Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device. The electrochemical device comprises an insulating layer, a positive electrode sheet, a negative electrode sheet and a separator provided between the positive electrode sheet and the negative electrode sheet, the insulating layer comprising a porous substrate, the porous substrate comprising polypropylene, and the surface density of the porous substrate being 2 g / m2 to 11 g / m2. The described arrangements enable the electrochemical device to have a high capacity.

Description

Electrochemical device and electronic device

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of the State Intellectual Property Office of China on March 31, 2024, with application number 202410383464.9 and invention name “An electrochemical device and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Art

[0003] Electrochemical devices, such as lithium-ion batteries, offer advantages such as high energy density, long cycle life, low self-discharge, and environmental friendliness. They are widely used in aviation, aerospace, marine, and electric vehicles. Lithium-ion batteries consist of a positive electrode, a negative electrode, a separator, and adhesive tape. In existing lithium-ion batteries, the adhesive tape area cannot fully utilize the battery's capacity, resulting in a loss of capacity. Summary of the Invention

[0004] The purpose of the present application is to provide an electrochemical device and an electronic device to increase the capacity of the electrochemical device.

[0005] It should be noted that in the invention content of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0006] The first aspect of the present application provides an electrochemical device, the electrochemical device comprising an insulating layer, a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprising a positive electrode tab, the insulating layer being between the separator and the positive electrode tab, or the insulating layer being between the separator and the positive electrode sheet tail region; the insulating layer comprising a porous substrate comprising polypropylene, the surface density of the porous substrate being 2 g / m 2 Up to 11g / m 2 By selecting a porous substrate comprising polypropylene and regulating the surface density of the porous substrate within the aforementioned range, the present application provides the insulating layer with excellent ion conductivity. In the areas of the positive and negative electrode sheets covered by the insulating layer, lithium ions can freely and rapidly shuttle through them, as in areas not covered with adhesive tape, thereby fully utilizing the capacity of the positive and negative active materials in the covered areas. This increases the effective area of ​​the positive and negative active material layers, and improves the capacity of the electrochemical device.

[0007] In some embodiments of the present application, the area density of the porous substrate is 3 g / m 2 Up to 11g / m 2While increasing the capacity of the electrochemical device, it reduces the risk of short circuit and further improves the safety performance of the electrochemical device.

[0008] In some embodiments of the present application, a glue layer is provided on one surface of a porous substrate, the glue layer comprising a polymer and inorganic particles; the polymer has a glass transition temperature of -30°C to -10°C and comprises polyacrylate; the inorganic particles comprise at least one of boehmite, aluminum oxide, titanium dioxide, magnesium oxide, zirconium oxide, or zinc oxide; based on the mass of the glue layer, the mass percentage of the polymer is 30% to 95%, and the mass percentage of the inorganic particles is 5% to 70%. By selecting a polymer having a glass transition temperature within the above range and inorganic particles having the above range, and regulating the mass percentages of the polymer and inorganic particles in the glue layer within the above range, and adjusting the fluid properties such as slurry viscosity and cohesion, the glue layer shrinks on the surface of the release film to form pores, exposing the porous substrate, thereby enabling the electrochemical device to have a higher capacity without affecting its safety performance.

[0009] In some embodiments of the present application, the adhesive layer has holes, and part of the porous substrate is exposed from the holes of the adhesive layer, thereby further improving the ion-conducting function of the insulating layer and increasing the capacity of the electrochemical device.

[0010] In some embodiments of the present application, the longitudinal tensile strength of the porous substrate is 1000 kgf / cm 2 Up to 2000kgf / cm 2 , the transverse tensile strength of the porous substrate is 300kgf / cm 2 Up to 600kgf / cm 2 The probability of deformation of the insulating layer along the lateral and longitudinal directions of the porous substrate is reduced, and the risk of exposure of the area covered by the insulating layer due to deformation of the insulating layer is reduced, so that the electrochemical device can have higher safety performance while having higher capacity.

[0011] In some embodiments of the present application, the thickness of the insulating layer is 8 μm to 30 μm, which can reduce the possibility of burrs on the positive electrode plate in the electrochemical device passing through the insulating layer to contact the negative electrode plate or burrs on the negative electrode plate passing through the insulating layer to contact the positive electrode plate.

[0012] In some embodiments of the present application, the thickness of the insulating layer is 8 μm to 17 μm. The electrochemical device has higher safety performance and energy density based on higher capacity.

[0013] In some embodiments of the present application, the thickness of the porous substrate is 8 μm to 20 μm. By controlling the thickness of the porous substrate within the above range, the electrochemical device has good safety performance, a thinner thickness, and a higher volume energy density.

[0014] In some embodiments of the present application, the melting temperature of the porous substrate is 165° C. to 175° C. This enables the electrochemical device to have higher safety performance on the basis of higher capacity.

[0015] In some embodiments of the present application, the Dv50 of the inorganic particles is 80 nm to 1000 nm. By regulating the Dv50 of the inorganic particles within the above range, the electrochemical device can have a higher capacity and good safety performance.

[0016] In some embodiments of the present application, a positive electrode sheet includes a positive current collector and a positive active material layer. The positive current collector includes a first surface and a second surface that oppose each other. The positive active material layer is disposed at least on the first surface of the positive current collector. A first recess is disposed in the positive active material layer, exposing the positive current collector. The positive electrode tab is disposed within the first recess and connected to the positive current collector. The second surface includes a first hollow foil region opposing the first recess. An insulating layer is adhered to at least one of the following: the surface of the positive tab, the first hollow foil region, the surface of the negative electrode sheet adjacent to the first recess, the surface of the negative electrode sheet adjacent to the first hollow foil region, or the positive electrode sheet tail region. Adhering the insulating layer to the aforementioned locations can enable the electrochemical device to have a higher energy density and better safety performance.

[0017] In some embodiments of the present application, a negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer, and a negative electrode tab. The negative electrode current collector includes opposing third and fourth surfaces. The negative electrode active material layer is disposed at least on the third surface of the negative electrode current collector. A second recess is disposed in the negative electrode active material layer, exposing the negative electrode current collector. The negative electrode tab is disposed within the second recess and connected to the negative electrode current collector. The fourth surface includes a second hollow foil region opposing the second recess. An insulating layer is attached to at least one of the surface of the negative electrode tab or the second hollow foil region. Attaching the insulating layer to these locations can enable the electrochemical device to have a higher energy density and better safety performance.

[0018] A second aspect of the present application provides an electronic device, which includes the electrochemical device described in any one of the aforementioned embodiments. Therefore, the electronic device has good performance.

[0019] Beneficial effects of this application:

[0020] The present application provides an electrochemical device and an electronic device. By selecting a porous substrate comprising polypropylene and controlling the surface density of the porous substrate within the aforementioned range, the electrochemical device provides an insulating layer with excellent ion conductivity. Lithium ions can freely and rapidly shuttle through the areas of the positive and negative electrode sheets covered by the insulating layer, as they do in areas not covered with adhesive tape, thereby fully utilizing the capacity of the positive and negative active materials in the covered areas. This increases the effective area of ​​the positive and negative active material layers, thereby improving the capacity of the electrochemical device.

[0021] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0023] FIG1 is a schematic diagram of a cross-sectional structure of an insulating layer along its thickness direction and longitudinal direction according to some embodiments of the present application;

[0024] FIG2 is a schematic diagram of the cross-sectional structure of the insulating layer along its thickness direction and longitudinal direction according to other embodiments of the present application;

[0025] FIG3 is a schematic diagram of a positive electrode tab adhered to an insulating layer in some embodiments of the present application;

[0026] FIG4 is a morphology image of the surface of the insulating layer according to some embodiments of the present application under a scanning electron microscope (SEM);

[0027] Figure 5 is an enlarged view of Figure 4;

[0028] FIG6 is an enlarged view of FIG4;

[0029] FIG7 is a schematic diagram showing the position of an insulating layer in some embodiments of the present application;

[0030] FIG8 is a schematic diagram showing the position of the insulating layer in some other embodiments of the present application.

[0031] Figure markings: 10-positive electrode sheet; 11-positive electrode current collector; 12-positive electrode active material layer; 13-positive electrode tab; 11a-first surface; 11b-second surface; 15-first groove; 16-first empty foil area; 20-negative electrode sheet; 21-negative electrode current collector; 22-negative electrode active material layer; 23-negative electrode tab; 25-second groove; 26-second empty foil area; 21c-third surface; 21d-fourth surface; 30-separator; 40-insulating layer; 41-porous substrate; 42-glue layer; 50-non-ion-conducting insulating layer. DETAILED DESCRIPTION

[0032] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0033] It should be noted that, in the specific embodiments of the present application, a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium-ion battery.

[0034] The first aspect of the present application provides an electrochemical device, the electrochemical device comprising an insulating layer, a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprising a positive electrode tab, the insulating layer being between the separator and the positive electrode tab, or the insulating layer being between the separator and the positive electrode sheet tail region; the insulating layer comprising a porous substrate comprising polypropylene, the surface density of the porous substrate being 2 g / m 2 Up to 11g / m 2 .

[0035] In some embodiments of the present application, the area density of the porous substrate is 2 g / m 2 , 3g / m 2 , 4g / m 2 , 5g / m 2 , 6g / m 2 , 7g / m 2 , 8g / m 2 , 9g / m 2 , 10g / m 2 , 11g / m 2 Or any value between any two numerical ranges mentioned above. The surface density of the porous substrate is less than 2g / m 2 The surface density of the porous substrate is too small, and the polypropylene content in the porous substrate is very low, resulting in low transverse and longitudinal tensile strength of the porous substrate. During the manufacturing process of the electrochemical device, the roller tension cannot be met and the belt is easily broken. If the thickness of the porous substrate is constant, its surface density is less than 2g / m2 , the surface density is too small, based on the existing process, it may not be possible to prepare a porous substrate; if the process development can prepare a porous substrate, there are too many pores in the porous substrate. When the adhesive layer slurry is coated on the porous substrate, the adhesive layer slurry can easily enter the pores of the porous substrate, affecting the speed and number of lithium ions shuttling from the insulating layer, thereby affecting the performance of the active material covered by the insulating layer, reducing the capacity of the electrochemical device, and causing lithium precipitation in the negative electrode. The surface density of the porous substrate is greater than 11g / m 2 If the surface density of the porous substrate is too large and the pores in the porous substrate are too few, the ion conductivity of the insulating layer will be poor, and the speed and number of lithium ion shuttles in the area covered by the insulating layer will be greatly reduced, which will reduce the capacity of the electrochemical device. 2 Up to 11g / m 2 , while ensuring the increase in capacity, the risk of short circuit is further reduced.

[0036] Overall, by selecting a porous substrate comprising polypropylene and controlling the surface density of the porous substrate within the aforementioned range, the present invention provides the insulating layer with excellent ion conductivity. Lithium ions can freely and rapidly travel through the areas of the positive and negative electrode sheets where the insulating layer is applied, just as they do in areas where the tape is not applied. This allows the full utilization of the capacity of the positive and negative active materials in the areas covered by the insulating layer. This increases the effective area of ​​the positive and negative active material layers, thereby improving the capacity of the electrochemical device.

[0037] The present application has no particular restrictions on the method of regulating the surface density 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 thickness and porosity of the porous substrate. More specifically, it is achieved by controlling the stretching multiple (2 to 10 times), heating temperature (100°C to 140°C), etc. when the porous substrate is prepared. Generally, when the porosity of the porous substrate is constant, the thicker the thickness of the porous substrate, the greater the surface density of the porous substrate; the thinner the thickness of the porous substrate, the smaller the surface density of the porous substrate. When the thickness of the porous substrate is constant, the smaller the porosity of the porous substrate, the greater the surface density of the porous substrate; the greater the porosity of the porous substrate, the smaller the surface density of the porous substrate.

[0038] For ease of understanding, it should be noted that in the present application, as shown in Figures 1 to 3, when the insulating layer 40 is attached to the positive electrode tab 10, the longitudinal direction X of the porous substrate 41 is parallel to the extension direction of the positive electrode tab 13, the transverse direction Y of the porous substrate 41 is perpendicular to the extension direction of the positive electrode tab 13, and the thickness direction Z of the porous substrate 41 is perpendicular to the transverse direction Y and the longitudinal direction X of the porous substrate 41. In some embodiments, as shown in Figure 1, the insulating layer 40 includes a porous substrate 41, and the thickness of the insulating layer 40 is T 40In other embodiments, as shown in FIG2 , the insulating layer 40 includes a porous substrate 41 and a glue layer 42 disposed on one surface of the porous substrate 41 . The thickness of the insulating layer 40 is T 40 As shown. It is understood that the adhesive layer 42 can also be provided on the other surface of the porous substrate 41. In this application, when the insulating layer is provided with an adhesive layer, the thickness of the insulating layer is the sum of the thickness of the porous substrate and the adhesive layer; when the insulating layer is not provided with an adhesive layer, the thickness of the insulating layer is the thickness of the porous substrate.

[0039] In some embodiments of the present application, as shown in Figure 2, a subbing layer 42 is disposed on one surface of a porous substrate 41. In other embodiments, the subbing layer 42 may be disposed on another surface of the porous substrate 41. The subbing layer comprises a polymer and inorganic particles; the polymer has a glass transition temperature of -30°C to -10°C, and the polymer comprises a polyacrylate. The polyacrylate includes, but is not limited to, a homopolymer or copolymer formed from at least one of the following monomers: methyl acrylate, ethyl acrylate, and butyl acrylate. The inorganic particles comprise at least one of boehmite, aluminum oxide, titanium dioxide, magnesium oxide, zirconium oxide, or zinc oxide. Based on the mass of the subbing layer, the mass percentage of the polymer is 30% to 95%, and the mass percentage of the inorganic particles is 5% to 70%. For example, the glass transition temperature of the polymer is -30°C, -25°C, -20°C, -16°C, -10°C, or any value between any two of the aforementioned ranges. For example, the mass percentage of the high molecular weight polymer is 30%, 40%, 45%, 50%, 60%, 70%, 80%, 88%, 95%, or any value between any two of the above numerical ranges. For example, the mass percentage of the inorganic particles is 5%, 15%, 22%, 30%, 35%, 40%, 50%, 58%, 63%, 70%, or any value between any two of the above numerical ranges. A high molecular weight polymer with a glass transition temperature within the above range is selected for use in the adhesive layer of the insulating layer. The adhesive layer does not require hot pressing and can have good adhesion at room temperature. By selecting the above-mentioned types of high molecular weight polymers with a glass transition temperature within the above-mentioned range, selecting the above-mentioned types of inorganic particles, and regulating the mass percentages of the high molecular weight polymer and inorganic particles in the adhesive layer within the above-mentioned range, the prepared adhesive layer can have good adhesion, and can have good adhesion between the adhesive layer and the porous substrate, and between the adhesive layer and the positive and negative electrodes. Therefore, the adhesive layer is attached to the positive electrode sheet or the negative electrode sheet, which can provide good protection for the positive electrode sheet and the negative electrode sheet, reducing the probability of short circuit caused by contact between the positive electrode sheet and the negative electrode sheet. In addition, the arrangement of inorganic particles in the adhesive layer can create pores in the adhesive layer, which is conducive to the shuttle of lithium ions from the adhesive layer, so that the capacity of the positive and negative active materials in the area covered by the insulating layer can be fully utilized while playing the role of adhesion. In this way, the electrochemical device can have a higher capacity without affecting its safety performance. The "glass transition temperature" in this application is the glass transition temperature well known in the art.

[0040] In some embodiments of the present application, the inorganic particles are boehmite. Based on the mass of the subbing layer, the mass percentage of the high molecular weight polymer is 30% to 60%, and the mass percentage of the inorganic particles is 40% to 70%. For example, the mass percentage of the high molecular weight polymer is 30%, 40%, 45%, 50%, 60%, or any value between any two of the aforementioned numerical ranges. For example, the mass percentage of the inorganic particles is 40%, 50%, 58%, 63%, 70%, or any value between any two of the aforementioned numerical ranges.

[0041] In some embodiments of the present application, the adhesive layer has holes, and a portion of the porous substrate is exposed through the holes in the adhesive layer. In this case, the pore size of the holes in the adhesive layer is larger than the pore size of the porous substrate, thereby further improving the ion conductivity of the insulating layer and increasing the capacity of the electrochemical device. Figure 4 shows the morphology of the insulating layer surface under SEM in some embodiments. The adhesive layer 42 has multiple holes, and a portion of the porous substrate 41 is exposed through the holes in the adhesive layer 42. Figure 5 is an enlarged view of Figure 4. As can be seen from Figure 5, there are multiple small holes in the porous substrate 41, and the pore size of the holes in the adhesive layer 42 is larger than the small holes in the porous substrate 41. Figure 6 is a partial enlarged view of the adhesive layer 42 in Figure 4. As can be seen from Figure 6, there are multiple inorganic particles on the adhesive layer 42.

[0042] In some embodiments of the present application, the longitudinal tensile strength of the porous substrate is 1000 kgf / cm 2 Up to 2000kgf / cm 2 , the transverse tensile strength of the porous substrate is 300kgf / cm 2 Up to 600kgf / cm 2 For example, the longitudinal tensile strength of a porous substrate is 1000 kgf / cm 2 、1100kgf / cm 2 、1200kgf / cm 2 、1330kgf / cm 2 、1450kgf / cm 2 、1600kgf / cm 2 、1700kgf / cm 2 、1820kgf / cm 2 、1900kgf / cm 2 、2000kgf / cm 2 Or any value between any two numerical ranges mentioned above. For example, the transverse tensile strength of the porous substrate is 300 kgf / cm 2 、360kgf / cm 2 、410kgf / cm 2 、500kgf / cm 2 、560kgf / cm 2 、600kgf / cm2 Or any value between any two of the above numerical ranges. The longitudinal tensile strength and transverse tensile strength of the porous substrate are within the above ranges. The porous substrate has both high longitudinal tensile strength and transverse tensile strength. Thus, during the preparation of the insulating layer, during the process of attaching the insulating layer to the positive and negative electrode sheets, or during the preparation of the electrochemical device after the insulating layer is attached, the probability of the insulating layer being deformed and stretched into a long strip or dumbbell shape is low, and the risk of the location where the insulating layer is attached being exposed due to deformation of the insulating layer is low, thereby reducing the risk of the positive and negative electrodes contacting and causing a short circuit in the electrochemical device. As a result, the electrochemical device can have higher safety performance while having a higher capacity.

[0043] The present application does not particularly limit the method for regulating the longitudinal tensile strength and transverse tensile strength of the porous substrate, as long as the objectives of the present application can be achieved. For example, this can be achieved by regulating the molecular weight and crystallinity of the porous substrate raw material, or by regulating the stretching process parameters of the porous substrate manufacturing equipment.

[0044] In some embodiments of the present application, the thickness of the insulating layer is 8 μm to 30 μm. For example, the thickness of the insulating layer is 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 21 μm, 24 μm, 26 μm, 28 μm, 30 μm, or any value between any two of the above numerical ranges. The thickness of the insulating layer is within the above range, which is beneficial to reducing the possibility of burrs in the positive electrode sheet passing through the insulating layer to contact the negative electrode sheet or burrs in the negative electrode sheet passing through the insulating layer to contact the positive electrode sheet, so as to reduce the risk of short circuit caused by contact between the positive and negative electrodes of the electrochemical device, thereby improving the safety performance of the electrochemical device; it is also beneficial to make the electrochemical device have a smaller volume, so as to reduce the loss of energy density caused by the electrochemical device due to excessive volume, and the path for lithium ions to shuttle from the insulating layer is shorter, and the lithium ions have a higher transmission speed, so that the electrochemical device has good cycle performance and kinetic performance.

[0045] In some embodiments of the present application, the thickness of the insulating layer is 8 μm to 17 μm. For example, the thickness of the insulating layer is 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm or any value between any two of the above numerical ranges. By regulating the thickness of the insulating layer within the above range, it is possible to reduce the possibility of burrs on the positive electrode sheet in the electrochemical device passing through the insulating layer and contacting the negative electrode sheet, or burrs on the negative electrode sheet passing through the insulating layer and contacting the positive electrode sheet without increasing the volume of the electrochemical device, thereby reducing the possibility of energy density loss due to increased volume of the electrochemical device. As a result, the electrochemical device has higher safety performance and energy density on the basis of higher capacity.

[0046] In some embodiments of the present application, as shown in FIG. 2 , the thickness T of the porous substrate 41 is 41 8μm to 20μm. For example, the thickness of the porous substrate is 8μm, 11μm, 13μm, 15μm, 17μm, 18μm, 20μm or any value between any two of the above numerical ranges. By regulating the thickness of the porous substrate within the above range, the possibility of the burrs in the positive electrode sheet passing through the insulating layer to contact the negative electrode sheet or the burrs in the negative electrode sheet passing through the insulating layer to contact the positive electrode sheet can be reduced, and the lithium ions in the area covered by the insulating layer can be freely shuttled, so that the capacity of the active material can be fully utilized and the effective area of ​​the positive and negative active material layers can be increased. As a result, the electrochemical device has a thinner thickness and a higher volume energy density without affecting its safety performance.

[0047] In some embodiments of the present application, the melting temperature of the porous substrate is 165°C to 175°C. For example, the melting temperature of the porous substrate is 165°C, 166°C, 167°C, 168°C, 169°C, 170°C, 171°C, 172°C, 173°C, 174°C, 175°C or any value between any two of the above numerical ranges. The melting temperature of the porous substrate is within the above range, and the raw material particles for preparing the porous substrate have a suitable degree of crystallinity, so that the porous substrate has a higher strength, and the porous substrate is applied to the electrochemical device. When the electrochemical device is in a high temperature state, the porous substrate is prone to melting, resulting in a lower risk of short circuit in the electrochemical device. As a result, the electrochemical device can have higher safety performance on the basis of having a higher capacity.

[0048] The present application does not particularly limit the method for controlling the melting temperature of the porous substrate, as long as the purpose of the present application can be achieved. For example, this can be achieved by controlling the crystallinity and molecular weight of the raw material of the porous substrate.

[0049] The present application has no particular limitation on the weight average molecular weight of the above-mentioned high molecular weight polymer, as long as the purpose of the present application can be achieved.

[0050] In some embodiments of the present application, as shown in FIG. 2 , the thickness T of the adhesive layer 42 is 42 The thickness of the adhesive layer is 1 μm to 8 μm. For example, the thickness of the adhesive layer is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or any value between any two of the above ranges. By regulating the thickness of the adhesive layer within the above range, the insulating layer has a relatively small thickness while maintaining good adhesion, thereby reducing the probability of the energy density of the electrochemical device being compromised due to a thick insulating layer. Furthermore, lithium ions can flow better through the adhesive layer. This allows the electrochemical device to have a higher capacity.

[0051] In some embodiments of the present application, the Dv50 of the inorganic particles is 80nm to 1000nm. For example, the Dv50 of the inorganic particles is 80nm, 100nm, 200nm, 230nm, 300nm, 400nm, 480nm, 520nm, 600nm, 660nm, 780nm, 810nm, 900nm, 1000nm or any value between any two of the above numerical ranges. By regulating the Dv50 of the inorganic particles within the above range, the inorganic particles can be evenly distributed in the adhesive layer slurry. When the adhesive layer slurry is coated on the surface of the porous substrate, the probability of the inorganic particles entering the pores of the porous substrate is small, and the probability of reducing the porosity of the porous substrate is low, thereby making the insulating layer have good ion conductivity and good adhesion. In this way, the insulating layer is applied to the electrochemical device, which can make the electrochemical device have a higher capacity and good safety performance.

[0052] In the present application, "Dv50" refers to the particle size at which the cumulative volume of inorganic particles reaches 50% from the smallest particle size side in the volume-based particle size distribution of inorganic particles.

[0053] The present application does not particularly limit the method for regulating the Dv50 of the inorganic particles, as long as the objectives of the present application can be achieved. For example, this can be achieved through crushing or screening. Alternatively, the Dv50 of the inorganic particles can be determined by purchasing commercially available inorganic particles and combining them with the testing method described in "Testing Dv50 of Inorganic Particles" in this application to select inorganic particles with the desired Dv50.

[0054] For ease of understanding, it is defined that when the electrode sheet is unfolded, the length direction of the positive electrode sheet itself is the same as the lateral direction of the insulating layer, the width direction of the positive electrode sheet itself is the same as the longitudinal direction of the insulating layer, and the thickness direction of the positive electrode sheet itself is the same as the thickness direction of the insulating layer. It can be understood that the length direction, width direction and thickness direction of the positive electrode collector, positive electrode active material layer, negative electrode sheet and separator are the same as those of the positive electrode sheet.

[0055] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector, a positive electrode active material layer, and a positive electrode tab. The positive electrode current collector includes a first surface and a second surface opposite to each other. The positive electrode active material layer is at least disposed on the first surface of the positive electrode current collector. A first groove exposing the positive electrode current collector is provided in the positive electrode active material layer. The positive electrode tab is disposed in the first groove and connected to the positive electrode current collector. The second surface includes a first hollow foil area opposite the first groove. The insulating layer is adhered to at least one of the surface of the positive electrode tab, the first hollow foil area, the surface of the negative electrode sheet adjacent to the first groove, the surface of the negative electrode sheet adjacent to the first hollow foil area, or the tail area of ​​the positive electrode sheet. The above-mentioned "the positive electrode active material layer is at least disposed on 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. In other embodiments, the positive electrode active material layer is disposed on both the first surface and the second surface of the positive electrode current collector. The "first surface" and the "second surface" may be partial or entire surfaces of the positive electrode collector. It should be noted that the negative electrode sheet in the "negative electrode sheet surface adjacent to the first groove" and the negative electrode sheet in the "negative electrode sheet surface adjacent to the first empty foil area" are not the same layer of negative electrode sheets, but two layers of negative electrode sheets adjacent to the positive electrode sheets respectively. The above-mentioned "two layers of negative electrode sheets" can be two negative electrode sheets, or two layers formed by winding a negative electrode sheet. As shown in Figure 7, the separator 30 is located between the positive electrode sheet 10 and the negative electrode sheet 20. The positive electrode sheet 10 includes a positive electrode collector 11, a positive electrode active material layer 12 and a positive electrode tab 13. The positive electrode collector 11 includes a first surface 11a and a second surface 11b opposite to each other along its own thickness direction Z. The positive electrode active material layer 12 is arranged on the first surface 11a of the positive electrode collector 11 and is also arranged on the second surface 11b of the positive electrode collector 11. A first groove 15 exposing the positive electrode collector 11 is provided in the positive electrode active material layer 12 arranged on the first surface 11a. The positive electrode tab 13 is arranged in the first groove 15 and is connected to the positive electrode collector 11. The second surface 11b includes a first empty foil area 16 opposite to the first groove 15. The insulating layer 40 is respectively adhered to the surface of the positive electrode tab 13, the first hollow 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 hollow foil area 16, and the tail area of ​​the positive electrode sheet 10. Typically, along the length direction Y of the positive electrode sheet 10, the length of the insulating layer 40 adhered to the surface of the positive electrode tab 13 and the first hollow foil area 16 is greater than the length of the insulating layer 40 adhered to the surface of the negative electrode sheet 20 adjacent to the first groove 15 and the surface of the negative electrode sheet 20 adjacent to the first hollow foil area 16.Pasting the insulating layer on the surface of the positive electrode tab and the surface of the negative electrode sheet adjacent to the first groove can reduce the probability of the burrs of the positive electrode tab penetrating the negative electrode active material layer and contacting the negative electrode current collector, thereby causing a short circuit. Pasting the insulating layer on the surface of the positive electrode tab in the area covered by the positive electrode active material layer allows lithium ions to be released normally, and the released lithium ions can also be normally embedded in the relative negative electrode active material layer, thereby reducing capacity waste and the probability of lithium plating. Pasting the insulating layer on the first empty foil area and the surface of the negative electrode sheet adjacent to the first empty foil area can reduce the probability of the burrs in the first empty foil area penetrating the negative electrode active material layer and contacting the negative electrode current collector, thereby causing a short circuit. Pasting the insulating layer on the area covered by the positive electrode active material layer in the first empty foil area allows lithium ions to be released normally, and the released lithium ions can also be normally embedded in the relative negative electrode active material layer, thereby reducing capacity waste and the probability of lithium plating. Pasting the insulating layer on the tail area of ​​the positive electrode sheet can reduce the probability of contact between the positive electrode current collector and the negative electrode sheet. Therefore, by sticking the insulating layer at the above-mentioned different positions, lithium ions in the area covered by the insulating layer can freely shuttle to exert the capacity of the active material, and can also reduce the risk of short circuit caused by contact between the positive and negative electrodes, thereby making the electrochemical device have higher energy density and good safety performance.

[0056] In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer, and a negative electrode tab. The negative electrode current collector includes opposing third and fourth surfaces. The negative electrode active material layer is disposed at least on the third surface of the negative electrode current collector. A second recess is disposed in the negative electrode active material layer, exposing the negative electrode current collector. The negative electrode tab is disposed within the second recess and connected to the negative electrode current collector. The fourth surface includes a second hollow foil region opposing the second recess. An insulating layer is adhered to at least one of the negative electrode tab surface and the second hollow foil region. The phrase "the negative electrode active material layer is disposed at least on 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. 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 8, the separator 30 is positioned between the positive electrode sheet 10 and the negative electrode sheet 20. The negative electrode sheet 20 includes a negative current collector 21, a negative active material layer 22, and a negative electrode tab 23. The negative electrode current collector 21 includes a third surface 21c and a fourth surface 21d that are opposed to each other along its thickness direction Z. The negative active material layer 22 is disposed on the third surface 21c and the fourth surface 21d of the negative electrode current collector 21. A second recess 25 is provided in the negative active material layer 22 on the third surface 21c, exposing the negative electrode current collector 21. The negative electrode tab 23 is disposed within the second recess 25 and connected to the negative electrode current collector 21. The fourth surface 21d includes a second hollow foil area 26 that is opposite the second recess 25. An insulating layer 40 is adhered to the surface of the negative electrode tab 23 and the second hollow foil area 26. A non-ion-conductive insulating layer 50 is adhered to the surface of the positive electrode sheet 10 adjacent to the second recess 25 and the surface of the positive electrode sheet 10 adjacent to the second hollow foil area 26. Adhering the insulating layer 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 insulating layer, increase the lithium ion embedding sites, and increase the capacity of the negative electrode active material layer, thereby making the electrochemical device have a higher energy density.

[0057] The present application has no particular limitation on the type of the non-ion-conducting insulating layer. A non-ion-conducting insulating layer known in the art may be selected as needed, as long as the purpose of the present application can be achieved.

[0058] The present application does not particularly limit the type of positive electrode current collector, as long as it can achieve the purpose of the present application. For example, the positive electrode current collector can include aluminum foil, aluminum alloy foil, etc.

[0059] The present application has no special restrictions on the positive electrode active material layer, as long as the purpose of the present application can be achieved. In one embodiment of the present application, the positive electrode active material layer includes a positive electrode active material. The present application has no special restrictions on the type of positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. Optionally, the positive electrode active material layer also includes a positive electrode conductor and a positive electrode binder. The present application has no special restrictions on the types of positive electrode conductors and positive electrode binders in the positive electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no special restrictions on the mass ratio of the positive electrode active material, positive electrode conductor and positive electrode binder in the positive electrode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.

[0060] The thickness of the positive electrode current collector and the positive electrode active material layer is not particularly limited in this application, as long as the purpose of this 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.

[0061] The present application has no particular limitation on the negative electrode current collector, as long as it can achieve the purpose of the present application. For example, the negative electrode current collector can include copper foil, copper alloy foil, nickel foil, titanium foil, nickel foam, or copper foam.

[0062] The present application has no particular restrictions on the negative electrode active material layer, as long as the purpose of the present application can be achieved. In one embodiment of the present application, the negative electrode active material layer includes a negative electrode active material. The present application has no particular restrictions on the type of negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microbeads, tin-based materials, silicon-based materials, lithium titanate, transition metal nitrides or natural flake graphite. Optionally, the negative electrode active material layer also includes at least one of a negative electrode conductor, a thickener, and a negative electrode binder. The present application has no particular restrictions on the types of negative electrode conductors, thickeners and negative electrode binders in the negative electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the mass ratio of the negative electrode active material, negative electrode conductor, thickener and negative electrode binder in the negative electrode active material layer, as long as the purpose of the present application can be achieved.

[0063] The thickness of the negative electrode current collector and the negative electrode active material layer is not particularly limited in this application, as long as the purpose of this 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.

[0064] The present application does not particularly limit the separator, as long as it can achieve the purpose of the present application. For example, the material of the separator may include, but is not limited to, at least one of polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of separator may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane, or a spun membrane.

[0065] The electrochemical device of this application also includes a packaging bag and an electrolyte. The insulating layer, positive electrode sheet, negative electrode sheet, separator, and electrolyte are contained in the packaging bag. This application does not particularly limit the packaging bag and electrolyte. The packaging bag and electrolyte known in this application may be selected according to actual needs, as long as they can achieve the purpose of this application.

[0066] The present application does not particularly limit the type of electrochemical device, and it can include any device that undergoes an electrochemical reaction. For example, the electrochemical device can include, but is not limited to: lithium metal secondary batteries, lithium ion secondary batteries (lithium ion batteries), sodium ion secondary batteries (sodium ion batteries), lithium polymer secondary batteries, and lithium ion polymer secondary batteries.

[0067] The present application does not impose any particular restrictions on the method for preparing the insulating layer, as long as the purpose of the present application can be achieved. For example, the method for preparing the insulating layer includes but is not limited to the following steps: (1) After mixing inorganic particles and a high molecular weight polymer, a solvent is added and stirred to obtain a glue layer slurry; (2) The glue layer slurry is coated on the surface of a release film by a micro-concave roller. During the drying process, the slurry forms a film and shrinks, and finally a porous glue layer is formed. After the glue layer is composited with the porous substrate, a release agent is provided on the surface of the porous substrate away from the glue layer. After drying, the insulating layer is obtained, rolled up, slit, and set aside. The present application does not impose any particular restrictions on the solid content of the glue layer slurry, as long as the purpose of the present application can be achieved. For example, the solid content of the glue layer slurry is 10wt% to 30wt%. The present application does not impose any particular restrictions on the type of the above-mentioned "solvent", as long as the purpose of the present application can be achieved. The present application does not impose any particular restrictions on the drying and drying temperature in the above-mentioned step (2), as long as the purpose of the present application can be achieved. The present application has no particular limitation on the release film and release agent. Those skilled in the art may select known release films and release agents according to actual conditions, as long as the purpose of the present application can be achieved.

[0068] The present application does not particularly limit the preparation method of the electrochemical device, and any preparation method known in the art may be selected as long as the purpose of the present application can be achieved. For example, the preparation method of the electrochemical device includes but is not limited to the following steps: stacking the positive electrode sheet, the separator, and the negative electrode sheet in order, attaching an insulating layer, and then winding, folding, etc. as needed to obtain a wound electrode assembly, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag, and sealing the bag to obtain the electrochemical device; or stacking the positive electrode sheet, the separator, and the negative electrode sheet in order, attaching an insulating layer, and then fixing the four corners of the entire stacked structure to obtain a stacked electrode assembly, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag, and sealing the bag to obtain the electrochemical device.

[0069] The second aspect of the present application provides an electronic device, which includes the electrochemical device described in any of the above embodiments. Therefore, the electrochemical device has good performance.

[0070] The electronic devices of the present application are not particularly limited and may include, but are not limited to, the following types: laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0071] Example

[0072] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods.

[0073] Test methods and equipment:

[0074] Methods for extracting porous substrates from lithium-ion batteries:

[0075] In a lithium-ion battery, if the insulating layer is located between the negative electrode plate and the separator, after removing the insulating layer from the lithium-ion battery, the insulating layer is placed in a mixed solvent of toluene and ethyl acetate (mass ratio of toluene to ethyl acetate 7:3) and water, respectively, and stirred at 50°C for 20 minutes, then taken out, and dried at 100°C for 2 hours until no solution is obtained, thereby obtaining a porous substrate; if the insulating layer is located between the positive electrode plate and the separator, after removing the insulating layer from the lithium-ion battery, the insulating layer is placed in N-methylpyrrolidone (NMP), stirred at 50°C for 20 minutes, then taken out, and dried at 100°C for 2 hours until no solution is obtained, thereby obtaining a porous substrate.

[0076] Thickness test:

[0077] (1) Insulation layer thickness T 40 The test:

[0078] Take out the positive and negative electrodes from the lithium-ion battery and measure the thickness T of the electrode where the insulation layer is attached. 总 and the thickness T of the non-adhesive part 极片 , insulation layer thickness T 40 =T 总 -T 极片 .

[0079] (2) Thickness of porous substrate T 41 The test:

[0080] Randomly measure the thickness of 6 points of the porous substrate sample and calculate the average value to obtain the thickness T of the porous substrate. 41 .

[0081] (3) Adhesive layer thickness T 42 The test:

[0082] According to the above-mentioned insulation layer thickness T 40 and the thickness of the porous substrate T 41 Calculate the thickness of the adhesive layer T 42 :T 42 =T 40 -T 41 .

[0083] Test of the surface density of porous substrates:

[0084] Use a magnifying glass (CCD, magnification 30 times) to measure the length and width of the porous substrate and calculate the area s in m 2 ; Weigh the porous substrate with known area s using an electronic balance M, unit is g; surface density (g / m 2 )=M / s.

[0085] Test of longitudinal tensile strength and transverse tensile strength of porous substrates:

[0086] (1) Test of longitudinal tensile strength:

[0087] Use a high-speed rail tensile testing machine to clamp the longitudinal ends of a long strip of porous substrate. The transverse cross-sectional area of ​​the porous substrate is A (the transverse length of the porous substrate × the thickness of the porous substrate = the transverse cross-sectional area of ​​the porous substrate). The tensile speed is 120 mm / min and the tensile force F is obtained. A , longitudinal tensile strength Rm v =F A / A.

[0088] (2) Transverse tensile strength test:

[0089] Use a high-speed rail tensile testing machine to clamp the two ends of the long strip of porous substrate. The longitudinal cross-sectional area of ​​the porous substrate is B (the longitudinal length of the porous substrate × the thickness of the porous substrate = the longitudinal cross-sectional area of ​​the porous substrate). The tensile speed is 120 mm / min and the tensile force F is obtained. B , transverse tensile strength Rm c =F B / B.

[0090] Testing of melting temperature of porous substrates:

[0091] About 3 mg of the porous substrate was measured using a differential scanning calorimeter (DSC) (DSC range: 0 mW to 600 mW, temperature fluctuation: ±0.1° C., temperature range: −35° C. to 600° C.), and the peak temperature of the melting peak was selected as the melting temperature.

[0092] Discharge capacity test:

[0093] (1) Place the lithium-ion battery in an environment at 25°C;

[0094] (2) Charge the lithium-ion battery to the charging cut-off voltage (e.g., 4.5V) at a constant current of 0.2C, and charge the lithium-ion battery to 0.02C at a constant voltage of the charging cut-off voltage;

[0095] (3) Let the lithium-ion battery stand for 10 minutes;

[0096] (4) Discharge the lithium-ion battery at a constant current of 0.1C to a discharge cut-off voltage (e.g., 3.0V) and extract the discharge capacity of the lithium-ion battery.

[0097] Short circuit test:

[0098] Under 20±5℃ conditions, charge the lithium-ion battery sample to 100% SOC (i.e. fully charged state), place the sample with one side facing up on the test table, and place a 25mm diameter round rod perpendicular to the extension direction of the lithium-ion battery tab on the sample tab welding area (the position where the welding protective glue is attached). The extrusion speed is 0.1mm / s. When the extrusion force reaches 10±0.78kN, stop the extrusion. Take 20 samples and repeat the above test. The passing criteria are: no fire, no explosion, and no smoke.

[0099] Lithium-ion battery thickness test:

[0100] After the lithium-ion battery is charged to 60% SOC (state of charge), the thickness of the lithium-ion battery is tested using a soft pack battery thickness gauge (PPG) (pressure 700g). The thickness of the lithium-ion battery is obtained by taking the average value of three measurements.

[0101] Example 1-1

[0102] <Preparation of Insulating Layer>

[0103] After mixing inorganic boehmite particles and high molecular weight polymer polymethyl acrylate (glass transition temperature Tg = -30°C), deionized water was added as a solvent and stirred evenly to obtain a glue layer slurry with a solid content of 20 wt %. The inorganic particles had a Dv50 of 100 nm.

[0104] The above adhesive layer slurry is coated on the surface of the release film PET film with a release force of 10g by a micro-concave roller, and dried at 110℃ to form a thickness of T 42 = 3μm adhesive layer, and then the adhesive layer and the porous substrate (thickness T 41 = 9 μm biaxially oriented polypropylene (BOPP film) (manufacturer: Dalian Eco Energy Technology Co., Ltd., model: ECO-9) is laminated, the adhesive layer is transferred to the surface of the porous substrate, and the film is rolled up to obtain an intermediate product with a release film and a porous substrate; the porous substrate side (the opposite side of the adhesive layer) of the intermediate product is coated with a silicone release agent (manufacturer: Dow Corning) using a micro-concave roller, and after drying, the release film is removed while the porous substrate is rolled up to obtain a film with a thickness of T 40 = 12 μm insulating layer (the surface of the insulating layer is shown in FIG4 ).

[0105] Among them, the longitudinal tensile strength Rm of the porous substrate v =1500kgf / cm 2 , transverse tensile strength Rm c =500kgf / cm 2 , surface density = 5g / m 2 , melting temperature = 170° C. Based on the mass of the adhesive layer, the mass percentage of the high molecular weight polymer W1 = 50%, and the mass percentage of the inorganic particles W2 = 50%.

[0106] <Preparation of positive electrode sheet>

[0107] The positive electrode active material, lithium cobalt oxide, the positive electrode conductive agent, conductive carbon black (Super P), and the positive electrode binder, polyvinylidene fluoride (PVDF), were mixed in a mass ratio of 97.2:1.5:1.3. NMP was added as a solvent and stirred in a vacuum mixer until a solid content of 72 wt% and a uniform positive electrode slurry was obtained. The positive electrode slurry was evenly coated on one surface of a 10 μm thick positive electrode current collector aluminum foil and dried at 85°C to obtain a positive electrode sheet coated with a single-sided positive electrode active material layer (90 μm thick). The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a double-sided positive electrode active material layer. The sheet was then cold pressed, cut, and welded to the positive electrode tabs, resulting in a 70 mm x 1400 mm positive electrode sheet ready for use.

[0108] <Preparation of negative electrode sheet>

[0109] Graphite, the negative electrode active material, sodium carboxymethyl cellulose, the negative electrode thickener, and styrene-butadiene rubber, the negative electrode binder, were mixed in a mass ratio of 98:1:1. Deionized water was then added as a solvent and stirred in a vacuum mixer until a uniform negative electrode slurry with a solids content of 42 wt% was obtained. The negative electrode slurry was evenly coated on one surface of an 8 μm thick negative electrode current collector copper foil and dried at 85°C to obtain a negative electrode sheet coated on one side with a negative electrode active material layer (60 μm thick). The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode active material layer. The sheet was then cold pressed, cut, and welded to the nickel tabs, resulting in a negative electrode sheet measuring 74 mm x 1408 mm for later use.

[0110] <Preparation of Separator>

[0111] The base film of the diaphragm is 8μm thick polyethylene (PE). A 2μm thick alumina ceramic layer is coated on both surfaces of the diaphragm base film along its thickness direction. Finally, a 2.5mg / cm thick alumina ceramic layer is coated on both surfaces of the ceramic layer along its thickness direction. 2 The binder PVDF is dried to obtain the diaphragm.

[0112] <Preparation of Electrolyte>

[0113] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are prepared into a basic electrolyte in a mass ratio of 1:1:0.5:1, and lithium hexafluorophosphate (LiPF6) is added and mixed evenly to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0114] <Preparation of lithium-ion batteries>

[0115] The negative electrode sheet, separator, and positive electrode sheet prepared above are stacked and wound in sequence to form a wound electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, injected with electrolyte, and subjected to vacuum packaging, static standing, formation, capacity measurement, degassing, and trimming to obtain a lithium-ion battery.

[0116] Among them, as shown in Figure 7, the surface of the positive electrode tab 13, the first empty foil area 16, the surface of the negative electrode sheet 20 adjacent to the first groove 15, the surface of the negative electrode sheet 20 adjacent to the first empty foil area 16, and the tail area of ​​the positive electrode sheet 10 are all affixed with an insulating layer 40; as shown in Figure 8, the surface of the negative electrode tab 23 and the second empty foil area 26 are affixed with an insulating layer 40, and the surface of the positive electrode sheet 10 adjacent to the second groove 25 and the surface of the positive electrode sheet 10 adjacent to the second empty foil area 26 are affixed with a non-ion-conducting insulating layer 50 (Manufacturer: Todi Chemical (Shanghai) Co., Ltd., Model: T4116BR).

[0117] Example 1-2 to Example 1-15

[0118] Except for adjusting the relevant preparation parameters in Table 1, the rest is the same as Example 1-1.

[0119] Examples 1-16

[0120] The process was the same as Example 1-1 except that the porous substrate in <Preparation of Insulating Layer> was replaced with a uniaxially oriented polypropylene film (manufacturer: Shenzhen Xingyuan Materials Technology Co., Ltd., model: SD216101).

[0121] Example 2-1 to Example 2-11

[0122] Except for adjusting the relevant preparation parameters in Table 2, the rest is the same as Example 1-1.

[0123] Example 3-1 to Example 3-3

[0124] Except for adjusting the relevant preparation parameters in Table 3, the rest is the same as Example 1-1.

[0125] Comparative Example 1

[0126] The insulating layer in <Preparation of Insulating Layer> is replaced by green glue (manufacturer: Dongguan Aozhong New Materials Technology Co., Ltd., with a porosity of 0%), the green glue includes a substrate and an adhesive layer arranged on one surface of the substrate, the material of the substrate is PET, and the material of the adhesive layer is polymethyl acrylate, and the rest is the same as Example 1-1.

[0127] Comparative Example 2 and Comparative Example 3

[0128] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0129] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 3.

[0130] Table 1 Note: The “-” in Table 1 indicates that the corresponding performance parameter cannot be measured. This is because the surface density of the porous substrate is too small, indicating that the porosity of the porous substrate is too high and cannot be prepared into a porous substrate, and therefore cannot be used in lithium batteries.

[0131] As can be seen from Examples 1-1 to 1-16 and Comparative Examples 1 to 3, the lithium-ion batteries of the present examples, by selecting a porous substrate material comprising polypropylene and controlling the surface density of the porous substrate within the range of this application, have a high capacity and a small thickness, indicating that the lithium-ion batteries have high capacity and energy density. However, in the lithium-ion batteries of the comparative examples, at least one of the type of porous substrate or the surface density of the porous substrate is outside the range of this application, resulting in the lithium-ion batteries not functioning properly or having a low capacity.

[0132] The type of porous substrate generally affects the safety and capacity of lithium-ion batteries. As can be seen from Examples 1-1, 1-16, and Comparative Example 1, lithium-ion batteries using porous substrates within the scope of this application exhibit higher capacity and lower thickness. Compared to Example 1-16, the lithium-ion battery of Example 1-1 uses BOPP as the porous substrate, which exhibits higher capacity and energy density without compromising safety.

[0133] Surface density and longitudinal tensile strength Rm of porous substrate v , transverse tensile strength Rm c , melting temperature usually affects the safety performance and capacity of lithium-ion batteries. From Examples 1-1 to 1-9, Comparative Examples 2 and 3, it can be seen that the surface density and longitudinal tensile strength Rm of the porous substrate are selected. v , transverse tensile strength Rm c The lithium-ion battery with a melting temperature within the range of this application can have a high capacity and a small thickness on the basis of good safety performance. In addition, the surface density is controlled at 3g / m 2 Up to 11g / m 2 It can keep the appropriate tensile strength of the substrate, reduce the risk of the insulating layer being deformed into a dumbbell shape when the insulating layer pasting mechanism pastes the insulating layer, reduce the width of the insulating layer in the lateral direction of the substrate, and cannot cover the originally designed covering area, resulting in the exposure of the originally covered area of ​​the electrode, and part of the welding area cannot be protected, thereby causing the positive and negative electrodes to contact and cause the electrochemical device to short-circuit. This further improves the safety performance caused by the short circuit in the machine ear welding area.

[0134] The thickness of the insulating layer generally affects the safety performance and capacity of lithium-ion batteries. As can be seen from Examples 1-1, 1-10, and 1-15, lithium-ion batteries with insulating layer thicknesses within the range of this application can achieve both good safety performance and high capacity.

[0135] The thickness of the porous substrate generally affects the safety and capacity of lithium-ion batteries. As can be seen from Examples 1-1, 1-9, and 1-10, lithium-ion batteries using a porous substrate thickness within the range of this application can achieve both good safety and high capacity.

[0136] The thickness of the glue layer usually affects the safety performance and capacity of the lithium-ion battery.

[0137] It can be seen from Examples 1-13 that the lithium-ion battery using a porous substrate having a thickness within the range of the present application can have a high capacity on the basis of good safety performance.

[0138] Table 2

[0139] The types of polymers and inorganic particles generally affect the safety and capacity of lithium-ion batteries. As can be seen from Examples 1-1, 2-1, 2-7, lithium-ion batteries using polymers and inorganic particles within the scope of this application can achieve high capacity while maintaining good safety.

[0140] The mass percentages of polymer and inorganic particles in the adhesive layer generally affect the safety and capacity of lithium-ion batteries. As can be seen from Examples 1-1, 2-8, and 2-11, lithium-ion batteries with polymer and inorganic particle mass percentages within the ranges of this application can achieve both good safety and high capacity.

[0141] Table 3

[0142] The Dv50 of inorganic particles generally affects the safety and capacity of lithium-ion batteries. As can be seen from Examples 1-1, 3-1, and 3-3, lithium-ion batteries using inorganic particles with a Dv50 within the range of this application can achieve both good safety and high capacity.

[0143] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0144] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0145] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An electrochemical device comprising an insulating layer, a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet includes a positive electrode tab, the insulating layer is interposed between the separator and the positive electrode tab, or the insulating layer is interposed between the separator and the positive electrode sheet tail region; the insulating layer comprises a porous substrate; wherein: The porous substrate comprises polypropylene, and the surface density of the porous substrate is 2 g / m 2 Up to 11g / m 2 .

2. The electrochemical device according to claim 1, wherein The surface density of the porous substrate is 3 g / m 2 Up to 11g / m 2 .

3. The electrochemical device according to claim 1, wherein A glue layer is provided on one surface of the porous substrate, and the glue layer includes a high molecular polymer and inorganic particles; The glass transition temperature of the high molecular polymer is -30°C to -10°C, and the high molecular polymer comprises polyacrylate; The inorganic particles include at least one of boehmite, aluminum oxide, titanium dioxide, magnesium oxide, zirconium oxide or zinc oxide; Based on the mass of the adhesive layer, the mass percentage of the high molecular weight polymer is 30% to 95%, and the mass percentage of the inorganic particles is 5% to 70%.

4. The electrochemical device according to claim 3, wherein the inorganic particles are boehmite, and based on the mass of the adhesive layer, the mass percentage of the high molecular weight polymer is 30% to 60%, and the mass percentage of the inorganic particles is 40% to 70%.

5. The electrochemical device according to claim 3, wherein The adhesive layer is provided with holes, and part of the porous substrate is exposed from the holes of the adhesive layer.

6. The electrochemical device according to any one of claims 1 to 5, wherein The longitudinal tensile strength of the porous substrate is 1000 kgf / cm 2 Up to 2000kgf / cm 2 The transverse tensile strength of the porous substrate is 300 kgf / cm 2 Up to 600kgf / cm 2 .

7. The electrochemical device according to any one of claims 1 to 5, wherein The thickness of the insulating layer is 8 μm to 30 μm.

8. The electrochemical device according to any one of claims 1 to 5, wherein The thickness of the insulating layer is 8 μm to 17 μm.

9. The electrochemical device according to any one of claims 1 to 5, wherein The thickness of the porous substrate is 8 μm to 20 μm.

10. The electrochemical device according to any one of claims 3 to 5, wherein The thickness of the adhesive layer is 1 μm to 8 μm.

11. The electrochemical device according to claim 3 or 4, wherein The Dv50 of the inorganic particles is 80 nm to 1000 nm.

12. The electrochemical device according to any one of claims 1 to 5, wherein The apertured substrate has a melting temperature of 165°C to 175°C.

13. The electrochemical device according to any one of claims 1 to 5, wherein The positive electrode sheet includes a positive electrode active material layer and a positive electrode current collector, the positive electrode current collector includes a first surface and a second surface opposite to each other, the positive electrode active material layer is provided at least on the first surface of the positive electrode current collector, a first groove is provided in the positive electrode active material layer to expose the positive electrode current collector, the positive electrode tab is provided in the first groove and connected to the positive electrode current collector, and the second surface includes a first empty foil area opposite to the first groove; The insulating layer is adhered to at least one of the surface of the positive electrode tab, the first empty foil area, the surface of the negative electrode sheet adjacent to the first groove, the surface of the negative electrode sheet adjacent to the first empty foil area, or the positive electrode sheet tail area.

14. The electrochemical device according to any one of claims 1 to 6, wherein The negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer and a negative electrode tab. The negative electrode current collector includes a third surface and a fourth surface opposite to each other. The negative electrode active material layer is provided at least on the third surface of the negative electrode current collector. A second groove is provided in the negative electrode active material layer to expose the negative electrode current collector. The negative electrode tab is provided in the second groove and connected to the negative electrode current collector. The fourth surface includes a second empty foil area opposite to the second groove. The insulating layer is adhered to at least one location on the surface of the negative electrode tab or the second empty foil area.

15. An electronic device comprising the electrochemical device according to any one of claims 1 to 14.

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