Positive pole piece and preparation method thereof, battery monomer, battery and electric device

Abstract

The embodiment of the invention provides a positive pole piece, a preparation method of the positive pole piece, a battery monomer, a battery and a power utilization device. The positive pole piece comprises: an active material layer, wherein the active material layer comprises a first active material, a conductive agent and a binder; wherein the first active material comprises a layered transition metal oxide, and the binder comprises a flexible binder used for bonding the first active material and the conductive agent. The performance of the battery containing the positive pole piece is improved.

Description

Positive electrode sheet and preparation method thereof, battery cell, battery and electrical device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a positive electrode plate and a preparation method thereof, a battery cell, a battery and an electrical device. Background Art

[0002] In recent years, the application scope of lithium-ion batteries has become increasingly wide. They are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0003] As a component of a battery, the performance of the positive electrode sheet is crucial to the performance of the battery. Therefore, how to provide a positive electrode sheet to improve battery performance is a technical problem that needs to be solved urgently.

[0004] Summary of the Invention

[0005] The embodiments of the present application provide a positive electrode plate and a preparation method thereof, a battery cell, a battery, and an electrical device to improve the performance of the battery.

[0006] In a first aspect, a positive electrode plate is provided, comprising: an active material layer, the active material layer comprising a first active material, a conductive agent and a binder; wherein the first active material comprises a layered transition metal oxide, and the binder comprises a flexible binder for bonding the first active material and the conductive agent.

[0007] The embodiment of the present application provides a positive electrode plate, which includes an active material layer, and the active material layer includes a first active material, a conductive agent and a binder. Specifically, the first active material includes a layered transition metal oxide, and the binder includes a flexible binder for bonding the first active material and the conductive agent. The layered transition metal oxide is used as the positive electrode active material. During the use of the battery, the volume of the layered transition metal oxide shrinks significantly, which increases the gap between the layered transition metal oxide and the binder. The layered transition metal oxide will tear the binder, causing the binder to separate from the first active material and / or the conductive agent, and the first active material and the conductive agent lose electrical connection due to the failure of the binder. In the technical solution of the embodiment of the present application, a flexible binder is provided for bonding the layered transition metal oxide and the conductive agent. The flexible binder has good stretchability. When the volume shrinkage of the layered transition metal oxide tears the binder, the flexible binder will deform to adapt to the volume shrinkage of the layered transition metal oxide and maintain the electrical connection between the layered transition metal oxide and the conductive agent, thereby reducing the impact of the failure of the electrical connection between the first active material and the conductive agent on the battery performance. Therefore, the technical solution of the embodiment of the present application can improve the performance of the battery.

[0008] In a possible implementation, the flexible adhesive includes at least one of a polyethylene-based adhesive, a polyisocyanate-based adhesive, and a polypropylene-based adhesive.

[0009] In a possible implementation, the flexible adhesive includes at least one of polyvinylpyrrolidone-polyethyleneimine (PVP-PEI) and poly (N-methylacrylate-3,4-hydroxy-L-phenylalanine) (PMDOPA).

[0010] The -NH2 groups in PVP-PEI form a dynamic hydrogen bond network with the C=O groups, giving PVP-PEI good self-healing properties and a certain degree of stretchability. PMDOPA is rich in o-diphenol functional groups, which gives PMDOPA good adhesion and improved flexibility. During the use of the battery, the layered transition metal oxide shrinks in volume and tears the binder. However, PVP-PEI, due to its good self-healing properties and a certain degree of stretchability, as well as PMDOPA's good adhesion and improved flexibility, can avoid the problem of poor electrical connection between the first active material and the conductive agent caused by the volume shrinkage of the layered transition metal oxide.

[0011] In a possible implementation, the first active material includes at least one of a ternary material and a quaternary material.

[0012] In a possible implementation, the first active material includes: Li 1+a Ni x Coy M 1-x-y O 2+b ; Wherein, M includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.5≤x<1.0, 0≤y<0.5, x+y<1, -0.5≤a≤0.5, and -0.02≤b<0.02.

[0013] In a possible implementation, the first active material includes lithium nickel cobalt manganese oxide.

[0014] Lithium nickel cobalt manganese oxide has the advantages of good cycle performance (excellent cycle stability at both room temperature and high temperature), high energy density, high voltage platform, good thermal stability, long cycle life, ideal crystal structure, low self-discharge, and no memory effect. Therefore, using lithium nickel cobalt manganese oxide as the positive electrode active material can improve the performance of the battery.

[0015] In a possible implementation, the conductive agent includes a linear conductive agent, and the linear conductive agent includes at least one of carbon nanotubes and graphene.

[0016] Linear conductive agents have good electrical conductivity, can reduce the contact resistance of the electrode, accelerate the movement of electrons, and can also effectively increase the migration rate of lithium ions in the electrode material, improve the electronic conductivity of the electrode, and thus improve the charge and discharge efficiency of the electrode. For example, carbon atoms in carbon nanotubes and graphene take SP 2 Hybridization results in high modulus and strength. Meanwhile, carbon nanotubes have good flexibility, stretchability, and electrical conductivity, while graphene has high tensile strength, good toughness, and electrical conductivity. Using carbon nanotubes and / or graphene as conductive agents can significantly enhance the conductivity of batteries.

[0017] In a possible implementation, the positive electrode material further includes a second active material, the second active material includes an olivine structure phosphate material, and optionally, the second active material includes: Li 1+c Fe d M' 1- d P 1-m O 4-n ; wherein, M' includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge, wherein, -0.2≤c≤0.2, 0.3≤d≤1, 0≤m≤0.1, 0≤n≤0.1.

[0018] In a possible implementation, the second active material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

[0019] Olivine structure is a crystal structure of a material. Materials with olivine structure have high stability. When applied to battery cells, they can reduce the risk of fire and explosion of battery cells under high temperature and other conditions, which is beneficial to improving the reliability of battery cells. The positive electrode material uses a composite active material, mixing layered transition metal oxides with phosphate materials. The battery combines the advantages of layered transition metal oxides and phosphate materials, further improving battery performance. For example, the second active material includes lithium iron phosphate, which has the advantages of high energy density, high safety, and long cycle life, which can improve the battery's cycle performance and energy density.

[0020] In a possible implementation, a mass ratio of the first active material to the second active material is 0.1:1 to 9:1.

[0021] The mass ratio of the first active material to the second active material is set within an appropriate range so that the battery can have the advantages of both layered transition metal oxides and phosphate materials, thereby improving the performance of the battery.

[0022] In a possible implementation, based on the total weight of the active material layer, the weight of the conductive agent in the active material layer accounts for 0.4% to 3%.

[0023] If the conductive agent content in the active material layer is too low, the electron conduction channels will be limited, making it ineffective for electrical conduction and unfavorable for high-current charge and discharge. If the conductive agent content in the active material layer is too high, the proportion of active material in the active material layer will be reduced, which will reduce the battery capacity. An appropriate content of the conductive agent in the active material layer will result in a higher discharge capacity and better cycle performance.

[0024] In a second aspect, a method for preparing a positive electrode plate is provided, comprising: providing an active material layer, the active material layer comprising a first active material, a conductive agent and a binder; wherein the first active material comprises a layered transition metal oxide, and the binder comprises a flexible binder for bonding the first active material and the conductive agent.

[0025] In a third aspect, a battery cell is provided, comprising the positive electrode sheet according to the first aspect and any possible implementation thereof.

[0026] In a fourth aspect, a battery is provided, comprising the battery cell described in the third aspect.

[0027] In a fifth aspect, an electrical device is provided, comprising the battery described in the fourth aspect.

[0028] In an embodiment of the present application, a positive electrode sheet is provided, which includes an active material layer, and the active material layer includes a first active material, a conductive agent, and a binder. Specifically, the first active material includes a layered transition metal oxide, and the binder includes a flexible binder for bonding the first active material and the conductive agent. The layered transition metal oxide is used as a positive electrode active material. During the use of the battery, the volume of the layered transition metal oxide shrinks significantly, which increases the gap between the layered transition metal oxide and the binder. The layered transition metal oxide will tear the binder, causing the binder to separate from the first active material and / or the conductive agent, and the first active material and the conductive agent lose electrical connection due to the failure of the binder. In the technical solution of the embodiment of the present application, a flexible binder is provided for bonding the layered transition metal oxide and the conductive agent. The flexible binder has good stretchability. When the volume shrinkage of the layered transition metal oxide tears the binder, the flexible binder will deform to adapt to the volume shrinkage of the layered transition metal oxide and maintain the electrical connection between the layered transition metal oxide and the conductive agent, thereby reducing the impact of the failure of the electrical connection between the first active material and the conductive agent on the battery performance. Therefore, the technical solution of the embodiment of the present application can improve the performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0030] FIG1-1 is a scanning electron microscope image of lithium nickel cobalt manganese oxide (NCM622) disclosed in one embodiment of the present application;

[0031] FIG1-2 is a scanning electron microscope image of lithium nickel cobalt manganese oxide (NCM622) disclosed in one embodiment of the present application;

[0032] FIG2-1 is a scanning electron microscope image of lithium iron phosphate (LFP) disclosed in one embodiment of the present application;

[0033] FIG2-2 is a scanning electron microscope image of lithium iron phosphate (LFP) disclosed in one embodiment of the present application;

[0034] FIG3-1 is a scanning electron microscope image of lithium iron manganese phosphate (LFMP) disclosed in one embodiment of the present application;

[0035] FIG3-2 is a scanning electron microscope image of lithium iron manganese phosphate (LFMP) disclosed in one embodiment of the present application;

[0036] FIG4 is a schematic diagram of a battery cell disclosed in an embodiment of the present application;

[0037] FIG5 is a schematic diagram of the exploded structure of a battery cell disclosed in one embodiment of the present application;

[0038] FIG6 is a schematic diagram of the exploded structure of a battery disclosed in one embodiment of the present application;

[0039] FIG7 is a schematic diagram of an electrical device disclosed in an embodiment of the present application.

[0040] In the drawings, the drawings are not drawn to scale.

[0041] The accompanying drawings in the specific implementation manner are as follows:

[0042] Battery 10 , box 11 , battery cell 20 , shell 21 , electrode assembly 22 , cover plate 23 . DETAILED DESCRIPTION

[0043] Below, the embodiments of the battery cells, batteries, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] In the description of this application, it should be noted that, unless otherwise specified, "plurality" means more than two; terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are merely for the purpose of facilitating the description of this application and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this application. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0047] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0048] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0050] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0051] Lithium-ion batteries are widely used in mobile phones, electric vehicles, power stations, and other fields due to their high energy density, high voltage, and long life. As a component of the battery, the performance of the positive electrode is crucial to its performance.

[0052] The positive electrode sheet includes a positive electrode current collector and a positive electrode material coated on the surface of the positive electrode current collector. The positive electrode material may include a positive electrode active material, a conductive agent, a binder, and a solvent for dissolving these materials. The positive electrode active material is electrically connected to the conductive agent through the binder, achieving electrical connection between the positive electrode active materials and between the positive electrode active materials and the positive electrode current collector.

[0053] However, some positive electrode active materials, such as layered transition metal oxides, will shrink in volume during the use of the battery due to the properties of the materials themselves, and tear the binder, causing the binder to separate from the positive electrode active material or the conductive agent, thereby causing the electrical connection between the positive electrode active material and the conductive agent to fail, resulting in the electrical connection between the positive electrode active materials and between the positive electrode active materials and the positive electrode current collector to fail, affecting the performance of the battery.

[0054] In view of this, an embodiment of the present application provides a positive electrode plate, including an active material layer, the active material layer including a first active material, a conductive agent and a binder. Specifically, the first active material includes a layered transition metal oxide, and the binder includes a flexible binder for bonding the first active material and the conductive agent. In the technical solution of the embodiment of the present application, a flexible binder is provided for bonding the layered transition metal oxide and the conductive agent. The flexible binder has good stretchability. When the volume shrinkage of the layered transition metal oxide tears the binder, the binder will deform to adapt to the volume shrinkage of the layered transition metal oxide and maintain the electrical connection of the layered transition metal oxide, thereby reducing the impact of the failure of the electrical connection between the positive electrode active material and the conductive agent on the battery performance. Therefore, the technical solution of the embodiment of the present application can improve the performance of the battery.

[0055] The following describes in detail several embodiments of the present application.

[0056] [Positive electrode]

[0057] The positive electrode sheet includes a positive electrode current collector and an active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode sheet provided in embodiments of the present application includes an active material layer comprising a first active material, a conductive agent, and a binder. Specifically, the first active material comprises a layered transition metal oxide, and the binder comprises a flexible binder for bonding the first active material and the conductive agent.

[0058] Layered transition metal oxides, which are active materials for battery positive electrodes, are a class of oxides with a multilayer (generally two-dimensional) structure. They are obtained based on the redox reaction of transition metal cations with lattice oxygen anions and have high energy and high power density.

[0059] Flexible binders bond the positive active material and conductive agent in the positive electrode sheet, thereby achieving electrical connection between the positive active materials and between the positive active materials and the positive current collector. Flexible binders have excellent stretchability and bond strength, and can adapt to external forces while maintaining bond strength.

[0060] The conductive agent has conductive properties and plays the role of collecting microcurrent between the positive electrode active materials in the positive electrode sheet to reduce the contact resistance of the electrode and accelerate the movement rate of electrons. It can also effectively increase the migration rate of lithium ions in the electrode material, thereby improving the charge and discharge efficiency of the electrode.

[0061] The positive electrode sheet provided in the embodiment of the present application includes an active material layer, and the active material layer includes a first active material, a conductive agent and a binder. Specifically, the first active material includes a layered transition metal oxide, and the binder includes a flexible binder for bonding the first active material and the conductive agent. The layered transition metal oxide is used as the positive electrode active material. During the use of the battery, the volume of the layered transition metal oxide shrinks significantly, which increases the gap between the layered transition metal oxide and the binder. The layered transition metal oxide will tear the binder, resulting in the binder being separated from the first active material and / or the conductive agent. The first active material and the conductive agent are not bonded by the binder and lose electrical connection. In the technical solution of the embodiment of the present application, a flexible binder is provided for bonding the layered transition metal oxide and the conductive agent. The flexible binder has good stretchability. When the volume shrinkage of the layered transition metal oxide tears the binder, the flexible binder will deform to adapt to the volume shrinkage of the layered transition metal oxide, maintain the electrical connection between the layered transition metal oxide and the conductive agent, and thus reduce the impact of the failure of the electrical connection between the first active material and the conductive agent on the battery performance. Therefore, the technical solution of the embodiment of the present application can improve the performance of the battery.

[0062] Optionally, in some embodiments, the flexible adhesive includes at least one of a polyethylene-based adhesive, a polyisocyanate-based adhesive, and a polypropylene-based adhesive.

[0063] Specifically, the flexible binder may include at least one of polyvinylpyrrolidone-polyethyleneimine (PVP-PEI) and poly (N-methylacrylate-3,4-hydroxy-L-phenylalanine) (PMDOPA).

[0064] The -NH2 groups in PVP-PEI form a dynamic hydrogen bond network with the C=O groups, giving PVP-PEI good self-healing properties and a certain degree of stretchability. PMDOPA is rich in o-diphenol functional groups, which gives PMDOPA good adhesion and improved flexibility. During the use of the battery, the layered transition metal oxide shrinks in volume and tears the binder. However, PVP-PEI, due to its good self-healing properties and a certain degree of stretchability, as well as PMDOPA's good adhesion and improved flexibility, can avoid the problem of poor electrical connection between the first active material and the conductive agent caused by the volume shrinkage of the layered transition metal oxide.

[0065] Optionally, in some embodiments, the first active material includes at least one of a ternary material and a quaternary material.

[0066] Optionally, the first active material includes: Li 1+a Ni x Co y M 1-x-y O 2+b ; Wherein, M includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.5≤x<1.0, 0≤y<0.5, x+y<1, -0.5≤a≤0.5, and -0.02≤b<0.02.

[0067] Optionally, in some embodiments, the first active material includes lithium nickel cobalt manganese oxide.

[0068] It should be understood that the aforementioned lithium nickel cobalt manganese oxide is merely an example of a substance used as the first active material in the embodiments of this application and does not constitute a limitation on the first active material of this application. For example, the first active material may also include lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, etc.

[0069] Lithium nickel cobalt manganese oxide has the advantages of good cycle performance (excellent cycle stability at both room temperature and high temperature), high energy density, high voltage platform, good thermal stability, long cycle life, ideal crystal structure, low self-discharge, and no memory effect. Therefore, using lithium nickel cobalt manganese oxide as the positive electrode active material can improve the performance of the battery.

[0070] Optionally, in some embodiments, the conductive agent includes a linear conductive agent, and the linear conductive agent includes at least one of carbon nanotubes and graphene.

[0071] Linear conductive agents have good electrical conductivity, can reduce the contact resistance of the electrode, accelerate the movement of electrons, and can also effectively increase the migration rate of lithium ions in the electrode material, improve the electronic conductivity of the electrode, and thus improve the charge and discharge efficiency of the electrode. For example, carbon atoms in carbon nanotubes and graphene take SP 2 Hybridization results in high modulus and strength. Meanwhile, carbon nanotubes have good flexibility, stretchability, and electrical conductivity, while graphene has high tensile strength, good toughness, and electrical conductivity. Using carbon nanotubes and / or graphene as conductive agents can significantly enhance the conductivity of batteries.

[0072] Optionally, in some embodiments, the positive electrode material further includes a second active material, the second active material includes an olivine structure phosphate material, and optionally, the second active material includes: Li 1+c Fe d M' 1-d P 1-m O 4-n ; wherein, M' includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge, wherein, -0.2≤c≤0.2, 0.3≤d≤1, 0≤m≤0.1, 0≤n≤0.1.

[0073] Optionally, in some embodiments, the second active material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

[0074] It should be understood that the aforementioned lithium iron phosphate and lithium manganese iron phosphate are merely illustrative examples of the second active material used in the embodiments of this application and do not constitute a limitation on the second active material of this application. For example, the second active material may also include lithium nickel phosphate, lithium cobalt phosphate, etc.

[0075] Olivine structure is a crystal structure of a material. Materials with olivine structure have high stability. When applied to battery cells, they can reduce the risk of fire and explosion of battery cells under high temperature and other conditions, which is beneficial to improving the reliability of battery cells. The positive electrode plate uses a composite active material, mixing layered transition metal oxides with olivine structure phosphate materials. The battery combines the advantages of layered transition metal oxides and olivine structure phosphate materials, further improving battery performance. For example, the second active material includes lithium iron phosphate, which has the advantages of high energy density, high safety, and long cycle life, which can improve the battery's cycle performance and energy density.

[0076] Optionally, in some embodiments, the mass ratio of the first active material to the second active material is 0.1:1 to 9:1.

[0077] Specifically, the mass ratio of the first active material to the second active material can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or the mass ratio value is within the range obtained by combining any two of the above mass ratio values.

[0078] The mass ratio of the first active material to the second active material is set within an appropriate range so that the battery can have the advantages of both layered transition metal oxides and phosphate materials, thereby improving the performance of the battery.

[0079] Optionally, in some embodiments, based on the total weight of the active material layer, the weight proportion of the conductive agent in the active material layer is 0.4% to 3%.

[0080] Specifically, the weight proportion of the conductive agent in the active material layer can be 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, or its value is within the range obtained by combining any two of the above values.

[0081] If the conductive agent content in the active material layer is too low, the electron conduction channels will be limited, making it ineffective for electrical conduction and unfavorable for high-current charge and discharge. If the conductive agent content in the active material layer is too high, the proportion of active material in the active material layer will be reduced, which will reduce the battery capacity. An appropriate content of the conductive agent in the active material layer will result in a higher discharge capacity and better cycle performance.

[0082] Optionally, the positive electrode sheet further includes a positive electrode current collector. Optionally, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the active material layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0083] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. 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.).

[0084] [Preparation method of positive electrode sheet]

[0085] The method for preparing a positive electrode plate includes: providing an active material layer.

[0086] The active material layer includes a first active material, a conductive agent and a binder; wherein the first active material includes a layered transition metal oxide, and the binder includes a flexible binder for bonding the first active material and the conductive agent.

[0087] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the first active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0088] [Negative electrode]

[0089] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0090] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0091] 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0092] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. 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, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0093] In some embodiments, the negative electrode film layer may further 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).

[0094] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0095] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0096] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0097] [Electrolytes]

[0098] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0099] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0100] 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0101] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0102] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0103] [Isolation film]

[0104] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0105] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven 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.

[0106] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0107] The battery cell, battery and electrical device of the present application are described below with reference to the accompanying drawings.

[0108] The present application also provides a battery cell. Typically, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery's charge and discharge process, active ions are embedded and released back and forth between the positive and negative electrode sheets. The electrolyte conducts ions between the positive and negative electrode sheets. The separator is positioned between the positive and negative electrode sheets, primarily preventing a short circuit between the positive and negative electrodes while allowing ions to pass through.

[0109] It should be understood that the "embedding" process described in this application refers to the process in which active ions are embedded in the positive electrode active material or the negative electrode active material due to an electrochemical reaction, and the "extraction" and "de-intercalation" processes described in this application refer to the process in which active ions are removed from the positive electrode active material or the negative electrode active material due to an electrochemical reaction.

[0110] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0111] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0112] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG4 shows a battery cell 20 having a square structure as an example.

[0113] In some embodiments, referring to Figure 5, the outer packaging may include a shell 21 and a cover plate 23. The shell 21 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 21 has an opening connected to the receiving cavity, and the cover plate 23 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 22 through a winding process or a lamination process. The electrode assembly 22 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 22. The number of electrode assemblies 22 contained in the battery cell 20 can be one or more, and those skilled in the art can select according to specific actual needs.

[0114] In some embodiments, the battery 10 may include multiple battery cells 20. For example, FIG6 is a schematic structural diagram of a battery 10 according to one embodiment of the present application. The battery 10 may include multiple battery cells 20. The battery 10 may also include a housing 11 having a hollow interior and housing the multiple battery cells 20. For example, the multiple battery cells 20 may be connected in parallel, in series, or in a mixed combination and then placed in the housing 11.

[0115] Optionally, the battery 10 may also include other structures, which will not be described in detail here. For example, the battery 10 may also include a busbar component, which is used to achieve electrical connection between multiple battery cells 20, such as parallel connection, series connection, or mixed connection. Specifically, the busbar component can achieve electrical connection between the battery cells 20 by connecting the electrode terminals of the battery cells 20. Furthermore, the busbar component can be fixed to the electrode terminals of the battery cells 20 by welding. The electrical energy of the multiple battery cells 20 can be further led out through the box 11 through a conductive mechanism. Optionally, the conductive mechanism may also belong to the busbar component.

[0116] The number of battery cells 20 can be set to any value based on different power requirements. Multiple battery cells 20 can be connected in series, parallel, or in a hybrid manner to achieve higher capacity or power. Since each battery 10 may include a large number of battery cells 20, for ease of installation, the battery cells 20 can be grouped, with each group of battery cells 20 forming a battery module. The number of battery cells 20 included in a battery module is not limited and can be set according to requirements. A battery can include multiple battery modules, which can be connected in series, parallel, or in a hybrid manner.

[0117] In addition, the present application also provides an electric device, which includes at least one of the battery cells, battery modules or batteries provided in the present application. The battery cells, battery modules or batteries can be used as the power source of the electric device, and can also be used as the energy storage unit of the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0118] As the electrical device, a battery cell, a battery module or a battery can be selected according to its usage requirements.

[0119] Figure 7 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cell, a battery or battery module can be used.

[0120] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0121] [Example]

[0122] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0123] (1) Preparation of positive electrode sheet

[0124] Positive Electrode Sheet 1: Lithium nickel cobalt manganese oxide (NCM622), conductive carbon nanotubes (CNTs), and flexible chain binder polyvinyl pyrrolidone-polyethyleneimine (PVP-PEI) were dissolved in N-methyl pyrrolidone (NMP) at a weight ratio of 96:2:2 and mixed evenly to prepare positive electrode material 1. The mass ratio of the positive electrode active material (first active material NCM622) to the solvent was 1:2. The average volume particle size D50 of the first active material NCM622 was 3.5 μm.

[0125] The positive electrode material 1 was coated on an aluminum foil and dried at 100° C. to form an NCM coating on the aluminum foil. The thickness of the coating was 240 μm.

[0126] The coated electrode is cold pressed at 40T pressure, and the compaction density of the electrode is 2.8g / cm3 , and cut into strips to obtain the positive electrode sheet 1.

[0127] Positive electrode sheet 2: Positive electrode sheet 2 differs from positive electrode sheet 1 in that the positive electrode active material in positive electrode material 2 includes a first active material and a second active material, namely NCM622 and lithium iron phosphate (LFP), wherein the weight ratio of NCM622, LFP, CNT, and PVP-PEI is 48:48:2:2, to obtain positive electrode sheet 2. The average volume particle size D50 of the second active material LFP is 9.5 μm.

[0128] Positive electrode sheet 3: Positive electrode sheet 3 is different from positive electrode sheet 2 in that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in positive electrode material 3 is 19.2:76.8:2:2, thereby obtaining positive electrode sheet 3.

[0129] Positive electrode sheet 4: Positive electrode sheet 4 is different from positive electrode sheet 2 in that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in positive electrode material 4 is 76.8:19.2:2:2, thereby obtaining positive electrode sheet 4.

[0130] Positive electrode sheet 5: Positive electrode sheet 5 is different from positive electrode sheet 2 in that the conductive agent in positive electrode material 5 is CNT and conductive carbon black (Super-P), and the weight ratio of CNT to Super-P is 1:1, thereby obtaining positive electrode sheet 5.

[0131] Positive electrode sheet 6: Positive electrode sheet 6 is different from positive electrode sheet 2 in that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in positive electrode material 6 is 47.5:47.5:3:2, thereby obtaining positive electrode sheet 6.

[0132] Positive electrode sheet 7: Positive electrode sheet 7 is different from positive electrode sheet 2 in that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in positive electrode material 7 is 48.5:48.5:1:2, thereby obtaining positive electrode sheet 7.

[0133] Positive electrode sheet 8: The positive electrode sheet 8 is different from the positive electrode sheet 2 in that the binder in the positive electrode material 8 is PVP-PEI and PVDF, and the weight ratio of PVP-PEI and PVDF is 1:1, thereby producing the positive electrode sheet 8.

[0134] Positive electrode sheet 9: Positive electrode sheet 9 is different from positive electrode sheet 2 in that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in positive electrode material 9 is 48.95:48.95:2:2, thereby obtaining positive electrode sheet 9.

[0135] Positive electrode sheet 10 : The positive electrode sheet 10 is different from the positive electrode sheet 2 , except that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in the positive electrode material 10 is 9:87:2:2, thereby obtaining the positive electrode sheet 10 .

[0136] Positive electrode sheet 11: The positive electrode sheet 11 is different from the positive electrode sheet 2 in that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in the positive electrode material 11 is 86.4:9.6:2:2, thereby obtaining the positive electrode sheet 11.

[0137] Positive electrode sheet 12: The positive electrode sheet 12 is different from the positive electrode sheet 2 in that the second active material in the positive electrode material 12 is lithium manganese iron phosphate (LMFP), and the average volume particle size D50 of the second active material LMFP is 10 μm.

[0138] Positive electrode sheet 13: The positive electrode sheet 13 is different from the positive electrode sheet 2, except that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in the positive electrode material 13 is 47:47:4:2, thereby obtaining the positive electrode sheet 13.

[0139] Positive electrode sheet 14 : The positive electrode sheet 14 is different from the positive electrode sheet 2 in that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in the positive electrode material 14 is 90:6:2:2, thereby obtaining the positive electrode sheet 14 .

[0140] Positive electrode sheet 15 : The positive electrode sheet 15 is different from the positive electrode sheet 2 in that the weight ratio of NCM622, LFP, CNT, and PVP-PEI in the positive electrode material 15 is 6:90:2:2, thereby obtaining the positive electrode sheet 15 .

[0141] Positive electrode sheet 16 : The positive electrode sheet 16 is different from the positive electrode sheet 2 in that the conductive agent in the positive electrode material 16 is conductive carbon black (Super-P), so as to obtain the positive electrode sheet 16 .

[0142] Positive electrode sheet 17 : The positive electrode sheet 17 is different from the positive electrode sheet 1 in that the binder in the positive electrode material 17 is polyvinylidene fluoride (PVDF).

[0143] Positive electrode sheet 18 : The positive electrode sheet 18 is different from the positive electrode sheet 2 in that the binder in the positive electrode material 18 is PVDF, so as to manufacture the positive electrode sheet 18 .

[0144] Positive electrode sheet 19: The difference between positive electrode sheet 19 and positive electrode sheet 2 is that the positive electrode active material in positive electrode material 19 only contains the second active material LFP, and the weight ratio of LFP, CNT, and PVP-PEI is 96:2:2, so as to obtain positive electrode sheet 19.

[0145] Positive electrode sheet 20 : The positive electrode sheet 20 is different from the positive electrode sheet 2 , except that the positive electrode active material in the positive electrode material 20 only contains the second active material LMFP, and the weight ratio of LMFP, CNT, and PVP-PEI is 96:2:2, thereby producing the positive electrode sheet 20 .

[0146] Positive electrode sheet 21: The positive electrode sheet 21 is different from the positive electrode sheet 2 in that no conductive agent is added to the positive electrode material 21. The weight ratio of NCM622, LFP, and PVP-PEI is 49:49:2 to obtain the positive electrode sheet 21.

[0147] (2) Preparation of negative electrode sheet

[0148] The active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water in a weight ratio of 96:1.5:1.5:1 and evenly mixed with the solvent deionized water to prepare a negative electrode slurry; the negative electrode slurry is then evenly coated on the negative electrode current collector copper foil, and after drying, a negative electrode film is obtained, which is then cold pressed and cut into pieces to obtain a negative electrode sheet.

[0149] (3) Preparation of electrolyte: In an argon atmosphere glove box with a water content of <10 ppm, fully dried lithium salt (LiPF6) was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:20:60. Then, vinylene carbonate (VC) was added as an additive and mixed thoroughly to obtain an electrolyte. The concentration of the lithium salt was 1 mol / L.

[0150] (4) Preparation of isolation film: Conventional polypropylene film was used as the isolation film.

[0151] (5) Assembly of lithium-ion batteries: stack the positive electrode sheet, separator, and negative electrode sheet in order, with the separator placed between the positive and negative electrode sheets to act as an isolation layer, and then wind them to obtain an electrode assembly; place the electrode assembly in a battery case, dry it, and inject the electrolyte, and then undergo formation, standing, and other processes to produce a lithium-ion battery.

[0152] Example 1: A lithium-ion battery obtained by assembling the positive electrode sheet 1, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 1.

[0153] Example 2: The lithium-ion battery obtained by assembling the positive electrode sheet 2, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 2.

[0154] Example 3: The lithium-ion battery obtained by assembling the positive electrode sheet 3, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 3.

[0155] Example 4: The lithium-ion battery obtained by assembling the positive electrode sheet 4, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 4.

[0156] Example 5: The lithium-ion battery obtained by assembling the positive electrode sheet 5, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 5.

[0157] Example 6: The lithium-ion battery obtained by assembling the positive electrode sheet 6, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 6.

[0158] Example 7: The lithium-ion battery obtained by assembling the positive electrode sheet 7, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 7.

[0159] Example 8: The lithium-ion battery obtained by assembling the positive electrode sheet 8, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 8.

[0160] Example 9: The lithium-ion battery obtained by assembling the positive electrode sheet 9, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 9.

[0161] Example 10: The lithium-ion battery obtained by assembling the positive electrode sheet 10, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 10.

[0162] Example 11: The lithium-ion battery obtained by assembling the positive electrode sheet 11, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 11.

[0163] Example 12: The lithium-ion battery obtained by assembling the positive electrode sheet 12, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 12.

[0164] Example 13: The lithium-ion battery obtained by assembling the positive electrode sheet 13, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 13.

[0165] Example 14: The lithium-ion battery obtained by assembling the positive electrode sheet 14, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 14.

[0166] Example 15: The lithium-ion battery obtained by assembling the positive electrode sheet 15, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 15.

[0167] Example 16: The lithium-ion battery obtained by assembling the positive electrode sheet 16, the separator, the negative electrode sheet, and the electrolyte according to the above method is Example 16.

[0168] Comparative Example 1: A lithium-ion battery obtained by assembling the positive electrode sheet 17, the separator, the negative electrode sheet, and the electrolyte according to the above method is Comparative Example 1.

[0169] Comparative Example 2: A lithium-ion battery obtained by assembling the positive electrode sheet 18, the separator, the negative electrode sheet, and the electrolyte according to the above method is Comparative Example 2.

[0170] Comparative Example 3: A lithium-ion battery obtained by assembling the positive electrode sheet 19, the separator, the negative electrode sheet, and the electrolyte according to the above method is Comparative Example 3.

[0171] Comparative Example 4: A lithium-ion battery obtained by assembling the positive electrode sheet 20, the separator, the negative electrode sheet, and the electrolyte according to the above method is Comparative Example 4.

[0172] Comparative Example 5: A lithium-ion battery obtained by assembling the positive electrode sheet 21, the separator, the negative electrode sheet, and the electrolyte according to the above method is Comparative Example 5.

[0173] The product parameters of different embodiments are detailed in Table 1.

[0174] Table 1: Product parameters of comparative examples and different embodiments

[0175] Next, the testing process of relevant parameters is explained.

[0176] 1. Test of parameters related to positive electrode active materials

[0177] (1) Volume average particle size D50 test

[0178] Equipment model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard process: GB / T19077-2016 / ISO 13320:2009.

[0179] Specific test process: Take an appropriate amount of the sample to be tested (the sample concentration is sufficient to ensure 8-12% shading), add 20ml of deionized water, and simultaneously operate under an external ultraviolet light source for 5 minutes (53KHz / 120W) to ensure that the sample is completely dispersed. Then, measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0180] (2) Morphology test of positive electrode active materials

[0181] The positive electrode active materials of all examples and comparative examples were tested using a ZEISS Sigma 300 scanning electron microscope and then tested according to the standard JY / T010-1996 to observe the sample morphology. The test results are shown in Figures 1-1 to 3-2.

[0182] Specifically, Figures 1-1 and 1-2 are both scanning electron microscope images of NCM622 in the examples of the present application. The difference is that the observation magnifications of Figures 1-1 and 1-2 are different.

[0183] Figures 2-1 and 2-2 are both scanning electron microscope images of LFP in the examples of the present application. The difference is that the observation magnifications of Figures 2-1 and 2-2 are different.

[0184] Figures 3-1 and 3-2 are both scanning electron microscope images of the LFMP in the examples of the present application. The difference is that the observation magnifications of Figures 3-1 and 3-2 are different.

[0185] It should be pointed out here that the shape of the positive electrode material used in this application is not necessarily spherical, but may also be irregular, and may be primary particles or secondary particles.

[0186] 2. Battery performance test

[0187] (1) Battery capacity retention test

[0188] At 45°C, charge the lithium-ion battery at a constant current of 1 / 3C to 4.35V, then charge it at a constant voltage of 4.35V to a current of 0.05C, let it sit for 5 minutes, and then discharge it at 1 / 3C to 2.8V. The resulting capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity C of the battery after the nth cycle. n , then the battery capacity retention rate P after each cycle n =C n / C0×100%.

[0189] During the test, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ..., the 200th cycle corresponds to n=200. The battery capacity retention rate data corresponding to the embodiment and the comparative example in Table 1 are the data measured after 200 cycles under the above test conditions, i.e., P 200 value.

[0190] (2) Specific capacitance test

[0191] At 25°C, the lithium-ion battery was charged at a constant current of 1 / 3C to 4.35V, then charged at a constant voltage of 4.35V to a current of 0.05C, left for 5 minutes, and then discharged at 1 / 3C to 2.8V. The resulting capacity was recorded as the initial capacity C0, specific capacity = C0 / (m×97%), where m is the coating weight of the positive electrode active material of the lithium-ion battery.

[0192] (3) Rate performance test

[0193] At 25°C, the battery was charged at a constant current of 1 / 3C to 4.35V, then charged at a constant voltage of 4.35V to a current of 0.05C, left for 5 minutes, and then discharged at 0.1C to 2.8V. The average capacity obtained after 5 cycles was recorded as the initial capacity D0. Then, the battery was charged under the same conditions as above, and discharged at 1C and 2C respectively. The average capacity obtained after 5 cycles was recorded as the initial capacity D 1-2 The capacity retention rate Q of each battery discharge rate n Calculated according to the following formula: n =(D n / D0)×100%.

[0194] The battery performance tests were performed on the prepared comparative examples 1-5 and examples 1-16 according to the above method. The results are shown in Table 2.

[0195] Table 2: Performance test results of comparative examples and different embodiments

[0196] From the comparison of the results of Comparative Example 1-2 and Example 1-2, it can be seen that by adding the flexible binder PVP-PEI to the positive electrode material, the volume of the ternary material lithium nickel cobalt manganese oxide shrinks during the use of the battery, and the flexible binder adaptively deforms with the volume shrinkage of the lithium nickel cobalt manganese oxide, so that the electrical connection between the lithium nickel cobalt manganese oxide and the conductive agent will not fail due to the volume shrinkage of the lithium nickel cobalt manganese oxide, thereby ensuring the electrical connection between the positive electrode active materials, and thus improving the performance of the battery.

[0197] From the comparison of the results of Comparative Examples 3-4 and Example 1 with Examples 2-4 and 10-12, it can be seen that the positive electrode active material adopts a composite active material of lithium nickel cobalt manganese oxide and lithium iron phosphate / lithium manganese iron phosphate, which takes into account the advantages of high energy density of lithium nickel cobalt manganese oxide and long cycle life of lithium iron phosphate / lithium manganese iron phosphate, so the overall performance of the battery is improved.

[0198] By comparing the results of Examples 14-15 with those of Examples 2-4 and 10-11, it can be seen that by setting the mass ratio of the first active material lithium nickel cobalt manganese oxide to the second active material lithium iron phosphate within an appropriate range, the battery can have the advantages of both lithium nickel cobalt manganese oxide and lithium iron phosphate, which can improve the battery's cycle performance, increase the battery's capacity, and thus improve the battery's overall performance.

[0199] From the comparison of the results of Example 16 and Example 2, it can be seen that adding linear conductive agent carbon nanotubes to the positive electrode material can reduce the contact resistance of the electrode and accelerate the movement rate of electrons. At the same time, it can also effectively increase the migration rate of lithium ions in the electrode material and increase the electronic conductivity of the electrode, thereby improving the cycle performance and capacity of the battery.

[0200] From the comparison of the results of Comparative Example 5 and Example 13 with Examples 2, 6, 7, and 9, it can be seen that the weight proportion of the linear conductive agent in the positive electrode material should not be too high or too low. By controlling the weight proportion of the linear conductive agent in the positive electrode material within an appropriate range, the cycle performance of the battery can be improved, and the discharge capacity of the battery can be improved, thereby improving the overall performance of the battery.

[0201] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A positive electrode sheet, comprising: an active material layer, the active material layer comprising a first active material, a conductive agent and a binder; The first active material comprises a layered transition metal oxide, and the binder comprises a flexible binder for bonding the first active material and the conductive agent.

2. The positive electrode sheet according to claim 1, wherein: The flexible adhesive includes at least one of a polyethylene-based adhesive, a polyisocyanate-based adhesive, and a polypropylene-based adhesive.

3. The positive electrode sheet according to claim 2, wherein: The flexible adhesive includes at least one of polyvinyl pyrrolidone-polyethylene imine and poly-N-methylacrylate-3,4-hydroxy-L-phenylalanine.

4. The positive electrode sheet according to any one of claims 1 to 3, wherein: The first active material includes at least one of a ternary material and a quaternary material.

5. The positive electrode sheet according to claim 4, wherein: The first active material includes: Li 1+a Ni x Co y M 1-x-y O 2+b ; Among them, M includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.5≤x<1.0, 0≤y<0.5, x+y<1, -0.5≤a≤0.5, and -0.02≤b<0.

02.

6. The positive electrode sheet according to claim 5, wherein: The first active material includes lithium nickel cobalt manganese oxide.

7. The positive electrode sheet according to any one of claims 1 to 6, wherein: The conductive agent includes a linear conductive agent, and the linear conductive agent includes at least one of carbon nanotubes and graphene.

8. The positive electrode sheet according to any one of claims 1 to 7, wherein: The active material layer further includes a second active material, the second active material includes an olivine structure phosphate material, and optionally, the second active material includes: Li 1+c Fe d M' 1-d P 1-m O 4-n ; Wherein, M' includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge, wherein -0.2≤c≤0.2, 0.3≤d≤1, 0≤m≤0.1, and 0≤n≤0.

1.

9. The positive electrode sheet according to claim 8, wherein: The second active material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

10. The positive electrode sheet according to claim 8 or 9, wherein: The mass ratio of the first active material to the second active material is 0.1:1 to 9:

1.

11. The positive electrode sheet according to any one of claims 1 to 10, wherein: Based on the total weight of the active material layer, the weight proportion of the conductive agent in the active material layer is 0.4% to 3%.

12. A method for preparing a positive electrode sheet, comprising: providing an active material layer, the active material layer comprising a first active material, a conductive agent, and a binder; The first active material comprises a layered transition metal oxide, and the binder comprises a flexible binder for bonding the first active material and the conductive agent. 13 . A battery cell comprising the positive electrode sheet according to claim 1 .

14. A battery comprising the battery cell according to claim 13.

15. An electrical device comprising the battery according to claim 14.

Images