Anti-cracking agent, pole piece, battery monomer, secondary battery and electric equipment

Abstract

The invention discloses an anti-cracking agent, a pole piece, a battery monomer, a secondary battery and electric equipment, and belongs to the technical field of secondary batteries. The anti-cracking agent includes a flexible segment and an anchoring group, the anchoring group having polarity. The anti-cracking agent contains an anchoring group with polarity and a flexible chain segment, when the anti-cracking agent is used for preparing the pole piece, the flexible chain segment has flexibility, the rigidity of the whole active material layer can be reduced, the anti-cracking effect is achieved, meanwhile, the flexible chain segment is beneficial to compatibility with a solvent in the preparation process, and the anti-cracking effect is improved. The anti-cracking agent can have a good dispersion effect in slurry in the preparation process of the active material layer, and the anchoring group with polarity has an anchoring effect on the active substance / binder, so that the dispersibility of the active substance and the binder is improved, the stress generated by drying shrinkage of the binder is reduced, and the service life of the active material layer is prolonged. Furthermore, the cracking probability of the thicker active material layer is reduced, the interface performance of an electrode assembly in the battery monomer is improved, and the interface dynamics and the cycle performance of the battery monomer are improved.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and more specifically, to an anti-cracking agent, electrode sheet, battery cell, secondary battery, and electrical equipment. Background Technology

[0002] Energy density is considered the biggest bottleneck restricting the development of current rechargeable batteries. Based on this, extensive research has been conducted on how to improve the energy density of rechargeable batteries. Among these efforts, increasing the thickness of the electrode sheets without affecting the battery's performance is a key direction for improving energy density.

[0003] However, as the electrode thickness increases, the processing difficulty also increases. Ultra-thick coated electrodes are prone to film cracking during the drying process. In addition, excessive film thickness can also lead to difficulties in electrolyte wetting and poor kinetics. Summary of the Invention

[0004] In view of the above problems, this application provides an anti-cracking agent, electrode sheet, battery cell, secondary battery, and electrical equipment, which can reduce the probability of cracking in thicker active material layers.

[0005] In a first aspect, this application provides a crack-resistant agent, the structural formula of which includes:

[0006]

[0007] Wherein, R1 is selected from at least one of H and C1-C6 alkyl groups;

[0008] R2 and R3 are each independently selected from H, C1-C8 alkyl, C1-C8 oxaalkyl, C1-C8 thiaalkyl, C3-C8 alkenyl, C3-C8 ester, C3-C8 sulfonate, and -(CH2). n -OH、

[0009] -(CH2) m At least one of -NH2, where n is a positive integer from 1 to 6, m is a positive integer from 1 to 6; and R2 and R3 are not both H;

[0010] R4 is selected from H, Li, Na, K, C1-C8 alkyl, C1-C8 ester, C1-C8 sulfonic acid, C1-C8 sulfonic acid salt, C1-C8 amino, C1-C8 sulfonate, C1-C8 alkoxy, C1-C8 alkylthio, 3-6 membered N-containing heterocyclic group, 3-6 membered O-containing heterocyclic group, phenyl, and -(CH2). p At least one of N(CH3)2, wherein p is a positive integer from 2 to 5;

[0011] R5 is selected from H, C1-C8 alkyl, C1-C8 ester, C1-C8 sulfonic acid, C1-C8 sulfonic acid salt, C1-C8 sulfonate, C1-C8 N-containing alkyl, C1-C8 alkoxy, C1-C8 alkylthio, 3-6 membered N-containing heterocyclic group, 3-6 membered O-containing heterocyclic group, -(CH2). q Si(OCH2CH3)3 and -(CH2) g -NH2 at least one, where q is a positive integer from 2 to 4 and g is a positive integer from 1 to 6;

[0012] R6 is selected from at least one of the halogen elements;

[0013] x, y, and z are all positive integers.

[0014] In the technical solution of this application embodiment, the anti-cracking agent contains polar anchoring groups such as carboxyl groups, ester groups, and amide groups, as well as flexible segments such as polyether segments. When used to prepare electrode sheets, the flexible segments are flexible, which can reduce the rigidity of the entire active material layer and achieve the anti-cracking effect. At the same time, the flexible segments are beneficial to the compatibility with solvents during the preparation process, so that the anti-cracking agent can have a good dispersion effect in the slurry during the preparation of the active material layer. The polar anchoring groups have an anchoring effect on the active material / binder, increasing the dispersibility of the active material and binder, reducing the stress generated by the drying shrinkage of the binder, thereby reducing the probability of cracking in thicker active material layers, improving the interfacial performance of electrode components in battery cells, and improving interfacial kinetics and cycle performance of battery cells. In addition, carboxyl groups, ester groups, or amide groups can produce a strong synergistic effect with the electrolyte in battery cells, which can increase the wetting of the active material layer by the electrolyte, thereby improving the kinetic performance of battery cells.

[0015] In some embodiments, R2 and R3 are independently selected from -CH3, -CH2CH3, -(CH2)2CH3, -(CH2)3CH3, -(CH2)4CH3, -(CH2)5CH3, -CH2OCH3, -CH2OCH2CH3, -CH2O(CH2)2CH3, -CH2O(CH2)3CH3, -CH2O(CH2)4CH3, -CH2O(CH2)5CH3, -CH2O(CH2)6CH3, -(CH2)2O(CH2)5CH3, -(CH2)3O(CH2)4CH3, and -CH2S. CH3, -CH2SCH2CH3, -CH2S(CH2)2CH3, -CH2S(CH2)3CH3, -CH2S(CH2)4CH3, -CH2S(CH2)5CH3, -CH2S(CH2)6CH3, -(CH2)2S(CH2)5CH 3. -(CH2)3S(CH2)4CH3, -CH2CH=CH2, -CH2CH=CHCH3, -CH2CH=CHCH2CH3, -CH2CH2CH=CHCH2CH3, -COOCH3, -COOCH2CH3, -COO(CH2)2 CH3, -COO(CH2)3CH3, -COO(CH2)4CH3, -CH2COOCH2CH3, -CH2COO(CH2)2CH3, -CH2COO(CH2)3CH3, -(CH2)2COO(CH2)3CH3, -SO3CH3 , -SO3CH2CH3, -SO3(CH2)2CH3, -SO3(CH2)3CH3, -SO3(CH2)4CH3, -CH2SO3CH2CH3, -CH2SO3(CH2)2CH3, -CH2SO3(CH2)3CH3, -(CH2 At least one of the following: -(CH2)2SO3CH2CH3, -(CH2)2SO3(CH2)2CH3, -SO2CH3, -SO2CH2CH3, -SO2(CH2)2CH3, -SO2(CH2)3CH3, -SO2(CH2)4CH3, -CH2SO2CH2CH3, -CH2SO2(CH2)2CH3, -CH2SO2(CH2)3CH3, -(CH2)2SO2CH3, -(CH2)2SO2CH2CH3 and -(CH2)2SO2(CH2)2CH3; and / or

[0016] R6 is selected from F, Cl, or Br.

[0017] In some embodiments, the anti-cracking agent comprises at least one of Formula 1 to Formula 8:

[0018] Formula 1: Where x, y, and z are independently selected from positive integers,

[0019] Formula 2: Where x, y, and z are independently selected from positive integers,

[0020] Formula 3: Where x, y, and z are independently selected from positive integers,

[0021] Formula 4: Where x, y, and z are independently selected from positive integers,

[0022] Formula 5: Where x, y, and z are independently selected from positive integers,

[0023] Formula 6: Where x, y, and z are independently selected from positive integers,

[0024] Formula 7: Where x, y, and z are independently selected from positive integers,

[0025] Formula 8: In this context, x, y, and z are each independently selected from positive integers.

[0026] In some embodiments, the weight-average molecular weight of the anti-cracking agent is 3000 to 10000.

[0027] In the above implementation process, the larger the weight average molecular weight of the anti-cracking agent, the better the dispersion effect of the conductive agent. The smaller the weight average molecular weight of the anti-cracking agent, the better it is to reduce its own viscosity and improve its reactivity. By controlling the weight average molecular weight of the anti-cracking agent to be 3000-10000, it is beneficial to improve the agglomeration of the conductive agent, reduce the probability of cracking of the active material layer, and enable the battery cell to have excellent electrical performance.

[0028] Secondly, this application provides an electrode sheet, which includes a current collector and an active material layer, wherein the active material layer is attached to the current collector; the active material layer includes the anti-cracking agent provided in the first aspect.

[0029] In some embodiments, the anti-cracking agent accounts for 0.1% to 0.5% of the mass of the active material layer.

[0030] In the above implementation process, the greater the amount of anti-cracking agent, the better it is for dispersing the conductive agent, which in turn helps to reduce the probability of cracking in the active material layer. The smaller the amount of anti-cracking agent, the better it is for the energy density of the battery cell. By controlling the mass ratio of anti-cracking agent in the active material layer to 0.1% to 0.5%, the energy density and electrochemical performance of the battery cell can be balanced.

[0031] In some embodiments, the anti-cracking agent accounts for 0.2% to 0.3% of the mass of the active material layer; and / or

[0032] The active material layer also includes active materials, which constitute 89.5% to 99.5% of the total mass of the active material layer; and / or

[0033] The active material layer also includes a conductive agent, which accounts for 0.3% to 4% of the total mass of the active material layer; and / or

[0034] The active material layer also includes a binder, which accounts for 1% to 6% of the total mass of the active material layer.

[0035] In some embodiments, the active material layer further includes an adhesive, the adhesive comprising a first adhesive and a second adhesive; and / or

[0036] The first adhesive comprises at least one of polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and fluorinated acrylate resin; and / or

[0037] The second adhesive includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and ethylene-chlorotrifluoroethylene copolymer; and / or

[0038] The weight-average molecular weight of the second adhesive is not less than ten million.

[0039] In the above implementation process, the combination of two adhesives can meet the requirements of the electrode manufacturing process. The first adhesive provides wetting and bonding to the active material, while the second adhesive can enhance the internal adhesion of the active material layer by winding and locking the particles (such as active materials, conductive agents, etc.) through fiber formation. This can ensure that the active material layer has a certain strength without sticking to the roller, and can ensure that the electrode does not break during high-speed belt travel.

[0040] In some embodiments, the first adhesive accounts for 0.5% to 4% of the active material layer by mass; and / or

[0041] The second binder accounts for 0.5% to 2% of the mass of the active material layer.

[0042] In the above implementation process, controlling the mass ratio of the first adhesive to be 0.5% to 4% and the mass ratio of the second adhesive to be 0.5% to 2% can better achieve the wetting, bonding and locking of the active material and the particles, thereby better enhancing the internal adhesion of the active material layer.

[0043] Thirdly, this application provides a battery cell, which includes the electrode provided in the second aspect.

[0044] Fourthly, this application provides a secondary battery, which includes the battery cell provided in the third aspect.

[0045] Fifthly, this application provides an electrical device, which includes a battery cell provided in the third aspect or a secondary battery provided in the fourth aspect. Attached Figure Description

[0046] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0047] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0048] Figure 2 This is an exploded structural diagram of a secondary battery provided in some embodiments of this application;

[0049] Figure 3 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0050] Figure 4 Exploded views of a single battery cell provided in some embodiments of this application;

[0051] Figure 5 This is a first structural schematic diagram of the positive electrode sheet provided in some embodiments of this application;

[0052] Figure 6 This is a schematic diagram of the second structure of the positive electrode sheet provided in some embodiments of this application;

[0053] Figure 7 Infrared detection results of anti-cracking agents provided in some embodiments of this application;

[0054] Figure 8 A flowchart illustrating the preparation method of the electrode sheet provided in some embodiments of this application;

[0055] Figure 9 Schematic diagrams of electrode cracking provided in some embodiments of this application;

[0056] Figure 10 This is a schematic diagram of the morphology of an electrode sheet without cracking, provided in some embodiments of this application.

[0057] The reference numerals in the detailed embodiments are as follows:

[0058] 1000 - Vehicle; 100 - Secondary battery; 200 - Motor; 300 - Controller; 10 - Housing; 11 - Accommodation space; 12 - First part; 13 - Second part; 20 - Battery cell; 21 - Shell; 211 - Opening; 22 - End cap assembly; 221 - End cap; 222 - Electrode terminal; 23 - Electrode assembly; 231 - Positive electrode sheet; 2311 - Positive current collector; 2312 - Positive active material layer; 24 - Current collector component; 25 - Insulation protection component. Detailed Implementation

[0059] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0061] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0062] 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 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.

[0063] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0064] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0065] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0066] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0067] Currently, judging from market trends, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of power battery applications, market demand is also constantly increasing.

[0068] Power batteries can be either lithium-ion or sodium-ion rechargeable batteries, which have wide applications in portable electronic devices, electric vehicles, and other fields. Energy density is considered the biggest bottleneck restricting the current development of rechargeable batteries. Based on this, extensive research has been conducted on how to improve the energy density of rechargeable batteries. Among these efforts, increasing the thickness of the electrode sheets without affecting the battery's performance is a key direction for improving energy density.

[0069] However, as the electrode thickness increases, the processing difficulty also increases. Ultra-thick coated electrodes are prone to film cracking during the drying process. In addition, excessive film thickness can also lead to difficulties in electrolyte wetting and poor kinetics.

[0070] To improve the energy density of secondary batteries, silicon-based materials are usually added to the negative electrode as negative electrode active materials. However, silicon-based materials have a low initial efficiency, so they are not used in combination with positive electrode active materials with high initial efficiency, such as lithium iron phosphate materials, to improve the energy density of the battery.

[0071] Based on the above considerations, in order to reduce the probability of cracking in thicker active material layers, this application proposes a battery cell, which includes an electrode, the electrode including a current collector and an active material layer, the active material layer being attached to the current collector; the active material layer including an anti-cracking agent, the anti-cracking agent including flexible segments and anchoring groups, the anchoring groups being polar.

[0072] In such a battery cell, an anti-cracking agent composed of polar anchoring groups and flexible segments is added to the active material layer. The flexible segments are flexible, which can reduce the rigidity of the entire active material layer and play an anti-cracking role. At the same time, the flexible segments are conducive to the compatibility with solvents during the preparation process, so that the anti-cracking agent can have a good dispersion effect in the slurry during the preparation of the active material layer. The polar anchoring groups anchor the active material / binder, increase the dispersibility of the active material and binder, reduce the stress generated by the drying shrinkage of the binder, and thus reduce the probability of cracking in the thicker active material layer. This improves the interfacial performance of the electrode components in the battery cell and enhances the interfacial kinetics and cycle performance of the battery cell.

[0073] The battery cell can be used, but is not limited to, in electrical equipment such as vehicles, ships, or aircraft. The power system of such electrical equipment can be composed of a secondary battery or similar device disclosed in this application.

[0074] This application provides an electrical device that uses a battery as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0075] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device according to an embodiment of this application.

[0076] Please refer to Figure 1 , Figure 1This is a schematic diagram of the structure of a vehicle provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A secondary battery 100 is installed inside the vehicle 1000, and the secondary battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The secondary battery 100 can be used to power the vehicle 1000; for example, the secondary battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 300 and a motor 200. The controller 300 is used to control the secondary battery 100 to supply power to the motor 200, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0077] In some embodiments of this application, the secondary battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0078] In this application, the secondary battery 100 can refer to a single battery cell 20, or it can refer to a single physical module comprising multiple battery cells 20 to provide higher voltage and capacity, which can be in the form of a battery pack, battery module, etc. The secondary battery 100 may include a housing 10 for encapsulating multiple battery cells 20, and the housing 10 can prevent liquids or other foreign objects from affecting the charging or discharging of the battery cells 20.

[0079] Figure 2 This is an exploded structural diagram of a secondary battery 100 provided in some embodiments of this application. Please refer to... Figure 2 The secondary battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10.

[0080] The housing 10 provides a receiving space 11 for the battery cell 20. In some embodiments, the housing 10 may include a first portion 12 and a second portion 13, which overlap each other to define the receiving space 11 for accommodating the battery cell 20. Of course, the connection between the first portion 12 and the second portion 13 may be sealed by a sealant (not shown), such as a sealing ring, sealant, etc.

[0081] The first part 12 and the second part 13 can be of various shapes, such as cuboids, cylinders, etc. The first part 12 can be a hollow structure with an opening on one side to form a cavity for accommodating the battery cell 20, and the second part 13 can also be a hollow structure with an opening on one side to form a cavity for accommodating the battery cell 20. When the opening side of the second part 13 covers the opening side of the first part 12, a housing 10 with an accommodating space 11 is formed. Of course, as... Figure 2As shown, the first part 12 can also be a hollow structure with an opening on one side, and the second part 13 can be a plate-like structure. The second part 13 covers the opening side of the first part 12, thus forming a box 10 with a accommodating space 11.

[0082] In the secondary battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed configuration, and then the whole assembly of multiple battery cells 20 is housed in the housing 10. Alternatively, multiple battery cells 20 can first be connected in series, parallel, or in a mixed configuration to form a battery module, and then multiple battery modules can be connected in series, parallel, or in a mixed configuration to form a whole assembly, which is then housed in the housing 10. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes. Figure 2 An example is shown where the battery cell 20 is square.

[0083] In some embodiments, the secondary battery 100 may further include a busbar (not shown), through which multiple battery cells 20 can be electrically connected to each other to achieve series, parallel, or mixed connection of multiple battery cells 20.

[0084] Figure 3 This is a schematic diagram of the structure of a battery cell 20 provided in some embodiments of this application. Figure 4 Exploded views of a battery cell 20 provided for some embodiments of this application. Please refer to... Figure 3 and Figure 4 The battery cell 20 may include a housing 21, an end cap assembly 22, and an electrode assembly 23. The housing 21 has an opening 211, the electrode assembly 23 is housed within the housing 21, and the end cap assembly 22 is used to seal the opening 211.

[0085] The shape of the outer casing 21 can be determined according to the specific shape of the electrode assembly 23. For example, if the electrode assembly 23 is a cuboid structure, the outer casing 21 can be a cuboid structure. Figure 3 and Figure 4 An example is shown where the housing 21 and electrode assembly 23 are square.

[0086] The outer shell 21 can also be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc. This application embodiment does not impose any special restrictions on this.

[0087] The end cap assembly 22 includes an end cap 221 and electrode terminals 222. The end cap assembly 22 is used to seal the opening 211 of the housing 21 to form a sealed mounting space (not shown) for accommodating the electrode assembly 23. The mounting space also accommodates an electrolyte, such as an electrolyte solution. As a component that outputs electrical energy to the electrode assembly 23, the end cap assembly 22 has electrode terminals 222 for electrical connection to the electrode assembly 23, specifically, the electrode terminals 222 are electrically connected to the tabs of the electrode assembly 23. For example, the electrode terminals 222 and the tabs are connected via a current collector 24 to achieve the electrical connection between the electrode terminals 222 and the tabs.

[0088] It should be noted that the opening 211 of the outer casing 21 can be one or two. If the outer casing 21 has one opening 211, the end cap assembly 22 can also be one, and two electrode terminals 222 can be provided in the end cap assembly 22. The two electrode terminals 222 are used to electrically connect to the positive electrode tab and the negative electrode tab of the electrode assembly 23, respectively. If the outer casing 21 has two openings 211, for example, the two openings 211 are located on opposite sides of the outer casing 21, the end cap assembly 22 can also be two, and the two end cap assemblies 22 respectively cover the two openings 211 of the outer casing 21. In this case, the electrode terminal 222 in one end cap assembly 22 can be a positive electrode terminal, used to electrically connect to the positive electrode tab of the electrode assembly 23; the electrode terminal 222 in the other end cap assembly 22 can be a negative electrode terminal, used to electrically connect to the negative electrode plate of the electrode assembly 23.

[0089] In some embodiments, such as Figure 4 As shown, the battery cell 20 may further include an insulating protective member 25 fixed to the outer periphery of the electrode assembly 23. The insulating protective member 25 is used to insulate and isolate the electrode assembly 23 from the housing 21. Exemplarily, the insulating protective member 25 is adhesive tape bonded to the outer periphery of the electrode assembly 23. In some embodiments, there are multiple electrode assemblies 23, and the insulating protective member 25 surrounds the outer periphery of multiple electrode assemblies 23, forming a single integral structure to maintain the structural stability of the electrode assembly 23.

[0090] The electrode assembly 23 includes a positive electrode 231, a negative electrode 231, and a separator. The electrode assembly 23 can be a wound electrode assembly 23 or a stacked electrode assembly 23, and the embodiments of this application are not limited thereto.

[0091] The positive electrode 231 includes a positive current collector 2311 and a positive active material layer 2312. The positive active material layer 2312 is coated on the surface of the positive current collector 2311. The positive current collector 2311 without the positive active material layer 2312 protrudes from the positive current collector 2311 with the positive active material layer 2312 coated. The positive current collector 2311 without the positive active material layer 2312 coated serves as the positive electrode tab.

[0092] In some embodiments, the positive current collector 2311 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 polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0093] In some embodiments, when the secondary battery 100 is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 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 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0094] In some embodiments, when the secondary battery 100 is a sodium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for sodium-ion batteries. As examples, at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds may be used. 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.

[0095] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x M02, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, 0 <x≤1。

[0096] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (Y04). n- The price state.

[0097] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0098] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) n+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (Y04). n-The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) n+ The valence state; the halogen can be at least one of F, Cl and Br.

[0099] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3, NaM'PO4F (where M' is one or more of V, Fe, Mn, and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0100] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a Me b Me' c (CN)6 where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0101] In some embodiments, the positive electrode active material layer 2312 may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0102] In some embodiments, the positive electrode active material layer 2312 may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, the positive electrode 231 can be prepared by dispersing the components used to prepare the positive electrode 231, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g. N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive current collector 2311, and after drying, cold pressing and other processes, the positive electrode 231 can be obtained.

[0104] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode current collector. The negative electrode current collector without the negative electrode active material layer protrudes from the negative electrode current collector with the negative electrode active material layer. The negative electrode current collector without the negative electrode active material layer serves as the negative electrode tab.

[0105] 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 polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one 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 be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one 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.

[0107] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one 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).

[0108] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0110] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0111] In other embodiments, the current collector of the negative electrode sheet may also include a current collector body and a base coating. The base coating may be disposed on at least one side of the current collector body. The base coating basically does not contain negative electrode active material, but may contain a small amount of carbon material. However, the carbon material forms a thin coating and cannot function as a negative electrode active material. In this embodiment, the negative electrode sheet can be an electrode sheet without a negative electrode active material layer. For a negative electrode sheet without a negative electrode active material layer, when the current collector of the negative electrode sheet does not contain a base coating, the film layer of the negative electrode sheet can be disposed on the surface of at least one side of the current collector body; when the current collector of the negative electrode sheet includes a base coating, the film layer of the negative electrode sheet can be disposed on the surface of the base coating away from the current collector body.

[0112] In some implementations, in order to ensure that a large current can pass through without melting, there are multiple positive electrode tabs stacked together, and multiple negative electrode tabs stacked together.

[0113] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0114] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can 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 can be the same or different, without particular limitation.

[0115] The electrolyte acts as a conductor of ions between the positive electrode 231 and the negative electrode. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0116] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0117] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0118] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, 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.

[0119] 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.

[0120] This application provides an anti-cracking agent, the structural formula of which includes:

[0121]

[0122] Wherein, R1 is selected from at least one of H and C1-C6 alkyl groups;

[0123] R2 and R3 are each independently selected from H, C1-C8 alkyl, C1-C8 oxaalkyl, C1-C8 thiaalkyl, C3-C8 alkenyl, C3-C8 ester, C3-C8 sulfonate, and -(CH2). n -OH、

[0124] -(CH2) m At least one of -NH2, where n is a positive integer from 1 to 6, m is a positive integer from 1 to 6; and R2 and R3 are not both H;

[0125] R4 is selected from H, Li, Na, K, C1-C8 alkyl, C1-C8 ester, C1-C8 sulfonic acid, C1-C8 sulfonic acid salt, C1-C8 amino, C1-C8 sulfonate, C1-C8 alkoxy, C1-C8 alkylthio, 3-6 membered N-containing heterocyclic group, 3-6 membered O-containing heterocyclic group, phenyl, and -(CH2). p At least one of N(CH3)2, wherein p is a positive integer from 2 to 5;

[0126] R5 is selected from H, C1-C8 alkyl, C1-C8 ester, C1-C8 sulfonic acid, C1-C8 sulfonic acid salt, C1-C8 sulfonate, C1-C8 N-containing alkyl, C1-C8 alkoxy, C1-C8 alkylthio, 3-6 membered N-containing heterocyclic group, 3-6 membered O-containing heterocyclic group, -(CH2). q Si(OCH2CH3)3 and -(CH2)g -NH2 at least one, where q is a positive integer from 2 to 4 and g is a positive integer from 1 to 6;

[0127] R6 is selected from at least one of the halogen elements;

[0128] x, y, and z are all positive integers.

[0129] This anti-cracking agent contains polar anchoring groups such as carboxyl, ester, and amide groups, as well as flexible segments such as polyether segments. When used in electrode preparation, the flexible segments reduce the rigidity of the entire active material layer, thus preventing cracking. Simultaneously, the flexible segments improve solvent compatibility during preparation, allowing the anti-cracking agent to disperse well in the slurry during active material layer preparation. The polar anchoring groups anchor the active material / binder, increasing their dispersibility and reducing stress caused by binder drying shrinkage. This reduces the probability of cracking in thicker active material layers, improves the interfacial performance of electrode components in battery cells, and enhances interfacial kinetics and cycle performance of the battery cell. Furthermore, carboxyl, ester, or amide groups can have a strong synergistic effect with the electrolyte in the battery cell, increasing electrolyte wetting of the active material layer and further improving the kinetic performance of the battery cell.

[0130] The anti-cracking agent can be applied to the battery cell 20. Specifically, the battery cell 20 includes an electrode, which includes a current collector and an active material layer containing the anti-cracking agent. The active material layer is attached to the current collector.

[0131] The current collector can be either a positive current collector 2311 or a negative current collector, and the corresponding active material layer can be either a positive active material layer 2312 or a negative active material layer. The active material layer can be attached to either one side of the current collector or both sides simultaneously. The following section uses the positive electrode 231 as an example for further explanation; please refer to the following text. Figure 5 In one embodiment, a positive electrode active material layer 2312 is disposed on one surface of the positive electrode current collector 2311; please continue reading Figure 6 In another embodiment, a positive electrode active material layer 2312 is provided on both surfaces of the positive electrode current collector 2311.

[0132] The groups in the anti-cracking agent can be detected by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) 1H and 1C spectroscopy. For example, the specific process of NMR 1H and 1C spectroscopy is as follows: use deuterated solvents such as CCl4 and deuterated chloroform to dissolve the sample and measure H1-NMR and C13-NMR.

[0133] Optionally, R2 and R3 are independently selected from -CH3, -CH2CH3, -(CH2)2CH3, -(CH2)3CH3, -(CH2)4CH3, -(CH2)5CH3, -CH2OCH3, -CH2OCH2CH3, -CH2O(CH2)2CH3, -CH2O(CH2)3CH3, -CH2O(CH2)4CH3, -CH2O(CH2)5CH3, -CH2O(CH2)6CH3, -(CH2)2O(CH2)5CH3, -(CH2)3O(CH2)4CH3, and -CH2SCH. 3. -CH2SCH2CH3, -CH2S(CH2)2CH3, -CH2S(CH2)3CH3, -CH2S(CH2)4CH3, -CH2S(CH2)5CH3, -CH2S(CH2)6CH3, -(CH2)2S(CH2)5CH3 , -(CH2)3S(CH2)4CH3, -CH2CH=CH2, -CH2CH=CHCH3, -CH2CH=CHCH2CH3, -CH2CH2CH=CHCH2CH3, -COOCH3, -COOCH2CH3, -COO(CH2)2 CH3, -COO(CH2)3CH3, -COO(CH2)4CH3, -CH2COOCH2CH3, -CH2COO(CH2)2CH3, -CH2COO(CH2)3CH3, -(CH2)2COO(CH2)3CH3, -SO3CH 3. -SO3CH2CH3, -SO3(CH2)2CH3, -SO3(CH2)3CH3, -SO3(CH2)4CH3, -CH2SO3CH2CH3, -CH2SO3(CH2)2CH3, -CH2SO3(CH2)3CH3, -(CH 2) At least one of 2SO3CH3, -(CH2)2SO3CH2CH3, -(CH2)2SO3(CH2)2CH3, -SO2CH3, -SO2CH2CH3, -SO2(CH2)2CH3, -SO2(CH2)3CH3, -SO2(CH2)4CH3, -CH2SO2CH2CH3, -CH2SO2(CH2)2CH3, -CH2SO2(CH2)3CH3, -(CH2)2SO2CH3, -(CH2)2SO2CH2CH3 and -(CH2)2SO2(CH2)2CH3.

[0134] Optionally, R6 is selected from F, Cl, or Br.

[0135] Furthermore, it includes at least one of Formulas 1 to 8:

[0136] Formula 1: Where x, y, and z are independently selected from positive integers,

[0137] Formula 2: Where x, y, and z are independently selected from positive integers,

[0138] Formula 3: Where x, y, and z are independently selected from positive integers,

[0139] Formula 4: Where x, y, and z are independently selected from positive integers,

[0140] Formula 5: Where x, y, and z are independently selected from positive integers,

[0141] Formula 6: Where x, y, and z are independently selected from positive integers,

[0142] Formula 7: Where x, y, and z are independently selected from positive integers,

[0143] Formula 8: In this context, x, y, and z are each independently selected from positive integers.

[0144] The following is based on Taking the preparation of [a specific ingredient] as an example, we will explain the preparation of the anti-cracking agent in detail. and Add the reagents in a flask at a molar ratio of 1:1. The catalyst is DMAP, the solvent is CH2Cl2, and the dehydrating agent is DCC. The reaction is then carried out under a N2 atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 is then reacted with… The mixtures were combined in a molar ratio of 1:1, with CuCl as the catalyst and butanone and isopropanol (volume ratio 7:3) as the solvent. The reaction temperature was 90℃, and the reaction time was 24 h to synthesize intermediate 2. Intermediate 2 and... The mixture was prepared by mixing ingredients in a 1:1 molar ratio, using CuCl as the catalyst and isopropanol as the solvent. The reaction temperature was 40℃, and the reaction time was 24 h. The product was obtained by precipitation with petroleum ether and filtration. Infrared spectroscopy was performed on the obtained product, and the results are as follows: Figure 7 As shown, this preparation method yields the substance. It should be noted that crack inhibitors of different molecular weights can be prepared by adjusting the mixing ratio of raw materials, controlling the temperature range, and time. Furthermore, different R1, R2, R3, R4, R5, and R6 groups on the crack inhibitor can be obtained by substituting or selecting these groups based on the raw materials, or by substituting them after the crack inhibitor has been prepared.

[0145] In the technical solution of this application embodiment, the weight-average molecular weight of the anti-cracking agent is 3000-10000.

[0146] Weight-average molecular weight (MAM) is the statistical average molecular weight of a polymer by mass, that is, the molecular weight averaged per unit weight. Methods for determining MAM include light scattering and gel permeation chromatography.

[0147] The higher the weight-average molecular weight of the anti-cracking agent, the better it is for the dispersion effect of the conductive agent. The lower the weight-average molecular weight of the anti-cracking agent, the better it is for reducing its own viscosity and improving its reactivity. By controlling the weight-average molecular weight of the anti-cracking agent to be 3000-10000, it is beneficial to improve the agglomeration of the conductive agent, reduce the probability of cracking of the active material layer, and enable the battery cell 20 to have excellent electrical performance.

[0148] For example, the weight average molecular weight of the anti-cracking agent can be 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500 or 10000, etc., or it can be any value in the range of 3000 to 10000.

[0149] In the technical solution of this application embodiment, the mass ratio of the anti-cracking agent in the active material layer is 0.1% to 0.5%.

[0150] Furthermore, the anti-cracking agent accounts for 0.2% to 0.3% of the mass of the active material layer.

[0151] The greater the amount of anti-cracking agent, the better it is for dispersing the conductive agent, which in turn helps reduce the probability of cracking in the active material layer. The smaller the amount of anti-cracking agent, the better it is for the energy density of the battery cell 20. By controlling the mass ratio of the anti-cracking agent in the active material layer to 0.1% to 0.5%, the energy density and electrochemical performance of the battery cell 20 can be balanced.

[0152] For example, the mass percentage of the anti-cracking agent in the active material layer can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, etc., or any value within the range of 0.1% to 0.5%.

[0153] In the technical solution of this application embodiment, the active material layer further includes active material, and the mass percentage of active material in the active material layer is 89.5% to 99.5%.

[0154] For example, the mass percentage of the active material in the active material layer can be 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or 99.5%, etc., or it can be any value in the range of 89.5% to 99.5%.

[0155] In the technical solution of this application embodiment, the active material layer further includes a conductive agent, and the mass percentage of the conductive agent in the active material layer is 0.3% to 4%.

[0156] For example, the mass percentage of the conductive agent in the active material layer can be 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or 4%, or any value within the range of 0.3% to 4%.

[0157] In the technical solution of this application embodiment, the active material layer further includes an adhesive, and the mass percentage of the adhesive in the active material layer is 1% to 6%.

[0158] For example, the mass percentage of the adhesive in the active material layer can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6%, or any value within the range of 1% to 6%.

[0159] In the technical solution of this application embodiment, the active material layer further includes an adhesive, which includes a first adhesive and a second adhesive. The combined use of these two adhesives satisfies the electrode manufacturing process. The first adhesive provides wetting and bonding to the active material, while the second adhesive can enhance the internal adhesion of the active material layer by fiber winding and locking the particles (e.g., active material, conductive agent, etc.). This ensures that the active material layer has a certain strength without sticking to the rollers, preventing the electrode from breaking during high-speed belt conveying. Specifically, the first adhesive includes at least one of polyvinylidene fluoride, polyvinylidene fluoride-tetrafluoroethylene-propylene terpolymer, polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and fluorinated acrylate resin; the second adhesive includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and ethylene-chlorotrifluoroethylene copolymer; and the weight-average molecular weight of the second adhesive is not less than ten million. By controlling the weight-average molecular weight of the second adhesive to be not less than ten million, the second adhesive can achieve better fiber winding and locking of the particles.

[0160] Furthermore, the first binder accounts for 0.5% to 4% of the mass of the active material layer, and the second binder accounts for 0.5% to 2% of the mass of the active material layer. By controlling the mass percentage of the first binder to 0.5% to 4% and the mass percentage of the second binder to 0.5% to 2%, the wetting, bonding, and particle locking of the active material can be better achieved, thereby better enhancing the internal adhesion of the active material layer.

[0161] For example, the mass percentage of the first adhesive in the active material layer can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or 4%, or any value within the range of 0.5% to 4%. The mass percentage of the second adhesive in the active material layer can be 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, or 2%, or any value within the range of 0.5% to 2%.

[0162] Having introduced the anti-cracking agent and its application to the corresponding electrode structure in batteries, the preparation method of the electrode will now be described in detail.

[0163] The preparation method of the electrode includes the following steps: preparing anti-cracking agent, active material, conductive agent and binder into agglomerated material, extruding and hot pressing the obtained agglomerated material to form a thick film, rolling the obtained thick film to thin it and then compounding it with current collector, and drying it to obtain the electrode. The anti-cracking agent includes polyether segments and anchoring groups, and the anchoring groups are polar.

[0164] This method involves adding a crack-resistant agent composed of polar anchoring groups and polyether segments to the active material layer. The polyether segments are flexible, which reduces the rigidity of the entire active material layer and prevents cracking. At the same time, the polyether segments improve the compatibility with solvents during the preparation process, allowing the crack-resistant agent to have a good dispersion effect in the slurry during the preparation of the active material layer. The polar anchoring groups anchor the active material / binder, increasing the dispersibility of the active material and binder, reducing the stress generated by the drying shrinkage of the binder, thereby reducing the probability of cracking in thicker active material layers, improving the interfacial performance of the electrode assembly 23 in the battery cell 20, and improving the interfacial kinetics and cycle performance of the battery cell 20.

[0165] Figure 8 For flowcharts of the electrode preparation methods provided in some embodiments of this application, please refer to [link / reference]. Figure 8 This application provides a method for preparing an electrode sheet, the method comprising:

[0166] S110, Preparation of adhesive solution: The anti-cracking agent and the first binder are dispersed in a solvent to form an adhesive solution.

[0167] The solvent can be one or more of dimethyl glutarate and N-methylpyrrolidone. The solid content of the adhesive solution can be 3% to 20%.

[0168] S120, Preparation of agglomerated material: The active material, conductive agent, second binder and adhesive are kneaded together to form agglomerated material.

[0169] The solid content of the lumpy material is 70%–95%. Kneading can be performed using an internal mixer, kneader, or twin-screw extruder. The screw element of the twin-screw extruder can be a combination of one or more of the following: threaded parts, meshing blocks, and toothed discs, to fully balance shearing, mixing, and conveying capacity.

[0170] S130, Preparation of thick film: The obtained agglomerated material is extruded or hot-pressed to obtain a thick film.

[0171] Thick film preparation equipment can include twin-screw extruders, hydraulic extruders, plunger extruders, hot presses, and open mills. The screw element of a twin-screw extruder can be composed of one or more of threaded components, meshing blocks, and toothed discs, to fully balance shearing, mixing, and conveying capabilities.

[0172] S140, Preparation of electrode sheet: The obtained thick film sheet is thinned by rolling and then combined with the current collector, and then dried to obtain the electrode sheet.

[0173] The above preparation process requires only a small amount of solvent. Therefore, the extruded film can greatly promote particle slippage during the rolling thinning process. The solvent acts like a "lubricant," making the film less prone to over-rolling, resulting in a more flexible film with better processing performance. The electrode is also easier to compact, facilitating the fabrication of thicker electrodes and achieving high-energy-density batteries. The amount of solvent added to the formulation is far lower than that used in industry wet coating processes, significantly reducing drying energy consumption and environmental pollution. Of course, wet coating processes can also be used to prepare the electrode in other embodiments.

[0174] After preparing the electrode sheet (which can be a positive electrode sheet and / or a negative electrode sheet), the first separator, the positive electrode sheet, the second separator, and the negative electrode sheet are stacked in sequence, wound to form a wound flat structure, and then hot-pressed to obtain a wound electrode assembly; or, after preparing the electrode sheet (which can be a positive electrode sheet and / or a negative electrode sheet), the positive electrode sheet, the separator, the negative electrode sheet, the separator, and so on, are stacked in sequence to form a stacked electrode assembly 23.

[0175] The electrode assembly 23 can be used to prepare a battery cell 20, which can be used to prepare a secondary battery 100 and provide electrical energy to electrical devices.

[0176] The following examples will describe one or more embodiments in more detail. Of course, these examples do not limit the scope of the one or more embodiments.

[0177] Preparation Example 1

[0178] A crack-resistant agent, the preparation process of which is as follows:

[0179] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 90℃, and the reaction time was 24 h to synthesize intermediate 2. Intermediate 2 and... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 40°C for 24 hours. The product was obtained by precipitation with petroleum ether and filtration.

[0180] The structural formula of the anti-cracking agent is as follows:

[0181]

[0182] Preparation Example 2

[0183] A crack-resistant agent, the preparation process of which is as follows:

[0184] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 95℃, and the reaction time was 26 h to synthesize intermediate 2. Intermediate 2 was then combined with... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 50°C for 22 hours. The product was obtained by precipitation with petroleum ether and filtration.

[0185] The structural formula of the anti-cracking agent is as follows:

[0186]

[0187] Preparation Example 3

[0188] A crack-resistant agent, the preparation process of which is as follows:

[0189] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total amount of reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 44 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 85℃, and the reaction time was 22 h to synthesize intermediate 2. Intermediate 2 and... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 40°C for 20 hours. The product was obtained by precipitation with petroleum ether and filtration.

[0190] The structural formula of the anti-cracking agent is as follows:

[0191]

[0192] Preparation Example 4

[0193] A crack-resistant agent, the preparation process of which is as follows:

[0194] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total amount of reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 44 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 85℃, and the reaction time was 22 h to synthesize intermediate 2. Intermediate 2 and... The mixture is prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 50°C for 30 hours. The product is obtained by precipitation with petroleum ether and filtration.

[0195] The structural formula of the anti-cracking agent is as follows:

[0196]

[0197] Preparation Example 5

[0198] A crack-resistant agent, the preparation process of which is as follows:

[0199] Will and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... (x = 40) Mixed in a molar ratio of 1:1, with CuCl as the catalyst (added at 1% of the total reactants), and butanone and isopropanol as the solvent (volume ratio 7:3). The reaction temperature was 85℃, and the reaction time was 26 h to synthesize intermediate 2; intermediate 2 and... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 50°C for 32 hours. The product was obtained by precipitation with petroleum ether and filtration.

[0200] The structural formula of the anti-cracking agent is as follows:

[0201]

[0202] Preparation Example 6

[0203] A crack-resistant agent, the preparation process of which is as follows:

[0204] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 90℃, and the reaction time was 28 h to synthesize intermediate 2. Intermediate 2 and... The mixture is prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 50°C for 30 hours. The product is obtained by precipitation with petroleum ether and filtration.

[0205] The structural formula of the anti-cracking agent is as follows:

[0206]

[0207] Preparation Example 7

[0208] A crack-resistant agent, the preparation process of which is as follows:

[0209] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a molar ratio of 1:1, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 85℃, and the reaction time was 24 h to synthesize intermediate 2. Intermediate 2 and... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 60°C for 36 hours. The product was obtained by precipitation with petroleum ether and filtration.

[0210] The structural formula of the anti-cracking agent is as follows:

[0211]

[0212] Preparation Example 8

[0213] A crack-resistant agent, the preparation process of which is as follows:

[0214] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total amount of reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 52 hours to synthesize intermediate 1. Intermediate 1 and... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 95℃, and the reaction time was 28 h to synthesize intermediate 2. Intermediate 2 and... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 60°C for 28 hours. The product was obtained by precipitation with petroleum ether and filtration.

[0215] The structural formula of the anti-cracking agent is as follows:

[0216]

[0217] Preparation Example 9

[0218] A crack-resistant agent, the preparation process of which is as follows:

[0219] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 90℃, and the reaction time was 24 h to synthesize intermediate 2. Intermediate 2 and... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 40°C for 14.4 h. The product was obtained by precipitation with petroleum ether and filtration.

[0220] The structural formula of the anti-cracking agent is as follows:

[0221]

[0222] Preparation Example 10

[0223] A crack-resistant agent, the preparation process of which is as follows:

[0224] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 90℃, and the reaction time was 24 h to synthesize intermediate 2. Intermediate 2 and... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 40°C for 19.2 h. The product was obtained by precipitation with petroleum ether and filtration.

[0225] The structural formula of the anti-cracking agent is as follows:

[0226]

[0227] Preparation Example 11

[0228] A crack-resistant agent, the preparation process of which is as follows:

[0229] Will (x is 40) and The reactants were added to a flask at a molar ratio of 1:1. The catalyst was DMAP (4-dimethylaminopyridine, added at 1% of the total reactants), the solvent was CH2Cl2, and the dehydrating agent was DCC (dicyclohexylcarbodiimide). The reaction was then carried out under a nitrogen atmosphere at room temperature for 48 hours to synthesize intermediate 1. Intermediate 1 was then reacted with... The reactants were mixed in a 1:1 molar ratio, with CuCl as the catalyst (1% of the total reactants) and butanone and isopropanol as the solvent (7:3 volume ratio). The reaction temperature was 90℃, and the reaction time was 24 h to synthesize intermediate 2. Intermediate 2 and... The mixture was prepared by mixing at a molar ratio of 1:1, using CuCl as the catalyst and isopropanol as the solvent, at a reaction temperature of 32°C for 48 hours. The product was obtained by precipitation with petroleum ether and filtration.

[0230] The structural formula of the anti-cracking agent is as follows:

[0231]

[0232] Examples and Comparative Examples

[0233] Preparation of the positive electrode sheet

[0234] A first binder, PVDF (weight average molecular weight of 1 million), an anti-cracking agent, and a solvent, NMP, are mixed to form a glue solution with a solid content of 4.3%. The positive electrode active material, LiFePO4, the second binder, PTFE (weight average molecular weight of 20 million), and the conductive agent, carbon black, are kneaded with the glue solution to form a clump material with a solid content of 75%. The obtained clump material is extruded through a twin-screw extruder to obtain a film of uniform thickness. The prepared film is then thinned by roller pressing to obtain a 1mm flexible film, which is then laminated with a positive electrode current collector aluminum foil. After drying in an oven, it undergoes further cold pressing and slitting to obtain the positive electrode sheet. The total weight of the positive electrode active material and the anti-cracking agent is 97.3% of the positive electrode active material layer, the weight of the conductive agent is 0.7% of the positive electrode active material layer, the weight of the first binder is 1.8% of the positive electrode active material layer, and the weight of the second binder is 0.2% of the positive electrode active material layer. The weight percentage of the anti-cracking agent in the positive electrode active material layer is shown in Table 1, and the remainder is positive electrode active material.

[0235] Preparation of the negative electrode sheet

[0236] The negative electrode active material graphite, the binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na), and the conductive agent carbon black (Super P) are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly coated onto the surface of the negative electrode current collector copper foil. After drying and cold pressing, the negative electrode sheet is obtained.

[0237] Preparation of Electrolyte

[0238] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried LiPF6 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0239]

Isolation Film

[0240] Porous polyethylene film is used as the separator.

[0241] [Preparation of battery cells]

[0242] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a battery cell is obtained.

[0243] The main parameter controls for each embodiment and comparative example are shown in Table 1 below:

[0244]

[0245]

[0246] In the table, " / " indicates that the substance does not exist or that the limitation does not exist.

[0247] In the table, "existing cracking agent" refers to Where x is 40.

[0248] The reaction time for preparing the anti-cracking agent in Example 13 was 60% of the reaction time for preparing the anti-cracking agent in Example 1.

[0249] The reaction time for preparing the anti-cracking agent in Example 14 was 80% of the reaction time for preparing the anti-cracking agent in Example 1.

[0250] The reaction time for preparing the anti-cracking agent in Example 15 was 200% of the reaction time for preparing the anti-cracking agent in Example 1, and the reaction temperature for preparing the anti-cracking agent in Example 15 was 80% of the reaction temperature for preparing the anti-cracking agent in Example 1.

[0251] The electrodes and battery cells provided in each embodiment and comparative example were tested, including:

[0252] Cracking was tested by scanning electron microscopy (SEM) of the prepared positive electrode sheet, and the cracking on the electrode surface was observed. The morphology of the cracks is as follows: Figure 9 As shown in the electron microscope scan, black cracks are visible, while the morphology of the uncracked area is as follows. Figure 10 As shown, no black cracks are visible in the electron microscope scan image.

[0253] Electrode adhesion test: Cut the electrode into strips 400mm long and 30mm wide using a custom die; then take a flat, thin steel plate, approximately 200-300mm long and 40-60mm wide, and apply a strip of double-sided tape (longer than the sample test length, 20mm wide) to the center of the steel plate, smoothing it firmly to ensure the tape adheres tightly to the center. Peel off the double-sided tape and attach the electrode to the tape strip; then insert the steel plate with the attached electrode into the lower clamp of the tensile testing machine and fix it vertically; insert the electrode without tape into the upper clamp and fix it, so that the electrode with tape adhered to it forms a 180° angle with the electrode fixed in the upper clamp. After fixing the test sample, calibrate and zero the sample, set the test width, electrode peeling length of 50mm, peeling speed of 100mm / min, and then start the test. After the test is completed, the load and fixture displacement data during the peeling process can be obtained. The adhesive force can be calculated as: adhesive force = load / double-sided tape width. Plotting the adhesive force against the displacement will give the peeling force curve. The adhesive force corresponding to the flat point of the curve is the adhesive force of the electrode.

[0254] DCR (DC internal resistance) performance test: At 25℃, the battery is charged at a constant current of 0.33C to 100% SOC (cutoff voltage 3.65V), and then discharged at a constant current of 0.33C to 0.5Cn (Cn represents the battery capacity) to adjust the battery to 50% SOC. The discharge cutoff voltage is 3.65V. The battery is left to stand for 30 minutes, and the voltage after the standing period is recorded as V1. Then the battery is discharged at a current of 3C (recorded as I) for 30 seconds, and the discharge cutoff voltage is recorded as V2.

[0255] The DC internal resistance of the battery is DCR = (V1-V2) / I, where V1 represents the resting end voltage, V2 represents the discharge cutoff voltage, and I represents the discharge current.

[0256] 3C capacity retention rate (rate performance) test: Charge at 0.33C to a constant voltage of 3.65V, charge to a current of 0.05C, let stand for 5 minutes, discharge at 0.33C to 2.5V and measure the discharge capacity during this period, let stand for 30 minutes; Charge at 0.33C to a constant voltage of 3.65V, charge to a current of 0.05C, let stand for 5 minutes, discharge at 3C to 2.5V and measure the discharge capacity during this period, let stand for 30 minutes. 3C capacity retention rate = 3C discharge capacity / 0.33C discharge capacity * 100%.

[0257] Cyclic performance test: At 25℃, the battery is charged at a constant current of 1C to 3.65V, then charged at a constant voltage to a current of 0.05C. After resting for 30 minutes, the battery is discharged at a constant current of 1C to 2.5V, and then rested for 30 minutes. The discharge capacity C0 of the battery is recorded. The battery is then cycled as follows: At 25℃, the battery is charged at a constant current of 1C0 to 3.65V, then charged at a constant voltage to a current of 0.05C. After resting for 30 minutes, the battery is discharged at a constant current of 1C0 to 2.5V, and then rested for 30 minutes. The discharge capacity of the battery in the first cycle is C1. The battery is cycled again using the above method. The discharge capacity of the second cycle is C2, ..., and the discharge capacity of the 1200th cycle is Cn. The cycle performance of the battery is represented by Cn / C1. The larger the Cn / C1, the better the cycle performance of the battery.

[0258] The test results are shown in the table below:

[0259]

[0260]

[0261] As can be seen from the table above, the electrode prepared by the method provided in the embodiments of this application can achieve a better anti-cracking effect on the electrode with a thicker active material layer by adding a specific anti-cracking agent to the active material layer, thereby enabling the assembled battery to have higher dynamic performance and cycle performance.

[0262] A comparison of the data from Examples 1 to 8 and Comparative Examples 1 to 2 shows that the use of a specific anti-cracking agent can achieve a high anti-cracking effect, thereby enabling the battery to maintain a 3C capacity retention rate of over 94.80% and a 1200-cycle capacity retention rate of over 83.00%.

[0263] A comparison of the data from Examples 1 and 9 to 12 shows that as the amount of anti-cracking agent gradually increases, the 3C capacity retention rate and the 1200-cycle capacity retention rate of the battery both show a trend of first improving and then deteriorating. By controlling the amount of anti-cracking agent at 0.10% to 0.50%, the 3C capacity retention rate of the battery is above 94.00%, and the 1200-cycle capacity retention rate is above 82.10%. In particular, controlling the amount of anti-cracking agent at 0.20% to 0.30% can make the 3C capacity retention rate above 95.30% and the 1200-cycle capacity retention rate above 82.90%.

[0264] A comparison of the data from Examples 1 and 13 to 15 shows that as the weight-average molecular weight of the anti-cracking agent gradually increases, the 3C capacity retention rate of the battery first improves and then deteriorates. The capacity retention rate after 1200 cycles shows a gradually improving trend. By controlling the weight-average molecular weight of the anti-cracking agent to be above 2000, the 3C capacity retention rate of the battery is above 94.00%, and the capacity retention rate after 1200 cycles is above 82.00%.

[0265] The above are merely specific embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A crack-resistant agent, characterized in that, The structural formula of the anti-cracking agent includes: Wherein, R1 is selected from at least one of H and C1-C6 alkyl groups; R2 and R3 are each independently selected from H, C1-C8 alkyl, C1-C8 oxaalkyl, C1-C8 thiaalkyl, C3-C8 alkenyl, C3-C8 ester, C3-C8 sulfonate, and -(CH2). n -OH, -(CH2) m At least one of -NH2, where n is a positive integer from 1 to 6, m is a positive integer from 1 to 6; and R2 and R3 are not both H; R4 is selected from H, Li, Na, K, C1-C8 alkyl, C1-C8 ester, C1-C8 sulfonic acid, C1-C8 sulfonic acid salt, C1-C8 amino, C1-C8 sulfonate, C1-C8 alkoxy, C1-C8 alkylthio, 3-6 membered N-containing heterocyclic group, 3-6 membered O-containing heterocyclic group, phenyl, and -(CH2). p At least one of N(CH3)2, wherein p is a positive integer from 2 to 5; R5 is selected from H, C1-C8 alkyl, C1-C8 ester, C1-C8 sulfonic acid, C1-C8 sulfonic acid salt, C1-C8 sulfonate, C1-C8 N-containing alkyl, C1-C8 alkoxy, C1-C8 alkylthio, 3-6 membered N-containing heterocyclic group, 3-6 membered O-containing heterocyclic group, -(CH2). q Si(OCH2CH3)3 and -(CH2) g -NH2 at least one, where q is a positive integer from 2 to 4 and g is a positive integer from 1 to 6; R6 is selected from at least one of the halogen elements; x, y, and z are all positive integers.

2. The anti-cracking agent according to claim 1, characterized in that, R2 and R3 are independently selected from -CH3, -CH2CH3, -(CH2)2CH3, -(CH2)3CH3, -(CH2)4CH3, -(CH2)5CH3, -CH2OCH3, -CH2OCH2CH3, -CH2O(CH2)2CH3, -CH2O(CH2)3CH3, -CH2O(CH2)4CH3, -CH2O(CH2)5CH3, -CH2O(CH2)6CH3, -(CH2)2O(CH2)5CH3, -(CH2)3O(CH2)4CH3, -CH2SCH3, -C H2SCH2CH3, -CH2S(CH2)2CH3, -CH2S(CH2)3CH3, -CH2S(CH2)4CH3, -CH2S(CH2)5CH3, -CH2S(CH2)6CH3, -(CH2)2S(CH2)5CH3, -(C H2)3S(CH2)4CH3, -CH2CH=CH2, -CH2CH=CHCH3, -CH2CH=CHCH2CH3, -CH2CH2CH=CHCH2CH3, -COOCH3, -COOCH2CH3, -COO(CH2)2CH3, -COO(CH2)3CH3, -COO(CH2)4CH3, -CH2COOCH2CH3, -CH2COO(CH2)2CH3, -CH2COO(CH2)3CH3, -(CH2)2COO(CH2)3CH3, -SO3CH3, -S O3CH2CH3, -SO3(CH2)2CH3, -SO3(CH2)3CH3, -SO3(CH2)4CH3, -CH2SO3CH2CH3, -CH2SO3(CH2)2CH3, -CH2SO3(CH2)3CH3, -(CH2)2 At least one of SO3CH3, -(CH2)2SO3CH2CH3, -(CH2)2SO3(CH2)2CH3, -SO2CH3, -SO2CH2CH3, -SO2(CH2)2CH3, -SO2(CH2)3CH3, -SO2(CH2)4CH3, -CH2SO2CH2CH3, -CH2SO2(CH2)2CH3, -CH2SO2(CH2)3CH3, -(CH2)2SO2CH3, -(CH2)2SO2CH2CH3 and -(CH2)2SO2(CH2)2CH3; and / or R6 is selected from at least one of F, Cl, or Br.

3. The anti-cracking agent according to any one of claims 1 to 2, characterized in that, The anti-cracking agent comprises at least one of Formula 1 to Formula 8: Formula 1: Where x, y, and z are independently selected from positive integers, Formula 2: Where x, y, and z are independently selected from positive integers, Formula 3: Where x, y, and z are independently selected from positive integers, Formula 4: Where x, y, and z are independently selected from positive integers, Formula 5: Where x, y, and z are independently selected from positive integers, Formula 6: Where x, y, and z are independently selected from positive integers, Formula 7: Where x, y, and z are independently selected from positive integers, Formula 8: In this context, x, y, and z are each independently selected from positive integers.

4. The anti-cracking agent according to any one of claims 1 to 3, characterized in that, The weight-average molecular weight of the anti-cracking agent is 3000-10000.

5. An electrode sheet, characterized in that, The electrode includes a current collector and an active material layer, the active material layer being attached to the current collector; the active material layer includes the anti-cracking agent as described in claims 1 to 4.

6. The electrode sheet according to claim 5, characterized in that, The anti-cracking agent accounts for 0.1% to 0.5% of the mass of the active material layer.

7. The electrode sheet according to any one of claims 5 to 6, characterized in that, The anti-cracking agent accounts for 0.2% to 0.3% of the mass of the active material layer.

8. The electrode sheet according to any one of claims 5 to 7, characterized in that, The active material layer further includes active materials, wherein the active materials constitute 89.5% to 99.5% of the active material layer by mass; and / or The active material layer further includes a conductive agent, wherein the conductive agent comprises 0.3% to 4% by mass in the active material layer; and / or The active material layer also includes an adhesive, wherein the adhesive accounts for 1% to 6% of the mass of the active material layer.

9. The electrode sheet according to any one of claims 5 to 8, characterized in that, The active material layer further includes an adhesive, which comprises a first adhesive and a second adhesive; and / or The first adhesive comprises at least one of polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and fluorinated acrylate resin; and / or The second adhesive comprises at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and ethylene-chlorotrifluoroethylene copolymer; and / or The weight-average molecular weight of the second adhesive is not less than ten million.

10. The electrode sheet according to claim 9, characterized in that, The first adhesive accounts for 0.5% to 4% of the active material layer by mass; and / or The second adhesive accounts for 0.5% to 2% of the mass of the active material layer.

11. A single battery cell, characterized in that, The battery cell includes the electrode sheet according to any one of claims 5 to 10.

12. A secondary battery, characterized in that, The secondary battery includes the battery cell described in claim 11.

13. An electrical appliance, characterized in that, The electrical equipment includes the battery cell of claim 11 or the secondary battery of claim 12.

Images