judging whether each local area of ​​the electrode piece is qualified according to the actual porosity of each local area, until each local area of ​​the electrode piece is qualified; The determining whether the local area of ​​the electrode piece is qualified according to the actual porosity of each local area includes: Calculating the deviation between the actual porosity and the target porosity of the local area, the calculation formula of the deviation δ1 is: δ1=|δ-δ0|, where δ is the actual porosity and δ0 is the target porosity; When the deviation between the actual porosity of the local area and the target porosity is less than or equal to a preset threshold, determining that the local area of ​​the electrode is qualified; When the deviation between the actual porosity of the local area and the target porosity is greater than the preset threshold, the local area of ​​the electrode is determined to be unqualified; the preset threshold is greater than 0 and less than or equal to 10%.

2. The method for preparing a secondary battery according to claim 1, wherein: The obtaining of the actual porosity of each local area of ​​the pole piece includes: acquiring an image of each of the local regions of the pole piece; The area S of each local region of the electrode is obtained according to the image total and the area S of the particle region in each of the local regions of the pole piece solid ; According to the area S of each local area of ​​the pole piece total , the area S of the particle region solid Obtain the actual porosity δ, the calculation formula of the actual porosity δ is: δ=1-S solid / S total .

3. The method for preparing a secondary battery according to claim 2, wherein: The acquiring of an image of each local area of ​​the pole piece comprises: Using an area array CCD image sensor or a linear array CCD image sensor to acquire an image of each of the local areas of the pole piece; The area S of each local area of ​​the electrode is obtained according to the image total and the area S of the particle region in each of the local regions of the pole piece solid ,include: The entire area of ​​the image is obtained as the area S of each local area of ​​the electrode. total , and use the grayscale algorithm to calculate the area S of the particle region in the image solid .

4. The method for preparing a secondary battery according to claim 2 or 3, wherein: The laser aperture is a circular hole; before the laser processing is performed on the local area of ​​the pole piece to form the laser aperture, the method includes: The radius of the circular hole is obtained according to the deviation and the area of ​​the local region of the electrode. The calculation formula of the radius r of the circular hole is: r=sqrt(3×δ1×S total / Pi); Pi is pi; S total is the area of ​​the local region of the pole piece; The laser processing of the local area of ​​the pole piece to form the laser aperture comprises: The laser aperture is formed by laser processing the local area of ​​the pole piece according to the radius r of the circular hole.

5. The method for preparing a secondary battery according to claim 2 or 3, wherein: The laser aperture is a long strip-shaped groove; before the laser processing is performed on the local area of ​​the pole piece to form the laser aperture, the method includes: The size of the long strip groove is obtained according to the deviation and the area of ​​the local area of ​​the electrode; the size of the long strip groove includes the length and width of the long strip groove, and the calculation formula of the length L of the long strip groove is: L=3×δ1×S total / W,S total is the area of ​​the local region of the pole piece, W is the width of the long strip groove, and W is in the range of 0.05 μm to 0.1 μm; The laser processing of the local area of ​​the pole piece to form the laser aperture comprises: The laser aperture is formed by laser processing the local area of ​​the pole piece according to the size of the long strip groove.

6. The method for preparing a secondary battery according to claim 1, wherein: Before the laser processing is performed on the local area of ​​the pole piece to form the laser aperture, the method includes: Obtaining the thickness of the pole piece, and determining the parameters of the laser processing according to the thickness, wherein the parameters include power, pulse width, laser speed, laser temperature, and laser frequency; When the pole piece is a positive pole piece, the power is 10W to 50W, the pulse width is 10ps to 100ns, the laser speed is 500mm / s to 2800mm / s, the laser temperature is 100°C to 300°C, and the laser frequency is 180kHz to 400kHz; when the pole piece is a negative pole piece, the power is 5W to 30W, the pulse width is 10ps to 100ns, the laser speed is 400mm / s to 800mm / s, the laser temperature is 80°C to 200°C, and the laser frequency is 180kHz to 400kHz; The laser processing of the local area of ​​the pole piece to form the laser aperture comprises: Laser processing is performed on the local area of ​​the pole piece according to the parameters of the laser processing to form the laser aperture.

7. A secondary battery, characterized in that: The secondary battery is prepared by the secondary battery preparation method according to any one of claims 1 to 6.

8. An energy storage system, characterized in that: include: A plurality of secondary batteries as claimed in claim 7.

9. An electrical device, characterized in that: include: The energy storage system according to claim 8.

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