Fast-charging secondary battery and electrical apparatus

Abstract

A fast-charging secondary battery and an electrical apparatus. The fast-charging secondary battery comprises an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate comprises a positive electrode current collector, and the positive electrode current collector integrally extends to form multiple positive electrode lugs. The negative electrode plate comprises a negative electrode current collector, and the negative electrode current collector integrally extends to form multiple negative electrode lugs. The separator comprises a separator base material, a first bonding coating and a second bonding coating, the first bonding coating and the second bonding coating being disposed on the two sides of the separator base material. The first bonding coating comprises a first polymer binder, and the first polymer binder has an average particle size of 0.3 μm to 3 μm. The second bonding coating comprises a second polymer binder, and the second polymer binder has an average particle size of 4 μm to 15 μm. The fast-charging secondary battery can balance dynamic performance, cycle performance, and mechanical reliability.

Description

Fast-charging secondary battery and power-consuming device Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a fast-charging secondary battery and an electrical device. Background Art

[0002] Secondary batteries (such as 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 increasingly higher requirements for their charging speed. The charging rate of lithium-ion batteries has continued to increase, and consumer demand has gradually increased from 1C to 5C or above. However, it is difficult to balance the dynamic performance, cycle performance and mechanical reliability of fast-charging (5C≤charging rate≤15C) lithium-ion batteries. Therefore, how to balance the dynamic performance, cycle performance and mechanical reliability of super-fast charging lithium-ion batteries has become a technical problem that needs to be solved urgently by those skilled in the art.

[0003] Summary of the Invention

[0004] The purpose of the present application is to provide a fast-charging secondary battery that takes into account the dynamic performance, cycle performance and mechanical reliability of the fast-charging secondary battery, and at the same time provides an electrical device using the fast-charging secondary battery.

[0005] It should be noted that in the invention content of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries of this application are not limited to lithium-ion batteries, and can also be applied to secondary batteries such as sodium-ion batteries.

[0006] The specific technical solutions are as follows:

[0007] The first aspect of the present application provides a fast-charging secondary battery, wherein the fast-charging secondary battery includes an electrode assembly and an electrolyte, the electrode assembly includes a positive electrode plate, a negative electrode plate and a separator arranged between the positive electrode plate and the negative electrode plate; 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 contains a first polymer binder, and the average particle size of the first polymer binder is 0.3μm to 3μm; the second bonding coating contains a second polymer binder, and the average particle size of the second polymer binder is 4μm to 15μm.

[0008] This application provides a multi-electrode structure for the secondary battery by providing a plurality of positive electrode tabs formed by integrally extending the positive electrode current collector and a plurality of negative electrode tabs formed by integrally extending the negative electrode current collector. The positive electrode tab and the negative electrode tab have multiple current channels, thereby reducing the internal resistance of the secondary battery, minimizing the voltage polarization of the secondary battery under high-rate charging conditions, reducing the charging temperature rise of the secondary battery, and shortening the charging time of the secondary battery, thereby providing the secondary battery with higher dynamic performance. In order to adapt to the dynamic requirements of fast-charging secondary batteries, a large amount of electrolyte is added to the secondary battery, i.e., a large amount of liquid is retained (free electrolyte exists in fresh secondary batteries), which places high requirements on the infiltration fluidity of the electrolyte. The connection strength between the multiple pole ears extending from the current collector and the current collector is much lower than the connection method of welding the external pole ears to the current collector in the prior art. At the same time, the pole ears extending integrally with the current collector are usually obtained by die-cutting. During the die-cutting process, burrs, microcracks and other defects are easily generated on the edges of the pole ears, further reducing the strength of the integrally extended pole ears. The above reasons lead to the low strength and easy fracture of the multi-pole ear structure extending from the current collector. The high liquid retention design of the fast-charging secondary battery will cause the free electrolyte to move under the action of external forces such as falling and vibration, impacting the multi-pole ear structure of the fast-charging secondary battery, increasing the risk of pole ear fracture, and thereby increasing the internal resistance of the fast-charging secondary battery or affecting the mechanical reliability of the fast-charging secondary battery. A first bonding coating and a second bonding coating are respectively provided on both sides of the isolation membrane of the fast-charging secondary battery, 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. One side of the isolation membrane has high bonding force, which can strengthen the bonding force between the isolation membrane and the positive / negative electrode sheets, improve the hardness of the fast-charging secondary battery, and thus improve the mechanical reliability of the fast-charging secondary battery. At the same time, the high bonding force of the isolation membrane can also reduce the relative movement of the electrodes caused by external mechanical forces, alleviate the impact, and reduce the fracture rate of the positive / negative electrode ears, thereby further improving the mechanical reliability of the fast-charging secondary battery and reducing the internal resistance of the fast-charging secondary battery. In addition, the other side of the isolation membrane has a second adhesive coating, and the gap between the negative / positive electrode sheet is increased, so that the transmission channel of the electrolyte is expanded, the space for storing the electrolyte becomes larger, and the fast-charged secondary battery can have a high liquid retention (such as 1.5g / Ah to 2.4g / Ah), so that the head, tail and middle parts of the fast-charged secondary battery have sufficient electrolyte during the cycle, which can provide sufficient ion channels, thereby meeting the cycle requirements of the fast-charged secondary battery and making the fast-charged secondary battery have good cycle performance. Therefore, the isolation membrane of the present application has a good synergistic effect with the multi-electrode structure, which can take into account the dynamic performance, cycle performance and mechanical reliability of the fast-charged secondary battery.

[0009] In one embodiment 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 range, 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 fast-charge secondary battery, thereby providing multiple current channels on the positive electrode tabs and negative electrode tabs, reducing the internal resistance of the secondary battery, reducing the charging temperature rise of the fast-charge secondary battery, and shortening the charging time, thereby achieving good dynamic performance while taking into account both cycle performance and mechanical reliability of the fast-charge secondary battery. 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 secondary battery, further reduce the charging temperature rise of the fast-charging secondary battery, and further shorten the charging time, thereby further improving the dynamic performance of the fast-charging secondary battery while taking into account both cycle performance and mechanical reliability. However, this will reduce the energy density of the secondary battery to a certain extent; adjusting N1 and N2 to 1 or 2 or 3 will reduce the number of tabs and increase the internal resistance to a certain extent, but it can increase the battery energy density.

[0010] In one embodiment of the present application, the first adhesive coating is disposed on the side of the separator substrate close to the negative electrode plate, and the second adhesive coating is disposed on the side of the separator substrate close to the positive electrode plate. For most secondary batteries, 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 secondary battery charging process mainly involves the insertion of lithium ions into the negative electrode. Therefore, placing a high-viscosity coating with smaller separator particles on the negative electrode plate can shorten the lithium ion transmission path during the charging process and achieve faster charging speed.

[0011] In one embodiment 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 8 μm to 12 μm. Regulating the average particle size of the first polymer binder within the above range is beneficial to further improving the kinetic performance and mechanical reliability of the fast-charged secondary battery while taking into account the cycle 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 kinetic performance and mechanical reliability of the fast-charged secondary battery while taking into account the mechanical reliability, and also allowing the fast-charged secondary battery to have a higher energy density.

[0012] In one embodiment of the present application, the thickness of the first bonding coating is 0.2 μm to 4 μm, and the thickness of the second bonding coating is 5 μm to 20 μm. The high-viscosity coating 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. The second bonding coating 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 the flow and wettability of the electrolyte.

[0013] In one embodiment 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 Regulating the single-sided coating weight of the first bonding coating within the above range can fully utilize the high bonding properties of the first bonding coating, better bond the pole piece and the separator, and ensure the mechanical reliability of the secondary battery; regulating the single-sided coating weight of the second bonding coating within the above range can fully realize the electrolyte flow channel between the pole piece and the separator, and improve the dynamics and cycle performance of the secondary battery.

[0014] In one embodiment of the present application, the coverage of the first polymer binder per unit area of ​​the first bonding coat layer is 40% to 60%. By regulating the coverage of the first polymer binder per unit area of ​​the first bonding coat layer within the above range, the high bonding properties of the first bonding coat layer can be fully utilized. This facilitates bonding between the separator and the electrode, allowing for faster lithium ion transmission, thereby further improving the dynamic performance of the secondary battery.

[0015] In one embodiment of the present application, the first polymer binder is a core-shell structure, the first polymer binder includes a first shell and a first core, the polymerization monomer of the first shell 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, and the polymerization monomer of the first core includes at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid or maleic acid; or, the first polymer binder is a non-core-shell structure, and the polymerization monomer of the 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.

[0016] In one embodiment of the present application, the coverage of the second polymer binder per unit area of ​​the second bonding coating layer is 40% to 60%. By regulating the coverage of the second polymer binder per unit area of ​​the second bonding coating layer within the above range, the separator and the electrode have strong adhesion, resulting in a secondary battery with a higher energy density. This allows the fast-charging secondary battery to have a low production cost and a high energy density while taking into account dynamic performance, cycle performance, and mechanical reliability.

[0017] In one embodiment of the present application, the second polymer binder has a core-shell structure, comprising a second outer shell and a second inner core, wherein the polymerized monomers of the second outer shell include at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, styrene, butadiene, acrylonitrile, acrylic acid, methyl acrylate, or butyl acrylate, and the polymerized monomers of the second inner core include at least one of ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, or ethyl chloromethylacrylate; alternatively, the second polymer binder has a non-core-shell structure, wherein the polymerized monomers of the second polymer binder include at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, allyl chloride, acrylic acid, methyl acrylate, butyl acrylate, styrene, butadiene, or acrylonitrile. The use of the above-mentioned second polymer binder can provide a large gap between the second bonding coating and the positive / negative electrode sheets.

[0018] In one embodiment of the present application, the separator further includes a ceramic coating, which is disposed between the separator substrate and the first bonding coating, and / or between the separator substrate and the second bonding coating. The ceramic coating includes ceramic particles, and the average particle size of the ceramic particles is 1 μm to 3 μm. The ceramic coating has good hardness and heat resistance. By disposing the ceramic coating in the separator and regulating the average particle size of the ceramic particles in the ceramic coating within the above range, the fast-charge secondary battery can further improve its mechanical reliability while having good thermal safety performance. Furthermore, the fast-charge secondary battery has good dynamic performance and cycle performance.

[0019] In one embodiment of the present application, the ceramic particles include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium hydroxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride or silicon nitride.

[0020] In one embodiment of the present application, the thickness of the ceramic coating is 0.5 μm to 6 μm. Controlling the thickness of the ceramic coating within this range is beneficial for ensuring that the fast-charging secondary battery has good thermal safety and energy density while taking into account dynamic performance, cycle performance, and mechanical reliability.

[0021] The second aspect of the present application provides an electrical device comprising the fast-charging secondary battery described in any of the aforementioned embodiments.

[0022] Beneficial effects of this application:

[0023] The present application provides a fast-charging secondary battery and an electrical device, wherein the fast-charging secondary battery is designed with a high liquid retention capacity. By providing a multi-pole structure, and providing a first bonding coating and a second bonding coating on both sides of the isolation membrane substrate, and limiting the particle size range of the first polymer binder in the first bonding coating and the second polymer binder in the second bonding coating, the fast-charging secondary battery has a high liquid retention capacity. The multi-pole structure and the isolation membrane play a good synergistic role, and on the basis of achieving the fast charging performance of the secondary battery, the mechanical reliability of the secondary battery is improved, that is, the dynamic performance, cycle performance and mechanical reliability of the fast-charging secondary battery are taken into account. The electrical device of the present application has good performance in use. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] FIG1 is a schematic structural diagram of an electrode assembly according to an embodiment of the present application;

[0026] FIG2 is a schematic structural diagram of an electrode assembly according to another embodiment of the present application;

[0027] FIG3 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present application;

[0028] FIG4 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present application;

[0029] FIG5 is a schematic diagram showing the positional relationship between the separator and the positive electrode sheet and the negative electrode sheet according to an embodiment of the present application;

[0030] FIG6 is a schematic diagram showing the positional relationship between the separator and the positive electrode sheet and the negative electrode sheet according to another embodiment of the present application;

[0031] FIG7 is a schematic diagram of a cross-sectional structure of an isolation membrane along its thickness direction according to an embodiment of the present application;

[0032] FIG8 is a schematic diagram of a cross-sectional structure of an isolation membrane along its thickness direction according to another embodiment of the present application;

[0033] FIG9 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. DETAILED DESCRIPTION

[0034] 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.

[0035] Fast-charged secondary batteries require that the impedance of the battery system is very low in order to meet the requirements of high-rate (5C ≤ charging rate ≤ 15C) charging and the cycle performance of fast-charged secondary batteries. The embedded single-pole ear structure used in existing secondary batteries leads to crowding of the current channels in the positive electrode plate or the negative electrode plate, which increases the ohmic impedance of the secondary battery. When the secondary battery is charged at a high rate, the charging temperature rises, the charging speed is low, and it has poor kinetic performance. In addition, the liquid retention capacity of existing secondary batteries is low. As the cycle proceeds, the electrolyte is gradually consumed and the number of ion channels gradually decreases. When the number of ion channels is reduced to a level that cannot meet the transmission requirements of the secondary battery cycle, the positive and negative electrode plates begin to fail due to local lithium deintercalation, and the failure area expands as the cycle continues, causing the secondary battery cycle to decay rapidly and fail. Based on this, the present application provides a fast-charged secondary battery and an electrical device.

[0036] The first aspect of the present application provides a fast-charging secondary battery, wherein the fast-charging secondary battery includes an electrode assembly and an electrolyte, the electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator arranged between the positive electrode plate and the negative electrode plate; the positive electrode plate includes a positive electrode current collector, and the positive electrode current collector extends as a whole to form a plurality of positive electrode tabs; the negative electrode plate includes a negative electrode current collector, and the negative electrode current 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 comprises 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 comprises a second polymer binder, and the average particle size of the second polymer binder is 4 μm to 15 μm.

[0037] In this application, for ease of understanding, the separator 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 length direction, width direction, and thickness direction of the positive and negative electrode sheets in the unfolded state are the same as those of the separator. After the positive electrode sheet, separator, and negative electrode sheet are wound to form an electrode assembly with a wound structure, the winding direction of the electrode assembly is W. As shown in Figures 1 and 2, the electrode assembly 001 includes a positive electrode sheet 10, a negative electrode sheet 20, and a separator 30, with the separator 30 being disposed between the positive electrode sheet 10 and the negative electrode sheet 20. As shown in FIG3 , the positive electrode sheet 10 includes a positive electrode current collector 11, which extends integrally to form a plurality of positive electrode tabs 12. The positive electrode current collector 11 includes a positive electrode tab region 111 and a positive electrode main body region 112. It is understood that the positive electrode tab region 111 is the region where the positive electrode tabs 12 are provided, and the positive electrode main body region 112 refers to the region of the positive electrode current collector 11 excluding the positive electrode tab region 111. As shown in FIG4 , the negative electrode sheet 20 includes a negative electrode current collector 21, which extends integrally to form a plurality of negative electrode tabs 22. The negative electrode current collector 21 includes a negative electrode tab region 211 and a negative electrode main body region 212. It is understood that the negative electrode tab region 211 refers to the region where the negative electrode tabs 22 are provided, and the negative electrode main body region 212 refers to the region of the negative electrode current collector 21 excluding the negative electrode tab region 211. In the present application, the above-mentioned "integrated extension" refers to the integral molding of the current collector and the tabs. For example, multiple 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 the number, shape and size of the positive and negative tabs in Figures 1 to 4 are only exemplary illustrations, and this application is not limited to this. As shown in Figures 5 and 6, 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 the negative electrode sheet 20 side. As shown in Figure 5, the first bonding coating 32 is arranged on the side of the separator substrate 31 close to the negative electrode sheet 20, and the second bonding coating 33 is arranged on the side of the separator substrate 31 close to the positive electrode sheet 10. As shown in Figure 6, the first bonding coating 32 is provided on the side of the separator substrate 31 close to the positive electrode sheet 10, and the second bonding coating 33 is provided on the side of the separator substrate 31 close to the negative electrode sheet 20. In this application, the above-mentioned "plurality" refers to two or more. In one embodiment of the present application, a plurality refers to 2 to the same number as the number of electrode layers. For example, a plurality can be 2, 3, 4, 5, 6, 7, 10, 15, 20, 25, or 30.

[0038] 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 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 coating 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 coating slurry is extremely small, and the distribution of the first polymer binder in the first bonding coating formed is uneven, which will affect the cohesion of the first bonding coating. 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. The gap between each particle of the first polymer binder will be too large, thereby affecting the performance of the first polymer binder in the first bonding coating, and then affecting the cohesion of the first bonding coating, and the average particle size of the first polymer binder is too large to increase the thickness of the first bonding coating, thereby increasing the volume of the fast-charged secondary battery and thus causing its energy density to be lost.

[0039] For example, the average particle size of the second polymer binder is 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 15μm or any value between any two of the above numerical ranges. The average particle size of the second polymer binder is less than 4μm. If the average particle size of the second polymer binder is too small, the gap between the separator and the positive electrode or negative electrode is too small, and the transmission channel of the electrolyte is too narrow, which affects the transmission of the electrolyte and thus affects the cycle performance and dynamic performance of the fast-charge secondary battery. The average particle size of the second polymer binder is greater than 15μm. 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 fast-charge secondary battery and causing a loss in its energy density.

[0040] This application provides a multi-electrode structure for the secondary battery by providing a plurality of positive electrode tabs formed by integrally extending the positive electrode current collector and a plurality of negative electrode tabs formed by integrally extending the negative electrode current collector. The positive electrode tab and the negative electrode tab have multiple current channels, thereby reducing the internal resistance of the secondary battery. This reduces the voltage polarization of the fast-charging secondary battery under high-rate charging conditions, reduces the charging temperature rise of the secondary battery, and shortens the charging time of the secondary battery, thereby making the secondary battery have higher dynamic performance. In order to adapt to the dynamic requirements of the fast-charging secondary battery, a large amount of electrolyte is added to the secondary battery, that is, a large amount of liquid is retained (free electrolyte exists in the fresh secondary battery), which places higher requirements on the infiltration fluidity of the electrolyte. The connection strength between the multiple pole ears extending from the current collector and the current collector is much lower than the connection method of welding the external pole ears to the current collector in the prior art. At the same time, the pole ears extending integrally with the current collector are usually obtained by die-cutting. During the die-cutting process, burrs, microcracks and other defects are easily generated on the edges of the pole ears, further reducing the strength of the integrally extended pole ears. The above reasons lead to the low strength and easy fracture of the multi-pole ear structure extending from the current collector. The high liquid retention design of the fast-charging secondary battery will cause the free electrolyte to move under the action of external forces such as falling and vibration, impacting the multi-pole ear structure of the fast-charging secondary battery, increasing the risk of pole ear fracture, and thereby increasing the internal resistance of the fast-charging secondary battery or affecting the mechanical reliability of the fast-charging secondary battery. A first bonding coating and a second bonding coating are respectively provided on both sides of the isolation membrane of the fast-charging secondary battery, 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. One side of the isolation membrane has high bonding force, which can strengthen the bonding force between the isolation membrane and the electrode, improve the hardness of the fast-charging secondary battery, and thus improve the mechanical reliability of the fast-charging secondary battery. At the same time, the high bonding force of the isolation membrane can also reduce the relative movement of the electrode caused by external mechanical force, alleviate the impact, and reduce the fracture rate of the electrode ear, thereby further improving the mechanical reliability of the fast-charging secondary battery and reducing the internal resistance of the fast-charging secondary battery. In addition, the other side of the isolation membrane has a second adhesive coating, and the gap between the isolation membrane and the electrode is increased, so that the transmission channel of the electrolyte is expanded. In this way, the space for storing electrolyte becomes larger, and the fast-charged secondary battery can have a high liquid retention (such as 1.5g / Ah to 2.4g / Ah), so that the head, tail and middle parts of the fast-charged secondary battery have sufficient electrolyte during the cycle, which can provide sufficient ion channels, thereby meeting the cycle requirements of the fast-charged secondary battery and making the fast-charged secondary battery have good cycle performance. Therefore, the isolation membrane of the present application has a good synergistic effect with the multi-electrode structure, which can take into account the dynamic performance, cycle performance and mechanical reliability of the fast-charged secondary battery.

[0041] In one embodiment 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. As shown in FIG1 , in the wound electrode assembly, from top to bottom in the figure, 0 layers of positive electrode sheet 10 are provided between two adjacent positive electrode tabs 12, and 0 layers of negative electrode sheet 20 are provided between two adjacent negative electrode tabs 22. As shown in FIG2 , in the wound electrode assembly, from top to bottom in the figure, 1 layer of positive electrode sheet 10 and 2 layers of positive electrode sheet 10 are provided between two adjacent positive electrode tabs 12, respectively, and 0 layers of negative electrode sheet 20 and 3 layers of negative electrode sheet 20 are provided between two adjacent negative electrode tabs 22, respectively. By regulating N1 and N2 within the above range, the positive and negative electrode tabs in the fast-charged secondary battery can be provided with a sufficient number of positive and negative electrode tabs, thereby providing multiple current channels on the positive and negative electrode tabs, reducing the internal resistance of the secondary battery, reducing the charging temperature rise of the fast-charged secondary battery, and shortening the charging time, thereby achieving good dynamic performance while taking into account both the cycle performance and mechanical reliability of the fast-charged secondary battery. It is understandable that regulating N1 and N2 to 0 can provide more current channels on the positive and negative electrode tabs, further reducing the internal resistance of the secondary battery, further reducing the charging temperature rise of the fast-charged secondary battery, and further shortening the charging time, thereby achieving further improvement in the dynamic performance of the fast-charged secondary battery while taking into account both the cycle performance and mechanical reliability, but this will reduce the energy density of the secondary battery to a certain extent; adjusting N1 and N2 to 1, 2, or 3 will reduce the number of tabs, increase the internal resistance to a certain extent, but can increase the battery energy density.

[0042] In one embodiment 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. As shown in FIG1 , in the wound electrode assembly, from top to bottom in the figure, a 0 layer of positive electrode sheet 10 is provided between two adjacent positive electrode tabs 12, and a 0 layer of negative electrode sheet 20 is provided between two adjacent negative electrode tabs 22. By regulating N1 and N2 to 0, more positive electrode sheets and negative electrode sheets in the fast-charged secondary battery can be provided with positive electrode tabs and negative electrode tabs, thereby providing more current channels on the positive electrode sheets and negative electrode sheets, further reducing the internal resistance of the secondary battery, further reducing the charging temperature rise of the fast-charged secondary battery, and further shortening the charging time, thereby further improving the dynamic performance of the fast-charged secondary battery while taking into account both the cycle performance and mechanical reliability, but reducing the energy density to a certain extent.

[0043] In one embodiment of the present application, the first bonding coating is provided on the side of the separator substrate close to the negative electrode sheet, and the second bonding coating is provided on the side of the separator substrate close to the positive electrode sheet. As shown in FIG5 , 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. For most secondary batteries, 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 secondary batteries mainly involves the embedding of lithium ions into the negative electrode, so the high-viscosity coating with smaller separator particles is provided on the negative electrode sheet side, which can shorten the lithium ion transmission path during the charging process and achieve faster charging speed.

[0044] In one embodiment of the present application, the average particle size of the first polymer binder is 0.6 μm to 1.6 μm. In another embodiment of the present application, the average particle size of the second polymer binder is 8 μm to 12 μm. In yet another embodiment 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 8 μm to 12 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 8 μm, 9 μm, 10 μm, 11 μm, 12 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 is conducive to the uniform distribution of the first polymer binder in the first bonding coating, and there is a suitable gap between each particle of the first polymer binder, so that the high-binder coating has a stronger bonding force, and it is also conducive to regulating the thickness of the first bonding coating within a suitable range, so that the fast-charged secondary battery can further improve the dynamic performance and mechanical reliability of the fast-charged secondary battery while taking into account the cycle performance, and has a higher energy density. Regulating the average particle size of the second polymer binder within the above range, there is a suitable gap between the isolation membrane and the positive electrode sheet or the negative electrode sheet, which is conducive to the transmission of the electrolyte, and it is also conducive to regulating the thickness of the second bonding coating within a suitable range, so that the fast-charged secondary battery can further improve the cycle performance and dynamic performance of the fast-charged secondary battery while taking into account the mechanical reliability, and also makes the fast-charged secondary battery have a higher energy density.

[0045] The present application does not particularly limit the method for regulating the average particle size of the first polymer binder and the average particle size of the second polymer binder, as long as the purpose of the present application can be achieved. For example, this can be achieved by purchasing first and second polymer binders with average particle sizes within the range of the present application, or by grinding, screening, particle size distribution testing, etc. to obtain first and second polymer binders with corresponding average particle sizes.

[0046] In one embodiment of the present application, as shown in Figures 6 to 9, 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 fast-charged secondary battery due to excessive thickness while ensuring the bonding force of the first bonding coating, thereby improving the energy density of the fast-charged secondary battery and shortening the transmission path of lithium ions in the active material layer corresponding to the first bonding coating. Thus, the fast-charged secondary battery can take into account dynamic performance, cycle performance and mechanical reliability, and can also improve the energy density of the fast-charged secondary battery.

[0047] In one embodiment of the present application, as shown in Figures 6 to 9, 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, and a channel for electrolyte circulation can be formed. 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 fast-charged secondary battery due to the large thickness when the electrolyte has good flow wettability in the pole piece and the separator. In this way, the fast-charged secondary battery can take into account dynamic performance, cycle performance and mechanical reliability, and can also improve the energy density of the fast-charged secondary battery.

[0048] In one embodiment 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 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 properties to better bond the electrode and the separator. It can also reduce the risk of energy density loss caused by the increase in volume of the fast-charge secondary battery due to excessive single-sided coating weight. In this way, the fast-charge secondary battery can have good mechanical reliability and high energy density on the basis of having good dynamic performance and cycle performance.

[0049] In one embodiment of the present application, the single-sided coating weight 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 first bonding coating within the above range, the electrolyte flow channel between the electrode and the separator can be fully realized, thereby improving the dynamic performance and cycle performance of the secondary battery. It can also reduce the risk of energy density loss caused by the increase in volume of the fast-charged secondary battery due to excessive single-sided coating weight. In this way, the fast-charged secondary battery can have a higher energy density while taking into account dynamic performance, cycle performance and mechanical reliability.

[0050] In one embodiment of the present application, the coverage Cr1 of the first polymer binder in the first bonding coating per unit area is 40% to 60%. For example, the coverage of the first polymer binder in the first bonding coating per unit area 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 first polymer binder in the first bonding coating per unit area 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 separator and the pole piece, and the lithium ions have a faster transmission speed, thereby making the secondary battery have good dynamic performance.

[0051] In one embodiment of the present application, the first polymer binder is a core-shell structure, the first polymer binder includes a first shell and a first core, the polymerized monomer of the first shell 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, and the polymerized monomer of the first core includes at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid or maleic acid. The above-mentioned first polymer binder is applied to the first bonding coating to enable the first bonding coating to have high bonding strength.

[0052] In one embodiment of the present application, the first polymer binder has a non-core-shell structure, and the polymerized monomer of the 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.

[0053] In one embodiment 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 application 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%.

[0054] 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. Auxiliary binders include but are not limited to homopolymers or copolymers polymerized by at least one of the following monomers: ethyl acrylate, butyl acrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic anhydride, dicarboxylic anhydride, acrylonitrile, butadiene, and 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.

[0055] In one embodiment of the present application, the coverage Cr2 of the second polymer binder in the second bonding coating per unit area is 40% to 60%. For example, the coverage of the second polymer binder in the second bonding coating per unit area 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 in the second bonding coating per unit area within the above range, the electrolyte flow channel between the pole piece and the separator can be fully realized. When the electrolyte has good flow wettability in the pole piece and the separator, the second bonding coating has a suitable thickness, thereby reducing the risk of energy density loss caused by the increase in volume of the fast-charged secondary battery due to the excessive thickness. In this way, the fast-charged secondary battery can take into account dynamic performance, cycle performance and mechanical reliability, and can also improve the energy density of the fast-charged secondary battery.

[0056] In one embodiment of the present application, the second polymer binder has a core-shell structure, comprising a second outer shell and a second inner core. The monomers of the second outer shell 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 second inner core include at least one of ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, or ethyl chloromethylacrylate. The use of these second polymer binders allows for a large gap between the second bonding coating and the positive / negative electrode sheets.

[0057] In one embodiment of the present application, the second polymer binder has a non-core-shell structure, and the monomers of the second polymer binder include at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, allyl chloride, acrylic acid, methyl acrylate, butyl acrylate, styrene, butadiene, or acrylonitrile. The use of these second polymer binders allows for a large gap between the second bonding coating and the positive / negative electrode sheets.

[0058] In one embodiment of the present application, the second bonding coating includes a second polymer binder and an auxiliary binder. The auxiliary binder is applied to the second bonding coating, 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, as long as the purpose of the present application can be achieved. For example, based on the mass of the second bonding coating, the mass percentage of the second polymer binder is 85% to 95%, and the mass percentage of the auxiliary binder is 5% to 15%.

[0059] In one embodiment of the present application, the separator further comprises a ceramic coating, which is disposed between the separator substrate and the first bonding coating. As shown in FIG7 , the separator 30 comprises a separator 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 disposed on either side of the separator substrate 31, respectively. The ceramic coating 34 is disposed between the separator substrate 31 and the first bonding coating 32, and the second bonding coating 33 is adjacent to the surface of the separator substrate 31 away from the ceramic coating 34. The ceramic coating has excellent hardness and heat resistance. Disposing the ceramic coating between the separator and the first bonding coating can prevent the separator from shrinking at high temperatures, thereby improving the hardness and heat resistance of the secondary battery. This can further improve the mechanical reliability of the fast-charge secondary battery while maintaining good thermal safety performance. Furthermore, the fast-charge secondary battery has good dynamic performance and cycling performance. The ceramic coating 34 disposed between the separator substrate 31 and the first bonding coating 32 can also store a certain amount of electrolyte, providing additional electrolyte flow channels and improving the dynamic performance of the secondary battery.

[0060] In one embodiment of the present application, the isolation membrane further includes a ceramic coating, which is disposed between the isolation membrane substrate and the second bonding coating. As shown in FIG8 , the isolation membrane 30 includes an isolation membrane 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 disposed on both sides of the isolation membrane substrate 31, and the ceramic coating 34 is disposed between the isolation membrane substrate 31 and the second bonding coating 33. The first bonding coating 32 is adjacent to the surface of the isolation membrane substrate 31 away from the ceramic coating 34. The ceramic coating has good hardness and heat resistance. The ceramic coating is disposed between the isolation membrane substrate and the second bonding coating. The ceramic coating can prevent the isolation membrane from shrinking at high temperatures, thereby improving the hardness and heat resistance of the secondary battery, thereby further improving the mechanical reliability of the fast-charged secondary battery while ensuring good thermal safety performance. In addition, the fast-charged secondary battery has good dynamic performance and cycle performance. In the present application, it is preferred that the second bonding coating 33 faces the positive electrode plate, and the ceramic coating 34 is arranged between the isolation membrane substrate 21 and the second bonding coating 33 to store electrolyte. It can also provide additional electrolyte channels outside the electrolyte channels formed by the second bonding coating 33, which can reduce the thickness of the second bonding coating 33 and improve 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.

[0061] In one embodiment of the present application, the isolation membrane further includes a ceramic coating, which is disposed between the isolation membrane substrate and the first bonding coating, and the ceramic coating is also disposed between the isolation membrane substrate and the second bonding coating. As shown in FIG9 , the isolation membrane 30 includes an isolation membrane substrate 31, a first bonding coating 32, a second bonding coating 33, and two layers of ceramic coating 34. The first bonding coating 32 and the second bonding coating 33 are disposed on both sides of the isolation membrane substrate 31, respectively. One layer of ceramic coating 34 is disposed between the isolation membrane substrate 31 and the first bonding coating 32. At the same time, another layer of ceramic coating 34 is disposed between the isolation membrane substrate 31 and the second bonding coating 33. It should be noted that the above-mentioned two layers of ceramic coating can be the same or different. The ceramic coating has good hardness and heat resistance. Providing a ceramic coating in the isolation membrane can improve the hardness and heat resistance of the fast-charged secondary battery, thereby further improving its mechanical reliability while enabling the fast-charged secondary battery to have good thermal safety performance. In addition, the fast-charged secondary battery has good dynamic performance and cycle performance. Providing ceramic coatings 34 on both sides of the isolation membrane substrate 31 can simultaneously have the advantages of the above two ceramic coating 34 provision schemes, but will increase costs and reduce energy density.

[0062] In one embodiment of the present application, the ceramic coating includes ceramic particles, and the average particle size of the ceramic particles is 1 μm to 3 μm. For example, the average particle size of the ceramic particles is 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or any value between any two of the above numerical ranges. By regulating the average particle size of the ceramic particles within the above range, the risk of agglomeration of the ceramic particles in the ceramic coating is low, and while the ceramic coating exhibits heat resistance and high hardness, its thickness can be regulated within a suitable range, which is conducive to the fast-charging secondary battery having good thermal safety performance while taking into account dynamic performance, cycle performance, and mechanical reliability.

[0063] The present application does not particularly limit the method for controlling the average particle size of the ceramic particles, as long as the purpose of the present application can be achieved. For example, it can be achieved by mechanical crushing, grinding, etc., or it can be achieved by directly purchasing ceramic particles with an average particle size that meets the requirements of the present application.

[0064] In one embodiment of the present application, the ceramic particles include 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. By selecting these types of ceramic particles, the ceramic coating can have high hardness and good heat resistance.

[0065] In one embodiment of the present application, as shown in Figures 7 to 9, the thickness H3 of the ceramic coating 34 is 0.5μm to 6μm. For example, the thickness H3 of the ceramic coating is 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm or any value between any two of the above numerical ranges. Regulating the thickness of the ceramic coating within the above range is beneficial for the ceramic coating to increase the volume of the fast-charged secondary battery less on the basis of its high hardness and good heat resistance. In this way, the probability of the energy density of the fast-charged secondary battery being damaged due to the increase in the thickness of the ceramic coating can be reduced, so that the fast-charged secondary battery has good thermal safety performance and energy density while taking into account the dynamic performance, cycle performance and mechanical reliability.

[0066] In one embodiment of the present application, the ceramic coating includes ceramic particles and a ceramic coating binder. The present application has no particular restrictions on the type of ceramic coating binder, as long as the purpose of the present application can be achieved. For example, 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 has no particular restrictions on 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%.

[0067] 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.

[0068] The positive electrode sheet of the present application also includes a positive electrode active material layer, and the positive electrode active material layer is arranged on at least one surface of the positive electrode main region in the positive electrode current collector. In some embodiments, the positive electrode active material layer is arranged on one surface of the positive electrode main region in the positive electrode current collector. In other embodiments, the positive electrode active material layer is arranged on two surfaces of the positive electrode main region in the positive electrode current collector, wherein the above-mentioned "surface" can be part of the surface or all of the surface of the positive electrode main region in the positive electrode current collector. The present application has no special restrictions on the type of positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the positive electrode current collector may include aluminum foil, aluminum alloy foil, etc. The positive electrode active material layer of the present application includes positive electrode active materials, and the present application has no special restrictions on the type of positive electrode active materials, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include but is not limited to lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide or lithium iron manganese phosphate, etc. In the present application, the positive electrode active material may also contain non-metallic elements, for example, non-metallic elements include at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur, which can further improve the stability of the positive electrode active material. In the present application, there is no particular restriction on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the purpose 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 can be 6μm to 18μm. The thickness of the positive electrode active material layer is 30μm to 120μm.

[0069] 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).

[0070] The negative electrode sheet of the present application further includes a negative electrode active material layer, which is disposed on at least one surface of the negative electrode main body region in the negative electrode current collector. In some embodiments, the negative electrode active material layer is disposed on one surface of the negative electrode main body region in the negative electrode current collector. In other embodiments, the negative electrode active material layer is disposed on two surfaces of the negative electrode main body region in the negative electrode current collector. Herein, the above "surface" may be a partial surface or the entire surface of the negative electrode main body region in the negative electrode current collector. The present application does not particularly limit the type of the 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, Cu, Ni, etc. The negative electrode active material layer of the present application contains a negative electrode active material. The present application does not particularly limit the type of the negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include, but is not limited to, natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x < 2), at least one of Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, Li-Al alloy or metallic lithium. 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 6 μm to 10 μm, and the thickness of the negative electrode active material layer is 30 μm to 130 μm.

[0071] Optionally, the negative electrode active material layer may further include at least one of a negative electrode conductive agent, a stabilizer, and a negative electrode binder. The present application does not particularly limit the types of the negative electrode conductive agent, 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. The present application does not particularly limit the mass ratio of the negative electrode active material, the negative electrode conductive agent, 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 conductive agent, 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).

[0072] In one embodiment of the present application, the fast-charging secondary battery further includes a housing, and the electrode assembly and the electrolyte are accommodated in the housing. The present application does not particularly limit the housing, which may be a housing well-known in the art, as long as the purpose of the present application can be achieved. For example, the housing includes, but is not limited to, an aluminum-plastic film, a steel shell.

[0073] The present application does not particularly limit the type of the fast-charging secondary battery, which may include any device that undergoes an electrochemical reaction. For example, the fast-charging secondary battery may include, but is not limited to: a lithium metal secondary battery, a lithium-ion secondary battery (lithium-ion battery), a sodium-ion secondary battery (sodium-ion battery), a lithium polymer secondary battery, a lithium-ion polymer secondary battery.

[0074] The fast-charging secondary battery of the present application can be used under the condition of a charging rate of 5C to 15C. For example, the charging rate can be 5C, 6C, 7C, 8C, 9C, 10C, 11C, 12C, 13C, 14C, 15C or any rate between any two of the above rate ranges.

[0075] 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.

[0076] For example, in one embodiment, 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.

[0077] For example, in another embodiment, 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 preparing the isolation membrane.

[0078] For example, in another embodiment, 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 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.

[0079] For example, in another embodiment, 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 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.

[0080] 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 3wt% to 6wt%. 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 8wt% to 12wt%. 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.

[0081] The present application does not impose any particular restrictions on the method for preparing the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, the method for preparing the positive electrode sheet includes but is not limited to the following steps: (1) 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; (2) preparing a positive electrode slurry; (3) 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; (4) 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; (5) cold pressing, cutting, and striping to obtain the positive electrode sheet. The present application does not impose any particular restrictions on the content and type of each component in the positive electrode slurry in the above step (2). 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 positive electrode slurry in step (2), as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the time and temperature of the drying in steps (3) and (4), 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 step (5), as long as the purpose of the present application can be achieved.

[0082] The present application does not impose any particular restrictions on the method for preparing the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, the method for preparing the negative electrode sheet includes but is not limited to the following steps: (1) 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; (2) preparing a negative electrode slurry; (3) 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; (4) 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; (5) cold pressing, cutting, and striping to obtain the negative electrode sheet. The present application does not impose any particular restrictions on the content and type of each component in the negative electrode slurry in the above step (2). 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 step (2), as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the time and temperature of the drying in steps (3) and (4), 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 step (5), as long as the purpose of the present application can be achieved.

[0083] This application does not impose any particular restrictions on the preparation method of a fast-charging secondary battery. Any preparation method known in the art may be used as long as the purpose of this application can be achieved. For example, the preparation method of a fast-charging secondary battery includes, but is not limited to, the following steps: stacking a positive electrode sheet, a separator, and a negative electrode sheet in sequence, and winding, folding, and other operations as needed to obtain an electrode assembly with a wound structure, 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 the housing to obtain a fast-charging secondary battery.

[0084] The second aspect of the present application provides an electrical device comprising the fast-charging secondary battery described in any of the aforementioned embodiments.

[0085] The electrical device of the present application is not particularly limited and may be any electrical device known in the art. For example, the electrical device may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-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.

[0086] Example

[0087] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods.

[0088] Test methods and equipment:

[0089] Average particle size test:

[0090] The average particle size of the first polymer binder and the second polymer binder can be determined by observing the cross section of the isolation film using a scanning electron microscope (SEM), measuring the diameters of 10 particles of the first polymer binder or the second polymer binder, and calculating the average value.

[0091] The average particle size of the ceramic particles can be determined by observing the cross section of the separator using a scanning electron microscope (SEM), measuring the diameters of 10 ceramic particles, and calculating the average value.

[0092] Test of single-sided coating weight of the first bonding coat:

[0093] After discharging the lithium-ion batteries from each example and comparative example, the separators were disassembled to obtain the test sample separators. Impurities on the separator surfaces were cleaned with dimethyl carbonate (DMC) and then dried at 60°C to obtain the test sample separators. A small disc was punched out and the separator mass was weighed, denoted as m1. The first adhesive coating was then peeled off, and the mass of the separator after the first adhesive coating was removed was measured, denoted as m2. The single-sided coating weight of the first adhesive coating was calculated as (m1 - m2) / S, where S is the area of ​​the small disc.

[0094] Test for single-sided coating weight of the second bonding coat:

[0095] After discharging the lithium-ion batteries from each example and comparative example, the separators were disassembled to obtain the test sample separators. Impurities on the separator surfaces were cleaned with dimethyl carbonate (DMC) and then dried at 60°C to obtain the test sample separators. A small disc was punched out and the separator mass was weighed, denoted as m1. The second adhesive coating was then peeled off, and the mass of the separator after the second adhesive coating was removed was measured, denoted as m2. The single-sided coating weight of the second adhesive coating was calculated as (m1 - m2) / S, where S is the area of ​​the small disc.

[0096] First Bond Coat Thickness Test:

[0097] The isolation film is subjected to argon ion polishing to obtain a cross section of the isolation film after coating. The cross section is observed using a scanning electron microscope and the thickness of the first bonding coating layer is measured.

[0098] Second bond coat thickness test:

[0099] The isolation film after coating is subjected to argon ion polishing to obtain a cross section of the isolation film, and the cross section is observed by a scanning electron microscope to measure the thickness of the second bonding coating layer.

[0100] Ceramic coating thickness test:

[0101] The isolation film cross section was obtained by performing argon ion polishing on the isolation film after coating, and the cross section was observed by scanning electron microscopy to measure the thickness of the ceramic coating.

[0102] Test of coverage of the first polymer binder:

[0103] A scanning electron microscope (SEM) was used to observe the surface of the first adhesive coating side of the isolation membrane coated with the first polymer binder. 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.

[0104] Second polymer binder coverage test:

[0105] The surface of the second adhesive coating side of the isolation film coated with the second polymer binder was observed by SEM. The coverage was obtained by dividing the area occupied by the second polymer binder substance in the electron microscope photo by the area of ​​the isolation film sampled in the entire electron microscope photo.

[0106] Test of the bonding force F1 of the separator to the positive electrode:

[0107] The 180° peel test standard (GB / T 6328-2008) was used to test the dry pressing adhesion between the separator and the positive electrode sheet. The separator and the positive electrode sheet were cut into 54.2 mm × 72.5 mm samples. The side of the separator provided with the second bonding coating was composited with the positive electrode sheet and hot pressed using a hot press under the conditions of 85°C, 1 MPa, and 85 s. The composite sample was cut into 15 mm × 54.2 mm strips and the adhesion was tested according to the 180° peel test standard.

[0108] Test of the bonding force F2 of the separator to the negative electrode:

[0109] The 180° peel test standard (GB / T 6328-2008) was used to test the dry pressing adhesion between the separator and the negative electrode sheet. The separator and the negative electrode sheet were cut into 54.2 mm × 72.5 mm samples. The side of the separator provided with the first bonding coating was composited with the negative electrode sheet and hot pressed using a hot press under the conditions of 85°C, 1 MPa, and 85 s. The composite sample was cut into 15 mm × 54.2 mm strips and the adhesion was tested according to the 180° peel test standard.

[0110] Dynamic performance test:

[0111] The lithium-ion batteries of the embodiments and comparative examples were subjected to a dynamic performance test under a charging rate of 10C. The specific steps are as follows:

[0112] The test temperature was adjusted to a constant temperature of 25°C, and the temperature sensing line of the multi-channel thermometer was placed at the center of the surface of the lithium-ion battery. The following steps were performed: (1) 10C constant current charging to 4.2V; (2) 8C constant current charging to 4.3V; (3) 6C constant current charging to 4.45V; (4) 4.45V constant voltage charging to 0.05C; (5) standing for 30 minutes; (6) 1C constant current discharge to 3.0V; (7) standing for 30 minutes; end;

[0113] Charging speed: the time from step (1) to step (4);

[0114] Charging temperature rise: The difference between the maximum temperature recorded by the temperature sensing line on the surface of the lithium-ion battery from step (1) to step (2) and the room temperature.

[0115] Ohmic impedance test:

[0116] Test instrument: IM6E electrochemical workstation from Zahner, Germany. Test method: conventional EIS electrochemical impedance spectroscopy test method for lithium-ion batteries.

[0117] The kinetic performance is characterized by ohmic impedance, charging speed and charging temperature rise. Among them, the lower the ohmic impedance, the shorter the charging time and the smaller the charging temperature rise, the better the kinetic performance.

[0118] Cycle performance test:

[0119] The lithium-ion batteries of the embodiments and comparative examples were subjected to a cycle performance test at a charge rate of 10C, and the specific steps were as follows:

[0120] Adjust the test temperature to 25℃ and start the test: (1) 10C constant current charging to 4.2V; (2) 8C constant current charging to 4.3V; (3) 6C constant current charging to 4.45V; (4) 4.45V constant voltage charging to 0.05C; (5) stand for 5 minutes; (6) 1C constant current discharge to 3.0V; (7) stand for 5 minutes; (8) cycle steps (1) to (7) for 1000 times (cls); end;

[0121] Capacity retention (%) = discharge capacity after 1000 cycles (cls) / first-cycle discharge capacity × 100%.

[0122] Mechanical reliability test:

[0123] The test temperature was adjusted to a constant 20°C. The lithium-ion battery was fully charged according to the following steps: charging at a constant current of 0.5C to 4.45V, and then charging at a constant voltage of 4.45V to 0.05C. The lithium-ion battery was placed in a drop fixture and dropped onto a concrete floor in a test environment of 20±5°C. The battery was dropped from a height of 1.5m onto a concrete floor, with the battery being dropped once along each of the six sides and once at each of the four corners of the housing, for a total of 10 rounds. At the end of the test, the lithium-ion battery was disassembled.

[0124] Judgment criteria: The battery passed the test if there was no fire, explosion, or smoke after the test, and no breakage of the positive or negative electrode tab after disassembly. Ten lithium-ion batteries were tested for each embodiment and comparative example.

[0125] Drop pass rate (%) = number of lithium-ion batteries passed / 10×100%.

[0126] Thermal safety performance test:

[0127] Lithium-ion battery hot box test: First, the lithium-ion battery is charged at 1.5C to 4.45V. Second, the fully charged lithium-ion battery is placed in an oven, heated at 5°C / min to 135°C, and held there for 1 hour. The lithium-ion battery passes the test if it does not catch fire or explode. Each example and comparative example uses 100 lithium-ion batteries for testing. The hot box test pass rate = number of batteries passing the test / 100 × 100%. The hot box test pass rate indicates the thermal safety performance of the lithium-ion battery. A higher hot box test pass rate indicates better thermal safety performance.

[0128] Example 1-1

[0129] <Preparation of Separator>

[0130] A single-layer polypropylene film with a thickness of 5 μm is used as the base material of the isolation membrane;

[0131] 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;

[0132] 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 = 1 × 10 3 ~8×10 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;

[0133] The second polymer binder polyvinylidene fluoride (Mw = 8 × 10 5 ~9×10 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 10μm; the second polymer binder is a non-core-shell structure;

[0134] 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, thereby obtaining an isolation membrane (see Figure 8 for the structure, but not limited to Figure 8).

[0135] 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%.

[0136] <Preparation of positive electrode sheet>

[0137] 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 96:2:2, N-methylpyrrolidone (NMP) is added as a solvent, and stirred in a vacuum mixer until a solid content of 75wt% and a uniform positive electrode slurry is obtained. The positive electrode slurry is evenly coated on the positive electrode main area of ​​one surface of a positive electrode current collector aluminum foil with a thickness of 13μm, 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 positive electrode main area of ​​the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode active material layer. The sheet is then cold pressed, cut into pieces, and slit. After slitting, it is dried at 85°C under vacuum for 4 hours to obtain a positive electrode sheet with a specification of 60mm×1580mm for use. The single layer thickness of the positive electrode active material layer is 38.5μm, and the thickness of the positive electrode sheet is 90μm. The positive electrode tab area of ​​the positive electrode current collector is extended integrally (the structure is shown in Figure 3, but is not limited to Figure 3) to form 20 positive electrode tabs. The compacted density of the positive electrode sheet is 4.0g / cm 3 .

[0138] <Preparation of negative electrode sheet>

[0139] The negative electrode active material artificial graphite, 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 ) were mixed in a mass ratio of 96.5:1.0:1.0:1.5, and then deionized water was added as a solvent. The mixture was stirred in a vacuum mixer until a solid content of 51 wt% and a uniform negative electrode slurry was obtained. The negative electrode slurry was evenly coated on the negative electrode main area of ​​one surface of a 10 μm thick negative electrode current collector copper foil and dried at 85°C to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. The above steps were then repeated on the negative electrode main area of ​​the other surface of the copper foil to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. The sheet was then cold pressed, cut, and slit, and then dried at 110°C under vacuum for 4 hours to obtain a negative electrode sheet with a size of 62 mm × 1600 mm for later use. The thickness of the negative electrode active material layer was 58.5 μm, and the thickness of the negative electrode sheet was 127 μm. The negative electrode tab area of ​​the negative electrode current collector is extended integrally (the structure is shown in Figure 4, but is not limited to Figure 4) to form 20 negative electrode tabs. The compaction density of the negative electrode sheet is 1.5g / cm 3 .

[0140] <Preparation of Electrolyte>

[0141] 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 fluorophosphate (LiPF6), solvent, and additive adiponitrile are prepared in a mass ratio of 8:90:2 to obtain an electrolyte.

[0142] <Preparation of lithium-ion batteries>

[0143] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to act as an insulator, and then wound to form 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. The first adhesive coating in the separator is close to the negative electrode sheet, and the second adhesive coating is close to the positive electrode sheet. After winding, the positive electrode sheet and the negative electrode sheet in the electrode assembly are layers, and N1=0 layers of positive electrode sheets are arranged between two adjacent positive electrode tabs, and N2=0 layers of negative electrode sheets are arranged between two adjacent negative electrode tabs (see Figure 1 for the arrangement of the positive and negative tabs, but are not limited to Figure 1).

[0144] The electrode assembly is placed in an aluminum-plastic film shell, and after drying, the electrolyte is injected. The lithium-ion battery is obtained through vacuum packaging, standing, formation, capacity, degassing, and trimming processes.

[0145] Example 1-2 to Example 1-9

[0146] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0147] Examples 1-10

[0148] 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.

[0149] Examples 1-11

[0150] The rest is 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.

[0151] Example 1-12 to Example 1-23

[0152] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0153] Examples 1-24

[0154] <Preparation of lithium-ion batteries>

[0155] 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.

[0156] <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.

[0157] Example 2-1 to Example 2-4

[0158] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 1-1.

[0159] Example 3-1

[0160] <Preparation of Separator>

[0161] 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 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; 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 obtaining an isolation membrane (see Figure 7 for the structure, but not limited to Figure 7).

[0162] The rest is the same as Example 1-1.

[0163] <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 Example 1-1.

[0164] Example 3-2

[0165] <Preparation of Separator>

[0166] A ceramic coating slurry is coated on one surface of an isolation membrane substrate, and after drying at 60°C, a first ceramic coating is formed on one surface of the isolation membrane substrate; a ceramic coating slurry is coated on the other surface of the isolation membrane substrate, and after drying at 60°C, a second ceramic coating is formed on the other surface of the isolation membrane substrate; a second bonding coating slurry is coated on the surface of the first 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 first ceramic coating away from the isolation membrane substrate; a first bonding coating slurry is coated on the surface of the second 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 second ceramic coating away from the isolation membrane substrate, thereby obtaining an isolation membrane (see Figure 9 for the structure, but not limited to Figure 9).

[0167] The rest is the same as Example 1-1.

[0168] <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 Example 1-1.

[0169] Example 3-3

[0170] Except that the ceramic coating layer was not provided in the <Preparation of Separator>, the rest was the same as Example 3-1.

[0171] Example 3-4 to Example 3-12

[0172] Except for adjusting the relevant preparation parameters according to Table 4, the rest is the same as Example 1-1.

[0173] Comparative Examples 1 to 4

[0174] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0175] Comparative Example 5

[0176] <Preparation of positive electrode sheet>

[0177] 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 96:2:2, 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 one surface of a 13 μm thick positive electrode current collector aluminum foil and dried at 95°C to obtain a positive electrode sheet coated on one side with a positive electrode active material layer. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated on both sides with a positive electrode active material layer. The sheet was then cold pressed, cut, and slit. After slitting, it was dried at 85°C under vacuum for 4 hours. A positive electrode tab was welded to the surface of the positive electrode current collector 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 38.5 μm, and the thickness of the positive electrode sheet was 90 μm.

[0178] <Preparation of negative electrode sheet>

[0179] The negative electrode active material artificial graphite, 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 ) were mixed in a mass ratio of 96.5:1.0:1.0:1.5, and then deionized water was added as a solvent. The mixture was stirred in a vacuum mixer until a solid content of 51 wt% and a uniform negative electrode slurry was obtained. The negative electrode slurry was evenly coated on one surface of a 10 μm thick negative electrode current collector copper foil and dried at 85°C to obtain a negative electrode sheet coated on one side with a negative electrode active material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode active material layer. The slurry was then cold pressed, cut, and slit. After slitting, it was dried at 110°C under vacuum for 4 hours. A negative electrode tab was welded to the surface of the negative electrode current collector to obtain a negative electrode sheet measuring 62 mm x 1600 mm for later use. The single layer thickness of the negative electrode active material layer was 58.5 μm, and the thickness of the negative electrode sheet was 127 μm.

[0180] <Preparation of lithium-ion batteries>

[0181] The 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.

[0182] <Preparation of Separator> and <Preparation of Electrolyte> were the same as those in Example 1-1.

[0183] Comparative Example 6

[0184] <Preparation of Separator>

[0185] 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.

[0186] The rest is the same as Example 1-1.

[0187] <Preparation of lithium-ion batteries>

[0188] 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.

[0189] <Preparation of positive electrode sheet>, <Preparation of negative electrode sheet>, and <Preparation of electrolyte solution> are the same as those in Example 1-1.

[0190] Comparative Example 7

[0191] <Preparation of Separator>

[0192] 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.

[0193] The rest is the same as Example 1-1.

[0194] <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 6.

[0195] Comparative Example 8

[0196] <Preparation of Positive Electrode Sheet> and <Preparation of Negative Electrode Sheet> are the same as those in Comparative Example 5.

[0197] <Preparation of Separator>, <Preparation of Electrolyte>, and <Preparation of Lithium Ion Battery> are the same as those in Comparative Example 6.

[0198] Comparative Example 9

[0199] <Preparation of Positive Electrode Sheet> and <Preparation of Negative Electrode Sheet> are the same as those in Comparative Example 5.

[0200] <Preparation of Separator>, <Preparation of Electrolyte>, and <Preparation of Lithium Ion Battery> are the same as those in Comparative Example 7.

[0201] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 5.

[0202] Table 1

[0203] 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.

[0204] Table 2

[0205] From Examples 1-1 to 1-24 and Comparative Examples 1 to 9, it can be seen that the secondary battery of the embodiment of the present application has a multi-pole structure by providing a positive electrode current collector integrally extending to form a plurality of positive electrode tabs and a negative electrode current collector integrally extending to form a plurality of negative electrode tabs. At the same time, a first bonding coating and a second bonding coating are respectively provided 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 scope of the present application, so that the bonding force F1 of the isolation membrane to the positive electrode sheet and the bonding force F2 of the isolation membrane to the negative electrode sheet F2 is higher, and the secondary battery has lower ohmic impedance, shorter charging time (that is, higher charging speed) and lower charging temperature rise at a charging rate of 10C, indicating that the secondary battery has good dynamic performance under fast charging conditions. The secondary battery has a higher capacity retention rate at a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast charging conditions. The secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability. Therefore, the secondary battery of the embodiment of the present application can take into account dynamic performance, cycle performance and mechanical reliability under fast charging conditions. However, the average particle size of the first polymer binder in the isolation membrane of the secondary batteries of Comparative Examples 1 and 2 is not within the scope of the present application; the average particle size of the second polymer binder in the isolation membrane of the secondary batteries of Comparative Examples 3 and 4 is not within the scope of the present application; the secondary battery of Comparative Example 5 has an embedded single-pole ear structure rather than the multi-pole ear structure of the present application; the secondary battery of Comparative Example 6 has a second adhesive coating on both sides of its isolation membrane rather than the isolation membrane structure of the present application; the secondary battery of Comparative Example 7 has a first adhesive coating on both sides of its isolation membrane rather than the isolation membrane structure of the present application; the secondary battery of Comparative Example 8 has a second adhesive coating on both sides of its isolation membrane rather than the isolation membrane structure of the present application, and has an embedded single-pole ear structure rather than the multi-pole ear structure of the present application; the secondary battery of Comparative Example 9 has a first adhesive coating on both sides of its isolation membrane , rather than the isolation membrane structure of the present application, and it has an embedded single-pole ear structure rather than the multi-pole ear structure of the present application; in the secondary batteries of Comparative Examples 1 to Comparative Examples 9, the adhesion F1 of the isolation membrane to the positive electrode sheet and / or the adhesion F2 of the isolation membrane to the negative electrode sheet are low, and the secondary battery has a higher ohmic impedance, a longer charging time (that is, a lower charging speed) and a higher charging temperature rise under a charging rate of 10C, indicating that the secondary battery has poor dynamic performance under fast charging conditions, or the secondary battery has a lower capacity retention rate under a charging rate of 10C, indicating that the secondary battery has lower cycle performance under fast charging conditions, or the secondary battery has a lower 1.5m drop pass rate, indicating that the secondary battery has lower mechanical reliability. Therefore, the secondary batteries of the comparative examples of the present application cannot take into account the dynamic performance, cycle performance and mechanical reliability under fast charging conditions.

[0206] The average particle size of the first polymer binder generally affects the kinetic performance, cycle performance, and mechanical reliability of the secondary battery. As can be seen from Examples 1-1 to 1-5, Comparative Examples 1 and 2, a secondary battery using an average particle size of the first polymer binder within the range of this application has a lower ohmic impedance, a shorter charging time, and a lower charging temperature rise at a charge rate of 10C, indicating that the secondary battery has good kinetic performance under fast charging conditions. The secondary battery has a higher capacity retention rate at a charge rate of 10C, indicating that the secondary battery has good cycle performance under fast charging conditions. The secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability. Thus, the secondary battery can balance kinetic performance, cycle performance, and mechanical reliability under fast charging conditions. Among them, compared with Example 1-2 and Example 1-5, the average particle size of the first polymer binder in Example 1-1, Example 1-3 and Example 1-4 is in the preferred range of 0.6μm to 1.6μm, which has lower ohmic impedance, shorter charging time, lower charging temperature rise, higher drop pass rate, and higher capacity retention rate, indicating that the secondary battery with the average particle size of the first polymer binder in the preferred range of 0.6μm to 1.6μm has good dynamic performance and mechanical reliability under fast charging conditions, and has higher cycle performance.

[0207] The average particle size of the second polymer binder generally affects the kinetic performance, cycle performance, and mechanical reliability of the secondary battery. As can be seen from Examples 1-1, 1-6, 1-9, Comparative Examples 3, and 4, a secondary battery having an average particle size of the second polymer binder within the range of the present application has a lower ohmic impedance, a shorter charging time, and a lower charging temperature rise at a charging rate of 10C, indicating that the secondary battery has good kinetic performance under fast charging conditions. The secondary battery has a higher capacity retention rate at a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast charging conditions. The secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability. Thus, the secondary battery can take into account kinetic performance, cycle performance, and mechanical reliability under fast charging conditions. Among them, compared with Example 1-6 and Example 1-9, the average particle size of the second polymer binder in Example 1-1, Example 1-7 and Example 1-8 is in the preferred range of 8μm to 12μm, which has lower ohmic impedance, shorter charging time, lower charging temperature rise, and higher capacity retention rate and drop pass rate, indicating that the secondary battery with the average particle size of the second polymer binder in the preferred range of 8μm to 12μm has good dynamic performance under fast charging conditions, and has higher cycle performance and mechanical reliability.

[0208] The values ​​of N1 and N2 often affect the kinetic performance, cycle performance, and mechanical reliability of secondary batteries. As can be seen from Examples 1-1, 1-10, and 1-11, as N1 and N2 increase, the secondary battery's ohmic impedance charging time and charging temperature rise both improve. However, the number of tabs decreases as N1 and N2 increase. Therefore, the energy density of Examples 1-10 and 1-11 is greater than that of Example 1-1.

[0209] The coverage rate Cr1 of the first polymer binder in the first bonding coating per unit area, the single-sided coating weight Cw1 of the first bonding coating, and the thickness H1 of the first bonding coating generally affect the dynamic performance, cycle performance, and mechanical reliability of the secondary battery. As can be seen from Examples 1-1, 1-12, and 1-17, a secondary battery having a coverage rate Cr1 of the first polymer binder in the first bonding coating per unit area, a single-sided coating weight Cw1 of the first bonding coating, and a thickness H1 of the first bonding coating within the scope of the present application is selected, which has a lower ohmic impedance, a shorter charging time, and a lower charging temperature rise at a charging rate of 10C, indicating that the secondary battery has good dynamic performance under fast charging conditions, the secondary battery has a higher capacity retention rate at a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast charging conditions, and the secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability. Thus, the secondary battery can take into account dynamic performance, cycle performance, and mechanical reliability under fast charging conditions.

[0210] The coverage Cr2 of the second polymer binder in the second bonding coat per unit area, the single-sided coating weight Cw2 of the second bonding coat, and the thickness H2 of the second bonding coat generally affect the dynamics, cycle performance, and mechanical reliability of the secondary battery. From Example 1-1, Example 1-18 to Example 1-23, it can be seen that the coverage Cr2 of the second polymer binder in the second bonding coat per unit area, the single-sided coating weight Cw2 of the second bonding coat, and the thickness H2 of the second bonding coat are selected to be in the secondary battery within the scope of the present application, which has lower ohmic impedance, shorter charging time (i.e., higher charging speed) and lower charging temperature rise under a charging rate of 10C, indicating that the secondary battery has good dynamics under fast charging conditions, and the secondary battery has a higher capacity retention rate under a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast charging conditions, and the secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability, and thus, the secondary battery can take into account dynamics, cycle performance, and mechanical reliability under fast charging conditions.

[0211] The positional relationship between the first and second adhesive coatings in the separator and the positive and negative electrode sheets typically affects the dynamic performance, cycling performance, and mechanical reliability of a secondary battery. 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 adhesion force F2 between the separator and the negative electrode sheet, resulting in poor drop resistance for the battery in Example 1-24 relative to that of Example 1-1. Furthermore, because the second adhesive coating in Example 1-24 corresponds to the negative electrode sheet, the lithium ion transmission path is longer during fast charging, resulting in a slightly longer charging time for Example 1-24 than for Example 1-1.

[0212] Table 3

[0213] The type of the first polymer binder generally affects the dynamic performance, cycle performance, and mechanical reliability of the secondary battery. As can be seen from Examples 1-1, 2-1, and 2-2, the secondary battery using the first polymer binder within the scope of the present application has a lower ohmic impedance, a shorter charging time, and a lower charging temperature rise at a charging rate of 10C, indicating that the secondary battery has good dynamic performance under fast charging conditions. The secondary battery has a higher capacity retention rate at a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast charging conditions. The secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability. Therefore, the secondary battery can take into account dynamic performance, cycle performance, and mechanical reliability under fast charging conditions.

[0214] The type of second polymer binder generally affects the dynamic performance, cycle performance, and mechanical reliability of the secondary battery. As can be seen from Examples 1-1, 2-3, and 2-4, the secondary battery using the type of second polymer binder within the scope of this application has a lower ohmic impedance, a shorter charging time, and a lower charging temperature rise at a charging rate of 10C, indicating that the secondary battery has good dynamic performance under fast charging conditions. The secondary battery has a high capacity retention rate at a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast charging conditions. The secondary battery has a high 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability. Therefore, the secondary battery can take into account dynamic performance, cycle performance, and mechanical reliability under fast charging conditions.

[0215] Table 4

[0216] Note: “\” in Table 4 indicates no corresponding parameter.

[0217] Table 5

[0218] The arrangement of the ceramic coating in the isolation membrane usually affects the dynamic performance, cycle performance, mechanical reliability and thermal safety performance of the fast-charged secondary battery. It can be seen from Examples 1-1, 3-1 and 3-3 that the arrangement of the ceramic coating in the isolation membrane can further improve the thermal safety performance of the fast-charged secondary battery on the basis of having good dynamic performance, cycle performance and mechanical reliability; the fast-charged secondary battery in which the number and positional relationship of the ceramic coating arranged in the isolation membrane are within the scope of this application has a lower ohmic impedance, a shorter charging time and a lower charging temperature rise at a charging rate of 10C, indicating that the secondary battery has good dynamic performance under fast-charge conditions, the secondary battery has a higher capacity retention rate at a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast-charge conditions, the secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability, the secondary battery has a higher hot box pass rate, indicating that the secondary battery has good thermal safety performance. As a result, the secondary battery can take into account dynamic performance, cycle performance and mechanical reliability under fast-charge conditions, and has good thermal safety performance.

[0219] The type and average particle size of ceramic particles usually affect the kinetic performance, cycle performance, mechanical reliability and thermal safety performance of fast-charged secondary batteries. It can be seen from Example 1-1, Example 3-4, Example 3-5 to Example 3-8 that the fast-charged secondary battery selected with the type and average particle size of ceramic particles within the scope of this application has a lower ohmic impedance, a shorter charging time and a lower charging temperature rise at a charging rate of 10C, indicating that the secondary battery has good kinetic performance under fast-charge conditions, the secondary battery has a higher capacity retention rate at a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast-charge conditions, the secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability, the secondary battery has a higher hot box pass rate, indicating that the secondary battery has good thermal safety performance. As a result, the secondary battery can take into account kinetic performance, cycle performance and mechanical reliability under fast-charge conditions, and has good thermal safety performance.

[0220] The thickness H3 of the ceramic coating usually affects the dynamic performance, cycle performance, mechanical reliability and thermal safety performance of the fast-charged secondary battery. It can be seen from Example 1-1, Example 3-9 to Example 3-12 that the fast-charged secondary battery with the thickness H3 of the ceramic coating selected within the scope of this application has a lower ohmic impedance, a shorter charging time and a lower charging temperature rise at a charging rate of 10C, indicating that the secondary battery has good dynamic performance under fast-charge conditions, the secondary battery has a higher capacity retention rate at a charging rate of 10C, indicating that the secondary battery has good cycle performance under fast-charge conditions, the secondary battery has a higher 1.5m drop pass rate, indicating that the secondary battery has good mechanical reliability, the secondary battery has a higher hot box pass rate, indicating that the secondary battery has good thermal safety performance. As a result, the secondary battery can take into account dynamic performance, cycle performance and mechanical reliability under fast-charge conditions, and has good thermal safety performance.

[0221] 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.

[0222] 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.

[0223] 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. A fast-charge secondary battery, wherein: The invention comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator disposed between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet comprises 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 sheet comprises 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 comprises a substrate, a first bonding coating and a second bonding coating, wherein the first bonding coating and the second bonding coating are respectively arranged on both sides of the isolation film substrate; The first bonding coating layer comprises 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 comprises a second polymer binder, and the average particle size of the second polymer binder is 4 μm to 15 μm.

2. The fast-charge secondary battery according to claim 1, wherein: An N1 layer of positive electrode sheet is arranged between two adjacent positive electrode tabs, and an N2 layer of negative electrode sheet is arranged between two adjacent negative electrode tabs, and N1 and N2 are independently selected from 0, 1, 2 or 3.

3. The fast-charge secondary battery 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.

4. The fast-charge secondary battery 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 8 μm to 12 μm.

5. The fast-charge secondary battery according to claim 1, wherein: The thickness of the first bonding coating layer is 0.2 μm to 4 μm; and / or the thickness of the second bonding coating layer is 5 μm to 20 μm.

6. The fast-charge secondary battery according to claim 1, wherein: The single-sided coating weight of the first bonding coating is 0.0001 mg / mm 2 To 0.001mg / mm 2 The single-sided coating weight of the second bonding coating is 0.0004 mg / mm 2 To 0.002mg / mm 2 .

7. The fast-charge secondary battery according to claim 1, wherein: The coverage rate of the first polymer binder in the first bonding coating layer per unit area is 40% to 60%.

8. The fast-charge secondary battery according to claim 1, wherein: The first polymer binder is a core-shell structure, comprising a first shell and a first core, wherein the polymerizable monomer of the first shell comprises 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, and the polymerizable monomer of the first core comprises at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid or maleic acid; or, The first polymer binder is a non-core-shell structure, and the polymerized monomer of the first polymer binder includes at least one of acrylic acid, methyl acrylate, butyl acrylate, butadiene, styrene, acrylonitrile, ethylene, fluorostyrene, chlorostyrene or propylene.

9. The fast-charge secondary battery 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%.

10. The fast-charge secondary battery according to claim 1, wherein: The second polymer binder is a core-shell structure, comprising a second outer shell and a second inner core, the polymerizable monomer of the second outer shell comprising at least one of vinylidene chloride, vinylidene fluoride, hexafluoropropylene, styrene, butadiene, acrylonitrile, acrylic acid, methyl acrylate or butyl acrylate, and the polymerizable monomer of the second inner core comprising at least one of ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate or ethyl chloromethylacrylate; or, The second polymer binder is a non-core-shell structure, and 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, styrene, butadiene or acrylonitrile.

11. The fast-charge secondary battery according to claim 1, wherein: The isolation film further comprises a ceramic coating, wherein the ceramic coating is disposed between the isolation film substrate and the first bonding coating, and / or the ceramic coating is disposed between the isolation film substrate and the second bonding coating; The ceramic coating includes ceramic particles, and the average particle size of the ceramic particles is 1 μm to 3 μm.

12. The fast-charge secondary battery according to claim 11, wherein: The ceramic particles include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium hydroxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride or silicon nitride.

13. The fast-charge secondary battery according to claim 11, wherein: The ceramic coating has a thickness of 0.5 μm to 6 μm.

14. An electrical device comprising the fast-charged secondary battery according to any one of claims 1 to 13.

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