A wound electrode assembly, an electrochemical device, and an electronic device

Abstract

A wound electrode assembly, an electrochemical device, and an electronic device are disclosed. The wound electrode assembly includes an electrode sheet and an insulating layer (30) on at least one surface of the electrode sheet. The adhesive force between the insulating layer (30) and the electrode sheet surface in a first region of the wound electrode assembly is greater than that in a second region of the wound electrode assembly. This results in a higher adhesive force between the insulating layer (30) and the electrode sheet surface in the first region of the wound electrode assembly. When the electrode sheet in the second region is subjected to stress, the layers can slip slightly to each other, thereby releasing the stress. This reduces the stress concentration caused by the uniform adhesive force between the existing insulating film and the electrode sheet surface, reduces the deformation of the electrochemical device caused by stress concentration, and thus improves the safety of the electrochemical device.

Description

Technical Field

[0001] This application relates to the field of electrochemistry, specifically to a wound electrode assembly, an electrochemical device, and an electronic device. Background Technology

[0002] Lithium-ion batteries are characterized by high energy density, high operating voltage, low self-discharge rate, small size, and light weight, and are widely used in various fields such as energy storage, portable electronic devices, and electric vehicles. With the rapid development of electric vehicles and mobile electronic devices, people have increasingly higher performance requirements for lithium-ion batteries, such as higher energy density, safety, and cycle performance.

[0003] In existing lithium-ion batteries, the separator is typically an integral part of the electrode assembly, primarily serving to isolate the positive and negative electrodes and to ensure ion conduction while blocking electron conduction. A bonding layer of uniform viscosity is usually placed between the separator and the electrode sheets to improve the adhesion between them. However, for lithium-ion batteries with complex shapes, due to their unique structure, the internal stress conditions vary in different areas. Stress concentration can easily occur in some areas, reducing the safety of the lithium-ion battery. Therefore, a new type of lithium-ion battery is urgently needed to improve its safety. Summary of the Invention

[0004] The purpose of this application is to provide a wound electrode assembly, an electrochemical device, and an electronic device to improve the safety of the electrochemical device.

[0005] It should be noted that, in the specific embodiments 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.

[0006] The specific technical solution is as follows:

[0007] A first aspect of this application provides a wound electrode assembly including an electrode sheet and an insulating layer on at least one surface of the electrode sheet. The wound electrode assembly has a first region and a second region, wherein the adhesive force between the insulating layer and the surface of the electrode sheet is greater in the first region than the adhesive force between the insulating layer and the surface of the electrode sheet in the second region, and the second region is a roll-back region of the wound electrode assembly.

[0008] Overall, the wound electrode assembly of this application has a first region and a second region, wherein the second region corresponds to the roll-back area of ​​the electrode sheet in the wound electrode assembly, and the first region is the region in the wound electrode assembly other than the second region. In the first region of the wound electrode assembly, the adhesion force between the separator layer and the electrode sheet surface is greater than that in the second region of the wound electrode assembly, resulting in a higher adhesion force between the separator layer and the electrode sheet surface in the first region of the wound electrode assembly. When the electrode sheet in the second region is subjected to stress, the layers can generate slight slippage between each other, thereby releasing the stress. Therefore, it can reduce the stress concentration caused by the uniform adhesion force between the separator and the electrode sheet surface in the existing system, reduce the deformation of the lithium-ion battery caused by stress concentration during cycling, and thus improve the safety of the lithium-ion battery.

[0009] In one embodiment of this application, the difference between the adhesion force F1 between the insulating layer and the electrode surface in the first region and the adhesion force F2 between the insulating layer and the electrode surface in the second region is in the range of 1 N / m to 15 N / m, preferably in the range of 5 N / m to 10 N / m. For example, the lower limit of the difference between the adhesion force F1 between the insulating layer and the electrode surface in the first region and the adhesion force F2 between the insulating layer and the electrode surface in the second region may include the following values: 1 N / m, 2 N / m, 3 N / m, 4 N / m or 5 N / m; the upper limit of the difference between the adhesion force F1 between the insulating layer and the electrode surface in the first region and the adhesion force F2 between the insulating layer and the electrode surface in the second region may include the following values: 6 N / m, 8 N / m, 10 N / m, 12 N / m or 15 N / m.

[0010] By controlling the difference between the adhesion force F1 between the separator layer and the electrode surface in the first region and the adhesion force F2 between the separator layer and the electrode surface in the second region within the aforementioned range, deformation of the electrode in the second region due to stress concentration is avoided, thereby improving the safety of the lithium-ion battery.

[0011] In one embodiment of this application, the adhesion force F1 between the insulating layer and the electrode surface in the first region can be from 1 N / m to 30 N / m, preferably from 10 N / m to 20 N / m. It is understood that when the adhesion force F1 between the insulating layer and the electrode surface in the first region increases, the adhesion force F2 between the insulating layer and the electrode surface in the second region can also increase, as long as the adhesion force F1 between the insulating layer and the electrode surface in the first region is greater than the adhesion force F2 in the second region. The greater adhesion force F1 between the insulating layer and the electrode surface in the first region than the adhesion force F2 in the second region prevents the electrode in the second region from deforming due to stress concentration.

[0012] In one embodiment of this application, the adhesion force F2 between the insulating layer and the electrode surface in the second region can be from 2 N / m to 15 N / m, as long as the adhesion force F2 between the insulating layer and the electrode surface in the second region is less than the adhesion force F1 in the first region, thus avoiding deformation of the electrode in the second region due to stress concentration.

[0013] In one embodiment of this application, the wound electrode assembly includes a flat region and a roll-back region, wherein the adhesion between the insulating layer and the electrode surface in the flat region is greater than the adhesion between the insulating layer and the electrode surface in the roll-back region.

[0014] The aforementioned flat region refers to the area where the electrode sheet in the wound electrode assembly is flat, while the aforementioned roll-back region refers to the area where the electrode sheet in the wound electrode assembly is rolled back. Stress concentration is typically more likely to occur in the roll-back region of a wound electrode assembly because the electrode sheet in the roll-back region is bent and subjected to greater compression. Ordinary lithium-ion batteries exhibit a deformation rate of approximately 6% to 7% after 300 cycles, while current lithium-ion batteries with high-viscosity separators show a deformation rate exceeding 10% after 300 cycles. Furthermore, under pressure, the interface gap between the electrode sheets in the roll-back region decreases, resulting in less liquid retention space and fewer electrolyte transport channels. This makes the lithium-ion battery prone to purple spots and lithium plating, posing a safety hazard. Therefore, in this application, the adhesion force between the separator layer and the electrode sheet surface in the flat region can be set to be greater than the adhesion force between the separator layer and the electrode sheet surface in the roll-back region, thus resulting in a relatively lower adhesion force between the separator layer and the electrode sheet surface in the roll-back region. During the charging and discharging process of a lithium-ion battery containing the aforementioned wound electrode assembly, the layers in the roll-back area can undergo slight slippage, thereby releasing stress and preventing the electrode sheets in the roll-back area from deforming due to stress concentration, thus improving the safety of the lithium-ion battery.

[0015] In one embodiment of this application, the first region may specifically refer to the flat region of the wound electrode assembly, and the second region may specifically refer to the roll-back region of the wound electrode assembly. The adhesion force between the insulating layer and the electrode surface in the flat region can be from 1 N / m to 30 N / m, preferably from 10 N / m to 20 N / m. When the adhesion force between the insulating layer and the electrode surface in the flat region increases, the adhesion force between the insulating layer and the electrode surface in the roll-back region can also increase accordingly, as long as the adhesion force between the insulating layer and the electrode surface in the flat region is greater than the adhesion force in the roll-back region.

[0016] In one embodiment of this application, the electrode assembly is a wound structure, comprising second regions located on the left and right sides of the wound electrode assembly and a first region located in the middle of the wound electrode assembly. The thickness of the wound electrode assembly is denoted by L. The second region can refer to the area encompassed by a length of 1 / 2L from the outermost edge of each side of the wound electrode assembly when it is laid flat. The first region is the area of ​​the wound electrode assembly excluding the second region. It is understood that the electrode sheet in the second region is curved and rolled up, while the electrode sheet in the first region is straight.

[0017] In one embodiment of this application, the first region of the wound electrode assembly may include a first sub-region and a second sub-region. The first sub-region refers to the region within the first region that contains the tabs, i.e., the tab region of the wound electrode assembly. The second sub-region refers to the region within the first region that does not contain the tabs. The tabs have thickness. Due to the presence of the tabs, the electrode sheet in the first sub-region is more prone to stress concentration. In this application, the adhesion force F3 between the separator and the electrode sheet in the second sub-region can be greater than the adhesion force F4 between the separator and the electrode sheet in the first sub-region, thereby preventing deformation of the electrode sheet in the first sub-region due to stress concentration and further improving the safety of the lithium-ion battery.

[0018] In one embodiment of this application, the adhesion force F3 between the insulating layer and the electrode sheet in the second sub-region can be 15 N / m to 20 N / m, and the adhesion force F4 between the insulating layer and the electrode sheet in the first sub-region can be 10 N / m to 15 N / m, such that the adhesion force F3 between the insulating layer and the electrode sheet in the second sub-region is greater than the adhesion force F4 between the insulating layer and the electrode sheet in the first sub-region.

[0019] In one embodiment of this application, isolation layers with different adhesion forces to the electrode electrode surface can be provided in different regions of the electrode electrode, such that the adhesion force between the isolation layer and the electrode electrode surface in the first region is greater than the adhesion force between the isolation layer and the electrode electrode surface in the second region.

[0020] In an embodiment of the present application, an isolation layer with binders of different viscosities can be provided in different regions of the wound electrode assembly to control the adhesion force between the isolation layer and the surface of the electrode tab. For example, an isolation layer with a low-viscosity binder is provided in the second region, and an isolation layer with a high-viscosity binder is provided in the first region. In this way, the adhesion force between the isolation layer and the surface of the electrode tab in the first region can be made greater than the adhesion force between the isolation layer and the surface of the electrode tab in the second region, thereby preventing the electrode tab in the second region from deforming due to stress concentration. The viscosity of the binder in the isolation layer can be changed by adjusting the content of the binder in the slurry. The high viscosity mentioned in the present application can refer to the interfacial adhesion force F: 10 N / m < F ≤ 20 N / m, and the low viscosity can be the interfacial adhesion force F: 1 N / m ≤ F ≤ 10 N / m.

[0021] In an embodiment of the present application, the adhesion force between the isolation layer and the surface of the electrode tab can be controlled by increasing the content of the binder in the isolation layer in the region where high adhesion force is required. It can be understood that the isolation layer contains polymer fibers, and the polymer fibers can include binders. In the first region, the content of the binder in the polymer fibers can be 5 wt% to 25 wt%, preferably 8 wt% to 17 wt%. For example, the lower limit value of the content of the binder in the polymer fibers can include the following values: 5 wt%, 8 wt%, 10 wt%, 12 wt% or 15 wt%.

[0022] In the second region, the content of the binder in the polymer fibers can be 2 wt% to 20 wt%, preferably 6 wt% to 15 wt%. For example, the upper limit value of the content of the binder in the polymer fibers can include the following values: 8 wt%, 12 wt%, 15 wt%, 17 wt% or 20 wt%. The content of the binder in the polymer fibers in the first region is higher than that in the polymer fibers in the second region, so that the adhesion force between the isolation layer and the surface of the electrode tab in the first region is greater than the adhesion force between the isolation layer and the surface of the electrode tab in the second region.

[0023] In an embodiment of the present application, the fiber diameter of the polymer fibers in the isolation layer is 10 nm to 5 μm, preferably 20 nm to 2 μm. For example, the lower limit value of the fiber diameter of the polymer fibers can include the following values: 20 nm, 50 nm, 100 nm or 500 nm; the upper limit value of the fiber diameter of the polymer fibers can include the following values: 1000 nm, 1500 nm or 2 μm. By controlling the diameter of the polymer fibers within the above range, the structural strength of the polymer fibers can be improved.

[0024] In one embodiment of this application, the thickness of the separator layer is from 1 μm to 50 μm, preferably from 3 μm to 15 μm. By controlling the thickness of the separator layer within the above range, the separator layer can have excellent structural strength without being too thick, thereby increasing the relative content of active materials in the lithium-ion battery and thus improving the energy density of the lithium-ion battery.

[0025] In one embodiment of this application, the isolation layer may further contain inorganic particles, the volume of which accounts for no more than 40% of the total volume of solid material in the isolation layer, preferably 15% to 30%. For example, the lower limit of the volume of inorganic particles in the total volume of solid material in the isolation layer may include the following values: 5%, 9%, 18%, or 21%; the upper limit of the volume of inorganic particles in the total volume of solid material in the isolation layer may include the following values: 24%, 27%, 35%, or 40%. The addition of inorganic particles can improve the strength of the isolation layer.

[0026] In one embodiment of this application, the average particle size of the inorganic particles in the isolation layer is 20 nm to 5 μm, preferably 50 nm to 2 μm. For example, the lower limit of the average particle size of the inorganic particles may include 50 nm, 100 nm, or 500 nm; the upper limit of the average particle size of the inorganic particles may include 1000 nm, 1500 nm, or 2 μm. By controlling the average particle size of the inorganic particles within the above range, the structural strength of the isolation layer can be further improved.

[0027] In one embodiment of this application, the inorganic particles may include a binder to improve their adhesion. In the first region, the binder content in the inorganic particles is 4 wt% to 7 wt%, for example, 4 wt%, 5 wt%, 6 wt%, or 7 wt%.

[0028] In the second region, the binder content in the inorganic particles is 3 wt% to 15 wt%, for example, 3 wt%, 5 wt%, 7 wt%, 10 wt%, or 15 wt%. It can be seen that the binder content in the inorganic particles in the second region is higher than in the first region, which can give the isolation layer in the second region higher strength. However, the inorganic particles only account for no more than 40% of the total volume of solid matter in the isolation layer, indicating a higher proportion of polymer fibers in the isolation layer. Therefore, the inventive objective of this application can be achieved by adjusting the binder content in the polymer fibers of the first and second regions.

[0029] In one embodiment of this application, the polymer fiber may further contain inorganic fillers, the content of which is 5 wt% to 10 wt%, for example, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%. By controlling the content of inorganic fillers in the polymer fiber within the above range, the polymer fiber can have good structural strength. However, excessive amounts of inorganic fillers should not be added, otherwise the bonding performance of the polymer fiber will be affected.

[0030] This application does not impose any particular restrictions on polymer fibers, as long as they meet the requirements of this application. For example, polymer fibers may include at least one of the following: polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene ether, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride-hexafluoropropylene, or polyvinylidene fluoride-co-trifluorochloroethylene, or derivatives thereof.

[0031] This application does not impose any particular restrictions on the inorganic materials of the inorganic particles in the isolation layer, nor does it impose any particular restrictions on the inorganic materials of the inorganic fillers in the polymer fibers, as long as they meet the requirements of this application. For example, the aforementioned inorganic materials may include at least one of the following: hafnium oxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide, aluminum hydroxide, lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS2 glass, P2S5 glass, lithium oxide, lithium fluoride, lithium hydroxide, lithium carbonate, lithium aluminate, lithium germanium phosphosulfur ceramic, or garnet ceramic.

[0032] This application does not impose any particular restrictions on the adhesive, as long as it meets the requirements of this application. For example, it may include at least one of polyvinyl alcohol, polytetrafluoroethylene, styrene-butadiene rubber, sodium carboxymethyl cellulose, polystyrene acid, polybutyl acrylate, polyacrylonitrile, polyurethane, or acrylonitrile copolymer.

[0033] This application does not impose any particular limitation on the preparation method of the isolation layer; any preparation method known to those skilled in the art can be used, such as the following preparation method:

[0034] The polymer and binders of different contents are dispersed in an organic solvent and stirred until the slurry viscosity is stable, resulting in slurry A and slurry B with different binder contents, wherein the binder content in slurry A is greater than that in slurry B.

[0035] Inorganic particles and a binder are dispersed in an organic solvent and stirred until the slurry viscosity stabilizes to prepare slurry C and slurry D. The binder content in slurry C can be greater than that in slurry D, or the binder content in slurry C and slurry D can be the same.

[0036] An insulating layer is obtained by alternately spraying slurry A and slurry C in the first region of the electrode sheet using an electrospinning device and an electrospraying device.

[0037] In the second region of the electrode sheet, an insulating layer is obtained by alternately spraying slurry B and slurry D using an electrospinning device and an electrospraying device. The resulting insulating layer has a higher binder content in the first region than in the second region. Both the electrospinning device and the electrospraying device are connected to voltage regulators.

[0038] If it is necessary to prepare an electrode sheet with an isolation layer on both sides, the above steps can be repeated on the back side of the electrode sheet to obtain an electrode sheet with an isolation layer on both sides.

[0039] Furthermore, if it is necessary to further improve the strength of the polymer fibers, inorganic fillers, such as calcium oxide, can be added to the polymer-containing slurry. The inorganic fillers and inorganic particles in this application can be selected from the same inorganic material or from different inorganic materials.

[0040] Those skilled in the art should understand that this application can prepare an isolation layer on the surface of the positive electrode sheet or on the surface of the negative electrode sheet. Of course, it can also prepare isolation layers on the surfaces of both the positive and negative electrode sheets simultaneously, as long as the adhesion between the isolation layer and the electrode sheet surface in different regions of the wound electrode assembly is not uniform. All of these should fall within the protection scope of this application.

[0041] For example, the aforementioned insulating layer can be provided on one side of the positive electrode, or on one side of the negative electrode, or on both sides of the positive electrode, or on both sides of the negative electrode, or on one side of the positive electrode and one side of the negative electrode, as long as the adhesion between the insulating layer and the electrode electrode surface in different regions of the wound electrode assembly is not uniform.

[0042] The positive electrode sheet in this application is not particularly limited, as long as it can achieve the purpose of this application. For example, the positive electrode sheet typically includes a positive current collector and a positive active material layer. The positive current collector is not particularly limited and can be any positive current collector known in the art, such as aluminum foil, aluminum alloy foil, or composite current collectors. The positive active material layer includes a positive active material, which is not particularly limited and can be any positive active material known in the art, for example, it can include at least one of lithium nickel cobalt manganese oxide (811, 622, 523, 111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate.

[0043] The negative electrode sheet in this application is not particularly limited, as long as it achieves the purpose of this application. For example, the negative electrode sheet typically includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is not particularly limited; any negative electrode current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collectors. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material is not particularly limited; any negative electrode active material known in the art can be used. For example, it can include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon, silicon-carbon, lithium titanate, etc.

[0044] The lithium-ion battery of this application also includes an electrolyte, which may be one or more of gel electrolyte, solid electrolyte and electrolyte solution, and the electrolyte solution includes lithium salt and non-aqueous solvent.

[0045] In some embodiments of this application, the lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate. For example, LiPF6 can be selected as the lithium salt because it can provide high ionic conductivity and improve cycling characteristics.

[0046] The non-aqueous solvent may be a carbonate compound, a carboxylic acid ester compound, an ether compound, other organic solvents, or a combination thereof.

[0047] The aforementioned carbonate compounds may be chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.

[0048] Examples of the aforementioned chain carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof. Examples of fluorinated carbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.

[0049] Examples of the above-mentioned carboxylic acid ester compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonic acid lactone, caprolactone, and combinations thereof.

[0050] Examples of the above-mentioned ether compounds are dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0051] Examples of other organic solvents mentioned above include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.

[0052] This application also provides an electrochemical device, including an electrode assembly and an electrolyte, wherein the electrode assembly is a wound electrode assembly as described in any of the above embodiments, and the electrochemical device has good safety performance.

[0053] This application also provides an electronic device comprising the electrochemical device described in the embodiments of this application, which has good safety performance.

[0054] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0055] The fabrication process of electrochemical devices is well known to those skilled in the art, and this application does not impose any particular limitations. For example, an electrochemical device can be manufactured through the following process: overlapping the positive and negative electrodes via a separator, and then, as needed, winding, folding, or performing other operations, placing them into a housing; injecting the electrolyte into the housing and sealing it; wherein the separator used is the separator described above provided in this application. Furthermore, overcurrent protection elements, conductive plates, etc., can be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0056] This application provides a wound electrode assembly in which the adhesion force between the separator layer and the electrode surface in the first region of the wound electrode assembly is greater than that in the second region of the wound electrode assembly. This results in a higher adhesion force between the separator layer and the electrode surface in the first region of the wound electrode assembly. When the electrode in the second region is subjected to stress, the layers can undergo slight slippage, thereby releasing the stress. Therefore, it can reduce the occurrence of stress concentration caused by the uniform adhesion force between the separator and the electrode surface in existing systems, reduce the deformation of lithium-ion batteries caused by stress concentration, and thus improve the safety of lithium-ion batteries. Attached Figure Description

[0057] To more clearly illustrate the technical solutions of this application and the prior art, the accompanying drawings used in the embodiments and the prior art are briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application.

[0058] Figure 1 This is a schematic diagram of the structure of a lithium-ion battery according to one embodiment of this application;

[0059] Figure 2 This is a schematic diagram of the structure of a wound electrode assembly according to another embodiment of this application (along the surface direction of the electrode sheet);

[0060] Figure 3This is a schematic diagram of an embodiment of the present application in which an isolation layer is disposed on an electrode sheet coated on one side.

[0061] Figure 4 This is a schematic diagram of a structure in one embodiment of the present application, in which an isolation layer is disposed on a double-coated positive electrode sheet;

[0062] Figure 5 This is a schematic diagram of a structure in one embodiment of the present application, in which an isolation layer is disposed on a double-coated negative electrode sheet;

[0063] Figure 6 This is a schematic diagram of the structure of a spinning and electro-spraying device according to one embodiment of this application;

[0064] Figure 7 This is a schematic diagram of an electrode stacking structure during the adhesion test of this application.

[0065] Reference numerals: 1: First sub-region; 2: Second sub-region; 3: Current collector layer; 4: Double-sided adhesive; 5: Tension-supporting plate; 6: Pressure plate; 7: Adhesive application area; 8: Packaging bag; 9: Electrode active material layer; 10: Positive current collector; 11: Tab; 20: Positive active material layer; 30: Separator layer; 40: Negative active material layer; 50: Negative current collector; 60: Electrospinning equipment; 70: Electrospraying equipment; 80: Voltage regulator. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other technical solutions obtained by those skilled in the art based on the embodiments of this application fall within the scope of protection of this application.

[0067] Figure 1 A schematic diagram of the structure of a wound electrode assembly according to one embodiment of this application is shown. (Refer to...) Figure 1 The electrode assembly is a wound structure, which includes a second region located at the left and right ends of the wound electrode assembly and a first region located in the middle of the wound electrode assembly.

[0068] like Figure 1 As shown, in one embodiment of this application, the wound electrode assembly may include a first sub-region 1 and a second sub-region 2, wherein the first sub-region 1 refers to... Figure 1 The first region shown contains the region of tab 11, and the second sub-region refers to... Figure 1 The first region shown does not include the area of ​​electrode 11.

[0069] Figure 2This is a schematic diagram of the structure of a wound electrode assembly in one embodiment of this application (along the surface direction of the electrode sheet). In one embodiment of this application, such as... Figure 2 As shown, the viscosity of the adhesive used in the second region is lower than that of the adhesive used in the first region, so that the adhesion between the insulating layer and the electrode surface in the first region is greater than that between the insulating layer and the electrode surface in the second region.

[0070] In one embodiment of this application, the insulating layer may be disposed on at least one surface of the electrode sheet, for example, it may be as follows: Figure 3 The structure shown, where an insulating layer is provided on one side of the electrode sheet, can also be... Figure 4 The structure shown, where the positive electrode sheet has an insulating layer on both sides, can also be... Figure 5 The structure shown has an insulating layer on both sides of the negative electrode sheet. Specifically, for example, Figure 3 An isolation layer 30 is provided on one surface of the positive electrode and the negative electrode. Figure 4 Both surfaces of the positive electrode are provided with an isolation layer 30. Figure 5 Both surfaces of the negative electrode sheet are provided with an isolation layer 30. The positive electrode sheet includes a positive current collector 10 and a positive active material layer 20, and the negative electrode sheet includes a negative current collector 50 and a negative active material layer 40.

[0071] Figure 6 This is a schematic diagram of the structure of a spinning and electro-spraying device in one embodiment of this application. The device includes an electrospinning device 60, an electro-spraying device 70, and a voltage regulator 80.

[0072] Example

[0073] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0074] Test methods and equipment:

[0075] Lithium-ion battery deformation test:

[0076] After the lithium-ion battery reaches its full capacity, i.e., after the battery has completed its first charge-discharge cycle and is charged to half capacity, the thickness of the first and second regions (winding areas) of the lithium-ion battery is measured. Three points are taken in each region, and the thickness data H0 is recorded. After 300 charge-discharge cycles, the lithium-ion battery is kept in the same charging state (e.g., the same voltage) as when the capacity was reached. The same measurement locations are selected, and the same measuring tools are used to measure the thickness of the lithium-ion battery, and the data H1 is recorded. The deformation rate at each measurement location is calculated using the following expression:

[0077] Deformation rate at measurement location = (H1 - H0) / H0 × 100%

[0078] The calculation results at different locations are then averaged to obtain the deformation rate of the lithium-ion battery.

[0079] Lithium-ion battery discharge energy density test:

[0080] The lithium-ion battery was left to stand at room temperature for 30 minutes, then charged at a constant current rate of 0.05C to a voltage of 4.45V. The electrochemical device was then discharged at a rate of 0.05C to 3.00V. This charge / discharge cycle was repeated three times to complete the formation of the lithium-ion battery. After formation, the battery was charged at a constant current and constant voltage rate of 0.2C to a voltage of 4.45V, then discharged at a rate of 0.2C to 3.00V. The discharge energy was recorded, and the energy density at 0.2C discharge was calculated.

[0081] Energy density (Wh / L) = Discharge energy (Wh) / Lithium-ion battery volume (L)

[0082] Lithium-ion battery capacity retention test:

[0083] The test environment temperature was 25℃. The comparative and example samples used the same charging process: the battery was charged at a constant current of 0.7C until the cutoff voltage was 4.5V, and then charged at a constant voltage until the cutoff current was 0.05C. After the battery was fully charged, it was left to stand for 5 minutes, and then discharged at a current of 0.5C to 3.0V. This is one charge-discharge cycle. After repeating this charge-discharge cycle 300 times, the discharge capacity after 300 cycles was divided by the discharge capacity of the first cycle to obtain the cycle capacity retention rate.

[0084] Adhesion test:

[0085] Ordinary electrode sheets (positive or negative electrode sheets) and electrode sheets with integrated insulating layers are cut into strips of 50mm × 100mm, and then the two are stacked to form a shape like... Figure 7The sandwich structure shown allows the two sides of the separator 30 to contact the electrode active material layer 9. The tension holding plate 5 is bonded to the current collector layer 3 by double-sided adhesive 4. The sandwich structure is then placed in a packaging bag 8 and sealed. Electrolyte (with the same composition and concentration as that in lithium-ion batteries) is then added to the sandwich structure. The bag is left to stand until the surface of the electrode sheet of the integrated separator is completely wetted. The packaging bag containing the sandwich structure is then placed on a press plate 6. The press plate 6 has a heating function. After the press plate is heated to 90°C, the press applies a pressure of 1 MPa for 30 minutes to complete the pressure release. After the press plate cools down, the pressed object is removed and the adhesion force is tested.

[0086] Remove the heat-pressed sandwich structure from the packaging bag 8 and transfer it to the tensile testing machine. Fix the end of the tensile clamping plate 5 to the lower clamp of the tensile testing machine, keeping it perpendicular to the ground. Fix the adhesive portion 7 of the release layer 30 to the upper clamp of the tensile testing machine, ensuring the upper clamp is parallel to the sample surface. Clamp the upper and lower clamps with fixtures. Ensure the operating table controls the start of the tensile testing machine. After the upper clamp is pre-stretched, perform the tensile test. Save the data after completion; the test is then complete.

[0087] Example 1

[0088] <Preparation of the positive electrode>

[0089] a) Coating of positive electrode active material

[0090] Lithium cobalt oxide (CCO), conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97.5:1:1.5. N-methylpyrrolidone (NMP) was then added as a solvent to prepare a slurry with a solid content of 75%, and the mixture was stirred until homogeneous. The slurry was then uniformly coated onto one surface of a 12 μm thick aluminum foil and dried at 90°C to obtain a single-sided coated CCO electrode sheet with a CCO active material layer thickness of approximately 100 μm.

[0091] b) <Preparation of the isolation layer>

[0092] Slurry preparation :

[0093] Polyvinylidene fluoride (PVDF) is used as the polymer, polyvinyl alcohol (PVA) is used as the binder, and alumina (Al2O3) is used as the inorganic particles with an average particle size of 200 nm.

[0094] PVDF and PVA were dispersed in a mixed solvent of dimethylformamide (DMF):acetone = 7:3 and stirred until the slurry viscosity stabilized to obtain slurry A with a solid content of 25%, wherein the mass ratio of PVDF to PVA was 91.3:8.7.

[0095] PVDF and PVA were dispersed in a mixed solvent of DMF:acetone = 7:3 and stirred until the slurry viscosity stabilized to obtain slurry B with a solid content of 25%, wherein the mass ratio of PVDF to PVA was 94:6.

[0096] Al2O3 and PVA were dispersed in a mixed solvent of DMF:acetone = 7:3 and stirred until the slurry viscosity stabilized, resulting in slurry C with a solid content of 40%, wherein the mass ratio of Al2O3 to PVA was 95.9:4.1.

[0097] Al2O3 and PVA were dispersed in a mixed solvent of DMF:acetone = 7:3 and stirred until the slurry viscosity stabilized, resulting in slurry D with a solid content of 40%, wherein the mass ratio of Al2O3 to PVA was 96.8:3.2.

[0098] Preparation of the first region isolation layer :

[0099] In the first region of the electrode sheet, paste A and paste C are used... Figure 6 The electrospinning equipment 60 and the electrospraying equipment 70 are used to alternately spray the coating to obtain an isolation layer with a thickness of 7 μm.

[0100] Preparation of the isolation layer in the roll-back region :

[0101] In the second region (i.e., the roll-back region) of the electrode sheet, slurry B and slurry D are alternately sprayed by electrospinning equipment 60 and electrospraying equipment 70 to obtain an isolation layer with a thickness of 7 μm, a porosity of 48%, and a fiber diameter of 100 nm.

[0102] c) <Preparation of double-sided coated electrode sheets>

[0103] Repeat steps a and b above on the back of the positive electrode sheet, then vacuum dry at 40°C to remove dispersants such as DMF, and then heat treat at 80°C for 6 hours to complete the crosslinking process, thus obtaining a positive electrode sheet with a double-sided integrated isolation layer. Then cut the positive electrode sheet into sheets with a specification of 74mm×867mm and weld tabs for later use.

[0104] <Preparation of Negative Electrode Sheets>

[0105] Graphite, conductive carbon black, and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, and deionized water was added as a solvent to prepare a slurry with a solid content of 70%, which was then stirred evenly. The slurry was uniformly coated onto the copper foil of the negative electrode current collector, dried at 110°C, and cold-pressed to obtain a single-sided coated negative electrode sheet with a negative electrode active material layer thickness of 150 μm.

[0106] After completing the above steps, repeat the same steps on the back of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. After coating, cut the negative electrode sheet into sheets with dimensions of 76mm × 851mm and weld on tabs for later use.

[0107] <Preparation of Electrolyte>

[0108] In a dry argon atmosphere, organic solvents ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate are mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to obtain an organic solution. Then, lithium hexafluorophosphate is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0109] <Preparation of Lithium-ion Batteries>

[0110] The prepared negative electrode sheet and the positive electrode sheet with integrated isolation layer are stacked and wound into an electrode assembly. The positive electrode tab and the negative electrode tab are set in the first area of ​​the wound electrode assembly. Then, after applying adhesive to the end of the winding structure, the tab, and the positive electrode head area, it is placed in an aluminum-plastic film. After top and side sealing, liquid injection, and encapsulation, a lithium-ion battery is obtained.

[0111] Examples 2-9

[0112] In Example 1, "Preparation of the Isolation Layer", except for adjusting the binder content in slurry A, slurry B, slurry C, and slurry D so that the binder content in the polymer fiber in the first region, the binder content in the inorganic particles in the first region, the binder content in the polymer fiber in the second region, and the binder content in the inorganic particles in the second region are as shown in Table 1 for each example, everything else is the same as in Example 1.

[0113] Example 10

[0114] Except for the preparation of the positive electrode and the preparation of the negative electrode, which are different from those in Example 1, the rest are the same as in Example 1.

[0115] <Preparation of the positive electrode>

[0116] Lithium cobalt oxide (CCO), conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97.5:1:1.5. N-methylpyrrolidone (NMP) was then added as a solvent to prepare a slurry with a solid content of 75%, which was stirred until homogeneous. The slurry was uniformly coated onto one surface of a 12 μm thick aluminum foil, dried at 90°C, and cold-pressed to obtain a single-sided CCO electrode sheet with a 100 μm thick CCO active material layer. The above steps were repeated on the other surface of the same CCO electrode sheet to obtain a double-sided CCO electrode sheet. The CCO electrode sheet was cut into 74 mm × 867 mm pieces and aluminum tabs were welded on for later use.

[0117] <Preparation of Negative Electrode Sheets>

[0118] a) Coating of negative electrode active material

[0119] Graphite, conductive carbon black, and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, and deionized water was added as a solvent to prepare a slurry with a solid content of 70%, which was then stirred evenly. The slurry was uniformly coated onto the copper foil of the negative electrode current collector and dried at 110°C to obtain a single-sided coated positive electrode sheet with a negative electrode active material layer thickness of approximately 100 μm.

[0120] b) <Preparation of the isolation layer>

[0121] Adjust the binder content in slurry A, slurry B, slurry C, and slurry D so that the binder content in the polymer fiber of the first region, the binder content in the inorganic particles of the first region, the binder content in the polymer fiber of the second region, and the binder content in the inorganic particles of the second region in the negative electrode sheet are the same as those shown in Table 1 Example 10, except that the contents are the same as those in Example 1.

[0122] c) <Preparation of double-sided coated electrode sheets>

[0123] Repeat steps a and b above on the back of the negative electrode sheet, then vacuum dry at 40°C to remove dispersants such as DMF, and then heat treat at 80°C for 6 hours to complete the crosslinking process, thus obtaining a negative electrode sheet with a double-sided integrated isolation layer. Then cut the negative electrode sheet into sheets with a specification of 74mm×851mm for later use.

[0124] Example 11

[0125] Except for coating the insulating layer on one side of the positive electrode sheet, the rest is the same as in Example 3.

[0126] Example 12

[0127] Except for adjusting the thickness of the isolation layer on one side to 3 μm, everything else is the same as in Example 3.

[0128] Example 13

[0129] Except for adjusting the thickness of the isolation layer on one side to 15 μm, everything else is the same as in Example 3.

[0130] Example 14

[0131] Except for the following in the <Preparation of the Isolation Layer> section, where the polymer is polyimide, the binder is styrene-butadiene rubber, the inorganic particles are magnesium oxide with an average particle size of 50 nm, and the fiber diameter of the isolation layer is 20 nm, the rest is the same as in Example 3.

[0132] Example 15

[0133] Except for the following in the <Preparation of the Isolation Layer> section, where the polymer is polyacrylonitrile, the binder is sodium carboxymethyl cellulose, the inorganic particles are calcium oxide with an average particle size of 2 μm, and the fiber diameter of the isolation layer is 2 μm, the rest is the same as in Example 3.

[0134] Example 16

[0135] In Example 1, "Preparation of the Isolation Layer", except for adjusting the binder content in slurry A, slurry B, slurry C, and slurry D so that the binder content in the polymer fiber in the first region, the binder content in the inorganic particles in the first region, the binder content in the polymer fiber in the second region, and the binder content in the inorganic particles in the second region are as shown in Table 1 for each example, everything else is the same as in Example 1.

[0136] Example 17

[0137] In Example 1, "Preparation of the Isolation Layer", except for adjusting the binder content in slurry A, slurry B, slurry C, and slurry D so that the binder content in the polymer fiber in the first region, the binder content in the inorganic particles in the first region, the binder content in the polymer fiber in the second region, and the binder content in the inorganic particles in the second region are as shown in Table 1 for each example, everything else is the same as in Example 1.

[0138] Example 18

[0139] In the <Preparation of Lithium-ion Batteries>, except that the positive and negative electrode tabs are placed in the second region of the wound electrode assembly, the rest is the same as in Example 1.

[0140] Example 19

[0141] Except for the preparation of the isolation layer, which is different from that in Example 1, everything else is the same as in Example 1.

[0142] <Preparation of the isolation layer>

[0143] Slurry preparation :

[0144] Polyvinylidene fluoride is selected as the polymer, polyvinyl alcohol is selected as the binder, and alumina is selected as the inorganic particles. The average particle size of the inorganic particles is 200 nm.

[0145] PVDF and PVA were dispersed in a mixed solvent of DMF:acetone = 7:3 and stirred until the slurry viscosity stabilized to obtain slurry A with a solid content of 25%, wherein the mass ratio of PVDF to PVA was 83:17.

[0146] PVDF and PVA were dispersed in a mixed solvent of DMF:acetone = 7:3 and stirred until the slurry viscosity stabilized to obtain slurry B with a solid content of 25%, wherein the mass ratio of PVDF to PVA was 85.6:14.4.

[0147] Al2O3 and PVA were dispersed in a mixed solvent of DMF:acetone = 7:3 and stirred until the slurry viscosity stabilized, resulting in slurry C with a solid content of 40%, wherein the mass ratio of Al2O3 to PVA was 95.2:4.8.

[0148] Al2O3 and PVA were dispersed in a mixed solvent of dimethylformamide:acetone = 7:3 and stirred until the slurry viscosity stabilized, resulting in slurry D with a solid content of 40%, wherein the mass ratio of Al2O3 to PVA was 95.5:4.5.

[0149] Preparation of the second sub-region isolation layer in the first region :

[0150] In the second sub-region within the first region of the electrode sheet, pastes A and C are used... Figure 6 The electrospinning equipment 60 and the electrospraying equipment 70 are used alternately to spray a 7μm thick isolation layer.

[0151] Preparation of the first sub-region isolation layer in the first region :

[0152] In the first sub-region of the first region of the electrode sheet, slurry B and slurry D are alternately sprayed by electrospinning equipment 60 and electrospraying equipment 70 to obtain an isolation layer with a thickness of 7μm.

[0153] Preparation of the second region isolation layer :

[0154] In the second region of the electrode sheet, slurry B and slurry D are alternately sprayed by electrospinning equipment 60 and electrospraying equipment 70 to obtain an isolation layer with a thickness of 7 μm, a porosity of 48%, and a fiber diameter of 100 nm.

[0155] Example 20

[0156] In Example 19, "Preparation of the Isolation Layer", except for adjusting the binder content in slurry A, slurry B, slurry C, and slurry D so that the binder content in the polymer fiber of the second sub-region, the binder content in the inorganic particles of the second sub-region, the binder content in the polymer fiber of the first sub-region, and the binder content in the inorganic particles of the first sub-region are as shown in Table 2 corresponding to Example 20, everything else is the same as in Example 19.

[0157] Example 21

[0158] In Example 19, "Preparation of the Isolation Layer", except for adjusting the binder content in slurry A, slurry B, slurry C, and slurry D so that the binder content in the polymer fiber of the second sub-region, the binder content in the inorganic particles of the second sub-region, the binder content in the polymer fiber of the first sub-region, and the binder content in the inorganic particles of the first sub-region are as shown in Table 2 corresponding to Example 21, everything else is the same as in Example 19.

[0159] Comparative Example 1

[0160] <Preparation of the positive electrode>

[0161] Lithium cobalt oxide (CCO), conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97.5:1:1.5. N-methylpyrrolidone (NMP) was then added as a solvent to prepare a slurry with a solid content of 75%, which was stirred until homogeneous. The slurry was uniformly coated onto one surface of a 12 μm thick aluminum foil, dried at 90°C, and cold-pressed to obtain a positive electrode sheet with a 100 μm thick CCO active material layer. The above steps were repeated on the other surface of the same positive electrode sheet to obtain a positive electrode sheet with a double-sided coating of CCO active material. The positive electrode sheet was cut into 74 mm × 867 mm pieces and aluminum tabs were welded on for later use.

[0162] <Preparation of Negative Electrode Sheets>

[0163] Graphite, conductive carbon black, and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, and deionized water was added as a solvent to prepare a slurry with a solid content of 70%, which was then stirred evenly. The slurry was uniformly coated onto the copper foil of the negative electrode current collector, dried at 110°C, and cold-pressed to obtain a single-sided coated negative electrode sheet with a negative electrode active material layer thickness of 150 μm.

[0164] After completing the above steps, repeat the same steps on the back of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. After coating, cut the negative electrode sheet into sheets with dimensions of 76mm × 851mm and weld on tabs for later use.

[0165] <Preparation of the separating membrane>

[0166] A porous polyethylene (PE) separator was selected, with an average pore size of 0.073 μm, a porosity of 26%, and a separator thickness of 20 μm.

[0167] <Preparation of Electrolyte>

[0168] In a dry argon atmosphere, organic solvents ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate are mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to obtain an organic solution. Then, lithium hexafluorophosphate is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0169] <Preparation of Lithium-ion Batteries>

[0170] The prepared positive electrode sheet, separator and negative electrode sheet are stacked and wound into an electrode assembly. After adhesive is applied to the end of the winding structure, the tab, and the positive electrode head area, it is placed in an aluminum-plastic film. After top and side sealing, liquid injection and encapsulation, a lithium-ion battery is obtained.

[0171] Comparative Example 2

[0172] Except for the preparation of the separating membrane, which is different from Comparative Example 1, everything else is the same as Comparative Example 1.

[0173] <Preparation of the separating membrane>

[0174] Al₂O₃ and polyacrylate were mixed at a mass ratio of 90:10 and dissolved in deionized water to form a ceramic slurry with a solid content of 50%. The ceramic slurry was then uniformly coated onto one side of a porous polyethylene (PE) substrate (7 μm thick, average pore size 0.073 μm, porosity 26%) using a microgravure coating method. After drying, a bilayer structure of ceramic coating and porous substrate was obtained, with the ceramic coating having a thickness of 50 μm.

[0175] PVDF and polyacrylate were mixed at a mass ratio of 96:4 and dissolved in deionized water to form a polymer slurry with a solid content of 50%. The polymer slurry was then uniformly coated onto both surfaces of the above-mentioned ceramic coating and porous substrate bilayer structure using a microgravure coating method. After drying, a release film was obtained, wherein the thickness of the single-layer coating formed by the polymer slurry was 2 μm.

[0176] Comparative Example 3

[0177] Except for the use of non-woven fabric for the isolation membrane, the rest is the same as Comparative Example 1, and the thickness of the non-woven fabric is 20μm.

[0178] Comparative Example 4

[0179] Except for the preparation of the positive electrode sheet, which is different from Example 1, the rest is the same as Example 1.

[0180] <Preparation of the positive electrode>

[0181] a) Coating of positive electrode active material

[0182] Lithium cobalt oxide, conductive carbon black, and PVDF were mixed in a mass ratio of 97.5:1:1.5, and NMP was added as a solvent to prepare a slurry with a solid content of 75%, which was then stirred evenly. The slurry was uniformly coated on one surface of an aluminum foil with a thickness of 12 μm and dried at 90°C to obtain a single-sided coated positive electrode sheet with a positive active material layer thickness of approximately 100 μm.

[0183] b) <Preparation of the isolation layer>

[0184] PVDF and low-melting-point PE (melting point 90℃ to 115℃) were dispersed in a mixed solvent of DMF: acetone = 7:3 and stirred until the slurry viscosity was stable to obtain slurry E with a solid content of 25%, wherein the mass ratio of PVDF to low-melting-point PE was 82:18.

[0185] Al2O3 and low-melting-point PE were dispersed in a mixed solvent of NMP:acetone = 7:3 and stirred until the slurry viscosity stabilized to obtain slurry F with a solid content of 40%, wherein the mass ratio of Al2O3 to low-melting-point PE was 95:5.

[0186] Using slurry E on the surface of the positive electrode sheet Figure 6 The electrospinning equipment 60 shown sprays a PVDF and PE mixed fiber layer with a thickness of 10 μm, wherein the average pore size of the fiber layer is 100 nm and the porosity is 50%. Then, the slurry F is sprayed onto the surface of the PVDF+PE fiber layer by the electrospray equipment 70 to form an isolation layer with a thickness of 12 μm.

[0187] c) <Preparation of double-sided coated electrode sheets>

[0188] Repeat steps a and b above on the back of the positive electrode sheet, then vacuum dry at 40°C to remove dispersants such as DMF, and then heat treat at 80°C for 6 hours to complete the crosslinking process, thus obtaining a positive electrode sheet with a double-sided integrated isolation layer. Then cut the positive electrode sheet into sheets with a specification of 74mm×867mm and weld tabs for later use.

[0189] The preparation parameters and test results of each embodiment and comparative example are shown in Tables 1 and 2 below:

[0190] Table 1. Test parameters and corresponding experimental results for Examples 1-18 and each comparative example.

[0191]

[0192] Table 2 Test parameters and corresponding experimental results for Examples 19-21

[0193]

[0194] As can be seen from Examples 1-21 and Comparative Examples 1, 2, and 4, the lithium-ion battery with the isolation layer of this application exhibits a significant decrease in deformation rate after 300 cycles, indicating that the lithium-ion battery of this application has a lower degree of deformation after multiple cycles, and therefore has higher safety.

[0195] As can be seen from Examples 1-21 and Comparative Examples 1-3, the volumetric energy density of the lithium-ion battery with the isolation layer of this application is significantly improved after O2C discharge, indicating that the lithium-ion battery of this application has a very high energy density.

[0196] As can be seen from Examples 1-15, 17-20 and Comparative Examples 1-4, the lithium-ion battery with the isolation layer of this application has improved cycle capacity retention, indicating that the lithium-ion battery of this application not only has excellent resistance to deformation, but also has a long service life.

[0197] The volume percentage of inorganic particles in the separator typically affects its strength; the thickness of the separator typically affects its strength and adhesion performance; porosity typically affects the air permeability of the separator; the fiber diameter of the polymer fibers typically affects the strength of the separator; and the average particle size of the inorganic particles typically affects the adhesion performance of the separator. As can be seen from Examples 1-21, as long as the above conditions are within the scope of this application, resulting in differences in the interfacial adhesion force between different regions of the lithium-ion battery—specifically, making the adhesion force between the separator and the electrode surface in the first region of the lithium-ion battery greater than that in the second region, and making the adhesion force between the separator and the electrode surface in the first sub-region of the first region greater than that in the second sub-region—thereby achieving low deformation in the lithium-ion battery, the objective of this invention can be achieved.

[0198] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An jelly-roll electrode assembly comprising an electrode tab and a separator layer on at least one surface of the electrode tab, the jelly-roll electrode assembly having a first region and a second region, the first region being a flat region of the jelly-roll electrode assembly, the second region being a rolled region of the jelly-roll electrode assembly, a bonding force F1 between the separator layer and the electrode tab surface in the first region being greater than a bonding force F2 between the separator layer and the electrode tab surface in the second region; the bonding force F2 between the separator layer and the electrode tab surface in the second region being 2 N / m to 15 N / m; the first region comprising a first sub-region and a second sub-region, the first sub-region being a tab region of the jelly-roll electrode assembly, the second sub-region being a region within the first region that does not contain a tab, a bonding force F3 between the separator layer and the electrode tab in the second sub-region being greater than a bonding force F4 between the separator layer and the electrode tab in the first sub-region.

2. The jellyroll electrode assembly according to claim 1, wherein a difference between the bonding force F1 between the separator layer and the electrode tab surface in the first region and the bonding force F2 between the separator layer and the electrode tab surface in the second region being 1 N / m to 15 N / m.

3. The wound electrode assembly of claim 2, wherein, a difference between the bonding force F1 between the separator layer and the electrode tab surface in the first region and the bonding force F2 between the separator layer and the electrode tab surface in the second region being 5 N / m to 10 N / m.

4. The jellyroll electrode assembly according to claim 1, wherein the bonding force F1 between the separator layer and the electrode tab surface in the first region being 1 N / m to 30 N / m.

5. The wound electrode assembly of claim 4, wherein, the bonding force F1 between the separator layer and the electrode tab surface in the first region being 10 N / m to 20 N / m.

6. The wound electrode assembly of claim 1, wherein, the separator layer comprising polymer fibers, the polymer fibers comprising a binder, a content of the binder in the polymer fibers in the first region being 5 wt% to 25 wt%, a content of the binder in the polymer fibers in the second region being 2 wt% to 20 wt%.

7. The wound electrode assembly of claim 6, wherein, the polymer fibers further comprising an inorganic filler, a content of the inorganic filler in the polymer fibers being 5 wt% to 10 wt%.

8. The wound electrode assembly of claim 6, wherein, the separator layer further comprising inorganic particles, a volume of the inorganic particles in the separator layer being no more than 40% of a total volume of solid substances in the separator layer.

9. The wound electrode assembly of claim 8, wherein, the inorganic particles comprising a binder, a content of the binder in the inorganic particles in the first region being 4 wt% to 7 wt%, a content of the binder in the inorganic particles in the second region being 3 wt% to 15 wt%.

10. The wound electrode assembly of claim 6, wherein, the polymer fibers comprising at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene ether, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride-hexafluoropropylene, or polyvinylidene fluoride-co-trifluorochloroethylene, or a derivative of the above.

11. The wound electrode assembly of claim 8, wherein, The inorganic substance of the inorganic particles includes at least one of hafnium oxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide, aluminum hydroxide, lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS2 glass, P2S5 glass, lithium oxide, lithium fluoride, lithium hydroxide, lithium carbonate, lithium meta-aluminate, lithium germanium phosphorus sulfur ceramic, or garnet ceramic.

12. The wound electrode assembly of claim 6, wherein, The binder includes at least one of polyvinyl alcohol, polytetrafluoroethylene, styrene butadiene rubber, sodium carboxymethyl cellulose, polyphenyl acrylic acid, polybutyl acrylate, polyacrylonitrile, polyurethane, or acrylonitrile multi-copolymer.

13. The wound electrode assembly of claim 8, wherein, The wound electrode assembly satisfies at least one of the following characteristics: (a) the fiber diameter of the polymer fiber in the separation layer is 10 nm to 5 μm; (b) the thickness of the separation layer is 1 μm to 50 μm; (c) the average particle size of the inorganic particles in the separation layer is 20 nm to 5 μm; (d) the volume of the inorganic particles in the separation layer is 15% to 30% of the total volume of solid matter in the separation layer.

14. An electrochemical device comprising the wound electrode assembly of any one of claims 1-13.

15. An electronic device comprising the electrochemical device of claim 14.

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