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 a positive current collector; the first coating is arranged on the surface of at least one side of the positive electrode current collector, and the first coating comprises a first active material; a second coating including a second active material, the second active material being different from the first active material; and the conductive layer is arranged between the first coating and the second coating and is used for isolating the first coating from the second coating. The performance of the battery comprising 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: a positive electrode current collector; a first coating layer, the first coating layer being arranged on the surface of at least one side of the positive electrode current collector, the first coating layer comprising a first active material; a second coating layer, the second coating layer comprising a second active material, the second active material being different from the first active material; and a conductive layer, the conductive layer being arranged between the first coating layer and the second coating layer, for isolating the first coating layer and the second coating layer.

[0007] The present invention provides a positive electrode sheet comprising a positive electrode current collector, a first coating layer, a second coating layer, and a conductive layer. Specifically, the first coating layer is disposed on at least one surface of the positive electrode current collector, and the conductive layer is disposed between the first coating layer and the second coating layer. The first active material included in the first coating layer and the second active material included in the second coating layer are different. In other words, the positive electrode active material comprises two different materials, the first active material and the second active material. This allows the positive electrode sheet to combine the advantages of both the first and second active materials, thereby improving the overall performance of the battery. On the other hand, due to differences in material properties between the first and second active materials, such as different electronic conductivities, direct contact between the first and second active materials can affect each other, reducing the performance of both active materials and thus affecting battery performance. Therefore, the conductive layer is used to separate the first and second coating layers, preventing direct contact between the first and second active materials while also electrically connecting the first and second active materials. In other words, the conductive layer prevents direct contact between the first and second active materials while ensuring electrical connection between them, allowing the first and second active materials to leverage their respective advantages and improving the overall performance of the battery.

[0008] In a possible implementation, the first active material includes at least one of an olivine-structured phosphate material and a spinel material.

[0009] 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. Olivine structure phosphates have the advantages of high theoretical specific capacity, good cycle stability, low cost and environmental friendliness. Spinel is a mineral composed of magnesium aluminum oxide, with tetrahedral and octahedral crystal forms. For example, spinel-type lithium manganese oxide materials have outstanding characteristics such as high specific capacity, low cost and low environmental pollution. Olivine structure phosphate materials and spinel materials are used as the first active material, which is beneficial to improving the performance of the battery.

[0010] In a possible implementation, the olivine structure phosphate material includes Li a Fe b M 1-b P 1- m O 4-n, wherein M includes at least one of the other metal elements except Fe, wherein 0≤a≤1.1, 0.3≤b≤1, 0≤m≤0.1, 0≤n≤0.1, optionally, M includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge, optionally, the olivine structure phosphate material includes at least one of lithium iron phosphate (LiFePO4) and lithium manganese iron phosphate (LiMnFePO4).

[0011] Lithium iron phosphate (LIFP) boasts long cycle life, excellent thermal stability, and high energy density; lithium iron manganese phosphate (LIMnP) also offers these advantages. Using LFP and LMPP as the first active material can improve battery cycle performance, energy density, and safety.

[0012] In one possible implementation, the spinel material includes LiNi c Mn 2-c O4, wherein 0≤c<2, optionally, the spinel material includes lithium manganate (LiMn2O4).

[0013] Lithium manganate as a positive electrode active material has the advantages of low price, high potential, environmental friendliness, high safety performance, and good rate performance.

[0014] In one possible implementation, the second active material includes a layered transition metal oxide.

[0015] Layered transition metal oxides, a class of oxides with multilayered (generally two-dimensional) structures, are used as positive electrode active materials in batteries. These oxides are derived from the redox reaction of transition metal cations with lattice oxygen anions and exhibit high energy and power density. Using layered transition metal oxides as a secondary active material can improve the energy density of batteries.

[0016] Optionally, the layered transition metal oxide includes LiCoO2, LiMnO2, LiNiO2, Li a’ Ni x Co y M 1 1-x-y O 2+d 、zLi2MnO3·(1-z)LiM 2 At least one of O2, wherein M 1 Including at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, La, M 2Including at least one of Co, Ni, and Mn, 0.5≤x≤1.0, 0≤y<0.5, x+y<1, 0.2≤a'<1.2, -0.02≤d<0.02, 0<z<1, optionally, the layered transition metal oxide includes Li(Ni 0.6 Co 0.2 Mn 0.2 ) 1.15 O2、Li(Ni 0.5 Co 0.2 Mn 0.3 ) 1.07 At least one of O2.

[0017] Lithium nickel cobalt manganese oxide (NCM) used as positive electrode active material has the advantages of high energy density, high voltage platform, good thermal stability and good cycle performance.

[0018] In a possible implementation, the conductive layer includes a conductive agent and a binder.

[0019] Conductive agents collect microcurrents between active materials, reducing electrode contact resistance and accelerating electron mobility. They also effectively increase the migration rate of metal ions within the electrode material, thereby improving the electrode's charge and discharge efficiency. Binders bond the active material to the conductive agent, enhancing electrical contact between them and stabilizing the structure of the positive electrode.

[0020] In a possible implementation, the conductive agent includes at least one of conductive carbon black, superconducting carbon, carbon dots, Ketjen black, and carbon nanotubes.

[0021] Due to the unique composition of carbon structure, carbon material conductive agents have good conductive properties. For example, conductive carbon black has low resistance and high conductivity, small particle size, large and rough specific surface area, high structure, clean surface (few compounds), etc. Ketjen black has a unique branched chain morphology, which makes it highly conductive. The carbon atoms in carbon nanotubes adopt SP 2 Hybridization gives it high modulus and high strength. Carbon nanotubes also have good flexibility, stretchability and electrical conductivity. Conductive carbon black, superconducting carbon, carbon dots, Ketjen black and carbon nanotubes as conductive agents can improve the conductivity of batteries.

[0022] In one possible implementation, the binder includes at least one of polyvinylidene fluoride, styrene butadiene rubber, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trichloroethylene copolymer and fluorine-containing acrylic resin, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, and polyarylate.

[0023] In one possible implementation, the thickness of the conductive layer is 1 μm to 15 μm, and optionally, the thickness of the conductive layer is 5 μm to 10 μm. On the one hand, the thickness of the conductive layer should not be too small, so that the conductive layer can effectively isolate the first active material from the second active material. On the other hand, the thickness of the conductive layer should not be too large, so as to ensure that the active material content in the positive electrode sheet is not too low, thereby ensuring the energy density of the battery.

[0024] In one possible implementation, the thickness of the first coating layer is 40 μm to 160 μm, and optionally, the thickness of the first coating layer is 70 μm to 140 μm. The thickness of the first coating layer should not be too large to reduce waste of the first active material and reduce the total volume of the battery, thereby lowering production costs. The thickness of the first coating layer should not be too small to ensure that the content of the first active material in the positive electrode sheet is not too low, which is conducive to improving battery performance.

[0025] In one possible implementation, the second coating layer has a thickness of 40 μm to 80 μm, and optionally, a thickness of 40 μm to 60 μm. The thickness of the second coating layer should not be too large to reduce waste of the second active material, reduce the total volume of the battery, and lower production costs. The thickness of the second coating layer should not be too small to ensure that the content of the second active material in the positive electrode sheet is not too low, which is beneficial to improving battery performance.

[0026] In a possible implementation, based on the total weight of the conductive layer, the weight percentage of the binder in the conductive layer is 1 wt% to 10 wt%, optionally 3 wt% to 7 wt%.

[0027] In a possible implementation, based on the total weight of the conductive layer, the weight percentage of the conductive agent in the conductive layer is 90 wt% to 99 wt%, optionally 93 wt% to 97 wt%.

[0028] The conductive agent in the conductive layer collects microcurrents between the active materials, reducing the contact resistance of the electrodes and accelerating the movement of electrons. It also effectively increases the migration rate of metal ions in the electrode material, thereby improving the charge and discharge efficiency of the electrodes. Too little conductive agent reduces the electron conduction channels in the positive electrode sheet, resulting in low utilization of the positive active material, which in turn reduces the battery's cycle performance and energy density.

[0029] In the above technical solution, by setting the weight contents of the conductive agent and the binder in the conductive layer within an appropriate range, the conductive layer can effectively play its role of isolating and electrically connecting the first active material and the second active material, thereby improving the overall performance of the battery.

[0030] In a possible implementation, based on the total weight of the first coating layer, the weight percentage of the first active material is 90 wt% to 98 wt%, optionally 96 wt% to 97 wt%.

[0031] In a possible implementation, based on the total weight of the first coating layer, the weight percentage of the conductive agent in the first coating layer is 0.1 wt% to 1 wt%, optionally 0.4 wt% to 0.6 wt%.

[0032] In a possible implementation, based on the total weight of the first coating layer, the weight percentage of the binder in the first coating layer is 1 wt% to 2 wt%, optionally, 1.2 wt% to 1.4 wt%.

[0033] In the above technical solution, the weight contents of the first active material, the conductive agent and the binder in the first coating layer are set within an appropriate range, so that the first active material can effectively function.

[0034] In a possible implementation, based on the total weight of the second coating layer, the weight percentage of the second active material is 90 wt% to 98 wt%, optionally 96 wt% to 97 wt%.

[0035] In a possible implementation, based on the total weight of the second coating layer, the weight percentage of the conductive agent in the second coating layer is 0.1 wt% to 1 wt%, optionally 0.4 wt% to 0.6 wt%.

[0036] In a possible implementation, based on the total weight of the second coating layer, the weight percentage of the binder in the second coating layer is 1 wt% to 2 wt%, optionally, 1.2 wt% to 1.4 wt%.

[0037] In the above technical solution, the weight contents of the second active material, the conductive agent and the binder in the second coating layer are set within an appropriate range, so that the second active material can effectively function.

[0038] In a second aspect, a method for preparing a positive electrode plate is provided, comprising: providing a positive electrode current collector, and arranging a first coating, a second coating and a conductive layer on the positive electrode current collector; wherein the first coating is arranged on the surface of at least one side of the positive electrode current collector, the conductive layer is arranged between the first coating and the second coating, the first coating includes a first active material, the second coating includes a second active material, and the second active material is different from the first active material.

[0039] In a third aspect, a battery cell is provided, comprising the positive electrode sheet according to the first aspect and any possible implementation thereof.

[0040] In a fourth aspect, a battery is provided, comprising the battery cell described in the third aspect.

[0041] In a fifth aspect, an electrical device is provided, comprising the battery described in the fourth aspect.

[0042] The present invention provides a positive electrode sheet comprising a positive electrode current collector, a first coating layer, a second coating layer, and a conductive layer. Specifically, the first coating layer is disposed on at least one surface of the positive electrode current collector, and the conductive layer is disposed between the first coating layer and the second coating layer. The first active material included in the first coating layer and the second active material included in the second coating layer are different. In other words, the positive electrode active material comprises two different materials, the first active material and the second active material. This allows the positive electrode sheet to combine the advantages of both the first and second active materials, thereby improving the overall performance of the battery. On the other hand, due to differences in material properties between the first and second active materials, such as different electronic conductivities, direct contact between the first and second active materials can affect each other, reducing the performance of both active materials and thus affecting battery performance. Therefore, the conductive layer is used to separate the first and second coating layers, preventing direct contact between the first and second active materials while also electrically connecting the first and second active materials. In other words, the conductive layer prevents direct contact between the first and second active materials while ensuring electrical connection between them, allowing the first and second active materials to leverage their respective advantages and improving the overall performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 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.

[0044] FIG1 is a schematic diagram of a positive electrode sheet according to an embodiment of the present application;

[0045] FIG2 is a schematic diagram of a positive electrode sheet according to an embodiment of the present application;

[0046] FIG3 is a schematic diagram of a method for preparing a positive electrode sheet according to an embodiment of the present application;

[0047] FIG4 is a schematic diagram of a battery cell disclosed in an embodiment of the present application;

[0048] FIG5 is a schematic diagram of the exploded structure of a battery cell disclosed in one embodiment of the present application;

[0049] FIG6 is a schematic diagram of the exploded structure of a battery disclosed in one embodiment of the present application;

[0050] FIG7 is a schematic diagram of an electrical device disclosed in an embodiment of the present application.

[0051] In the drawings, the drawings are not drawn to scale.

[0052] The accompanying drawings in the specific implementation manner are as follows:

[0053] Positive electrode sheet 1, positive electrode current collector 10, first coating layer 11, second coating layer 12, conductive layer 13, battery 10, box 11, battery cell 20, shell 21, electrode assembly 22, cover plate 23. DETAILED DESCRIPTION

[0054] Below, with appropriate reference to the accompanying drawings, the embodiments of the positive electrode sheet and its preparation method, battery cell, battery and electrical device of the present application are specifically disclosed in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0055] 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.

[0056] " 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.

[0057] 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), which means 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), which means 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.

[0058] 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.

[0059] 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).

[0060] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0061] 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.

[0062] 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.

[0063] The positive electrode sheet consists of a positive current collector and a positive active material coated on the surface of the positive current collector. The positive active material is a key factor influencing battery performance. To improve the overall performance of the battery, such as achieving both good cycle performance and high energy density, two or more positive active materials are coated on the surface of the positive current collector. However, different active materials have different electrochemical properties. For example, different electronic conductivities can lead to poor contact between different active materials, affecting the overall conductivity of the positive active material and, consequently, battery performance.

[0064] In view of this, an embodiment of the present application provides a positive electrode plate, comprising a positive electrode collector, a first coating, a second coating and a conductive layer. Specifically, the first coating is arranged on the surface of at least one side of the positive electrode collector, and the conductive layer is arranged between the first coating and the second coating. The first active material included in the first coating and the second active material included in the second coating are different, that is, the positive electrode active material includes two different materials, the first active material and the second active material. In this way, the positive electrode active material provided by the positive electrode plate can have the advantages of both the first active material and the second active material, which is beneficial to improving the overall performance of the battery. On the other hand, the conductive layer is used to separate the first coating and the second coating to avoid direct contact between the first active material and the second active material, while electrically connecting the first active material and the second active material. In other words, the provision of the conductive layer not only avoids direct contact between the first active material and the second active material, but also ensures electrical connection between the first active material and the second active material, so that the first active material and the second active material can play their respective advantages, thereby improving the overall performance of the battery.

[0065] The following describes in detail several embodiments of the present application.

[0066] [Positive electrode]

[0067] FIG1 is a schematic diagram of a positive electrode plate according to an embodiment of the present application. As shown in FIG1 , the positive electrode plate 1 includes a positive electrode current collector 10 , a first coating layer 11 , a second coating layer 12 and a conductive layer 13 .

[0068] The conductive layer 13 is disposed between the first coating layer 11 and the second coating layer 12. The first coating layer is disposed on the surface of the positive electrode current collector 10. For example, as shown in FIG1 , along the thickness direction of the positive electrode sheet 1 (the z direction in FIG1 ), the positive electrode current collector 10, the first coating layer 11, the conductive layer 13, and the second coating layer 12 are disposed in sequence.

[0069] The positive electrode current collector 10 has two surfaces arranged along its thickness direction, and the first coating layer 11, the conductive layer 13, and the second coating layer 12 are arranged on the surface of the same side of the positive electrode current collector 10. Alternatively, as shown in FIG1 , both surfaces of the positive electrode current collector 10 are provided with the first coating layer 11, the conductive layer 13, and the second coating layer 12.

[0070] FIG2 is a schematic diagram of a positive electrode sheet according to an embodiment of the present application. In some other embodiments, as shown in FIG2 , one of two opposite surfaces of the positive electrode current collector 10 along the thickness direction is provided with a first coating layer 11 , a conductive layer 13 , and a second coating layer 12 .

[0071] The first coating layer 11 includes a first active material, and the second coating layer 12 includes a second active material, which is different from the first active material.

[0072] Optionally, the first active material and the second active material have different crystal structures, wherein the crystal structure can represent the spatial arrangement of atoms in the material. For example, the first active material includes a phosphate material having an olivine structure and a material having a spinel structure, and the second active material includes a transition metal oxide having a layered structure. The material having an olivine structure can include a variety of materials, such as lithium iron phosphate (LiFePO4) and lithium manganese iron phosphate (LiMnFePO4). The transition metal oxide having a layered structure can include a variety of materials, such as LiMO2, where M includes at least one of Co, Ni, and Mn.

[0073] Conductive layer 13 is used to separate the first active material from the second active material. The presence of conductive layer 13 reduces the risk of contact between the first and second active materials, thereby reducing the impact of the performance differences between the first and second active materials on the battery cells. Conductive layer 13 also provides electrical connection between the first and second active materials.

[0074] For example, the first active material is lithium iron phosphate with a carbon coating layer, and the second active material is a ternary material. The first active material adhering to or coating the surface of the second active material may cause electrons to aggregate on the surface of the second active material. The aggregated electrons affect the embedding of lithium ions into the second active material, thereby affecting the cycle performance of the battery cell. By providing the conductive layer 13, the conductive layer 13 isolates the first active material and the second active material, thereby reducing the risk of the first active material adhering to or coating the second active material, and improving the aggregation of electrons on the surface of the second active material due to the difference in electrical conductivity between the first active material and the second active material, thereby reducing the risk of aggregated electrons embedding lithium ions into the second active material, and improving the cycle performance of the battery cell.

[0075] The cycling performance of a battery cell can be measured by its capacity retention, which is the ratio of retained capacity to initial discharge capacity. Retained capacity refers to the discharge capacity of a battery cell after completing a certain number of charge and discharge cycles. Initial discharge capacity refers to the discharge capacity of a battery cell during its first charge and discharge test.

[0076] Alternatively, the positive electrode current collector 10 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 layer and a metal layer formed on at least one surface of the polymer material base layer. 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 made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0077] The embodiment of the present application provides a positive electrode plate 1, comprising a positive electrode current collector 10, a first coating layer 11, a second coating layer 12 and a conductive layer 13. The first active material included in the first coating layer 11 is different from the second active material included in the second coating layer 12, that is, the positive electrode active material includes two different materials, the first active material and the second active material. In this way, the positive electrode active material provided by the positive electrode plate 1 can have the advantages of both the first active material and the second active material, thereby helping to improve the overall performance of the battery. On the other hand, the conductive layer 13 is used to separate the first coating layer 11 and the second coating layer 12 to avoid direct contact between the first active material and the second active material, while electrically connecting the first active material and the second active material. In other words, the provision of the conductive layer 13 not only avoids direct contact between the first active material and the second active material, but also ensures electrical connection between the first active material and the second active material, so that the first active material and the second active material can play their respective advantages, thereby improving the overall performance of the battery.

[0078] Optionally, in some embodiments, the first active material includes at least one of an olivine-structured phosphate material and a spinel material.

[0079] 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. Olivine structure phosphates have the advantages of high theoretical specific capacity, good cycle stability, low cost and environmental friendliness. Spinel is a mineral composed of magnesium aluminum oxide, with tetrahedral and octahedral crystal forms. For example, spinel-type lithium manganese oxide materials have outstanding characteristics such as high specific capacity, low cost and low environmental pollution. Olivine structure phosphate materials and spinel materials are used as the first active material, which is beneficial to improving the performance of the battery.

[0080] Optionally, the olivine structure phosphate material includes Li a Fe b M 1-b P 1-m O 4-n , wherein M includes at least one of the other metal elements except Fe, wherein 0≤a≤1.1, 0.3≤b≤1, 0≤m≤0.1, 0≤n≤0.1, optionally, M includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge, optionally, the olivine structure phosphate material includes at least one of LiFePO4 and LiMnFePO4.

[0081] It should be understood that the battery will be accompanied by lithium deintercalation and consumption during the charging and discharging process. The molar content of lithium is different when the battery is discharged to different states. a Fe b M 1-b P 1-m O 4-n The range of a is limited to include the molar content of lithium under different charge and discharge states of the battery (usually the battery voltage is between 2V and 5V).

[0082] It should be understood that the above-mentioned LiFePO4 and LiMnFePO4 are merely illustrative of the substances used as the first active material in the embodiments of the present application, and do not constitute a limitation on the first active material of the present application.

[0083] LiFePO4 has advantages such as long cycle life, good thermal stability, and high energy density; LiMnFePO4 also has advantages such as long cycle life and good thermal stability. Using LiFePO4 and LiMnFePO4 as the first active material can improve the battery's cycle performance, energy density, and safety.

[0084] Optionally, the spinel material includes LiNi c Mn 2-c O4, wherein 0≤c<2, optionally, the spinel material includes lithium manganate (LiMn2O4).

[0085] It should be understood that the above-mentioned LiMn2O4 is only an exemplary description of the substance used as the first active material in the embodiments of the present application, and does not constitute a limitation on the first active material of the present application.

[0086] LiMn2O4 used as positive electrode active material has the advantages of low price, high potential, environmental friendliness, high safety performance and good rate performance.

[0087] Optionally, in some embodiments, the second active material comprises a layered transition metal oxide.

[0088] Layered transition metal oxides are a class of oxides with multilayered (generally two-dimensional) structures. They are derived from the redox reaction of transition metal cations with lattice oxygen anions and possess high energy and power density. Using layered transition metal oxides as a second active material can improve the energy density of batteries.

[0089] Optionally, the layered transition metal oxide includes LiCoO2, LiMnO2, LiNiO2, Li a’ Ni x Co y M 1 1-x-y O 2+d 、zLi2MnO3·(1-z)LiM 2 At least one of O2, wherein M 1 Including at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, La, M 2 Including at least one of Co, Ni, and Mn, 0.5≤x≤1.0, 0≤y<0.5, x+y<1, 0.2≤a'<1.2, -0.02≤d<0.02, 0<z<1, optionally, the layered transition metal oxide includes Li(Ni 0.6 Co 0.2 Mn 0.2 ) 1.15 O2、Li(Ni 0.5 Co 0.2 Mn 0.3 ) 1.07 At least one of O2.

[0090] Lithium nickel cobalt manganese oxide (NCM) used as positive electrode active material has the advantages of high energy density, high voltage platform, good thermal stability and good cycle performance.

[0091] It should be understood that the above-mentioned NCM is only an exemplary description of the substance used as the second active material in the embodiments of the present application, and does not constitute a limitation on the second active material of the present application.

[0092] For example, the second active material may include ternary materials, lithium-rich manganese-based materials, and disordered rock salt phase structure materials. "Ternary materials" refer to materials composed of three chemical components (elements) and components (single substances and compounds). For example, ternary materials used as positive electrode active materials for batteries are usually synthesized from nickel salts, cobalt salts, and manganese salts / aluminum salts as raw materials. They contain three elements of nickel, cobalt, and manganese (or nickel, cobalt, and aluminum). The ratio of nickel, cobalt, and manganese (or nickel, cobalt, and aluminum) in the ternary material can be adjusted according to actual needs, and it has the advantages of high energy density and good cycle performance. Ternary materials, lithium-rich manganese-based materials, and disordered rock salt phase structure materials are used as the second active material to improve the performance of the battery.

[0093] Optionally, in some embodiments, the conductive layer 13 includes a conductive agent and a binder.

[0094] Conductive agents collect microcurrents between active materials, reducing electrode contact resistance and accelerating electron mobility. They also effectively increase the migration rate of metal ions within the electrode material, thereby improving the electrode's charge and discharge efficiency. Binders bond the active material to the conductive agent, enhancing electrical contact between them and stabilizing the structure of the positive electrode.

[0095] Optionally, the conductive layer 13 does not include active materials, but only includes a conductive agent and a binder.

[0096] Optionally, the conductive layer 13 is a porous film having a conductive agent and a binder.

[0097] Optionally, the conductive layer 13 may be bonded to the first coating layer 11 and the second coating layer 12 , thereby reducing the risk of deformation and wrinkling of the positive electrode plate 1 .

[0098] Optionally, in some embodiments, the conductive agent includes at least one of conductive carbon black, superconducting carbon, carbon dots, Ketjen black, and carbon nanotubes.

[0099] Due to the unique composition of carbon structure, carbon material conductive agents have good conductive properties. For example, conductive carbon black has low resistance and high conductivity, small particle size, large and rough specific surface area, high structure, clean surface (few compounds), etc. Ketjen black has a unique branched chain morphology, which makes it highly conductive. The carbon atoms in carbon nanotubes adopt SP 2Hybridization gives it high modulus and high strength. Carbon nanotubes also have good flexibility, stretchability and electrical conductivity. Conductive carbon black, superconducting carbon, carbon dots, Ketjen black and carbon nanotubes as conductive agents can improve the conductivity of batteries.

[0100] Optionally, in some embodiments, the binder includes polyvinylidene fluoride, styrene polybutadiene rubber, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trichloroethylene copolymer and at least one of fluorine-containing acrylic resin, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, and polyarylate.

[0101] Optionally, in some embodiments, as shown in FIG. 1 and FIG. 2 , the thickness d3 of the conductive layer 13 is 1 μm to 15 μm. Optionally, the thickness d3 of the conductive layer 13 is 5 μm to 10 μm.

[0102] Specifically, the thickness d3 of the conductive layer 13 may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a value between any two of the above values.

[0103] On the one hand, the thickness of the conductive layer 13 should not be too small, so that the conductive layer 13 can effectively isolate the first active material from the second active material. On the other hand, the thickness of the conductive layer 13 should not be too large, so as to ensure that the content of active material in the positive electrode sheet is not too small, thereby ensuring the energy density of the battery.

[0104] Optionally, in some embodiments, as shown in FIG. 1 and FIG. 2 , the thickness d1 of the first coating layer 11 is 40 μm to 160 μm. Optionally, the thickness d1 of the first coating layer 11 is 70 μm to 140 μm.

[0105] Specifically, the thickness d1 of the first coating layer 11 may be 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, or a value between any two of the above values.

[0106] The thickness of the first coating 11 should not be too large to reduce the waste of the first active material and reduce the total volume of the battery, thereby reducing production costs. The thickness of the first coating should not be too small to ensure that the content of the first active material in the positive electrode sheet is not too small, which is beneficial to improving battery performance.

[0107] Optionally, in some embodiments, as shown in FIG. 1 and FIG. 2 , the thickness d2 of the second coating layer 12 is 40 μm to 80 μm. Optionally, the thickness d2 of the second coating layer 12 is 40 μm to 60 μm.

[0108] Specifically, the thickness d2 of the second coating layer 12 may be 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, or a value between any two of the above values.

[0109] The thickness of the second coating should not be too large to reduce the waste of the second active material and reduce the total volume of the battery, thereby reducing production costs. The thickness of the second coating should not be too small to ensure that the content of the second active material in the positive electrode sheet is not too small, which is beneficial to improving battery performance.

[0110] Optionally, in some embodiments, based on the total weight of the conductive layer, the weight percentage of the binder in the conductive layer is 1 wt % to 10 wt %, optionally 3 wt % to 7 wt %.

[0111] Specifically, the weight percentage of the binder in the conductive layer can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or a value between any two of the above values.

[0112] Optionally, in some embodiments, based on the total weight of the conductive layer, the weight percentage of the conductive agent in the conductive layer is 90 wt % to 99 wt %, optionally, 93 wt % to 97 wt %.

[0113] Specifically, the weight percentage of the conductive agent in the conductive layer is 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, 99wt%, or a value between any two of the above values.

[0114] The conductive agent in the conductive layer collects microcurrents between the active materials, reducing the contact resistance of the electrodes and accelerating the movement of electrons. It also effectively increases the migration rate of metal ions in the electrode material, thereby improving the charge and discharge efficiency of the electrodes. Too little conductive agent reduces the electron conduction channels in the positive electrode sheet, resulting in low utilization of the positive electrode active material, thereby reducing the battery's cycle performance and energy density. Therefore, setting the conductive agent content in the conductive layer to 90wt% to 99wt% is beneficial to improving the overall performance of the battery.

[0115] In the above technical solution, by setting the weight contents of the conductive agent and the binder in the conductive layer 13 within an appropriate range, the conductive layer 13 can effectively play its role of isolating and electrically connecting the first active material and the second active material, thereby improving the overall performance of the battery.

[0116] Optionally, in some embodiments, based on the total weight of the first coating layer, the weight percentage of the first active material is 90 wt % to 98 wt %, optionally, 96 wt % to 97 wt %.

[0117] Specifically, the weight percentage of the first active material in the first coating can be 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, or a value between any two of the above values.

[0118] Optionally, in some embodiments, based on the total weight of the first coating layer, the weight percentage of the conductive agent in the first coating layer is 0.1 wt% to 1 wt%, optionally, 0.4 wt% to 0.6 wt%.

[0119] Specifically, the weight percentage of the conductive agent in the first coating can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or a value between any two of the above values.

[0120] Optionally, in some embodiments, based on the total weight of the first coating layer, the weight percentage of the binder in the first coating layer is 1 wt% to 2 wt%, optionally, 1.2 wt% to 1.4 wt%.

[0121] Specifically, the weight percentage of the binder in the first coating can be 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, or a value between any two of the above values.

[0122] In the above technical solution, the weight contents of the first active material, the conductive agent and the binder in the first coating layer 11 are set within an appropriate range, so that the first active material can effectively function.

[0123] Optionally, in some embodiments, based on the total weight of the second coating layer, the weight percentage of the second active material is 90 wt % to 98 wt %, optionally 96 wt % to 97 wt %.

[0124] Specifically, the weight percentage of the second active material in the second coating can be 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, or a value between any two of the above values.

[0125] Optionally, in some embodiments, based on the total weight of the second coating layer, the weight percentage of the conductive agent in the second coating layer is 0.1 wt% to 1 wt%, optionally, 0.4 wt% to 0.6 wt%.

[0126] Specifically, the weight percentage of the conductive agent in the second coating can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or a value between any two of the above values.

[0127] Optionally, in some embodiments, based on the total weight of the second coating layer, the weight percentage of the binder in the second coating layer is 1 wt% to 2 wt%, optionally, 1.2 wt% to 1.4 wt%.

[0128] Specifically, the weight percentage of the binder in the first coating can be 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, or a value between any two of the above values.

[0129] In the above technical solution, the weight contents of the second active material, the conductive agent and the binder in the second coating layer 12 are set within an appropriate range, so that the second active material can effectively function.

[0130] [Preparation method of positive electrode sheet]

[0131] FIG3 shows a method for preparing a positive electrode sheet according to an embodiment of the present application. As shown in FIG3 , the method 300 includes the following steps.

[0132] Step 310 : providing a positive electrode current collector, and disposing a first coating layer, a second coating layer, and a conductive layer on the positive electrode current collector.

[0133] The first coating is arranged on the surface of at least one side of the positive electrode current collector, the conductive layer is arranged between the first coating and the second coating, the first coating includes a first active material, the second coating includes a second active material, and the second active material is different from the first active material.

[0134] The positive electrode sheet prepared by the above method is beneficial to improving the performance of the battery when used in the battery.

[0135] [Negative electrode]

[0136] 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.

[0137] 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.

[0138] 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.).

[0139] 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.

[0140] 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).

[0141] 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.

[0142] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0143] 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.

[0144] [Electrolytes]

[0145] 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.

[0146] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] [Isolation film]

[0151] 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.

[0152] 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.

[0153] 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.

[0154] The battery cell, battery and electrical device of the present application are described below with reference to the accompanying drawings.

[0155] The present application also provides a battery cell. The battery cell includes the positive electrode sheet, negative electrode sheet, electrolyte, and separator described in the above embodiments. 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 disposed between the positive and negative electrode sheets, primarily to prevent a short circuit between the positive and negative electrodes while allowing ions to pass through.

[0156] 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.

[0157] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] As the electrical device, a battery cell, a battery module or a battery can be selected according to its usage requirements.

[0166] 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.

[0167] 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.

[0168] [Example]

[0169] 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.

[0170] (1) Preparation of positive electrode sheet

[0171] Positive electrode sheet 1: Lithium iron phosphate (LiFePO4), conductive carbon black, carbon nanotubes (CNT), and polyvinylidene fluoride (PVDF) are dissolved in a solvent N-methylpyrrolidone (NMP) in a weight ratio of 97.6:0.6:0.4:1.4, and the first coating is formed after stirring and mixing evenly.

[0172] Lithium nickel cobalt manganese oxide (NCM622), conductive carbon black, CNT, and PVDF were dissolved in a solvent NMP in a weight ratio of 97.6:0.6:0.4:1.4, and the mixture was stirred and mixed to form a second coating.

[0173] The binder carboxymethyl cellulose (CMC) and the conductive agent conductive carbon black are dissolved in the solvent deionized water in a weight ratio of 3:97, and the mixture is stirred and mixed to form a conductive layer.

[0174] The first coating layer, the second coating layer, and the conductive layer are applied to the positive electrode current collector simultaneously or in steps using extrusion coating according to the structure of the positive electrode plate shown in Figure 1 or Figure 2 in the embodiment of the present application (for example, the first coating layer, the second coating layer, and the conductive layer can be applied to the positive electrode current collector simultaneously using an LOM extrusion coater) to produce a positive electrode plate 1. The thickness of the first coating layer is 130 μm, the thickness of the second coating layer is 50 μm, and the thickness of the conductive layer is 1 μm.

[0175] Positive electrode sheet 2: Positive electrode sheet 2 is different from positive electrode sheet 1, except that the thickness of the conductive layer is 5 μm, thus obtaining positive electrode sheet 2.

[0176] Positive electrode sheet 3: Positive electrode sheet 3 is different from positive electrode sheet 1, except that the thickness of the conductive layer is 10 μm, thus producing positive electrode sheet 3.

[0177] Positive electrode sheet 4: The difference between the positive electrode sheet 4 and the positive electrode sheet 1 is that the thickness of the conductive layer is 15 μm, and the positive electrode sheet 4 is obtained.

[0178] Positive electrode sheet 5: Positive electrode sheet 5 is different from positive electrode sheet 2 in that the thickness of the first coating layer is 40 μm, thereby obtaining positive electrode sheet 5.

[0179] Positive electrode sheet 6: The difference between the positive electrode sheet 6 and the positive electrode sheet 2 is that the thickness of the first coating layer is 70 μm, thus obtaining the positive electrode sheet 6.

[0180] Positive electrode sheet 7: Positive electrode sheet 7 is different from positive electrode sheet 2, except that the thickness of the first coating layer is 140 μm, thus producing positive electrode sheet 7.

[0181] Positive electrode sheet 8: The difference between the positive electrode sheet 8 and the positive electrode sheet 2 is that the thickness of the first coating layer is 160 μm, thereby obtaining the positive electrode sheet 8.

[0182] Positive electrode sheet 9: Positive electrode sheet 9 is different from positive electrode sheet 2 in that the thickness of the second coating layer is 40 μm, thereby obtaining positive electrode sheet 9.

[0183] Positive electrode sheet 10 : The positive electrode sheet 10 is different from the positive electrode sheet 2 , except that the thickness of the second coating layer is 60 μm, thereby obtaining the positive electrode sheet 10 .

[0184] Positive electrode sheet 11: The positive electrode sheet 11 is different from the positive electrode sheet 2, except that the thickness of the second coating layer is 80 μm, thereby obtaining the positive electrode sheet 11.

[0185] Positive electrode sheet 12: The difference between positive electrode sheet 12 and positive electrode sheet 2 is that lithium manganese iron phosphate (LiMnFePO4), conductive carbon black, CNT, and PVDF are dissolved in solvent NMP in a weight ratio of 97.6:0.6:0.4:1.4, and then stirred and mixed evenly to form a first coating. The thickness of the first coating is 130 μm, and the positive electrode sheet 12 is obtained.

[0186] Positive electrode sheet 13: Positive electrode sheet 13 is different from positive electrode sheet 2 in that LiCoO2, conductive carbon black, CNT, and PVDF are dissolved in solvent NMP in a weight ratio of 97.6:0.6:0.4:1.4, and then stirred and mixed evenly to form a second coating. The thickness of the second coating is 50 μm, thereby obtaining positive electrode sheet 13.

[0187] Positive electrode sheet 14 : The positive electrode sheet 14 is different from the positive electrode sheet 2 , except that the thickness of the conductive layer is 20 μm.

[0188] Positive electrode sheet 15 : The positive electrode sheet 15 is different from the positive electrode sheet 2 , except that the thickness of the first coating layer is 30 μm, thereby obtaining the positive electrode sheet 15 .

[0189] Positive electrode sheet 16 : The positive electrode sheet 16 is different from the positive electrode sheet 2 , except that the thickness of the first coating layer is 170 μm, thereby obtaining the positive electrode sheet 16 .

[0190] Positive electrode sheet 17: Positive electrode sheet 17 is different from positive electrode sheet 2, except that the thickness of the second coating layer is 30 μm, thereby obtaining positive electrode sheet 17.

[0191] Positive electrode sheet 18 : The positive electrode sheet 18 is different from the positive electrode sheet 2 , except that the thickness of the second coating layer is 90 μm, thereby obtaining the positive electrode sheet 18 .

[0192] Positive electrode sheet 19: Positive electrode sheet 19 is different from positive electrode sheet 2, except that the weight ratio of the binder CMC and the conductive agent conductive carbon black in the conductive layer is 10:90, thereby obtaining positive electrode sheet 19.

[0193] Positive electrode sheet 20 : The positive electrode sheet 20 is different from the positive electrode sheet 2 , except that the weight ratio of the binder CMC and the conductive agent conductive carbon black in the conductive layer is 7:93, thereby producing the positive electrode sheet 20 .

[0194] Positive electrode sheet 21: The positive electrode sheet 21 is different from the positive electrode sheet 2, except that the weight ratio of the binder CMC and the conductive agent conductive carbon black in the conductive layer is 1:99, thereby obtaining the positive electrode sheet 21.

[0195] Positive electrode sheet 22: The positive electrode sheet 22 is different from the positive electrode sheet 2 in that no conductive layer is provided.

[0196] (2) Preparation of negative electrode sheet

[0197] Artificial graphite, conductive carbon black, styrene-butadiene rubber (SBR), and CMC are dissolved in deionized water in a weight ratio of 95.5:1.2:1.3:1.5, and evenly mixed to prepare a negative electrode slurry; the negative electrode slurry is then evenly coated on the negative electrode collector, dried to obtain a negative electrode film, and then cold pressed and cut to obtain a negative electrode sheet.

[0198] (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.

[0199] (4) Preparation of isolation film: Conventional polypropylene film was used as the isolation film.

[0200] (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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] Example 17: The 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 Example 17.

[0218] Example 18: The 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 Example 18.

[0219] Example 19: The 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 Example 19.

[0220] Example 20: The 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 Example 20.

[0221] Example 21: The 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 Example 21.

[0222] Comparative Example 1: A lithium-ion battery obtained by assembling the positive electrode sheet 22, the separator, the negative electrode sheet, and the electrolyte according to the above method is Comparative Example 1.

[0223] The product parameters of different embodiments are detailed in Table 1.

[0224] Table 1: Product parameters of comparative examples and different embodiments

[0225] Next, the testing process of relevant parameters is explained.

[0226] 1. Cycle performance test

[0227] At 25 / 45°C, the battery cell is first charged to 4.3V at a constant current of 1C, then further charged at a constant voltage of 4.3V to a current of 0.05C, and then discharged to 3V at a constant current of 1C. This constitutes one charge-discharge cycle, and the discharge capacity at this time is the discharge capacity of the first cycle. The battery is subjected to multiple charge-discharge cycles as described above, and the discharge capacity of the 200th cycle is measured. The capacity retention rate of the battery cell after 200 cycles is calculated using the following formula: Capacity retention rate (%) after 200 cycles = [discharge capacity at the 200th cycle / discharge capacity at the 1st cycle] × 100%.

[0228] 2. Energy density test

[0229] At room temperature (25℃±2℃), discharge to the lower limit voltage in the form of constant current discharge (1 / 3C rate), let it stand for 30 minutes, and then charge to the upper limit cut-off voltage in a constant current and constant voltage charging mode (constant current 1 / 3C, constant voltage charging to 1 / 20C), let it stand for 30 minutes, and calculate the discharge energy E (in Wh). Repeat 3 times, take the average value of the 3 discharge energies E as E0, divide it by the volume V of the hard shell battery cell, and the volume energy density (in Wh / L) = E0 / V.

[0230] The battery performance tests were performed on the comparative example 1 and examples 1-21 prepared according to the above method. The results are shown in Table 2.

[0231] Table 2: Performance test results of comparative examples and different embodiments

[0232] From the comparison of the results of Comparative Example 1 and Examples 1-4, it can be seen that providing a conductive layer between the first coating layer and the second coating layer to connect the first active material and the second active material can improve the cycle performance of the battery.

[0233] From the comparison of the results of Examples 1-4 and 14, it can be seen that the thickness of the conductive layer needs to be set within an appropriate range. If the thickness of the conductive layer is too large, the proportion of active material in the active material layer will be reduced, which will reduce the energy density of the battery.

[0234] From the comparison of the results of Examples 2 and 19-21, it can be seen that when the thickness of the conductive layer is constant, within a certain range, the higher the content of the conductive agent in the conductive layer, the better the cycle performance of the battery and the higher the energy density.

[0235] 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: Positive electrode current collector; A first coating layer, the first coating layer is disposed on a surface of at least one side of the positive electrode current collector, and the first coating layer includes a first active material; a second coating, the second coating comprising a second active material, the second active material being different from the first active material; A conductive layer is disposed between the first coating layer and the second coating layer and is used to isolate the first coating layer from the second coating layer.

2. The positive electrode sheet according to claim 1, wherein: The first active material includes at least one of an olivine structure phosphate material and a spinel material.

3. The positive electrode sheet according to claim 2, wherein: The olivine structure phosphate material includes Li a Fe b M 1-b P 1-m O 4-n , wherein M includes at least one of the other metal elements except Fe, wherein 0≤a≤1.1, 0.3≤b≤1, 0≤m≤0.1, 0≤n≤0.1, optionally, M includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge, optionally, the olivine structure phosphate material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

4. The positive electrode sheet according to claim 2 or 3, wherein: The spinel material includes LiNi c Mn 2-c O4, wherein 0≤c<2, optionally, the spinel material comprises lithium manganate.

5. The positive electrode sheet according to any one of claims 1 to 4, wherein: The second active material includes a layered transition metal oxide.

6. The positive electrode sheet according to claim 5, wherein: The layered transition metal oxides include LiCoO2, LiMnO2, LiNiO2, Li a’ Ni x Co y M 1 1-x-y O 2+d 、zLi2MnO3·(1-z)LiM 2 O2 at least one, wherein M 1 Including at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, La, M 2 The layered transition metal oxide comprises at least one of Co, Ni and Mn, 0.5≤x≤1.0, 0≤y<0.5, x+y<1, 0.2≤a'<1.2, -0.02≤d<0.02, 0<z<1, and optionally, the layered transition metal oxide comprises Li(Ni 0.6 Co 0.2 Mn 0.2 ) 1.15 O2、Li(Ni 0.5 Co 0.2 Mn 0.3 ) 1.07 At least one of O2.

7. The positive electrode sheet according to any one of claims 1 to 6, wherein: The conductive layer includes a conductive agent and a binder.

8. The positive electrode sheet according to claim 7, wherein: The conductive agent includes at least one of conductive carbon black, superconducting carbon, carbon dots, Ketjen black and carbon nanotubes.

9. The positive electrode sheet according to claim 7 or 8, wherein: The binder includes at least one of polyvinylidene fluoride, styrene polybutadiene rubber, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trichloroethylene copolymer and fluorine-containing acrylic resin, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, and polyarylate.

10. The positive electrode sheet according to any one of claims 1 to 9, wherein: The thickness of the conductive layer is 1 μm to 15 μm. Optionally, the thickness of the conductive layer is 5 μm to 10 μm.

11. The positive electrode sheet according to any one of claims 1 to 10, wherein: The thickness of the first coating layer is 40 μm to 160 μm. Optionally, the thickness of the first coating layer is 70 μm to 140 μm.

12. The positive electrode sheet according to any one of claims 1 to 11, wherein: The thickness of the second coating layer is 40 μm to 80 μm. Optionally, the thickness of the second coating layer is 40 μm to 60 μm.

13. The positive electrode sheet according to any one of claims 1 to 12, wherein: Based on the total weight of the conductive layer, the weight percentage of the binder in the conductive layer is 1 wt % to 10 wt %, and optionally, 3 wt % to 7 wt %.

14. The positive electrode sheet according to any one of claims 1 to 13, wherein: Based on the total weight of the conductive layer, the weight percentage of the conductive agent in the conductive layer is 90wt% to 99wt%, and optionally, 93wt% to 97wt%.

15. The positive electrode sheet according to any one of claims 1 to 14, wherein: Based on the total weight of the first coating layer, the weight percentage of the first active material is 90 wt % to 98 wt %, and optionally, 96 wt % to 97 wt %.

16. The positive electrode sheet according to any one of claims 1 to 15, wherein: Based on the total weight of the first coating layer, the weight percentage of the conductive agent in the first coating layer is 0.1 wt% to 1 wt%, and optionally, 0.4 wt% to 0.6 wt%.

17. The positive electrode sheet according to any one of claims 1 to 16, wherein: Based on the total weight of the first coating layer, the weight percentage of the binder in the first coating layer is 1 wt % to 2 wt %, and optionally, 1.2 wt % to 1.4 wt %.

18. The positive electrode sheet according to any one of claims 1 to 17, wherein: Based on the total weight of the second coating layer, the weight percentage of the second active material is 90 wt % to 98 wt %, and optionally, 96 wt % to 97 wt %.

19. The positive electrode sheet according to any one of claims 1 to 18, wherein: Based on the total weight of the second coating layer, the weight percentage of the conductive agent in the second coating layer is 0.1 wt % to 1 wt %, and optionally, 0.4 wt % to 0.6 wt %.

20. The positive electrode sheet according to any one of claims 1 to 19, wherein: Based on the total weight of the second coating layer, the weight percentage of the binder in the second coating layer is 1 wt % to 2 wt %, and optionally, 1.2 wt % to 1.4 wt %.

21. A method for preparing a positive electrode sheet, comprising: Providing a positive electrode current collector, on which a first coating layer, a second coating layer and a conductive layer are disposed; The first coating is disposed on the surface of at least one side of the positive electrode current collector, the conductive layer is disposed between the first coating and the second coating, the first coating includes a first active material, the second coating includes a second active material, and the second active material is different from the first active material.

22. A battery cell comprising the positive electrode sheet according to any one of claims 1 to 20.

23. A battery comprising the battery cell according to claim 22.

24. An electrical device comprising the battery according to claim 23.

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