Separator, electrochemical device and electronic device

Abstract

The present application provides a separator, an electrochemical device and an electronic device. The separator comprises a base material, and an inorganic coating and a bonding layer that are arranged on one surface of the base material; the inorganic coating is arranged between the base material and the bonding layer; the binding layer is arranged on the other surface of the base material; the bonding layer comprises polymer particles, and the average particle size of the polymer particles is Dv50 μm; and the surface of the inorganic coating is provided with a plurality of pits, the depth of each pit is C μm, and C and Dv50 meet the following conditions: 0.25≤C / Dv50≤4 and 0.5≤C≤2. When the separator is applied to the electrochemical device, the internal resistance of the electrochemical device can be reduced, improving the temperature conversion coefficient of the electrochemical device.

Description

A diaphragm, electrochemical device and electronic device

[0001] The present application claims priority to the Chinese patent application No. 202410544857.3, filed on April 30, 2024, and entitled "A diaphragm, electrochemical device and electronic device", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of electrochemistry, in particular to a diaphragm, electrochemical device and electronic device. BACKGROUND

[0003] With the popularity of electronic products such as notebook computers, mobile phones, handheld game consoles and tablet computers, people's requirements for electrochemical devices (for example, lithium ion batteries) are also becoming more and more strict. Lithium ion batteries have the characteristics of high energy density, high working voltage, low self-discharge rate, small size and light weight, and are widely used in various fields such as electric energy storage, portable electronic devices and electric vehicles. However, the existing lithium ion batteries are prone to have the technical problem of too low temperature conversion coefficient, therefore, how to improve the temperature conversion coefficient of lithium ion batteries has become a technical problem to be solved by the technical personnel in the field. SUMMARY

[0004] The purpose of the present application is to provide a diaphragm, electrochemical device and electronic device to improve the temperature conversion coefficient of the electrochemical device.

[0005] It should be noted that the present application is explained by taking lithium ion batteries as an example of electrochemical devices in the summary of the present application, but the electrochemical device of the present application is not limited to lithium ion batteries. The specific technical solutions are as follows:

[0006] The first aspect of the present application provides a separator, the separator comprising a substrate, and an inorganic coating layer and a bonding layer provided on one surface of the substrate, the inorganic coating layer being provided between the substrate and the bonding layer, the other surface of the substrate being provided with the bonding layer, the bonding layer comprising polymer particles, the average particle size of the polymer particles being Dv50 μm; the surface of the inorganic coating layer having a plurality of pits, the depth of the pits being C μm, C and Dv50 satisfying: 0.25≤C / Dv50≤4, 0.5≤C≤2. By providing the inorganic coating layer and the bonding layer on one surface of the substrate of the separator, and providing a plurality of pits on the surface of the inorganic coating layer, and regulating the depth C of the pits and the ratio C / Dv50 between the depth C and the average particle size of the polymer particles in the bonding layer within the range of the present application, when the bonding layer is provided on the inorganic coating layer, the bonding layer can make the inorganic coating layer and the bonding layer have good bonding uniformity with a lower coating amount, and the polymer particles in the bonding layer can exert their own good bonding force, so that the separator has good bonding force. When the separator is applied to an electrochemical device, the internal resistance of the electrochemical device can be reduced, and thus the temperature conversion coefficient of the electrochemical device is improved.

[0007] In some embodiments of the present application, 0.4≤Dv50≤1. By regulating the average particle size Dv50 of the polymer particles within the above range, the internal resistance of the electrochemical device can be reduced, and the electrochemical device has a higher temperature conversion coefficient.

[0008] In some embodiments of the present application, the width D of the pits is 0.5 μm to 2 μm. By regulating the width of the pits within the above range, the internal resistance of the electrochemical device is reduced, and thus the temperature conversion coefficient of the electrochemical device is improved.

[0009] In some embodiments of the present application, the thickness E of the inorganic coating layer is 0.5 μm to 3 μm. By regulating the thickness E of the inorganic coating layer within the above range, the electrochemical device has a higher temperature conversion coefficient and a higher energy density.

[0010] In some embodiments of the present application, the separator satisfies at least one of the following (1) to (5): (1) 0.3≤C / Dv50≤3.5; (2) 0.5≤C≤1.0; (3) 0.5≤Dv50≤1.0; (4) the width D of the pits is 0.5 μm to 1.5 μm; (5) the thickness E of the inorganic coating layer is 0.5 μm to 2 μm.

[0011] In some embodiments of the present application, the thickness E of the inorganic coating layer is 0.5 μm to 1.5 μm. By regulating the thickness E of the inorganic coating layer within the above range, the electrochemical device has a higher temperature conversion coefficient and a higher energy density.

[0012] In some embodiments of the present application, the inorganic coating layer comprises filler particles and an inorganic coating binder, the filler particles comprise at least one of boehmite, alumina, zirconia, titania, magnesia, mullite, silicon carbide or silicon nitride, the inorganic coating binder comprises at least one of polyvinyl alcohol, polyacrylic acid, hydroxymethyl cellulose, styrene butadiene rubber or polymethyl methacrylate; the mass percentage of the filler particles is 95% to 99% and the mass percentage of the inorganic coating binder is 1% to 5% based on the mass of the inorganic coating layer. The use of the above-mentioned filler particles and inorganic coating binder and the adjustment of the mass percentage of the filler particles and the inorganic coating binder in the inorganic coating layer within the above-mentioned range is conducive to the electrochemical device having a higher temperature conversion coefficient.

[0013] In some embodiments of the present application, the adhesive layer further comprises an auxiliary binder, the polymer particles comprise at least one of polyvinylidene fluoride or polymethyl methacrylate, the auxiliary binder comprises at least one of polyvinyl alcohol, polyacrylic acid, hydroxymethyl cellulose or styrene butadiene rubber; the mass percentage of the polymer particles is 97% to 99.5% and the mass percentage of the auxiliary binder is 0.5% to 3% based on the mass of the adhesive layer. The use of the above-mentioned polymer particles and auxiliary binder and the adjustment of the mass percentage of the polymer particles and the auxiliary binder in the adhesive layer within the above-mentioned range is conducive to the electrochemical device having a higher temperature conversion coefficient.

[0014] In some embodiments of the present application, the other surface of the substrate is further provided with an inorganic coating layer, and the inorganic coating layer is arranged between the substrate and the adhesive layer.

[0015] In some embodiments of the present application, the separator comprises a first surface provided with an inorganic coating layer and an adhesive layer, the adhesion of the first surface to the positive electrode sheet is 7 N / m to 40 N / m, and the adhesion of the first surface to the negative electrode sheet is 6 N / m to 30 N / m.

[0016] The second aspect of the present application provides an electrochemical device, which comprises the separator according to any one of the preceding embodiments. Therefore, the electrochemical device has a higher temperature conversion coefficient.

[0017] The third aspect of the present application provides an electronic device, wherein the electronic device comprises the electrochemical device according to any one of the preceding embodiments. Therefore, the electronic device has good use performance.

[0018] The beneficial effects of the present application are as follows:

[0019] The application provides a separator, an electrochemical device and an electronic device, wherein by arranging a plurality of pits on the surface of the inorganic coating layer of the separator, and regulating the depth C of the pits and the ratio C / Dv50 between the depth C and the average particle size of the polymer particles in the adhesive layer within the range of the application, when the adhesive layer is arranged on the inorganic coating layer, the adhesive layer can make the inorganic coating layer and the adhesive layer have good bonding uniformity with a lower coating amount, and the polymer particles in the adhesive layer can exert their own good bonding force, so that the separator has good bonding force. When the separator is applied to the electrochemical device, the internal resistance of the electrochemical device can be reduced, and thus the temperature conversion coefficient of the electrochemical device is improved.

[0020] Of course, implementing any product or method of the application does not necessarily require all the advantages described above to be achieved at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other embodiments can also be obtained by those skilled in the art based on these drawings.

[0022] Fig. 1 is a schematic diagram of the cross-sectional structure of the separator along the thickness direction and the width direction of the separator according to some embodiments of the application;

[0023] Fig. 2 is a schematic diagram of the cross-sectional structure of the separator along the thickness direction and the width direction of the separator according to some other embodiments of the application;

[0024] Fig. 3 is a scanning electron microscope photograph of the cross section of the inorganic coating layer according to some embodiments of the application.

[0025] Reference signs: 10-separator; 11-substrate; 12-inorganic coating layer; 121-pit; 13-adhesive layer; 101-first surface; 102-second surface; 113-third surface; 114-fourth surface. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. All other embodiments obtained by those skilled in the art based on the application belong to the scope of protection of the application.

[0027] It should be noted that in the specific embodiments of the application, the lithium ion battery is taken as an example of the electrochemical device to explain the application, but the electrochemical device of the application is not limited to the lithium ion battery.

[0028] The first aspect of the present application provides a separator, comprising a substrate, and an inorganic coating layer and an adhesive layer disposed on one surface of the substrate, the inorganic coating layer being disposed between the substrate and the adhesive layer, and the other surface of the substrate being provided with the adhesive layer. The adhesive layer comprises polymer particles, the average particle size of the polymer particles being Dv50 μm; the surface of the inorganic coating layer has a plurality of pits, the depth of the pits being C μm, C and Dv50 satisfying: 0.25≤C / Dv50≤4, 0.5≤C≤2.

[0029] For the convenience of understanding, in the present application, the width direction of the separator itself is defined as Y, and the thickness direction of the separator itself is defined as Z. It should be understood that the above definition of the direction is for the purpose of facilitating the description of the present application, and the direction defined in the present application can be understood according to the relative position of the actual product elements in the drawings. Moreover, the width direction and the thickness direction of the substrate, the inorganic coating layer and the adhesive layer are the same as those of the separator. As shown in FIG. 1, the separator 10 comprises a substrate 11, an inorganic coating layer 12 and an adhesive layer 13, the substrate 11 comprises a third surface 113 and a fourth surface 114 oppositely arranged along the thickness direction Z, the third surface 113 of the substrate 11 is sequentially provided with the inorganic coating layer 12 and the adhesive layer 13, the surface of the inorganic coating layer 12 has a plurality of pits 121, the depth of the pits 121 is shown as C, and the width of the pits 121 is shown as D. The surface of the separator 10 provided with the inorganic coating layer 12 and the adhesive layer 13 is the first surface 101. The fourth surface 114 of the substrate 11 is provided with the adhesive layer 13, the adhesive layer 13 is adjacent to and in contact with the third surface 114, and the surface of the separator 10 provided with the adhesive layer 13 and not provided with the inorganic coating layer 12 is the second surface 102. The above-mentioned "a plurality of pits" refers to two or more pits, and the specific number is not particularly limited as long as the purpose of the present application can be achieved. It can be understood that each pit is the same or different, because each filler particle in the inorganic coating layer is not completely the same. It should be noted that the pits in the drawings of the present application are only for illustration, and are not limited thereto. In the present application, the "depth of the pits" refers to the average value of the distance from the surface of the inorganic coating layer to the lowest point of each pit along the thickness direction of the separator in the cross section obtained by the inorganic coating layer along the thickness direction and the width direction, in an area with an area of 100 μm 2 .

[0030] For example, the ratio C / Dv50 of the depth C of the pits to the average particle size Dv50 of the polymer particles is 0.25, 0.3, 0.45, 0.60, 0.84, 0.9, 1.0, 1.6, 2.0, 2.1, 2.3, 2.6, 2.9, 3.1, 3.4, 3.7, 4, or any value between any two of the above ranges. When C / Dv50 is less than 0.25, the depth of the pits is too small relative to the average particle size of the polymer particles, the surface of the inorganic coating is too smooth, the adhesion between the adhesive layer and the inorganic coating is insufficient, and the adhesive layer is prone to delamination, which affects the normal use performance of the separator. When C / Dv50 is greater than 4, the depth of the pits is too large relative to the average particle size of the polymer particles, the polymer particles are prone to embed in the pits, and the adhesive layer is difficult to play its own adhesive role, which will result in too large a coating weight of the adhesive layer, thereby increasing the internal resistance of the electrochemical device.

[0031] For example, the depth C of the pits is 0.5, 0.7, 0.9, 1.2, 1.4, 1.6, 1.8, 2, or any value between any two of the above ranges. When C is less than 0.5, the depth C of the pits is too small, the surface of the inorganic coating is too smooth, the adhesion between the inorganic coating and the adhesive layer is insufficient, and the adhesive layer is prone to delamination. When C is greater than 2, the depth C of the pits is too large, and when the adhesive layer is provided on the surface of the inorganic coating, the coating weight of the adhesive layer is increased, thereby increasing the internal resistance of the electrochemical device and reducing the temperature conversion coefficient of the electrochemical device.

[0032] Overall, by providing the inorganic coating and the adhesive layer on one surface of the separator substrate, and providing a plurality of pits on the surface of the inorganic coating, and adjusting the depth C of the pits and the ratio C / Dv50 between the depth C and the average particle size of the polymer particles in the adhesive layer within the range of the present application, when the adhesive layer is provided on the inorganic coating, the adhesive layer can have good adhesion uniformity between the inorganic coating and the adhesive layer with a lower coating weight, the polymer particles in the adhesive layer can play their own good adhesion, and the separator has good adhesion. When the separator is applied to an electrochemical device, it is beneficial to improve the adhesion between the separator and the electrochemical device, thereby improving the temperature conversion coefficient of the electrochemical device.

[0033] In some embodiments of the present application, 0.3≤C / Dv50≤3.5. For example, C / Dv50 is 0.3, 0.45, 0.60, 0.84, 0.9, 1.0, 1.6, 2.0, 2.1, 2.3, 2.6, 2.9, 3.1, 3.5, or any value between any two of the above ranges. By adjusting C / Dv50 within the above range, the adhesive layer can have good adhesion uniformity between the adhesive layer and the inorganic coating with a lower coating weight, and the adhesive layer also has good adhesion. When the separator is applied to an electrochemical device, the electrochemical device has a lower internal resistance, thereby improving the temperature conversion coefficient of the electrochemical device.

[0034] In some embodiments of the present application, 0.5≤C≤1.0. For example, the depth C of the recess is 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or any value within a range between any two of the above values. Controlling the depth C of the recess within the above range can allow the adhesive layer to have good adhesion uniformity between the adhesive layer and the inorganic coating layer with a lower coating amount, and the adhesive layer also has good adhesion, and the application of the separator to the electrochemical device can reduce the internal resistance of the electrochemical device, thereby improving the temperature conversion coefficient of the electrochemical device.

[0035] In some embodiments of the present application, 0.4≤Dv50≤1. In some embodiments of the present application, the average particle size Dv50 of the polymer particles is 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or any value within a range between any two of the above values. Controlling the average particle size Dv50 of the polymer particles within the above range can allow the average particle size of the polymer particles to have a higher matching degree with the size of the recess, and the number of the polymer particles that fall into the recess can be appropriate, so that the adhesive layer can have good adhesion between the adhesive layer and the inorganic coating layer, and the coating amount of the adhesive layer can be lower, and the application of the separator to the electrochemical device can reduce the internal resistance of the electrochemical device, thereby improving the temperature conversion coefficient of the electrochemical device.

[0036] In some embodiments of the present application, 0.5≤Dv50≤1.0. For example, the average particle size Dv50 of the polymer particles is 0.5, 0.6, 0.7, 0.8, 1.0, or any value within a range between any two of the above values. Controlling the average particle size Dv50 of the polymer particles within the above range can further reduce the internal resistance of the electrochemical device, thereby further improving the temperature conversion coefficient of the electrochemical device.

[0037] In some embodiments of the present application, as shown in FIG. 1, the width D of the recess 121 is 0.5 μm to 2 μm. For example, the width D of the recess is 0.5 μm, 0.7 μm, 0.9 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, or any value within a range between any two of the above values. Controlling the width of the recess within the above range can allow some of the polymer particles to fall into the recess, so that the adhesive layer can have good adhesion between the adhesive layer and the inorganic coating layer, the adhesion effect of the polymer particles in the adhesive layer can be fully exerted, and the coating amount of the adhesive layer can be reduced. The application of the separator to the electrochemical device can reduce the internal resistance of the electrochemical device, thereby improving the temperature conversion coefficient of the electrochemical device. In the present application, the “width of the recess” refers to the average value of the maximum distance of each recess measured in the width direction of the separator within an area of 100 μm2 obtained in the cross section of the inorganic coating layer in the thickness direction and the width direction. 2 ​

[0038] In some embodiments of the present application, the width D of the dimples is 0.5 μm to 1.5 μm. For example, the width D of the dimples is 0.5 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.5 μm, or any value within a range between any two of the above values. Controlling the width of the dimples within the above range can further reduce the internal resistance of the electrochemical device, and further improve the temperature conversion coefficient of the electrochemical device.

[0039] The present application does not have a particular limitation on the way of controlling the width and depth of the dimples, as long as the purpose of the present application can be achieved. For example, it can be achieved by controlling at least one of the average particle size of the filler particles in the inorganic coating or the shape of the filler particles.

[0040] The present application does not have a particular limitation on the way of controlling the average particle size Dv50 of the polymer particles, as long as the purpose of the present application can be achieved. For example, commercially available polymer particles having an average particle size within the range of the present application can be selected, and the average particle size of the polymer particles can be determined by combining the "Test for the average particle size of polymer particles" in the present application to select polymer particles having the desired average particle size. Polymer particles having the desired average particle size can also be obtained by grinding, sieving, or the like.

[0041] In some embodiments of the present application, the thickness E of the inorganic coating is 0.5 μm to 3 μm. For example, the thickness E of the inorganic coating is 0.5 μm, 0.8 μm, 1.2 μm, 1.7 μm, 2.0 μm, 2.4 μm, 2.7 μm, 3 μm, or any value within a range between any two of the above values. Controlling the thickness E of the inorganic coating within the above range is advantageous in making the separator have a smaller thickness, thereby reducing the risk of energy density loss due to the increase in the volume of the electrochemical device caused by the increase in the thickness of the separator, and thus the electrochemical device has a higher energy density on the basis of a higher temperature conversion coefficient.

[0042] In some embodiments of the present application, the thickness E of the inorganic coating is 0.5 μm to 2 μm. For example, the thickness E of the inorganic coating is 0.5 μm, 0.8 μm, 1.2 μm, 1.4 μm, 1.7 μm, 2 μm, or any value within a range between any two of the above values. Controlling the thickness E of the inorganic coating within the above range is advantageous in further improving the electrochemical device to have a higher temperature conversion coefficient and energy density.

[0043] In some embodiments of the present application, the thickness E of the inorganic coating layer is 0.5 μm to 1.5 μm. For example, the thickness E of the inorganic coating layer is 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm, or any value within a range between any two of the above values. Controlling the thickness E of the inorganic coating layer within the above range is advantageous for further improving the electrochemical device to have a higher temperature conversion coefficient and energy density.

[0044] In some embodiments of the present application, the inorganic coating layer includes filler particles including at least one of boehmite, alumina, zirconia, titania, magnesia, mullite, silicon carbide, or silicon nitride, and an inorganic coating binder including at least one of polyvinyl alcohol (PVA), polyacrylic acid (PAA), hydroxymethyl cellulose, styrene butadiene rubber (SBR), or polymethyl methacrylate; the mass percentage of the filler particles is 95% to 99%, and the mass percentage of the inorganic coating binder is 1% to 5%, based on the mass of the inorganic coating layer. For example, the mass percentage of the filler particles is 95%, 96%, 97%, 98%, 99%, or any value within a range between any two of the above values. For example, the mass percentage of the inorganic coating binder is 1%, 2%, 3%, 4%, 5%, or any value within a range between any two of the above values. Selecting the above types of filler particles and inorganic coating binder and controlling the mass percentages of the filler particles and the inorganic coating binder in the inorganic coating layer within the above ranges allows the inorganic coating layer to have good performance, which is advantageous for the separator to have good wettability and low impedance, and for the electrochemical device to have a higher temperature conversion coefficient.

[0045] The average particle diameter of the filler particles is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the average particle diameter of the filler particles is 200 nm to 2 μm, further 500 nm to 1.5 μm.

[0046] The shape of the filler particles is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the shape of the boehmite particles in the filler particles is a hexahedral shape, and the shapes of the other particles other than boehmite are irregular shapes.

[0047] In the present application, the "average particle diameter" means a particle diameter at which 50% of the particles by volume are accumulated from the small particle diameter side in a particle size distribution on a volume basis. The "particle" described above can be the filler particles of the present application or the polymer particles of the present application.

[0048] In some embodiments of the present application, the adhesive layer further comprises an auxiliary binder, the polymer particles comprise at least one of polyvinylidene fluoride or polymethyl methacrylate (PMMA), the auxiliary binder comprises at least one of polyvinyl alcohol, polyacrylic acid, hydroxymethyl cellulose or styrene butadiene rubber; the mass percentage of the polymer particles is 97% to 99.5% and the mass percentage of the auxiliary binder is 0.5% to 3% based on the mass of the adhesive layer. For example, the mass percentage of the polymer particles is 97%, 97.5%, 98%, 98.5%, 99%, 99.5% or any value within the range between any two of the above values. For example, the mass percentage of the auxiliary binder is 0.5%, 1%, 1.5%, 2%, 2.5%, 3% or any value within the range between any two of the above values. By selecting the above types of polymer particles and auxiliary binders and adjusting the mass percentages of the polymer particles and the auxiliary binders in the adhesive layer within the above ranges, an adhesive layer with good adhesion is prepared, which is conducive to the application of the separator in an electrochemical device with a higher temperature conversion coefficient.

[0049] In some embodiments of the present application, the other surface of the substrate is further provided with an inorganic coating layer, and the inorganic coating layer is arranged between the substrate and the adhesive layer. As shown in FIG. 2, the separator 10 comprises a substrate 11, an inorganic coating layer 12 and an adhesive layer 13, the substrate 11 comprises a third surface 113 and a fourth surface 114 arranged oppositely along the thickness direction Z. The inorganic coating layer 12 and the adhesive layer 13 are sequentially arranged on the third surface 113 of the substrate 11, and the inorganic coating layer 12 and the adhesive layer 13 are sequentially arranged on the fourth surface 114 of the substrate 11, and the inorganic coating layer 12 is arranged between the substrate 11 and the adhesive layer 13. The two side surfaces of the separator 10 arranged oppositely along the thickness direction Z are both the first surface 101. Further arranging the inorganic coating layer and the adhesive layer on the other surface of the substrate can further improve the hardness and adhesion of the separator, both surfaces of the separator have good adhesion, which can have good adhesion uniformity with the positive electrode plate and the negative electrode plate, the adhesive layer has a low coating amount, and at the same time improves the retention amount of the electrolyte of the separator. The separator is applied to an electrochemical device, and the electrochemical device has a low internal resistance, thereby having a high temperature conversion coefficient.

[0050] In some embodiments of the present application, as shown in FIG. 1 and FIG. 2, the separator 10 comprises a first surface 101 provided with an inorganic coating layer 12 and a bonding layer 13, the adhesion of the first surface 101 to the positive electrode tab is 7 N / m to 40 N / m, and the adhesion of the first surface 101 to the negative electrode tab is 6 N / m to 30 N / m. It should be noted that the "adhesion of the first surface to the positive electrode tab" can also be understood as the adhesion between the first surface of the side of the separator provided with the inorganic coating layer and the bonding layer and the positive electrode tab, and the "adhesion of the first surface to the negative electrode tab" can also be understood as the adhesion between the first surface of the side of the separator provided with the inorganic coating layer and the bonding layer and the negative electrode tab. For example, the adhesion of the first surface to the positive electrode tab is 7 N / m, 10 N / m, 13 N / m, 17 N / m, 20 N / m, 25 N / m, 30 N / m, 33 N / m, 40 N / m or any value within any two of the above numerical ranges. For example, the adhesion of the first surface to the negative electrode tab is 6 N / m, 10 N / m, 13 N / m, 17 N / m, 20 N / m, 25 N / m, 28 N / m, 30 N / m or any value within any two of the above numerical ranges. When the separator is applied to an electrochemical device, the first surface of the separator has good adhesion between the positive electrode tab and the negative electrode tab, which is beneficial to make the electrochemical device have a higher temperature conversion coefficient on the basis of having good safety performance. It should be noted that the "first surface of the separator" in the present application can be understood as the surface of the side of the separator provided with both the inorganic coating layer and the bonding layer. The "second surface of the separator" can be understood as the surface of the side of the separator provided with the bonding layer but not provided with the inorganic coating layer. Specifically, in some embodiments, as shown in FIG. 1, the second surface 102 of the separator 10 refers to the surface of the side of the separator 10 provided with only the bonding layer 13 but not provided with the inorganic coating layer 12; as shown in FIG. 2, the surfaces of both sides of the separator 10 are provided with both the inorganic coating layer 12 and the bonding layer 13, which are the first surface 101, and therefore do not have the second surface 102.

[0051] The base material in the separator 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 purpose of the present application can be achieved. For example, the material of the base material can include but is not limited to at least one of polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET). The structure of the base material can be a single-layer structure or a multi-layer structure. For example, the multi-layer structure can be two layers, three layers or four layers. The thickness of the base material can be 3 μm to 20 μm. The porosity of the base material can be 20% to 50%. The pore size of the base material can be 30 nm to 50 nm.

[0052] The preparation method of the separator is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, in some embodiments, the preparation method of the separator includes but is not limited to the following steps: (1) uniformly mixing inorganic particles and inorganic coating binders, adding a solvent to prepare an inorganic coating slurry with a solid content of 25wt% to 55wt%; uniformly mixing polymer particles and auxiliary binders, adding a solvent to prepare an adhesive layer slurry with a solid content of 2wt% to 40wt%; (2) coating the inorganic coating slurry on one surface of the substrate, and after drying, forming an inorganic coating separator; (3) spraying the adhesive layer slurry on the surface of the inorganic coating, and after drying, directly spraying the adhesive layer slurry on the other surface of the substrate, and after drying, obtaining the separator. In other embodiments, the preparation method of the separator includes but is not limited to the following steps: (1) uniformly mixing inorganic particles and inorganic coating binders, adding a solvent to prepare an inorganic coating slurry with a solid content of 25wt% to 55wt%; uniformly mixing polymer particles and auxiliary binders, adding a solvent to prepare an adhesive layer slurry with a solid content of 2wt% to 40wt%; (2) coating the inorganic coating slurry on both surfaces of the substrate, and after drying, forming an inorganic coating; (3) spraying the adhesive layer slurry on the surfaces of the two inorganic coatings away from the substrate, and after drying, obtaining the separator. 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.

[0053] The second aspect of the present application provides an electrochemical device, which includes the separator of any one of the preceding embodiments. Therefore, the electrochemical device has a higher temperature conversion coefficient.

[0054] In some embodiments of the present application, the electrochemical device includes a separator, a positive electrode sheet and a negative electrode sheet, and the separator is located between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet. In some embodiments, the structure of the separator is shown in FIG. 1, and the separator is applied to the electrochemical device, the first surface of the separator is adjacent to the positive electrode sheet, and the second surface of the separator is adjacent to the negative electrode sheet.

[0055] The positive electrode sheet 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 sheet includes a positive electrode current collector and a positive electrode active material layer. 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 or an aluminum alloy foil, etc. The positive electrode active material layer of the present application 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 cobaltate, lithium manganate, lithium manganese iron phosphate, or lithium titanate, etc. In the present application, the positive electrode active material can also include non-metallic elements, for example, the non-metallic elements include at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur, which can further improve the stability of the positive electrode active material. In the present application, the thickness of the positive electrode current collector and the positive electrode active material layer is not particularly limited, 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, preferably 6 μm to 18 μm. The thickness of the single-sided positive electrode active material layer is 30 μm to 120 μm. In the present application, the positive electrode active material layer can be arranged on one surface in the thickness direction of the positive electrode current collector, or can be arranged on both surfaces in the thickness direction of the positive electrode current collector. Optionally, the positive electrode active material layer can also include a positive electrode conductive agent and 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 those skilled in the art can select according to actual needs, as long as the object of the present application can be achieved. For example, 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 (97.5 to 97.9):(0.8 to 1.7):(1.0 to 2.0).

[0056] The negative electrode sheet 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 sheet includes a negative electrode current collector and a negative electrode active material layer. 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 stainless steel foil, a titanium foil, a nickel foam, or a copper foam, etc. The negative electrode active material layer of the present application 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 natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x < 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate with spinel structure Li4Ti5O 12Li-Al alloy or metallic lithium. In the present application, the thickness of the negative current collector and the negative active material layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the negative current collector is 6 to 10 μm, and the thickness of the negative active material layer is 30 to 130 μm. Optionally, the negative active material layer can further include at least one of a negative conductive agent, a thickening agent, and a negative binder. The present application does not particularly limit the kind of the negative conductive agent, the thickening agent, and the negative binder in the negative active material layer as long as the object of the present application can be achieved. The present application does not particularly limit the mass ratio of the negative active material, the negative conductive agent, the thickening agent, and the negative binder in the negative active material layer as long as the object of the present application can be achieved. For example, the mass ratio of the negative active material, the negative conductive agent, the thickening agent, and the negative binder in the negative active material layer is (97 to 98):(0.5 to 1.5):(0 to 1.5):(1.0 to 1.9).

[0057] The electrochemical device of the present application further includes an electrolyte and a packaging bag, and the electrolyte, the separator, the positive electrode sheet, and the negative electrode sheet are contained in the packaging bag. The present application does not particularly limit the electrolyte and the packaging bag, and any electrolyte and packaging bag known in the art can be used as long as the object of the present application can be achieved.

[0058] The present application does not particularly limit the kind of the electrochemical device, and it can include any device in which an electrochemical reaction occurs. For example, the electrochemical device can include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a sodium ion secondary battery (sodium ion battery), a lithium polymer secondary battery, a lithium ion polymer secondary battery.

[0059] The present application does not particularly limit the method of manufacturing the electrochemical device, and any method known in the art can be used as long as the object of the present application can be achieved. For example, the method of manufacturing the electrochemical device 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 winding, folding, or the like as necessary to obtain an electrode assembly having a wound structure, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag and sealing it to obtain the electrochemical device; or stacking the separator, the positive electrode sheet, the separator, and the negative electrode sheet in order, and then fixing the four corners of the entire stacked structure to obtain an electrode assembly having a stacked structure, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag and sealing it to obtain the electrochemical device.

[0060] The third aspect of the present application provides an electronic device, wherein the electronic device includes the electrochemical device according to any one of the preceding embodiments. Thus, the electronic device has good use performance.

[0061] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the art. For example, the electronic device can include, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copier, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a household large storage battery, and a lithium ion capacitor.

[0062] Embodiment

[0063] 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.

[0064] Test method and equipment:

[0065] Test of the depth C and the width D of the pits:

[0066] After disassembling the lithium ion battery discharged at 0.2C to 3V, the separator was obtained, and the separator was washed in N-methyl pyrrolidone (NMP) for 1 min and dried.

[0067] Preparation of argon ion polishing (CP) sample with inorganic coating: after the separator was cut into a size of 6.0 mm x 6.0 mm and fixed on a sample stage, vacuum was drawn and argon was introduced, and the sample was polished along the thickness direction and the width direction of the separator under a voltage of 6 kV to obtain a CP sample with inorganic coating.

[0068] After obtaining the CP sample, the polished surface, i.e. the cross section, was placed under a scanning electron microscope (SEM) for observation. In any 10 μm x 10 μm test area on the cross section of the inorganic coating, each pit can be observed. The average value of the distance of the widest part of each pit along the width direction of the inorganic coating is recorded as the width D of the pit, and the average value of the distance of the deepest part is recorded as the depth C of the pit. For example, referring to FIG. 3, pits 121 can be observed on the cross section of the inorganic coating.

[0069] Test of the average particle size of the polymer particles:

[0070] The average particle size of the polymer particles was tested by Malvern 3000 laser particle size analyzer, refractive index: 1.59, and absorbance: 0.1.

[0071] Test of the adhesion F1 of the first surface of the separator to the positive electrode plate:

[0072] Discharge the lithium ion battery to 3V at 0.2C, remove the packaging bag, take out the electrode assembly, open the lithium ion battery from the negative electrode side, retain the interface of the positive electrode tab and the separator (the first surface of the positive electrode tab and the separator is adjacent), and then perform the following steps:

[0073] First step: use a punching slicer to punch the separator and the positive electrode tab into a test sample strip with a size of length x width = 20 cm x 3 cm;

[0074] Second step: hot-press composite treatment of the separator and the positive electrode tab, wherein the hot-press temperature is 80°C, the hot-press time is 60s, and the hot-press pressure is 1 MPa;

[0075] Third step: 180° peeling test of the hot-press composite treated separator and the positive electrode tab using a multi-grid photovoltaic solder strip peeling force testing machine, and the tested peeling force is the adhesion F1 of the first surface of the separator to the positive electrode tab.

[0076] Test of the adhesion of the separator to the negative electrode tab:

[0077] Discharge the lithium ion battery to 3V at 0.2C, remove the packaging bag, take out the electrode assembly, open the lithium ion battery from the positive electrode side, retain the interface of the negative electrode tab and the separator, and then perform the following steps:

[0078] First step: use a punching slicer to punch the separator and the negative electrode tab into a test sample strip with a size of length x width = 20 cm x 3 cm;

[0079] Second step: hot-press composite treatment of the separator and the negative electrode tab, wherein the hot-press temperature is 80°C, the hot-press time is 60s, and the hot-press pressure is 1 MPa;

[0080] Third step: 180° peeling test of the hot-press composite treated separator and the negative electrode tab using a multi-grid photovoltaic solder strip peeling force testing machine, and the tested peeling force is the adhesion of the separator to the negative electrode tab.

[0081] If the interface of the negative electrode tab and the separator is the interface between the first surface of the negative electrode tab and the separator, then the tested peeling force is the adhesion F2 of the first surface of the separator to the negative electrode tab; if the interface of the negative electrode tab and the separator is the interface between the second surface of the negative electrode tab and the separator, then the tested peeling force is the adhesion F3 of the second surface of the separator to the negative electrode tab.

[0082] Test of the impedance of the adhesion layer:

[0083] First step: measure the overall impedance of the "inorganic coating separator" using a separator impedance testing instrument;

[0084] Second step: measure the overall impedance of the "adhesion layer + inorganic coating separator" using a separator impedance testing instrument;

[0085] Third step: Adhesion layer impedance = "adhesion layer + inorganic coating separator" overall impedance - "inorganic coating separator" overall impedance.

[0086] The above-mentioned "inorganic coating separator" refers to a semi-finished separator in which the surface of the substrate is provided with an inorganic coating but not provided with an adhesion layer in the preparation of the separator; and the "adhesion layer + inorganic coating separator" refers to a finished separator obtained in the preparation of the separator.

[0087] Test of temperature conversion coefficient:

[0088] (1) 25℃ capacity test: charge at 0.2C constant current to 4.5V, charge at 4.5V constant voltage to 0.02C; stand for 5min; discharge at 0.2C constant current to 3.0V, record the discharge capacity;

[0089] (2) 0℃ capacity test: charge at 0.2C constant current to 4.5V, charge at 4.5V constant voltage to 0.02C; stand for 5min; discharge at 0.2C constant current to 3.0V, record the discharge capacity;

[0090] (3) Temperature conversion coefficient = 0℃ discharge capacity / 25℃ discharge capacity x 100%.

[0091] The greater the value of the temperature conversion coefficient, the better the kinetics of the lithium ion battery.

[0092] Example 1-1

[0093] Preparation of the separator

[0094] PE with a thickness of 5μm was selected as the substrate, and the porosity of the substrate was 35%;

[0095] The filler particles boehmite and the inorganic coating binder PAA (weight average molecular weight Mw = 20W) were mixed, deionized water was added as a solvent, and after stirring uniformly, an inorganic coating slurry with a solid content of 35wt% was formed; wherein the average particle size of the filler particles was 1μm, and the shape of the filler particles was hexahedral shape;

[0096] Polymer particles polyvinylidene fluoride (PVDF, Mw = 18W) and auxiliary binder PAA (Mw = 20W) were added to a stirrer, deionized water was added as a solvent, and after stirring uniformly, an adhesion layer slurry with a solid content of 10wt% was formed; wherein the average particle size Dv50 of the polymer particles was 1.0μm;

[0097] The inorganic coating slurry was coated on one surface of the substrate, dried at 35°C, and an inorganic coating layer was formed on one surface of the substrate, respectively; the adhesive layer slurry was coated on the surface of the inorganic coating layer away from the substrate and the other surface of the substrate by micro gravure roll coating, dried at 35°C, to obtain the separator. The structure of the separator is shown in FIG. 1, but is not limited to FIG. 1.

[0098] wherein the depth C of the recesses on the surface of the inorganic coating layer is 2.0 pm, the width D of the recesses is 0.5 pm, and the thickness E of the inorganic coating layer is 2.0 pm. The mass percentage content of the filler particles W1 is 97% and the mass percentage content of the inorganic coating binder W2 is 3% based on the mass of the inorganic coating layer. The mass percentage content of the polymer particles W3 is 99% and the mass percentage content of the auxiliary binder W4 is 1% based on the mass of the adhesive layer.

[0099] <Preparation of the positive electrode sheet>

[0100] The positive electrode active material LiCoO2, the positive electrode conductive agent conductive carbon black (Super P), and the positive electrode binder PVDF (Mw=50W) were mixed in a mass ratio of 97.5:1:1.5, N-methyl pyrrolidone (NMP) was added as a solvent, and the positive electrode slurry was stirred in a vacuum stirrer until the solid content was 75wt% and the system was uniform. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 pm, dried at 85°C, to obtain a positive electrode sheet coated with a single 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 coated with a double positive electrode active material layer. After cold pressing, cutting, and welding of the positive electrode tabs, a positive electrode sheet with a size of 74 mm x 851 mm was obtained for use.

[0101] <Preparation of the negative electrode sheet>

[0102] The negative electrode active material graphite, the negative electrode conductive agent conductive carbon black (Super P), the thickening agent carboxymethyl cellulose, and the binder styrene butadiene rubber (SBR) were mixed in a mass ratio of 97.5:1:0.5:1, and then deionized water was added as a solvent, and the negative electrode slurry was stirred in a vacuum stirrer until the solid content was 50wt% and the system was uniform. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 8 pm, dried at 85°C, to obtain a negative electrode sheet coated with a single 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 coated with a double negative electrode active material layer. After cold pressing, cutting, and welding of the negative electrode tabs, a negative electrode sheet with a size of 76 mm x 867 mm was obtained for use.

[0103] <Preparation of the electrolyte>

[0104] The organic solvent ethylene carbonate, methyl ethyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solution, then lithium salt lithium hexafluorophosphate was dissolved and mixed uniformly in the organic solvent to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0105] <Preparation of a lithium ion battery>

[0106] The above-prepared separator (denoted as separator A), negative electrode sheet, separator (denoted as separator B) and positive electrode sheet were stacked and wound in order to obtain an electrode assembly with a wound structure, with the first surface of separator A adjacent to the positive electrode sheet and the first surface of separator B adjacent to the positive electrode sheet. The electrode assembly was 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 was obtained.

[0107] Examples 1-2 to 1-17

[0108] Except for adjusting the relevant preparation parameters according to Table 1, the rest was the same as Example 1-1.

[0109] Examples 2-1 to 2-2

[0110] Except for adjusting the relevant preparation parameters according to Table 2, the rest was the same as Example 1-7.

[0111] Example 2-3

[0112] Except for adjusting the relevant preparation parameters according to Table 2 and adjusting the depth C of the pits in the <Preparation of a separator> to 1.5 μm, the rest was the same as Example 1-7.

[0113] Example 2-4

[0114] Except for adjusting the relevant preparation parameters according to Table 2 and adjusting the depth C of the pits in the <Preparation of a separator> to 1.0 μm, the rest was the same as Example 1-7.

[0115] Example 2-5

[0116] Except for adjusting the relevant preparation parameters according to Table 2 and adjusting the depth C of the pits in the <Preparation of a separator> to 0.5 μm, the rest was the same as Example 1-7.

[0117] Example 2-6

[0118] Except for adjusting the relevant preparation parameters according to Table 2, the rest was the same as Example 1-7.

[0119] Examples 3-1 to 3-10

[0120] The rest was the same as Example 1-7 except that the relevant preparation parameters were adjusted according to Table 3.

[0121] Examples 4-1 to 4-9

[0122] The rest was the same as Example 1-7 except that the relevant preparation parameters were adjusted according to Table 4.

[0123] Example 5-1

[0124] In the preparation of the separator, the rest was the same as Example 1-7 except that the inorganic coating layer was formed on both surfaces of the substrate at the same time, and the adhesive layer was arranged on the surface of each of the two inorganic coating layers away from the substrate.

[0125] In the preparation of the lithium ion battery, the rest was the same as Example 1-7 except that the separator prepared above (denoted as separator A), the negative electrode sheet, the separator (denoted as separator B), and the positive electrode sheet were stacked and wound in sequence to obtain the electrode assembly of the wound structure.

[0126] The preparation of the positive electrode sheet, the preparation of the negative electrode sheet, and the preparation of the electrolyte were the same as Example 1-7.

[0127] Comparative Example 1

[0128] The rest was the same as Example 1-1 except that the relevant preparation parameters were adjusted according to Table 1 and the thickness of the inorganic coating layer in the preparation of the separator was adjusted to 3.0 μm.

[0129] Comparative Examples 2 and 3

[0130] The rest was the same as Example 1-1 except that the relevant preparation parameters were adjusted according to Table 1.

[0131] Comparative Example 4

[0132] The rest was the same as Example 1-1 except that the relevant preparation parameters were adjusted according to Table 1 and the thickness of the inorganic coating layer in the preparation of the separator was adjusted to 2.5 μm.

[0133] Comparative Example 5

[0134] The rest was the same as Example 1-1 except that the relevant preparation parameters were adjusted according to Table 1 and the thickness of the inorganic coating layer in the preparation of the separator was adjusted to 3.0 μm.

[0135] The preparation parameters and performance parameters of each example and comparative example are shown in Tables 1 to 5.

[0136] Table 1

[0137] As can be seen from Examples 1-1 to 1-17, Comparative Examples 1 to 5, the separator in the examples of the present application has a suitable adhesion between the first surface of the separator and the positive electrode and the negative electrode by satisfying the following conditions for the recesses on the surface of the inorganic coating layer: the depth C of the recesses is 0.5 to 2 μm, and the ratio C / Dv50 between the depth of the recesses and the average particle size of the polymer particles in the adhesive layer is 0.25 to 4. When the separator is used in an electrochemical device, the electrochemical device has a higher temperature conversion coefficient on the basis of good safety performance. In the separators in the comparative examples, at least one of the depth C of the recesses or the ratio C / Dv50 between the depth of the recesses and the average particle size of the polymer particles in the adhesive layer is not within the range of the present application, and the separators in the comparative examples have too low or too high adhesion between the separators and the positive electrode and the negative electrode, which affects the internal resistance of the electrochemical device. When the separators in the comparative examples are used in an electrochemical device, the electrochemical device has a lower temperature conversion coefficient, and the too low adhesion F1 and F2 also makes the safety performance of the electrochemical device in the comparative examples poor.

[0138] The depth C of the recesses generally affects the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-1 to 1-4, Comparative Example 1, Comparative Example 2 and Comparative Example 4, the separators selected with the depth C of the recesses within the range of the present application have good adhesion between the separators and the positive electrode and the negative electrode, and when the separators are used in an electrochemical device, the electrochemical device has a higher temperature conversion coefficient.

[0139] The ratio C / Dv50 between the depth of the recesses and the average particle size of the polymer particles in the adhesive layer generally affects the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-1 to 1-4, Examples 1-11 to 1-17, Comparative Example 1, Comparative Examples 3 to 5, the separators selected with the ratio C / Dv50 between the depth of the recesses and the average particle size of the polymer particles in the adhesive layer within the range of the present application have good adhesion between the separators and the positive electrode and the negative electrode, and when the separators are used in an electrochemical device, the electrochemical device has a higher temperature conversion coefficient.

[0140] The width D of the recesses generally affects the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-4 to 1-10, the separators selected with the width D of the recesses within the range of the present application have good adhesion between the separators and the positive electrode and the negative electrode, and when the separators are used in an electrochemical device, the electrochemical device has a higher temperature conversion coefficient.

[0141] The average particle size Dv50 of the polymer particles generally affects the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-7, Examples 1-11 to Examples 1-17, the separator with the average particle size Dv50 of the polymer particles within the range of the present application has good adhesion between the positive electrode sheet and the negative electrode sheet, and the electrochemical device has a higher temperature conversion coefficient when the separator is applied to the electrochemical device.

[0142] Table 2

[0143] The thickness of the inorganic coating generally affects the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-7, Examples 2-1 to Examples 2-6, the separator with the thickness of the inorganic coating within the range of the present application has good adhesion between the positive electrode sheet and the negative electrode sheet, and the electrochemical device has a higher temperature conversion coefficient when the separator is applied to the electrochemical device.

[0144] Table 3

[0145] The mass percentage content of the filler particles and the inorganic coating binder in the inorganic coating generally affects the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-7, Examples 3-1 to Examples 3-6, the separator with the mass percentage content of the filler particles and the inorganic coating binder in the inorganic coating within the range of the present application has good adhesion between the positive electrode sheet and the negative electrode sheet, and the electrochemical device has a higher temperature conversion coefficient when the separator is applied to the electrochemical device. Compared with Examples 1-7, Examples 3-1 to Examples 3-5, the lithium ion battery of Example 3-6 has a higher temperature conversion coefficient, but the adhesion between the separator and the positive electrode sheet and the negative electrode sheet is lower, and the processing performance of the separator is poorer, and the safety performance of the lithium ion battery is relatively poor when the separator is applied to the lithium ion battery, therefore, the mass percentage content of the filler particles and the inorganic coating binder in Example 3-10 is not preferred.

[0146] The type of the filler particles and the inorganic coating binder generally affects the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-7, Examples 3-7 to Examples 3-10, the separator with the type of the filler particles and the inorganic coating binder within the range of the present application has good adhesion between the positive electrode sheet and the negative electrode sheet, and the electrochemical device has a higher temperature conversion coefficient when the separator is applied to the electrochemical device.

[0147] Table 4

[0148] The mass percentage of the polymer particles and the auxiliary binder in the adhesive layer generally affects the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-7, Examples 4-1 to 4-5, the separator with the mass percentage of the polymer particles and the auxiliary binder in the adhesive layer within the scope of the present application has good adhesion between the positive electrode sheet and the negative electrode sheet, and the electrochemical device has a higher temperature conversion coefficient when the separator is applied to the electrochemical device. Compared with Examples 1-7, Examples 4-1 to 4-4, the lithium ion battery of Example 4-5 has a higher temperature conversion coefficient, but the adhesion between the separator and the positive electrode sheet and the negative electrode sheet is lower, and the processing performance of the separator is poorer. When the separator is applied to the lithium ion battery, the safety performance of the lithium ion battery is relatively poor. Therefore, the mass percentage of the polymer particles and the auxiliary binder in the adhesive layer in Example 4-5 is not preferred. The adhesion between the separator and the positive electrode sheet and the negative electrode sheet in Example 4-5 is lower because the content of the auxiliary binder is less, which makes the adhesive layer prone to powdering in processes such as slitting, and the polymer particles fall off, the polymer particles decrease, which affects the adhesion of the separator to the positive electrode sheet and the negative electrode sheet, but also reduces the impedance, so that the temperature conversion coefficient of the lithium ion battery is higher.

[0149] The types of the polymer particles and the auxiliary binder generally affect the temperature conversion coefficient of the electrochemical device. As can be seen from Examples 1-7, Examples 4-6 to 4-9, the separator with the types of the polymer particles and the auxiliary binder within the scope of the present application has good adhesion between the positive electrode sheet and the negative electrode sheet, and the electrochemical device has a higher temperature conversion coefficient when the separator is applied to the electrochemical device.

[0150] Table 5

[0151] Note: "-" in Table 5 indicates that there is no corresponding parameter. Specifically, the F3 value of Example 5-1 is "-" because the surfaces on both sides of the separator in Example 5-1 are the first surfaces. Therefore, the interface between the negative electrode sheet and the separator is the interface between the negative electrode sheet and the first surface of the separator, and the adhesion test gives the adhesion F2 of the first surface of the separator to the negative electrode sheet. The F2 value of Example 1-7 is "-" because the surface on one side of the separator in Example 1-7 is the first surface, and the surface on the other side is the second surface. The second surface of the separator is adjacent to the negative electrode sheet. Therefore, the interface between the negative electrode sheet and the separator is the interface between the negative electrode sheet and the second surface of the separator, and the adhesion test gives the adhesion F3 of the second surface of the separator to the negative electrode sheet.

[0152] The structure of the separator also generally affects the temperature conversion coefficient of the lithium ion battery. As can be seen from Examples 1-7 and Example 5-1, the separator selected has a good adhesion between the positive electrode sheet and the negative electrode sheet, and the application of the separator to the electrochemical device has a higher temperature conversion coefficient. The reason why the adhesion F3 of the second surface of the separator in Example 1-7 to the negative electrode sheet is better than the adhesion F2 of the second surface of the separator in Example 5-1 to the negative electrode sheet is that in Example 1-7, the separator is provided with an adhesion layer on only one side, and the adhesion layer is directly provided on the substrate, resulting in a higher adhesion of the adhesion layer itself. However, in Example 5-1, the separator is provided with an inorganic coating on both sides of the separator, which improves the retention amount of the electrolyte of the separator, thereby further improving the temperature conversion coefficient of the lithium ion battery.

[0153] It should be noted that the relational terms herein such as first and second, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations 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.

[0154] Each of the embodiments in the specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the difference from other embodiments.

[0155] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A separator comprising a base material, and an inorganic coating layer and a bonding layer provided on one surface of the base material, the inorganic coating layer being provided between the base material and the bonding layer, the other surface of the base material being provided with the bonding layer, the bonding layer comprising polymer particles, the polymer particles having an average particle diameter of Dv50 μm. a surface of the inorganic coating layer has a plurality of pits, the pits having a depth of C μm, C and Dv50 satisfying: 0.25 ≤ C / Dv50 ≤ 4, 0.5 ≤ C ≤ 2.

2. The septum of claim 1, wherein, 0.4 ≤ Dv50 ≤ 1.

3. The septum of claim 1, wherein, a width D of the pits is 0.5 μm to 2 μm.

4. The septum of claim 1, wherein, a thickness E of the inorganic coating layer is 0.5 μm to 3 μm.

5. The separator according to any one of claims 1 to 4, wherein the separator satisfying at least one of the following (1) to (5): (1) 0.3 ≤ C / Dv50 ≤ 3.5; (2)0.5≤C≤1.0； (3) 0.5 ≤ Dv50 ≤ 1.0; (4) a width D of the pits is 0.5 μm to 1.5 μm; (5) a thickness E of the inorganic coating layer is 0.5 μm to 2 μm.

6. The septum of any one of claims 1 to 4, wherein, a thickness E of the inorganic coating layer is 0.5 μm to 1.5 μm.

7. The separator of any one of claims 1 to 4, wherein, the inorganic coating layer comprising filler particles and an inorganic coating layer binder, the filler particles comprising at least one of boehmite, alumina, zirconia, titania, magnesia, mullite, silicon carbide, or silicon nitride, the inorganic coating layer binder comprising at least one of polyvinyl alcohol, polyacrylic acid, hydroxymethyl cellulose, styrene butadiene rubber, or polymethyl methacrylate; a mass percentage of the filler particles is 95% to 99% and a mass percentage of the inorganic coating layer binder is 1% to 5% based on a mass of the inorganic coating layer.

8. The separator of any one of claims 1 to 4, wherein, the bonding layer further comprising an auxiliary binder, the polymer particles comprising at least one of polyvinylidene fluoride or polymethyl methacrylate, the auxiliary binder comprising at least one of polyvinyl alcohol, polyacrylic acid, hydroxymethyl cellulose, or styrene butadiene rubber; a mass percentage of the polymer particles is 97% to 99.5% and a mass percentage of the auxiliary binder is 0.5% to 3% based on a mass of the bonding layer.

9. The septum of claim 8, wherein, the other surface of the base material is further provided with an inorganic coating layer, the inorganic coating layer being provided between the base material and the bonding layer.

10. The separator of claim 1 or 9, wherein, the separator comprising a first surface provided with the inorganic coating layer and the bonding layer, the first surface having an adhesion to a positive electrode tab of 7 N / m to 40 N / m and an adhesion to a negative electrode tab of 6 N / m to 30 N / m.

11. An electrochemical device, wherein, the electrochemical device comprising the separator according to any one of claims 1 to 10. 12.An electronic device, wherein, the electronic device comprising the electrochemical device according to claim 11.

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