Electrode plate laminated body, preparation method and system thereof and soft package battery

Abstract

The invention relates to the technical field of batteries, in particular to an electrode slice lamination body, a preparation method and system thereof and a soft package battery. The electrode plate laminated body comprises a plurality of positive plates, a plurality of negative plates and a plurality of diaphragms; the positive plates and the negative plates are alternately stacked; the diaphragms are arranged between the adjacent positive plates and negative plates; the mass difference between any two adjacent positive plates is less than or equal to 0.0481 g; the mass difference between any two adjacent negative plates is less than or equal to 0.0525 g; and the mass difference between any adjacent positive plate and negative plate ranges from 0.7913 g to 0.8919 g. In the electrode plate laminated body, the positive electrode plate and the negative electrode plate respectively have relatively high consistency, and the positive electrode plate and the negative electrode plate are matched with each other according to a proper quality difference, so that the electrochemical performance of the battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and more particularly, to an electrode sheet laminate, a preparation method, a system thereof, and a soft-pack battery. Background Art

[0002] Currently, lithium-ion batteries have been widely used in various aspects of life. Among them, soft-pack batteries are a new type of battery, which have the advantages of small size, light weight, and strong flexibility. Therefore, they have been widely used in the fields of electric vehicles, drones, mobile phones, etc. Soft-pack batteries mainly include important components such as battery cells (including positive and negative electrode sheets, separators, and electrolytes) and electrode tabs. In the existing preparation methods, there are defects in the consistency of the positive and negative electrode sheets, which will affect the electrochemical performance of the prepared batteries. Therefore, how to ensure the consistency of the positive and negative electrode sheets is crucial for improving the electrochemical performance of the batteries.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] An object of the present invention is to provide an electrode sheet laminate, which has good consistency, and the positive and negative electrode sheets cooperate with each other with an appropriate mass difference, so as to improve the electrochemical performance of the battery.

[0005] Another object of the present invention is to provide a preparation method of the electrode sheet laminate, by screening, matching, and laminating the positive and negative electrode sheets, so as to improve the consistency of the battery and ensure the electrochemical performance and safety performance of the battery.

[0006] Another object of the present invention is to provide a sheet matching system for implementing the preparation method of the electrode sheet laminate, which has high working efficiency and high safety.

[0007] Another object of the present invention is to provide a soft-pack battery.

[0008] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0009] An electrode sheet laminate includes a plurality of positive electrode sheets, a plurality of negative electrode sheets, and a plurality of separators; the positive electrode sheets and the negative electrode sheets are alternately laminated; the separators are disposed between adjacent positive electrode sheets and negative electrode sheets;

[0010] The mass difference between any two adjacent positive electrode sheets is less than or equal to 0.0481 g;

[0011] The mass difference between any two adjacent negative electrode sheets is less than or equal to 0.0525 g;

[0012] The mass difference between any adjacent positive electrode sheet and negative electrode sheet ranges from 0.7913 g to 0.8919 g.

[0013] In one embodiment, along the same thickness direction of the electrode sheet laminate, the mass of the positive electrode sheet and the mass of the negative electrode sheet each independently increase gradually.

[0014] The method for preparing the electrode sheet laminate as described above includes the following steps:

[0015] (a) Obtain positive electrode sheets and negative electrode sheets without appearance defects; obtain the mass of each positive electrode sheet and the mass of each negative electrode sheet;

[0016] (b) According to the N / P value range of the battery, obtain the theoretical masses M1 to M2 of the positive electrode sheets and the theoretical masses M3 to M4 of the negative electrode sheets; perform a first screening on the positive electrode sheets and negative electrode sheets in step (a) respectively, and retain the positive electrode sheets within the range of M1 to M2 and the negative electrode sheets within the range of M3 to M4;

[0017] (c) Respectively obtain the average mass of the positive electrode sheets and the average mass of the negative electrode sheets in step (b), and then perform a second screening, set the theoretical mass deviation value range t 0 , and obtain the positive electrode sheets and negative electrode sheets that meet the theoretical mass deviation value range t 0 ; then sort the positive electrode sheets and negative electrode sheets respectively in ascending order of mass and perform piece matching one by one, and stack the positive electrode sheets, negative electrode sheets and separator to obtain an electrode sheet laminate.

[0018] In one embodiment, it further includes: measuring the vertical resistivity of the positive electrode sheets and negative electrode sheets after the first screening in step (b) respectively, and retaining the positive electrode sheets and negative electrode sheets with qualified vertical resistivity; then measuring the peel strength, and obtaining the positive electrode sheets and negative electrode sheets with qualified peel strength.

[0019] In one embodiment, the qualified range of the vertical resistivity of the positive electrode sheet is 0.95X 1 ~1.05X 1 , where X 1 represents the average vertical resistivity of the positive electrode sheet.

[0020] In one embodiment, the qualified range of the vertical resistivity of the negative electrode sheet is 0.95X 2 ~1.05X 2 , where X 2 represents the average vertical resistivity of the negative electrode sheet.

[0021] In one embodiment, the qualified range of the peel strength of the positive electrode sheet is 600 - 700 N / m.

[0022] In one embodiment, the qualified range of the peel strength of the negative electrode sheet is 45 - 55 N / m.

[0023] In one embodiment, the range of the theoretical mass deviation value t 0 ≤0.5; the actual deviation value t of each positive electrode sheet or negative electrode sheet is calculated according to the formula t = (actual mass of the electrode sheet - average mass of the electrode sheet) / average mass of the electrode sheet × 100, and the absolute value of the obtained actual deviation value t is less than or equal to the theoretical mass deviation value t 0 for the positive electrode sheet and the negative electrode sheet.

[0024] The system for implementing the preparation method of the electrode sheet laminate includes a defect detection unit, a first screening unit, a second screening and sheet matching unit, and a laminating unit; the defect detection unit is used to detect the appearance defects of the positive electrode sheet and the negative electrode sheet to be screened, so as to obtain the positive electrode sheet and the negative electrode sheet without appearance defects; the first screening unit is used to perform the first screening on the positive electrode sheet and the negative electrode sheet without appearance defects, so as to obtain the positive electrode sheet within the range of M1 to M2 and the negative electrode sheet within the range of M3 to M4; the second screening and sheet matching unit is used to perform the second screening and sheet matching on the positive electrode sheet and the negative electrode sheet after the first screening; the laminating unit is used to laminate the positive electrode sheet and the negative electrode sheet after the second screening and sheet matching, so as to obtain the electrode sheet laminate.

[0025] In one embodiment, a vertical resistivity measurement and screening unit and a peel strength measurement and screening unit are further arranged between the first screening unit and the second screening and sheet matching unit; the vertical resistivity measurement and screening unit is used to measure and screen the vertical resistivity of the positive electrode sheet and the negative electrode sheet after the first screening, so as to obtain the positive electrode sheet and the negative electrode sheet with qualified vertical resistivity, and the peel strength measurement and screening unit is used to measure and screen the peel strength of the positive electrode sheet and the negative electrode sheet after the vertical resistivity measurement and screening, so as to obtain the positive electrode sheet and the negative electrode sheet with qualified peel strength.

[0026] A soft package battery includes the electrode sheet laminate as described above, or the electrode sheet laminate prepared by the preparation method of the electrode sheet laminate as described above.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The electrode sheet laminate of the present invention has good consistency, and the positive and negative electrode sheets cooperate with each other, which can improve the electrochemical performance and safety performance of the battery.

[0029] (2) The method of the present invention obtains the positive electrode sheet and the negative electrode sheet with good consistency by respectively performing appearance defect detection, first quality screening, and second quality screening on the positive electrode sheet and the negative electrode sheet, and then performs sheet matching and lamination in order of quality from high to low, so as to improve the consistency of the battery and obtain a battery with more excellent electrochemical performance and higher safety.

[0030] (3) Through the mutual cooperation of each unit, the system of the present invention can screen, piece and stack the prepared positive and negative electrode sheets, with high efficiency and high safety; it can improve the consistency of the battery, which is beneficial to improving the electrochemical performance and safety performance of the finally obtained battery.

[0031] (4) The soft-pack battery of the present invention has excellent electrochemical performance and safety performance. Description of the Drawings

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a cyclic performance diagram of the battery prepared from the positive and negative electrode sheets of Example 1 and Comparative Example 1 of the present invention. Detailed Embodiments

[0034] The following will describe the implementation schemes of the present invention in detail in conjunction with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0035] According to one aspect of the present invention, the present invention relates to an electrode sheet laminate, comprising a plurality of positive electrode sheets, a plurality of negative electrode sheets and a plurality of separators; the positive electrode sheets and the negative electrode sheets are arranged in an alternating laminated manner; the separators are arranged between adjacent positive electrode sheets and negative electrode sheets; the mass difference between any two adjacent positive electrode sheets is less than or equal to 0.0481 g; the mass difference between any two adjacent negative electrode sheets is less than or equal to 0.0525 g; the mass difference range between any adjacent positive electrode sheet and negative electrode sheet is 0.7913 g to 0.8919 g.

[0036] The electrode sheet laminate of the present invention has good consistency, and the positive and negative electrode sheets cooperate with each other, which can improve the electrochemical performance and safety performance of the battery.

[0037] In one embodiment, along the same thickness direction of the electrode sheet laminate, the mass of the positive electrode sheet and the mass of the negative electrode sheet independently increase gradually. In the electrode sheet laminate of the present invention, the masses of the positive electrode sheet and the negative electrode sheet have the above characteristics, which are more beneficial to improving the electrochemical performance of the battery.

[0038] According to another aspect of the present invention, the present invention also relates to a method for preparing the electrode sheet laminate as described above, comprising the following steps:

[0039] (a) Obtain a positive electrode sheet and a negative electrode sheet without appearance defects; obtain the mass of each positive electrode sheet and the mass of each negative electrode sheet;

[0040] (b) According to the N / P value range of the battery, obtain the theoretical masses M1 to M2 of the positive electrode sheets and the theoretical masses M3 to M4 of the negative electrode sheets; perform a first screening on the positive electrode sheets and the negative electrode sheets in step (a), and retain the positive electrode sheets within the range of M1 to M2 and the negative electrode sheets within the range of M3 to M4;

[0041] (c) Respectively obtain the average mass of the positive electrode sheets and the average mass of the negative electrode sheets in step (b), and then perform a second screening, set the theoretical mass deviation value range t 0 , and obtain the positive electrode sheets and negative electrode sheets that meet the theoretical mass deviation value range t 0 ; then sort the positive electrode sheets and negative electrode sheets in ascending order of mass and perform piece matching one by one, and stack the positive electrode sheets, negative electrode sheets and separator to obtain an electrode sheet laminate.

[0042] In the method of the present invention, by respectively performing appearance defect detection, first quality screening, and second quality screening on the positive electrode sheets and negative electrode sheets, positive electrode sheets and negative electrode sheets with good consistency are obtained, and then piece matching and stacking are performed in the order of mass from low to high to obtain a battery with more excellent electrochemical performance.

[0043] In one embodiment, it further includes: respectively measuring the vertical resistivity of the positive electrode sheets and negative electrode sheets after the first screening in step (b), and retaining the positive electrode sheets and negative electrode sheets with qualified vertical resistivity; then measuring the peel strength to obtain the positive electrode sheets and negative electrode sheets with qualified peel strength.

[0044] In the present invention, the method for measuring the vertical resistivity includes:

[0045] (1) Clamp the sample: Operate the test bench, lift the probe of the four-probe instrument, place the sample on the test bench, select the test point, and then press down the probe;

[0046] (2) Input the correction coefficients k1 and k2 into the main body of the four-probe instrument. Among them, when the coating thickness is 100 μm, k1 = 6.280 and k2 = 0.0628;

[0047] (3) Directly read the resistivity in the instrument measurement mode.

[0048] In the present invention, the test method for peel strength includes: first, bonding the pressure-sensitive tape to the stainless steel plate, then bonding the electrode sheet to the pressure-sensitive tape, clamping the electrode sheet with a tensile machine for 180° peeling, and recording the data of peel strength through an instrument. The test for peel strength is carried out in a sampling manner, and the electrode sheets after testing are not used anymore.

[0049] In one embodiment, the qualified range of the vertical resistivity of the positive electrode sheet is 0.95X 1 ~1.05X 1 , where X 1 represents the average vertical resistivity of the positive electrode sheet. In one embodiment, the qualified range of the vertical resistivity of the negative electrode sheet is 0.95X 2 ~1.05X 2 , where X 2 represents the average vertical resistivity of the negative electrode sheet. By measuring and screening the vertical resistivity of the positive electrode sheet and the negative electrode sheet respectively, the present invention limits the qualified range of the vertical resistivity, thereby ensuring that the electrochemical performance of the finally obtained battery is more excellent.

[0050] In one embodiment, the qualified range of the vertical resistivity of the positive electrode sheet is 294.5~325.5 Ω·cm. In one embodiment, the qualified range of the vertical resistivity of the negative electrode sheet is 712.5~787.5 Ω·cm. The present invention limits the qualified range of the vertical resistivity of the positive electrode sheet and the negative electrode sheet, thereby making the electrochemical performance of the finally obtained battery more excellent.

[0051] In one embodiment, the qualified range of the peel strength of the positive electrode sheet is 600~700 N / m, such as 600 N / m, 610 N / m, 620 N / m, 650 N / m, 660 N / m, 670 N / m, 680 N / m, 700 N / m, etc. In one embodiment, the qualified range of the peel strength of the negative electrode sheet is 45~55 N / m, such as 45 N / m, 46 N / m, 47 N / m, 48 N / m, 50 N / m, 55 N / m, etc.

[0052] In one embodiment, the range of the theoretical mass deviation value t 0 ≤0.5; the actual deviation value t of each positive electrode sheet or negative electrode sheet is calculated according to the formula t=(actual mass of the electrode sheet - average mass of the electrode sheet) / average mass of the electrode sheet×100, and positive electrode sheets and negative electrode sheets with the absolute value of the obtained actual deviation value t less than or equal to the theoretical mass deviation value t 0 are obtained.

[0053] In one embodiment, the theoretical N / P = the negative electrode capacity per unit area / the positive electrode capacity per unit area = (the negative electrode surface density × the mass ratio of the negative electrode active material × the specific capacity of the negative electrode active material) / (the positive electrode surface density × the mass ratio of the positive electrode active material × the specific capacity of the positive electrode active material). In one embodiment, the N / P = 1.14 to 1.16.

[0054] In one embodiment, the method for obtaining the theoretical mass M1 - M2 of the positive electrode sheet includes: setting the mass ratio of the positive electrode active material, the mass ratio of the negative electrode active material, the negative electrode surface density, the specific capacity of the negative electrode, the specific capacity of the positive electrode, the width of the positive electrode sheet, the single-sided coating length, the double-sided coating length, and the mass of the positive electrode current collector; and calculating the theoretical mass M1 - M2 of the positive electrode sheet according to the calculation formula of the theoretical N / P.

[0055] In one embodiment, the method for obtaining the theoretical mass M3 - M4 of the negative electrode sheet includes: setting the mass ratio of the positive electrode active material, the mass ratio of the negative electrode active material, the positive electrode surface density, the specific capacity of the negative electrode, the specific capacity of the positive electrode, the width of the negative electrode sheet, the single-sided coating length, and the double-sided coating length, and calculating the theoretical mass M3 - M4 of the positive electrode sheet according to the calculation formula of the theoretical N / P.

[0056] According to another aspect of the present invention, the present invention also relates to a system for implementing the preparation method of the electrode sheet laminate, including a defect detection unit, a first screening unit, a second screening and sheet matching unit, and a laminating unit; the defect detection unit is used to detect the appearance defects of the positive electrode sheet and the negative electrode sheet to be screened, so as to obtain a positive electrode sheet and a negative electrode sheet without appearance defects; the first screening unit is used to perform the first screening on the positive electrode sheet and the negative electrode sheet without appearance defects, so as to obtain a positive electrode sheet within the range of M1 - M2 and a negative electrode sheet within the range of M3 - M4; the second screening and sheet matching unit is used to perform the second screening and sheet matching on the positive electrode sheet and the negative electrode sheet after the first screening; the laminating unit is used to laminate the positive electrode sheet and the negative electrode sheet after the second screening and sheet matching to obtain an electrode sheet laminate.

[0057] Through the mutual cooperation of each unit, the system of the present invention can screen, match, and laminate the prepared positive and negative electrode sheets, with high efficiency and high safety; it can improve the consistency of the battery, which is beneficial to improving the electrochemical performance and safety performance of the finally obtained battery.

[0058] In one embodiment, a vertical resistivity measurement and screening unit and a peel strength measurement and screening unit are further provided between the first screening unit and the second screening and wafer matching unit; the vertical resistivity measurement and screening unit is used to measure and screen the vertical resistivity of the positive and negative electrode sheets after the first screening to obtain positive and negative electrode sheets with qualified vertical resistivity, and the peel strength measurement and screening unit is used to measure and screen the peel strength of the positive and negative electrode sheets that have completed the measurement and screening of the vertical resistivity to obtain positive and negative electrode sheets with qualified peel strength.

[0059] In one embodiment, the detection device involved in the present invention includes: an SZT-C type rapid constant voltage test bench, an ST-2258C type multi-functional digital four-probe tester, and a tensile testing machine.

[0060] In one embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector; the positive electrode material layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. In one embodiment, the preparation method of the positive electrode sheet includes: mixing a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a solvent, and stirring to obtain a positive electrode slurry; coating the positive electrode slurry on at least one surface of a positive electrode current collector foil tape, drying and compressing to obtain a positive electrode tape, and cutting the positive electrode tape to obtain a positive electrode sheet.

[0061] In one embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector; the negative electrode material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. In one embodiment, the preparation method of the negative electrode sheet includes: mixing a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and a solvent, and stirring to obtain a negative electrode slurry; coating the negative electrode slurry on at least one surface of a negative electrode current collector foil tape, drying and compressing to obtain a negative electrode tape, and cutting the negative electrode tape to obtain a negative electrode sheet.

[0062] According to the above method, the present invention prepares a number of positive and negative electrode sheets by adjusting process parameters. Then, the positive and negative electrode sheets are screened and wafer-matched respectively according to the above preparation method of the laminate, and the screened positive and negative electrode sheets are mechanically laminated with a separator to obtain an electrode sheet laminate.

[0063] According to another aspect of the present invention, the present invention also relates to a soft-pack battery, including the electrode sheet laminate described above, or an electrode sheet laminate prepared by the preparation method of the electrode sheet laminate described above. For the soft-pack battery of the present invention, the positive and negative electrode sheets have good consistency, the positive and negative electrode sheets in the laminate have a suitable mass difference, and it has excellent electrochemical performance and safety performance.

[0064] A method for preparing a soft-pack battery, obtaining an electrode sheet laminate according to the above method; thermally pressing, casing, injecting electrolyte, pressure forming, and sealing the electrode sheet laminate.

[0065] In one embodiment, the thermal pressing includes: heating a hot press to a certain temperature, placing the laminate on the hot press plate, and starting the machine to apply pressure. Casing includes: cutting an aluminum-plastic film of a certain size according to the required specifications, with the tab glue protruding 0.5 mm from the aluminum-plastic film during top sealing, 5 mm for left side sealing, pasting a label after top sealing and side sealing are completed, and weighing and recording the batteries in sequence using a balance. Injecting electrolyte includes: placing the baked battery in a glove box to cool down, dropping an appropriate amount of electrolyte matching the battery, and after injecting electrolyte, withdrawing it into the glove box chamber and maintaining pressure for a certain time. Pressure forming includes: clamping the battery with the upper clamp plate, connecting the positive and negative electrodes to the forming equipment, and placing it in an oven for high-temperature forming. Sealing includes: after high-temperature forming, first measuring the internal resistance of the battery with the upper clamp plate at high temperature; removing the clamp plate, cutting open the air bag of the battery; placing the battery in a vertical vacuum sealing machine for secondary sealing, cutting off the excess air bag after sealing; weighing and recording the data of the battery and the cut air bag separately, and pasting green adhesive tapes on the top sealing and left and right side sealings of the weighed battery; then measuring the voltage and internal resistance.

[0066] The following further explains with specific embodiments.

[0067] Example 1

[0068] A method for preparing an electrode sheet laminate of a soft-pack battery includes the following steps:

[0069] (1) Obtain a number of positive electrode sheets and negative electrode sheets, respectively perform surface defect detection on the positive electrode sheets and negative electrode sheets, and leave the positive electrode sheets and negative electrode sheets without appearance defects.

[0070] (2) Weigh the masses of the positive electrode sheets and negative electrode sheets without appearance defects in step (1) respectively, and group and number the positive electrode sheets and negative electrode sheets according to their masses.

[0071] (3) According to the theoretical N / P value of the battery, obtain the theoretical masses M1 - M2 of the positive electrode sheets and the theoretical masses M3 - M4 of the negative electrode sheets;

[0072] Among them, the method for obtaining the theoretical masses M1 - M2 of the positive electrode sheets includes: assuming N / P = 1.15 ± 0.01, the mass ratio of the positive active material is 96%, the mass ratio of the negative active material is 96%, and the negative surface density is 22.45 mg / cm 2, the negative electrode specific capacity is 355 mAh / g, the positive electrode specific capacity is 198 mAh / g, the width of the positive electrode sheet is 40 mm, the single-sided coating length is 435 mm, the double-sided coating length is 375 mm, and the weight of the aluminum foil is 775 mg; according to the N / P value calculation formula: N / P = (negative electrode surface density × mass ratio of negative electrode active material × negative electrode active material specific capacity) / (positive electrode surface density × mass ratio of positive electrode active material × positive electrode active material specific capacity), the positive electrode surface density is calculated, and the theoretical mass M1 - M2 of the positive electrode sheet is 6396.3 mg - 6494.9 mg.

[0073] The method for obtaining the theoretical mass M3 - M4 of the negative electrode sheet includes: setting N / P = 1.15 ± 0.01, the mass ratio of the positive electrode active material is 96%, the mass ratio of the negative electrode active material is 96%, and the positive electrode surface density is 35 mg / cm 2 , the negative electrode specific capacity is 355 mAh / g, the positive electrode specific capacity is 198 mAh / g, the width of the negative electrode sheet is 42 mm, the single-sided coating length is 436 mm, the double-sided coating length is 389 mm, and the weight of the copper foil is 1736.3 mg; according to the above N / P value calculation formula, the surface density of the negative electrode sheet and the theoretical mass M3 - M4 of the negative electrode sheet are obtained, and the theoretical mass M3 - M4 of the negative electrode sheet is 5591.8 mg - 5658.7 mg.

[0074] Perform the first screening on the positive electrode sheet and the negative electrode sheet respectively, and retain the positive electrode sheet within the range of M1 - M2 and the negative electrode sheet within the range of M3 - M4.

[0075] (4) Measure the vertical resistivity of the positive electrode sheet and the negative electrode sheet after the first screening respectively: the standard value of the average resistivity of the positive electrode sheet is 310 Ω·cm, and retain the positive electrode sheet with resistivity between 294.5 Ω·cm and 325.5 Ω·cm; the standard value of the average resistivity is 750 mΩ·cm, and select the negative electrode sheet with resistivity between 712.5 Ω·cm and 787.5 Ω·cm.

[0076] (5) Then measure the peel strength of the positive electrode sheet and the negative electrode sheet retained in the vertical resistivity measurement in step (4) respectively, and obtain the positive electrode sheet and the negative electrode sheet with qualified peel strength; among them, the qualified peel strength range of the negative electrode sheet is 45 - 55 N / m, and the qualified peel strength range of the positive electrode sheet is 600 - 700 N / m.

[0077] (6) Respectively obtain the average mass of the positive electrode sheet and the average mass of the negative electrode sheet in step (5), perform the second screening according to the required number of electrode sheets, and set the theoretical mass deviation value range t 0 , obtain the positive electrode sheet and the negative electrode sheet that meet the deviation value range t 0 ;

[0078] During the second screening process, the masses of the positive electrode sheets are shown in Table 1.

[0079] Table 1 Mass of the Positive Electrode Sheets

[0080]

[0081]

[0082] The average mass of the above positive electrode sheets is 6.4711 g. According to the required number of electrode sheets, the deviation value is 0.31. Retain the positive electrode sheets with the absolute value of the deviation less than 0.31, and sort them in ascending order of mass.

[0083] During the second screening process, the masses of the negative electrode sheets are shown in Table 2.

[0084] Table 2 Mass of the Negative Electrode Sheets

[0085]

[0086]

[0087] The average mass of the above negative electrode sheets is 5.6170. According to the required number of electrode sheets, the deviation value is 0.34. Select the negative electrode sheets with the absolute value of the deviation less than 0.34 in Table 2, and sort them in ascending order of mass.

[0088] Pair the sorted positive electrode sheets and the sorted negative electrode sheets one by one in ascending order of mass, and stack the paired positive electrode sheets, negative electrode sheets, and separator to obtain an electrode sheet laminate. In the same thickness direction of the electrode sheet laminate, the mass of the positive electrode sheets gradually increases, and the mass of the negative electrode sheets gradually increases.

[0089] Example 2

[0090] A method for preparing an electrode sheet laminate of a soft-pack battery, except that the sorted positive electrode sheets and the sorted negative electrode sheets are directly stacked with the separator without sorting by mass from low to high, and other conditions are the same as in Example 1.

[0091] Example 3

[0092] The sheet pairing system used in the sheet pairing method of the battery electrode sheet includes a defect detection unit, a first screening unit, a vertical resistivity measurement and screening unit, a peel strength measurement and screening unit, a second screening and sheet pairing unit, and a stacking unit.

[0093] A number of positive electrode sheets and negative electrode sheets are respectively subjected to surface defect detection in a detection unit to obtain positive electrode sheets and negative electrode sheets without appearance defects; according to the theoretical masses M1 to M2 and the theoretical mass M3 to M4 of the negative electrode sheets, the positive electrode sheets and negative electrode sheets are respectively subjected to a first screening. After being detected by a first mass detector, the relevant electrode sheets are retained and rejected. The positive electrode sheets within the range of M1 to M2 and the negative electrode sheets within the range of M3 to M4 are retained and further sent to a vertical resistivity measurement and screening unit to reject unqualified positive and negative electrode sheets.

[0094] The positive electrode sheets and negative electrode sheets are respectively subjected to measurement and screening in a vertical resistivity measurement and screening unit. The qualified range of the vertical resistivity of the positive electrode sheets is 0.95X 1 ~1.05X 1 , where X 1 represents the average vertical resistivity of the positive electrode sheets; the qualified range of the vertical resistivity of the negative electrode sheets is 0.95X 2 ~1.05X 2 , where X 2 represents the average vertical resistivity of the negative electrode sheets.

[0095] The positive electrode sheets and negative electrode sheets with qualified vertical resistivity are successively sent to a peel strength measurement and screening unit; positive electrode sheets with a peel strength range of 600 to 700 N / m and negative electrode sheets with a peel strength range of 45 to 55 N / m are obtained.

[0096] The positive electrode sheets and negative electrode sheets with qualified peel strength are successively sent to a second screening and sheet matching unit; the average mass of the positive electrode sheets and the average mass of the negative electrode sheets are obtained, and a second screening is performed according to the required number of electrode sheets. A theoretical mass deviation value range t 0 is set, and positive electrode sheets and negative electrode sheets that meet the deviation value range t 0 are obtained; then the positive electrode sheets and negative electrode sheets are respectively sorted from low to high in terms of mass and placed in a sheet matching device, so that the positive electrode sheets and negative electrode sheets are matched one by one in the order of increasing mass;

[0097] The positive electrode sheets and negative electrode sheets that have completed sheet matching are sent to a lamination unit for lamination treatment with a separator to obtain an electrode sheet laminate.

[0098] Comparative Example 1

[0099] In the manner of Example 1, a number of positive electrode sheets and negative electrode sheets are obtained. Without performing the sheet matching method of Example 1, the positive electrode sheets and negative electrode sheets are directly divided into three groups, and each group contains the same number of positive electrode sheets and negative electrode sheets as the final sheet matching number in Example 1.

[0100] Test Example

[0101] The positive and negative electrode sheets in Example 1 and Comparative Example 1 were respectively used to prepare soft-pack batteries. The specific preparation method of the soft-pack batteries includes:

[0102] (1) Welding the tabs of the positive and negative electrode sheets

[0103] Weld the tabs, adjust the parameters required for tab welding, leave a certain size from the positive and negative electrode sheets to the tab glue, and the solder joints should be firm.

[0104] (2) Winding the electrode core

[0105] ① Place the positive and negative electrode sheets in the electrode sheet slots of the winding machine in ascending order of their numbers. First, place the negative electrode sheet, and the negative electrode sheet should be in the middle of the separator.

[0106] ② Then place the positive electrode sheet in ascending order of its number. The positive electrode sheet should be in the middle of the negative electrode sheet. Align the electrode sheets and perform winding. Note: The positive and negative electrodes should correspond one by one in number.

[0107] (3) Hot pressing

[0108] ① Heat the upper and lower parts of the hot press to a certain temperature.

[0109] ② Place the electrode core on the hot press plate and start the machine to apply pressure.

[0110] (4) Inserting the electrode core into the shell

[0111] ① Cut the aluminum-plastic film (cut according to the required specifications)

[0112] ② When top-sealing, the tab glue should protrude 0.5 mm from the aluminum-plastic film.

[0113] ③ Seal 5 mm on the left side.

[0114] ④ After top-sealing and side-sealing, stick on the label, and weigh and record the batteries in sequence with a balance.

[0115] (5) Injecting electrolyte and sealing

[0116] ① Put the baked battery into the glove box to cool down.

[0117] ② Drop in an appropriate amount of electrolyte matching the battery. After injection, draw it into the glove box chamber and maintain pressure for a certain period of time.

[0118] (6) Pressurizing formation

[0119] Clamp the battery with the upper and lower clamping plates well, connect the positive and negative electrodes to the formation equipment, and place it in the oven for high-temperature formation at 45 °C.

[0120] (7) Second sealing after formation

[0121] ① After formation, put the battery into a vertical vacuum sealing machine for secondary sealing. After sealing, cut off the excess air bag.

[0122] ② Weigh the battery and the cut airbag separately and record the data. After weighing the battery, apply green tape to the top seal and the left and right side seals.

[0123] ③ Then measure the voltage and internal resistance.

[0124] Further test the electrochemical performance of the soft-pack battery.

[0125] After the positive and negative electrode sheets of Example 1 and Comparative Example 1 of the present invention are made into finished batteries according to the above method, the batteries are subjected to a cycle performance test. The test conditions are: 25 °C, voltage range 2.8 - 4.2 V, charge at 0.5 C and discharge at 1 C. The specific test results are shown in Table 1 and Figure 1 as follows.

[0126] Table 1 Test results of the electrochemical performance of the battery

[0127]

[0128] As can be seen from Table 1, the preparation method of the electrode sheet laminate of the present invention can improve the consistency of the positive and negative electrode sheets. At the same time, the positive and negative electrode sheets in the electrode sheet laminate are laminated in ascending order of mass, which is more conducive to improving the capacity retention rate of the battery.

[0129] For the laminate of Comparative Example 1, no screening and matching of the positive and negative electrode sheets are carried out, and the capacity retention rate of the obtained battery is relatively low.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrode sheet laminate, characterized in that, it includes a plurality of positive electrode sheets, a plurality of negative electrode sheets and a plurality of separators; the positive electrode sheets and the negative electrode sheets are arranged in an alternating laminated manner; the separators are arranged between adjacent positive electrode sheets and negative electrode sheets; the mass difference between any two adjacent positive electrode sheets is less than or equal to 0.0481 g; the mass difference between any two adjacent negative electrode sheets is less than or equal to 0.0525 g; the mass difference range between any adjacent positive electrode sheet and negative electrode sheet is 0.7913 g to 0.8919 g.

2. The electrode sheet laminate according to claim 1, characterized in that, along the same thickness direction of the electrode sheet laminate, the mass of the positive electrode sheet and the mass of the negative electrode sheet independently increase gradually.

3. A method for preparing the electrode sheet laminate according to claim 1 or 2, characterized in that, it includes the following steps: (a) Obtain positive electrode sheets and negative electrode sheets without appearance defects; obtain the mass of each positive electrode sheet and the mass of each negative electrode sheet; (b) According to the N / P value range of the battery, obtain the theoretical mass M1 to M2 of the positive electrode sheet and the theoretical mass M3 to M4 of the negative electrode sheet; perform the first screening on the positive electrode sheets and negative electrode sheets in step (a) respectively, and retain the positive electrode sheets within the range of M1 to M2 and the negative electrode sheets within the range of M3 to M4; (c) Obtain the average mass of the positive electrode sheet and the average mass of the negative electrode sheet described in step (b) respectively, and then conduct a second screening to set the theoretical mass deviation value range t 0 , and obtain the positive electrode sheet and the negative electrode sheet that meet the theoretical mass deviation value range t 0 ; then sort the positive electrode sheet and the negative electrode sheet respectively in ascending order of mass and pair them one by one, and stack the positive electrode sheet, the negative electrode sheet and the separator to obtain an electrode sheet laminate.

4. The method for preparing the electrode sheet laminate according to claim 3, characterized in that, it further includes: measuring the vertical resistivity of the positive electrode sheets and negative electrode sheets after the first screening in step (b) respectively, and retaining the positive electrode sheets and negative electrode sheets with qualified vertical resistivity; then measuring the peel strength, and obtaining the positive electrode sheets and negative electrode sheets with qualified peel strength.

5. The method for preparing the electrode sheet laminate according to claim 4, characterized in that, The qualified range of the vertical resistivity of the positive electrode sheet is 0.95X 1 ~1.05X 1 , where X 1 represents the average vertical resistivity of the positive electrode sheet; The qualified range of the vertical resistivity of the negative electrode sheet is 0.95X 2 ~1.05X 2 , where X 2 represents the average vertical resistivity of the negative electrode sheet.

6. The method for preparing the electrode sheet laminate according to claim 1, characterized in that, the qualified range of the peel strength of the positive electrode sheet is 600 to 700 N / m; the qualified range of the peel strength of the negative electrode sheet is 45 to 55 N / m.

7. The method for preparing the electrode sheet laminate according to claim 1, characterized in that, The theoretical mass deviation value range t 0 ≤0.5; The actual deviation value t of each of the positive electrode plates or negative electrode plates is calculated according to the formula t = (actual mass of the electrode plate - average mass of the electrode plate) / average mass of the electrode plate × 100, and positive electrode plates and negative electrode plates with the absolute value of the obtained actual deviation value t less than or equal to the theoretical mass deviation value t are obtained. 0 ​ 8. A system for implementing the method for preparing the electrode sheet laminate according to any one of claims 3 to 7, characterized in that, it includes a defect detection unit, a first screening unit, a second screening and sheet matching unit, and a laminating unit; the defect detection unit is used to detect the appearance defects of the positive electrode sheets and negative electrode sheets to be screened, so as to obtain positive electrode sheets and negative electrode sheets without appearance defects; the first screening unit is used to perform the first screening on the positive electrode sheets and negative electrode sheets without appearance defects, so as to obtain positive electrode sheets within the range of M1 to M2 and negative electrode sheets within the range of M3 to M4; the second screening and sheet matching unit is used to perform the second screening and sheet matching on the positive electrode sheets and negative electrode sheets after the first screening; the laminating unit is used to laminate the positive electrode sheets and negative electrode sheets after the second screening and sheet matching to obtain the electrode sheet laminate.

9. The system according to claim 8, wherein a vertical resistivity measurement and screening unit and a peel strength measurement and screening unit are further provided between the first screening unit and the second screening and sheet matching unit; the vertical resistivity measurement and screening unit is used to measure and screen the vertical resistivity of the positive and negative electrode sheets after the first screening to obtain positive and negative electrode sheets with qualified vertical resistivity, and the peel strength measurement and screening unit is used to measure and screen the peel strength of the positive and negative electrode sheets that have completed the measurement and screening of the vertical resistivity to obtain positive and negative electrode sheets with qualified peel strength.

10. A soft-pack battery, characterized in that, it includes the electrode sheet laminate according to any one of claims 1 to 2, or the electrode sheet laminate prepared by the preparation method of the electrode sheet laminate according to any one of claims 3 to 7.

Images