Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device, the secondary battery comprises gummed paper, a positive pole piece, a negative pole piece and a diaphragm arranged between the positive pole piece and the negative pole piece, the positive pole piece comprises a positive pole lug, and the gummed paper is arranged between the diaphragm and the positive pole lug; the gummed paper comprises a porous base material and a glue layer arranged on at least one surface of the base material; wherein the adhesive layer comprises inert substances, the inert substances comprise a first inert substance and a second inert substance, the particle size of the first inert substance is d1nm, the particle size of the second inert substance is d2nm, d1 is more than 300 and less than or equal to 900, and d2 is more than or equal to 50 and less than or equal to 300; the average particle size of the first inert substance is D1 nm, the average particle size of the second inert substance is D2 nm, D1 is greater than or equal to 400 and less than or equal to 800, and D2 is greater than or equal to 100 and less than or equal to 200; in any area of the surface of the adhesive layer, the ratio of the number of particles of the first inert substance to the number of particles of the second inert substance is 3: 7-7: 3. Through the arrangement, the secondary battery has good dynamic performance.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] Secondary batteries (such as lithium-ion batteries) have the advantages of high energy density, long cycle life, low self-discharge rate and environmental protection and pollution-free, and have been widely used in aviation, aerospace, navigation, electric vehicles, consumer electronics and other fields. Lithium-ion batteries are composed of positive electrode plates, negative electrode plates, diaphragms, adhesive tapes and other components. The ion-conducting adhesive tape in existing lithium-ion batteries is produced by micro-gravure process. The adhesive layer is a mixed slurry (including boehmite, adhesive layer material and solvent) coated on the substrate. After the solvent evaporates, the place originally occupied by the solvent is pores. The boehmite in the adhesive layer is prone to agglomeration, resulting in excessive local impedance, which affects the dynamic performance of lithium-ion batteries. Summary of the invention

[0003] The purpose of the present application is to provide a secondary battery and an electronic device to improve the dynamic performance of the secondary battery.

[0004] It should be noted that in the invention content of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries of this application are not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0005] A first aspect of the present application provides a secondary battery, the secondary battery comprising adhesive tape, a positive electrode sheet, a negative electrode sheet and a separator arranged between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprising a positive electrode tab, the adhesive tape being between the separator and the positive electrode tab, the adhesive tape comprising a porous substrate and an adhesive layer arranged on at least one surface of the substrate; wherein the adhesive layer comprises an inert substance, the inert substance comprises a first inert substance and a second inert substance, the particle size of the first inert substance is d1 nm, the particle size of the second inert substance is d2 nm, and 300<d1≤900, 50≤d2≤300; the average particle size of the first inert substance is D1nm, the average particle size of the second inert substance is D2 nm, and 400≤D1≤800, 100≤D2≤200; in any area on the surface of the adhesive layer, the particle number ratio of the first inert substance to the second inert substance is 3:7 to 7:3. The secondary battery provided in the first aspect of the present application, by simultaneously adding a first inert substance with larger particles and a second inert substance with smaller particles in the glue layer, and regulating the average particle size of the first inert substance and the second inert substance, and the ratio of the number of particles of the first inert substance and the second inert substance within the scope of the present application, the first inert substance with larger particles and the second inert substance with smaller particles are matched, and the first inert substance with larger particles can support the pore formation on the surface of the porous substrate to improve the air permeability of the porous substrate, thereby improving the air permeability of the adhesive tape, so as to reduce the probability of lithium precipitation in the adhesive tape pasting area, and the second inert substance with smaller particles has a small pore formation pore, which can improve the bonding force of the glue layer, so as to reduce the probability of the adhesive tape falling off during the winding process. Thus, the dynamic performance of the secondary battery can be improved, and the processing performance of the secondary battery can also be improved. In addition, the adhesive tape of the present application has a high air permeability, and lithium ions can freely shuttle in the area where the adhesive tape is provided, so the capacity of the adhesive tape pasting area can still be exerted, thereby improving the energy density of the secondary battery.

[0006] In some embodiments of the present application, 1 / 7≤D2 / D1≤1 / 3. By adjusting the value of the ratio D2 / D1 between the average particle size of the second inert substance and the average particle size of the first inert substance within the above range, the probability of lithium precipitation in the adhesive tape area in the later stage of the secondary battery charge and discharge cycle can be reduced so that the secondary battery has good dynamic performance, and the probability of the adhesive layer falling off during the winding process of the adhesive tape is also reduced. In addition, lithium ions can freely shuttle in the area where the adhesive tape is provided, so the capacity of the adhesive tape area can still be utilized, thereby improving the energy density of the secondary battery.

[0007] In some embodiments of the present application, the average pore size of the porous substrate is P nm; D2 and P satisfy the following relationship: 0.5≤P / D2≤1. The value of the ratio P / D2 between the average pore size of the porous substrate and the average particle size of the second inert substance is regulated within the above range, the probability of the adhesive layer falling off during the winding process of the adhesive tape is low, and the probability of lithium deposition in the adhesive tape-pasted area in the later stage of the secondary battery charge and discharge cycle is low, so that the secondary battery has good dynamic performance. Lithium ions can shuttle freely in the area where the adhesive tape is set, so the capacity of the adhesive tape-pasted area can still be exerted, thereby improving the energy density of the secondary battery.

[0008] In some embodiments of the present application, 50≤P≤200. The average pore size of the porous substrate is adjusted within the above range, and the porous substrate has a suitable average pore size, which is conducive to better adhesion between the adhesive layer and the porous substrate and higher air permeability of the adhesive tape.

[0009] In some embodiments of the present application, the adhesive layer includes an adhesive layer binder, and the mass ratio of the inert substance to the adhesive layer binder is 3:7 to 7:3. The mass ratio of the inert substance to the adhesive layer binder is regulated within the above range, the probability of the adhesive layer falling off during the winding process is low, and the probability of lithium precipitation in the adhesive tape area in the later stage of the secondary battery charge and discharge cycle is low, so that the secondary battery has good dynamic performance. Lithium ions can shuttle freely in the area where the adhesive tape is provided, so the capacity of the adhesive tape area can still be exerted, thereby improving the energy density of the secondary battery.

[0010] In some embodiments of the present application, the air permeability of the adhesive tape is 180 s / 100 mL to 600 s / 100 mL, indicating that the adhesive tape has good air permeability.

[0011] In some embodiments of the present application, the porosity of the porous substrate is 25% to 55%. When the porosity of the porous substrate is controlled within the above range, the probability of interfacial lithium deposition in the secondary battery during the charge and discharge cycle is low, and the secondary battery has good kinetic performance.

[0012] In some embodiments of the present application, the thickness of the porous substrate is 9 μm to 24 μm. By adjusting the thickness of the porous substrate within the above range, the probability of local impedance becoming larger can be reduced, the occurrence of lithium precipitation at the interface of the secondary battery during charge and discharge cycles can be reduced, and the dynamic performance of the secondary battery can be improved. It can also reduce the loss of energy density caused by the excessive thickness of the porous substrate, so that the secondary battery has a higher energy density.

[0013] In some embodiments of the present application, the thickness of the adhesive layer is 2 μm to 6 μm. When the thickness of the adhesive layer is controlled within the above range, the probability of the adhesive layer falling off during the winding process is reduced, which is also conducive to reducing the energy density loss of the secondary battery caused by the excessive thickness of the adhesive layer, thereby making the secondary battery have a higher energy density.

[0014] In some embodiments of the present application, the secondary battery meets at least one of the following characteristics: (1) the ratio of the number of particles of the first inert substance to the second inert substance is 1:1 to 7:3; (2) 1 / 5≤D2 / D1≤1 / 3; (3) the mass ratio of the inert substance to the adhesive layer binder is 1:2 to 7:3; (4) the thickness of the porous substrate is 12 μm to 16 μm; (5) the thickness of the adhesive layer is 3 μm to 5 μm. This is conducive to making the secondary battery have good dynamic performance and safety performance, and high energy density.

[0015] In some embodiments of the present application, the inert material includes at least one of boehmite, diaspore, halloysite or quartz sand. The use of the above-mentioned inert materials is conducive to making the adhesive tape have better air permeability and higher strength.

[0016] In some embodiments of the present application, the adhesive layer binder includes at least one of polymethyl acrylate, polyacrylic acid, ethylene-acrylic acid copolymer, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyurethane or epoxy resin. Selecting the above-mentioned adhesive layer binder is conducive to making the adhesive layer have better bonding force and improving the bonding property of the adhesive tape.

[0017] In some embodiments of the present application, the positive electrode sheet includes a positive electrode active material layer and a positive electrode current collector, the positive electrode current collector includes a first surface and a second surface relative to each other, the positive electrode active material layer is at least arranged on the first surface of the positive electrode current collector, a first groove exposing the positive electrode current collector is arranged in the positive electrode active material layer, the positive electrode ear is arranged in the first groove and connected to the positive electrode current collector, and the second surface includes a first empty foil area relative to the first groove; the adhesive tape is attached to at least one of the positive electrode ear surface, the first empty foil area, the negative electrode sheet surface adjacent to the first groove, the negative electrode sheet surface adjacent to the first empty foil area, or the positive electrode sheet tailing area. Attaching the adhesive tape to the above-mentioned different positions can make the lithium ions in the area covered by the adhesive tape shuttle freely to exert the capacity of the active material, and can also reduce the risk of short circuit caused by contact between the positive and negative electrodes and the probability of lithium plating, so that the secondary battery has a higher energy density and good safety and kinetic performance.

[0018] In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer and a negative electrode tab, the negative electrode current collector includes a third surface and a fourth surface opposite to each other, the negative electrode active material layer is at least arranged on the third surface of the negative electrode current collector, a second groove exposing the negative electrode current collector is arranged in the negative electrode active material layer, the negative electrode tab is arranged in the second groove and connected to the negative electrode current collector, and the fourth surface includes a second empty foil area opposite to the second groove; and the adhesive tape is attached to at least one of the surface of the negative electrode tab or the second empty foil area. Attaching the adhesive tape to the surface of the negative electrode tab and the second empty foil area can embed lithium ions into the negative electrode active material layer covered by the adhesive tape, increase the lithium ion embedding sites, and increase the capacity of the negative electrode active material layer, so that the secondary battery has a higher energy density.

[0019] The second aspect of the present application provides an electronic device, which comprises the secondary battery described in any of the above embodiments. Therefore, the electronic device has good performance.

[0020] Beneficial effects of this application:

[0021] The present application provides a secondary battery and an electronic device. The secondary battery includes adhesive tape, a positive electrode sheet, a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode tab. The adhesive tape is between the separator and the positive electrode tab. The adhesive tape includes a porous substrate and an adhesive layer arranged on at least one surface of the porous substrate. The adhesive layer includes an inert substance. The inert substance includes a first inert substance and a second inert substance. The particle size of the first inert substance is d1 nm, the particle size of the second inert substance is d2 nm, and 300<d1≤900, 50≤d2≤300; the average particle size of the first inert substance is D1 nm, the average particle size of the second inert substance is D2 nm, and 400≤D1≤800, 100≤D2≤200; in any area on the surface of the adhesive layer, the particle number ratio of the first inert substance to the second inert substance is 3:7 to 7:3. The adhesive tape is provided with a first inert material with larger particles and a second inert material with smaller particles in the adhesive layer, and the ratio of the number of particles of the first inert material to the second inert material is adjusted to be within the above range, so that the first inert material with larger particles and the second inert material with smaller particles are matched, and the first inert material with larger particles can support the pore formation on the surface of the porous substrate to improve the air permeability of the porous substrate, thereby improving the air permeability of the adhesive tape, so as to reduce the probability of lithium precipitation in the adhesive tape pasting area, and the second inert material with smaller particles has a small pore formation, which can improve the adhesion of the adhesive layer, so as to reduce the probability of the adhesive layer falling off during the winding process of the adhesive tape. Thus, the dynamic performance of the secondary battery can be improved, and the processing performance of the secondary battery can also be improved. In addition, the adhesive tape of the present application has a high air permeability, and lithium ions can freely shuttle in the area where the adhesive tape is provided, so the capacity of the adhesive tape pasting area can still be exerted, thereby improving the energy density of the secondary battery.

[0022] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and a person skilled in the art can also obtain other embodiments based on these drawings.

[0024] Figure 1 Schematic diagram of the cross-sectional structure of the adhesive tape along its thickness direction and longitudinal direction according to some embodiments of the present application;

[0025] Figure 2 A schematic diagram of adhesive tape for a positive electrode tab in some embodiments of the present application;

[0026] Figure 3A schematic diagram of the position of the adhesive tape in some embodiments of the present application;

[0027] Figure 4 This is a schematic diagram of the position of adhesive tape in other embodiments of the present application.

[0028] 10-positive electrode plate; 11-positive electrode current collector; 12-positive electrode active material layer; 13-positive electrode ear; 11a-first surface; 11b-second surface; 15-first groove; 16-first empty foil area; 20-negative electrode plate; 21-negative electrode current collector; 22-negative electrode active material layer; 23-negative electrode ear; 25-second groove; 26-second empty foil area; 21c-third surface; 21d-fourth surface; 30-diaphragm; 40-adhesive paper; 41-porous substrate; 42-adhesive layer; 50-non-ion-conductive adhesive paper. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0030] It should be noted that in the specific implementation manner of the present application, the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0031] The first aspect of the present application provides a secondary battery, the secondary battery comprising adhesive tape, a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprising a positive electrode tab, the adhesive tape being between the separator and the positive electrode tab, the adhesive tape comprising a porous substrate and an adhesive layer disposed on at least one surface of the porous substrate. The adhesive layer comprises an inert substance, the inert substance comprises a first inert substance and a second inert substance, the particle size of the first inert substance is d1 nm, the particle size of the second inert substance is d2 nm, and 300<d1≤900, 50≤d2≤300. The average particle size of the first inert substance is D1 nm, the average particle size of the second inert substance is D2 nm, and 400≤D1≤800, 100≤D2≤200. In any area on the surface of the adhesive layer, the ratio of the number of particles of the first inert substance to the second inert substance is 3:7 to 7:3.

[0032] The above-mentioned "adhesive layer disposed on at least one surface of the porous substrate" means that the adhesive layer can be disposed on one surface of the porous substrate or on both surfaces of the porous substrate. For the convenience of understanding, the longitudinal direction of the adhesive tape itself is defined as X, the transverse direction of the adhesive tape itself is defined as Y, and the thickness of the adhesive tape itself is defined as Z. It should be understood that the above definition of direction is for the purpose of convenient description of this application, and the direction defined in this application can be understood based on the relative position of the attached drawings and the actual product elements. Figure 1 and Figure 2 As shown, when the adhesive tape 40 is attached to the positive electrode sheet 10, the longitudinal direction X of the adhesive tape 40 is parallel to the extension direction of the positive electrode tab 13, the transverse direction Y of the adhesive tape 40 is perpendicular to the extension direction of the positive electrode tab 13, and the thickness direction Z of the adhesive tape 40 is perpendicular to the transverse direction Y and the longitudinal direction X of the adhesive tape 40. In some embodiments, as Figure 1 As shown, the adhesive tape 40 includes a porous substrate 41 and an adhesive layer 42, and the adhesive layer 42 is disposed on one surface of the porous substrate 41. It can be understood that in other embodiments, the adhesive layer 42 can also be disposed on the other surface of the porous substrate 41. In some embodiments, the adhesive layer 42 can also be disposed on both surfaces of the porous substrate 41.

[0033] For example, d1 is 301, 320, 350, 370, 410, 430, 450, 470, 500, 533, 550, 570, 590, 610, 650, 700, 720, 750, 770, 790, 800, 810, 840, 870, 900 or any value between any two of the above numerical ranges. For example, d2 is 50, 71, 90, 105, 110, 130, 150, 173, 200, 220, 245, 260, 300 or any value between any two of the above numerical ranges. In the present application, the first inert material whose particle size d1 satisfies 300<d1≤900 is defined as a large particle inert material; the second inert material whose particle size d2 satisfies 50≤d2≤300 is defined as a small particle inert material. When the particle size d2 is less than 50, the particle size of the inert substance is too small, and the inert substance is easy to block the pores of the porous substrate, making the air permeability of the porous substrate worse, and the probability of the inert substance agglomerating itself or agglomerating with the adhesive layer adhesive will increase, thereby making the probability of lithium plating interface problems in the secondary battery in the later stage of the charge and discharge cycle too high; when the particle size d1 is greater than 900, the particle size of the inert substance is too large, which will reduce the adhesion of the adhesive layer, and the inert substance is easy to be filtered out during the slurry filtration process due to its large particle size, which will affect the content of the adhesive layer material components, increase the difficulty of the preparation process, and affect the ion conductivity and adhesion of the adhesive paper.

[0034] For example, D1 is 400, 415, 447, 472, 500, 530, 556, 581, 600, 610, 630, 653, 671, 700, 720, 740, 762, 788, 800 or any value between any two of the above value ranges. When D1 is less than 400, the average particle size of the first inert substance is too small, and the particle size of the first inert substance is too small as a whole. When used in combination with the second inert substance, the overall particle size of the inert substance is small, and there are fewer inert substance particles to support pore formation, or the pores of the inert substance are too small, making it difficult to improve the air permeability of the porous substrate, and the probability of reducing lithium precipitation in the adhesive tape area is too small; when D1 is greater than 800, the average particle size of the first inert substance is too large, and the particle size of the first inert substance is too large as a whole, which will reduce the adhesion of the adhesive layer and the inert substance is easily filtered out during the slurry filtration process due to its large particle size, which will affect the content of the material components of the adhesive layer, increase the difficulty of the preparation process, and affect the ion conductivity and adhesion of the adhesive tape.

[0035] For example, D2 is 100, 107, 115, 130, 140, 150, 162, 175, 180, 190, 200 or any value between any two of the above numerical ranges. When D2 is less than 100, the average particle size of the second inert substance is too small, the particle size of the second inert substance is too small as a whole, the second inert substance is easy to block the pores of the porous substrate, making the air permeability of the porous substrate worse, and the probability of the second inert substance agglomerating itself or agglomerating with the adhesive layer binder will increase, thereby making the probability of the secondary battery having a lithium deposition interface problem in the later stage of the charge and discharge cycle too high; when D2 is greater than 200, the average particle size of the second inert substance is too large, the particle size of the second inert substance is too large as a whole, which will affect the improvement of the adhesion of the second inert substance to the adhesive layer, thereby increasing the probability of the adhesive layer falling off during the winding process of the adhesive paper.

[0036] For example, the ratio of the number of particles of the first inert substance to the second inert substance is 3:7, 4:7, 5:7, 6:7, 1:1, 7:6, 7:5, 7:4, 7:3 or any ratio between any two of the above ratio ranges. If the ratio of the number of particles of the first inert substance to the second inert substance is less than 3:7, the number of particles of the first inert substance is too small, the number of large particles of inert substance used to support pore formation is too small, the air permeability of the adhesive tape is too poor, and the number of the second inert substance is too large. In addition to improving the adhesion of the adhesive layer, the extra small particles of inert substance are easy to block the pores of the porous substrate, the air permeability of the adhesive tape becomes poor, and the small particles of inert substance are difficult to disperse and easy to agglomerate, which makes the probability of point-like lithium deposition interface problems in the secondary battery during the charge and discharge cycle too high; The ratio of the number of particles of the two inert substances is greater than 7:3, the number of particles of the second inert substance is too small, the number of small-particle inert substances used to improve the adhesion of the adhesive layer is too small, the adhesion of the adhesive layer is too poor, and the probability of the adhesive layer falling off during the winding process of the adhesive paper is too high. The number of particles of the first inert substance is too large, the large-particle inert substance has a small specific surface area, and the adhesion to the porous substrate is reduced, resulting in poor adhesion between the porous substrate and the adhesive layer, the probability of the adhesive layer falling off during the winding process of the adhesive paper is too high, or the probability of local lithium deposition on the interface during the charge and discharge cycle of the secondary battery is too high.

[0037] In general, the adhesive tape in the secondary battery of the present application, by simultaneously adding a first inert substance with larger particles and a second inert substance with smaller particles in the adhesive layer, and regulating the average particle size of the first inert substance and the second inert substance, and the ratio of the number of particles of the first inert substance and the second inert substance within the scope of the present application, the first inert substance with larger particles and the second inert substance with smaller particles are matched, and the first inert substance with larger particles can support the pore formation on the surface of the porous substrate to improve the air permeability of the porous substrate, thereby improving the air permeability of the adhesive tape, so as to reduce the probability of lithium precipitation in the adhesive tape pasting area, and the second inert substance with smaller particles has a small pore formation pore, which can improve the adhesion of the adhesive layer, so as to reduce the probability of the adhesive layer falling off during the winding process of the adhesive tape. Thus, the dynamic performance of the secondary battery can be improved, and the processing performance of the secondary battery can also be improved. In addition, the adhesive tape of the present application has a high air permeability, and lithium ions can freely shuttle in the area where the adhesive tape is provided, so the capacity of the adhesive tape pasting area can still be exerted, thereby improving the energy density of the secondary battery.

[0038] In the present application, particle size refers to a single particle size of a single particle, which can also be understood as an equivalent particle size. The average particle size refers to the average particle size obtained by selecting several arbitrary areas on the surface of the adhesive layer, measuring the particle size of the inert material particles in the area, and then calculating the average value. The above-mentioned "several" can be one or more than two. The present application does not have any special restrictions on the area size of the above-mentioned "any area", and those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.

[0039] The present application has no particular restrictions on the method for regulating the particle size of the inert substance, as long as the purpose of the present application can be achieved. For example, it can be achieved by crushing and screening. The present application has no particular restrictions on the method for regulating the average particle size of the inert substance, as long as the purpose of the present application can be achieved. For example, after the film is prepared by the process of the present application, its average particle size can be tested by combining a scanning electron microscope, and the inert substance particles of the desired particle size can be selected. When testing the average particle size of the particles, 50 particles are selected to test the average value of the maximum circumscribed circle diameter of their outer contour as the average particle size of the particles.

[0040] It is understandable that the particle size of the inert substance defined in the present application is the main particle size, and within the allowable error range, the number of particles with a particle size exceeding 900 nm and less than 50 nm accounts for no more than 5% of the total number of inert substance particles.

[0041] In some embodiments of the present application, the ratio of the number of particles of the first inert substance to the second inert substance is 1:1 to 7:3. For example, the ratio of the number of particles of the first inert substance to the second inert substance is 1:1, 7:6, 7:5, 7:4, 7:3 or any ratio between any two of the above ratio ranges. The ratio of the number of particles of the first inert substance to the second inert substance is regulated within the above range, and the first inert substance and the second inert substance cooperate with each other, which can support the pore formation on the surface of the porous substrate to improve the air permeability of the adhesive tape, and can also make the inert substance have a higher adhesion to the surface of the porous substrate, and improve the adhesion between the porous substrate and the adhesive layer. In this way, the probability of lithium precipitation in the adhesive tape area in the late stage of the secondary battery charge and discharge cycle can be reduced, so that the secondary battery has good dynamic performance, and the probability of the adhesive layer falling off during the winding process of the adhesive tape is also reduced. In addition, lithium ions can shuttle freely in the area where the adhesive tape is provided, so the capacity of the adhesive tape area can still be exerted, thereby improving the energy density of the secondary battery.

[0042] The present application has no particular restrictions on the method for controlling the particle number ratio of the first inert substance to the second inert substance, as long as the purpose of the present application can be achieved. For example, the first inert substance and the second inert substance can be obtained by crushing and screening, and then the first inert substance and the second inert substance having the corresponding particle number ratio can be mixed according to actual needs.

[0043] In some embodiments of the present application, 1 / 7≤D2 / D1≤1 / 3. For example, the value of D1 / D2 is 1 / 7, 1 / 6, 1 / 5, 1 / 4, 1 / 3.7, 1 / 3.5, 1 / 3.2, 1 / 3 or any value between any two of the above numerical ranges. The value of the ratio D2 / D1 between the average particle size of the second inert substance and the average particle size of the first inert substance is regulated within the above range, and the large-particle inert substance and the small-particle inert substance are matched, which is beneficial to the surface of the porous substrate to support the pores to improve the air permeability of the adhesive tape, and is also beneficial to improve the adhesion of the inert substance to the surface of the porous substrate, so that the bonding force between the porous substrate and the adhesive layer is improved. In this way, the probability of lithium precipitation in the adhesive tape area in the later stage of the secondary battery charge and discharge cycle can be reduced so that the secondary battery has good dynamic performance, and the probability of the adhesive tape falling off during the winding process is also reduced. In addition, lithium ions can shuttle freely in the area where the adhesive tape is provided, so the capacity of the adhesive tape area can still be exerted, thereby improving the energy density of the secondary battery.

[0044] In some embodiments of the present application, 1 / 5≤D2 / D1≤1 / 3. For example, the value of D1 / D2 is 1 / 5, 1 / 4.5, 1 / 4, 1 / 3.7, 1 / 3.5, 1 / 3.2, 1 / 3 or any value between any two of the above numerical ranges. The value of the ratio D2 / D1 between the average particle size of the second inert substance and the average particle size of the first inert substance is regulated within the above range, and the large-particle inert substance and the small-particle inert substance are matched, which is more conducive to the porous substrate surface supporting pore formation to improve the air permeability of the adhesive tape, and is also more conducive to improving the adhesion of the inert substance to the porous substrate surface, so that the bonding force between the porous substrate and the adhesive layer is improved, so that the probability of lithium precipitation in the adhesive tape area in the later stage of the secondary battery charge and discharge cycle can be reduced so that the secondary battery has good dynamic performance, and the probability of the adhesive tape falling off during the winding process is also reduced. In addition, lithium ions can shuttle freely in the area where the adhesive tape is provided, so the capacity of the adhesive tape area can still be exerted, thereby improving the energy density of the secondary battery.

[0045] In some embodiments of the present application, the average pore size of the porous substrate is P nm; D2 and P satisfy the following relationship: 0.5≤P / D2≤1. For example, the value of P / D2 is 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any value between any two of the above numerical ranges. By adjusting the value of the ratio P / D2 between the average pore size of the porous substrate and the average particle size of the second inert substance within the above range, the second inert substance can have a higher adhesion to the porous substrate, and the probability of small particles of inert substance falling into the pores of the porous substrate is also reduced, so that the adhesive layer and the porous substrate have a better adhesion and the adhesive tape has a higher air permeability. In this way, the probability of the adhesive layer falling off during the winding process is low, and the probability of lithium precipitation in the adhesive tape area in the later stage of the secondary battery charge and discharge cycle is low, so that the secondary battery has good dynamic performance. Lithium ions can shuttle freely in the area where the adhesive tape is set, so the capacity of the adhesive tape area can still be exerted, thereby improving the energy density of the secondary battery.

[0046] In some embodiments of the present application, 50≤P≤200. For example, P is 50, 60, 80, 100, 120, 130, 140, 150, 162, 170, 180, 190, 200 or any value between any two of the above numerical ranges. The average pore size of the porous substrate is regulated within the above range, and the porous substrate has a suitable average pore size, which is conducive to a good adhesion between the adhesive layer and the porous substrate, and the adhesive tape has a high air permeability. In this way, the probability of the adhesive layer falling off during the winding process of the adhesive tape is low, and the probability of lithium precipitation in the adhesive tape area in the later stage of the secondary battery charge and discharge cycle is small so that the secondary battery has good dynamic performance. Lithium ions can shuttle freely in the area where the adhesive tape is provided, so the capacity of the adhesive tape area can still be exerted, thereby improving the energy density of the secondary battery.

[0047] The present application has no particular limitation on the method for adjusting the average pore size of the porous substrate, as long as the purpose of the present application can be achieved. For example, it can be achieved by adjusting the bidirectional (transverse and longitudinal) stretching ratio during the preparation of the porous substrate.

[0048] In some embodiments of the present application, the adhesive layer includes an adhesive layer binder, and the mass ratio of the inert substance to the adhesive layer binder is 3:7 to 7:3. For example, the mass ratio of the inert substance to the adhesive layer binder is 3:7, 4:7, 5:7, 6:7, 1:1, 7:6, 7:5, 7:4, 7:3 or any ratio between any two of the above ratio ranges. Regulating the mass ratio of the inert substance to the adhesive layer binder within the above range is conducive to making the adhesive tape have a higher air permeability and adhesion, so that the probability of the adhesive layer falling off during the winding process of the adhesive tape is low, and the probability of lithium precipitation in the adhesive tape area in the later stage of the secondary battery charge and discharge cycle is small so that the secondary battery has good kinetic performance. Lithium ions can shuttle freely in the area where the adhesive tape is provided, so the capacity of the adhesive tape area can still be exerted, thereby improving the energy density of the secondary battery.

[0049] In some embodiments of the present application, the mass ratio of the inert substance to the adhesive layer binder is 1:2 to 7:3. For example, the mass ratio of the inert substance to the adhesive layer binder is 1:2, 1:1, 7:6, 7:5, 7:4, 7:3 or any ratio between any two of the above ratio ranges. Regulating the mass ratio of the inert substance to the adhesive layer binder within the above range is conducive to further improving the air permeability and adhesion of the adhesive tape. Thereby further reducing the probability of the adhesive layer falling off during the winding process of the adhesive tape, and further reducing the probability of lithium precipitation in the adhesive tape area in the later stage of the secondary battery charge and discharge cycle so that the secondary battery has better dynamic performance.

[0050] In some embodiments of the present application, the air permeability of the adhesive tape is 180s / 100mL to 600s / 100mL. For example, the air permeability of the adhesive tape is 180s / 100mL, 200s / 100mL, 220s / 100mL, 240s / 100mL, 260s / 100mL, 280s / 100mL, 3200s / 100mL, 380s / 100mL, 400s / 100mL, 420s / 100mL, 452s / 100mL, 480s / 100mL, 512s / 100mL, 530s / 100mL, 550s / 100mL, 573s / 100mL, 600s / 100mL, or any value between any two of the above ranges. Controlling the air permeability of the adhesive tape within the above range is beneficial to reducing the probability of lithium plating in the adhesive tape-attached area in the later stage of the secondary battery charge and discharge cycle so that the secondary battery has good dynamic performance.

[0051] The present application does not particularly limit the method for regulating the air permeability of the adhesive tape, as long as the purpose of the present application can be achieved. For example, it can be achieved by regulating at least one of the mass ratio of the inert substance in the adhesive layer and the adhesive of the adhesive layer, the porosity of the porous substrate, or the average pore size of the porous substrate. Generally speaking, the more inert substances in the adhesive layer, the better the air permeability of the adhesive tape (the smaller the air permeability value); the less inert substances in the adhesive layer, the worse the air permeability of the adhesive tape (the larger the air permeability value). The greater the porosity of the porous substrate, the better the air permeability of the adhesive tape; the smaller the porosity of the porous substrate, the worse the air permeability of the adhesive tape. The larger the average pore size of the porous substrate, the better the air permeability of the adhesive tape; the smaller the average pore size of the porous substrate, the worse the air permeability of the adhesive tape.

[0052] In some embodiments of the present application, the porosity of the porous substrate is 25% to 55%. For example, the porosity of the porous substrate is 25%, 30%, 34%, 40%, 45%, 50%, 55% or any value between any two of the above ranges. Regulating the porosity of the porous substrate within the above range is conducive to making the porous substrate have better air permeability on the basis of higher strength, and then the adhesive tape has better air permeability, the probability of interface lithium precipitation in the secondary battery during the charge and discharge cycle is small, and the secondary battery has good dynamic performance.

[0053] The present application has no particular restrictions on the manner of regulating the porosity of the porous substrate, as long as the purpose of the present application can be achieved. For example, it can be achieved by regulating the biaxial stretching ratio during the preparation of the porous substrate.

[0054] In some embodiments of the present application, the thickness of the porous substrate is 9 μm to 24 μm. For example, the thickness of the porous substrate is 9 μm, 12 μm, 14 μm, 17 μm, 20 μm, 21 μm, 22 μm, 24 μm, or any value between any two of the above ranges. Figure 1 As shown, the thickness of the porous substrate 41 is T 41 As shown. When the thickness of the porous substrate is controlled within the above range, the porous substrate has sufficient tensile strength. When the adhesive layer slurry is coated on the surface of the porous substrate, the flow of the adhesive layer slurry can be slowed down to reduce the probability of the adhesive layer slurry agglomerating and causing the adhesive layer to be uneven, thereby reducing the probability of local impedance becoming larger, reducing the occurrence of lithium precipitation at the interface of the secondary battery during charge and discharge cycles, and improving the dynamic performance of the secondary battery. It can also reduce the energy density loss of the secondary battery caused by the excessive thickness of the porous substrate, so that the secondary battery has a higher energy density.

[0055] In some embodiments of the present application, the thickness of the porous substrate is 12 μm to 16 μm. For example, the thickness of the porous substrate is 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, or any value between any two of the above ranges. Figure 1 As shown, the thickness of the porous substrate 41 is T 41 The thickness of the porous substrate is controlled within the above range, which is beneficial to further reduce the probability of the glue layer being uneven due to the agglomeration of the glue material, and is also beneficial to further reduce the energy density loss of the secondary battery caused by the excessive thickness of the porous substrate. Thus, the secondary battery has good dynamic performance and high energy density.

[0056] The present application has no particular restrictions on the material of the porous substrate, as long as the purpose of the present application can be achieved. For example, the material of the porous substrate includes but is not limited to at least one of polypropylene, low-density polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose film or non-woven fabric.

[0057] In some embodiments of the present application, the thickness of the glue layer is 2 μm to 6 μm. For example, the thickness of the glue layer is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or any value between any two of the above ranges. Figure 1 As shown, the thickness of the adhesive layer 42 is T 42 Controlling the thickness of the adhesive layer within the above range is conducive to making the adhesive tape have good adhesion, reducing the probability of the adhesive layer falling off during the winding process, and also helping to reduce the energy density loss of the secondary battery caused by the excessive thickness of the adhesive layer, thereby making the secondary battery have a higher energy density.

[0058] In some embodiments of the present application, the thickness of the adhesive layer is 3 μm to 5 μm. For example, the thickness of the adhesive layer is 3 μm, 4 μm, 5 μm, or any value between any two of the above ranges. Figure 1 As shown, the thickness of the adhesive layer 42 is T 42 Controlling the thickness of the adhesive layer within the above range is conducive to making the adhesive tape have good adhesion, reducing the probability of the adhesive layer falling off during the winding process, and also helping to reduce the energy density loss of the secondary battery caused by the excessive thickness of the adhesive layer, thereby making the secondary battery have a higher energy density.

[0059] The present application has no particular limitation on the thickness of the adhesive tape, as long as the purpose of the present application can be achieved. For example, the thickness of the adhesive tape is 11 μm to 36 μm.

[0060] In some embodiments of the present application, the inert material includes at least one of boehmite, diaspore, halloysite or quartz sand. In some embodiments, the first inert material and the second inert material each independently include at least one of boehmite, diaspore, halloysite or quartz sand. In some embodiments, the first inert material and the second inert material are of the same type. In other embodiments, the first inert material and the second inert material are of different types. The selection of the above-mentioned types of inert materials is conducive to making the adhesive tape have better air permeability and also makes the adhesive tape have higher strength. In this way, the probability of interfacial lithium precipitation in the secondary battery during the charge and discharge cycle is reduced, so that the secondary battery has good dynamic performance. The probability of the adhesive tape being punctured by particles or burrs on the surface of the positive electrode sheet or the negative electrode sheet is small, so that the secondary battery has good safety performance.

[0061] In some embodiments of the present application, the adhesive layer binder includes at least one of polymethyl acrylate, polyacrylic acid (PAA), ethylene-acrylic acid copolymer (EAA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide (PI), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), polyurethane or epoxy resin. Selecting the above-mentioned adhesive layer binder is conducive to making the adhesive layer have better bonding force and improving the bonding property of the adhesive tape.

[0062] The present application has no particular limitation on the weight average molecular weight of the adhesive layer adhesive, as long as the purpose of the present application can be achieved.

[0063] For ease of understanding, it is defined that when the positive electrode sheet is unfolded, the length direction of the positive electrode sheet itself is the same as the transverse direction Y of the adhesive tape, the width direction of the positive electrode sheet itself is the same as the longitudinal direction X of the adhesive tape, and the thickness direction of the positive electrode sheet itself is the same as the thickness direction Z of the adhesive tape. It can be understood that when the positive electrode sheet, the negative electrode sheet and the separator are unfolded, the length direction, width direction and thickness direction of the positive current collector, the positive active material layer, the negative electrode sheet and the separator are the same as those of the positive electrode sheet.

[0064] In some embodiments of the present application, the positive electrode sheet includes a positive electrode active material layer and a positive electrode current collector, the positive electrode current collector includes a first surface and a second surface opposite to each other, the positive electrode active material layer is at least arranged on the first surface of the positive electrode current collector, a first groove exposing the positive electrode current collector is arranged in the positive electrode active material layer, the positive electrode tab is arranged in the first groove and connected to the positive electrode current collector, and the second surface includes a first empty foil area opposite to the first groove; the adhesive tape is attached to at least one of the positive electrode tab surface, the first empty foil area, the negative electrode sheet surface adjacent to the first groove, the negative electrode sheet surface adjacent to the first empty foil area, or the positive electrode sheet tailing area. The above-mentioned "the positive electrode active material layer is at least arranged on the first surface of the positive electrode current collector" means that in some embodiments, the positive electrode active material layer is arranged on the first surface of the positive electrode current collector, and in other embodiments, the positive electrode active material layer is arranged on the first surface and the second surface of the positive electrode current collector at the same time. "The first surface" and "the second surface" may be partial or all surfaces of the positive electrode current collector. It should be noted that the negative electrode sheet in the "negative electrode sheet surface adjacent to the first groove" and the negative electrode sheet in the "negative electrode sheet surface adjacent to the first empty foil area" are not the same layer of negative electrode sheets, but two layers of negative electrode sheets adjacent to the positive electrode sheets. The above-mentioned "two layers of negative electrode sheets" can be two negative electrode sheets, or two layers formed by winding a negative electrode sheet. Figure 3As shown, the separator 30 is located between the positive electrode sheet 10 and the negative electrode sheet 20. The positive electrode sheet 10 includes a positive electrode collector 11, a positive electrode active material layer 12 and a positive electrode tab 13. The positive electrode collector 11 includes a first surface 11a and a second surface 11b opposite to each other along its thickness direction Z. The positive electrode active material layer 12 is arranged on the first surface 11a of the positive electrode collector 11, and is also arranged on the second surface 11b of the positive electrode collector 11. The positive electrode active material layer 12 arranged on the first surface 11a is provided with a first groove 15 exposing the positive electrode collector 11. The positive electrode tab 13 is arranged in the first groove 15 and connected to the positive electrode collector 11. The second surface 11b includes a first empty foil area 16 opposite to the first groove 15. The adhesive tape 40 is respectively attached to the surface of the positive electrode tab 13, the first empty foil area 16, the surface of the negative electrode sheet 20 adjacent to the first groove 15, the surface of the negative electrode sheet 20 adjacent to the first empty foil area 16, and the tail area of ​​the positive electrode sheet 10. Generally, along the length direction Y of the positive electrode sheet 10, the length of the adhesive tape 40 attached to the surface of the positive electrode tab 13 and the first empty foil area 16 is greater than the length of the adhesive tape 40 attached to the surface of the negative electrode sheet 20 adjacent to the first groove 15 and the surface of the negative electrode sheet 20 adjacent to the first empty foil area 16. By sticking the adhesive tape on the surface of the positive electrode ear and the surface of the negative electrode sheet adjacent to the first groove, the probability of the burrs of the positive electrode ear penetrating the negative electrode active material layer and contacting the negative electrode collector to cause a short circuit can be reduced. In the area where the adhesive tape stuck on the surface of the positive electrode ear covers the positive electrode active material layer, lithium ions can be normally released, and the lithium ions after release can also be normally embedded in the relative negative electrode active material layer, thereby reducing the waste of capacity and the probability of lithium precipitation. By sticking the adhesive tape on the first empty foil area and the surface of the negative electrode sheet adjacent to the first empty foil area, the probability of the burrs in the first empty foil area penetrating the negative electrode active material layer and contacting the negative electrode collector to cause a short circuit can be reduced. In the area where the adhesive tape stuck on the first empty foil area covers the positive electrode active material layer, lithium ions can be normally released, and the lithium ions after release can also be normally embedded in the relative negative electrode active material layer, thereby reducing the waste of capacity and the probability of lithium precipitation. By sticking the adhesive tape on the tailing area of ​​the positive electrode sheet, the probability of the positive electrode collector contacting the negative electrode sheet can be reduced. Therefore, sticking the tape at the above-mentioned different positions can enable the lithium ions in the area covered by the tape to shuttle freely to exert the capacity of the active material, and can also reduce the risk of short circuit caused by contact between the positive and negative electrodes and the probability of lithium plating, so that the secondary battery has a higher energy density and good safety and dynamic performance.

[0065] In some embodiments of the present application, the negative electrode plate includes a negative electrode collector, a negative electrode active material layer and a negative electrode tab. The negative electrode collector includes a third surface and a fourth surface relative to each other. The negative electrode active material layer is at least arranged on the third surface of the negative electrode collector. A second groove exposing the negative electrode collector is arranged in the negative electrode active material layer. The negative electrode tab is arranged in the second groove and connected to the negative electrode collector. The fourth surface includes a second empty foil area relative to the second groove. The adhesive tape is attached to the surface of the negative electrode tab or at least one of the second empty foil areas. The above-mentioned "the negative electrode active material layer is at least arranged on the third surface of the negative electrode collector" means that, in some embodiments, the negative electrode active material layer is arranged on the third surface of the negative electrode collector. In other embodiments, the negative electrode active material layer is simultaneously arranged on the third surface and the fourth surface of the negative electrode collector. Figure 4 As shown, the separator 30 is located between the positive electrode sheet 10 and the negative electrode sheet 20. The negative electrode sheet 20 includes a negative electrode current collector 21, a negative electrode active material layer 22 and a negative electrode tab 23. The negative electrode current collector 21 includes a third surface 21c and a fourth surface 21d opposite to each other along its thickness direction Z. The negative electrode active material layer 22 is arranged on the third surface 21c and the fourth surface 21d of the negative electrode current collector 21. A second groove 25 exposing the negative electrode current collector 21 is arranged in the negative electrode active material layer 22 located on the third surface 21c. The negative electrode tab 23 is arranged in the second groove 25 and connected to the negative electrode current collector 21. The fourth surface 21d includes a second empty foil area 26 opposite to the second groove 25. The adhesive tape 40 is attached to the surface of the negative electrode tab 23 and the second empty foil area 26. The surface of the positive electrode sheet 10 adjacent to the second groove 25 and the surface of the positive electrode sheet 10 adjacent to the second empty foil area 26 are attached with non-ion conductive adhesive tape 50. Sticking the adhesive tape to the surface of the negative electrode tab and the second empty foil area can embed lithium ions into the negative electrode active material layer covered by the adhesive tape, increase the lithium ion embedding sites, and increase the capacity of the negative electrode active material layer, thereby making the secondary battery have a higher energy density.

[0066] The present application has no particular limitation on the type of non-ion-conducting adhesive tape, and any non-ion-conducting adhesive tape known in the art may be selected as needed, as long as the purpose of the present application can be achieved.

[0067] The present application has no particular restrictions on the material of the positive electrode tab, as long as the purpose of the present application can be achieved. For example, the material of the positive electrode tab includes at least one of aluminum (Al) or an aluminum alloy. The present application has no particular restrictions on the material of the negative electrode tab, as long as the purpose of the present application can be achieved. For example, the material of the negative electrode tab includes at least one of nickel (Ni), copper (Cu) or copper-plated nickel (Ni-Cu).

[0068] The present application has no particular restrictions on the type of positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the positive electrode current collector may include aluminum foil, aluminum alloy foil, etc. The present application has no particular restrictions on the positive electrode active material layer, as long as the purpose of the present application can be achieved. In one embodiment of the present application, the positive electrode active material layer includes a positive electrode active material. The present application has no particular restrictions on the type of positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, or lithium titanate. Optionally, the positive electrode active material layer also includes a positive electrode conductive agent and a positive electrode binder. The present application has no particular restrictions on the types of positive electrode conductive agents and positive electrode binders in the positive electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the mass ratio of positive electrode active materials, positive electrode conductive agents, and positive electrode binders in the positive electrode active material layer, and those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. The thickness of the positive electrode current collector and the positive electrode active material layer is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, and the thickness of the positive electrode active material layer is 30 μm to 120 μm.

[0069] The present application has no particular restrictions on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the negative electrode current collector may include copper foil, copper alloy foil, nickel foil, titanium foil, nickel foam or copper foam, etc. The present application has no particular restrictions on the negative electrode active material layer, as long as the purpose of the present application can be achieved. In one embodiment of the present application, the negative electrode active material layer includes a negative electrode active material. The present application has no particular restrictions on the type of negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, tin-based materials, silicon-based materials, lithium titanate, transition metal nitrides or natural flake graphite. Optionally, the negative electrode active material layer also includes at least one of a negative electrode conductive agent, a thickener, and a negative electrode binder. The present application has no particular restrictions on the types of negative electrode conductive agents, thickeners and negative electrode binders in the negative electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the mass ratio of the negative electrode active material, the negative electrode conductive agent, the thickener and the negative electrode binder in the negative electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 5 μm to 20 μm, and the thickness of the negative electrode active material layer is 30 μm to 120 μm.

[0070] The present application has no particular restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include, but is not limited to, polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) films), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of diaphragm may include at least one of a woven membrane, a nonwoven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0071] The secondary battery of the present application also includes a packaging bag and an electrolyte, and the glue layer, the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte are contained in the packaging bag. The present application has no special restrictions on the packaging bag and the electrolyte, and the packaging bag and the electrolyte known in the present application can be selected according to actual needs, as long as the purpose of the present application can be achieved.

[0072] The present application does not particularly limit the type of secondary battery, which may include any device that undergoes an electrochemical reaction. For example, the secondary battery may include, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a sodium ion secondary battery (sodium ion battery), a lithium polymer secondary battery, and a lithium ion polymer secondary battery.

[0073] The present application has no particular restrictions on the preparation method of the adhesive layer, as long as the purpose of the present application can be achieved. For example, the preparation method of the adhesive layer includes but is not limited to the following steps: (1) After mixing the inert substance and the adhesive layer binder, a solvent is added and stirred to obtain an adhesive layer slurry; (2) The adhesive layer slurry is coated on the surface of the release film by a micro-concave roller, and the slurry forms a film and shrinks during the drying process, and finally a porous adhesive layer is formed. After the adhesive layer is composited with the porous substrate, a release agent is set on the surface of the porous substrate away from the adhesive layer, and the adhesive layer is obtained after drying, and is rolled up, cut, and used. The present application has no particular restrictions on the solid content of the adhesive layer slurry, as long as the purpose of the present application can be achieved. For example, the solid content of the adhesive layer slurry is 10wt% to 30wt%. The present application has no particular restrictions on the type of the above-mentioned "solvent", as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the drying and drying temperature in the above-mentioned step (2), as long as the purpose of the present application can be achieved. The present application has no particular limitation on the release film and release agent, and those skilled in the art may select known release films and release agents according to actual conditions, as long as the purpose of the present application can be achieved.

[0074] The present application does not particularly limit the preparation method of the secondary battery, and the preparation method known in the art can be selected as long as the purpose of the present application can be achieved. For example, the preparation method of the secondary battery includes but is not limited to the following steps: stacking the diaphragm, the positive electrode sheet, the diaphragm and the negative electrode sheet in order, and after pasting the adhesive tape, winding, folding and other operations as needed to obtain an electrode assembly of a winding structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the diaphragm, the positive electrode sheet, the diaphragm and the negative electrode sheet in order, and after pasting the adhesive tape, fixing the four corners of the entire laminated structure to obtain an electrode assembly of a laminated structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery.

[0075] The second aspect of the present application provides an electronic device, which comprises the secondary battery described in any of the above embodiments. Therefore, the electronic device has good performance.

[0076] The electronic devices of the present application are not particularly limited, and may include but are not limited to the following types: laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0077] Example

[0078] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods.

[0079] Test methods and equipment:

[0080] Methods for extracting porous substrates from lithium-ion batteries:

[0081] Disassemble the lithium-ion battery in an environment with room temperature and humidity less than 20%, separate the positive electrode, separator and negative electrode, and tear off the adhesive tape with tweezers. If the adhesive tape is located between the negative electrode and the separator, tear off the adhesive tape and place it in a mixed solvent of toluene and ethyl acetate (toluene and ethyl acetate mass ratio 7:3) and water in turn, stir at 50°C for 20 minutes, take it out, and dry it at 100°C for 2 hours until there is no solution, so as to obtain a porous substrate; if the adhesive tape is located between the positive electrode and the separator, tear off the adhesive tape and place it in N-methylpyrrolidone (NMP), stir at 50°C for 20 minutes, take it out, and dry it at 100°C for 2 hours until there is no solution, so as to obtain a porous substrate.

[0082] Thickness test:

[0083] (1) Tape thickness T 40 The test:

[0084] Take out the positive and negative electrodes from the lithium-ion battery and use a micrometer to measure the thickness T of the electrodes where the adhesive tape is attached. 总 and the thickness T where the adhesive tape is not applied 极片 , tape thickness T 40 =T 总 -T 极片 .

[0085] (2) Thickness of porous substrate T 41 The test:

[0086] Use a screw micrometer to randomly measure the thickness of the porous substrate sample at 6 locations, calculate the average value, and obtain the thickness T of the porous substrate. 41 .

[0087] (3) Adhesive layer thickness T 42 The test:

[0088] According to the above-mentioned tape thickness T 40 and the thickness of the porous substrate T 41 Calculate the thickness of the adhesive layer T 42 :T 42 =T 40 -T 41 .

[0089] Test of average pore size of porous substrates:

[0090] Take a sample of a porous substrate and take a scanning electron microscope (SEM) image at an accelerating voltage (EHT) of 3 kV and a magnification of 10,000 times. Using imageJ software, randomly select 5 different areas of 10 μm × 10 μm to measure the pore size, and take the average value as the median pore size, that is, the average pore size.

[0091] Tests for particle size, average particle size and ratio of inert material particles:

[0092] Take the adhesive tape sample, take the SEM image of the adhesive layer at EHT = 3kV and magnification 10000 times. Use imageJ software to randomly select 5 different areas of 10μm×10μm to count the number of large and small particles, and get the ratio of the number of particles of the first inert substance and the second inert substance; at the same time, select 50 large particles of inert substance and 50 small particles of inert substance, test the maximum circumscribed circle diameter of their outer contours, and take the average value as the average particle size of the particles.

[0093] Test of air permeability of adhesive tape:

[0094] Cut the adhesive tape sample to a size of 50mm×50mm, place it on the air permeability tester, press the start button, the test will be completed after five seconds, and the air permeability value will be automatically displayed; repeat the experiment 5 times for each sample, and take the average value as the air permeability of the adhesive tape of this application.

[0095] Porosity test of porous substrates:

[0096] The porosity of the porous substrate is calculated using the following formula: φ = [1-m (s × h × ρ)] × 100%, where m is the mass of the porous substrate sample, s is the area of ​​the porous substrate sample, h is the thickness of the porous substrate sample, and ρ is the density of the porous substrate material.

[0097] Lithium extraction test:

[0098] The lithium-ion battery was directly charged at a low temperature (12°C) at a rate of 1.5C to a set voltage of 4.45V, and discharged at 1.5C to 3V. After 10 cycles, the lithium-ion battery was disassembled to observe whether silvery white lithium metal appeared on the surface of the electrode where the tape was attached to the surface of the positive electrode tab. Calculated based on the total area of ​​the tape plane, a lithium deposition area of ​​less than 1% indicates no lithium deposition, a lithium deposition area of ​​1% to 5% indicates slight lithium deposition, a lithium deposition area of ​​more than 5% to 10% indicates moderate lithium deposition, and a lithium deposition area of ​​more than 10% indicates severe lithium deposition.

[0099] The degree of lithium deposition is used to characterize the kinetic performance of lithium-ion batteries. The more severe the degree of lithium deposition (i.e., the larger the lithium deposition area), the worse the kinetic performance of the lithium-ion battery; the lighter the degree of lithium deposition (i.e., the smaller the lithium deposition area), the better the kinetic performance of the lithium-ion battery.

[0100] Energy density (ED) test:

[0101] Taking the labeling on the outer packaging of lithium-ion batteries as an example, when the voltage range marked on the outer packaging of the battery is 3.0V to 4.45V, the charging cut-off voltage is 4.45V and the discharging cut-off voltage is 3.0V.

[0102] Under 25°C environment, both the comparative example and the embodiment adopt 0.2C direct charging to 4.45V, 4.45V constant voltage charging to 0.025C full charging, and then discharge to 3.0V with 0.2C current after full charging. The above process is repeated 3 times, and the average capacity is taken as the actual capacity.

[0103] ED = actual capacity × discharge platform / (volume of lithium-ion battery).

[0104] Adhesion test:

[0105] The adhesion between the adhesive tape and the negative electrode sheet was tested by 180° peeling. Take adhesive tape and negative electrode sheet with a length of 100mm to 300mm, and punch the negative electrode sheet and adhesive tape into samples with a specification of 54.2mm×72.5mm; stack the punched adhesive tape and negative electrode sheet neatly, put the stacked sample into the flat press and adjust the pressure to 2kg to compound the adhesive tape and negative electrode sheet to obtain the sample; use the knife die and punching machine to punch the sample into small strips of 72.5mm×15mm, separate the adhesive tape from the negative electrode sheet, connect the sample with A4 paper with a width of 15mm, and stick wrinkle glue on both sides of the connection to complete the sample production; turn on the high-speed rail tensile machine, and set it in sequence: adhesion test, speed 50mm / min, starting fixture spacing 40mm; click "Start" to pre-stretch ~5mm; after pre-stretching, reset the force, displacement, etc. to zero again, start the test, and measure at least 5 samples in each group. The average value is taken as the final adhesion value.

[0106] The adhesive force is used to characterize the probability of the adhesive layer falling off during the winding process of the adhesive tape. The greater the adhesive force, the smaller the probability of the adhesive layer falling off during the winding process; the smaller the adhesive force, the greater the probability of the adhesive layer falling off during the winding process of the adhesive tape.

[0107] Example 1-1

[0108] <Preparation of adhesive tape>

[0109] After mixing the inert material boehmite and the adhesive layer binder polymethyl acrylate (weight average molecular weight Mw=86W), ethyl acetate is added as a solvent and stirred evenly to obtain an adhesive layer slurry with a solid content of 20wt%. Among them, the mass ratio of the inert material to the adhesive layer binder is 1:1, the inert material includes a first inert material with a particle size d1 satisfying 300<d1≤900 and a second inert material with a particle size d2 satisfying 50≤d2≤300, the average particle size D1 of the first inert material is 600nm, and the average particle size D2 of the second inert material is 140nm. The particle number ratio of the first inert material to the second inert material is 3:2.

[0110] The adhesive layer slurry is coated on the surface of a release film polyethylene terephthalate (PET) film with a release force of 10g by a micro-concave roller, and dried at 110°C to form a film with a thickness of T42 = 3 μm adhesive layer, and then the adhesive layer and the porous substrate (thickness T 41 =14μm, porosity 45% biaxially oriented polypropylene (BOPP film) (manufacturer: Dalian Eco Energy Technology Co., Ltd., model: ECO-9) composite, the adhesive layer is transferred to the surface of the porous substrate, and rolled up to obtain an intermediate product with a release film and a porous substrate; the porous substrate side (the opposite side of the adhesive layer) of the intermediate product is coated with a silicon release agent (manufacturer: Dow Corning) using a micro-concave roller, and after drying, the release film is removed while the porous substrate is rolled up to obtain a thickness T 40 =17μm adhesive tape.

[0111] <Preparation of positive electrode sheet>

[0112] The positive electrode active material lithium cobalt oxide, the positive electrode conductive agent conductive carbon black (Super P), and the positive electrode binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 95.5:2.5:2.0, and NMP is added as a solvent. Stirred under the action of a vacuum mixer until the solid content is 72wt% and the system is uniform. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 85°C to obtain a positive electrode sheet with a single-sided positive electrode active material layer (thickness 50μm). After that, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode active material layer. After cold pressing, cutting, and welding of the positive electrode aluminum tab, a positive electrode sheet with a specification of 70mm×1400mm is obtained for standby use.

[0113] <Preparation of negative electrode sheet>

[0114] The negative electrode active material artificial graphite, the negative electrode thickener sodium carboxymethyl cellulose, and the negative electrode binder styrene butadiene rubber are mixed in a mass ratio of 98.2:0.8:1.0, and then deionized water is added as a solvent, and stirred under the action of a vacuum mixer until the solid content is 42wt% and the system is uniform. The negative electrode slurry is evenly coated on one surface of the negative electrode current collector copper foil with a thickness of 8μm, and dried at 85°C to obtain a negative electrode sheet with a single-sided coating of a negative electrode active material layer (thickness 60μm). After that, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of a negative electrode active material layer. After cold pressing, cutting, and welding of the negative electrode tab nickel tab, a negative electrode sheet with a specification of 74mm×1408mm is obtained for standby use.

[0115] <Preparation of Separator>

[0116] The diaphragm base film is 8μm thick polyethylene (PE), and a 2μm thick alumina ceramic layer is coated on both surfaces of the diaphragm base film along its thickness direction. Finally, a 2.5mg / cm thick alumina ceramic layer is coated on both surfaces of the ceramic layer along its thickness direction.2 The binder PVDF is used and the diaphragm is obtained by drying.

[0117] <Preparation of Electrolyte>

[0118] In an environment with a water content of less than 10ppm, non-aqueous organic solvents propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are prepared into a basic electrolyte in a mass ratio of 1:1:0.5:1, and lithium hexafluorophosphate (LiPF6) is added and mixed evenly to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0119] <Preparation of lithium-ion batteries>

[0120] The negative electrode sheet, separator and positive electrode sheet prepared above are stacked and wound in sequence to obtain an electrode assembly with a wound structure. The electrode assembly is placed in an aluminum-plastic film packaging bag, and after drying, an electrolyte is injected, and a lithium-ion battery is obtained through vacuum packaging, standing, formation, capacity, degassing, trimming and other processes.

[0121] Among them, Figure 3 As shown, the surface of the positive electrode tab 13, the first empty foil area 16, the surface of the negative electrode sheet 20 adjacent to the first groove 15, the surface of the negative electrode sheet 20 adjacent to the first empty foil area 16, and the tail area of ​​the positive electrode sheet 10 are all affixed with adhesive tape 40; Figure 4 As shown, the surface of the negative electrode tab 23 and the second empty foil area 26 are affixed with adhesive tape 40, and the surface of the positive electrode sheet 10 adjacent to the second groove 25 and the surface of the positive electrode sheet 10 adjacent to the second empty foil area 26 are affixed with non-ion-conducting adhesive tape 50 (manufacturer: Todi Chemical (Shanghai) Co., Ltd., model: T4116BR).

[0122] Example 1-2 to Example 1-16

[0123] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0124] Example 2-1 to Example 2-11

[0125] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 1-1.

[0126] Example 3-1 to Example 3-16

[0127] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as Example 1-1.

[0128] Comparative Examples 1 to 8

[0129] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0130] The preparation parameters and performance data of each embodiment and comparative example are shown in Tables 1 to 3.

[0131] Table 1

[0132]

[0133]

[0134] Note: “\” in Table 1 indicates no corresponding parameter; “A” in Table 1 indicates the ratio of the number of particles of the first inert substance to the number of particles of the second inert substance.

[0135] It can be seen from Examples 1-1 to 1-13 and Comparative Examples 1 to 8 that the secondary battery of the embodiment of the present application, by selecting adhesive tape with larger particles of the first inert substance and smaller particles of the second inert substance added to the adhesive layer, and regulating the average particle size of the first inert substance and the second inert substance and the ratio of the number of particles of the first inert substance and the second inert substance within the scope of the present application, makes the interfacial lithium deposition of the secondary battery relatively mild and has a higher energy density, and the adhesive tape has a greater bonding force, indicating that the secondary battery of the embodiment of the present application can have both higher dynamic performance, energy density and lower probability of glue falling off during winding. In the secondary battery of the comparative example, only larger particles of the first inert substance or smaller particles of the second inert substance are added to the glue layer, and at least one of the average particle size of the first inert substance, the average particle size of the second inert substance, or the ratio of the number of particles of the first inert substance to the second inert substance is not within the scope of the present application. The interface lithium plating of the secondary battery of the comparative example is more serious, or the glue tape has lower adhesion, or the secondary battery has lower energy density, indicating that the secondary battery of the comparative example cannot have both higher dynamic performance, energy density and lower probability of glue falling off during winding.

[0136] The average particle size D1 of the first inert substance, the average particle size D2 of the second inert substance, and the value of the ratio D2 / D1 of the two usually affect the dynamic performance, energy density, and the probability of glue falling off during winding of the secondary battery. From Examples 1-1 to 1-10 and Comparative Examples 1 to 4, it can be seen that the secondary battery in which the average particle size D1 of the first inert substance, the average particle size D2 of the second inert substance, and the value of the ratio D2 / D1 of the two are within the scope of the present application has a relatively mild lithium precipitation at the interface, a relatively high energy density, and a relatively high adhesive force of the adhesive tape, indicating that the secondary battery can have good dynamic performance, a relatively high energy density, and a relatively low probability of glue falling off during winding.

[0137] The ratio of the number of particles of the first inert substance to the second inert substance usually affects the dynamic performance, energy density and probability of glue falling off during winding of the secondary battery. It can be seen from Example 1-1, Example 1-11 to Example 1-13, Comparative Example 5 and Comparative Example 6 that the secondary battery in which the ratio of the number of particles of the first inert substance to the second inert substance is within the scope of the present application has a relatively mild lithium precipitation on the interface, a relatively high energy density, and a relatively high adhesive force of the adhesive tape, indicating that the secondary battery can have good dynamic performance, a relatively high energy density and a relatively low probability of glue falling off during winding.

[0138] The average pore size P of the porous substrate and the ratio P / D2 between the average pore size of the porous substrate and the average particle size of the second inert substance usually affect the dynamic performance, energy density and winding glue falling probability of the secondary battery. It can be seen from Example 1-1, Example 1-5 to Example 1-7, Example 1-14 to Example 1-16 that the selection of the secondary battery whose average pore size P of the porous substrate and the ratio P / D2 between the average pore size of the porous substrate and the average particle size of the second inert substance are within the scope of the present application is conducive to controlling the specific surface area of ​​the porous substrate within a suitable range, increasing the adhesion ability of the particles to the porous substrate, and improving the bonding effect between the porous substrate and the glue layer. The lithium precipitation at the interface is relatively mild, the energy density is relatively high, and the adhesive force of the adhesive tape is relatively high, indicating that the secondary battery can take into account good dynamic performance, high energy density and low probability of winding glue falling.

[0139] Table 2

[0140]

[0141]

[0142] The mass ratio of the inert material and the adhesive layer binder usually affects the dynamic performance, energy density and the probability of adhesive peeling during winding of the secondary battery. It can be seen from Examples 1-1, 2-1 to 2-6 that the secondary battery using the inert material and the adhesive layer binder whose mass is within the scope of this application has a relatively mild lithium precipitation at the interface, a higher energy density, and a higher adhesive force of the adhesive tape, indicating that the secondary battery can have good dynamic performance, a higher energy density and a lower probability of adhesive peeling during winding.

[0143] The type of inert material usually affects the dynamic performance, energy density and the probability of glue falling off during winding of the secondary battery. It can be seen from Examples 1-1, 2-7 and 2-8 that the secondary battery using the type of inert material within the scope of the present application has a relatively mild lithium precipitation on the interface, a relatively high energy density and a relatively high adhesive force of the adhesive tape, indicating that the secondary battery can have good dynamic performance, a relatively high energy density and a relatively low probability of glue falling off during winding.

[0144] The type of adhesive layer binder usually affects the dynamic performance, energy density and the probability of adhesive peeling during winding of the secondary battery. It can be seen from Examples 1-1, 2-9 and 2-11 that the secondary battery using the adhesive layer binder type within the scope of the present application has a relatively mild lithium precipitation on the interface, a relatively high energy density, and a relatively high adhesive force of the adhesive tape, indicating that the secondary battery can have good dynamic performance, a relatively high energy density and a relatively low probability of adhesive peeling during winding.

[0145] Table 3

[0146]

[0147]

[0148] The porosity of the porous substrate usually affects the dynamic performance, energy density and the probability of glue falling off during winding of the secondary battery. It can be seen from Examples 1-1, 3-1 and 3-4 that the selection of a secondary battery with a porous substrate having a porosity within the scope of the present application is conducive to maintaining the air permeability of the adhesive tape within an appropriate range, and is less likely to have interface problems. The lithium precipitation at the interface is relatively mild, the energy density is relatively high, and the adhesive force of the adhesive tape is relatively high, indicating that the secondary battery can have good dynamic performance, high energy density and low probability of glue falling off during winding.

[0149] The thickness of the porous substrate usually affects the dynamic performance, energy density and the probability of glue falling off during winding of the secondary battery. It can be seen from Examples 1-1, 3-5 to 3-10 that the secondary battery with a porous substrate thickness within the range of the present application has a relatively mild lithium precipitation on the interface, a relatively high energy density, and a relatively high adhesive force of the adhesive tape, indicating that the secondary battery can have good dynamic performance, a relatively high energy density and a relatively low probability of glue falling off during winding.

[0150] The thickness of the adhesive layer usually affects the dynamic performance, energy density and probability of adhesive peeling during winding of the secondary battery. It can be seen from Examples 1-1, 3-11 to 3-16 that the selection of a secondary battery with an adhesive layer thickness within the scope of the present application is conducive to maintaining the air permeability of the adhesive tape within an appropriate range and maintaining good bonding strength, with less lithium precipitation at the interface, higher energy density, and higher bonding strength of the adhesive tape, indicating that the secondary battery can have good dynamic performance, higher energy density and lower probability of adhesive peeling during winding.

[0151] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0152] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0153] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery, comprising adhesive tape, a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode tab, the adhesive tape is disposed between the separator and the positive electrode tab, and the adhesive tape comprises a porous substrate and an adhesive layer disposed on at least one surface of the porous substrate; wherein: The adhesive layer includes an inert substance, and the inert substance includes a first inert substance and a second inert substance, the particle size of the first inert substance is d1 nm, the particle size of the second inert substance is d2 nm, and 300<d1≤900, 50≤d2≤300; The average particle size of the first inert substance is D1 nm, the average particle size of the second inert substance is D2 nm, and 400≤D1≤800, 100≤D2≤200; In any area on the surface of the adhesive layer, the ratio of the number of particles of the first inert substance to the number of particles of the second inert substance is 3:7 to 7:

3.

2. The secondary battery according to claim 1, wherein 1 / 7≤D2 / D1≤1 / 3.

3. The secondary battery according to claim 1, wherein The average pore size of the porous substrate is P nm; D2 and P satisfy the following relationship: 0.5≤P / D2≤1.

4. The secondary battery according to claim 3, wherein 50≤P≤200。 5. The secondary battery according to claim 1, wherein The adhesive layer includes an adhesive layer binder, and the mass ratio of the inert substance to the adhesive layer binder is 3:7 to 7:

3.

6. The secondary battery according to claim 5, wherein The air permeability of the adhesive tape is 180s / 100mL to 600s / 100mL.

7. The secondary battery according to any one of claims 1 to 6, wherein The porosity of the porous substrate is 25% to 55%.

8. The secondary battery according to claim 5, wherein The thickness of the porous substrate is 9 μm to 24 μm.

9. The secondary battery according to claim 8, wherein The thickness of the adhesive layer is 2 μm to 6 μm.

10. The secondary battery according to claim 9, wherein The secondary battery satisfies at least one of the following characteristics: (1) the particle number ratio of the first inert substance to the second inert substance is 1:1 to 7:3; (2) 1 / 5≤D2 / D1≤1 / 3; (3) The mass ratio of the inert substance to the adhesive layer bonding material is 1:2 to 7:3; (4) The thickness of the porous substrate is 12 μm to 16 μm; (5) The thickness of the adhesive layer is 3 μm to 5 μm.

11. The secondary battery according to any one of claims 1 to 6, wherein The inert material includes at least one of boehmite, diaspore, halloysite or quartz sand.

12. The secondary battery according to any one of claims 1 to 6, wherein The adhesive layer adhesive includes at least one of polymethyl acrylate, polyacrylic acid, ethylene-acrylic acid copolymer, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyurethane or epoxy resin.

13. The secondary battery according to any one of claims 1 to 6, wherein The positive electrode sheet comprises a positive electrode active material layer and a positive electrode current collector, the positive electrode current collector comprises a first surface and a second surface opposite to each other, the positive electrode active material layer is at least arranged on the first surface of the positive electrode current collector, a first groove exposing the positive electrode current collector is arranged in the positive electrode active material layer, the positive electrode tab is arranged in the first groove and connected to the positive electrode current collector, and the second surface comprises a first empty foil area opposite to the first groove; The adhesive tape is attached to at least one of the surface of the positive electrode tab, the first empty foil area, the surface of the negative electrode sheet adjacent to the first groove, the surface of the negative electrode sheet adjacent to the first empty foil area, or the positive electrode sheet tailing area.

14. The secondary battery according to any one of claims 1 to 6, wherein The negative electrode sheet comprises a negative electrode current collector, a negative electrode active material layer and a negative electrode tab, the negative electrode current collector comprises a third surface and a fourth surface opposite to each other, the negative electrode active material layer is at least arranged on the third surface of the negative electrode current collector, a second groove exposing the negative electrode current collector is arranged in the negative electrode active material layer, the negative electrode tab is arranged in the second groove and connected to the negative electrode current collector, and the fourth surface comprises a second empty foil area opposite to the second groove; The adhesive tape is attached to at least one of the surface of the negative electrode tab or the second empty foil area. 15 . An electronic device comprising the secondary battery according to claim 1 .

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