Preparation method of secondary battery, secondary battery, energy storage system and electric equipment

Abstract

The invention relates to the technical field of batteries, and discloses a preparation method of a secondary battery, the secondary battery, an energy storage system and electric equipment.The preparation method of the secondary battery comprises the steps that a pole piece is provided, the pole piece is a positive pole piece or a negative pole piece, and the pole piece is a pole piece obtained after rolling operation; obtaining the actual porosity of the pole piece; judging whether the pole piece is qualified or not according to the actual porosity; under the condition that the pole piece is qualified, the pole piece is sequentially subjected to rolling, blanking, cell assembly, liquid injection and packaging to form the secondary battery; under the condition that the pole piece is unqualified, performing laser treatment on the pole piece to form a laser hole; and repeating the step of acquiring the actual porosity of the pole piece and the step of judging whether the pole piece is qualified or not according to the actual porosity until the pole piece is qualified, so that the uniformity of the porosity of the pole piece is improved, the wettability of the pole piece is enhanced, and the electrical property of the secondary battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a preparation method of a secondary battery, a secondary battery, an energy storage system, and an electrical device. Background Art

[0002] In the preparation process of a secondary battery, the preparation of the electrode sheet is one of the key links, and the wettability of the electrode sheet plays an important role in improving the electrical performance of the secondary battery. In the current preparation process of the electrode sheet for a secondary battery, the main steps include electrode sheet feeding, unwinding and running the strip, electrode sheet rolling, thickness detection, winding and blanking, etc.

[0003] However, the current preparation process of the secondary battery still has the problem of poor wettability of the electrode sheet, thereby reducing 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 preparation method of a secondary battery, a secondary battery, an energy storage system, and an electrical device, so as to improve the uniformity of the porosity of the electrode sheet, enhance the wettability of the electrode sheet, and improve the electrical performance of the secondary battery.

[0005] To solve the technical problem of poor electrical performance of the secondary battery caused by poor wettability of the electrode sheet, the embodiments of the present application provide a preparation method of a secondary battery, including: providing an electrode sheet, where the electrode sheet is a positive electrode sheet or a negative electrode sheet, and the electrode sheet is the electrode sheet after a rolling operation; obtaining the actual porosity of the electrode sheet; judging whether the electrode sheet is qualified according to the actual porosity; in the case where the electrode sheet is qualified, winding, blanking, cell assembly, liquid injection, and encapsulation are sequentially performed on the electrode sheet to form a secondary battery; in the case where the electrode sheet is unqualified, laser treatment is performed on the electrode sheet to form laser pores; the steps of obtaining the actual porosity of the electrode sheet and judging whether the electrode sheet is qualified according to the actual porosity are repeatedly performed until the electrode sheet is qualified.

[0006] The embodiments of the present application also provide a secondary battery, which is prepared by the above-mentioned preparation method of the secondary battery.

[0007] The embodiments of the present application also provide an energy storage system, including: a plurality of the above-mentioned secondary batteries.

[0008] The embodiments of the present application also provide an electrical device, including: the above-mentioned energy storage system.

[0009] In some embodiments, determining whether the electrode sheet is qualified according to the actual porosity includes: calculating the deviation between the actual porosity and the target porosity, and the calculation formula for the deviation δ1 is: δ1 = |δ - δ0|, where δ is the actual porosity and δ0 is the target porosity; determining that the electrode sheet is qualified when the deviation is less than or equal to a preset threshold; determining that the electrode sheet is unqualified when the deviation is greater than the preset threshold, and the preset threshold is greater than 0 and less than or equal to 10%.

[0010] In some embodiments, obtaining the actual porosity of the electrode sheet includes: obtaining an image of the electrode sheet; obtaining the area S of the electrode sheet according to the image total and the area S of the particle region in the electrode sheet solid ; according to the area S of the electrode sheet total , the area S of the particle region solid obtain the actual porosity δ, and the calculation formula for the actual porosity δ is: δ = 1 - S solid / S total .

[0011] In some embodiments, obtaining the image of the electrode sheet includes: obtaining the image of the electrode sheet by using a area array CCD image sensor or a linear array CDD image sensor; the image is an image of a local region in the electrode sheet; obtaining the area S of the electrode sheet according to the image total and the area S of the particle region in the electrode sheet solid , including: obtaining the overall area of the image as the area S of the electrode sheet total , and calculating the area S of the particle region in the image by using a gray scale algorithm solid .

[0012] In some embodiments, the laser pore is a round hole; before performing laser treatment on the electrode sheet to form the laser pore, it includes: obtaining the radius of the round hole according to the deviation and the total area of the electrode sheet, and the calculation formula for the radius r of the round hole is: r = sqrt(3 × δ1 × S total / Pi); Pi is the pi; S total is the total area of the electrode sheet; performing laser treatment on the electrode sheet to form the laser pore includes: performing laser treatment on the electrode sheet according to the radius r of the round hole to form the laser pore.

[0013] In some embodiments, the laser pores are strip-shaped grooves; before the laser treatment of the electrode sheet to form the laser pores, it includes: obtaining the dimensions of the strip-shaped grooves according to the deviation and the total area of the electrode sheet; the dimensions of the strip-shaped grooves include the length and width of the strip-shaped grooves, and the calculation formula for the length L of the strip-shaped grooves is: L = 3×δ1×S total / W, S total is the area of the electrode sheet, W is the width of the strip-shaped groove, and W is in the range of 0.05μm to 0.1μm; the laser treatment of the electrode sheet to form the laser pores includes: performing laser treatment on the electrode sheet according to the dimensions of the strip-shaped grooves to form the laser pores.

[0014] In some embodiments, before the laser treatment of the electrode sheet to form the laser pores, it includes: obtaining the thickness of the electrode sheet, and determining the parameters of the laser treatment according to the thickness, and the parameters include power, pulse width, laser speed, laser temperature, laser frequency; when the electrode sheet is a positive electrode sheet, 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 electrode sheet is a negative electrode sheet, 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 treatment of the electrode sheet to form the laser pores includes: performing laser treatment on the electrode sheet according to the parameters of the laser treatment to form the laser pores.

[0015] The technical solutions provided by the embodiments of the present application have at least the following advantages: In the embodiments of the present application, after the rolling operation, the actual porosity of the electrode sheet is detected, and it is judged whether the electrode sheet is qualified according to the actual porosity of the electrode sheet. In the case of determining that the electrode sheet is qualified, subsequent winding, blanking, battery cell assembly, liquid injection, and encapsulation operations are performed on the electrode sheet to form a secondary battery. In the case of determining that the electrode sheet is unqualified, laser treatment is performed on the electrode sheet 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. Thus, the defects of insufficient porosity in the electrode sheet can be effectively identified and compensated, the uniformity of the porosity of the electrode sheet is improved, the wettability of the electrode sheet is enhanced, thereby improving the ion transport performance of the electrode sheet and the electrical performance of the secondary battery. Moreover, the process cost of the porosity detection and adjustment method added in the embodiments of the present application is relatively low and the safety is relatively high, while improving the wettability of the electrode sheet, the process cost and safety of the preparation of the secondary battery are also taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings represent similar elements. Unless otherwise stated, the drawings in the figures do not constitute a scale limitation.

[0017] Figure 1 is a schematic flow chart of a method for preparing a secondary battery according to an embodiment of the present application; Figure 2 is a process flow chart of the preparation of a secondary battery in the related art; Figure 3 is a process flow chart of the preparation of a secondary battery according to an embodiment of the present application; Figure 4 is a schematic flow chart of a method for preparing a secondary battery according to another embodiment of the present application; Figure 5 is a schematic flow chart of a method for preparing a secondary battery according to still another embodiment of the present application; Figure 6 is a process flow chart of a method for preparing a secondary battery according to yet another embodiment of the present application; Figure 7 is a schematic flow chart of a method for preparing a secondary battery according to another embodiment of the present application; Figure 8 is a schematic flow chart of a method for preparing a secondary battery according to still another embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] As can be seen from the background art, in the current preparation process of secondary batteries, there is still a problem of poor wettability of the electrode sheets, which reduces the electrical performance of the secondary batteries.

[0019] Through analysis and research, it is found that in the process of preparing secondary batteries, when both the areal density and the rolling thickness fluctuate, there must be a problem of uneven pore structure in local areas of the electrode sheets. The uneven pore structure will lead to problems such as local electrolyte dry-up and local failure driving the overall failure of the battery cell to drop at the end of the cycle, resulting in poor wettability of the electrode sheets and thus reducing the electrical performance of the secondary batteries.

[0020] In order to solve the problem of poor wettability of the electrode sheet in secondary batteries, in related technologies, the wettability of the electrode sheet is usually improved by optimizing the liquid injection process and the electrolyte formula. However, this method cannot improve the local wettability of the electrode sheet, resulting in poor wettability of the electrode sheet. At the same time, it will also increase the process cost in the preparation process of secondary batteries and reduce the safety in the preparation process of secondary batteries. To solve the above technical problems, an embodiment of the present application provides a method for preparing a secondary battery, including: providing an electrode sheet, the electrode sheet being a positive electrode sheet or a negative electrode sheet, and the electrode sheet being an electrode sheet after a rolling operation; obtaining the actual porosity of the electrode sheet; judging whether the electrode sheet is qualified according to the actual porosity; in the case where the electrode sheet is qualified, successively winding, cutting, assembling the battery core, injecting liquid, and packaging the electrode sheet to form a secondary battery; in the case where the electrode sheet is unqualified, performing laser treatment on the electrode sheet to form laser pores; repeating the steps of obtaining the actual porosity of the electrode sheet and judging whether the electrode sheet is qualified according to the actual porosity until the electrode sheet is qualified.

[0021] In the embodiment of the present application, after the rolling operation, the actual porosity of the electrode sheet is detected, and it is judged whether the electrode sheet is qualified according to the actual porosity of the electrode sheet. In the case where the electrode sheet is judged to be qualified, subsequent winding, cutting, battery core assembling, liquid injection, and packaging operations are performed on the electrode sheet to form a secondary battery. In the case where the electrode sheet is judged to be unqualified, laser treatment is performed on the electrode sheet to form laser pores to adjust the porosity of the electrode sheet, and the actual porosity of the electrode sheet is detected again until the electrode sheet is qualified. Thereby, the defect of insufficient porosity in the electrode sheet can be effectively identified and compensated, the uniformity of the porosity of the electrode sheet is improved, the wettability of the electrode sheet is enhanced, thereby improving the ion transport performance of the electrode sheet and the electrical performance of the secondary battery. Moreover, the process cost of the porosity detection and adjustment method added in the embodiment of the present application is relatively low and the safety is relatively high, taking into account the process cost and safety in the preparation of secondary batteries while improving the wettability of the electrode sheet.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present application, many technical details are proposed for 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 required to be protected by the present application can be implemented. The following division of each embodiment is for convenience of description and should not constitute any limitation to the specific implementation manner of the present application. Each embodiment can be combined and cross-referenced with each other on the premise of no contradiction.

[0023] An embodiment of the present application relates to a method for preparing a secondary battery. The schematic flow chart of the specific method for preparing the secondary battery is as Figure 1 shown. The method for preparing the secondary battery includes the following steps: Step 101: Provide a pole piece.

[0024] Specifically, the pole piece in this embodiment is a positive pole piece or a negative pole piece, and the pole piece is the pole piece after the rolling operation.

[0025] In the preparation process of the secondary battery, the preparation of the pole piece is one of the key links. As Figure 2 shown, it is a process flow chart of the preparation of the secondary battery in the related art. The preparation process of the pole piece in the related art includes pole piece loading, unwinding and feeding, pole piece rolling, thickness detection, and winding and blanking. Pole piece loading is to place the prepared pole piece or pole coil on the production line. The pole coil needs to be installed on the unwinding device to ensure that the pole piece can be smoothly unwound. Unwinding and feeding is to unwind the pole coil through the unwinding device and transport the pole piece to the subsequent process through the conveyor belt or roller system. During the unwinding process, the tension of the pole piece needs to be controlled to prevent the pole piece from deforming or breaking. Pole piece rolling is to compact the pole piece through one or more pairs of roller presses to compact the pole piece coating and prevent peeling during electrolyte immersion and battery use, and improve the density and mechanical strength of the pole piece. Thickness detection is carried out after the pole piece rolling. Thickness detection is to detect the thickness of the pole piece to ensure that the thickness of the pole piece meets the process requirements. In this embodiment, while detecting the thickness of the pole piece, the porosity of the pole piece is synchronously detected, that is, the image sensor is synchronously used to obtain the pole piece to improve the preparation efficiency of the secondary battery. Pole piece winding is to continuously process the coil material and use the winding machine to gradually wind the coil material into a large coil, so as to store and transport the coil material of the lithium battery pole piece in an efficient and low-loss manner. Pole coil blanking In fully automated production, the automatic guided vehicle will automatically receive the blanking shaft of the winding machine and transport the completed pole coil to the designated position.

[0026] The pole piece provided in this embodiment is at least the pole piece after the rolling operation. In order to further improve the detection efficiency of the pole piece and avoid subsequent porosity detection of the pole piece with unqualified thickness, which results in a reduction in the detection efficiency of the pole piece, the pole piece provided in this embodiment can also be the pole piece after the thickness detection is qualified, thereby improving the detection efficiency of the pole piece and the preparation efficiency of the secondary battery. As Figure 3 shown, it is a process flow chart of the preparation of the secondary battery in this embodiment. In this embodiment, porosity detection is added after the pole piece rolling and thickness detection. If it is qualified, subsequent winding and blanking operations are carried out. If it is unqualified, porosity adjustment is carried out, and subsequent winding and blanking operations are carried out after the porosity of the pole piece is qualified.

[0027] Step 102: Obtain the actual porosity of the pole piece.

[0028] The actual porosity of the electrode sheet in this embodiment refers to the actual porosity of a local area in the electrode sheet. Since the entire surface of the electrode sheet of the secondary battery includes multiple local areas, in practical applications, the porosity of each local area is detected separately, so as to adjust the porosity of the local area with unqualified porosity and improve the uniformity of the porosity of the electrode sheet. Since fluctuations exist in both the areal density and the rolling thickness of the electrode sheet, it will cause the problem of non-uniform porosity in each local area of the electrode sheet, that is, the porosity of some areas is normal while the porosity of some areas is small, resulting in the problems of local electrolyte dry-out and overall failure of the battery cell driven by local failure at the end of the cycle of the secondary battery. Therefore, in this embodiment, for the local area of the electrode sheet, the corresponding actual porosity is detected, so as to detect the area with abnormal porosity of the electrode sheet for subsequent porosity adjustment, improve the uniformity of the porosity of the electrode sheet, improve the wettability of the electrode sheet, and improve the performance of the prepared secondary battery.

[0029] Step 103: Judge whether the electrode sheet is qualified according to the actual porosity.

[0030] After obtaining the actual porosity of the local area in the electrode sheet in this embodiment, it is judged whether the electrode sheet is qualified according to the actual porosity. Among them, when the actual porosity of the electrode sheet meets the preset conditions, it is determined that the electrode sheet is unqualified; when the actual porosity of the electrode sheet meets the preset conditions, it is determined that the electrode sheet is qualified. Among them, the preset condition is that the deviation between the actual void ratio and the target porosity is less than or equal to the preset threshold.

[0031] Specifically, when the electrode sheet includes multiple local areas, the porosity of each local area in the electrode sheet is detected separately. During the process of detecting the porosity of one of the local areas, when the actual porosity of the local area of the electrode sheet meets the preset conditions, it is judged that the local area of the electrode sheet is qualified; when the actual porosity of the local area of the electrode sheet does not meet the preset conditions, it is determined that the local area of the electrode sheet is unqualified. Then, the porosity of the next local area of the electrode sheet is detected, and this process is cycled in turn until the porosity of multiple local areas of the electrode sheet has been detected. And during the process of detecting the porosity of each local area, as long as the actual porosity corresponding to one local area in the electrode sheet does not meet the preset conditions, it will cause the problem of non-uniform porosity of the electrode sheet and affect the wettability of the electrode sheet. Therefore, it is necessary to adjust the actual porosity of the local area that does not meet the preset conditions, so as to increase the actual porosity of this local area, make the porosity of each local area in the electrode sheet uniform, and improve the wettability of the electrode sheet.

[0032] Specifically, in this embodiment, different treatments are carried out respectively in the case where a local area of the electrode sheet is qualified and a local area of the electrode sheet is unqualified. In the case where a local area of the electrode sheet is qualified, step 104 is entered, that is, the electrode sheet is wound, cut, assembled into an electric core, injected with liquid, and encapsulated in sequence to form a secondary battery. In the case where a local area of the electrode sheet is unqualified, step 105 is entered, that is, the electrode sheet is subjected to laser treatment to form laser pores, that is, the local area of the electrode sheet is subjected to laser treatment to form laser pores, so as to increase the porosity of the local area, improve the uniformity of the porosity of the electrode sheet, and improve the wettability of the electrode sheet.

[0033] Specifically, in the case where the electrode sheet includes multiple local areas, the porosity of each local area in the electrode sheet is detected respectively. If the porosity of each local area meets the preset conditions, that is, each local area is qualified, the subsequent steps of winding, cutting, assembling the electric core, injecting liquid, and encapsulating the electrode sheet in sequence to form a secondary battery are entered. If the porosity of any local area does not meet the preset conditions, that is, any local area is unqualified, laser treatment is carried out on this local area to form laser pores, so as to increase the porosity of the local area, improve the uniformity of the porosity of the electrode sheet, and improve the wettability of the electrode sheet.

[0034] Step 104: The electrode sheet is wound, cut, assembled into an electric core, injected with liquid, and encapsulated in sequence to form a secondary battery.

[0035] Specifically, in this embodiment, in the case where the electrode sheet is qualified, subsequent winding and cutting operations are carried out on the electrode sheet. After that, the electric core is assembled, injected with liquid, and encapsulated to form a secondary battery.

[0036] The electric core assembly includes laminating or winding, inserting a center pin, and encapsulating the electric core; laminating or winding is to alternately stack or wind the positive electrode sheet, separator, and negative electrode sheet into an electric core according to the design of the secondary battery. The separator is used to isolate the positive and negative electrodes to prevent short circuit; inserting a center pin is to insert a center pin in a wound electric core to fix the electric core structure; encapsulating the electric core is to put the assembled electric core into the battery case and place insulators on both sides of the electric core. Injecting liquid is to inject the electrolyte into the battery case to make the electrolyte fully infiltrate the electric core. The electrolyte usually consists of electrolyte salts, solvents, and additives. Encapsulation is to seal the battery case and the battery cover by welding or other means to ensure the sealing performance.

[0037] Step 105: The electrode sheet is subjected to laser treatment to form laser pores.

[0038] In this embodiment, the electrode sheet is subjected to laser treatment to form laser pores, that is, the local area of the electrode sheet is subjected to laser treatment to form laser pores. This local area is the local area where the actual porosity does not meet the preset conditions. Therefore, laser treatment needs to be carried out on this local area to increase the porosity of this local area, so as to improve the uniformity of the overall porosity of the electrode sheet and improve the wettability of the electrode sheet.

[0039] The laser used in this embodiment can be a nanosecond laser, a picosecond laser, a femtosecond laser, etc. Laser treatment is performed perpendicular to the electrode plate to form laser pores, thereby increasing the porosity of the local area.

[0040] After laser treatment is performed on the electrode plate to form laser pores in this embodiment, steps 102 of re-acquiring the actual porosity of the local area in the electrode plate and step 103 of determining whether the electrode plate is qualified according to the actual porosity of the local area are repeated until the electrode plate is qualified, that is, until the local area of the electrode plate is qualified.

[0041] Specifically, the electrode plate is strip-shaped. For example, the length of the electrode plate is 800 mm and the width is 50 mm. The local area in this embodiment is a partial area of the electrode plate. For example, the electrode plate 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. Or, the electrode plate is bisected 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.

[0042] In this embodiment, by detecting and adjusting the porosity of each local area, when the porosity of each local area does not meet the requirements, laser treatment is performed on the local area to increase the porosity of the local area, improve the uniformity of the porosity of multiple local areas in the electrode plate, and thereby improve the wettability of the electrode plate.

[0043] In practical applications, if the porosity is very uneven, that is, the porosity of some local areas is large, the porosity of some local areas is small, and the deviation between the actual porosity of the local area with a large porosity and the target porosity exceeds the preset threshold, and the porosity of this area cannot be reduced. Therefore, such an electrode plate cannot form a qualified product through laser treatment and can be directly screened out for scrap treatment.

[0044] In this embodiment, after the pole piece is subjected to a rolling operation, the actual porosity of the pole piece is detected, and it is judged whether the pole piece is qualified according to the actual porosity of the pole piece. When it is determined that the pole piece is qualified, subsequent winding, blanking, battery cell assembly, liquid injection, and encapsulation operations are performed on the pole piece to form a secondary battery. When the actual porosity of any area of the pole piece does not meet the preset conditions, that is, when it is determined that the pole piece is unqualified, laser treatment is performed on the pole piece to form laser pores to adjust the porosity of the pole piece, and the actual porosity of the pole piece is detected again until the pole piece is qualified. Thus, the defect of insufficient porosity in the pole piece can be effectively identified and remedied, the uniformity of the porosity of the pole piece is improved, the wettability of the pole piece is enhanced, thereby improving the ion transport performance of the pole piece and the electrical performance of the secondary battery. Moreover, the process cost of the porosity detection and adjustment method added in the embodiment of the present application is relatively low and the safety is relatively high, taking into account the process cost and safety of the preparation of the secondary battery while improving the wettability of the pole piece.

[0045] Figure 2 The related technology shown is Comparative Example 1 of this embodiment. The preparation method of the secondary battery in this embodiment, that is, Example 1, has a significant improvement in performance compared with the process of Comparative Example 1. Referring to the technical effect comparison table shown in Table 1, the soaking time of the battery cell in the secondary battery in Comparative Example 1 is 24 h, and the 0.5P cycle life-capacity retention rate of the secondary battery is 95.7% @ 500 cycles. 95.7% @ 500 cycles 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 occasional brown spots appear on the full charge interface of the secondary battery. While in this embodiment, that is, Example 1, the soaking time of the battery cell is 16 h, the soaking time of the battery cell is shortened by 8 h, and the 0.5P cycle life-capacity retention rate of the secondary battery is 96.5% @ 500 cycles. 96.5% @ 500 cycles 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 there are no brown spots on the full charge interface of the secondary battery.

[0046] It can be seen that compared with Comparative Example 1, in Example 1, the soaking time of the battery cell, the 0.5P cycle life-capacity retention rate, and the full charge interface have all been improved, thereby improving the wettability of the pole piece and the performance of the battery cell.

[0047] Table 1

[0048] Another embodiment of the present application relates to a method for preparing a secondary battery. In this embodiment, the preset condition is further defined as that the deviation between the actual porosity and the target porosity is less than or equal to a preset threshold, and the above step 103 is further refined, that is, it is judged whether the pole piece is qualified according to the actual porosity. The flow chart of the preparation method of the secondary battery in this embodiment is as Figure 4As shown in the figure, the method for preparing a secondary battery according to this embodiment includes the following steps: Step 201: Provide a pole piece.

[0049] Step 202: Obtain the actual porosity of the pole piece.

[0050] Step 203: Calculate the deviation between the actual porosity and the target porosity.

[0051] In this embodiment, after obtaining the actual porosity of a local area of the pole piece, the deviation between the actual porosity of this local area and the target porosity is calculated. In some embodiments, the calculation formula for the deviation δ1 is: 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%.

[0052] Step 204: Determine whether the pole piece is qualified according to the deviation.

[0053] In this embodiment, it is determined whether the pole piece is qualified through the deviation corresponding to the local area. That is, as long as the deviation corresponding to a local area in the pole piece is greater than the preset threshold, it will cause the problem of uneven porosity of the pole piece and affect the wettability of the pole piece. 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 this area, make the porosity of each local area in the pole piece uniform, and improve the wettability of the pole piece.

[0054] In some embodiments, the preset threshold is greater than 0 and less than or equal to 10%, such as 2%, 4%, 6%, 8%, 10%. Specifically, the preset threshold can be in the range of 0 to 6%, or can be 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 pole piece, if the actual porosity of a local area of the pole piece is 35%, the deviation between the actual porosity of this local area of 35% and the target porosity of 40% is 5%, which is less than the preset threshold of 10%. At this time, it is determined that this local area of the pole piece is qualified; if the actual porosity of a local area of the pole piece is 25%, the deviation between the actual porosity of this area and the target porosity of 40% is 15%, which is greater than the preset threshold of 10%. At this time, it is determined that this local area of the pole piece is unqualified. After that, laser treatment is performed on this local area to form laser pores, so as to increase the actual porosity of this local area, improve the uniformity of the porosity of the pole piece, and improve the wettability of the pole piece.

[0055] Specifically, when the electrode sheet is qualified, it enters step 205, where the electrode sheet is successively wound up, cut, assembled into an electrode core, injected with electrolyte, and encapsulated to form a secondary battery. When the electrode sheet is unqualified, it enters step 206, where the electrode sheet is laser-treated to form laser pores, thereby increasing the actual porosity of this local area of the electrode sheet, improving the uniformity of the porosity of the electrode sheet, and enhancing the wettability of the electrode sheet.

[0056] Step 205: The electrode sheet is successively wound up, cut, assembled into an electrode core, injected with electrolyte, and encapsulated to form a secondary battery.

[0057] Step 206: The electrode sheet is laser-treated to form laser pores.

[0058] After the electrode sheet is laser-treated to form laser pores in this embodiment, steps 202 of obtaining the actual porosity of the electrode sheet, step 203 of calculating the deviation between the actual porosity and the target porosity, and step 204 of determining whether the electrode sheet is qualified according to the deviation are repeatedly carried out until the electrode sheet is qualified.

[0059] Steps 201, 202, 205, and 206 in this embodiment are substantially the same as steps 101, 102, 104, and 105 in the previous embodiment. To avoid repetition, they will not be elaborated here.

[0060] In this embodiment, by calculating the deviation between the actual porosity and the target porosity of the electrode sheet and determining whether the electrode sheet is qualified according to the deviation, when the electrode sheet is qualified, the electrode sheet is successively wound up, cut, assembled into an electrode core, injected with electrolyte, and encapsulated to form a secondary battery. When the electrode sheet is unqualified, the electrode sheet is laser-treated to form laser pores, improving the uniformity of the porosity of the electrode sheet and enhancing the wettability of the electrode sheet.

[0061] Another embodiment of the present application relates to a method for preparing a secondary battery. In this embodiment, the manner of obtaining the actual porosity of the electrode sheet is further defined. The flow schematic diagram of the method for preparing the secondary battery in this embodiment is as Figure 5 shown. The method for preparing the secondary battery in this embodiment includes the following steps: Step 301: Provide an electrode sheet.

[0062] Step 302: Obtain an image of the electrode sheet.

[0063] Step 303: Obtain the area S of the electrode sheet according to the image total and the area S of the particle region in the electrode sheet solid .

[0064] Step 304: Obtain the actual porosity δ according to the area S of the electrode sheet total and the area S of the particle region solid .

[0065] Specifically, the actual porosity of a local area in the electrode sheet is obtained in this embodiment. To obtain the actual porosity of the local area in the electrode sheet, an image corresponding to the electrode sheet is first obtained, and this image is an image of the local area in the electrode sheet. After that, the area S of the local area of the electrode sheet is obtained according to the image. total And the area S of the particle area in the local area of the electrode sheet solid , according to the area S of the local area of the electrode sheet total , the area S of the particle area solid The actual porosity δ corresponding to the local area of the electrode sheet is obtained. The calculation formula of the actual porosity δ is: δ = 1 - S solid / S total .

[0066] In some embodiments, step 302, that is, obtaining the image of the electrode sheet, is implemented in the following manner: A planar array CCD (Charge-Coupled Device) image sensor or a linear array CDD image sensor is used to obtain the image corresponding to the local area in the electrode sheet.

[0067] The pixels of the planar array CCD image sensor are arranged in a two-dimensional matrix form and can capture the images of each local area in the electrode sheet simultaneously. The planar array CCD image sensor in this embodiment can be a frame transfer planar array CCD or an interline transfer planar array CCD. Among them, the working modes of the two are different. After exposure, the frame transfer planar array CCD transfers the charges accumulated in the photosensitive units to the storage units and then reads them, while after exposure, the interline transfer planar array CCD transfers the charges from the photosensitive units to the adjacent storage units, and at the same time, the photosensitive units in the next row are ready for exposure.

[0068] The pixels of the linear array CDD image sensor are arranged in a straight line and can only capture one row of pixels of the image each time. The linear array CCD image sensor captures the image by means of progressive scanning and has a relatively fast image acquisition speed. The linear array CCD image sensor in this embodiment can be divided into a single-channel linear array CCD or a dual-channel linear array CCD. Among them, the dual-channel linear array CCD has a higher transfer efficiency, which is more conducive to improving the image acquisition speed and the porosity detection efficiency.

[0069] Correspondingly, step 303 in this embodiment, that is, obtaining the area of the electrode sheet and the area of the particle area in the electrode sheet according to the image, is implemented in the following manner: The overall area of the image is obtained as the area S of the local area of the electrode sheet total , and the area S of the particle area in this local area is calculated by using the gray-scale algorithm solid . That is, for the image of each local area in the electrode sheet, the area S of the image corresponding to the local area is obtainedtotal and the area S of the particle region in the image solid , according to the calculation formula of the actual porosity δ, δ = 1 - S solid / S total the actual porosity δ of this local area is calculated and obtained.

[0070] Step 305: Judge whether the electrode sheet is qualified according to the actual porosity.

[0071] Specifically, after obtaining the actual porosity of the local area of the electrode sheet in this embodiment, the deviation between the actual porosity and the target porosity is calculated, and it is judged whether the electrode sheet is qualified through the deviation. The actual porosity of the local area with the deviation greater than the preset threshold is adjusted, so as to improve the actual porosity of the local area of the electrode sheet, improve the uniformity of the porosity of the electrode sheet, and improve the wettability of the electrode sheet.

[0072] Specifically, when the electrode sheet is qualified, go to Step 306, that is, wind up, cut, assemble the battery core, inject electrolyte, and package the electrode sheet in sequence to form a secondary battery. When the electrode sheet is unqualified, go to Step 307, that is, perform laser treatment on the electrode sheet to form laser pores, so as to improve the uniformity of the porosity of the electrode sheet and improve the wettability of the electrode sheet.

[0073] Step 306: Wind up, cut, assemble the battery core, inject electrolyte, and package the electrode sheet in sequence to form a secondary battery.

[0074] Step 307: Perform laser treatment on the electrode sheet to form laser pores.

[0075] After performing laser treatment on the electrode sheet to form laser pores in this embodiment, re-enter Step 302, that is, the step of obtaining the image of the electrode sheet, Step 303, that is, the step of obtaining the area S of the electrode sheet total and the area S of the particle region in the electrode sheet solid of Step 304, that is, according to the area S of the electrode sheet total , the area S of the particle region solid to obtain the step of the actual porosity δ, and Step 305, that is, the step of judging whether the electrode sheet is qualified according to the actual porosity, until the electrode sheet is qualified.

[0076] Steps 301, 305, 306, and 307 in this embodiment are substantially the same as Steps 101, 103, 104, and 105 in the previous embodiment. To avoid repetition, they will not be elaborated here.

[0077] Another embodiment of the present application relates to a method for preparing a secondary battery. In this embodiment, the laser pores are further defined as round holes. Before the laser treatment of the electrode sheet to form laser pores, it includes: obtaining the radius of the round hole according to the deviation and the area of the electrode sheet. The laser treatment of the electrode sheet to form laser pores includes: performing laser treatment on the electrode sheet according to the radius r of the round hole to form laser pores.

[0078] The schematic flow chart of the method for preparing the secondary battery in this embodiment is as Figure 6 shown. The method for preparing the secondary battery in this embodiment includes the following steps: Step 401, provide an electrode sheet.

[0079] Step 402, obtain an image of the electrode sheet.

[0080] Step 403, obtain the area S of the electrode sheet according to the image total and the area S of the particle region in the electrode sheet solid .

[0081] Step 404, obtain the actual porosity δ according to the area S of the electrode sheet total , the area S of the particle region solid .

[0082] Step 405, calculate the deviation between the actual porosity and the target porosity.

[0083] Step 406, judge whether the electrode sheet is qualified according to the deviation.

[0084] Specifically, when the electrode sheet is qualified, go to Step 407; when the electrode sheet is unqualified, go to Step 408.

[0085] Step 407, wind up, cut, assemble the battery core, inject electrolyte, and package the electrode sheet in sequence to form a secondary battery.

[0086] Step 408, obtain the radius of the round hole according to the deviation and the area of the electrode sheet.

[0087] Step 409, perform laser treatment on the electrode sheet according to the radius of the round hole to form laser pores.

[0088] After determining that the electrode sheet is unqualified in this embodiment, it is necessary to perform laser treatment on a local area of the electrode sheet to form laser pores. The purpose of the 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. And the actual porosities of different local areas are different. If the same laser treatment parameters are used, for the local area with a smaller actual porosity, the porosity cannot be effectively increased, reducing the efficiency and accuracy of porosity adjustment.

[0089] In order to further improve the efficiency and accuracy of porosity adjustment in this embodiment, the laser pores formed by laser treatment are set as round holes. The radius of the round hole is obtained according to the deviation corresponding to the local area and the total area of the local area. The calculation formula for the radius r of the round hole is: r = sqrt(3 × δ1 × S total / Pi), where δ1 is the deviation between the actual porosity and the target porosity, Pi is the pi, and S total is the area of the electrode sheet, that is, the area of the local area in the electrode sheet; then the local area in the electrode sheet is laser-treated according to the radius r of the round hole to form laser pores, that is, round holes, so as to set 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 porosity adjustment.

[0090] After the local area in the electrode sheet is laser-treated to form laser pores in this embodiment, it re-enters step 402, that is, the step of obtaining the image of the electrode sheet, step 403, that is, the step of obtaining the area S total of the electrode sheet and the area S solid of the particle area in the electrode sheet, step 404, that is, the step of obtaining the actual porosity δ according to the area S total of the electrode sheet, the area S solid of the particle area, step 405, that is, the step of calculating the deviation between the actual porosity and the target porosity, step 406, that is, the step of judging whether the electrode sheet is qualified according to the deviation, until the electrode sheet is qualified.

[0091] Steps 401 to 404 in this embodiment are substantially the same as steps 301 to 304 in the previous embodiment, and steps 405 to 407 are substantially the same as steps 203 to 205 in the above embodiment. To avoid repetition, they will not be elaborated here.

[0092] In this embodiment, by setting the laser pores as round holes, obtaining the radius of the round hole according to the deviation corresponding to the local area of the electrode sheet and the area of the local area, and laser-treating the local area in the electrode sheet according to the radius of the round hole to form laser pores, it realizes setting 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 porosity adjustment.

[0093] The optimized liquid injection process and electrolyte formula of the related technology are Comparative Example 2 of this embodiment. Referring to the technical effect comparison table shown in Table 2, in Comparative Example 2, the soaking time of the battery cell of the secondary battery is 20 h, and the 0.5C cycle life-capacity retention rate of the secondary battery is 95.8% @ 500 cycles. 95.8% @ 500 cycles 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 without brown spots; while in this embodiment, that is, in Example 2, the soaking time of the battery cell of the secondary battery is 16 h, and the 0.5C cycle life-capacity retention rate of the secondary battery is 96.5% @ 500 cycles. 96.5% @ 500 cycles 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 without brown spots.

[0094] It can be seen that compared with Comparative Example 2, in Example 2, there is no obvious change in the fully charged interface, but the soaking time of the battery cell is significantly reduced, and the 0.5C cycle life-capacity retention rate is also improved, so that the wettability of the electrode sheet is improved, and the performance of the battery cell is improved.

[0095] Table 2

[0096] Another embodiment of the present application relates to a method for preparing a secondary battery. In this embodiment, it is further defined that the laser pores are long strip-shaped grooves; before the electrode sheet is laser-treated to form laser pores, it includes: obtaining the size of the long strip-shaped grooves according to the deviation and the area of the electrode sheet; laser-treating the electrode sheet to form laser pores, including: laser-treating the electrode sheet according to the size of the long strip-shaped grooves to form laser pores.

[0097] The flow schematic diagram of the method for preparing the secondary battery of this embodiment is as Figure 7 shown. The method for preparing the secondary battery of this embodiment includes the following steps: Step 501, provide an electrode sheet.

[0098] Step 502, obtain an image of the electrode sheet.

[0099] Step 503, obtain the area S of the electrode sheet according to the image total and the area S of the particle region in the electrode sheet solid .

[0100] Step 504, obtain the actual porosity δ according to the area S of the electrode sheet total , the area S of the particle region solid .

[0101] Step 505, calculate the deviation between the actual porosity and the target porosity.

[0102] Step 506: Determine whether the electrode sheet is qualified according to the deviation.

[0103] If the electrode sheet is qualified, proceed to Step 507; if the electrode sheet is unqualified, proceed to Step 508.

[0104] Step 507: Wind up, cut, assemble the battery core, inject electrolyte, and package the electrode sheet in sequence to form a secondary battery.

[0105] Step 508: Obtain the size of the long strip-shaped groove according to the deviation and the area of the electrode sheet.

[0106] Step 509: Perform laser treatment on the electrode sheet according to the size of the long strip-shaped groove to form laser pores.

[0107] In this embodiment, after determining that the electrode sheet is unqualified, it is necessary to perform laser treatment on a local area of the electrode sheet to form laser pores. 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 the preset threshold. And the actual porosities of different layout areas are different. If the same laser treatment parameters are used, for the local area with a relatively small actual porosity, the porosity cannot be effectively increased, reducing the efficiency and accuracy of porosity adjustment.

[0108] In this embodiment, in order to further improve the efficiency and accuracy of porosity adjustment, the laser pores formed by laser treatment are set as long strip-shaped grooves, and the size of the long strip-shaped groove is obtained according to the deviation corresponding to the local area and the total area of the local area.

[0109] The size of the long strip-shaped groove includes the length and width of the long strip-shaped groove. The calculation formula for the length L of the long strip-shaped groove is: L = 3×δ1×S total / W, where δ1 is the deviation between the actual porosity and the target porosity, S total is the area of the electrode sheet, that is, the area of the local area in the electrode sheet, and W is the width of the long strip-shaped groove. W is a fixed value within the range of 0.05 μm to 0.1 μm, such as 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm.

[0110] After that, perform laser treatment on the local area of the electrode sheet according to the size of the long strip-shaped groove to form laser pores, that is, long strip-shaped grooves, so as to set 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 porosity adjustment.

[0111] After the laser treatment is performed on the electrode sheet to form laser pores in this embodiment, the process returns to step 502, i.e., the step of obtaining an image of the electrode sheet, and step 503, i.e., the step of obtaining the area S of the electrode sheet according to the image total and the area S of the particle region in the electrode sheet solid of the step, step 504, i.e., according to the total area S of the electrode sheet total and the area S of the particle region solid to obtain the actual porosity δ, step 505, i.e., the step of calculating the deviation between the actual porosity and the target porosity, step 506, i.e., the step of determining whether the electrode sheet is qualified according to the deviation, until the electrode sheet is qualified.

[0112] Steps 501 to 507 of this embodiment are substantially the same as steps 401 to 407 of the previous embodiment. To avoid repetition, they will not be elaborated here.

[0113] In this embodiment, by setting the laser pores as long strip-shaped grooves, the size of the long strip-shaped grooves is obtained according to the deviation corresponding to the local area of the electrode sheet and the total area of the local area, and the local area of the electrode sheet is laser-treated according to the size of the long strip-shaped grooves to form laser pores, which realizes setting 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 porosity adjustment.

[0114] The optimized liquid injection process and electrolyte formula of the related technology are Comparative Example 2 of this embodiment. Referring to the technical effect comparison table shown in Table 3, in Comparative Example 2, the infiltration time of the secondary battery cell is 20h, 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 without brown spots; while for the secondary battery of this embodiment, i.e., Embodiment 3, the infiltration time of the secondary battery cell is 16h, 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 without brown spots.

[0115] It can be seen that compared with Comparative Example 2, in Embodiment 3, the fully charged interface has no obvious change, but the infiltration time of the cell is significantly reduced, and the 0.5P cycle life-capacity retention rate is improved, which improves the wettability of the electrode sheet and the performance of the cell.

[0116] Table 3

[0117] Another embodiment of the present application relates to a method for manufacturing a secondary battery. In this embodiment, before forming laser pores on the electrode sheet by laser treatment, the thickness of the electrode sheet is obtained, and the laser treatment parameters are determined according to the thickness. The process schematic diagram of the method for manufacturing the secondary battery in this embodiment is as shown in Figure 8 shown. The method for manufacturing the secondary battery in this embodiment includes the following steps: Step 601: Provide an electrode sheet.

[0118] Step 602: Obtain the actual porosity of the electrode sheet.

[0119] Step 603: Judge whether the electrode sheet is qualified according to the actual porosity.

[0120] Step 604: Wind up, cut, assemble the battery core, inject electrolyte, and package the electrode sheet in sequence to form a secondary battery.

[0121] Step 605: Obtain the thickness of the electrode sheet, and determine the laser treatment parameters according to the thickness.

[0122] In this embodiment, the laser treatment parameters include power, pulse width, laser speed, laser temperature, and laser frequency.

[0123] Among them, when the electrode sheet is a positive electrode sheet, 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, 1000mm / 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.

[0124] When the electrode sheet is a negative electrode sheet, the power is from 5W to 30W, for example, 5W, 15W, 20W, 25W, 30W; the pulse width is from 10ps to 100ns, for example, 10ps, 20ps, 30ps, 40ps, 50ps, 60ps, 70ps, 80ps, 90ps, 100ps; the laser speed is from 400mm / s to 800mm / s, for example, 400mm / s, 500mm / s, 600mm / s, 700mm / s, 800mm / s; the laser temperature is from 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 from 180kHz to 400kHz, for example, 180kHz, 200kHz, 250kHz, 300kHz, 350kHz, 400kHz.

[0125] The electrode sheet thickness obtained in this embodiment can directly obtain the electrode sheet thickness recorded during the electrode sheet thickness detection, thereby improving the efficiency of laser processing and the efficiency of porosity adjustment.

[0126] Step 606, perform laser processing on the electrode sheet according to the laser processing parameters to form laser pores.

[0127] For electrode sheets with different thicknesses, if the same laser processing parameters are used, there will be a risk of reduced laser processing efficiency and the porosity cannot be effectively adjusted. Therefore, in this embodiment, the laser processing parameters, including power, pulse width, laser speed, and laser temperature, are determined according to the thickness of the electrode sheet, and laser processing is performed on the electrode sheet according to the laser processing parameters to form laser pores, thereby improving the laser processing efficiency and the accuracy of porosity adjustment.

[0128] After forming laser pores by performing laser processing on the electrode sheet in this embodiment, it re-enters step 602 and step 603 until the electrode sheet is qualified.

[0129] Steps 601 to 604 in this embodiment are substantially the same as steps 101 to 104 in the above embodiment. To avoid repetition, they will not be elaborated here.

[0130] On the other hand, this application provides a secondary battery, which is prepared by the preparation method of the secondary battery in the above embodiment.

[0131] The secondary battery in this embodiment is prepared by the preparation method of the secondary battery in the above embodiment. The secondary battery is a secondary battery that has passed the porosity detection and is qualified, improving the wettability of the electrode sheet in the secondary battery, thereby improving the ion transport performance of the electrode sheet in the secondary battery and improving the electrical performance of the secondary battery.

[0132] Specifically, the electrode sheet of the secondary battery in this embodiment has gone through processes such as electrode sheet loading, unwinding and running the tape, electrode sheet rolling, thickness detection, porosity detection, winding and unloading. After the electrode sheet winding and unloading are completed, subsequent winding and unloading operations are performed on the electrode sheet. Then, cell assembly, liquid injection, and encapsulation are carried out to form a secondary battery.

[0133] On the other hand, this application provides an energy storage system, including: a plurality of secondary batteries of the above embodiments.

[0134] The energy storage system of this embodiment includes a plurality of secondary batteries of the above embodiments. Among them, the secondary battery is a secondary battery that has passed the porosity detection and is qualified, which improves the wettability of the electrode sheet in the secondary battery, thereby improving the electrical performance of the secondary battery and the performance of the energy storage system.

[0135] Specifically, after the secondary battery is encapsulated, operations such as cell stacking, tab processing, module encapsulation, system assembly, and energy storage system integration are sequentially performed on the secondary battery to form an energy storage system, which can be applied in various scenarios, including power storage, power grid peak shaving, and supporting renewable energy.

[0136] On yet another aspect, this application provides an electrical device, including: the energy storage system of the above embodiments.

[0137] The electrical device of this embodiment includes the energy storage system of the above embodiments. Among them, the secondary battery in the energy storage system is a secondary battery that has passed the porosity detection and is qualified, and the electrical performance of the secondary battery is relatively high, which improves the performance of power consumption.

[0138] The electrical device of this embodiment can be a portable terminal, a pure electric vehicle, a hybrid electric vehicle, an electric ship, a smart home appliance, etc.

[0139] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing this application. In actual applications, various changes can be made to them in form and details without departing from the spirit and scope of this application.

Claims

1. A method for preparing a secondary battery, characterized in that, Including: Providing a pole piece, the pole piece being a positive pole piece or a negative pole piece, and the pole piece being the pole piece after a rolling operation; Obtaining the actual porosity of the pole piece; Judging whether the pole piece is qualified according to the actual porosity; When the pole piece is qualified, winding, blanking, cell assembly, liquid injection, and encapsulation are sequentially performed on the pole piece to form a secondary battery; When the pole piece is unqualified, laser treatment is performed on the pole piece to form laser pores; the steps of obtaining the actual porosity of the pole piece and the step of judging whether the pole piece is qualified according to the actual porosity are repeated until the pole piece is qualified.

2. The manufacturing method of the secondary battery according to claim 1, wherein The judging whether the pole piece is qualified according to the actual porosity includes: Calculating the deviation between the actual porosity and the target porosity, and 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 is less than or equal to a preset threshold, it is determined that the pole piece is qualified; when the deviation is greater than the preset threshold, it is determined that the pole piece is unqualified; the preset threshold is greater than 0 and less than or equal to 10%.

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

4. The method for preparing a secondary battery according to claim 3, wherein The obtaining the image of the pole piece includes: Using a area array CCD image sensor or a linear array CDD image sensor to obtain an image of the pole piece; the image is an image of a local area in the pole piece; Obtaining the area S of the electrode tab according to the image total and the area S of the particle region in the electrode tab solid , including: Obtain the overall area of the image as the area S of the pole piece total , and calculate the area S of the particle region in the image using the grayscale algorithm solid .

5. The method for preparing a secondary battery according to claim 3 or 4, characterized in that, The laser pores are round holes; before performing laser treatment on the pole piece to form laser pores, it includes: Obtain the radius of the circular hole according to the deviation and the area of the pole piece. The calculation formula for the radius r of the circular hole is: r = sqrt(3×δ1×S total / Pi); Pi is the pi; S total is the area of the pole piece; The performing laser treatment on the pole piece to form laser pores includes: Performing laser treatment on the pole piece according to the radius r of the round hole to form the laser pores.

6. The method for preparing a secondary battery according to claim 3 or 4, wherein, The laser pores are long strip-shaped grooves; before performing laser treatment on the pole piece to form laser pores, it includes: Obtain the dimensions of the elongated groove according to the deviation and the area of the electrode tab; the dimensions of the elongated groove include the length and width of the elongated groove, and the calculation formula for the length L of the elongated groove is: L = 3×δ1×S total / W, S total is the area of the electrode tab, W is the width of the elongated groove, and W is in the range of 0.05 μm to 0.1 μm; The performing laser treatment on the pole piece to form laser pores includes: Performing laser treatment on the pole piece according to the size of the long strip-shaped groove to form the laser pores.

7. The method for preparing a secondary battery according to claim 1, characterized in that, Before performing laser treatment on the pole piece to form laser pores, it includes: Obtaining the thickness of the pole piece, and determining the parameters of the laser treatment according to the thickness, and 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 performing laser treatment on the pole piece to form laser pores includes: Performing laser treatment on the pole piece according to the parameters of the laser treatment to form the laser pores.

8. A secondary battery, characterized in that, The secondary battery is prepared by the method for preparing a secondary battery according to any one of claims 1 to 7.

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

10. An electrical device, characterized in that, Comprising: An energy storage system as claimed in claim 9.

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