Electrochemical device and electronic device

Abstract

The present application provides an electrochemical device and an electronic device. The positive electrode active material in the positive electrode sheet of the electrochemical device has a Dv99 value of 27 to 33 μm, and the negative electrode active material in the negative electrode sheet has a Dv99 value of 23 to 28 μm. The positive electrode current collector in the positive electrode sheet extends integrally to form multiple positive electrode tabs; the negative electrode current collector in the negative electrode sheet extends integrally to form multiple negative electrode tabs. The separator comprises a separator substrate, a first bonding coating, and a second bonding coating, the first bonding coating and the second bonding coating being disposed on either side of the separator substrate, respectively. The first bonding coating comprises a first polymer binder having an average particle size of 0.3 to 3 μm; and the second bonding coating comprises a second polymer binder having an average particle size of 10 to 38 μm. The electrochemical device of the present application exhibits excellent cycling kinetics and high-temperature stability.

Description

Technical Field

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

[0002] Lithium-ion batteries have the characteristics of high specific energy, 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 continuous iterative development of consumer lithium-ion batteries in recent years, the market has higher and higher requirements for their charging speed, and the charging rate has continued to increase. Consumer demand has gradually increased from 1C to 3C, 5C, 6C, 7C and 10C. At a rate of 10C, the full charge time of a lithium-ion battery is less than 15 minutes, which provides great convenience for daily life. However, it is difficult to balance the charging rate and high temperature (temperature ≥ 60°C) stability of super-fast charging (5C≤charging rate≤15C) lithium-ion batteries. Therefore, how to improve the cycle kinetics performance of lithium-ion batteries while taking into account the high temperature stability of lithium-ion batteries has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0003] The purpose of the present application is to provide an electrochemical device to improve the cycle kinetics performance of the electrochemical device while taking into account high-temperature stability, and at the same time provide an electronic device using the electrochemical device.

[0004] It should be noted that in the invention content of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries, and can also be applied to electrochemical devices such as sodium-ion batteries.

[0005] The specific technical solutions are as follows:

[0006] The first aspect of the present application provides an electrochemical device, which includes an electrode assembly, the electrode assembly includes a positive electrode plate, a negative electrode plate and a separator, the positive electrode plate includes a positive electrode active material, the negative electrode plate includes a negative electrode active material, the Dv99 of the positive electrode active material is 27μm to 33μm, and the Dv99 of the negative electrode active material is 23μm to 28μm; the positive electrode plate includes a positive electrode collector, and the positive electrode collector extends as a whole to form a plurality of positive electrode tabs; the negative electrode plate includes a negative electrode collector, and the negative electrode collector extends as a whole to form a plurality of negative electrode tabs; the separator includes a separator substrate, a first bonding coating and a second bonding coating, and the first bonding coating and the second bonding coating are respectively arranged on both sides of the separator substrate; the first bonding coating includes a first polymer binder, and the average particle size of the first polymer binder is 0.3μm to 3μm; the second bonding coating includes a second polymer binder, and the average particle size of the second polymer binder is 10μm to 38μm.

[0007] The present application regulates the Dv99 of the positive electrode active material and the negative electrode active material within the above range, so that the lithium ions have a shorter transmission path and smaller transmission tortuosity within the positive electrode active material and the negative electrode active material during the transmission process, accelerates the conduction of lithium ions to reduce the concentration polarization of the electrochemical device, and thus makes the electrochemical device have good cycle kinetic performance. The present application provides a positive electrode current collector that extends integrally to form multiple positive electrode tabs, and a negative electrode current collector that extends integrally to form multiple negative electrode tabs, so that the electrochemical device has a multi-tab structure. In this way, there are multiple current channels on the positive electrode plate and the negative electrode plate, the internal resistance of the electrochemical device is reduced, and the voltage polarization of the electrochemical device is small during super-fast charging, which can reduce the charging temperature rise of the electrochemical device and shorten the charging time of the electrochemical device, thereby making the electrochemical device have higher kinetic performance. However, the high kinetic design makes it easy for side reactions to occur between the positive electrode active material, the negative electrode active material and the electrolyte, especially at high temperatures, violent side reactions occur to produce a large amount of gas, which makes the high temperature stability of the electrochemical device poor. The present application sets a first bonding coating and a second bonding coating on both sides of the isolation membrane, and the average particle size of the first polymer binder in the first bonding coating and the average particle size of the second polymer binder in the second bonding coating are within the above-mentioned range of the present application, which is beneficial to strengthening the interface between the isolation membrane and the positive electrode sheet and the negative electrode sheet, inhibiting gas production under high temperature conditions, and reducing the probability of the electrochemical device expanding due to excessive gas production, so as to improve the cycle performance and high-temperature stability. On one side of the second bonding coating of the isolation membrane, an electrolyte flow channel can be generated and the electrolyte can be stored, meeting the requirements of the electrochemical device for high electrolyte retention (such as 1.5g / Ah to 2.4g / Ah) and high transmission and infiltration in the super-fast charging state, thereby ensuring the rate and cycle kinetics performance of the electrochemical device. The present application combines the particle size control of the positive active material and the negative active material, the multi-electrode structure design, and the isolation membrane structure design, and makes the above three have good synergistic effects, so as to improve the cycle kinetics performance of the electrochemical device and take into account the high-temperature stability.

[0008] In some embodiments of the present application, the first bonding coating is disposed on the side of the separator substrate close to the negative electrode plate, and the second bonding coating is disposed on the side of the separator substrate close to the positive electrode plate. For most electrochemical devices, fast charging is primarily required for energy replenishment, but there is no need for fast discharge, that is, the charging rate is much greater than the discharge rate. The charging process of an electrochemical device mainly involves the insertion of lithium ions into the negative electrode. Therefore, disposing the first bonding coating with smaller separator particles close to the negative electrode plate can shorten the lithium ion transmission path during the charging process and achieve faster charging speed.

[0009] In some embodiments of the present application, an N1 layer of positive electrode tabs is provided between two adjacent positive electrode tabs, and an N2 layer of negative electrode tabs is provided between two adjacent negative electrode tabs, and N1 and N2 are each independently selected from 0, 1, 2, or 3. By regulating N1 and N2 within the above ranges, it is possible to provide a sufficient number of positive electrode tabs and negative electrode tabs on the positive electrode tabs and negative electrode tabs in the electrochemical device, thereby providing multiple current channels on the positive electrode tabs and negative electrode tabs, reducing the internal resistance of the electrochemical device, and reducing the charging temperature rise and charging time of the electrochemical device during super-fast charging, thereby improving the cycle kinetics performance of the electrochemical device while maintaining good high-temperature stability. It can be understood that adjusting N1 and N2 to 0 can provide more current channels on the positive and negative electrodes, further reduce the internal resistance of the electrochemical device, further reduce the charging temperature rise of the electrochemical device, and further shorten the charging time, thereby further improving the cycle kinetics of the electrochemical device while taking into account high-temperature stability. However, this will reduce the energy density of the electrochemical device to a certain extent; adjusting N1 and N2 to 1, 2, or 3 will reduce the number of tabs and increase the internal resistance to a certain extent, but can increase the energy density of the electrochemical device.

[0010] In some embodiments of the present application, the Dv99 of the positive electrode active material is 28 μm to 31 μm, and / or the Dv99 of the negative electrode active material is 24 μm to 26 μm. By regulating the Dv99 of the positive electrode active material and / or the negative electrode active material within the above range, the Dv99 range of the positive electrode active material and / or the negative electrode active material is more optimal, which is conducive to further improving the cycle kinetics performance and high temperature stability of the electrochemical device.

[0011] In some embodiments of the present application, the Dv50 of the positive electrode active material is 10 μm to 15 μm, and / or the Dv50 of the negative electrode active material is 7 μm to 12 μm. Regulating the Dv50 of the positive electrode active material and / or the negative electrode active material within the above range is beneficial for achieving a high energy density of the electrochemical device while having good cycle kinetics and high temperature stability.

[0012] In some embodiments of the present application, the Dv50 of the positive electrode active material is 11 μm to 13 μm, and / or the Dv50 of the negative electrode active material is 8 μm to 11 μm. By regulating the Dv50 of the positive electrode active material and / or the negative electrode active material within the above range, the Dv50 range of the positive electrode active material and / or the negative electrode active material is more optimal, which is conducive to further enabling the electrochemical device to have a higher energy density on the basis of having good cycle kinetics and high temperature stability.

[0013] In some embodiments of the present application, the average particle size of the first polymer binder is 0.6 μm to 1.6 μm, and / or the average particle size of the second polymer binder is 20 μm to 30 μm. Regulating the average particle size of the first polymer binder within the above range is beneficial to further improving the high-temperature stability of the electrochemical device while taking into account the cycle kinetics performance, and having a higher energy density. Regulating the average particle size of the second polymer binder within the above range is beneficial to further improving the cycle kinetics performance of the electrochemical device while taking into account the high-temperature stability of the electrochemical device, and also allowing the electrochemical device to have a higher energy density.

[0014] In some embodiments of the present application, the thickness of the first bonding coating layer is 0.2 μm to 4 μm, and the thickness of the second bonding coating layer is 5 μm to 20 μm. The first bonding coating layer has a smaller particle size and stronger bonding strength. Ensuring its thickness is between 0.2 μm and 4 μm can maximize energy density while ensuring bonding strength, while shortening the lithium ion transmission path in the active material layer corresponding to the first bonding coating layer. The second bonding coating layer has a larger particle size, which can form a channel for electrolyte circulation. Setting it between 5 μm and 20 μm can improve energy density while ensuring electrolyte flow and wettability.

[0015] In some embodiments of the present application, the single-sided coating weight of the first bonding coating is 0.0001 mg / mm 2 to 0.001 mg / mm 2 The single-sided coating weight of the second bonding coating is 0.0004 mg / mm 2 to 0.002 mg / mm 2 By regulating the single-sided coating weight of the first bonding coating within the aforementioned range, the high bonding properties of the first bonding coating can be fully utilized, thereby better bonding the electrode and the separator, and ensuring the high-temperature stability of the electrochemical device. By regulating the single-sided coating weight of the second bonding coating within the aforementioned range, the electrolyte flow channel between the electrode and the separator can be fully realized, thereby improving the cycle dynamics performance of the electrochemical device.

[0016] In some embodiments of the present application, the coverage of the first polymer binder per unit area in the first bonding coating layer is 40% to 60%. Controlling the coverage of the first polymer binder per unit area in the first bonding coating layer within this range can fully utilize the high bonding properties of the first bonding coating layer, facilitating faster lithium ion transmission when the separator and the electrode are bonded, thereby further improving the cycling kinetics of the electrochemical device.

[0017] In some embodiments of the present application, the first polymer binder includes a core-shell structure first polymer binder or a non-core-shell structure first polymer binder, the core of the core-shell structure first polymer binder includes at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid or maleic acid, the shell of the core-shell structure first polymer binder includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene, chloromethyl ethyl acrylate, chlorostyrene, fluorostyrene, methylstyrene, acrylonitrile or methacrylonitrile; the non-core-shell structure first polymer binder includes at least one of acrylic acid, methyl acrylate, butyl acrylate, butadiene, styrene, acrylonitrile, ethylene, fluorostyrene, chlorostyrene or propylene. The above-mentioned first polymer binder is applied to the first bonding coating layer, which can make the first bonding coating layer have high bonding force.

[0018] In some embodiments of the present application, the coverage of the second polymer binder per unit area in the second bonding coating layer is 40% to 60%. By regulating the coverage of the second polymer binder per unit area in the second bonding coating layer within the above range, the separator and the electrode have strong adhesion, and the electrochemical device has a higher energy density. This enables the electrochemical device to have a lower production cost and a higher energy density while taking into account both cycle dynamics performance and high-temperature stability.

[0019] In some embodiments of the present application, the polymerizable monomer of the second polymer binder includes at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, allyl chloride, acrylic acid, methyl acrylate, butyl acrylate, chlorostyrene, fluorostyrene, ethyl acrylate, ethyl methacrylate, methyl methacrylate, butyl methacrylate, ethyl chloromethacrylate, styrene, butadiene, or acrylonitrile. The use of the aforementioned second polymer binder can provide a large gap between the second bonding coating layer and the positive and negative electrode sheets.

[0020] In some embodiments of the present application, the second polymer binder includes a core-shell structure second polymer binder or a non-core-shell structure second polymer binder, the shell of the core-shell structure second polymer binder includes at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, styrene, butadiene, acrylonitrile, acrylic acid, methyl acrylate, or butyl acrylate, the core of the core-shell structure second polymer binder includes at least one of ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, or ethyl chloromethylacrylate; the non-core-shell structure second polymer binder includes at least one of acrylic acid, methyl acrylate, butyl acrylate, butadiene, styrene, acrylonitrile, ethylene, propylene, chlorostyrene, fluorostyrene, vinylidene chloride, vinylidene fluoride, hexafluoropropylene, vinyl chloride, or allyl chloride. The selection of the above-mentioned second polymer binder can provide a large gap between the second bonding coating and the positive electrode sheet or the negative electrode sheet.

[0021] In some embodiments of the present application, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, or lithium titanate. The above-mentioned positive electrode active materials have high surface activity and can enable the electrochemical device to have good cycle kinetics while maintaining high temperature stability.

[0022] In some embodiments of the present application, the positive electrode active material includes a non-metallic element, and the non-metallic element includes at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur. Including the above-mentioned non-metallic elements in the positive electrode active material can further improve the stability of the positive electrode active material. The above-mentioned non-metallic elements can be added to the positive electrode active material by bulk doping or surface coating using a single substance or compound containing the above-mentioned non-metallic elements.

[0023] In some embodiments of the present application, the negative electrode active material includes at least one of a carbon-based material, a silicon-based material, or a tin-based material. The carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, or mesocarbon microbeads. The silicon-based material includes at least one of a silicon material, a silicon-carbon material, or a silicon-oxygen material. The tin-based material includes at least one of elemental tin, a tin alloy, or a tin oxide. The above-mentioned negative electrode active materials have high surface activity and can enable the electrochemical device to have good cycle kinetics while maintaining high temperature stability.

[0024] In some embodiments of the present application, the carbon-based material is tested by Raman with a peak intensity ratio of d peak to g peak of d / I g Satisfy: 0.1≤I d / I g ≤1. Will satisfy the above Id / I g The application of high-value carbon-based materials in electrochemical devices is beneficial to further improve the cycle kinetics performance of electrochemical devices on the basis of good high-temperature stability.

[0025] In a second aspect of the present application, an electronic device is provided, which includes the electrochemical device according to any one of the aforementioned embodiments. Therefore, the electronic device has good performance.

[0026] Beneficial effects of this application:

[0027] The present application provides an electrochemical device and an electronic device. The electrochemical device achieves good synergy between the positive and negative active materials, the multi-electrode structure, and the separator by regulating the Dv99 of the positive and negative active materials to be within the range of the present application, providing a multi-electrode structure, and providing a first bonding coating and a second bonding coating on both sides of the separator substrate, respectively. Furthermore, the average particle size range of the first polymer binder in the first bonding coating and the second polymer binder in the second bonding coating is limited. This allows for a short transmission path for lithium ions within the positive and negative active materials, multiple current channels on the positive and negative electrode sheets, and wide electrolyte flow channels and strong interfacial adhesion between the separator and the positive or negative electrode sheets, thereby improving the cycle kinetics of the electrochemical device while also taking into account high-temperature stability. The electronic device of the present application has good performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0029] Figure 1 This is a schematic structural diagram of an electrode assembly according to an embodiment of the present application;

[0030] Figure 2 This is a schematic structural diagram of an electrode assembly according to another embodiment of the present application;

[0031] Figure 3 This is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present application;

[0032] Figure 4 This is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present application;

[0033] Figure 5 A schematic diagram of the positional relationship between the separator, the positive electrode sheet, and the negative electrode sheet according to one embodiment of the present application;

[0034] Figure 6A schematic diagram of the positional relationship between the separator, the positive electrode sheet, and the negative electrode sheet according to another embodiment of the present application;

[0035] Figure 7 This is a schematic diagram of the cross-sectional structure of an isolation membrane according to an embodiment of the present application along its thickness direction;

[0036] Figure 8 This is a schematic diagram of the cross-sectional structure of an isolation membrane according to another embodiment of the present application along its thickness direction;

[0037] Figure 9 This is a schematic diagram of the cross-sectional structure of an isolation membrane according to another embodiment of the present application along its thickness direction;

[0038] Figure 10 This is the Raman spectrum of Example 3-3. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples. It is apparent that the described examples are only a portion of the embodiments of this application, rather than all of them. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0040] The first aspect of the present application provides an electrochemical device, which includes an electrode assembly, the electrode assembly includes a positive electrode plate, a negative electrode plate and a separator, the positive electrode plate includes a positive electrode active material, the negative electrode plate includes a negative electrode active material, the Dv99 of the positive electrode active material is 27μm to 33μm, and the Dv99 of the negative electrode active material is 23μm to 28μm; the positive electrode plate includes a positive electrode collector, and the positive electrode collector extends as a whole to form a plurality of positive electrode tabs; the negative electrode plate includes a negative electrode collector, and the negative electrode collector extends as a whole to form a plurality of negative electrode tabs; the separator includes a separator substrate, a first bonding coating and a second bonding coating, and the first bonding coating and the second bonding coating are respectively arranged on both sides of the separator substrate; the first bonding coating includes a first polymer binder, and the average particle size of the first polymer binder is 0.3μm to 3μm; the second bonding coating includes a second polymer binder, and the average particle size of the second polymer binder is 10μm to 38μm.

[0041] For example, the Dv99 of the positive electrode active material is 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm or any value between any two of the above numerical ranges. The Dv99 of the positive electrode active material is less than 27μm. The Dv99 of the positive electrode active material is too small, indicating that the volume particle size of the positive electrode active material particles is too small. When preparing the positive electrode slurry, the positive electrode active material particles are prone to agglomeration. In this way, the probability of the positive electrode active material being uniformly dispersed in the positive electrode slurry is small, and the positive electrode active material particles in the formed positive electrode active material layer are unevenly distributed, which will affect the processing stability of the positive electrode sheet and cause uneven coating problems during the coating of the positive electrode slurry. In addition, the specific surface area of ​​the positive electrode active material particles will be too large, resulting in poor contact between the positive electrode active material particles and the electrolyte. As the number of contact interfaces increases, side reactions will intensify, especially in the high-kinetic electrolyte system of super-fast charging, the side reactions will be very violent, accelerating the consumption of electrolyte and the generation of side reaction products, and worsening the cycle kinetics and high-temperature stability of the electrochemical device; the Dv99 of the positive electrode active material is greater than 33μm, the Dv99 of the positive electrode active material is too large, the transmission path of lithium ions inside the positive electrode active material particles is too long, and the tortuosity of the transmission inside the positive electrode sheet is too large, which will lead to excessive concentration polarization inside the electrochemical device, thereby increasing the internal resistance of the electrochemical device and reducing the cycle kinetics of the electrochemical device.

[0042] For example, the Dv99 of the negative electrode active material is 23μm, 24μm, 25μm, 26μm, 27μm, 28μm or any value between any two of the above numerical ranges. The Dv99 of the negative electrode active material is less than 23μm. The Dv99 of the negative electrode active material is too small, indicating that the volume particle size of the negative electrode active material particles is too small. When preparing the negative electrode slurry, the particles of the negative electrode active material are prone to agglomeration. In this way, the probability of the negative electrode active material being uniformly dispersed in the negative electrode slurry is small, and the negative electrode active material particles in the formed negative electrode active material layer are unevenly distributed, which will affect the processing stability of the negative electrode sheet and cause uneven coating problems during the coating of the negative electrode slurry. In addition, the specific surface area of ​​the negative electrode active material particles will be too large, resulting in poor contact between the negative electrode active material particles and the electrolyte. As the number of contact interfaces increases, side reactions will intensify, especially in the high-kinetic electrolyte system of super-fast charging, the side reactions will be very violent, accelerating the consumption of electrolyte and the generation of side reaction products, and worsening the cycle kinetics and high-temperature stability of the electrochemical device; the Dv99 of the negative electrode active material is greater than 28μm, the Dv99 of the negative electrode active material is too large, the transmission path of lithium ions inside the negative electrode active material particles is too long, and the tortuosity of the transmission inside the negative electrode sheet is too large, which will lead to excessive concentration polarization inside the electrochemical device, thereby increasing the internal resistance of the electrochemical device and reducing the cycle kinetics of the electrochemical device.

[0043] In this application, for ease of understanding, the positive electrode sheet is defined as having its own length direction as X, its own width direction as Y, and its own thickness direction as Z in the unfolded state. It can be understood that the negative electrode sheet and the separator have the same length direction, width direction, and thickness direction as the positive electrode sheet in the unfolded state. After the positive electrode sheet, the separator, and the negative electrode sheet are wound to form an electrode assembly with a wound structure, the winding direction of the electrode assembly is W. Figure 1 and Figure 2 As shown, the electrode assembly 001 includes a positive electrode sheet 10, a negative electrode sheet 20 and a separator 30, and the separator 30 is arranged between the positive electrode sheet 10 and the negative electrode sheet 20. The positive electrode sheet 10 includes a positive electrode current collector 11, as shown in FIG. Figure 3 As shown, the positive electrode current collector 11 includes a positive electrode tab region 111 and a positive electrode main body region 112. The positive electrode current collector 11 extends integrally to form a plurality of positive electrode tabs 12. The region where the positive electrode tabs 12 are provided in the positive electrode current collector 11 is the positive electrode tab region 111, and the region other than the positive electrode tab region 111 in the positive electrode current collector 11 is the positive electrode main body region 112. The negative electrode sheet 20 includes a negative electrode current collector 21, as shown in FIG. Figure 4 As shown, the negative electrode current collector 21 includes a negative electrode tab region 211 and a negative electrode main body region 212. The negative electrode current collector 21 extends integrally to form a plurality of negative electrode tabs 22. The region in the negative electrode current collector 21 where the negative electrode tabs 22 are provided is the negative electrode tab region 211, and the region in the negative electrode current collector 21 other than the negative electrode tab region 211 is the negative electrode main body region 212. In the present application, the above-mentioned "integrated extension" refers to the integral molding of the current collector and the tabs. For example, a plurality of tabs can be cut out on the current collector by die-cutting or laser, which is different from the solution of connecting the tabs to the current collector by welding or other means. It should be noted that, Figures 1 to 4 The number, shape and size of the positive electrode tabs and negative electrode tabs are for illustrative purposes only and are not intended to limit this application. In this application, the above-mentioned "plurality" refers to two or more. In one embodiment of the present application, "plurality" refers to at least 2, and there is no special requirement for the upper limit of the number of tabs, which can be adjusted according to factors such as the capacity and size of the electrode assembly. Exemplarily, "plurality" can be 2, 3, 4, 5, 6, 7, 20 or 50. In a preferred embodiment, one tab is provided for each layer of positive electrode sheet and / or one tab is provided for each layer of negative electrode sheet.

[0044] like Figure 5 and Figure 6 As shown, the separator 30 includes a separator substrate 31, a first bonding coating 32 and a second bonding coating 33. The first bonding coating 32 and the second bonding coating 33 are respectively arranged on both sides of the separator substrate 31, and the separator substrate 31 is located between the first bonding coating 32 and the second bonding coating 33. Among them, the first bonding coating 32 can be close to the positive electrode sheet 10 side, or close to the negative electrode sheet 20 side. Figure 5 As shown, the first bonding coating 32 is provided on the side of the separator substrate 31 close to the negative electrode sheet 20, and the second bonding coating 33 is provided on the side of the separator substrate 31 close to the positive electrode sheet 10. Figure 6 As shown, the first bonding coating 32 is disposed on the side of the separator substrate 31 close to the positive electrode sheet 10 , and the second bonding coating 33 is disposed on the side of the separator substrate 31 close to the negative electrode sheet 20 .

[0045] For example, the average particle size of the first polymer binder is 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or any numerical value between any two numerical ranges mentioned above. The average particle size of the first polymer binder is less than 0.3 μm, and the average particle size of the first polymer binder is too small. When preparing the first bonding coat slurry, each particle of the first polymer binder is easily agglomerated. In this way, the probability that the first polymer binder is uniformly dispersed in the first bonding coat slurry is extremely small, and the distribution of the first polymer binder in the first bonding coat formed is uneven, which will affect the cohesive force of the first bonding coat. The average particle size of the first polymer binder is greater than 3 μm, and the average particle size of the first polymer binder is too large, which is unfavorable for cycle performance, and the average particle size of the first polymer binder is too large to increase the thickness of the first bonding coat, thereby increasing the volume of the electrochemical device and causing its energy density to be lost.

[0046] For example, the average particle size of the second polymer binder is 10 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 38 μm, or any value between any two of the above numerical ranges. The average particle size of the second polymer binder is less than 10 μm. If the average particle size of the second polymer binder is too small, the gap between the separator and the positive electrode sheet or the negative electrode sheet will be too small, and the electrolyte transmission channel will be too narrow, which will affect the electrolyte transmission speed and thus affect the cycle dynamics performance of the electrochemical device. The average particle size of the second polymer binder is greater than 38 μm. If the average particle size of the second polymer binder is too large, the thickness of the second bonding coating will increase, thereby increasing the volume of the electrochemical device and causing a loss in its energy density.

[0047] In general, the present application regulates the Dv99 of the positive electrode active material and the negative electrode active material within the above range, so that the lithium ions have a shorter transmission path and smaller transmission tortuosity within the positive electrode active material and the negative electrode active material during the transmission process, accelerates the conduction of lithium ions to reduce the concentration polarization of the electrochemical device, and thus makes the electrochemical device have good cycle kinetic performance. The present application provides a positive electrode current collector that extends integrally to form multiple positive electrode tabs, and a negative electrode current collector that extends integrally to form multiple negative electrode tabs, so that the electrochemical device has a multi-tab structure. In this way, there are multiple current channels on the positive electrode plate and the negative electrode plate, the internal resistance of the electrochemical device is reduced, and the voltage polarization of the electrochemical device is small during super-fast charging, which can reduce the charging temperature rise of the electrochemical device and shorten the charging time of the electrochemical device, thereby making the electrochemical device have higher kinetic performance. However, the high kinetic design makes it easy for side reactions to occur between the positive electrode active material, the negative electrode active material and the electrolyte, especially at high temperatures, violent side reactions occur to produce a large amount of gas, which makes the high temperature stability of the electrochemical device poor. The present application sets a first bonding coating and a second bonding coating on both sides of the isolation membrane, and the average particle size of the first polymer binder in the first bonding coating and the average particle size of the second polymer binder in the second bonding coating are within the above-mentioned range of the present application, which is beneficial to strengthening the interface between the isolation membrane and the positive electrode sheet and the negative electrode sheet, inhibiting gas production under high temperature conditions, and reducing the probability of the electrochemical device expanding due to excessive gas production, so as to improve the cycle performance and high-temperature stability. On one side of the second bonding coating of the isolation membrane, an electrolyte flow channel can be generated and the electrolyte can be stored, meeting the requirements of the electrochemical device for high electrolyte retention (such as 1.5g / Ah to 2.4g / Ah) and high transmission and infiltration in the super-fast charging state, thereby ensuring the rate and cycle kinetics performance of the electrochemical device. The present application combines the particle size control of the positive active material and the negative active material, the multi-electrode structure design, and the isolation membrane structure design, and makes the above three have good synergistic effects, so as to improve the cycle kinetics performance of the electrochemical device and take into account the high-temperature stability.

[0048] In this application, Dv99 means the particle size that reaches 99% of the cumulative volume from the small particle size side in the volume-based particle size distribution. The above-mentioned "particles" in this application can be particles of positive electrode active materials or particles of negative electrode active materials. This application does not particularly limit the method of regulating the Dv99 of positive electrode active materials and negative electrode active materials, as long as the purpose of this application can be achieved. For example, it can be achieved by directly purchasing positive electrode active materials and negative electrode active materials whose Dv99 is within the scope of this application, or by crushing, grinding or ball milling.

[0049] The electrochemical device in the present application can be used under super-fast charging conditions, specifically, can be used at a charge rate of 5C to 15C. For example, the charge rate of the electrochemical device is 5C, 8C, 10C, 12C, 15C, or a range consisting of any two of these values.

[0050] In some embodiments of the present application, the first bonding coating is disposed on the side of the separator substrate close to the negative electrode sheet, and the second bonding coating is disposed on the side of the separator substrate close to the positive electrode sheet. Figure 5 As shown, the first bonding coating 32 is provided on the side of the separator substrate 31 close to the negative electrode 20, and the second bonding coating 33 is provided on the side of the separator substrate 31 close to the positive electrode 10. For most electrochemical devices, fast charging is mainly required for energy replenishment, but there is no need for fast discharge, that is, the charging rate is much greater than the discharge rate. The charging process of the electrochemical device mainly involves the insertion of lithium ions into the negative electrode. Therefore, the first bonding coating with smaller separator particles is provided on the side close to the negative electrode. This can shorten the lithium ion transmission path during the charging process and achieve faster charging speed. It is also beneficial for the positive electrode or negative electrode to have excellent bonding properties with the separator, so that the electrochemical device has good high-temperature stability.

[0051] In some embodiments of the present application, an N1 layer of positive electrode sheet is provided between two adjacent positive electrode tabs, and an N2 layer of negative electrode sheet is provided between two adjacent negative electrode tabs, and N1 and N2 are each independently selected from 0, 1, 2 or 3. Figure 1 As shown, in the wound electrode assembly, from top to bottom, no positive electrode sheet 10 is set between two adjacent positive electrode tabs 12, and no negative electrode sheet 20 is set between two adjacent negative electrode tabs 22. Figure 2As shown, in the wound electrode assembly, viewed from top to bottom in the figure, one layer of positive electrode sheet 10 and two layers of positive electrode sheet 10 are respectively disposed between two adjacent positive electrode tabs 12, and zero layer of negative electrode sheet 20 and three layers of negative electrode sheet 20 are respectively disposed between two adjacent negative electrode tabs 22. By regulating N1 and N2 within the above ranges, it is possible to provide a sufficient number of positive electrode tabs and negative electrode tabs on the positive and negative electrode sheets of the electrochemical device, thereby providing multiple current channels on the positive and negative electrode sheets, reducing the internal resistance of the electrochemical device, lowering the charging temperature rise of the electrochemical device during super-fast charging, and shortening the charging time, thereby improving the cycling kinetics of the electrochemical device while maintaining good high-temperature stability. It can be understood that adjusting N1 and N2 to 0 can provide more current channels on the positive and negative electrodes, further reduce the internal resistance of the electrochemical device, further reduce the charging temperature rise of the electrochemical device, and further shorten the charging time, thereby further improving the cycle kinetics of the electrochemical device while taking into account high-temperature stability. However, this will reduce the energy density of the electrochemical device to a certain extent; adjusting N1 and N2 to 1, 2, or 3 will reduce the number of tabs and increase the internal resistance to a certain extent, but can increase the energy density of the electrochemical device.

[0052] In some embodiments of the present application, an N1 layer of positive electrode sheet is provided between two adjacent positive electrode tabs, and an N2 layer of negative electrode sheet is provided between two adjacent negative electrode tabs, and N1 and N2 are each independently selected from 0. Figure 1 As shown, in the wound electrode assembly, from top to bottom in the figure, there is a positive electrode sheet 10 layer provided between each adjacent positive electrode tab 12, and a negative electrode sheet 20 layer provided between each adjacent negative electrode tab 22. By adjusting N1 and N2 to 0, more positive electrode sheets in the electrochemical device can be provided with positive electrode tabs, and more negative electrode sheets can be provided with negative electrode tabs, thereby providing more current channels on the positive and negative electrode sheets, further reducing the internal resistance of the electrochemical device, further reducing the charging temperature rise of the electrochemical device during super-fast charging, and further shortening the charging time, thereby further improving the cycle kinetics performance of the electrochemical device while maintaining good high-temperature stability, but at the same time reducing the energy density to a certain extent. In the present application, N1 layers of positive electrode sheets are arranged between two adjacent positive electrode tabs, which means that the number of layers of positive electrode sheets with double-sided positive electrode active material layers between two adjacent positive electrode tabs is N1 layers; N2 layers of negative electrode sheets are arranged between two adjacent negative electrode tabs, which means that the number of layers of negative electrode sheets with double-sided negative electrode active material layers between two adjacent negative electrode tabs is N2 layers.

[0053] In some embodiments of the present application, the Dv99 of the positive electrode active material is 28 μm to 31 μm. For example, the Dv99 of the positive electrode active material is 28 μm, 29 μm, 30 μm, 31 μm, or any value between any two of the above ranges. By regulating the Dv99 of the positive electrode active material within the above range, the Dv99 range of the positive electrode active material is more optimal, which is conducive to further improving the cycle kinetics and high temperature stability of the electrochemical device.

[0054] In some embodiments of the present application, the Dv99 of the negative electrode active material is 24 μm to 26 μm. For example, the Dv99 of the negative electrode active material is 24 μm, 25 μm, 26 μm, or any value between any two of the above ranges. By regulating the Dv99 of the negative electrode active material within the above range, the Dv99 range of the negative electrode active material is more optimal, which is conducive to further improving the cycling kinetics and high-temperature stability of the electrochemical device.

[0055] In some embodiments of the present application, the Dv99 of the positive electrode active material is 28μm to 31μm, and the Dv99 of the negative electrode active material is 24μm to 26μm. For example, the Dv99 of the positive electrode active material is 28μm, 29μm, 30μm, 31μm, or any value between any two of the above numerical ranges. The Dv99 of the negative electrode active material is 24μm, 25μm, 26μm, or any value between any two of the above numerical ranges. By regulating the Dv99 of the positive electrode active material and the negative electrode active material within the above range, the Dv99 range of the positive electrode active material and the negative electrode active material is more optimal, which is conducive to further improving the cycle kinetics and high temperature stability of the electrochemical device.

[0056] In some embodiments of the present application, the Dv50 of the positive electrode active material is 10 μm to 15 μm, and / or the Dv50 of the negative electrode active material is 7 μm to 12 μm. For example, the Dv50 of the positive electrode active material is 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any value between any two of the above numerical ranges. The Dv50 of the negative electrode active material is 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any value between any two of the above numerical ranges. By regulating the Dv50 of the positive electrode active material and / or the negative electrode active material within the above range, the risk of agglomeration of the positive electrode active material in the positive electrode slurry is low, and / or the risk of agglomeration of the negative electrode active material in the negative electrode slurry is low, and the thickness of the positive electrode active material layer and / or the negative electrode active material layer can be regulated within a suitable range on the basis of enabling the positive electrode active material and / or the negative electrode active material to play their own role, so as to reduce the risk of energy density loss due to increased thickness, thereby facilitating the electrochemical device to have a higher energy density on the basis of good cycle kinetics and high temperature stability.

[0057] In some embodiments of the present application, the Dv50 of the positive electrode active material is 11 μm to 13 μm, and / or the Dv50 of the negative electrode active material is 8 μm to 11 μm. For example, the Dv50 of the positive electrode active material is 11 μm, 12 μm, 13 μm, or any value between any two of the above numerical ranges. The Dv50 of the negative electrode active material is 8 μm, 9 μm, 10 μm, 11 μm, or any value between any two of the above numerical ranges. By regulating the Dv50 of the positive electrode active material and / or the negative electrode active material within the above range, the risk of agglomeration of the positive electrode active material in the positive electrode slurry is low, and / or the risk of agglomeration of the negative electrode active material in the negative electrode slurry is low, and the thickness of the positive electrode active material layer and / or the negative electrode active material layer can be regulated within a suitable range on the basis of enabling the positive electrode active material and / or the negative electrode active material to play their own role, so as to further reduce the risk of energy density loss due to increased thickness, thereby facilitating the electrochemical device to have a higher energy density on the basis of good cycle kinetics and high temperature stability.

[0058] In this application, Dv50 means the particle size at which 50% of the volume is accumulated, starting from the small particle size side, in the volume-based particle size distribution. The above-mentioned "particles" in this application can be particles of positive electrode active materials or particles of negative electrode active materials. This application does not impose any particular restrictions on the method of regulating the Dv50 of positive electrode active materials and negative electrode active materials, as long as the purpose of this application can be achieved. For example, this can be achieved by directly purchasing positive electrode active materials and negative electrode active materials whose Dv50 is within the range of this application, or by crushing, grinding or ball milling.

[0059] In some embodiments of the present application, the average particle size of the first polymer binder is 0.6 μm to 1.6 μm. In other embodiments of the present application, the average particle size of the second polymer binder is 20 μm to 30 μm. In other embodiments of the present application, the average particle size of the first polymer binder is 0.6 μm to 1.6 μm, and the average particle size of the second polymer binder is 20 μm to 30 μm. For example, the average particle size of the first polymer binder is 0.6 μm, 0.8 μm, 1.0 μm, 1.6 μm, or any value between any two of the above numerical ranges. For example, the average particle size of the second polymer binder is 20 μm, 22 μm, 25 μm, 27 μm, 30 μm, or any value between any two of the above numerical ranges. Regulating the average particle size of the first polymer binder within the above range facilitates uniform distribution of the first polymer binder in the first bonding coat, and provides suitable spacing between the particles of the first polymer binder, thereby providing the first bonding coat with stronger bonding strength. Furthermore, it is also advantageous to regulate the thickness of the first bonding coat within a suitable range, thereby further improving the high-temperature stability of the electrochemical device while taking into account the cycle kinetics performance, and achieving a higher energy density. Regulating the average particle size of the second polymer binder within the above range provides a suitable spacing between the separator and the positive or negative electrode sheet, thereby facilitating the transmission of the electrolyte, and further regulated the thickness of the second bonding coat within a suitable range, thereby further improving the cycle kinetics performance of the electrochemical device while taking into account the high-temperature stability of the electrochemical device, and achieving a higher energy density.

[0060] In some embodiments of the present application, Figures 5 to 9 As shown, the thickness H1 of the first bonding coating 32 is 0.2μm to 4μm. For example, the thickness H1 of the first bonding coating is 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm or any value between any two of the above numerical ranges. The particle size of the first polymer binder in the first bonding coating is small, the bonding force of the first bonding coating is strong, and the thickness of the first bonding coating is regulated within the above range. The first bonding coating has a suitable thickness, which can reduce the risk of energy density loss caused by the increase in volume of the electrochemical device due to excessive thickness while ensuring the bonding force of the first bonding coating, thereby improving the energy density of the electrochemical device and shortening the transmission path of lithium ions in the active material layer corresponding to the first bonding coating. As a result, the electrochemical device can be improved while taking into account both cycle dynamics performance and high temperature stability.

[0061] In some embodiments of the present application, Figures 5 to 9As shown, the thickness H2 of the second bonding coating 33 is 5μm to 20μm. For example, the thickness H2 of the second bonding coating is 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm or any value between any two of the above numerical ranges. The particle size of the second polymer binder in the second bonding coating is large, which can form a channel for the circulation of the electrolyte. The thickness of the second bonding coating is regulated within the above range. The second bonding coating has a suitable thickness, which can reduce the risk of energy density loss caused by the increase in the volume of the electrochemical device due to excessive thickness when the electrolyte has good flow wettability in the pole piece and the separator. In this way, the electrochemical device can improve the energy density of the electrochemical device while taking into account the cycle dynamics performance and high temperature stability.

[0062] In some embodiments of the present application, the single-sided coating weight Cw1 of the first bonding coating is 0.0001 mg / mm 2 to 0.001 mg / mm 2 For example, the single-sided coating weight of the first bonding coating is 0.0001 mg / mm 2 , 0.0002mg / mm 2 , 0.0003mg / mm 2 , 0.0004mg / mm 2 , 0.0005mg / mm 2 , 0.0006mg / mm 2 , 0.0007mg / mm 2 , 0.0008mg / mm 2 , 0.0009mg / mm 2 , 0.001mg / mm 2 Or any value between any two of the above numerical ranges. By regulating the single-sided coating weight of the first bonding coating within the above range, the first bonding coating can exert its high bonding strength to better bond the electrode and the separator. It can also reduce the risk of energy density loss caused by the increase in the volume of the electrochemical device due to excessive single-sided coating weight. In this way, the electrochemical device can have a higher energy density while having good cycle dynamics and high-temperature stability.

[0063] In some embodiments of the present application, the single-sided coating weight Cw2 of the second bonding coating is 0.0004 mg / mm 2 to 0.002 mg / mm 2 For example, the coating weight of the second adhesive coating layer on one side is 0.0004 mg / mm 2 , 0.0008mg / mm 2 , 0.0012mg / mm 2, 0.0016mg / mm 2 , 0.002mg / mm 2 Or any value between any two of the above numerical ranges. By regulating the single-sided coating weight of the second bonding coating within the above range, the electrolyte flow channel between the electrode and the separator can be fully realized, thereby improving the cycle kinetics performance of the electrochemical device. It can also reduce the risk of energy density loss caused by the increase in the volume of the electrochemical device due to excessive single-sided coating weight. In this way, the electrochemical device can have a higher energy density while taking into account both cycle kinetics performance and high-temperature stability.

[0064] In some embodiments of the present application, the coverage rate Cr1 of the first polymer binder per unit area in the first bonding coating is 40% to 60%. For example, the coverage rate of the first polymer binder per unit area in the first bonding coating is 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60% or any value between any two of the above numerical ranges. By regulating the coverage rate of the first polymer binder per unit area in the first bonding coating within the above range, the high bonding properties of the first bonding coating can be fully utilized, which is beneficial to the bonding of the isolation membrane and the pole piece. When the lithium ion has a faster transmission speed, it is more conducive to making the electrochemical device have good cycle dynamics performance.

[0065] In some embodiments of the present application, the first polymer binder includes a core-shell structure first polymer binder, the core of the core-shell structure first polymer binder includes at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, or maleic acid, and the shell of the core-shell structure first polymer binder includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene, chloromethyl acrylate, chlorostyrene, fluorostyrene, methylstyrene, acrylonitrile, or methacrylonitrile. The above-mentioned first polymer binder is applied to the first bonding coating layer, which can make the first bonding coating layer have high bonding strength.

[0066] In some embodiments of the present application, the first polymer binder includes a non-core-shell structure first polymer binder, and the polymerized monomer of the non-core-shell structure first polymer binder includes at least one of acrylic acid, methyl acrylate, butyl acrylate, butadiene, styrene, acrylonitrile, ethylene, fluorostyrene, chlorostyrene, or propylene. The above-mentioned first polymer binder is applied to the first bonding coating layer, which can provide the first bonding coating layer with high bonding strength.

[0067] In some embodiments of the present application, the first bonding coating layer includes a first polymer binder, a thickener, an auxiliary binder and a wetting agent. The thickener is applied to the first bonding coating layer to increase the stability of the first bonding coating layer slurry and prevent the sedimentation of the components in the first bonding coating layer slurry. The auxiliary binder is applied to the first bonding coating layer to bond the first polymer binder to the isolation membrane substrate and the ceramic coating during the application of the first bonding coating layer slurry. The wetting agent is applied to the first bonding coating layer to reduce the surface energy of the first bonding coating layer slurry and prevent the first bonding coating layer slurry from leaking during the coating process. The present application has no particular restrictions on the content of the first polymer binder, thickener, auxiliary binder and wetting agent in the first bonding coating layer, as long as the purpose of the present application can be achieved. For example, based on the mass of the first bonding coating layer, the mass percentage of the first polymer binder is 85% to 95%, the mass percentage of the thickener is 0.5% to 2%, the mass percentage of the auxiliary binder is 0% to 15%, and the mass percentage of the wetting agent is 4% to 10%.

[0068] The present application does not particularly limit the types of thickeners, auxiliary binders, and wetting agents, as long as the purpose of the present application can be achieved. For example, thickeners include but are not limited to sodium carboxymethyl cellulose. For example, auxiliary binders include but are not limited to homopolymers or copolymers polymerized from at least one of the following monomers: ethyl acrylate, butyl acrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic anhydride, dicarboxylic anhydride, acrylonitrile, butadiene, or monovinyl compounds. The present application does not particularly limit the types of the above-mentioned monovinyl compounds, as long as the purpose of the present application can be achieved. For example, monovinyl compounds include but are not limited to at least one of styrene, chlorostyrene, fluorostyrene, or methylstyrene. For example, wetting agents include but are not limited to sodium carboxymethyl cellulose, dimethyl siloxane, polyethylene oxide dimethyl siloxane, polyethylene oxide, oxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, oxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer, or at least one of dioctyl sodium sulfosuccinate.

[0069] In some embodiments of the present application, the coverage Cr2 of the second polymer binder per unit area in the second bonding coating is 40% to 60%. For example, the coverage of the second polymer binder per unit area in the second bonding coating is 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60% or any value between any two of the above numerical ranges. By regulating the coverage of the second polymer binder per unit area in the second bonding coating within the above range, the electrolyte flow channel between the pole piece and the separator can be fully realized, and the electrolyte has good flow wettability in the pole piece and the separator, so that the second bonding coating has a suitable thickness, thereby reducing the risk of energy density loss caused by the increase in volume of the electrochemical device due to the excessive thickness. In this way, the electrochemical device can take into account both cycle dynamics performance and high temperature stability, and can also improve the energy density of the electrochemical device.

[0070] In some embodiments of the present application, the polymerizable monomer of the second polymer binder includes at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, allyl chloride, acrylic acid, methyl acrylate, butyl acrylate, chlorostyrene, fluorostyrene, ethyl acrylate, ethyl methacrylate, methyl methacrylate, butyl methacrylate, ethyl chloromethacrylate, styrene, butadiene, or acrylonitrile. The use of the aforementioned second polymer binder can provide a large gap between the second bonding coating layer and the positive or negative electrode sheet.

[0071] In some embodiments of the present application, the second polymer binder includes a core-shell structured second polymer binder, wherein the monomers of the shell of the core-shell structured second polymer binder include at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, styrene, butadiene, acrylonitrile, acrylic acid, methyl acrylate, or butyl acrylate, and the monomers of the core of the core-shell structured second polymer binder include at least one of ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, or ethyl chloromethylacrylate. The use of the aforementioned second polymer binders can provide a large gap between the second bonding coating layer and the positive or negative electrode sheet.

[0072] In some embodiments of the present application, the second polymer binder includes a non-core-shell second polymer binder. The monomers of the non-core-shell second polymer binder include at least one of acrylic acid, methyl acrylate, butyl acrylate, butadiene, styrene, acrylonitrile, ethylene, propylene, chlorostyrene, fluorostyrene, vinylidene chloride, vinylidene fluoride, hexafluoropropylene, vinyl chloride, or allyl chloride. The use of these second polymer binders can create a large gap between the second bonding coating layer and the positive or negative electrode sheet.

[0073] In some embodiments of the present application, the second bonding coating layer includes a second polymer binder and an auxiliary binder. The auxiliary binder is applied to the second bonding coating layer, and the second polymer binder can be bonded to the isolation film substrate and the ceramic coating during the application of the second bonding coating slurry. The present application has no particular restrictions on the content of the second polymer binder and the auxiliary binder in the second bonding coating layer, as long as the purpose of the present application can be achieved. For example, based on the mass of the second bonding coating layer, the mass percentage of the second polymer binder is 85% to 95%, and the mass percentage of the auxiliary binder is 0% to 15%.

[0074] In some embodiments of the present application, the isolation film further comprises a ceramic coating, which is disposed between the isolation film substrate and the first bonding coating, and / or between the isolation film substrate and the second bonding coating. Figure 7 As shown, the isolation film 30 includes an isolation film substrate 31, a first bonding coating 32, a second bonding coating 33 and a ceramic coating 34. The first bonding coating 32 and the second bonding coating 33 are respectively arranged on both sides of the isolation film substrate 31, and the ceramic coating 34 is arranged between the isolation film substrate 31 and the first bonding coating 32. The second bonding coating 33 is adjacent to the surface of the isolation film substrate 31 away from the ceramic coating 34. In other embodiments, such as Figure 8 As shown, the isolation film 30 includes an isolation film substrate 31, a first bonding coating 32, a second bonding coating 33 and a ceramic coating 34. The first bonding coating 32 and the second bonding coating 33 are respectively arranged on both sides of the isolation film substrate 31, and the ceramic coating 34 is arranged between the isolation film substrate 31 and the second bonding coating 33. The first bonding coating 32 is adjacent to the surface of the isolation film substrate 31 away from the ceramic coating 34. In some other embodiments, such as Figure 9As shown, the separator 30 includes a separator substrate 31, a first bonding coating 32, a second bonding coating 33, and two ceramic coating layers 34. The first bonding coating 32 and the second bonding coating 33 are respectively disposed on either side of the separator substrate 31. One ceramic coating layer 34 is disposed between the separator substrate 31 and the first bonding coating 32. Meanwhile, another ceramic coating layer 34 is disposed between the separator substrate 31 and the second bonding coating 33. It should be noted that the two ceramic coating layers can be the same or different. The ceramic coating has good hardness and heat resistance. When the ceramic coating is disposed in the separator, it can prevent the separator from shrinking at high temperatures, thereby improving the hardness and heat resistance of the electrochemical device, thereby enabling the electrochemical device to have good high-temperature stability while maintaining good cycle kinetic performance. In the present application, it is preferred that the second bonding coating 33 faces the positive electrode plate 10, and the ceramic coating 34 is arranged between the isolation membrane substrate 31 and the second bonding coating 33. This structure can store electrolyte and provide additional electrolyte channels outside the electrolyte channels formed by the second bonding coating 33, thereby reducing the thickness of the second bonding coating 33 and improving the energy density. At the same time, it protects the isolation membrane substrate 31 from being oxidized by the high voltage of the positive electrode and can also reduce the coating thickness of the second bonding coating 33.

[0075] In some embodiments of the present application, the ceramic coating includes ceramic particles and a ceramic coating binder. The present application does not particularly limit the types of ceramic particles and ceramic coating binders, as long as the purpose of the present application can be achieved. For example, ceramic particles include but are not limited to at least one of aluminum oxide, boehmite, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium hydroxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, or silicon nitride. The ceramic coating binder includes but is not limited to at least one of polyvinylidene fluoride, polyacrylic acid, polymethyl methacrylate, polybutyl acrylate, or polyacrylonitrile. The present application does not particularly limit the content of ceramic particles and ceramic coating binder in the ceramic coating, as long as the purpose of the present application can be achieved. For example, based on the mass of the ceramic coating, the mass percentage of ceramic particles is 5% to 95%, and the mass percentage of ceramic coating binder is 5% to 95%. The present application does not particularly limit the average particle size of the ceramic particles, as long as the purpose of the present application can be achieved. For example, the average particle size of the ceramic particles is 1 μm to 3 μm. The present application has no particular limitation on the thickness of the ceramic coating. For example, the thickness of the ceramic coating may be 0.5 μm to 6 μm.

[0076] In this application, the average particle size can be understood as an equivalent diameter. This application does not particularly limit the method for regulating the average particle size of the first polymer binder, the average particle size of the second polymer binder, and the average particle size of the ceramic particles, as long as the purpose of this application can be achieved. For example, this can be achieved by directly purchasing the first polymer binder, the second polymer binder, and the ceramic particles whose average particle size is within the range of this application, or by crushing, grinding, or ball milling.

[0077] In this application, the thickness of the first bonding coating layer, the thickness of the second bonding coating layer, and the average particle size of the ceramic particles are obtained by observing and testing the parameters of a cross-sectional sample of the isolation membrane. This application does not particularly limit the method for preparing the cross-sectional sample of the isolation membrane, as long as it can achieve the objectives of this application. For example, the isolation membrane cross-section can be obtained by argon ion polishing or embedding sectioning.

[0078] The present application does not particularly limit the isolation film substrate, as long as it can achieve the purpose of this application. For example, the structure of the isolation film substrate includes a single-layer structure or a multi-layer composite structure, wherein the multi-layer composite structure can be a double-layer composite structure, a three-layer composite structure, or a four-layer composite structure. The type of the isolation film substrate includes at least one of polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET). The thickness of the isolation film substrate can be 3 μm to 20 μm.

[0079] In some embodiments of the present application, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, or lithium titanate. The chemical formula of the above-mentioned lithium-rich manganese-based materials is LiMnO·LiMO, where M may include Ni, Co, or Mn. The above-mentioned types of positive electrode active materials have high surface activity and are applied to electrochemical devices to increase the active sites for lithium ion insertion and extraction, reduce the electrochemical polarization of the electrochemical device, and thus reduce the impedance of the electrochemical device, so that the electrochemical device has good cycle kinetics performance on the basis of high temperature stability.

[0080] In some embodiments of the present application, the positive electrode active material contains non-metallic elements, and the non-metallic elements include at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur. The present application has no particular restrictions on the content of non-metallic elements in the positive electrode active material, as long as the purpose of the present application can be achieved. In some embodiments of the present application, based on the mass of the positive electrode active material, the mass percentage of non-metallic elements is 0.1% to 10%. For example, the mass percentage of non-metallic elements is 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value between any two of the above numerical ranges. Including the above-mentioned types of non-metallic elements in the positive electrode active material can further improve the stability of the positive electrode active material. The above-mentioned non-metallic elements can be added to the positive electrode active material by bulk doping or surface coating with a single substance or compound containing the above-mentioned non-metallic elements.

[0081] In some embodiments of the present application, the negative electrode active material includes at least one of a carbon-based material, a silicon-based material, or a tin-based material, the carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, or mesophase carbon microbeads, the silicon-based material includes at least one of a silicon material, a silicon-carbon material, or a silicon-oxygen material, and the tin-based material includes at least one of elemental tin, a tin alloy, or a tin oxide. The above-mentioned types of negative electrode active materials have high surface activity and, when applied to electrochemical devices, can increase active sites for lithium ion insertion and extraction, reduce the electrochemical polarization of the electrochemical device, and thus reduce the impedance of the electrochemical device, so that the electrochemical device has good cycle kinetics while having high temperature stability.

[0082] In some embodiments of the present application, the carbon-based material is tested by Raman with a peak intensity ratio of d peak to g peak of d / I g Satisfy: 0.1≤I d / I g ≤1. This indicates that the surface of the carbon-based material contains amorphous carbon, which can enhance the electrochemical activity of the carbon-based material and make the lithium ion embedding smoother during the cycling of the electrochemical device, thereby reducing the electrochemical polarization of the electrochemical device, thereby reducing the internal impedance of the electrochemical device and improving its cycling kinetics. d / I g The application of high-value carbon-based materials in electrochemical devices is beneficial to further improve the cycle kinetics performance of electrochemical devices on the basis of good high-temperature stability.

[0083] In this application, the d peak is the shift range of 1300 cm in the Raman spectrum of carbon-based material particles. -1 to 1400cm -1 The peak of g is the shift range of 1530cm in the Raman spectrum of carbon-based material particles. -1to 1630cm -1 Peak.

[0084] This application is for d / I g There is no particular limitation on the method for controlling the value of , as long as the purpose of this application can be achieved. For example, commercially available carbon-based materials with different amounts of amorphous carbon coated on their surfaces can be selected, and the I value of the carbon-based materials can be determined by combining the Raman test method in this application. d / I g , select the desired d / I g of carbon-based materials.

[0085] The present application does not particularly limit the preparation method of the carbon-based material, as long as the purpose of the present application can be achieved. For example, the preparation method of the carbon-based material may include but is not limited to: mixing the carbon-based material and amorphous carbon uniformly, heating to 500°C to 1500°C, and then maintaining the temperature for 10 hours to 20 hours to obtain a carbon-based material with amorphous carbon coated on the surface.

[0086] The positive electrode sheet of the present application includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. In some embodiments, the positive electrode active material layer is disposed on one surface of the positive electrode current collector. In other embodiments, the positive electrode active material layer is disposed on both surfaces of the positive electrode current collector. The aforementioned "surface" may be part of the surface or the entire surface of the positive electrode current collector. The present application does not particularly limit the type of positive electrode current collector, as long as the objectives of the present application can be achieved. For example, the positive electrode current collector may include, but is not limited to, aluminum foil or aluminum alloy foil. The positive electrode active material layer of the present application includes the positive electrode active material described in the aforementioned embodiments. In the present application, there is no particular limitation on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the objectives of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5μm to 20μm, and further, the thickness of the positive electrode current collector may be 6μm to 18μm. The thickness of the positive electrode active material layer is 30μm to 120μm.

[0087] Optionally, the positive electrode active material layer may further include a positive electrode conductor and a positive electrode binder. The present application has no particular restrictions on the types of positive electrode conductors and positive electrode binders in the positive electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the mass ratio of the positive electrode active material, the positive electrode conductor, and the positive electrode binder in the positive electrode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. For example, the mass ratio of the positive electrode active material, the positive electrode conductor, and the positive electrode binder in the positive electrode active material layer is (95-98): (0.5-2.5): (1.5-3.4).

[0088] The negative electrode sheet of the present application includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. In some embodiments, the negative electrode active material layer is disposed on one surface of the negative electrode current collector. In other embodiments, the negative electrode active material layer is disposed on both surfaces of the negative electrode current collector. The above-mentioned "surface" can be part of the surface or the entire surface of the negative electrode current collector. The present application does not particularly limit the type of negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the negative electrode current collector includes but is not limited to copper foil, copper alloy foil, nickel foil, titanium foil, nickel foam or copper foam. The negative electrode active material layer of the present application includes the negative electrode active material described in the above embodiments. In the present application, there is no particular limitation on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 6μm to 10μm, and the thickness of the negative electrode active material layer is 30μm to 130μm.

[0089] Optionally, the negative electrode active material layer may further include at least one of a negative electrode conductor, a stabilizer or a negative electrode binder. The present application does not particularly limit the types of negative electrode conductors, stabilizers and negative electrode binders in the negative electrode active material layer, as long as the purpose of the present application can be achieved. The present application does not particularly limit the mass ratio of the negative electrode active material, the negative electrode conductor, the stabilizer and the negative electrode binder in the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the mass ratio of the negative electrode active material, the negative electrode conductor, the stabilizer and the negative electrode binder in the negative electrode active material layer is (96-98):(0.5-2):(0-1.5):(1.0-1.9).

[0090] The electrochemical device of the present application also includes an electrolyte, which includes a lithium salt and a non-aqueous solvent. The present application has no particular restrictions on the lithium salt, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, lithium bis(oxalatoborate) or lithium difluoroborate. Preferably, the lithium salt includes LiPF6. The present application has no particular restrictions on the non-aqueous solvent, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of a carbonate compound, a carboxylate compound, an ether compound or other organic solvent. The above-mentioned carbonate compound may include but is not limited to at least one of a chain carbonate compound, a cyclic carbonate compound, and a fluorinated carbonate compound. Above-mentioned linear carbonate compound can include but not limited to at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC) or methyl ethyl carbonate (MEC).Cyclic carbonate can include but not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC).Fluorinated carbonate compound can include but not limited to at least one of 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 or trifluoromethylethylene carbonate. The carboxylate compound may include but is not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerolactone, mevalonolactone or caprolactone. The ether compound may include but is not limited to at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphate.

[0091] In some embodiments of the present application, the electrochemical device further includes a housing, in which the electrode assembly and electrolyte are housed. The present application does not particularly limit the housing and may be any known housing in the art, as long as it can achieve the objectives of the present application. For example, the housing includes, but is not limited to, aluminum-plastic film and steel shell.

[0092] The electrochemical device of the present application is not particularly limited and may include any device that generates an electrochemical reaction. In some embodiments, the electrochemical device may include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0093] The present application has no particular limitation on the method for preparing the isolation membrane, as long as the purpose of the present application can be achieved.

[0094] For example, in some embodiments, the preparation method of the isolation membrane includes but is not limited to the following steps: (1) uniformly mixing a first polymer binder, a thickener, an auxiliary binder and a wetting agent to obtain a first bonding coating slurry; (2) uniformly mixing a second polymer binder and an auxiliary binder to obtain a second bonding coating slurry; (3) coating the first bonding coating slurry on one surface of the isolation membrane substrate, and forming a first bonding coating on one surface of the isolation membrane substrate after drying; coating the second bonding coating slurry on the other surface of the isolation membrane substrate, and forming a second bonding coating on the other surface of the isolation membrane substrate after drying, thereby obtaining an isolation membrane.

[0095] For example, in some other embodiments, the preparation method of the isolation membrane includes but is not limited to the following steps: (1) mixing a first polymer binder, a thickener, an auxiliary binder and a wetting agent evenly to obtain a first bonding coating slurry; (2) mixing a second polymer binder and an auxiliary binder evenly to obtain a second bonding coating slurry; (3) mixing ceramic particles and a ceramic coating binder evenly to obtain a ceramic coating slurry; (4) coating the ceramic coating slurry on one surface of the isolation membrane substrate, and after drying, forming a ceramic coating on one surface of the isolation membrane substrate; coating the first bonding coating slurry on the surface of the ceramic coating, and after drying, forming a first bonding coating on the surface of the ceramic coating away from the isolation membrane substrate; coating the second bonding coating slurry on the other surface of the isolation membrane substrate, and after drying, forming a second bonding coating on the other surface of the isolation membrane substrate, thereby obtaining an isolation membrane.

[0096] For example, in some further embodiments, the preparation method of the isolation membrane includes but is not limited to the following steps: (1) uniformly mixing a first polymer binder, a thickener, an auxiliary binder and a wetting agent to obtain a first bonding coating slurry; (2) uniformly mixing a second polymer binder and an auxiliary binder to obtain a second bonding coating slurry; (3) uniformly mixing ceramic particles and a ceramic coating binder to obtain a ceramic coating slurry; (4) coating the ceramic coating slurry on one surface of the isolation membrane substrate, and after drying, forming a ceramic coating on one surface of the isolation membrane substrate; coating the second bonding coating slurry on the surface of the ceramic coating, and after drying, forming a second bonding coating on the surface of the ceramic coating away from the isolation membrane substrate; coating the first bonding coating slurry on the other surface of the isolation membrane substrate, and after drying, forming the first bonding coating on the other surface of the isolation membrane substrate, thereby obtaining an isolation membrane.

[0097] For example, in some further embodiments, the preparation method of the isolation membrane includes but is not limited to the following steps: (1) uniformly mixing a first polymer binder, a thickener, an auxiliary binder and a wetting agent to obtain a first bonding coating slurry; (2) uniformly mixing a second polymer binder and an auxiliary binder to obtain a second bonding coating slurry; (3) uniformly mixing ceramic particles and a ceramic coating binder to obtain a ceramic coating slurry; (4) coating the ceramic coating slurry on one surface of the isolation membrane substrate, and after drying, forming a ceramic coating on one surface of the isolation membrane substrate; coating the ceramic coating slurry on the other surface of the isolation membrane, and after drying, forming a ceramic coating on the other surface of the isolation membrane substrate; coating the second bonding coating slurry on the surface of the first ceramic coating away from the isolation membrane substrate, and after drying, forming a second bonding coating on the surface of the first ceramic coating away from the isolation membrane substrate; coating the first bonding coating slurry on the surface of the second ceramic coating away from the isolation membrane substrate, and after drying, forming a first bonding coating on the surface of the second ceramic coating away from the isolation membrane substrate, thereby obtaining an isolation membrane.

[0098] The present application has no particular restrictions on the solid content of the above-mentioned first bonding coating slurry, as long as the purpose of this application can be achieved. For example, the solid content of the first bonding coating slurry is 60wt% to 80wt%. The present application has no particular restrictions on the solid content of the above-mentioned second bonding coating slurry, as long as the purpose of this application can be achieved. For example, the solid content of the second bonding coating slurry is 60wt% to 80wt%. The present application has no particular restrictions on the solid content of the above-mentioned ceramic coating slurry, as long as the purpose of this application can be achieved. For example, the solid content of the ceramic coating slurry is 30wt% to 40wt%. The present application has no particular restrictions on the temperature and time of the above-mentioned drying, and those skilled in the art can select and adjust according to actual needs, as long as the purpose of this application can be achieved.

[0099] The present application has no particular restrictions on the preparation method of the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, the preparation method of the positive electrode sheet includes but is not limited to the following steps: (1) preparing a positive electrode slurry; (2) coating the positive electrode slurry on one surface of the positive electrode main region of the positive electrode current collector, and after drying, forming a positive electrode active material layer on one surface of the positive electrode main region of the positive electrode current collector; (3) coating the positive electrode slurry on the other surface of the positive electrode main region of the positive electrode current collector, and after drying, forming a positive electrode active material layer on each of the two surfaces of the positive electrode main region of the positive electrode current collector; (4) after cold pressing, die-cutting the positive electrode tab area of ​​the positive electrode current collector so that the positive electrode current collector extends integrally to form multiple positive electrode tabs, and finally slitting to obtain a positive electrode sheet. The present application has no particular restrictions on the content and type of each component in the positive electrode slurry in the above step (1). Those skilled in the art can choose according to actual conditions, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the solid content of the positive electrode slurry in the above step (1), as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the drying time and temperature in the above steps (2) and (3), as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the process parameters of the cold pressing in the above step (4), as long as the purpose of the present application can be achieved.

[0100] The present application has no particular restrictions on the preparation method of the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, the preparation method of the negative electrode sheet includes but is not limited to the following steps: (1) preparing a negative electrode slurry; (2) coating the negative electrode slurry on one surface of the negative electrode main region of the negative electrode current collector, and after drying, forming a negative electrode active material layer on one surface of the negative electrode main region of the negative electrode current collector; (3) coating the negative electrode slurry on the other surface of the negative electrode main region of the negative electrode current collector, and after drying, forming a negative electrode active material layer on each of the two surfaces of the negative electrode main region of the negative electrode current collector; (4) after cold pressing, die-cutting the negative electrode tab area of ​​the negative electrode current collector so that the negative electrode current collector extends integrally to form multiple negative electrode tabs, and finally slitting to obtain a negative electrode sheet. The present application has no particular restrictions on the content and type of each component in the negative electrode slurry in the above step (1). Those skilled in the art can select according to actual conditions, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the solid content of the negative electrode slurry in the above step (1), as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the drying time and temperature in the above steps (2) and (3), as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the process parameters of the cold pressing in the above step (4), as long as the purpose of the present application can be achieved.

[0101] This application does not particularly limit the preparation method of the electrochemical device. Preparation methods known in the art may be used as long as the purpose of this application can be achieved. For example, the preparation method of the electrochemical device includes but is not limited to the following steps: stacking a separator, a positive electrode sheet, a separator, and a negative electrode sheet in sequence, and winding and folding them as needed to obtain a wound electrode assembly; spot welding multiple positive electrode tabs and multiple negative electrode tabs; placing the electrode assembly in a housing; injecting an electrolyte into the housing and sealing it to obtain the electrochemical device.

[0102] In a second aspect of the present application, an electronic device is provided, which includes the electrochemical device according to any one of the aforementioned embodiments. Therefore, the electronic device has good performance.

[0103] The electronic device of the present application is not particularly limited and can be any electronic device known in the art. For example, the electronic device can include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0104] Example

[0105] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0106] Test methods and equipment:

[0107] Testing of relevant particle sizes

[0108] For the average particle size of the first polymer binder and the second polymer binder, the surface of the isolation membrane perpendicular to the thickness direction can be observed by scanning electron microscopy (SEM), and the diameter of 10 first polymer binder or second polymer binder particles is measured and averaged. Wherein, the first polymer binder and the second polymer binder are distinguished by particle diameter size. Specifically, in the surface of the isolation membrane, the side with relatively smaller diameter of each particle is the first bonding coating containing the first polymer binder, and 10 first polymer binders are arbitrarily selected in the first bonding coating to obtain the average particle size of the first polymer binder; the side with relatively larger diameter of each particle is the second bonding coating containing the second polymer binder, and 10 second polymer binders are arbitrarily selected in the second bonding coating to obtain the average particle size of the second polymer binder. Since the particles of the first polymer binder and the second polymer binder will be deformed under the pressure of cold pressing, hot pressing and other processes during the preparation of the electrochemical device, the diameters of the particles along the thickness direction of the isolation membrane and the direction perpendicular to the thickness direction of the isolation membrane are different. The average particle size of the first polymer binder and the second polymer binder of the present application is the diameter measured on the surface of the particles perpendicular to the thickness direction of the isolation membrane. Therefore, the average particle size of the above-mentioned first polymer binder and the second polymer binder is not limited by the thickness of the first bonding coating and the second bonding coating.

[0109] The average particle size of the ceramic particles on the isolation film can be determined by observing the cross section of the isolation film after argon ion polishing using a SEM, measuring the diameters of 10 ceramic particles, and calculating the average value.

[0110] The Dv50 and Dv99 of the positive and negative active materials were measured using a laser particle size analyzer.

[0111] Test of single-sided coating weight of the first bonding coat:

[0112] The lithium-ion batteries of the examples and comparative examples were discharged at 0.5C to 3.0V, and then disassembled to obtain the separators. The impurities on the separator surface were cleaned with DMC and dried at 60°C to obtain the test samples of the separators. An area of ​​Smm was punched out on the test samples of the separators. 2 The small disc is weighed and recorded as m1, and then the first bonding coating on the small disc is peeled off to obtain the mass of the small disc after peeling off the first bonding coating, which is recorded as m2. The single-sided coating weight of the first bonding coating = (m1-m2) / S.

[0113] Test for single-sided coating weight of the second bonding coat:

[0114] The lithium-ion batteries of the examples and comparative examples were discharged at 0.5C to 3.0V, and then disassembled to obtain the separators. The impurities on the separator surface were cleaned with DMC and dried at 60°C to obtain the test samples of the separators. An area of ​​Smm was punched out on the test samples of the separators. 2 The small disc is weighed and recorded as m3, and then the second bonding coating on the small disc is peeled off to obtain the mass of the small disc after peeling off the second bonding coating, recorded as m4, and the single-sided coating weight of the second bonding coating = (m3-m4) / S.

[0115] Test of thickness of first bonding coating and second bonding coating:

[0116] The coated separator was subjected to argon ion polishing to obtain a cross-section of the separator. The cross-section was observed using a scanning electron microscope (SEM) to measure the thickness of the first and second bonding coating layers. In the separator cross-section, the side with the smaller particle diameter represents the first bonding coating layer containing the first polymer binder, while the side with the larger particle diameter represents the second bonding coating layer containing the second polymer binder.

[0117] Test of coverage of the first polymer binder:

[0118] The surface of the isolation membrane provided with the first adhesive coating was observed by SEM, and the coverage was obtained by dividing the area occupied by the first polymer binder in the electron microscope photograph by the area of ​​the isolation membrane sampled in the entire electron microscope photograph.

[0119] Second polymer binder coverage test:

[0120] The surface of the coated isolation film provided with the second adhesive coating was observed by SEM, and the coverage was obtained by dividing the area occupied by the second polymer binder in the electron microscope photograph by the area of ​​the isolation film sampled in the entire electron microscope photograph.

[0121] Raman test:

[0122] After the lithium-ion battery was discharged, it was disassembled to obtain the negative electrode sheet. After being cleaned with dimethyl carbonate and dried, an area of ​​100 μm × 100 μm was selected on the negative electrode active material layer. The negative electrode active material particles within the area were scanned using a laser microconfocal Raman spectrometer (Raman, HR Evolution, HORIBA Scientific Instrument Division) to obtain the d peak and g peak of all the negative electrode active material particles within the area. The data were processed using LabSpec software to obtain the peak intensities of the d peak and g peak of each negative electrode active material particle, which were I, G, and L, respectively. d and I g The laser wavelength of the Raman spectrometer is in the range of 532nm to 785nm. d / I g The value of is the I of all negative electrode active material particles measured within this range. d and I g The average of the ratios.

[0123] Test of the bonding force F1 of the separator to the positive electrode:

[0124] The dry-pressed adhesion strength between the separator and the positive electrode sheet was measured using a 180° peel test. The lithium-ion batteries in the tested examples and comparative examples were discharged and disassembled. The negative electrode sheet was peeled off, and the separator and positive electrode sheet were soaked in dimethyl carbonate for 20 minutes to remove the electrolyte. The separator and positive electrode sheet were then cut into 54.2 mm × 72.5 mm samples. The side of the separator provided with the second adhesive coating was laminated to the positive electrode sheet. The samples were hot-pressed using a hot press at 85°C, 1 MPa, and 85 seconds. The laminated samples were then cut into 15 mm × 54.2 mm strips to obtain test strips for the separator-to-positive electrode sheet adhesion test. A 15 mm × 55 mm piece of double-sided tape (NITTO.NO5000NS) was applied to a steel plate, and the test strips were then attached to the tape with the test side facing down. Connect a 15mm×70mm paper tape to one end of the test specimen with double-sided tape, and manually push a small stick with a mass of 2kg to roll on the test specimen 8 times to obtain a test sample. Use a tensile testing machine for testing. Fix the test sample on the test bench, fold the paper tape 180° upwards, and fix it with a clamp. Then the tensile testing machine starts pulling the paper tape at a speed of 50mm / min until the isolation film on the surface of the double-sided tape and the positive electrode are separated. End the test and save the test data. The bonding force F1 between the isolation film and the positive electrode is calculated based on the tensile force and the stretched displacement when the isolation film and the positive electrode are separated. The unit is N / m.

[0125] Test of the bonding force F2 of the separator to the negative electrode:

[0126] The dry-pressed adhesion strength between the separator and the negative electrode sheet was measured using a 180° peel test. The lithium-ion batteries in the examples and comparative examples were discharged and disassembled. The positive electrode sheet was peeled off and the separator and negative electrode sheet were soaked in dimethyl carbonate for 20 minutes to remove the electrolyte. The separator and negative electrode sheet were then cut into 54.2 mm x 72.5 mm samples. The side of the separator provided with the first adhesive coating was laminated to the negative electrode sheet and hot-pressed using a hot press at 85°C, 1 MPa, and 85 seconds. The laminated sample was then cut into 15 mm x 54.2 mm strips to obtain test specimens for the separator-to-negative-electrode adhesion test. The adhesion strength F2 between the separator and the negative electrode sheet was then measured using the same procedure as described for the separator-to-positive-electrode adhesion test (unit: N / m).

[0127] Cyclic dynamics performance test:

[0128] The lithium-ion batteries of the embodiments and comparative examples were subjected to a cycle dynamics performance test at a charge rate of 10C, and the specific steps are as follows:

[0129] (1) Adjust the test temperature to a constant temperature of 25°C, place the temperature sensing line of the multi-channel thermometer at the center of the lithium-ion battery surface, and perform the following steps: 1) 10C constant current charge to 4.2V; 2) 8C constant current charge to 4.3V; 3) 6C constant current charge to 4.45V; 4) 4.45V constant voltage charge to 0.05C; 5) stand for 30 minutes; 6) 1C constant current discharge to 3.0V; 7) stand for 30 minutes; end;

[0130] 10C charging speed: time from step 1) to step 4);

[0131] 10C charging temperature rise: The difference between the maximum temperature recorded by the temperature sensing line on the surface of the lithium-ion battery during step 1) to step 4) and the room temperature.

[0132] (2) Adjust the test temperature to 25°C and start the test: 1) 10C constant current charge to 4.2V; 2) 8C constant current charge to 4.3V; 3) 6C constant current charge to 4.45V; 4) 4.45V constant voltage charge to 0.05C; 5) Stand for 5 minutes; 6) 1C constant current discharge to 3.0V; 7) Stand for 5 minutes; 8) Steps 1) to 7) are cycled 1000 times (cls) and the discharge capacity of the first cycle and the discharge capacity after 1000 cycles are recorded; end;

[0133] 25°C 1000 cls capacity retention (%) = discharge capacity after 1000 cycles (cls) / first cycle discharge capacity × 100%.

[0134] The cycling kinetics performance is characterized by 10C charging speed, 10C charging temperature rise and 25℃1000cls capacity retention rate. Among them, the shorter the 10C charging time, the smaller the 10C charging temperature rise and the higher the 25℃1000cls capacity retention rate, the better the cycling kinetics performance.

[0135] High temperature stability test:

[0136] Test the thickness of the lithium-ion battery after it is manufactured, referred to as the initial thickness of the lithium-ion battery;

[0137] The lithium-ion battery is fully charged according to the following steps: charge at a constant current of 0.7C to 4.45V, and charge at a constant voltage of 4.45V to 0.02C;

[0138] The lithium-ion battery was placed in a high and low temperature box at 80°C and stored for 8 hours. The thickness of the lithium-ion battery after storage at 80°C was tested, and the test was completed.

[0139] 80° C. storage expansion ratio=(thickness of the lithium ion battery after storage at 80° C.−initial thickness of the lithium ion battery) / initial thickness of the lithium ion battery×100%.

[0140] The storage expansion ratio at 80°C is used to characterize the high-temperature stability. The smaller the storage expansion ratio at 80°C, the better the high-temperature stability.

[0141] Example 1-1

[0142] <Preparation of Separator>

[0143] A single-layer polypropylene film with a thickness of 5 μm is used as the base material of the isolation membrane;

[0144] The ceramic particles aluminum oxide, ceramic coating binder butadiene-styrene polymer (weight average molecular weight Mw = 7 × 10 6 ), solvent deionized water is mixed according to a mass ratio of 35:10:55. Specifically, 30 kg of butadiene-styrene polymer and deionized water are first added to a double planetary mixer with a volume of 60 L, and dispersed at 45° C. for 3 hours; then 16.1 kg of aluminum oxide ceramic particles are added to the mixer and dispersed at high speed at 45° C. for 2 hours; then, ball milling is performed using a nano grinder for 1.5 hours, using spherical zirconium oxide beads with a diameter of 6 μm as the grinding medium to obtain a ceramic coating slurry; the average particle size of the ceramic particles is 2 μm;

[0145] The first polymer binder polyacrylic acid (Mw = 3 × 10 3 ), thickener sodium carboxymethyl cellulose (Mw = 9 × 10 4 ~3×10 5 ) and wetting agent polyoxyethylene ether (Mw = 5 × 10 3 ) are mixed in a mass ratio of 91:0.5:8.5, deionized water is added as a solvent, and the mixture is stirred evenly to form a first bonding coating slurry with a solid content of 75 wt %; the average particle size of the first polymer binder is 1.6 μm; the first polymer binder has a non-core-shell structure;

[0146] The second polymer binder polyvinylidene fluoride (Mw = 8.5 × 10 5 ) and auxiliary binder methacrylic acid according to a mass ratio of 90:10, deionized water is added as a solvent, and stirred evenly to form a second bonding coating slurry with a solid content of 75wt%; the average particle size of the second polymer binder is 25μm; the second polymer binder is a non-core-shell structure;

[0147] A ceramic coating slurry is coated on one surface of the isolation membrane substrate, and after drying at 60°C, a ceramic coating is formed on one surface of the isolation membrane substrate; a second bonding coating slurry is coated on the surface of the ceramic coating away from the isolation membrane substrate, and after drying at 60°C, a second bonding coating is formed on the surface of the ceramic coating away from the isolation membrane substrate; a first bonding coating slurry is coated on the other surface of the isolation membrane substrate, and after drying at 60°C, a first bonding coating is formed on the other surface of the isolation membrane substrate, thus preparing an isolation membrane (see the structure). Figure 8 But not Figure 8 limited).

[0148] The single-sided coating weight of the first adhesive coating layer is Cw1 = 0.0006 mg / mm 2 The thickness of the first bonding coating layer is H1 = 2 μm, and the single-sided coating weight of the second bonding coating layer is Cw2 = 0.0012 mg / mm 2 The thickness of the second bonding coating is H2 = 12 μm. The single-sided coating weight of the ceramic coating is Cw3 = 0.0023 mg / mm 2 The thickness of the ceramic coating is H3 = 1 μm. The coverage rate Cr1 of the first polymer binder per unit area in the first bonding coating is 50%, and the coverage rate Cr2 of the second polymer binder per unit area in the second bonding coating is 50%.

[0149] <Preparation of positive electrode sheet>

[0150] The positive electrode active material is lithium cobalt oxide, the positive electrode conductive agent is superconducting carbon (Super P), and the positive electrode binder is polyvinylidene fluoride (PVDF, Mw = 7×10 6 ) were mixed in a mass ratio of 97:1:2, and N-methylpyrrolidone (NMP) was added as a solvent. The mixture was stirred in a vacuum mixer until a solid content of 75 wt% and a uniform system was obtained. The positive electrode slurry was evenly coated on the positive electrode main body area of ​​one surface of a 10 μm thick positive electrode current collector aluminum foil and dried at 95°C to obtain a positive electrode sheet coated with a positive electrode active material layer on one side. The above steps were then repeated on the positive electrode main body area of ​​the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. The sheet was then cold pressed, die-cut in the positive electrode tab area of ​​the positive electrode current collector to form positive electrode tabs, and then stripped. After stripping, the sheet was dried at 85°C under vacuum for 4 hours to obtain a positive electrode sheet with a size of 60 mm × 1580 mm for later use. The single layer thickness of the positive electrode active material layer was 36.5 μm, and the thickness of the positive electrode sheet was 83 μm. The positive electrode tab area of ​​the positive electrode current collector extends integrally (see the structure for Figure 3 But not Figure 3 The compaction density of the positive electrode sheet is 4.0g / cm 3The positive electrode active material lithium cobalt oxide has a Dv99 of 30 μm and a Dv50 of 12 μm.

[0151] <Preparation of negative electrode sheet>

[0152] The negative electrode active material, negative electrode conductive agent Super P, stabilizer sodium carboxymethyl cellulose (CMC-Na, Mw = 7 × 10 5 ), negative electrode binder styrene-butadiene rubber (SBR, Mw = 5 × 10 6 ) are mixed in a mass ratio of 95:2.0:1.5:1.5, and then deionized water is added as a solvent, and stirred under the action of a vacuum mixer until the solid content is 51wt% and the system is uniform. The negative electrode slurry is evenly coated on the negative electrode main area of ​​one surface of the negative electrode current collector copper foil with a thickness of 6μm, and dried at 85°C to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. After that, the above steps are repeated on the negative electrode main area on the other surface of the copper foil to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. It is then cold pressed and die-cut in the negative electrode tab area of ​​the negative electrode current collector to form a negative electrode tab, and stripped. After stripping, it is dried at 110°C for 4h under vacuum conditions to obtain a negative electrode sheet with a specification of 62mm×1600mm for standby use. Among them, the single layer thickness of the negative electrode active material layer is 56μm, and the thickness of the negative electrode sheet is 118μm. The negative electrode tab area of ​​the negative electrode current collector extends as a whole (see the structure) Figure 4 But not Figure 4 The negative electrode tabs are formed with a density of 20. The compaction density of the negative electrode tab is 1.5 g / cm 3 The negative electrode active material has a Dv99 of 25 μm and a Dv50 of 9 μm. The types of negative electrode active materials are shown in Table 5.

[0153] <Preparation of Electrolyte>

[0154] In an environment with a water content of less than 10 ppm, n-propyl propionate, ethylene carbonate, and diethyl carbonate are mixed in a mass ratio of 40:30:30 as a solvent, and lithium salt lithium hexafluorophosphate (LiPF6), solvent, and additive glutaronitrile are prepared in a mass ratio of 10:84:6 to obtain an electrolyte.

[0155] <Preparation of lithium-ion batteries>

[0156] Stack the separator, positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then wind them to obtain an electrode assembly. The positive electrode tab is spot-welded with an aluminum tab, and the negative electrode tab is spot-welded with a nickel tab. Among them, the first bonding coating in the separator is close to the negative electrode sheet, and the second bonding coating is close to the positive electrode sheet. After winding, N1=0 layers of positive electrode sheets are arranged between two adjacent positive electrode tabs in the electrode assembly, and N2=0 layers of negative electrode sheets are arranged between two adjacent negative electrode tabs. There is one positive electrode tab on each layer of positive electrode tabs, and one negative electrode tab on each layer of negative electrode tabs (for the arrangement of positive and negative tabs, see Figure 1 But not Figure 1 The electrode assembly is placed in an aluminum-plastic film shell, dried, and then injected with electrolyte. The lithium-ion battery is obtained through vacuum packaging, standing, formation, capacity, degassing, and trimming processes.

[0157] Example 1-2 to Example 1-17

[0158] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0159] Examples 1-18

[0160] The same as Example 1-1 except that N1 = 1 and N2 = 1 are used. The number of positive electrode tabs and negative electrode tabs are adjusted to achieve N1 = 1 and N2 = 1.

[0161] Examples 1-19

[0162] The same as Example 1-1 except that N1 = 2 and N2 = 2. The number of positive electrode tabs and negative electrode tabs is adjusted to make N1 = 2 and N2 = 2.

[0163] Example 1-20 to Example 1-23

[0164] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0165] Examples 1-24

[0166] <Preparation of lithium-ion batteries>

[0167] Except that the first bonding coating layer in the separator is close to the positive electrode plate and the second bonding coating layer is close to the negative electrode plate, the rest is the same as Example 1-1.

[0168] <Preparation of positive electrode sheet>, <Preparation of negative electrode sheet>, <Preparation of separator>, and <Preparation of electrolyte> are the same as those in Example 1-1.

[0169] Example 2-1 to Example 2-16

[0170] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as Example 1-1.

[0171] Example 3-1

[0172] Except for adjusting the relevant preparation parameters according to Table 5, the rest is the same as Example 1-1.

[0173] Example 3-2 to Example 3-4

[0174] The process was the same as Example 1-1, except that artificial graphite coated with amorphous carbon was used as the negative electrode active material in the preparation of the negative electrode sheet. The mass ratio of artificial graphite to amorphous carbon was adjusted according to Table 5.

[0175] Example 3-5 and Example 3-6

[0176] Except for adjusting the relevant preparation parameters according to Table 5, the rest is the same as Example 1-1.

[0177] Comparative Example 1

[0178] <Preparation of positive electrode sheet>

[0179] The positive electrode active material is lithium cobalt oxide, the positive electrode conductive agent is superconducting carbon (Super P), and the positive electrode binder is polyvinylidene fluoride (PVDF, Mw = 7×10 6 ) are mixed in a mass ratio of 97:1:2, N-methylpyrrolidone (NMP) is added as a solvent, and stirred under the action of a vacuum mixer until the solid content is 75wt% and the system is uniform. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 95°C to obtain a positive electrode sheet with a single-sided positive electrode active material layer. Thereafter, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode active material layer. It is then cold pressed, cut into pieces, and slit. After slit, it is dried at 85°C under vacuum for 4h, and a positive electrode tab is welded to the surface of the positive electrode collector to obtain a positive electrode sheet with a specification of 60mm×1580mm for standby use. Among them, the single layer thickness of the positive electrode active material layer is 36.5μm, and the thickness of the positive electrode sheet is 83μm. The compaction density of the positive electrode sheet is 4.0g / cm 3 The positive electrode active material lithium cobalt oxide has a Dv99 of 30 μm and a Dv50 of 12 μm.

[0180] <Preparation of negative electrode sheet>

[0181] The negative electrode active material, negative electrode conductive agent Super P, stabilizer sodium carboxymethyl cellulose (CMC-Na, Mw = 7 × 10 5), negative electrode binder styrene-butadiene rubber (SBR, Mw = 5 × 10 6 ) are mixed in a mass ratio of 95:2.0:1.5:1.5, and then deionized water is added as a solvent. The mixture is stirred under a vacuum mixer until the solid content is 51wt% and the system is uniform. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm and dried at 85°C to obtain a negative electrode sheet with a single-sided negative electrode active material layer. Thereafter, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided negative electrode active material layer. The sheet is then cold pressed, cut into pieces, and slit. After slit, it is dried at 110°C under vacuum for 4 hours. A negative electrode tab nickel tab is welded to the surface of the negative electrode current collector to obtain a negative electrode sheet with a specification of 62mm×1600mm for standby use. Among them, the single layer thickness of the negative electrode active material layer is 56μm, and the thickness of the negative electrode sheet is 118μm. The compaction density of the negative electrode sheet is 1.5g / cm 3 The negative electrode active material had a Dv99 of 25 μm and a Dv50 of 9 μm. The type of negative electrode active material was the same as that of Example 1-1.

[0182] <Preparation of lithium-ion batteries>

[0183] The separator, positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. The electrodes are then wound to form an electrode assembly. The first adhesive coating layer in the separator is positioned adjacent to the negative electrode sheet, while the second adhesive coating layer is positioned adjacent to the positive electrode sheet. The electrode assembly is then placed in an aluminum-plastic film casing, dried, and then filled with electrolyte. The lithium-ion battery is then produced through vacuum packaging, resting, formation, capacity measurement, degassing, and trimming.

[0184] <Preparation of Separator> and <Preparation of Electrolyte> were the same as those in Example 1-1.

[0185] Comparative Examples 2 to 9

[0186] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0187] Comparative Example 10

[0188] <Preparation of Separator>

[0189] A ceramic coating slurry is coated on one surface of an isolation membrane substrate, and after drying at 60°C, a ceramic coating is formed on one surface of the isolation membrane substrate; a first bonding coating slurry is coated on the surface of the ceramic coating away from the isolation membrane substrate, and after drying at 60°C, a first bonding coating is formed on the surface of the ceramic coating away from the isolation membrane substrate; the first bonding coating slurry is coated on the other surface of the isolation membrane substrate, and after drying at 60°C, a first bonding coating is formed on the other surface of the isolation membrane substrate, thereby producing an isolation membrane.

[0190] The rest is the same as Example 1-1.

[0191] <Preparation of lithium-ion batteries>

[0192] Except that the surface of the separator provided with the ceramic coating is closer to the positive electrode sheet, the rest is the same as Example 1-1.

[0193] <Preparation of positive electrode sheet>, <Preparation of negative electrode sheet>, and <Preparation of electrolyte solution> are the same as those in Example 1-1.

[0194] Comparative Example 11

[0195] <Preparation of Separator>

[0196] A ceramic coating slurry is coated on one surface of an isolation membrane substrate, and after drying at 60°C, a ceramic coating is formed on one surface of the isolation membrane substrate; a second bonding coating slurry is coated on the surface of the ceramic coating away from the isolation membrane substrate, and after drying at 60°C, a second bonding coating is formed on the surface of the ceramic coating away from the isolation membrane substrate; a second bonding coating slurry is coated on the other surface of the isolation membrane substrate, and after drying at 60°C, a second bonding coating is formed on the other surface of the isolation membrane substrate, thereby producing an isolation membrane.

[0197] The rest is the same as Example 1-1.

[0198] <Preparation of positive electrode sheet>, <Preparation of negative electrode sheet>, <Preparation of electrolyte>, and <Preparation of lithium-ion battery> are the same as those in Comparative Example 10. The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 5.

[0199] Table 1

[0200]

[0201]

[0202] Note: “\” in Table 1 indicates no corresponding parameter; the difference between Example 1-1 and Example 1-24 in Table 1 is that in the lithium-ion battery of Example 1-1, the first bonding coating in the separator is close to the negative electrode sheet, and the second bonding coating is close to the positive electrode sheet, while in the lithium-ion battery of Example 1-24, the first bonding coating in the separator is close to the positive electrode sheet, and the second bonding coating is close to the negative electrode sheet.

[0203] Table 2

[0204]

[0205]

[0206] It can be seen from Examples 1-1 to 1-24 and Comparative Examples 1 to 11 that the electrochemical device of the embodiment of the present application is provided with a first bonding coating and a second bonding coating on both sides of the separator, and the average particle size of the first polymer binder in the first bonding coating and the average particle size of the second polymer binder in the second bonding coating are within the scope of the present application, and the Dv99 of the positive electrode active material and the Dv99 of the negative electrode active material are within the scope of the present application, and the positive electrode current collector is provided to extend integrally to form a plurality of positive electrode ears, and the negative electrode current collector is provided to extend integrally to form a plurality of negative electrode ears. The tabs make the electrochemical device have a multi-tab structure, so that the separator has a higher bonding force F1 to the positive electrode sheet and the separator has a higher bonding force F2 to the negative electrode sheet. The electrochemical device has a shorter 10C charging time (that is, a higher 10C charging speed), a lower 10C charging temperature rise, and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle dynamics performance under super-fast charging conditions. The electrochemical device has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high-temperature stability. This shows that the electrochemical device of the embodiment of the present application can take into account high-temperature stability on the basis of having good cycle dynamics performance under super-fast charging conditions, that is, the electrochemical device has better comprehensive performance under super-fast charging conditions. The electrochemical device of Comparative Example 1 has an embedded single-pole ear structure rather than the multi-pole ear structure of the present application; the electrochemical devices of Comparative Examples 2 and 3, the average particle size of the second polymer binder in their isolation membranes is not within the scope of the present application; the electrochemical devices of Comparative Examples 4 and 5, the average particle size of the first polymer binder in their isolation membranes is not within the scope of the present application; the electrochemical devices of Comparative Examples 6 and 7, the Dv99 of their negative electrode active materials are not within the scope of the present application; the electrochemical devices of Comparative Examples 8 and 9, the Dv99 of their positive electrode active materials are not within the scope of the present application; the electrochemical device of Comparative Example 10, both sides of its isolation membrane are set as a first bonding coating, rather than the isolation membrane structure of the present application; the electrochemical device of Comparative Example 11, both sides of its isolation membrane are set as a second bonding coating, rather than the isolation membrane structure of the present application. In the electrochemical devices of Comparative Examples 1 to 11, the electrochemical device has a longer 10C charging time (i.e., a lower 10C charging speed) and / or a higher 10C charging temperature rise and / or a lower 25°C 1000cls capacity retention rate, or the electrochemical device has a higher 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device cannot take into account the 10C charging time, 10C charging temperature rise, 25°C 1000cls capacity retention rate, and 80°C storage expansion rate under super-fast charging conditions, that is, the electrochemical device cannot take into account both the cycle dynamics performance and the high temperature stability under super-fast charging conditions.

[0207] The Dv99 of the positive electrode active material usually affects the cycle kinetics and high temperature stability of the electrochemical device. From Example 1-1 to Example 1-5, Comparative Example 8 and Comparative Example 9, it can be seen that the electrochemical device using the Dv99 positive electrode active material within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise, and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle kinetics under super-fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability while having good cycle kinetics under super-fast charging conditions. Among them, compared with Example 1-2 and Example 1-5, the Dv99 of the positive electrode active material in Example 1-1, Example 1-3 and Example 1-4 is in the preferred range of 28μm to 31μm. While having a shorter 10C charging time, a lower 10C charging temperature rise and a lower 80℃ storage expansion rate, it has a higher 25℃1000cls capacity retention rate, indicating that the electrochemical device in which the positive electrode active material Dv99 is in the preferred range of 28μm to 31μm has better cycle dynamics performance while having good high temperature stability under superfast charging conditions.

[0208] The Dv99 of the negative electrode active material usually affects the cycle kinetics and high temperature stability of the electrochemical device. It can be seen from Example 1-1, Example 1-6 to Example 1-9, Comparative Example 6 and Comparative Example 7 that the electrochemical device using the Dv99 negative electrode active material within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle kinetics under super fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability on the basis of good cycle kinetics under super fast charging conditions. Among them, compared with Example 1-6 and Example 1-9, the Dv99 of the negative electrode active material in Example 1-1, Example 1-7 and Example 1-8 is in the preferred range of 24μm to 26μm. While having a shorter 10C charging time, a lower 10C charging temperature rise and a lower 80℃ storage expansion rate, it has a higher 25℃1000cls capacity retention rate, indicating that the electrochemical device in which the negative electrode active material Dv99 is in the preferred range of 24μm to 26μm has better cycle dynamics performance while having good high temperature stability under super fast charging conditions.

[0209] The average particle size of the first polymer binder usually affects the cycle dynamics and high temperature stability of the electrochemical device. It can be seen from Example 1-1, Example 1-10 to Example 1-13, Comparative Example 4 and Comparative Example 5 that the electrochemical device in which the average particle size of the first polymer binder is within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle dynamics under super fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability on the basis of having good cycle dynamics under super fast charging conditions. Among them, compared with Example 1-10 and Example 1-13, the average particle size of the first polymer binder in Example 1-1, Example 1-11 and Example 1-12 is in the preferred range of 0.6μm to 1.6μm, and it has a shorter 10C charging time, a lower 10C charging temperature rise and a lower 80℃ storage expansion rate. At the same time, it has a higher 25℃1000cls capacity retention rate, indicating that the electrochemical device with the average particle size of the first polymer binder in the preferred range of 0.6μm to 1.6μm has better cycling dynamics performance while having good high temperature stability under superfast charging conditions.

[0210] The average particle size of the second polymer binder usually affects the cycle dynamics and high temperature stability of the electrochemical device. It can be seen from Example 1-1, Example 1-14 to Example 1-17, Comparative Example 2 and Comparative Example 3 that the electrochemical device in which the average particle size of the second polymer binder is within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle dynamics under super fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability on the basis of having good cycle dynamics under super fast charging conditions. Among them, compared with Example 1-14 and Example 1-17, the average particle size of the second polymer binder in Example 1-1, Example 1-15 and Example 1-16 is in the preferred range of 8μm to 12μm. It has a shorter 10C charging time, a lower 10C charging temperature rise and a lower 80°C storage expansion rate, while having a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device with the average particle size of the second polymer binder in the preferred range of 8μm to 12μm has better cycling dynamics performance while having good high temperature stability under super fast charging conditions.

[0211] The values ​​of N1 and N2 generally affect the cycling kinetics and high-temperature stability of electrochemical devices. Examples 1-1, 1-18, and 1-19 show that increasing N1 and N2 increases the 10C charge time, 10C charge temperature rise, and 80°C storage expansion rate of the electrochemical device, while decreasing the 25°C 1000cls capacity retention rate. However, the number of tabs decreases with increasing N1 and N2. Therefore, the energy density of Examples 1-18 and 1-19 is higher than that of Example 1-1.

[0212] The Dv50 of the positive electrode active material usually affects the cycle kinetics and high temperature stability of the electrochemical device. It can be seen from Examples 1-1 to 1-5, and 1-20 to 1-21 that the electrochemical device whose Dv50 of the positive electrode active material is within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise, and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle kinetics under super-fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability on the basis of good cycle kinetics under super-fast charging conditions.

[0213] The Dv50 of the negative electrode active material usually affects the cycle kinetics and high temperature stability of the electrochemical device. It can be seen from Example 1-1, Example 1-6 to Example 1-9, Example 1-22 to Example 1-23 that the electrochemical device whose Dv50 of the negative electrode active material is within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle kinetics under super fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability on the basis of having good cycle kinetics under super fast charging conditions.

[0214] The positional relationship between the first and second bonding coatings in the separator and the positive and negative electrode sheets typically affects the cycling kinetics and high-temperature stability of the electrochemical device. As can be seen from Examples 1-1 and 1-24, the poor adhesion between the second polymer binder, polyvinylidene fluoride, and the negative electrode sheet results in a low bonding force F2 between the separator and the negative electrode sheet, resulting in poor high-temperature stability for the electrochemical device of Example 1-24 relative to that of Example 1-1. Furthermore, because the second bonding coating in Example 1-24 corresponds to the negative electrode sheet, the lithium ion transmission path is longer during super-fast charging, resulting in a slightly longer charging time for Example 1-24 compared to Example 1-1.

[0215] Table 3

[0216]

[0217] Table 4

[0218]

[0219]

[0220] The coverage rate Cr1, single-sided coating weight Cw1, and thickness H1 of the first polymer binder per unit area in the first bonding coat generally affect the cyclic kinetics and high-temperature stability of the electrochemical device. As can be seen from Examples 1-1, 2-1, and 2-6, the electrochemical device selected for the coverage rate Cr1, single-sided coating weight Cw1, and thickness H1 of the first polymer binder per unit area in the first bonding coat within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise, and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cyclic kinetics under super-fast charging conditions. The electrochemical device has a lower 80°C storage expansion rate after being stored at 80°C for 8 hours, indicating that the electrochemical device has good high-temperature stability. As a result, the electrochemical device can achieve both good cyclic kinetics and high-temperature stability under super-fast charging conditions.

[0221] The coverage rate Cr2, single-sided coating weight Cw2, and thickness H2 of the second polymer binder per unit area in the second bonding coat generally affect the cyclic kinetics and high-temperature stability of the electrochemical device. As can be seen from Examples 1-1, 2-7, and 2-12, the electrochemical device selected for the coverage rate Cr2, single-sided coating weight Cw2, and thickness H2 of the second polymer binder per unit area in the second bonding coat within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise, and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cyclic kinetics under super-fast charging conditions. After being stored at 80°C for 8 hours, it has a lower 80°C storage expansion rate, indicating that the electrochemical device has good high-temperature stability. As a result, the electrochemical device can achieve good cyclic kinetics under super-fast charging conditions while taking into account high-temperature stability.

[0222] The type of the first polymer binder usually affects the cycle kinetics and high temperature stability of the electrochemical device. It can be seen from Example 1-1, Example 2-13, and Example 2-14 that the electrochemical device in which the type of the first polymer binder is selected is within the scope of this application, which has a shorter 10C charging time, a lower 10C charging temperature rise, and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle kinetics under super-fast charging conditions, and has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability on the basis of having good cycle kinetics under super-fast charging conditions.

[0223] The type of the second polymer binder usually affects the cycle kinetics and high temperature stability of the electrochemical device. It can be seen from Example 1-1, Example 2-15, and Example 2-16 that the electrochemical device using the type of the second polymer binder within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise, and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle kinetics under super-fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability while having good cycle kinetics under super-fast charging conditions.

[0224] Table 5

[0225]

[0226] Note: “\” in Table 5 indicates no corresponding parameter; “Mr” in Table 5 indicates the mass ratio of artificial graphite to amorphous carbon.

[0227] Types of negative electrode active materials, carbon-based materials d / I g The value usually affects the cycle kinetics and high temperature stability of the electrochemical device. It can be seen from Examples 1-1, 3-1 and 3-4 that the type of negative electrode active material, the I of the carbon-based material d / I g The electrochemical device with a value within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise, and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle dynamics performance under super fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. Therefore, the electrochemical device can have good cycle dynamics performance under super fast charging conditions while taking into account high temperature stability. Among them, Figure 10 The Raman spectrum of Example 3-3 is shown. Figure 10 It can be seen that in the Raman spectrum of the high-kinetic negative electrode active material, its I d / I g A higher value indicates that it has good surface activity.

[0228] The type of positive electrode active material usually affects the cycle kinetics and high temperature stability of the electrochemical device. It can be seen from Examples 1-1, 3-5 and 3-6 that the electrochemical device whose type of positive electrode active material is within the scope of this application has a shorter 10C charging time, a lower 10C charging temperature rise and a higher 25°C 1000cls capacity retention rate, indicating that the electrochemical device has good cycle kinetics under super fast charging conditions. It has a lower 80°C storage expansion rate after being stored at 80°C for 8h, indicating that the electrochemical device has good high temperature stability. As a result, the electrochemical device can take into account high temperature stability on the basis of good cycle kinetics under super fast charging conditions.

[0229] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0230] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0231] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An electrochemical device comprising an electrode assembly, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator, the positive electrode sheet comprising a positive electrode active material, the negative electrode sheet comprising a negative electrode active material, the Dv99 of the positive electrode active material being 27 μm to 33 μm, and the Dv99 of the negative electrode active material being 23 μm to 28 μm; The positive electrode plate includes a positive electrode current collector, and the positive electrode current collector is integrally extended to form a plurality of positive electrode tabs; the negative electrode plate includes a negative electrode current collector, and the negative electrode current collector is integrally extended to form a plurality of negative electrode tabs; The isolation film includes an isolation film substrate, a first bonding coating layer and a second bonding coating layer, wherein the first bonding coating layer and the second bonding coating layer are respectively arranged on both sides of the isolation film substrate; the first bonding coating layer includes a first polymer binder, and the average particle size of the first polymer binder is 0.3 μm to 3 μm; the second bonding coating layer includes a second polymer binder, and the average particle size of the second polymer binder is 10 μm to 38 μm.

2. The electrochemical device according to claim 1, wherein The first bonding coating is disposed on a side of the separator substrate close to the negative electrode plate, and the second bonding coating is disposed on a side of the separator substrate close to the positive electrode plate.

3. The electrochemical device according to claim 1, wherein An N1 layer of positive electrode sheet is provided between two adjacent positive electrode tabs, and an N2 layer of negative electrode sheet is provided between two adjacent negative electrode tabs. N1 and N2 are independently selected from 0, 1, 2 or 3.

4. The electrochemical device according to claim 1, wherein The Dv99 of the positive electrode active material is 28 μm to 31 μm, and / or the Dv99 of the negative electrode active material is 24 μm to 26 μm.

5. The electrochemical device according to claim 1, wherein The Dv50 of the positive electrode active material is 10 μm to 15 μm, and / or the Dv50 of the negative electrode active material is 7 μm to 12 μm.

6. The electrochemical device according to claim 1, wherein The Dv50 of the positive electrode active material is 11 μm to 13 μm, and / or the Dv50 of the negative electrode active material is 8 μm to 11 μm.

7. The electrochemical device according to claim 1, wherein The average particle size of the first polymer binder is 0.6 μm to 1.6 μm, and / or the average particle size of the second polymer binder is 20 μm to 30 μm.

8. The electrochemical device according to claim 1, wherein The thickness of the first bonding coating layer is 0.2 μm to 4 μm, and the thickness of the second bonding coating layer is 5 μm to 20 μm.

9. The electrochemical device according to claim 1, wherein The single-sided coating weight of the first bonding coating is 0.0001 mg / mm 2 to 0.001 mg / mm 2 The single-sided coating weight of the second bonding coating is 0.0004 mg / mm 2 to 0.002 mg / mm 2 .

10. The electrochemical device according to claim 1, wherein The coverage rate of the first polymer binder per unit area in the first bonding coating layer is 40% to 60%.

11. The electrochemical device according to claim 1, wherein The first polymer binder includes a core-shell structure first polymer binder or a non-core-shell structure first polymer binder, the core of the core-shell structure first polymer binder includes at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid or maleic acid, the shell of the core-shell structure first polymer binder includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene, ethyl chloromethylacrylate, chlorostyrene, fluorostyrene, methylstyrene, acrylonitrile or methacrylonitrile; the non-core-shell structure first polymer binder includes at least one of acrylic acid, methyl acrylate, butyl acrylate, butadiene, styrene, acrylonitrile, ethylene, fluorostyrene, chlorostyrene or propylene.

12. The electrochemical device according to claim 1, wherein The coverage rate of the second polymer binder per unit area in the second bonding coating layer is 40% to 60%.

13. The electrochemical device according to claim 1, wherein The polymerization monomer of the second polymer binder includes at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, allyl chloride, acrylic acid, methyl acrylate, butyl acrylate, chlorostyrene, fluorostyrene, ethyl acrylate, ethyl methacrylate, methyl methacrylate, butyl methacrylate, ethyl chloromethylacrylate, styrene, butadiene or acrylonitrile.

14. The electrochemical device according to claim 1, wherein The second polymer binder includes a core-shell structure second polymer binder or a non-core-shell structure second polymer binder, the polymerization monomer of the shell of the core-shell structure second polymer binder includes at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, styrene, butadiene, acrylonitrile, acrylic acid, methyl acrylate or butyl acrylate, and the polymerization monomer of the core of the core-shell structure second polymer binder includes at least one of ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate or ethyl chloromethylacrylate; the polymerization monomer of the non-core-shell structure second polymer binder includes at least one of acrylic acid, methyl acrylate, butyl acrylate, butadiene, styrene, acrylonitrile, ethylene, propylene, chlorostyrene, fluorostyrene, vinylidene chloride, vinylidene fluoride, hexafluoropropylene, vinyl chloride or allyl chloride.

15. The electrochemical device according to claim 1, wherein The positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate or lithium titanate.

16. The electrochemical device according to claim 1, wherein The positive electrode active material includes a non-metallic element, and the non-metallic element includes at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur.

17. The electrochemical device according to claim 1, wherein The negative electrode active material includes at least one of a carbon-based material, a silicon-based material or a tin-based material, the carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon or mesophase carbon microbeads, the silicon-based material includes at least one of a silicon material, a silicon-carbon material or a silicon-oxygen material, and the tin-based material includes at least one of elemental tin, a tin alloy or a tin oxide.

18. The electrochemical device according to claim 17, wherein The carbon-based material is tested by Raman with a peak intensity ratio of d peak to g peak I d / I g Satisfy: 0.1≤I d / I g ≤1.

19. An electronic device comprising the electrochemical device according to any one of claims 1 to 18.

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