Secondary battery and electronic device

Abstract

The application provides a secondary battery and an electronic device. The secondary battery comprises a gummed paper, 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 comprises a positive electrode tab. The gummed paper is arranged between the separator and the positive electrode tab. The gummed paper comprises a base material with holes and a gum layer arranged on at least one surface of the base material. The gum layer comprises inert substances. The inert substances comprise first inert substances and second inert substances. The particle size of the first inert substances is d1 nm, and the particle size of the second inert substances is d2 nm. 300 < d1 < 900, and 50 < d2 < 300. The average particle size of the first inert substances is D1 nm, and the average particle size of the second inert substances is D2 nm. 400 < D1 < 800, and 100 < D2 < 200. In any area on the surface of the gum layer, the particle quantity ratio of the first inert substances to the second inert substances is 3:7 to 7:3. Through the above arrangement, the secondary battery has good kinetic performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, and particularly relates to a secondary battery and an electronic device. BACKGROUND

[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 have been widely applied in the fields of aviation, aerospace, navigation, electric vehicles, consumer electronics and the like. A lithium ion battery is composed of a positive electrode sheet, a negative electrode sheet, a separator, a glue paper and the like. The ion-conducting glue paper in the existing lithium ion battery is produced by a micro-gravure process. The glue layer is mixed slurry (including boehmite, glue layer material and solvent) coated on a substrate. After the solvent volatilizes, the place originally occupied by the solvent is a pore. The boehmite in the glue layer is prone to agglomeration, resulting in excessive local impedance, which affects the kinetic performance of the lithium ion battery. SUMMARY

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

[0004] It should be noted that the lithium ion battery is taken as an example of the secondary battery in the summary of the present application to explain the present application, but the secondary battery of the present application is not limited to the lithium ion battery. The specific technical solutions are as follows:

[0005] The first aspect of the present application provides a secondary battery, the secondary battery comprising a gum paper, a positive electrode tab, a negative electrode tab, and a separator disposed between the positive electrode tab and the negative electrode tab, the positive electrode tab comprising a positive electrode tab, the gum paper being interposed between the separator and the positive electrode tab, the gum paper comprising a porous substrate and a gum layer disposed on at least one surface of the substrate; wherein the gum layer comprises an inert substance, the inert substance comprising a first inert substance and a second inert substance, the first inert substance having a particle size of d1 nm, the second inert substance having a particle size of d2 nm, and 300 < d1 ≤ 900, 50 ≤ d2 ≤ 300; the first inert substance having an average particle size of D1 nm, the second inert substance having an average particle size of D2 nm, and 400 ≤ D1 ≤ 800, 100 ≤ D2 ≤ 200; in any region on the surface of the gum 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 by the first aspect of the present application simultaneously adds the first inert substance with larger particles and the second inert substance with smaller particles in the gum layer, and adjusts the average particle size of the first inert substance and the second inert substance, and the particle number ratio of the first inert substance and the second inert substance within the range of the present application, so that the first inert substance with larger particles and the second inert substance with smaller particles cooperate, the first inert substance with larger particles can support pore formation on the surface of the porous substrate to improve the air permeability of the porous substrate, and then improve the air permeability of the gum paper, which can reduce the probability of lithium precipitation in the gum paper area. The probability of the second inert substance with smaller particles forming small pore apertures to improve the adhesion of the gum layer can reduce the probability of the gum layer falling off during the winding process. Thus, the kinetic performance of the secondary battery can be improved, and the processing performance of the secondary battery can also be improved. In addition, the gum paper has high air permeability, and lithium ions can freely shuttle in the area provided with the gum paper, so the capacity of the gum paper area can still be utilized, thereby improving the energy density of the secondary battery.

[0006] In some embodiments of the present application, 1 / 7 ≤ D2 / D1 ≤ 1 / 3. Adjusting 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 can reduce the probability of lithium precipitation in the gum paper area in the later stage of the charge-discharge cycle of the secondary battery to make the secondary battery have good kinetic performance, and also reduces the probability of the gum layer falling off during the winding process. In addition, lithium ions can freely shuttle in the area provided with the gum paper, so the capacity of the gum paper 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. By regulating 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 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 area where the adhesive tape is pasted in the later stage of the charge-discharge cycle of the secondary battery 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 area where the adhesive tape is pasted can still be developed, thereby improving the energy density of the secondary battery.

[0008] In some embodiments of the present application, 50≤P≤200. By regulating the average pore size of the porous substrate within the above range, the porous substrate has a suitable average pore size, which is beneficial to making the adhesive layer and the porous substrate have good adhesion and the adhesive tape have high air permeability.

[0009] In some embodiments of the present application, the adhesive layer comprises an adhesive layer binder, and the mass ratio of the inert substance and the adhesive layer binder is 3:7 to 7:3. By regulating the mass ratio of the inert substance and the adhesive layer binder 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 precipitation in the area where the adhesive tape is pasted in the later stage of the charge-discharge cycle of the secondary battery 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 area where the adhesive tape is pasted can still be developed, 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. It indicates 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%. By regulating the porosity of the porous substrate within the above range, the probability of interface lithium precipitation of the secondary battery during the charge-discharge cycle is small, 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 regulating the thickness of the porous substrate within the above range, the probability of local impedance increasing can be reduced, the interface lithium precipitation phenomenon of the secondary battery during the charge-discharge cycle can be reduced, and the kinetic performance of the secondary battery is improved. The loss of energy density due to the too thick thickness of the porous substrate can also be reduced, so that the secondary battery has high energy density.

[0013] In some embodiments of the present application, the thickness of the adhesive layer is 2-6 μm. Controlling the thickness of the adhesive layer within the above range reduces the probability of the adhesive layer falling off during the winding process, and also helps to reduce the energy density loss 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 satisfies at least one of the following characteristics: (1) the particle number ratio of the first inert substance to the second inert substance is 1:1-7:3; (2) 1 / 5≤D2 / D1≤1 / 3; (3) the mass ratio of the inert substance to the adhesive layer binder is 1:2-7:3; (4) the thickness of the porous substrate is 12-16 μm; (5) the thickness of the adhesive layer is 3-5 μm. This is advantageous for making the secondary battery have good kinetic performance and safety performance, and a higher energy density.

[0015] In some embodiments of the present application, the inert substance includes at least one of boehmite, diaspore, halloysite or quartz sand. Selecting the above-mentioned types of inert substance is advantageous for making the adhesive paper have better air permeability, and also making the adhesive paper have higher strength.

[0016] In some embodiments of the present application, the adhesive layer binder includes at least one of poly(methyl acrylate), poly(acrylic acid), ethylene-acrylic acid copolymer, poly(vinylidene fluoride), poly(tetrafluoroethylene), polyimide, butadiene-styrene rubber, sodium carboxymethyl cellulose, polyurethane or epoxy resin. Selecting the above-mentioned types of adhesive layer binder is advantageous for making the adhesive layer have better adhesion, and improving the adhesion of the adhesive paper.

[0017] In some embodiments of the present application, the positive electrode tab includes a positive electrode active material layer and a positive electrode current collector, the positive electrode current collector includes opposite first and second surfaces, the positive electrode active material layer is arranged on at least the first surface of the positive electrode current collector, the positive electrode active material layer is provided with a first groove exposing the positive electrode current collector, a positive electrode tab is arranged in the first groove and connected with the positive electrode current collector, and the second surface includes a first empty foil area opposite the first groove; the adhesive paper 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 tab adjacent to the first groove, the surface of the negative electrode tab adjacent to the first empty foil area or the end area of the positive electrode tab. Attaching the adhesive paper to the above-mentioned different positions can make the lithium ions in the area covered by the adhesive paper shuttle freely and exert the capacity of the active material, and also can reduce the risk of short circuit caused by the contact between the positive and negative electrodes and the probability of the occurrence of lithium precipitation, thereby making the secondary battery have a higher energy density and good safety performance and kinetic performance.

[0018] In some embodiments of the present application, the negative electrode tab includes a negative electrode current collector, a negative electrode active material layer, and a negative electrode tab, the negative electrode current collector includes opposite third and fourth surfaces, the negative electrode active material layer is disposed on at least the third surface of the negative electrode current collector, the negative electrode active material layer is provided with a second groove exposing the negative electrode current collector, the negative electrode tab is disposed in the second groove and connected with the negative electrode current collector, and the fourth surface includes a second empty foil area opposite 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 enable lithium ions to be embedded in the negative electrode active material layer covered by the adhesive tape, increase the lithium ion embedding sites, increase the capacity of the negative electrode active material layer, and thus enable the secondary battery to have a higher energy density.

[0019] The second aspect of the present application provides an electronic device including the secondary battery of any of the foregoing embodiments. Thus, the electronic device has good use performance.

[0020] The present application has the following beneficial effects:

[0021] This application provides a secondary battery and an electronic device. The secondary battery includes adhesive tape, a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrode. The positive electrode includes a positive electrode tab. The adhesive tape is located between the separator and the positive electrode tab. The adhesive tape includes a porous substrate and an adhesive layer disposed on at least one surface of the porous substrate. The adhesive layer includes an inert material, which includes a first inert material and a second inert material. The particle size of the first inert material is d1 nm, and the particle size of the second inert material is d2 nm, and 300 < d1 ≤ 900, 50 ≤ d2 ≤ 300. The average particle size of the first inert material is D1 nm, and the average particle size of the second inert material is D2 nm, and 400 ≤ D1 ≤ 800, 100 ≤ D2 ≤ 200. In any region on the surface of the adhesive layer, the ratio of the number of particles of the first inert material to the number of particles of the second inert material is 3:7 to 7:3. The adhesive tape incorporates a first inert material with larger particles and a second inert material with smaller particles in the adhesive layer. The ratio of the first to second inert material particles is controlled within a specified range. This allows the larger particles to work together, creating pores on the porous substrate surface, thus increasing the substrate's permeability and consequently the adhesive tape's permeability. This reduces the probability of lithium plating in the adhesive tape area. The smaller particles of the second inert material create smaller pores, improving the adhesive layer's bonding strength and reducing the likelihood of the adhesive layer falling off during winding. This improves both the kinetic and processing performance of the secondary battery. Furthermore, the high permeability of the adhesive tape allows lithium ions to move freely within the tape-covered area, ensuring the capacity of the tape-covered area remains utilized and ultimately increasing the secondary battery's energy density.

[0022] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0024] Figure 1 This is a schematic diagram of the cross-sectional structure of the adhesive tape along its thickness direction and longitudinal direction in some embodiments of this application;

[0025] Figure 2 This is a schematic diagram of the adhesive tape being applied to the positive electrode tab in some embodiments of this application;

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

[0027] Figure 4 A schematic view of the position of the adhesive paper in some embodiments of the present application.

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

[0029] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments and drawings of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0030] It should be noted that in the specific embodiments of the present application, the lithium ion battery is taken as an example of the secondary battery to explain the present application, but the secondary battery of the present application is not limited to the lithium ion battery.

[0031] The first aspect of the present application provides a secondary battery, which comprises an adhesive paper, a positive electrode tab, a negative electrode tab, and a separator arranged between the positive electrode tab and the negative electrode tab, the positive electrode tab comprising a positive electrode tab, the adhesive paper being arranged between the separator and the positive electrode tab, the adhesive paper comprising a perforated substrate and an adhesive layer arranged on at least one surface of the perforated substrate. The adhesive layer comprises an inert substance, the inert substance comprising a first inert substance and a second inert substance, the particle size of the first inert substance being d1 nm, the particle size of the second inert substance being 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.

[0032] The aforementioned "adhesive layer disposed on at least one surface of a porous substrate" means that the adhesive layer can be disposed on one surface or two surfaces of the porous substrate. For ease of understanding, the longitudinal direction of the adhesive tape is defined as X, its transverse direction as Y, and its thickness as Z. It should be understood that the above definitions of direction are for the purpose of describing this application, and the directions defined in this application can be understood based on the relative positions of the accompanying drawings and actual product elements. Figure 1 and Figure 2 As shown, when the adhesive tape 40 is attached to the positive electrode plate 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 both the transverse direction Y and the longitudinal direction X. In some embodiments, such as Figure 1 As shown, the adhesive tape 40 includes a porous substrate 41 and an adhesive layer 42, with the adhesive layer 42 disposed on one surface of the porous substrate 41. It is understood that in some embodiments, the adhesive layer 42 may also be disposed on the other surface of the porous substrate 41. In some embodiments, the adhesive layer 42 may 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 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 ranges. In this application, a first inert material with a particle size d1 satisfying 300 < d1 ≤ 900 is defined as a large-particle inert material; a second inert material with a particle size d2 satisfying 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 material is too small. The inert material is prone to clogging the pores of the porous substrate, which will reduce the air permeability of the porous substrate. In addition, the probability of the inert material itself agglomerating or agglomerating with the adhesive layer will increase, which will make the probability of lithium plating interface problems in the later stage of charge and discharge cycle of the secondary battery too high. When the particle size d1 is greater than 900, the particle size of the inert material is too large, which will reduce the adhesion of the adhesive layer. The inert material is also easy to be filtered out during the slurry filtration process due to its large particle size, which will affect the composition content of the adhesive layer, increase the difficulty of the preparation process, and affect the ion conduction 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-mentioned numerical ranges. If D1 is less than 400, the average particle size of the first inert substance is too small, the particle size of the first inert substance as a whole is too small, and when used in combination with the second inert substance, the overall particle size of the inert substance is too small, the number of inert substance particles used to support the pores is small, or the pore size of the inert substance is too small, which makes it difficult to improve the air permeability of the porous substrate, and the probability of reducing the area of the adhesive tape where lithium precipitation occurs is too small. If D1 is greater than 800, the average particle size of the first inert substance is too large, the particle size of the first inert substance as a whole is too large, which will reduce the adhesion of the adhesive layer and the inert substance will be easily filtered out during the slurry filtration process due to the too large particle size, which will affect the content of the adhesive layer material composition, 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-mentioned numerical ranges. If 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 as a whole is too small, 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 itself or the adhesive layer adhesive agglomerating will increase, thereby increasing the probability of the secondary battery having a lithium precipitation interface problem at the later stage of the charge and discharge cycle. If 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 as a whole is too large, which will affect the improvement of the adhesive force of the second inert substance to the adhesive layer, thereby increasing the probability of the adhesive tape falling off during the winding process.

[0036] For example, the particle quantity ratio 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 ratios. If the particle quantity ratio of the first inert substance to the second inert substance is less than 3:7, the quantity of the first inert substance is too small to support the quantity of the large-particle inert substance for the purpose of forming pores, and the air permeability of the adhesive tape is too poor. If the quantity of the second inert substance is too large, the small-particle inert substance that is in excess of the purpose of improving the adhesive strength of the adhesive layer is prone to block the pores of the porous substrate, the air permeability of the adhesive tape is poor, and the small-particle inert substance is difficult to disperse and prone to agglomeration, which increases the probability of the occurrence of the problem of the point-like lithium precipitation interface of the secondary battery during the charge and discharge cycle. If the particle quantity ratio of the first inert substance to the second inert substance is greater than 7:3, the quantity of the second inert substance is too small, the quantity of the small-particle inert substance that is in excess of the purpose of improving the adhesive strength of the adhesive layer is too small, and the adhesive strength of the adhesive layer is too poor. The probability of the adhesive layer falling off during the winding process is too large. If the quantity of the first inert substance is too large, the specific surface area of the large-particle inert substance is small, the adhesion to the porous substrate is poor, the adhesive strength of the porous substrate and the adhesive layer is poor, the probability of the adhesive layer falling off during the winding process is too large, or the probability of the occurrence of the problem of the local lithium precipitation interface of the secondary battery during the charge and discharge cycle is too large.

[0037] Overall, the adhesive tape of the secondary battery of the present application simultaneously adds the first inert substance with large particles and the second inert substance with small particles in the adhesive layer, and controls the average particle size of the first inert substance and the second inert substance and the particle quantity ratio of the first inert substance to the second inert substance within the range of the present application. The first inert substance with large particles and the second inert substance with small particles cooperate with each other. The first inert substance with large particles can support the formation of pores on the surface of the porous substrate to improve the air permeability of the porous substrate, and further improve the air permeability of the adhesive tape. This can reduce the probability of lithium precipitation in the area of the adhesive tape. The second inert substance with small particles can improve the adhesive strength of the adhesive layer to reduce the probability of the adhesive layer falling off during the winding process. Thus, the kinetic 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 high air permeability, and lithium ions can freely shuttle in the area provided with the adhesive tape. Therefore, the capacity of the area of the adhesive tape can still be utilized, and thus the energy density of the secondary battery can be improved.

[0038] In the present application, the particle size refers to the single particle size of a single particle, and can also be understood as the equivalent particle size. The average particle size refers to the average value obtained by measuring the particle size of the inert substance particles in a region after selecting several arbitrary regions on the surface of the adhesive layer. The above-mentioned "several" can be one or more than two. The present application does not particularly limit the size of the above-mentioned "arbitrary region", and those skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved.

[0039] The control method of the particle size of the inert substance is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, it can be achieved by crushing and sieving. The control method of the average particle size of the inert substance is not particularly limited in the present application, 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, the average particle size can be tested by scanning electron microscopy, and the inert substance particles with the desired particle size can be selected. When testing the average particle size of the particles, the average value of the maximum circumscribed circle diameter of the outer contour of 50 particles is selected as the average particle size of the particles.

[0040] It can be understood 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 greater than 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 particle number ratio of the first inert substance to the second inert substance is 1:1 to 7:3. For example, the particle number ratio 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 ranges. By controlling the particle number ratio of the first inert substance to the second inert substance within the above range, the first inert substance and the second inert substance cooperate with each other to support the pore-forming of the porous substrate surface to improve the air permeability of the adhesive paper, and also to make the inert substance have a high adhesion to the porous substrate surface, thereby improving the adhesion between the porous substrate and the adhesive layer. In this way, the probability of lithium precipitation in the adhesive paper area of the secondary battery at the later stage of the charging and discharging cycle of the secondary battery can be reduced, and the secondary battery has good kinetic performance. In addition, the probability of adhesive layer falling off during the winding process is also reduced. In addition, lithium ions can freely shuttle in the area provided with the adhesive paper, so the capacity of the adhesive paper area can still be utilized, thereby improving the energy density of the secondary battery.

[0042] The control method of the particle number ratio of the first inert substance to the second inert substance is not particularly limited in the present application, 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 sieving, respectively, and then mixed according to the actual needs to achieve the corresponding particle number ratio.

[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-mentioned numerical ranges. By regulating 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-mentioned range, the large-particle inert substance and the small-particle inert substance are matched, which is conducive to supporting the pore-forming of the surface of the porous substrate to increase the air permeability of the adhesive paper, and is also conducive to increasing the adhesion of the inert substance to the surface of the porous substrate, so that the adhesion between the porous substrate and the adhesive layer is increased. In this way, the probability of lithium precipitation in the area of the adhesive paper in the later stage of the charge-discharge cycle of the secondary battery can be reduced, so that the secondary battery has good kinetic performance, and the probability of the adhesive layer falling off during the winding process of the adhesive paper is also reduced. In addition, lithium ions can freely shuttle in the area provided with the adhesive paper, so the capacity of the area of the adhesive paper can still be utilized, 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-mentioned numerical ranges. By regulating 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-mentioned range, the large-particle inert substance and the small-particle inert substance are matched, which is more conducive to supporting the pore-forming of the surface of the porous substrate to increase the air permeability of the adhesive paper, and is also more conducive to increasing the adhesion of the inert substance to the surface of the porous substrate, so that the adhesion between the porous substrate and the adhesive layer is increased. In this way, the probability of lithium precipitation in the area of the adhesive paper in the later stage of the charge-discharge cycle of the secondary battery can be reduced, so that the secondary battery has good kinetic performance, and the probability of the adhesive layer falling off during the winding process of the adhesive paper is also reduced. In addition, lithium ions can freely shuttle in the area provided with the adhesive paper, so the capacity of the area of the adhesive paper can still be utilized, 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-mentioned numerical ranges. By regulating 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-mentioned range, the second inert substance has a higher adhesion to the porous substrate, and the probability of small particle inert substances falling into the pores of the porous substrate is smaller, so that the adhesive layer has a better bonding force with the porous substrate, 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 lower, and the probability of lithium precipitation in the area of the adhesive tape during the later stage of the charge-discharge cycle of the secondary battery is smaller, so that the secondary battery has good kinetic performance. Lithium ions can freely shuttle in the area provided with the adhesive tape, so the capacity of the area of the adhesive tape can still be utilized, 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-mentioned numerical ranges. By regulating the average pore size of the porous substrate within the above-mentioned range, the porous substrate has a suitable average pore size, which is beneficial to make the adhesive layer have a better bonding force with the porous substrate, 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 lower, and the probability of lithium precipitation in the area of the adhesive tape during the later stage of the charge-discharge cycle of the secondary battery is smaller, so that the secondary battery has good kinetic performance. Lithium ions can freely shuttle in the area provided with the adhesive tape, so the capacity of the area of the adhesive tape can still be utilized, thereby improving the energy density of the secondary battery.

[0047] The present application does not have a particular limitation on the regulation method of 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 regulating the bidirectional (lateral and longitudinal) stretching ratio during the preparation process of the porous substrate.

[0048] In some embodiments of the present application, the adhesive layer comprises an adhesive layer binder, and the mass ratio of the inert substance and the adhesive layer binder is 3:7 to 7:3. For example, the mass ratio of the inert substance and 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 within any two of the above-mentioned ratio ranges. Controlling the mass ratio of the inert substance and the adhesive layer binder within the above-mentioned range is conducive to making the adhesive paper have a higher air permeability and adhesion, so that the probability of the adhesive layer falling off during winding is lower, and the probability of lithium precipitation in the area where the adhesive paper is pasted in the later stage of the secondary battery charging and discharging cycle is smaller to make the secondary battery have good kinetic performance. Lithium ions can shuttle freely in the area where the adhesive paper is provided, so the capacity of the area where the adhesive paper is pasted can still be developed, thereby improving the energy density of the secondary battery.

[0049] In some embodiments of the present application, the mass ratio of the inert substance and the adhesive layer binder is 1:2 to 7:3. For example, the mass ratio of the inert substance and the adhesive layer binder is 1:2, 1:1, 7:6, 7:5, 7:4, 7:3, or any ratio within any two of the above-mentioned ratio ranges. Controlling the mass ratio of the inert substance and the adhesive layer binder within the above-mentioned range is conducive to further improving the air permeability and adhesion of the adhesive paper. Thus, the probability of the adhesive layer falling off during winding is further reduced, and the probability of lithium precipitation in the area where the adhesive paper is pasted in the later stage of the secondary battery charging and discharging cycle is further reduced to make the secondary battery have better kinetic performance.

[0050] In some embodiments of the present application, the air permeability of the adhesive paper is 180 s / 100 mL to 600 s / 100 mL. For example, the air permeability of the adhesive paper is 180 s / 100 mL, 200 s / 100 mL, 220 s / 100 mL, 240 s / 100 mL, 260 s / 100 mL, 280 s / 100 mL, 3200 s / 100 mL, 380 s / 100 mL, 400 s / 100 mL, 420 s / 100 mL, 452 s / 100 mL, 480 s / 100 mL, 512 s / 100 mL, 530 s / 100 mL, 550 s / 100 mL, 573 s / 100 mL, 600 s / 100 mL, or any value within any two of the above-mentioned value ranges. Controlling the air permeability of the adhesive paper within the above-mentioned range is conducive to reducing the probability of lithium precipitation in the area where the adhesive paper is pasted in the later stage of the secondary battery charging and discharging cycle to make the secondary battery have good kinetic performance.

[0051] The application does not have special restrictions on the regulation method of the air permeability of the adhesive paper, as long as the application purpose can be achieved. For example, it can be achieved by regulating at least one of the mass ratio of inert substances in the adhesive layer and the adhesive layer bonding material, the porosity of the porous substrate, or the average pore diameter of the porous substrate. Generally speaking, the more the content of inert substances in the adhesive layer, the better the air permeability of the adhesive paper (the smaller the air permeability value); the less the content of inert substances in the adhesive layer, the worse the air permeability of the adhesive paper (the larger the air permeability value). The larger the porosity of the porous substrate, the better the air permeability of the adhesive paper; the smaller the porosity of the porous substrate, the worse the air permeability of the adhesive paper. The larger the average pore diameter of the porous substrate, the better the air permeability of the adhesive paper; the smaller the average pore diameter of the porous substrate, the worse the air permeability of the adhesive paper.

[0052] In some embodiments of the 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 within any two of the above-mentioned numerical ranges. By regulating the porosity of the porous substrate within the above-mentioned range, the porous substrate has better air permeability on the basis of higher strength, and the adhesive paper has better air permeability, and the probability of interface lithium precipitation of the secondary battery during the charge and discharge cycle is smaller, and the secondary battery has good kinetic performance.

[0053] The application does not have special restrictions on the regulation method of the porosity of the porous substrate, as long as the application purpose can be achieved. For example, it can be achieved by regulating the two-way stretching ratio in the preparation process of the porous substrate.

[0054] In some embodiments of the 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 within any two of the above-mentioned numerical ranges. As shown in FIG. 4, the thickness of the porous substrate 41 is T Figure 1 41 The application does not have special restrictions on the regulation method of the porosity of the porous substrate, as long as the application purpose can be achieved. For example, it can be achieved by regulating the two-way stretching ratio in the preparation process of the porous substrate.

[0055] In some embodiments of the 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 within any two of the above-mentioned numerical ranges. As shown in FIG. 4, the thickness of the porous substrate 41 is T​Figure 1 As shown, the thickness of the porous substrate 41 is expressed as T 41 As shown, controlling the thickness of the porous substrate within the aforementioned range helps to further reduce the probability of adhesive layer agglomeration leading to uneven adhesive layer, and also helps to further reduce the energy density loss of the secondary battery caused by excessive porous substrate thickness. This results in the secondary battery having good kinetic performance and high energy density.

[0056] This application does not impose any particular limitation on the material of the porous substrate, as long as it can achieve the purpose of this application. For example, the materials of the porous substrate include, but are not limited to, at least one of polypropylene, low-density polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose membrane or nonwoven fabric.

[0057] In some embodiments of this application, the thickness of the adhesive layer is from 2 μm to 6 μm. For example, the thickness of the adhesive 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 adhesive layer 42 is expressed as T 42 As shown. Controlling the thickness of the adhesive layer within the above range is beneficial for the adhesive paper to have good adhesion, reduces the probability of the adhesive layer falling off during the winding process, and also helps to reduce the energy density loss of the secondary battery caused by excessive adhesive layer thickness, thereby enabling the secondary battery to have a higher energy density.

[0058] In some embodiments of this 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 adhesive layer 42 is expressed as T 42 As shown. Controlling the thickness of the adhesive layer within the above range is beneficial for the adhesive paper to have good adhesion, reduces the probability of the adhesive layer falling off during the winding process, and also helps to reduce the energy density loss of the secondary battery caused by excessive adhesive layer thickness, thereby enabling the secondary battery to have a higher energy density.

[0059] This application does not impose any particular limitation on the thickness of the adhesive tape, as long as it achieves the purpose of this application. For example, the thickness of the adhesive tape can be from 11 μm to 36 μm.

[0060] In some embodiments of the present application, the inert substance includes at least one of boehmite, diaspore, halloysite or quartz sand. In some embodiments, the first inert substance and the second inert substance each independently includes at least one of boehmite, diaspore, halloysite or quartz sand. In some embodiments, the first inert substance and the second inert substance are of the same kind. In other embodiments, the first inert substance and the second inert substance are of different kinds. The use of the above-mentioned kinds of inert substances is conducive to making the adhesive paper have better air permeability and also make the adhesive paper have higher strength. In this way, the probability of interface lithium precipitation of the secondary battery during the charge and discharge cycle process is reduced, thereby making the secondary battery have good kinetic performance. The probability of the adhesive paper being punctured by the surface particles or burrs of the positive electrode sheet or the negative electrode sheet is smaller, thereby making the secondary battery have good safety performance.

[0061] In some embodiments of the present application, the adhesive layer binder includes at least one of polyacrylate, 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. The use of the above-mentioned kinds of adhesive layer binders is conducive to making the adhesive layer have better adhesion and improve the adhesion of the adhesive paper.

[0062] The weight average molecular weight of the above-mentioned adhesive layer binder is not particularly limited in the present application, as long as the purpose of the present application can be achieved.

[0063] For the convenience of understanding, it is defined that in the unfolded state of the positive electrode sheet, the length direction of the positive electrode sheet itself is the same as the transverse direction Y of the adhesive paper, the width direction of the positive electrode sheet itself is the same as the longitudinal direction X of the adhesive paper, and the thickness direction of the positive electrode sheet itself is the same as the thickness direction Z of the adhesive paper. It can be understood that in the unfolded state of the positive electrode sheet, the negative electrode sheet and the separator, the length direction, the width direction and the thickness direction of the positive electrode current collector, the positive electrode 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 tab includes a positive electrode active material layer and a positive electrode current collector, the positive electrode current collector includes opposite first and second surfaces, the positive electrode active material layer is disposed on at least the first surface of the positive electrode current collector, the positive electrode active material layer is provided with a first groove exposing the positive electrode current collector, the positive electrode tab is disposed in the first groove and connected with the positive electrode current collector, and the second surface includes a first empty foil area opposite 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 tab adjacent to the first groove, the surface of the negative electrode tab adjacent to the first empty foil area, or the end area of the positive electrode tab. The above "the positive electrode active material layer is disposed on at least the first surface of the positive electrode current collector" means that, in some embodiments, the positive electrode active material layer is disposed on the first surface of the positive electrode current collector, and in other embodiments, the positive electrode active material layer is disposed on both the first and second surfaces of the positive electrode current collector. The "first surface" and "second surface" can be part or all of the surface of the positive electrode current collector. It should be noted that the negative electrode tab in "the surface of the negative electrode tab adjacent to the first groove" is not the same layer of negative electrode tab as the negative electrode tab in "the surface of the negative electrode tab adjacent to the first empty foil area", but two layers of negative electrode tabs adjacent to the positive electrode tab, and the above "two layers of negative electrode tabs" can be two negative electrode tabs or one negative electrode tab after being wound to form two layers. For example, Figure 3As shown, the separator 30 is located between the positive electrode tab 10 and the negative electrode tab 20, the positive electrode tab 10 comprises a positive electrode current collector 11, a positive electrode active material layer 12 and a positive electrode tab 13, the positive electrode current collector 11 comprises a first surface 11a and a second surface 11b opposite along the thickness direction Z of the positive electrode current collector 11, the positive electrode active material layer 12 is arranged on the first surface 11a of the positive electrode current collector 11 and also arranged on the second surface 11b of the positive electrode current 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 current collector 11, and the positive electrode tab 13 is arranged in the first groove 15 and connected with the positive electrode current collector 11, and the second surface 11b comprises a first empty foil area 16 opposite to the first groove 15. The adhesive tape 40 is respectively adhered to the surface of the positive electrode tab 13, the first empty foil area 16, the surface of the negative electrode tab 20 adjacent to the first groove 15, the surface of the negative electrode tab 20 adjacent to the first empty foil area 16 and the end area of the positive electrode tab 10. Generally, along the length direction Y of the positive electrode tab 10, the length of the adhesive tape 40 adhered 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 adhered to the surface of the negative electrode tab 20 adjacent to the first groove 15 and the surface of the negative electrode tab 20 adjacent to the first empty foil area 16. Adhering the adhesive tape to the surface of the positive electrode tab and the surface of the negative electrode tab adjacent to the first groove can reduce the probability that the burr of the positive electrode tab penetrates the negative electrode active material layer and contacts the negative electrode current collector to cause short circuit, the area covered by the adhesive tape adhered to the surface of the positive electrode tab is covered by the positive electrode active material layer, lithium ions can be normally deintercalated, and the deintercalated lithium ions can also be normally intercalated into the opposite negative electrode active material layer, thereby reducing the probability of capacity waste and lithium precipitation phenomenon. Adhering the adhesive tape to the first empty foil area and the surface of the negative electrode tab adjacent to the first empty foil area can reduce the probability that the burr in the first empty foil area penetrates the negative electrode active material layer and contacts the negative electrode current collector to cause short circuit, the area covered by the adhesive tape adhered to the first empty foil area is covered by the positive electrode active material layer, lithium ions can be normally deintercalated, and the deintercalated lithium ions can also be normally intercalated into the opposite negative electrode active material layer, thereby reducing the probability of capacity waste and lithium precipitation phenomenon. Adhering the adhesive tape to the end area of the positive electrode tab can reduce the probability that the positive electrode current collector contacts the negative electrode tab. Thus, adhering the adhesive tape to the above different positions can make lithium ions in the area covered by the adhesive tape shuttle freely and play the capacity of the active material, and also can reduce the risk of short circuit caused by the contact between the positive electrode and the negative electrode and the probability of lithium precipitation phenomenon, thereby making the secondary battery have higher energy density and good safety performance and kinetic performance.

[0065] In some embodiments of the present application, the negative electrode tab includes a negative electrode current collector, a negative electrode active material layer, and a negative electrode tab, the negative electrode current collector includes opposite third and fourth surfaces, the negative electrode active material layer is disposed on at least the third surface of the negative electrode current collector, the negative electrode active material layer is provided with a second groove exposing the negative electrode current collector, the negative electrode tab is disposed in the second groove and connected to the negative electrode current collector, and the fourth surface includes a second empty foil area opposite 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. The above "the negative electrode active material layer is disposed on at least the third surface of the negative electrode current collector" means that, in some embodiments, the negative electrode active material layer is disposed on the third surface of the negative electrode current collector, and in other embodiments, the negative electrode active material layer is disposed on both the third and fourth surfaces of the negative electrode current collector. As shown in Figure 4 The separator 30 is located between the positive electrode tab 10 and the negative electrode tab 20, the negative electrode tab 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 opposite third and fourth surfaces 21c and 21d along the thickness direction Z thereof, the negative electrode active material layer 22 is disposed on the third and fourth surfaces 21c and 21d of the negative electrode current collector 21, the negative electrode active material layer 22 located on the third surface 21c is provided with a second groove 25 exposing the negative electrode current collector 21, the negative electrode tab 23 is disposed in the second groove 25 and connected to the negative electrode current collector 21, and the fourth surface 21d includes a second empty foil area 26 opposite 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 tab 10 adjacent to the second groove 25 and the surface of the positive electrode tab 10 adjacent to the second empty foil area 26 are attached with non-ionic adhesive tape 50. Attaching the adhesive tape to the surface of the negative electrode tab and the second empty foil area can enable lithium ions to be embedded in 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 enabling the secondary battery to have a higher energy density.

[0066] The present application does not have a particular limitation on the type of non-ionic adhesive tape, and any non-ionic adhesive tape known in the art can be selected as needed as long as the purpose of the present application can be achieved.

[0067] The present application does not have a particular limitation 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 aluminum alloy. The present application does not have a particular limitation 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 nickel-plated copper (Ni-Cu).

[0068] The kind of the positive electrode current collector is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the positive electrode current collector can include an aluminum foil, an aluminum alloy foil, or the like. The kind of the positive electrode active material layer is not particularly limited in the present application, as long as the object of the present application can be achieved. In an embodiment of the present application, the positive electrode active material layer includes a positive electrode active material. The kind of the positive electrode active material is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the positive electrode active material can include at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate, or the like. Optionally, the positive electrode active material layer further includes a positive electrode conductive agent, a positive electrode binder. The kind of the positive electrode conductive agent and the positive electrode binder in the positive electrode active material layer is not particularly limited in the present application, as long as the object of the present application can be achieved. The mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder in the positive electrode active material layer is not particularly limited in the present application, and can be selected by a person skilled in the art according to actual needs, as long as the object 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 object 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 kind of the negative electrode current collector is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the negative electrode current collector can include a copper foil, a copper alloy foil, a nickel foil, a titanium foil, a nickel foam, a copper foam, or the like. The kind of the negative electrode active material layer is not particularly limited in the present application, as long as the object of the present application can be achieved. In an embodiment of the present application, the negative electrode active material layer includes a negative electrode active material. The kind of the negative electrode active material is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the negative electrode active material can include at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbeads, tin-based material, silicon-based material, lithium titanate, transition metal nitride, or natural flake graphite, or the like. Optionally, the negative electrode active material layer further includes at least one of a negative electrode conductive agent, a thickening agent, and a negative electrode binder. The kind of the negative electrode conductive agent, the thickening agent, and the negative electrode binder in the negative electrode active material layer is not particularly limited in the present application, as long as the object of the present application can be achieved. The mass ratio of the negative electrode active material, the negative electrode conductive agent, the thickening agent, and the negative electrode binder in the negative electrode active material layer is not particularly limited in the present application, as long as the object of the present application can be achieved. The thickness of the negative electrode current collector and the negative electrode active material layer is not particularly limited in the present application, as long as the object 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 diaphragm is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm can include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of diaphragm can include at least one of woven film, non-woven film, microporous film, composite film, calendered film or spunlaced film.

[0071] The secondary battery of the present application also includes a packaging bag and an electrolyte, and the adhesive layer, the positive electrode sheet, the negative electrode sheet, the diaphragm and the electrolyte are contained in the packaging bag. The packaging bag and the electrolyte are not particularly limited in the present application, and the packaging bag and the electrolyte known in the art can be selected as needed, as long as the purpose of the present application can be achieved.

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

[0073] The preparation method of the adhesive layer is not particularly limited in the present application, 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) mixing the inert material and the adhesive layer binder, then adding the solvent and stirring uniformly to obtain the adhesive layer slurry; (2) coating the adhesive layer slurry on the surface of the release film by micro-concave roller, and the slurry is film-formed and shrunk during the drying process, and finally a porous adhesive layer is formed. After the adhesive layer is compounded with the porous substrate, a release agent is arranged on the surface of the porous substrate away from the adhesive layer, and the adhesive layer is obtained after drying, winding, slitting and waiting for use. The solid content of the adhesive layer slurry is not particularly limited in the present application, 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 type of the above-mentioned "solvent" is not particularly limited in the present application, as long as the purpose of the present application can be achieved. The temperature of drying and drying in the above-mentioned step (2) is not particularly limited in the present application, as long as the purpose of the present application can be achieved. The above-mentioned release film and release agent are not particularly limited in the present application, and those skilled in the art can select the known release film and release agent according to the actual situation, as long as the purpose of the present application can be achieved.

[0074] The preparation method of the secondary battery is not particularly limited in the present application, and a 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 separator, the positive electrode sheet, the separator and the negative electrode sheet in order, and pasting the adhesive paper, then winding, folding, etc. according to the need to obtain the electrode assembly of the winding structure, placing the electrode assembly into the packaging bag, injecting the electrolyte into the packaging bag and sealing to obtain the secondary battery; or stacking the separator, the positive electrode sheet, the separator and the negative electrode sheet in order, and pasting the adhesive paper, then fixing the four corners of the entire stack structure to obtain the electrode assembly of the stack structure, placing the electrode assembly into the packaging bag, injecting the electrolyte into the packaging bag and sealing to obtain the secondary battery.

[0075] The second aspect of the present application provides an electronic device comprising the secondary battery of any one of the preceding embodiments. Therefore, the electronic device has good use performance.

[0076] The electronic device of the present application is not particularly limited, and can include, but is not limited to, the following types: notebook computers, pen input computers, mobile computers, electronic book players, portable telephones, portable facsimile machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting appliances, toys, game machines, watches, power tools, flashlights, cameras, household large storage batteries and lithium ion capacitors, etc.

[0077] Embodiment

[0078] Hereinafter, the embodiments of the present application will be described more specifically by citing examples and comparative examples. Various tests and evaluations were performed according to the following methods.

[0079] Test methods and equipment:

[0080] Method for extracting a porous substrate from a lithium ion battery:

[0081] The lithium ion battery is disassembled in an environment at room temperature and humidity less than 20%, and the positive electrode sheet, the separator and the negative electrode sheet are separated, and then the adhesive tape is torn off with tweezers. If the adhesive tape is located between the negative electrode sheet and the separator, after tearing off the adhesive tape, it is sequentially placed in a mixed solvent of toluene and ethyl acetate (mass ratio of toluene to ethyl acetate is 7:3) and water, and after stirring at 50°C for 20 min, it is taken out and dried at 100°C for 2h until no solution, and a porous substrate is obtained; if the adhesive tape is located between the positive electrode sheet and the separator, after tearing off the adhesive tape, it is placed in N-methyl pyrrolidone (NMP), stirred at 50°C for 20 min, taken out, and dried at 100°C for 2h until no solution, and a porous substrate is obtained.

[0082] Test of thickness:

[0083] (1) Test of thickness of adhesive tape T 40 :

[0084] The thickness T 总 of the positive electrode sheet and the negative electrode sheet in the lithium ion battery is measured with a screw micrometer at the position where the sheet is pasted with the adhesive tape, and the thickness T 极片 of the sheet without the adhesive tape is measured, and the thickness T 40 of the adhesive tape is T 总 -T 极片 .

[0085] (2) Test of thickness T 41 of the porous substrate:

[0086] The thickness of the porous substrate sample at 6 positions is randomly measured with a screw micrometer, and the average value is obtained to obtain the thickness T 41 of the porous substrate.

[0087] (3) Test of thickness T 42 of the adhesive layer:

[0088] The thickness T 40 of the adhesive tape and the thickness T 41 of the porous substrate are calculated to obtain the thickness T 42 of the adhesive layer: T 42 =T 40 -T 41 .

[0089] Test of average pore size of the porous substrate:

[0090] The porous substrate sample is taken, and a scanning electron microscope (SEM) image is taken at an accelerating voltage (EHT) = 3kV and a magnification of 10000 times. The pore size is measured by randomly selecting 5 different regions of 10μm×10μm size using imageJ software, and the average value is taken as the median pore size, i.e. the average pore size is obtained.

[0091] Test of particle size, average particle size and ratio of number of inert particles:

[0092] Take the adhesive tape sample, at EHT = 3 kV, magnification 10000 times, take SEM image of the adhesive layer. Using imageJ software, randomly select 5 different regions of 10 μm x 10 μm size to count the number of large particles, that is, the ratio of the number of first inert particles and second inert particles can be obtained; At the same time, 50 large particle inert particles and 50 small particle inert particles are selected respectively, and the maximum circumscribed circle diameter of the outer contour is tested and averaged as the average particle size of the particles.

[0093] Test of air permeability of adhesive tape:

[0094] Cut the adhesive tape sample to 50 mm x 50 mm, place it on the air permeability tester, press the start button, and the test is completed after five seconds. The air permeability value is automatically displayed. Each sample is tested 5 times, and the average value is recorded as the air permeability of the adhesive tape.

[0095] Test of porosity of the porous substrate:

[0096] The porosity of the porous substrate is calculated using the following formula: φ = [1 - m(s x h x p)] x 100%. Wherein, 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 p is the density of the porous substrate material.

[0097] Test of lithium precipitation:

[0098] The lithium ion battery is charged at a low temperature (12℃) at a rate of 1.5C to a set voltage of 4.45V, and discharged at a rate of 1.5C to 3V. After 10 cycles, the lithium ion battery is disassembled, and the surface of the positive tab at the adhesive tape position is observed for the presence of silver-white lithium metal. The total area of the adhesive tape is calculated, and the area of lithium precipitation is less than 1% for no lithium precipitation, 1% to 5% for slight lithium precipitation, greater than 5% to 10% for moderate lithium precipitation, and greater than 10% for severe lithium precipitation.

[0099] The degree of lithium precipitation is used to represent the kinetic performance of the lithium ion battery. The more severe the degree of lithium precipitation (i.e. the larger the area of lithium precipitation), the worse the kinetic performance of the lithium ion battery; the less severe the degree of lithium precipitation (i.e. the smaller the area of lithium precipitation), the better the kinetic performance of the lithium ion battery.

[0100] Test of energy density (ED):

[0101] Taking the lithium ion battery factory packaging label as an example, when the voltage range marked on the factory battery packaging is 3.0V to 4.45V, the charge cut-off voltage is 4.45V, and the discharge cut-off voltage is 3.0V.

[0102] The comparative examples and the examples were all charged at 0.2C to 4.45V at 25℃, charged at 4.45V to 0.025C to full charge, discharged at 0.2C to 3.0V after full charge, and the above process was repeated 3 times, and the average capacity was taken as the actual capacity.

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

[0104] Test of adhesion:

[0105] The adhesion between the adhesive tape and the negative electrode sheet was tested by 180° peeling. The adhesive tape and the negative electrode sheet with a length of 100mm to 300mm were cut into samples with a size of 54.2mm x 72.5mm; the cut adhesive tape and the negative electrode sheet were neatly stacked, the stacked samples were placed in a flat press to adjust the pressure to 2kg to composite the adhesive tape and the negative electrode sheet to obtain samples; the samples were cut into small strips of 72.5mm x 15mm using a die and a punch press, the adhesive tape and the negative electrode sheet were separated, and the samples were connected with A4 paper with a width of 15mm, and the connected parts were adhered with corrugated tape on both sides to complete the sample preparation; the high-iron tensile testing machine was started, and was set as follows: adhesion test, speed 50mm / min, initial clamp distance 40mm; click "start" to pre-stretch ~ 5mm; after pre-stretching, the force, displacement, etc. were reset to zero, and the test was started, and at least 5 samples were measured for each group. The average value was taken as the final adhesion value.

[0106] The adhesion was used to represent the probability of the adhesive layer falling off during winding. The greater the adhesion, the smaller the probability of the adhesive layer falling off during winding; the smaller the adhesion, the greater the probability of the adhesive layer falling off during winding.

[0107] Example 1-1

[0108] Preparation of adhesive tape

[0109] After mixing the inert substance boehmite and the adhesive layer binder polyacrylate (weight average molecular weight Mw = 86W), adding ethyl acetate as a solvent, and stirring uniformly, a slurry of the adhesive layer with a solid content of 20wt% was obtained. The mass ratio of the inert substance and the adhesive layer binder was 1:1, the inert substance included a first inert substance with a particle size d1 satisfying 300 < d1 ≤ 900 and a second inert substance with a particle size d2 satisfying 50 ≤ d2 ≤ 300, the average particle size D1 of the first inert substance was 600nm, and the average particle size D2 of the second inert substance was 140nm. The particle number ratio of the first inert substance to the second inert substance was 3:2.

[0110] The above adhesive layer slurry was coated on the surface of a release film polyethylene terephthalate (PET) film with a release force of 10g by a micro-concave roller, and after drying at 110℃, an adhesive layer with a thickness T42 = 3 pm adhesive layer, and then the adhesive layer was transferred to the surface of the porous base material (thickness T 41 = 14 pm, porosity 45%, and then the adhesive layer was transferred to the surface of the porous base material, and the intermediate product of the porous base material with the release film was obtained; the surface of the porous base material (the opposite side of the adhesive layer) of the intermediate product was coated with a micro-concave roller with a silicone release agent (manufacturer: Dow Corning), and after drying, the release film was removed while the porous base material was wound to obtain a porous base material with a thickness T 40 = 17 pm.

[0111] <Preparation of the positive electrode sheet>

[0112] The positive electrode active material lithium cobaltate, the positive electrode conductive agent conductive carbon black (Super P), and the positive electrode binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95.5:2.5:2.0, and NMP was added as a solvent. The positive electrode slurry was stirred in a vacuum stirrer until the solid content was 72 wt% and the system was uniform. The positive electrode slurry was uniformly coated on one surface of the positive electrode current collector aluminum foil with a thickness of 10 pm, and was dried at 85°C to obtain a positive electrode sheet with a single-sided coated positive electrode active material layer (thickness 50 pm). Then, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coated positive electrode active material layer. After cold pressing, cutting, and welding of the positive electrode tabs, an aluminum tab, a positive electrode sheet with a size of 70 mm x 1400 mm was obtained for use.

[0113] <Preparation of the negative electrode sheet>

[0114] The negative electrode active material artificial graphite, the negative electrode thickening agent sodium carboxymethyl cellulose, and the negative electrode binder styrene-butadiene rubber were mixed in a mass ratio of 98.2:0.8:1.0, and then deionized water was added as a solvent. The negative electrode slurry was stirred in a vacuum stirrer until the solid content was 42 wt% and the system was uniform. The negative electrode slurry was uniformly coated on one surface of the negative electrode current collector copper foil with a thickness of 8 pm, and was dried at 85°C to obtain a negative electrode sheet with a single-sided coated negative electrode active material layer (thickness 60 pm). Then, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coated negative electrode active material layer. After cold pressing, cutting, and welding of the negative electrode tabs, a nickel tab, a negative electrode sheet with a size of 74 mm x 1408 mm was obtained for use.

[0115] <Preparation of the separator>

[0116] The separator base film was a polyethylene (PE) with a thickness of 8 pm. An aluminum oxide ceramic layer with a thickness of 2 pm was coated on each of the two surfaces of the separator base film along the thickness direction of the separator base film. Finally, 2.5 mg / cm2of a polytetrafluoroethylene (PTFE) microporous layer was coated on each of the two surfaces of the ceramic layer along the thickness direction of the ceramic layer.2 The binder PVDF is dried to obtain the separator.

[0117] <Preparation of electrolyte>

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

[0119] <Preparation of lithium ion battery>

[0120] The negative electrode sheet, the separator and the positive electrode sheet prepared above are stacked and wound in sequence to obtain an electrode assembly with a winding structure. The electrode assembly is placed in an aluminum plastic film packaging bag, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, capacity, degassing, and edge cutting processes, a lithium ion battery is obtained.

[0121] Among them, as shown in Figure 3 , the surface of the positive 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 end area of the positive electrode sheet 10 are all pasted with adhesive paper 40; as shown in Figure 4 Test methods and equipment: Figure 3 Figure 4 , the surface of the negative tab 23 and the second empty foil area 26 are pasted with adhesive paper 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 pasted with non-ionic adhesive paper 50 (manufacturer: Tadiran Chemical (Shanghai) Co., Ltd., model: T4116BR).

[0122] Examples 1-2 to 1-16

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

[0124] Examples 2-1 to 2-11

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

[0126] Examples 3-1 to 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 example and comparative example are shown in Tables 1 to 3.

[0131] Table 1

[0132]

[0133]

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

[0135] As can be seen from Examples 1-1 to 1-13 and Comparative Examples 1 to 8, the secondary battery of the present application has a mild interface lithium precipitation, a high energy density, and a large adhesive force of the jelly paper, indicating that the secondary battery of the present application can have a high kinetic performance, an energy density, and a low probability of winding off the jelly, by selecting the jelly paper with both the first inert substance with large particles and the second inert substance with small particles in the jelly layer, and controlling the average particle size of the first inert substance and the second inert substance, and the particle number ratio of the first inert substance to the second inert substance within the range of the present application. The secondary battery of the comparative examples has a more serious interface lithium precipitation, or a lower adhesive force of the jelly paper, or a lower energy density of the secondary battery, indicating that the secondary battery of the comparative examples cannot have a high kinetic performance, an energy density, and a low probability of winding off the jelly, by adding only the first inert substance with large particles or the second inert substance with small particles in the jelly 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 particle number ratio of the first inert substance to the second inert substance is not within the range of the present application.

[0136] The average particle size D1 of the first inert substance, the average particle size D2 of the second inert substance, and the ratio D2 / D1 of the two values will generally affect the kinetic performance, energy density, and probability of winding off the jelly of the secondary battery. As can be seen from Examples 1-1 to 1-10 and Comparative Examples 1 to 4, the secondary battery with the average particle size D1 of the first inert substance, the average particle size D2 of the second inert substance, and the ratio D2 / D1 of the two values within the range of the present application has a mild interface lithium precipitation, a high energy density, and a high adhesive force of the jelly paper, indicating that the secondary battery can have a good kinetic performance, a high energy density, and a low probability of winding off the jelly.

[0137] The particle number ratio of the first inert material to the second inert material generally affects the kinetic performance, energy density and winding off-gel probability of the secondary battery. As can be seen from Example 1-1, Example 1-11 to Example 1-13, Comparative Example 5 and Comparative Example 6, the secondary battery selected with the particle number ratio of the first inert material to the second inert material within the range of the present application has a relatively mild interface lithium precipitation, a relatively high energy density and a relatively high adhesive force of the adhesive paper, indicating that the secondary battery can have good kinetic performance, a relatively high energy density and a relatively low winding off-gel probability.

[0138] The average pore size P of the porous substrate and 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 material generally affect the kinetic performance, energy density and winding off-gel probability of the secondary battery. As can be seen from Example 1-1, Example 1-5 to Example 1-7, Example 1-14 to Example 1-16, the secondary battery selected with the average pore size P of the porous substrate and 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 material within the range of the present application is beneficial to control the specific surface area of the porous substrate within a suitable range, increase the adhesion of the particles to the porous substrate and improve the adhesive effect of the porous substrate and the adhesive layer, has a relatively mild interface lithium precipitation, a relatively high energy density and a relatively high adhesive force of the adhesive paper, indicating that the secondary battery can have good kinetic performance, a relatively high energy density and a relatively low winding off-gel probability.

[0139] Table 2

[0140]

[0141]

[0142] The mass ratio of the inert material and the adhesive layer generally affects the kinetic performance, energy density and winding off-gel probability of the secondary battery. As can be seen from Example 1-1, Example 2-1 to Example 2-6, the secondary battery selected with the mass of the inert material and the adhesive layer within the range of the present application has a relatively mild interface lithium precipitation, a relatively high energy density and a relatively high adhesive force of the adhesive paper, indicating that the secondary battery can have good kinetic performance, a relatively high energy density and a relatively low winding off-gel probability.

[0143] The type of inert material generally affects the kinetic performance, energy density and winding off-gel probability of the secondary battery. As can be seen from Example 1-1, Example 2-7 and Example 2-8, the secondary battery selected with the type of inert material within the range of the present application has a relatively mild interface lithium precipitation, a relatively high energy density and a relatively high adhesive force of the adhesive paper, indicating that the secondary battery can have good kinetic performance, a relatively high energy density and a relatively low winding off-gel probability.

[0144] The type of adhesive layer bonding generally affects the kinetic performance, energy density and winding off adhesive probability of the secondary battery. As can be seen from Example 1-1, Example 2-9 to Example 2-11, the secondary battery selected with the type of adhesive layer bonding within the scope of the present application has a lighter interface lithium stripping, higher energy density, and higher adhesive force of the adhesive paper, indicating that the secondary battery can have good kinetic performance, higher energy density and lower winding off adhesive probability.

[0145] Table 3

[0146]

[0147]

[0148] The porosity of the porous substrate generally affects the kinetic performance, energy density and winding off adhesive probability of the secondary battery. As can be seen from Example 1-1, Example 3-1 to Example 3-4, the secondary battery selected with the porosity of the porous substrate within the scope of the present application is beneficial to maintain the air permeability of the adhesive paper within a suitable range, and is not prone to interface problems, has a lighter interface lithium stripping, higher energy density, and higher adhesive force of the adhesive paper, indicating that the secondary battery can have good kinetic performance, higher energy density and lower winding off adhesive probability.

[0149] The thickness of the porous substrate generally affects the kinetic performance, energy density and winding off adhesive probability of the secondary battery. As can be seen from Example 1-1, Example 3-5 to Example 3-10, the secondary battery selected with the thickness of the porous substrate within the scope of the present application has a lighter interface lithium stripping, higher energy density, and higher adhesive force of the adhesive paper, indicating that the secondary battery can have good kinetic performance, higher energy density and lower winding off adhesive probability.

[0150] The thickness of the adhesive layer generally affects the kinetic performance, energy density and winding off adhesive probability of the secondary battery. As can be seen from Example 1-1, Example 3-11 to Example 3-16, the secondary battery selected with the thickness of the adhesive layer within the scope of the present application is beneficial to maintain the air permeability of the adhesive paper within a suitable range and maintain good bonding strength, has a lighter interface lithium stripping, higher energy density, and higher adhesive force of the adhesive paper, indicating that the secondary battery can have good kinetic performance, higher energy density and lower winding off adhesive probability.

[0151] It is to be noted that, in the present document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0152] Various embodiments are described herein with reference to particular applications with a specific configuration and contents for convenience. It is to be understood that the application is not limited to those embodiments but cover any technical equivalents in principle as far as they are within the scope of a patent protection. The same or similar parts or features between the embodiments are designated by the same reference numerals, and repeated explanation thereof is omitted.

[0153] The preferred embodiments of the present application have been disclosed herein and obviously many modifications and alterations will occur to those skilled in the art. Therefore, it is the intention that the preferred embodiments be taken as illustrative only and not as limiting the present application. It is intended to fall within the scope of the appended claims and their equivalents.

Claims

1.A secondary battery, comprising a gum paper, a positive electrode tab, a negative electrode tab, and a separator disposed between the positive electrode tab and the negative electrode tab, the positive electrode tab comprising a positive electrode tab, the gum paper being interposed between the separator and the positive electrode tab, the gum paper comprising a porous substrate and a gum layer disposed on at least one surface of the porous substrate; wherein the gum layer comprises inert substances, the inert substances comprising a first inert substance and a second inert substance, the first inert substance having a particle size of d1 nm, the second inert substance having a particle size of d2 nm, and 300 < d1 ≤ 900, 50 ≤ d2 ≤ 300; the first inert substance having an average particle size of D1 nm, the second inert substance having an average particle size of D2 nm, and 400 ≤ D1 ≤ 800, 100 ≤ D2 ≤ 200; in any region of the surface of the gum layer, the particle number ratio of the first inert substance to the second inert substance is 3:7 to 7:3; the porous substrate having an average pore size of P nm; D2 and P satisfy the following relationship: 0.5 ≤ P / D2 ≤ 1. 1 / 7 ≤ D2 / D1 ≤ 1 / 3; the gum layer comprising a gum layer binder, the mass ratio of the inert substances to the gum layer binder being 3:7 to 7:3; the gum paper having a gas permeability of 180 s / 100 mL to 600 s / 100 mL; the porous substrate having a porosity of 25% to 55%; the porous substrate having a thickness of 9 μm to 24 μm; the gum layer having a thickness of 2 μm to 6 μm; and the secondary battery satisfying 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 substances to the gum 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 gum layer is 3 μm to 5 μm. the inert substances comprising at least one of boehmite, diaspore, halloysite, or quartz sand; the gum layer binder comprising 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; the positive electrode tab comprising a positive electrode active material layer and a positive electrode current collector, the positive electrode current collector comprising opposite first and second surfaces, the positive electrode active material layer being disposed on at least the first surface of the positive electrode current collector, the positive electrode active material layer having a first recess exposing the positive electrode current collector, the positive electrode tab being disposed in the first recess and connected to the positive electrode current collector, and the second surface comprising a first empty foil region opposite the first recess; and the gum paper being attached to at least one of the surface of the positive electrode tab, the first empty foil region, the surface of the negative electrode tab adjacent to the first recess, the surface of the negative electrode tab adjacent to the first empty foil region, or an end region of the positive electrode tab. ​ ​ ​ ​ ​ 2. The secondary battery according to claim 1, wherein ​ 3. The secondary battery according to claim 1, wherein 50≤P≤200。 4. The secondary battery according to claim 1, wherein ​ 5. The secondary battery according to claim 4, wherein ​ 6. The secondary battery according to any one of claims 1 to 5, wherein ​ 7. The secondary battery according to claim 4, wherein ​ 8. The secondary battery according to claim 7, wherein ​ 9. The secondary battery according to claim 8, wherein ​ ​ ​ ​ ​ ​ 10. The secondary battery according to any one of claims 1 to 5, wherein ​ 11. The secondary battery according to any one of claims 1 to 5, wherein ​ 12. The secondary battery according to any one of claims 1 to 5, wherein ​ ​ 13. The secondary battery according to any one of claims 1 to 5, wherein The negative electrode tab includes a negative electrode current collector, a negative electrode active material layer, and a negative electrode tab, the negative electrode current collector includes opposite third and fourth surfaces, the negative electrode active material layer is disposed on at least the third surface of the negative electrode current collector, the negative electrode active material layer has a second recess exposing the negative electrode current collector, the negative electrode tab is disposed in the second recess and connected to the negative electrode current collector, and the fourth surface includes a second empty foil area opposite the second recess. The adhesive tape is attached to at least one of a surface of the negative electrode tab or the second empty foil area. 14.An electronic device comprising the secondary battery of any one of claims 1 to 13.

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