Secondary battery and preparation method therefor, electrode sheet, and electric device

Abstract

The present application relates to a secondary battery and a preparation method therefor, an electrode sheet, and an electric device. The secondary battery comprises an electrode sheet, the electrode sheet comprising a current collector, an active layer, and a first insulating layer, wherein the current collector comprises a main body portion and a tab protruding from the main body portion in a first direction, the main body portion comprising a coating region and a transition region arranged between the coating region and the tab; the active layer is arranged on the surface of the coating region; and at least part of the first insulating layer is arranged on the surface of the transition region, and the first insulating layer comprises a microcapsule, the microcapsule comprising a core and a shell covering at least part of the surface of the core, the core comprising a fire extinguishing material, and the shell comprising a thermoplastic polymer.

Description

Secondary batteries, their preparation methods, electrode plates, and electrical devices Cross-referencing

[0001] This application incorporates Chinese Patent Application No. 202411545355.9, filed on October 31, 2024, entitled “Secondary Battery and Method for Preparation Thereof, Electrode Sheets and Electrical Device”, which is incorporated herein by reference in its entirety. Technical Field

[0002] This application relates to the field of secondary battery technology, and in particular to a secondary battery and its preparation method, electrode plates, and electrical device. Background Technology

[0003] In recent years, with the increasingly wide range of applications of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0004] Secondary batteries pose a risk of thermal runaway during their fabrication or use. Preventing or delaying thermal runaway is of great significance for the further application and development of batteries. Therefore, how to reduce the risk of thermal runaway in secondary batteries is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] This application provides a secondary battery and its preparation method, electrode plates, and electrical device, aiming to reduce the risk of thermal runaway of the secondary battery.

[0006] A first aspect of this application provides a secondary battery, including an electrode sheet, the electrode sheet including a current collector, an active layer and a first insulating layer;

[0007] The current collector includes a main body and an electrode tab protruding from the main body along a first direction. The main body includes a coating area and a transition area between the coating area and the electrode tab.

[0008] The active layer is disposed on the surface of the coating area, and at least a portion of the first insulating layer is disposed on the surface of the transition area. The first insulating layer includes microcapsules, each microcapsule including a core and a wall covering at least a portion of the surface of the core. The core includes a fire extinguishing material, and the wall includes a thermoplastic polymer.

[0009] When the current collector with the first insulating layer is cut, the first insulating layer is heated, and the thermoplastic polymer in the microcapsule melts, causing the capsule wall to rupture and releasing the fire extinguishing material. The fire extinguishing material vaporizes under these conditions, carrying away excess heat and oxygen, which can reduce the risk of fire during the cutting process and reduce the impact on the insulation effect of the first insulating layer, thereby reducing the risk of thermal runaway of the secondary battery.

[0010] Furthermore, when the current collector with the first insulating layer is cut, the thermoplastic polymer in the microcapsule melts when heated and can flow to the end face of the current collector to cover the exposed end face and the burrs generated during the cutting process, reducing the risk of burrs overlapping with electrode plates of opposite polarity, thereby further reducing the risk of thermal runaway of the secondary battery.

[0011] In some embodiments, the core component accounts for 60% to 80% of the mass of the microcapsule. By controlling the mass percentage of the core component within the microcapsule to be within the above range, the risk of fire during the cutting process can be further reduced. Further, the core component accounts for 65% to 70% of the mass of the microcapsule.

[0012] In some embodiments, the volume average particle size Dv50 of the microcapsules is 6 μm to 15 μm. By adjusting the Dv50 of the microcapsules, on the one hand, the quality of the capsule core can be controlled, enabling the microcapsules to achieve a better fire extinguishing effect; on the other hand, it is beneficial to improve the uniformity of the first insulating layer, thereby further improving the insulation effect of the first insulating layer.

[0013] In some embodiments, the thickness of the first insulating layer on one side of the current collector is 20 μm to 50 μm. This allows it to be matched with electrode sheets of higher compaction density, effectively utilizing the fire extinguishing effect of the fire extinguishing material in the microcapsule when the heat during cutting is high, and reducing the risk of fire during the cutting process.

[0014] In some embodiments, the first insulating layer is provided on both sides of the current collector.

[0015] In some embodiments, the boiling point of the fire extinguishing material is less than or equal to 200°C. This allows the thermoplastic polymer to melt and flow during cutting, and the released fire extinguishing material vaporizes, carrying away excess heat and oxygen, thus reducing the risk of fire during the cutting process.

[0016] In some embodiments, the extinguishing material includes one or more of perfluorohexanone, fluoroalkyl extinguishing agents, and halon extinguishing agents.

[0017] In some embodiments, the fluoroalkane fire extinguishing agent includes one or more of heptafluoropropane and hexafluoropropane.

[0018] In some embodiments, the halon-type fire extinguishing agent includes one or more of bromochlorodifluoromethane, bromotrifluoromethane, and dibromotetrafluoroethane.

[0019] The above-mentioned types of fire extinguishing materials have the advantages of fast fire extinguishing speed and good fire extinguishing effect. In addition, the above-mentioned types of fire extinguishing materials have good insulation properties, which can reduce the risk of short circuit of electrode plates.

[0020] In some embodiments, the thermoplastic polymer has a dropping melting point of 80°C to 200°C. This design reduces the risk of the thermoplastic polymer melting and flowing during the processing of the electrode sheet, and also reduces the risk that a second insulating layer cannot be formed on the exposed end face of the current collector during the cutting process, or that the fire extinguishing material cannot be released in a timely manner.

[0021] In some embodiments, the thermoplastic polymer includes at least one of a crystalline thermoplastic polymer and an amorphous thermoplastic polymer.

[0022] In some embodiments, the crystalline thermoplastic polymer includes one or more of polyethylene, polypropylene, polyamide, polyimide, and their respective modified polymers.

[0023] In some embodiments, the amorphous thermoplastic polymer includes one or more of microcrystalline wax, polystyrene, polymethyl methacrylate, polyethyl methacrylate, polybutyl acrylate, and their respective modified polymers.

[0024] The aforementioned types of crystalline or amorphous thermoplastic polymers have high insulation and oxidation resistance, exhibit no oxidation peak at 3V to 5V voltages, and have relatively high stability. Furthermore, the use of these types of crystalline or amorphous thermoplastic polymers can effectively cover the exposed end faces and burrs of the current collector.

[0025] In some embodiments, the first insulating layer further includes an adhesive. The adhesive can improve the adhesion between the microcapsules in the first insulating layer and the current collector, reducing the risk of the first insulating layer detaching from the current collector.

[0026] In some embodiments, the mass ratio of the microcapsules to the adhesive in the first insulating layer is (50-70):(10-30). This facilitates the melt flow of the thermoplastic polymer in the microcapsules to cover the exposed end faces and burrs of the current collector, while also further reducing the risk of the first insulating layer detaching from the current collector.

[0027] In some embodiments, the first insulating layer further includes a ceramic material. This reduces the risk of aluminum leakage due to thermal shrinkage of the first insulating layer.

[0028] In some embodiments, the mass ratio of the microcapsules to the ceramic material in the first insulating layer is (50-70):(10-20). Designing the mass ratio of the microcapsules to the ceramic material within this range facilitates the melt flow of the thermoplastic polymer in the microcapsules, thereby covering the exposed end face and burrs of the current collector. Simultaneously, it helps to further reduce the risk of aluminum leakage due to thermal shrinkage of the first insulating layer.

[0029] In some embodiments, the ceramic material includes one or more of boehmite and alumina.

[0030] In some embodiments, the microcapsules in the first insulating layer are mixed with the ceramic material.

[0031] In some embodiments, the first insulating layer includes a first portion and a second portion connected to the first portion, the first portion being disposed on the surface of the transition region, and the second portion extending along the first direction and disposed on a portion of the surface of the tab. This reduces the risk of the tab colliding with an electrode sheet of opposite polarity, thereby further reducing the risk of thermal runaway in the secondary battery.

[0032] In some embodiments, the electrode sheet further includes a second insulating layer;

[0033] The main body includes a first end face and a second end face, the first end face being a sidewall adjacent to the transition region, and the second end face being a sidewall adjacent to the coating region. The second insulating layer is disposed on the first end face and / or the second end face of the main body; and / or,

[0034] The electrode tab includes a third end face, which is a sidewall adjacent to the second portion of the first insulating layer, and the second insulating layer is disposed at the third end face. This reduces the risk of electrode plates colliding with electrode plates of opposite polarity and the risk of thermal runaway in the secondary battery.

[0035] In some embodiments, the second insulating layer comprises only the thermoplastic polymer, or the second insulating layer comprises the microcapsules.

[0036] In some embodiments, the thickness of the second insulating layer is 50 nm to 200 nm. This allows for better coverage of the exposed end face of the current collector, further reducing the risk of burrs overlapping with electrode plates of opposite polarity.

[0037] In some embodiments, the electrode sheet is a positive electrode sheet, the current collector is a positive current collector, the active layer is a positive active layer, and the electrode active material in the active layer is a positive active material.

[0038] A second aspect of this application provides a method for preparing the secondary battery described in the first aspect of this application, including the step of preparing the electrode sheet; the step of preparing the electrode sheet includes:

[0039] A first slurry containing electrode active material is disposed in the coating area of ​​the main body of the current collector to form the active layer;

[0040] A second slurry containing the microcapsules is disposed in the transition region of the main body of the current collector to form the first insulating layer;

[0041] The current collector is cut, and at least part of the cutting line is set in the transition region to form an electrode tab protruding from the main body along the first direction, thereby preparing the electrode sheet.

[0042] The above preparation method is relatively simple to operate, which is conducive to the large-scale production of secondary batteries. When cutting the current collector with the first insulating layer, the risk of fire during the cutting process can be reduced, and the impact on the insulation effect of the first insulating layer can be minimized, thereby reducing the risk of thermal runaway of the secondary battery.

[0043] In some embodiments, the step of cutting the current collector includes:

[0044] A laser processing tool is controlled to cut the current collector with the first insulating layer along the cutting line. The laser processing tool has a power of 50W to 300W and a frequency of 100kHz to 1000kHz. This design allows the second insulating layer to be formed simultaneously with the cutting, which simplifies the preparation steps of the second insulating layer.

[0045] In some embodiments, the electrode sheet is a positive electrode sheet, the current collector is a positive current collector, the active layer is a positive active layer, and the electrode active material is a positive active material.

[0046] A third aspect of this application provides an electrode sheet, comprising a current collector, an active layer, and a first insulating layer;

[0047] The current collector includes a main body and an electrode tab protruding from the main body along a first direction. The main body includes a coating area and a transition area between the coating area and the electrode tab.

[0048] The active layer is disposed on the surface of the coating area, and at least a portion of the first insulating layer is disposed on the surface of the transition area. The first insulating layer includes microcapsules, each microcapsule including a core and a wall covering at least a portion of the surface of the core. The core includes a fire extinguishing material, and the wall includes a thermoplastic polymer.

[0049] The microcapsules introduced into the electrode sheet can reduce the risk of fire during the cutting process and reduce the impact on the insulation effect of the first insulating layer, thereby reducing the risk of thermal runaway of the secondary battery.

[0050] In some embodiments, the electrode sheet is a positive electrode sheet, the current collector is a positive current collector, the active layer is a positive active layer, and the electrode active material in the active layer is a positive active material.

[0051] A fourth aspect of this application provides an electrical device comprising at least one of the secondary battery described in the first aspect of this application, the secondary battery prepared by the method described in the second aspect of this application, and the electrode sheet described in the third aspect of this application.

[0052] The aforementioned electrical device includes at least one of the secondary battery described in this application, the secondary battery prepared by the aforementioned preparation method, and the aforementioned electrode sheet, and therefore has at least the same advantages as the aforementioned secondary battery, the secondary battery prepared by the aforementioned preparation method, and the aforementioned electrode sheet.

[0053] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0054] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort. In the drawings:

[0055] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of this application.

[0056] Figure 2 is a schematic diagram of the current collector before the electrode tab in an embodiment of this application.

[0057] Figure 3 is a schematic diagram of the electrode plates in a secondary battery according to an embodiment of this application.

[0058] Figure 4 is a cross-sectional view along the MM direction in Figure 3.

[0059] Figure 5 is a schematic diagram of the electrode plates in a secondary battery according to another embodiment of this application.

[0060] Figure 6 is an exploded view of the secondary battery shown in Figure 1.

[0061] Figure 7 is a schematic diagram of a battery module according to an embodiment of this application.

[0062] Figure 8 is a schematic diagram of a battery pack according to an embodiment of this application.

[0063] Figure 9 is an exploded view of a battery pack according to an embodiment of this application, as shown in Figure 8.

[0064] Figure 10 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0065] Explanation of reference numerals in the attached figures:

[0066] 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device; 7 Electrode plate; 70 Current collector; 701 Active layer; 702 First insulating layer; 7021 First part; 7022 Second part; 703 Second insulating layer; 71 Main body; 711 Coated area; 712 Transition area; 71a First end face; 71b Second end face; 72 Tab; 72a Third end face; 73 Cutting line. Detailed Implementation

[0067] The following describes in detail, with appropriate reference to the accompanying drawings, some embodiments of the secondary battery and its preparation method, electrode plates, and electrical device of this application. However, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0068] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0069] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0070] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0071] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0072] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0073] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0074] The electrode plates in a secondary battery typically consist of an active layer and an insulating layer containing a polymer. The active layer provides active ions, which can embed or extract into the active layer, enabling the storage and release of electrical energy. The insulating layer reduces the risk of contact between the positive and negative electrode plates, preventing short circuits that could lead to thermal runaway, fire, or even explosion. After the active and insulating layers are formed on the current collector, it is usually necessary to cut the current collector to form tabs. Because the insulating layer contains polymers, the insulation layer can be heated during the cutting process, which can easily cause the polymer to ignite, posing a threat to production safety and affecting the insulation effect, thus increasing the risk of thermal runaway in the battery.

[0075] Based on this, the first aspect of this application provides a secondary battery, including an electrode sheet, the electrode sheet including a current collector, an active layer and a first insulating layer;

[0076] The current collector includes a main body and an electrode tab protruding from the main body along a first direction. The main body includes a coating area and a transition area between the coating area and the electrode tab.

[0077] An active layer is disposed on the surface of the coating area, and at least a portion of the first insulating layer is disposed on the surface of the transition area. The first insulating layer includes microcapsules, each microcapsule including a core and a wall covering at least a portion of the surface of the core. The core includes a fire extinguishing material, and the wall includes a thermoplastic polymer.

[0078] When the current collector with the first insulating layer is cut, the first insulating layer is heated, and the thermoplastic polymer in the microcapsule melts, causing the capsule wall to rupture and releasing the fire extinguishing material. The fire extinguishing material vaporizes under these conditions, carrying away excess heat and oxygen, which can reduce the risk of fire during the cutting process and reduce the impact on the insulation effect of the first insulating layer, thereby reducing the risk of thermal runaway of the secondary battery.

[0079] Furthermore, when the current collector with the first insulating layer is cut, the thermoplastic polymer in the microcapsule melts when heated and can flow to the end face of the current collector to cover the exposed end face and the burrs generated during the cutting process, reducing the risk of burrs overlapping with electrode plates of opposite polarity, thereby further reducing the risk of thermal runaway of the secondary battery.

[0080] In this application, fire extinguishing materials refer to materials that can effectively disrupt combustion conditions in the combustion zone, thereby inhibiting or extinguishing combustion. As a non-limiting example, fire extinguishing materials include, but are not limited to, one or more of perfluorohexanone, fluoroalkyl fire extinguishing agents, and halon fire extinguishing agents.

[0081] Without limitation, scanning electron microscopy (SEM) can be used to observe whether there is a first insulating layer and microcapsules between the active layer and the tab, and the thickness of the first insulating layer can be measured using SEM. Infrared spectroscopy can be used to test the composition of the first insulating layer in the electrode sheet, and to confirm whether there are fire extinguishing materials and thermoplastic polymers in the microcapsules.

[0082] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of this application; Figure 2 is a schematic diagram of the current collector before the electrode tab is processed according to an embodiment of this application; Figure 3 is a schematic diagram of the electrode sheet in the secondary battery according to an embodiment of this application; and Figure 4 is a cross-sectional view along the MM direction in Figure 3. In some embodiments, referring to Figures 1 to 4, the secondary battery 5 includes an electrode sheet 7, which includes a current collector 70, an active layer 701, and a first insulating layer 702.

[0083] The current collector 70 includes a main body 71 and an electrode tab 72 protruding from the main body 71 along a first direction. The main body 71 includes a coating area 711 and a transition area 712 disposed between the coating area 711 and the electrode tab 72.

[0084] An active layer 701 is disposed on the surface of the coating area 711, and a first insulating layer 702 is disposed on the surface of the transition area 712. The first insulating layer 702 includes microcapsules, each microcapsule including a core and a wall covering at least a portion of the surface of the core. The core includes a fire extinguishing material, and the wall includes a thermoplastic polymer.

[0085] The first direction can be parallel to the plane on which the active layer 701 is located on the current collector 70. For example, the first direction can be the Y direction in Figures 2 to 4.

[0086] The current collector 70 has two surfaces opposite each other along its thickness direction. The coating region 711 can be disposed on any one or both surfaces of the current collector 70 along its thickness direction; correspondingly, the active layer 701 can be disposed on any one or both surfaces of the current collector 70 along its thickness direction. The transition region 712 can be disposed on any one or both surfaces of the current collector 70 along its thickness direction; correspondingly, the first insulating layer 702 can be disposed on any one or both surfaces of the current collector 70 along its thickness direction.

[0087] The tab 72 can be formed by cutting. Referring to Figures 2 to 4, the coating area 711 of the main body 71 of the current collector 70 is provided with an active layer 701, and the transition area 712 of the main body 71 of the current collector 70 is provided with a first insulating layer 702. The tab 72 can be formed by cutting the current collector 70 along the cutting line 73.

[0088] When the current collector 70 with the first insulating layer 702 is cut, the first insulating layer 702 is heated, and the thermoplastic polymer in the microcapsule melts, causing the capsule wall to rupture and releasing the fire extinguishing material. The fire extinguishing material vaporizes under these conditions, carrying away excess heat and oxygen, which can reduce the risk of fire during the cutting process and reduce the impact on the insulation effect of the first insulating layer 702, thereby reducing the risk of thermal runaway of the secondary battery 5.

[0089] Furthermore, when the current collector 70 with the first insulating layer 702 is cut, the thermoplastic polymer in the microcapsule melts when heated and can flow to the end face of the current collector 70 to cover the exposed end face and the burrs generated during the cutting process, reducing the risk of burrs overlapping with electrode plates of opposite polarity, thereby further reducing the risk of thermal runaway of the secondary battery 5.

[0090] In some embodiments, the first insulating layer 702 includes a first portion 7021 and a second portion 7022 connected to the first portion 7021. The first portion 7021 is disposed on the surface of the transition region 712, and the second portion 7022 extends along a first direction and is disposed on a portion of the surface of the tab 72. In this way, the first insulating layer 702 can reduce the risk of the tab 72 colliding with an electrode sheet of opposite polarity, thereby further reducing the risk of thermal runaway of the secondary battery 5.

[0091] In some embodiments, please refer to Figures 2 to 5, the electrode plate 7 further includes a second insulating layer 703;

[0092] The main body 71 includes a first end face 71a and a second end face 71b. The first end face 71a is a sidewall adjacent to the transition region 712, and the second end face 71b is a sidewall adjacent to the coating region 711. A second insulating layer 703 is disposed at the first end face 71a and / or the second end face 71b of the main body 71; and / or,

[0093] The tab 72 includes a third end face 72a, which is a sidewall adjacent to the second part 7022 of the first insulating layer 702, and the second insulation 703 is disposed at the third end face 72a.

[0094] This reduces the risk of electrode 7 colliding with electrode 7 of opposite polarity and the risk of thermal runaway in the secondary battery.

[0095] The aforementioned sidewall is adjacent to, but located on, a different surface from, the surface where the transition area 712 or the coating area 711 is located. Furthermore, the aforementioned sidewall is perpendicularly adjacent to, the surface where the transition area 712 or the coating area 711 is located.

[0096] In some embodiments, the second insulating layer 703 can be formed as shown in Figures 2 to 5, when the current collector 70 is cut along the cutting line 73, the first end face 71a of the main body 71 and / or the third end face 72a of the tab 72 are exposed. The thermoplastic polymer in the microcapsules of the first insulating layer 702 melts upon heating and flows to the first end face 71a and / or the third end face 72a to form the second insulating layer 703. The second insulating layer 703 may also be provided at a portion of the first end face 71a.

[0097] In other embodiments, the second insulating layer 703 can be formed by depositing an insulating layer slurry on at least one of the first end face 71a, the second end face 71b of the main body 71, and the third end face 72a of the tab 72. The insulating layer slurry may include microcapsules or only thermoplastic polymers, and the deposition method includes, but is not limited to, spraying.

[0098] In some embodiments, please refer to FIG3, the second insulating layer 703 is disposed at the third end face 72a of the tab 72.

[0099] Figure 5 is a schematic diagram of the electrode plates in a secondary battery according to another embodiment of this application. In some other embodiments, please refer to Figure 5, the second insulating layer 703 is disposed on the third end face 72a of the tab 72 and the first end face 71a and the second end face 71b of the main body 71.

[0100] In some embodiments, the second insulating layer 703 comprises only a thermoplastic polymer, or the second insulating layer 703 comprises microcapsules. When the second insulating layer 703 comprises microcapsules, when the electrode plate 7 is heated, causing the capsule wall of the microcapsule to rupture, fire extinguishing material can be released, reducing the risk of fire.

[0101] In some embodiments, referring to FIG4, the thickness L2 of the second insulating layer 703 is 50 nm to 200 nm. This allows for better coverage of the exposed end face of the current collector 70, further reducing the risk of burrs overlapping with electrode plates of opposite polarity. Non-limitingly, the thickness L2 of the second insulating layer 703 includes, but is not limited to: 50 nm, 70 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, or any range between the foregoing.

[0102] In this application, the unit "nm" refers to nanometers.

[0103] In some embodiments, the thickness L2 of the second insulating layer 703 is 200 nm to 2000 nm. Non-limitingly, the thickness L2 of the second insulating layer 703 includes, but is not limited to: 200 nm, 400 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm, 2000 nm, or any range between the foregoing.

[0104] In some embodiments, the core mass percentage of the microcapsule is 60% to 80%. By controlling the core mass percentage within the above range, the risk of fire during the cutting process can be further reduced. Non-limitingly, the core mass percentage within the microcapsule includes, but is not limited to, 60%, 62%, 64%, 65%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, or any range between the foregoing. Further, the core mass percentage within the microcapsule is 65% to 70%.

[0105] In some embodiments, the volume average particle size Dv50 of the microcapsules is 6 μm to 15 μm. By adjusting the Dv50 of the microcapsules, on the one hand, the quality of the capsule core can be controlled, enabling the microcapsules to achieve a better fire extinguishing effect; on the other hand, it is beneficial to improve the uniformity of the first insulating layer, thereby further improving the insulation effect of the first insulating layer.

[0106] In this application, the unit "μm" refers to micrometers.

[0107] In some embodiments, referring to Figure 4, the thickness L1 of the first insulating layer on one side of the current collector is 20 μm to 50 μm. This allows for compatibility with electrode sheets of higher compaction density, effectively maximizing the fire extinguishing effect of the fire-extinguishing material in the microcapsules and reducing the risk of fire during the cutting process when the heat generated during cutting is high. Non-limitingly, the thickness L1 of the first insulating layer on one side includes, but is not limited to: 20 μm, 23 μm, 25 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, or any range between the foregoing.

[0108] It should be noted that the thickness L1 of the first insulating layer on one side of the current collector means that the thickness L1 of the first insulating layer on any side of the current collector can be 20μm to 50μm. The thickness L1 of the first insulating layer on different sides of the current collector can be the same or different.

[0109] Understandably, the current collector has a first insulating layer on one or both sides. In some embodiments, the current collector has a first insulating layer on both sides. Understandably, the thickness of the first insulating layer on both sides of the current collector may be the same or different.

[0110] In some embodiments, the total thickness of the first insulating layer on both sides of the current collector is 40 μm to 100 μm. This allows for compatibility with electrode sheets of higher compaction density, effectively maximizing the fire extinguishing effect of the fire extinguishing material in the microcapsules and reducing the risk of fire during the cutting process when the heat of cutting is high. Non-limitingly, the total thickness of the first insulating layer on both sides of the current collector includes, but is not limited to: 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, or any range between the foregoing.

[0111] In some embodiments, the boiling point of the extinguishing material is less than or equal to 200 degrees Celsius (°C). This allows the thermoplastic polymer to melt and flow during cutting, and the vaporization of the released extinguishing material can carry away excess heat and oxygen, reducing the risk of fire during the cutting process. Non-limitingly, the boiling point of the extinguishing material includes, but is not limited to, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 140°C, 160°C, 180°C, 200°C, or a range between any two of the foregoing.

[0112] In some embodiments, the extinguishing material includes one or more of perfluorohexanone, fluoroalkyl extinguishing agents, and halon extinguishing agents.

[0113] In some embodiments, the fluoroalkane fire extinguishing agent includes one or more of heptafluoropropane and hexafluoropropane.

[0114] In some embodiments, halon-type fire extinguishing agents include one or more of bromochlorodifluoromethane, bromotrifluoromethane, and dibromotetrafluoroethane.

[0115] The above-mentioned types of fire extinguishing materials have the advantages of fast fire extinguishing speed and good fire extinguishing effect. In addition, the above-mentioned types of fire extinguishing materials have good insulation properties, which can reduce the risk of short circuit of electrode plates.

[0116] In some embodiments, the dropping point of the thermoplastic polymer is 80°C to 200°C. This design reduces the risk of the thermoplastic polymer melting and flowing during the processing of the electrode sheet, and also reduces the risk that a second insulating layer cannot be formed at the exposed end face of the current collector during the cutting process, or that the fire extinguishing material cannot be released in a timely manner. Non-limitingly, the dropping point of the thermoplastic polymer includes, but is not limited to: 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, or any range between the foregoing.

[0117] In this application, the dropping melting point of a thermoplastic polymer refers to the temperature at which the thermoplastic polymer changes from a solid or semi-solid state to a liquid state.

[0118] In some embodiments, the thermoplastic polymer includes at least one of a crystalline thermoplastic polymer and an amorphous thermoplastic polymer.

[0119] In some embodiments, the crystalline thermoplastic polymer includes one or more of polyethylene, polypropylene, polyamide, polyimide, and their respective modified polymers.

[0120] In some embodiments, the amorphous thermoplastic polymer includes one or more of microcrystalline wax, polystyrene, polymethyl methacrylate, polyethyl methacrylate, polybutyl acrylate, and their respective modified polymers.

[0121] The aforementioned types of crystalline or amorphous thermoplastic polymers have high insulation and oxidation resistance, exhibit no oxidation peak at 3V to 5V voltages, and have relatively high stability. Furthermore, the use of these types of crystalline or amorphous thermoplastic polymers can effectively cover the exposed end faces and burrs of the current collector.

[0122] In this application, the unit "V" refers to volt.

[0123] In some embodiments, the first insulating layer further includes an adhesive. The adhesive can improve the adhesion between the microcapsules in the first insulating layer and the current collector, reducing the risk of the first insulating layer detaching from the current collector. As a non-limiting example, the adhesive includes, but is not limited to, halogenated polymers, including, but not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0124] In some embodiments, the mass ratio of microcapsules to binder in the first insulating layer is (50–70):(10–30). Designing the mass ratio of microcapsules to binder within this range facilitates the melt flow of the thermoplastic polymer in the microcapsules, thereby covering the exposed end faces and burrs of the current collector, while further reducing the risk of the first insulating layer detaching from the current collector. Non-limitingly, the mass ratio of microcapsules to binder includes, but is not limited to: 50:10, 50:20, 50:30, 60:10, 60:20, 60:30, 70:10, 70:20, 70:30, or any range between the foregoing.

[0125] In some embodiments, the first insulating layer further includes a ceramic material. Introducing a ceramic material into the first insulating layer can reduce the risk of aluminum leakage due to thermal shrinkage of the first insulating layer.

[0126] In some embodiments, the mass ratio of microcapsules to ceramic material in the first insulating layer is (50–70):(10–20). Designing the mass ratio of microcapsules to ceramic material within this range facilitates the melt flow of the thermoplastic polymer in the microcapsules, thereby covering the exposed end faces and burrs of the current collector, while also further reducing the risk of aluminum leakage due to thermal shrinkage of the first insulating layer. Non-limitingly, the mass ratio of microcapsules to ceramic material includes, but is not limited to: 50:10, 50:20, 60:10, 60:20, 70:10, 70:20, or any range between the foregoing.

[0127] In some embodiments, the ceramic material includes one or more of boehmite and alumina.

[0128] In some embodiments, the microcapsules in the first insulating layer are intermixed with ceramic material. This reduces the risk of aluminum leakage due to thermal shrinkage of the first insulating layer.

[0129] In some embodiments, the electrode sheet is a positive electrode sheet, the current collector is a positive current collector, the active layer is a positive active layer, and the electrode active material in the active layer is a positive active material.

[0130] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on a polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0131] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: ternary cathode materials, lithium phosphates. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0132] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. In the examples of positive electrode active materials listed in this application, unless otherwise specified, the Li content refers to the initial state of the material. When positive electrode active materials are applied to the positive electrode in a battery system, the Li content in the positive electrode active material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode active materials, and non-limiting examples include coating modification.

[0133] In the examples of positive electrode active materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0134] The positive electrode active material includes sodium ion active material.

[0135] As an example, sodium-ion active materials may include one or more of the following: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0136] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of a sodium transition metal oxide is Na. x M1O2, wherein M1 may include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0137] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (Y1O4) structure. n -A class of compounds with anionic units. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y1 may be one or more of P, S, and Si; n represents (Y1O4). n- The price state.

[0138] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (Y1O4) ions. n- A class of compounds consisting of anionic units and halide anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y1 may be one or more of P, S, and Si, where n represents (Y1O4). n- The valence state; halogens can be one or more of F, Cl and Br.

[0139] Polyanionic compounds can also be sodium-ionized or tetrahedral (Y1O4) compounds. n- Anionic unit, polyhedral unit (Z1O) y ) m+ And a class of compounds with optional halide anions. Y1 can be one or more of P, S, and Si, and n represents (Y1O4). n- The valence state; Z represents a transition metal, which may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents (Z1O). y ) m+ The valence state; halogens can be one or more of F, Cl and Br.

[0140] Polyanionic compounds can include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y One or more of (0≤y≤1). Among them, M' in NaM'PO4F can include one or more of V, Fe, Mn and Ni.

[0141] Prussian blue compounds can contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds containing Prussian blue. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of Prussian blue compounds is Na. a Me b Me' c (CN)6, wherein Me and Me' can each be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0142] In some embodiments, the positive electrode active material includes a ternary positive electrode material, and the compaction density of the positive electrode sheet is 3.4 g / cm³. 3 ~3.7g / cm 3 .

[0143] In this application, the unit "g / cm" is used. 3 "" refers to grams per cubic centimeter.

[0144] In some embodiments, the positive electrode active material comprises lithium phosphate, and the compaction density of the positive electrode sheet is 3.4 g / cm³. 3 ~3.7g / cm 3 .

[0145] The aforementioned positive electrode sheet has a high compaction density. Under these conditions, the current collector after rolling may exhibit wavy edges or wrinkles. When this current collector is cut, for example using laser processing tools, the laser focus may shift vertically, resulting in some areas receiving higher laser energy. This could easily ignite the thermoplastic polymer in the first insulating layer, posing a threat to production safety. The above technical solution can reduce the risk of fire during the cutting process, while also minimizing the impact on the insulation effect of the first insulating layer, thus reducing the risk of thermal runaway in the secondary battery.

[0146] In some embodiments, the ternary cathode material includes one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt manganese oxide, and modified compounds thereof. Non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co 0.15 Al 0.05 O2.

[0147] In some embodiments, lithium phosphates include those with the chemical formula Li m A a Fe x D d P y E e O z G g The material comprises, wherein A includes at least one element selected from Al, Na, K and Mg; D includes at least one element selected from Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti and V; E includes at least one element selected from B, S, Si and N; G includes at least one element selected from S, F, Cl and Br; 0.5≤m≤1.5, 0≤a≤0.1, 0.5≤x≤1, 0≤d≤0.5, 0.5≤y≤1, 0≤e≤0.5, 3.5≤z≤4, and 0≤g≤0.5.

[0148] In some embodiments, the positive electrode active layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0149] In some embodiments, the positive electrode active layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0150] In some embodiments, the electrode sheet is a negative electrode sheet, the current collector is a negative current collector, the active layer is a negative active layer, and the electrode active material in the active layer is a negative active material.

[0151] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0152] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0153] In some embodiments, the negative electrode active layer may optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0154] In some embodiments, the negative electrode active layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0155] In some embodiments, the negative electrode active layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0156] A second aspect of this application provides a method for preparing a secondary battery, including the step of preparing electrode sheets; the step of preparing electrode sheets includes:

[0157] A first slurry containing electrode active material is placed in the coating area of ​​the main body of the current collector to form an active layer;

[0158] A second slurry containing microcapsules is disposed in the transition zone of the main body of the current collector to form a first insulating layer; the microcapsule includes a core and a wall covering at least a portion of the surface of the core, the core including a fire extinguishing material and the wall including a thermoplastic polymer.

[0159] The current collector is cut, and at least part of the cutting line is set in the transition zone to form an electrode tab protruding from the main body along the first direction, thereby preparing an electrode sheet.

[0160] The above preparation method is relatively simple to operate, which is conducive to the large-scale production of secondary batteries. When the current collector with the first insulating layer is cut, the first insulating layer is heated, and the thermoplastic polymer in the microcapsule melts, causing the capsule wall to rupture and releasing the fire extinguishing material. Under these conditions, the fire extinguishing material vaporizes, carrying away excess heat and oxygen, which can reduce the risk of fire during the cutting process. At the same time, it can reduce the impact on the insulation effect of the first insulating layer, thereby reducing the risk of thermal runaway of the secondary battery.

[0161] Furthermore, when the current collector with the first insulating layer is cut, the thermoplastic polymer in the microcapsule melts when heated and can flow to the end face of the current collector to cover the exposed end face and the burrs generated during the cutting process, reducing the risk of burrs overlapping with electrode plates of opposite polarity, thereby further reducing the risk of thermal runaway of the secondary battery.

[0162] In some embodiments, the step of cutting the current collector includes:

[0163] The laser processing tool is controlled to cut the current collector with the first insulating layer along the cutting line. The power of the laser processing tool is 50W to 300W and the frequency is 100kHz to 1000kHz.

[0164] In this application, the unit "W" refers to watts and the unit "kHz" refers to kilohertz.

[0165] By controlling the parameters of the laser processing tool within the above range, the thermoplastic polymer in the microcapsules of the first insulating layer melts upon heating during cutting and flows to the exposed end face of the current collector, thus forming the second insulating layer. This simplifies the preparation steps of the second insulating layer.

[0166] As a non-limiting example, the power of the laser processing tool includes, but is not limited to, 50W, 100W, 150W, 200W, 250W, 300W or any two of the foregoing, and the frequency includes, but is not limited to, 100kHz, 200kHz, 400kHz, 600kHz, 800kHz, 1000kHz or any two of the foregoing.

[0167] In some embodiments, the electrode sheet is a positive electrode sheet, the current collector is a positive current collector, the active layer is a positive active layer, and the electrode active material is a positive active material.

[0168] In some embodiments, the positive electrode active material includes a ternary positive electrode material, and the compaction density of the positive electrode sheet is 3.4 g / cm³. 3 ~3.7g / cm 3 .

[0169] In some embodiments, the positive electrode active material includes lithium phosphate, and the compaction density of the positive electrode sheet is 2.4 g / cm³. 3 ~2.7g / cm 3 .

[0170] The aforementioned positive electrode sheet has a high compaction density. Under these conditions, the current collector after rolling may exhibit wavy edges or wrinkles. When this current collector is cut, for example using laser processing tools, the laser focus may shift vertically, resulting in some areas receiving higher laser energy. This could easily ignite the thermoplastic polymer in the first insulating layer, posing a threat to production safety. The above technical solution can reduce the risk of fire during the cutting process, while also minimizing the impact on the insulation effect of the first insulating layer, thus reducing the risk of thermal runaway in the secondary battery.

[0171] In some embodiments, lithium phosphates include those with the chemical formula Li m A a Fe x D d P y E e O z G g The material comprises, wherein A includes at least one element selected from Al, Na, K and Mg; D includes at least one element selected from Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti and V; E includes at least one element selected from B, S, Si and N; G includes at least one element selected from S, F, Cl and Br; 0.5≤m≤1.5, 0≤a≤0.1, 0.5≤x≤1, 0≤d≤0.5, 0.5≤y≤1, 0≤e≤0.5, 3.5≤z≤4, and 0≤g≤0.5.

[0172] By adjusting the process conditions of the preparation method of the second aspect of this application, the secondary battery described in the first aspect of this application can be obtained.

[0173] A third aspect of this application provides an electrode sheet, comprising a current collector, an active layer, and a first insulating layer;

[0174] The current collector includes a main body and an electrode tab protruding from the main body along a first direction. The main body includes a coating area and a transition area between the coating area and the electrode tab.

[0175] An active layer is disposed on the surface of the coating area, and at least a portion of the first insulating layer is disposed on the surface of the transition area. The first insulating layer includes microcapsules, each microcapsule including a core and a wall covering at least a portion of the surface of the core. The core includes a fire extinguishing material, and the wall includes a thermoplastic polymer.

[0176] The microcapsules introduced into the electrode sheet can reduce the risk of fire during the cutting process and reduce the impact on the insulation effect of the first insulating layer, thereby reducing the risk of thermal runaway of the secondary battery.

[0177] In some embodiments, the electrode sheet is the electrode sheet in the secondary battery described in the first aspect of this application.

[0178] In some embodiments, the electrode sheet is a positive electrode sheet, the current collector is a positive current collector, the active layer is a positive active layer, and the electrode active material is a positive active material.

[0179] In some embodiments, the secondary battery also includes an electrolyte.

[0180] Electrolytes function to conduct ions between the positive and negative electrode plates. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0181] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0182] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0183] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butene carbonate Fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0184] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0185] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0186] In some embodiments, the secondary battery further includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0187] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0188] In some embodiments, the thickness of the isolation membrane is 6μm-40μm, and optionally 12μm-20μm.

[0189] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0190] In some embodiments, the secondary battery further includes an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0191] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0192] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0193] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0194] This application does not impose any particular restrictions on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape.

[0195] In some embodiments, the secondary battery 5 in FIG1 is a single battery cell. Referring to FIG6, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, the bottom plate and the side plate enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell may be one or more, which can be selected by those skilled in the art according to actual needs.

[0196] The secondary battery can be either battery module 4 or battery pack 1.

[0197] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0198] Figure 7 shows a battery module 4 as an example. Referring to Figure 7, in battery module 4, multiple battery cells can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells can be fixed in place using fasteners.

[0199] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells are housed.

[0200] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number based on the application and capacity of the battery pack.

[0201] Figures 8 and 9 illustrate a battery pack 1 as an example. Referring to Figures 8 and 9, the battery pack 1 may include a battery compartment and multiple battery modules 4 disposed within the battery compartment. The battery compartment includes an upper compartment 2 and a lower compartment 3, with the upper compartment 2 covering the lower compartment 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery compartment.

[0202] The seventh aspect of this application provides an electrical device comprising at least one of the following: the secondary battery described in the first aspect of this application, the secondary battery prepared by the preparation method described in the second aspect of this application, the electrode sheet described in the third aspect of this application, the secondary battery described in the fourth aspect of this application, the secondary battery prepared by the preparation method described in the fifth aspect of this application, and the electrode sheet described in the sixth aspect of this application.

[0203] Secondary batteries can be used as the power source for an electrical device or as the energy storage unit of that device. Electrical devices can include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices can be, for example, mobile phones and laptops; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0204] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0205] Figure 10 shows an example of an electrical device 6. This electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0206] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0207] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where the technology or conditions are not specified in the embodiments, they are performed according to the technology or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0208] Example 1

[0209] The preparation method of a secondary battery includes the following steps:

[0210] (1) Preparation of positive electrode sheet

[0211] (1.1) Preparation of insulating layer paste

[0212] Microcapsules, boehmite ceramic material, and PVDF binder were added in a mass ratio of 50:20:30, and NMP solvent was added and stirred evenly to obtain an insulating layer slurry (second slurry) with a viscosity of approximately 2000 mPa·s. The microcapsules had a volume average particle size Dv50 of 8 μm, an oxidized polyethylene wall, and a perfluorohexanone core, with the core accounting for 60% of the mass of the microcapsules.

[0213] (1.2) Preparation of positive electrode slurry

[0214] The positive electrode active material lithium iron phosphate (LiFePO4), conductive agent SP and binder PVDF are dispersed in solvent NMP at a mass ratio of 98:1:1 and mixed evenly to obtain the positive electrode slurry (first slurry);

[0215] (1.3) Preparation of insulating layer and positive electrode active layer

[0216] Using aluminum foil as the current collector, as shown in Figures 2 to 4, the main body 71 on both sides of the current collector 70 is pre-determined with a coating area 711 and a transition area 712. The positive electrode slurry is coated on the coating area 711, and the insulating layer slurry is coated on the transition area 712. After drying in an oven at a temperature of 100°C, a positive electrode active layer 701 and a first insulating layer 702 are formed. The width of the first insulating layer 702 is 10 mm, and the total thickness of the first insulating layer 702 on both sides is 80 μm. The total thickness of the positive electrode active layer 701 on both sides is 120 μm. The thickness of the first insulating layer 702 on each side of the current collector 70 is 40 μm, and the thickness of the positive electrode active layer 701 on each side of the current collector 70 is 60 μm.

[0217] After the obtained product is rolled, it is laser-diced along the cutting line 73. The die-cutting power is 300W and the frequency is 100kHz, forming tabs 72. During the laser die-cutting process, the oxidized polyethylene of the capsule wall in the first insulating layer 702 is heated and melted, flowing to the first end face 71a of the main body 71 and the third end face 72a of the tabs 72. A second insulating layer 703 is formed at the first end face 71a and the third end face 72a. The material of the second insulating layer 703 is oxidized polyethylene, resulting in a compaction density of 2.8 g / cm³. 3 The positive electrode 7. The thickness of the second insulating layer 703 is 155 nm.

[0218] (2) Preparation of negative electrode sheet

[0219] The negative electrode active material graphite, thickener sodium carboxymethyl cellulose, binder styrene-butadiene rubber, and conductive agent acetylene black were mixed in a mass ratio of 97:1:1:1. Deionized water was added, and the mixture was stirred in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on both sides of a copper foil. After the copper foil was dried at room temperature, it was transferred to a 120°C oven to dry for 1 hour. Then, it was cold-pressed and slit to obtain the negative electrode sheet.

[0220] (3) Separating membrane

[0221] A 12μm thick polypropylene separator membrane was selected.

[0222] (4) Preparation of electrolyte

[0223] The organic solvent was a mixture containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of EC:20:20:60. Thoroughly dried lithium salt LiPF6 was dissolved in the organic solvent and mixed thoroughly in an argon-atmosphere glove box with a water content of <10 ppm to obtain the electrolyte. The concentration of the lithium salt was 1 mol / L.

[0224] (5) Battery manufacturing

[0225] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. After being wound into a square bare cell, it is placed in an aluminum-plastic film, baked at 80°C to remove water, injected with the electrolyte, and sealed. After processes such as standing, hot and cold pressing, formation, clamping, and capacity testing, a lithium-ion secondary battery is obtained.

[0226] Examples 2 to 4

[0227] The preparation method of the secondary battery is basically the same as that in Example 1, except that the mass ratio of the core in the microcapsule in step (1.1) is changed, as shown in Table 1.

[0228] Examples 5 to 6

[0229] The preparation method of the secondary battery is basically the same as that in Example 1, except that the Dv50 of the microcapsules in step (1.1) is changed, as shown in Table 1.

[0230] Examples 7 to 8

[0231] The preparation method of the secondary battery is basically the same as that in Example 1, except that the thickness of the first insulating layer 702 on one side of the current collector 70 in step (1.3) is changed, as shown in Table 1.

[0232] Examples 9 to 10

[0233] The preparation method of the secondary battery is basically the same as that in Example 1, except that the core material of the microcapsule in step (1.1) is changed, as shown in Table 1.

[0234] Examples 11 to 13

[0235] The preparation method of the secondary battery is basically the same as that in Example 1, except that the capsule wall material of the microcapsule in step (1.1) is changed, as shown in Table 1.

[0236] Examples 14-15

[0237] The preparation method of the secondary battery is basically the same as that in Example 1, except that the mass ratio of microcapsules, ceramic material boehmite and binder PVDF in step (1.1) is changed, as shown in Table 1.

[0238] Comparative Example 1

[0239] The preparation method of the secondary battery is basically the same as that in Example 1, except that: microcapsules were not added when preparing the insulating layer slurry in step (1.3), and the ceramic material boehmite and the binder PVDF were added in a mass ratio of 70:30, as shown in Table 1.

[0240] Comparative Example 2

[0241] The preparation method of the secondary battery is basically the same as that in Example 1, except that: in step (1.1) when preparing the insulating layer slurry, the microcapsules are replaced with polyethylene oxide, and polyethylene oxide, ceramic material boehmite and binder PVDF are added in a mass ratio of 50:20:30, as shown in Table 1.

[0242] Test case

[0243] (1) Volume average particle size Dv50 test of microcapsules

[0244] Dv50 refers to the particle size corresponding to 50% of the volume distribution. The Dv50 of microcapsules can be tested according to GB / T19077-2016, with the following specific test steps: The particle sample can be dispersed at an appropriate concentration in a suitable liquid (e.g., deionized water) or gas through ultrasonic treatment or other methods. The sample is then tested using a Malvern Mastersizer-3000 instrument. The sample is passed through a monochromatic beam (usually a laser). When the light encounters the particles, it scatters at different angles. The scattered light is measured by a multi-element detector, and these values ​​related to the scattering pattern are stored for subsequent analysis. Through appropriate optical models and mathematical processes, these quantified scattering data are converted to obtain a series of discrete particle size ranges representing the percentage of particle volume relative to the total particle volume, thus yielding the particle size distribution.

[0245] (2) Boiling point test of the core

[0246] The boiling point of the core sample can be tested according to GB / T 616-2006. The specific test steps are as follows: (1) Put the sample to be tested into the distillation flask. Note that the amount of sample should not exceed half the volume of the distillation flask. At the same time, prevent the sample from evaporating or becoming contaminated during the loading process. (2) Install the distillation apparatus in the correct order. Ensure that all parts are tightly connected and leak-proof. The thermometer should be in the correct position, and the upper edge of its mercury bulb should be on the same horizontal plane as the lower edge of the side arm of the distillation flask. (3) Slowly heat the distillation flask and control the heating rate to make the distillation process proceed smoothly. Observe the thermometer reading. When the thermometer reading is stable, record the temperature at this time, which is the boiling point of the sample.

[0247] (3) Droplet melting point test of the capsule wall

[0248] The dropping melting point of thermoplastic polymers can be determined according to GB / T8026-2014. For example, a cooled temperature sensor is vertically immersed in the sample, allowing the sample to adhere to the sensor. Then, the sample is placed in a test tube and heated at the required rate to begin melting. The melting point is determined by the temperature of the sensor at which the first drop of sample falls onto it.

[0249] For example, the dropping point of a thermoplastic polymer can be determined based on the specific type of thermoplastic polymer. As an example, for crystalline thermoplastic polymers, the dropping point refers to the melting point of the crystalline thermoplastic polymer; for amorphous thermoplastic polymers, the dropping point refers to the glass transition temperature of the amorphous thermoplastic polymer.

[0250] (4) Thickness test of the first and second insulating layers

[0251] The thickness of the first insulating layer and the thickness of the second insulating layer can be measured using SEM.

[0252] (5) Test for fire ignition during the die-cutting process

[0253] Observe whether the positive electrode sheet catches fire during the die-cutting process of the positive electrode sheet in Examples 1 to 15, Comparative Example 1 and Comparative Example 2.

[0254] (6) End face contact resistance test

[0255] The contact resistance of the laser-diced positive electrode end face of Examples 1-15, Comparative Example 1, and Comparative Example 2 was tested using a resistance tester. Specifically, the positive electrode was clamped at one end of the resistance tester and a metal rod was clamped at the other end. The laser-diced end face of the positive electrode was then connected to the metal rod, and the value of the resistance tester was read to obtain the contact resistance of the laser-diced end face of the positive electrode.

[0256] (7) Test of fully charged negative electrode plate

[0257] (7.1) The end face of the positive electrode sheet after laser die-cutting of Examples 1 to 15, Comparative Example 1 and Comparative Example 2 was fully overlapped with the negative electrode sheet, and it was observed whether it caught fire.

[0258] (7.2) Using the first insulating layer of the positive electrode sheet of Examples 1 to 15, Comparative Example 1 and Comparative Example 2, overlap the negative electrode sheet and observe whether it catches fire.

[0259] The test results are shown in Table 2.

[0260] Table 1

[0261] Table 2

[0262] In Table 2, the contact resistance of the end face of the positive electrode sheet after laser die-cutting in Comparative Examples 1-2 is only 0.001 ohms (Ω), indicating that the end face of the positive electrode sheet in Comparative Examples 1-2 is not insulated. The contact resistance of the end face of the positive electrode sheet after laser die-cutting in Examples 1-15 is in the kiloohm range, indicating that the end face of the positive electrode sheet in Examples 1-15 is insulated and has a better insulation effect.

[0263] As shown in Tables 1 and 2, compared with Comparative Examples 1-2, the positive electrode sheets of Examples 1-15 did not ignite during laser die-cutting, and the first insulating layer did not ignite when fully overlapped with the negative electrode sheet. The insulation effect of the end face of the positive electrode sheet after laser die-cutting was better, and the end face of the positive electrode sheet after laser die-cutting did not ignite when fully overlapped with the negative electrode sheet. This indicates that the introduction of microcapsules into the first insulating layer of the positive electrode sheet in Examples 1-15 of this application can reduce the risk of fire during the die-cutting process, reduce the impact on the insulation effect of the first insulating layer, and reduce the risk of thermal runaway of the secondary battery. The thermoplastic polymer in the microcapsules melts when heated to form a second insulating layer, which can cover the burrs and reduce the risk of burrs overlapping with the negative electrode sheet, thereby further reducing the risk of thermal runaway of the battery.

[0264] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0265] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, comprising an electrode sheet, the electrode sheet comprising a current collector, an active layer, and a first insulating layer; The current collector includes a main body and an electrode tab protruding from the main body along a first direction. The main body includes a coating area and a transition area between the coating area and the electrode tab. The active layer is disposed on the surface of the coating area, and at least a portion of the first insulating layer is disposed on the surface of the transition area. The first insulating layer includes microcapsules, each microcapsule including a core and a wall covering at least a portion of the surface of the core. The core includes a fire extinguishing material, and the wall includes a thermoplastic polymer.

2. The secondary battery according to claim 1, wherein, The core portion of the microcapsule accounts for 60% to 80% of its mass.

3. The secondary battery according to any one of claims 1 to 2, wherein, The core portion of the microcapsule accounts for 65% to 70% of its mass.

4. The secondary battery according to any one of claims 1 to 3, wherein, The volume average particle size Dv50 of the microcapsules is 6μm to 15μm.

5. The secondary battery according to any one of claims 1 to 4, wherein, The thickness of the first insulating layer on one side of the current collector is 20 μm to 50 μm.

6. The secondary battery according to any one of claims 1 to 5, wherein, The current collector is provided with the first insulating layer on both sides.

7. The secondary battery according to any one of claims 1 to 6, wherein, The boiling point of the fire extinguishing material is less than or equal to 200°C.

8. The secondary battery according to any one of claims 1 to 7, wherein, The extinguishing materials include one or more of perfluorohexanone, fluoroalkyl extinguishing agents, and halon extinguishing agents.

9. The secondary battery according to claim 8, wherein, The secondary battery has one or more of the following features (1) to (2): (1) The fluoroalkane fire extinguishing agent includes one or more of heptafluoropropane and hexafluoropropane; (2) The halon fire extinguishing agent includes one or more of bromochlorodifluoromethane, bromotrifluoromethane and dibromotetrafluoroethane.

10. The secondary battery according to any one of claims 1 to 9, wherein, The thermoplastic polymer has a dropping melting point of 80°C to 200°C.

11. The secondary battery according to any one of claims 1 to 10, wherein, The thermoplastic polymer includes at least one of crystalline thermoplastic polymers and amorphous thermoplastic polymers.

12. The secondary battery according to claim 11, wherein, The secondary battery has one or more of the following features (1) to (2): (1) The crystalline thermoplastic polymer includes one or more of polyethylene, polypropylene, polyamide, polyimide and their respective modified polymers; (2) The amorphous thermoplastic polymer includes one or more of microcrystalline wax, polystyrene, polymethyl methacrylate, polyethyl methacrylate, polybutyl acrylate and their respective modified polymers.

13. The secondary battery according to any one of claims 1 to 12, wherein, The first insulating layer also includes an adhesive.

14. The secondary battery according to claim 13, wherein, In the first insulating layer, the mass ratio of the microcapsule to the adhesive is (50-70):(10-30).

15. The secondary battery according to any one of claims 1 to 14, wherein, The first insulating layer also includes a ceramic material.

16. The secondary battery according to claim 15, wherein, The secondary battery has one or more of the following features (1) to (3): (1) In the first insulating layer, the mass ratio of the microcapsule to the ceramic material is (50-70):(10-20); (2) The ceramic material includes one or more of boehmite and alumina; (3) The microcapsules in the first insulating layer are mixed with the ceramic material.

17. The secondary battery according to any one of claims 1 to 16, wherein, The first insulating layer includes a first portion and a second portion connected to the first portion. The first portion is disposed on the surface of the transition region, and the second portion extends along the first direction and is disposed on a portion of the surface of the tab.

18. The secondary battery according to claim 17, wherein, The electrode sheet further includes a second insulating layer; The main body includes a first end face and a second end face, the first end face being a sidewall adjacent to the transition region, and the second end face being a sidewall adjacent to the coating region. The second insulating layer is disposed on the first end face and / or the second end face of the main body; and / or, The electrode tab includes a third end face, which is a sidewall adjacent to the second portion of the first insulating layer, and the second insulating layer is disposed at the third end face.

19. The secondary battery according to claim 18, wherein, The secondary battery has one or more of the following features (1) to (2): (1) The second insulating layer comprises only the thermoplastic polymer, or the second insulating layer comprises the microcapsules; (2) The thickness of the second insulating layer is 50nm to 200nm.

20. The secondary battery according to any one of claims 1 to 19, wherein, The electrode sheet is a positive electrode sheet, the current collector is a positive current collector, the active layer is a positive active layer, and the electrode active material in the active layer is a positive active material.

21. The method for preparing the secondary battery according to claim 1, comprising the step of preparing the electrode sheet; The steps for preparing the electrode sheet include: A first slurry containing electrode active material is disposed in the coating area of ​​the main body of the current collector to form the active layer; A second slurry containing the microcapsules is disposed in the transition region of the main body of the current collector to form the first insulating layer; The current collector is cut, and at least part of the cutting line is set in the transition region to form an electrode tab protruding from the main body along the first direction, thereby preparing the electrode sheet.

22. The preparation method according to claim 21, wherein, The steps for cutting the current collector include: The laser processing tool is controlled to cut the current collector with the first insulating layer along the cutting line. The power of the laser processing tool is 50W to 300W and the frequency is 100kHz to 1000kHz.

23. The preparation method according to any one of claims 21 to 22, wherein, The electrode sheet is a positive electrode sheet, the current collector is a positive current collector, the active layer is a positive active layer, and the electrode active material is a positive active material.

24. An electrode sheet, comprising a current collector, an active layer, and a first insulating layer; The current collector includes a main body and an electrode tab protruding from the main body along a first direction. The main body includes a coating area and a transition area between the coating area and the electrode tab. The active layer is disposed on the surface of the coating area, and at least a portion of the first insulating layer is disposed on the surface of the transition area. The first insulating layer includes microcapsules, each microcapsule including a core and a wall covering at least a portion of the surface of the core. The core includes a fire extinguishing material, and the wall includes a thermoplastic polymer.

25. An electrical device comprising at least one of the secondary battery according to any one of claims 1 to 20, the secondary battery prepared by the preparation method according to any one of claims 21 to 23, and the electrode sheet according to claim 24.

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