Positive electrode sheet, method for manufacturing the same, battery cell, battery, and power using device

Abstract

The application provides a positive electrode sheet, a preparation method thereof, a battery monomer, a battery and an electric device. The positive electrode sheet comprises a current collector, a first positive electrode active material layer and a second positive electrode active material layer. The first positive electrode active material layer is arranged on at least one side of the current collector, and the second positive electrode active material layer is arranged on the first positive electrode active material layer. The first positive electrode active material layer comprises a first positive electrode active material, and the second positive electrode active material layer comprises a second positive electrode active material. The first positive electrode active material comprises a lithium-containing phosphate with an olivine structure, and the second positive electrode active material comprises a lithium metal oxide containing cobalt. The positive electrode sheet can effectively improve the influence of concentration polarization of the battery on the performance of the battery and help improve the capacity and cycle performance of the battery.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically, to a positive electrode sheet and its preparation method, a battery cell, a battery, and an electrical device. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace, resulting in tremendous development. Consequently, higher requirements have been placed on the capacity and cycle performance of lithium-ion batteries.

[0003] Battery polarization is one of the factors affecting the capacity and cycle performance of lithium-ion batteries, thus limiting their development. Therefore, reducing the impact of battery polarization on battery performance has become an urgent technical problem to be solved. Summary of the Invention

[0004] This application addresses the aforementioned technical problems and aims to provide a positive electrode sheet, its preparation method, a battery cell, a battery, and an electrical device. When applied to a battery, this positive electrode sheet effectively mitigates the impact of electrochemical polarization and electrolyte concentration polarization on battery performance, thereby helping to improve battery capacity and cycle performance.

[0005] In a first aspect, a positive electrode sheet is provided, the positive electrode sheet comprising a current collector, a first positive electrode active material layer, and a second positive electrode active material layer, wherein the first positive electrode active material layer is disposed on at least one side of the current collector, and the second positive electrode active material layer is disposed on the first positive electrode active material layer; the first positive electrode active material layer comprises a first positive electrode active material, the second positive electrode active material layer comprises a second positive electrode active material, the first positive electrode active material comprises a lithium phosphate with an olivine structure, and the second positive electrode active material comprises a cobalt-containing lithium metal oxide.

[0006] In the embodiments of this application, the positive electrode film on the positive electrode sheet has a double-layer structure. The upper layer is composed of a cobalt-containing lithium metal oxide, and the lower layer is composed of a lithium phosphate with an olivine structure. Through the arrangement of the upper and lower layers of the positive electrode film, the lithium-ion kinetics of the upper layer are superior to those of the lower layer; in other words, the lithium-ion conductivity of the upper layer is better than that of the lower layer. Therefore, by placing a second positive electrode active material with good lithium-ion kinetics on the upper layer of the positive electrode film, which has better electrolyte wetting, and a first positive electrode active material on the lower layer of the positive electrode film, which has less electrolyte wetting, the current density distribution along the thickness direction of the positive electrode sheet matches the ion kinetic properties of the positive electrode active material. This reduces the charging polarization voltage of the positive electrode sheet, thereby helping to improve the battery's capacity and cycle performance.

[0007] It should be understood that the upper layer of the positive electrode film layer described in this application is the positive electrode active material layer on the positive electrode sheet that is close to the electrolyte, such as the second positive electrode active material layer; the lower layer of the positive electrode film layer is the positive electrode active material layer on the positive electrode sheet that is close to the current collector, such as the first positive electrode active material layer.

[0008] In some embodiments, the manganese-based transition metal phosphate comprises a compound of formula (I):

[0009] Li (1+x1) Mn a1 M1 (1-a1) P (1-m) O (4-n) (I)

[0010] Where M1 represents a metallic element, -0.2≤x1≤0.2, 0.1≤a1≤0.9, 0≤m≤0.1, and 0≤n≤0.1.

[0011] In some embodiments, M1 includes one or more of Fe, Al, Cu, Cr, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb, and Ge.

[0012] In some embodiments, the cobalt-containing lithium metal oxide comprises layered cobalt-containing lithium metal oxide.

[0013] In some embodiments, the cobalt-containing lithium metal oxide comprises a compound represented by formula (II):

[0014] Li (1+x2) Co a2 M2 (1-a2) O (2-y) A y (II)

[0015] Where M2 represents a metallic element, A represents a dopant element at the oxygen site, and A includes one or more of S, F, Cl and Br, -0.2≤x2≤0.2, 0.02≤a2≤0.5, and 0≤y<2.

[0016] It should be understood that during the charging and discharging process of a battery, there will be Li insertion / extraction and consumption. The molar content of Li will be different when the battery is discharged to different states. The above limitations on x1 and x2 include the molar content of Li in different charging and discharging states of the battery (typically the battery voltage is between 2.0V and 5.0V).

[0017] In some embodiments, M2 includes one or more of Ni, Fe, Cr, Mn, Ti, Zn, V, Al, and Zr.

[0018] In some embodiments, the positive electrode active material includes a first positive electrode active material and a second positive electrode active material, wherein the mass ratio of the first positive electrode active material to the positive electrode active material is m, and the mass ratio of the second positive electrode active material to the positive electrode active material is n, wherein 0 < m < 1, 0 < n < 1, and 0 < m + n ≤ 1.

[0019] In some embodiments, the first positive electrode active material and the second positive electrode active material satisfy the following condition: 0.2 ≤ K ≤ 0.6;

[0020] in,

[0021] In the embodiments of this application, by controlling the value of K within a suitable range, the lithium-ion dynamic distribution of the positive electrode active material in the thickness direction of the positive electrode sheet can be flexibly adjusted, thereby better matching it with the current density distribution caused by the concentration polarization of the electrolyte, effectively improving the impact of electrochemical polarization and electrolyte concentration polarization on battery performance.

[0022] In some embodiments, in a battery cell including the positive electrode, the conductivity σ of the electrolyte satisfies: 3.3 mS cm⁻¹ -1 ≤σ≤13mS cm -1 .

[0023] In a second aspect, a method for preparing a positive electrode sheet is provided, the method comprising: providing a current collector; disposing a first positive electrode active material layer on the current collector; disposing a second positive electrode active material layer on the first positive electrode active material layer; wherein the first positive electrode active material layer comprises a first positive electrode active material, the second positive electrode active material layer comprises a second positive electrode active material, the first positive electrode active material comprises a lithium phosphate with an olivine structure, and the second positive electrode active material comprises a cobalt-containing lithium metal oxide.

[0024] Thirdly, a battery cell is provided, the battery cell comprising a positive electrode sheet as described in any embodiment of the first aspect, or a positive electrode sheet prepared according to the method described in any embodiment of the second aspect.

[0025] In some embodiments, the battery cell includes an electrolyte, the conductivity σ of which satisfies: 3.3 mS / cm -1 ≤σ≤13mS cm -1 .

[0026] Fourthly, a battery is provided, the battery comprising a battery cell as described in any embodiment of the third aspect.

[0027] Fifthly, an electrical device is provided, the electrical device comprising a battery cell in any embodiment of the third aspect and / or a battery in any embodiment of the fourth aspect. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort. In the drawings, the drawings are not drawn to scale.

[0029] Figure 1 This is a schematic structural diagram of a positive electrode sheet according to this application.

[0030] Figure 2 This is a SEM image of a positive electrode sheet according to this application.

[0031] Figure 3 This is a schematic flowchart illustrating a method for preparing a positive electrode sheet according to this application.

[0032] Figure 4 This is a schematic diagram of a battery cell according to this application.

[0033] Figure 5 This is a schematic diagram of a battery module according to this application.

[0034] Figure 6 This is a schematic diagram of a battery according to this application.

[0035] Figure 7 This is another schematic diagram of a battery according to this application. Detailed Implementation

[0036] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode sheet and its preparation method, battery cell, battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0037] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the allowable tolerance range. "Parallel" is not parallel in the strict sense, but within the allowable tolerance range.

[0039] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0040] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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).

[0041] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their technically accepted meanings.

[0045] Typically, a battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through. In some embodiments, the battery described in this application is also referred to as a secondary battery.

[0046] This application takes lithium-ion batteries as an example. Lithium-ion batteries are a typical type of rechargeable battery. Because they rely on the chemical reaction of lithium ions intercalating and deintercalating between the positive and negative electrodes for charging and discharging, lithium-ion batteries are also known as rocking chair batteries. During the charging process of a lithium-ion battery, lithium ions are extracted from the positive electrode, move, and intercalate into the negative electrode; while during the discharging process, lithium ions are extracted from the negative electrode, move, and intercalate into the positive electrode.

[0047] It should be understood that the “lithium intercalation” or “intercalation” process described in this application refers to the process in which lithium ions are intercalated into the positive electrode material and the negative electrode material due to an electrochemical reaction, while the “deintercalation”, “delithiation”, or “deintercalation” process described in this application refers to the process in which lithium ions are deintercalated into the positive electrode material and the negative electrode material due to an electrochemical reaction.

[0048] With the increasingly widespread application of lithium-ion batteries, higher requirements are being placed on battery capacity and cycle performance. Battery polarization is one of the reasons why lithium-ion batteries easily suffer capacity loss and degraded cycle performance during charging and discharging. Battery polarization is generally classified into ohmic polarization, electrochemical polarization, and concentration polarization. Concentration polarization is caused by the diffusion rate of lithium ions participating in the battery's electrochemical reaction in the liquid or solid phase being lower than the electron transport rate in the electrochemical reaction. Electrochemical polarization is a polarization phenomenon caused by the sluggishness of the electrochemical reaction, resulting in the electrode potential deviating from the equilibrium potential. Especially in the later stages of battery charging, when the electrode components are under a high-charge state, the electrochemical and concentration polarization at the positive electrode increases significantly, severely affecting the battery's charging capacity and subsequently its discharge capacity, leading to a decrease in battery capacity. Furthermore, with battery cycling, polarization intensifies, adversely affecting the battery's cycle performance.

[0049] In view of this, embodiments of this application provide a positive electrode sheet, the film layer on which includes a first positive electrode active material layer disposed on a current collector and a second positive electrode active material layer disposed on the first positive electrode active material layer; the first positive electrode active material layer includes a first positive electrode active material, and the second positive electrode active material layer includes a second positive electrode active material; the first positive electrode active material includes a lithium phosphate with an olivine structure, and the second positive electrode active material includes a cobalt-containing lithium metal oxide. By providing a first positive electrode active material with high lithium-ion kinetics in the first positive electrode active material layer and a second positive electrode active material in the second positive electrode active material layer, the influence of electrochemical polarization and concentration polarization on battery performance can be effectively improved, helping to improve battery capacity and cycle performance.

[0050] Next, we will provide a detailed introduction to the positive electrode, negative electrode, separator, and other components in the battery.

[0051] [Positive electrode plate]

[0052] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material. It should be understood that the positive electrode film layer is the film layer disposed on the positive current collector.

[0053] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0054] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0055] Figure 1 This is a schematic structural diagram of a positive electrode sheet provided in an embodiment of this application.

[0056] like Figure 1 As shown, the positive electrode 1 includes a current collector 11 and a film layer 12 disposed on at least one side of the current collector 11.

[0057] The membrane layer 12 includes a first positive electrode active material layer 121 and a second positive electrode active material layer 122. The first positive electrode active material layer 121 is disposed on the positive electrode current collector, and the second positive electrode active material layer 122 is disposed on the first positive electrode active material layer 121.

[0058] The first positive electrode active material layer 121 includes a first positive electrode active material, and the second positive electrode active material layer 122 includes a second positive electrode active material. The first positive electrode active material includes a lithium phosphate with an olivine structure, and the second positive electrode active material includes a cobalt-containing lithium metal oxide.

[0059] Generally, the upper layer of the film 12 of the positive electrode 1 is in full contact with the electrolyte and has a good degree of wetting, allowing for a larger current to pass through during electrochemical reactions. Conversely, the lower layer of the film 12 has a lesser degree of wetting, resulting in a smaller current passing through during electrochemical reactions. Therefore, during battery polarization, the upper layer of the positive electrode 1 will be more severely polarized than the lower layer, further intensifying battery polarization and negatively impacting battery capacity retention and cycle stability.

[0060] In this embodiment, film layer 12 is the aforementioned positive electrode film layer. In the positive electrode sheet 1, the first positive electrode active material layer 121 disposed on at least one side of the current collector includes a lithium phosphate with an olivine structure, and the second positive electrode active material layer 122 disposed closer to the electrolyte includes a lithium metal oxide with cobalt. Compared with the lithium phosphate with an olivine structure, the lithium metal oxide with cobalt has higher lithium-ion kinetics, and the number of lithium ions that can be transferred during charging can be matched with a larger current; while the lithium phosphate with an olivine structure is disposed in the lower layer of film layer 12, and its lithium-ion kinetics can be matched with a smaller current.

[0061] Therefore, the embodiments of this application, through the design of the first positive electrode active material layer 121 and the second positive electrode active material layer 122 on the positive electrode sheet 1, make the kinetic performance of the positive electrode active material in the thickness direction of the positive electrode sheet 1 match the current density distribution during the charging process, effectively improve the concentration polarization during the charging process, so that the capacity of the positive electrode active material on the positive electrode sheet 1 can be fully utilized, which helps to maintain the battery capacity and improve the cycle stability of the battery.

[0062] Figure 2 A scanning electron microscope (SEM) image of a positive electrode 1 provided in an embodiment of this application.

[0063] Figure 2 The SEM morphology of the positive electrode 1 along its thickness direction is shown. It can be seen that the positive electrode 1 has a clear three-layer structure, which consists of a current collector 11 with a smooth and flat morphology, a first positive electrode active material layer 121 with a relatively dense powder morphology, and a second positive electrode active material layer 122 with a relatively loose powder morphology from bottom to top.

[0064] In some embodiments, the lithium phosphate with an olivine structure includes compounds represented by formula (I):

[0065] Li (1+x1) Mn a1 M1 (1-a1) P (1-m) O (4-n) (I)

[0066] Where M1 represents a metallic element, -0.2≤x1≤0.2, 0.1≤a1≤0.9, 0≤m≤0.1, and 0≤n≤0.1.

[0067] For example, x1 can be -0.2, -0.1, 0, 0.1, 0.2, or a value within the range of any two combinations of the aforementioned values. a1 can be 0.5, 0.6, 0.7, 0.8, 0.9, or a value within the range of any two combinations of the aforementioned values. m can be 0, 0.02, 0.04, 0.06, 0.08, 0.1, or a value within the range of any two combinations of the aforementioned values. n can be 0.02, 0.04, 0.06, 0.08, 0.1, or a value within the range of any two combinations of the aforementioned values.

[0068] In the embodiments of this application, the lithium phosphates with an olivine structure that meet the above conditions have a high manganese content, which contributes a higher voltage window in the electrochemical reaction. Therefore, selecting lithium phosphates with an olivine structure that meet the above conditions helps to further improve the energy density of the battery.

[0069] In some embodiments, M1 may include one or more of Fe, Al, Cu, Cr, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb, and Ge.

[0070] In some embodiments, the cobalt-containing lithium metal oxide comprises layered cobalt-containing lithium metal oxide.

[0071] Cobalt-containing lithium metal oxides are a widely used class of positive electrode active materials. These can include lithium nickel cobalt oxides, lithium manganese cobalt oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. It may include hexagonal structure, layered structure, etc.

[0072] In the embodiments of this application, layered cobalt-containing lithium metal oxides are selected, whose ordered layered structure can provide more lithium-ion active sites for electrochemical reactions, thereby providing higher capacity for the battery.

[0073] In some embodiments, the cobalt-containing lithium metal oxide comprises a compound represented by formula (II):

[0074] Li (1+x2) Co a2 M2 (1-a2) O (2-y) A y (II)

[0075] Where M2 represents a metallic element, A represents a dopant element at the oxygen site, and A includes one or more of S, F, Cl and Br, -0.2≤x2≤0.2, 0.02≤a2≤0.5, and 0≤y<2.

[0076] For example, x2 can be -0.2, -0.1, 0, 0.1, 0.2, or a value within the range obtained by any two of the aforementioned values. a2 can be 0.02, 0.04, 0.06, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or a value within the range obtained by any two of the aforementioned values. y can be any value from 0 to 2, or a value within the range obtained by any two of the aforementioned values.

[0077] It should be understood that during the charging and discharging process of a battery, there will be Li insertion / extraction and consumption. The molar content of Li will be different when the battery is discharged to different states. The above limitations on x1 and x2 include the molar content of Li in different charging and discharging states of the battery (typically the battery voltage is between 2.0V and 5.0V).

[0078] In some embodiments, M2 includes one or more of Ni, Fe, Cr, Mn, Ti, Zn, V, Al, and Zr.

[0079] In some embodiments, the positive electrode active material includes a first positive electrode active material and a second positive electrode active material, wherein the mass ratio of the first positive electrode active material to the positive electrode active material is m, and the mass ratio of the second positive electrode active material to the positive electrode active material is n, wherein 0 < m < 1, 0 < n < 1, and 0 < m + n ≤ 1.

[0080] Specifically, the manganese and cobalt content on the positive electrode 1 can be flexibly controlled by adjusting the mass ratio of the first positive electrode active material and the mass ratio of the second positive electrode active material in the positive electrode active material, so that the positive electrode 1 can meet different application requirements.

[0081] Additionally, the positive electrode active material may also include a third positive electrode active material, for example, lithium iron phosphate. In one example, the first positive electrode active material layer may include both a first positive electrode active material and a third positive electrode active material. In another example, the second positive electrode active material layer may include both a second positive electrode active material and a third positive electrode active material.

[0082] In some embodiments, the first positive electrode active material and the second positive electrode active material satisfy the following condition: 0.2 ≤ K ≤ 0.6;

[0083] in,

[0084] Specifically, the K value can be controlled by adjusting the values ​​of m, n, a1, and a2. Specifically, m and n can be adjusted by controlling the amounts of the first and second positive electrode active materials, thereby controlling the K value. The compounds shown in formula (I) and formula (II) can be prepared using synthetic methods commonly used in the art. a1 and a2 can be adjusted by controlling the amounts of manganese and cobalt sources used in the synthesis process, thereby controlling the K value.

[0085] In the embodiments of this application, by controlling the value of K within a suitable range, the lithium-ion dynamics in the thickness direction of the positive electrode 1 can be flexibly adjusted. This allows the lithium-ion dynamics of the upper layer of the film 12 to match the large current flowing through the surface of the positive electrode 1 during the later stages of charging, and the lithium-ion dynamics of the lower layer of the film 12 to match the current flowing through the interior of the positive electrode 1. This effectively improves the polarization of the positive electrode 1 during charging, thereby reducing the impact of concentration polarization on battery performance. Through flexible adjustment of the K value, the positive electrode 1 can be used in batteries of different models and energy densities.

[0086] In some embodiments, the membrane layer 12 may optionally include an adhesive. As an example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0087] In some embodiments, the film layer 12 may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the positive electrode 1 can be prepared by dispersing the components used to prepare the positive electrode, such as the first positive electrode active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a first positive electrode slurry; dispersing the second positive electrode active material, conductive agent, binder and any other components in a solvent (e.g., N-methylpyrrolidone) to form a second positive electrode slurry; coating the first positive electrode slurry and the second positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode 1 after drying, cold pressing and other processes.

[0089] [Negative electrode plate]

[0090] A negative electrode typically includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer comprising a negative electrode active material. It should be understood that the negative electrode film layer is the film layer disposed on the negative current collector.

[0091] As an example, the negative electrode current collector has two surfaces opposite each other in its own 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.

[0092] Optionally, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0093] Optionally, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0094] Optionally, the negative electrode film layer also includes 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).

[0095] Optionally, in one embodiment, the negative electrode film layer further includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0096] Optionally, the negative electrode film may also include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0097] In some embodiments, the negative electrode sheet can be prepared by forming a negative electrode slurry using the components described above. For example, the negative electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a negative electrode slurry. The negative electrode slurry is then coated onto a negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained.

[0098] [Electrolytes]

[0099] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0100] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0101] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0102] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0103] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0104] In some embodiments, the conductivity σ of the electrolyte satisfies: 3.3 mS cm⁻¹ -1 ≤σ≤13mS cm -1 .

[0105] The conductivity σ of an electrolyte is related to factors such as the electrolyte, solute, solvent, and concentration of the electrolyte. In some examples, the conductivity σ of the electrolyte can be controlled by adjusting the concentration of the electrolyte or changing the type of electrolyte or solvent.

[0106] [Isolation Component]

[0107] In some embodiments, the battery also includes a separator. This application does not impose any particular limitation on the type of separator; for example, any known porous membrane with good chemical and mechanical stability can be selected.

[0108] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0109] Next, the method for preparing the positive electrode 1 according to the embodiments of this application will be described in detail.

[0110] Figure 3 This is a schematic flowchart illustrating a method for preparing a positive electrode sheet 1 according to an embodiment of this application. Figure 3 As shown, method 300 includes:

[0111] S301 provides current collector 11.

[0112] S302, a first positive electrode active material layer 121 is provided on at least one side of the current collector.

[0113] S303, a second positive electrode active material layer 122 is disposed on the first positive electrode active material layer 121.

[0114] The first positive electrode active material layer 121 includes a first positive electrode active material, and the second positive electrode active material layer 122 includes a second positive electrode active material. The first positive electrode active material includes a lithium phosphate with an olivine structure, and the second positive electrode active material includes a cobalt-containing lithium metal oxide.

[0115] In this embodiment, the positive electrode 1 prepared by method 300 has a double-layer structure in its film layer 12, which has the same technical effect as the positive electrode 1, and will not be described in detail here.

[0116] In some implementations, the positive electrode 1, the negative electrode 1, and the separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0117] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0118] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0119] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 This is an example of a square-structured battery cell, 400.

[0120] Figure 5 This is a battery module 500 used as an example. (See reference...) Figure 5 In the battery module 500, multiple battery cells 400 can be arranged sequentially along the length of the battery module 500. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 400 can be secured using fasteners.

[0121] Alternatively, in one embodiment, the battery module 500 may further include a housing with a receiving space in which a plurality of battery cells 400 are received.

[0122] Optionally, in one embodiment, the battery module 500 can also be assembled into a battery. The number of battery modules 500 contained in the battery can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery.

[0123] Figure 6 and Figure 7 This is a battery 600 used as an example. (See reference...) Figure 6 and Figure 7 The battery 600 may include a battery box and multiple battery modules 500 disposed within the battery box. The battery box includes an upper box 601 and a lower box 602, with the upper box 601 covering the lower box 602 to form a closed space for accommodating the battery modules 500. The multiple battery modules 500 can be arranged in any manner within the battery box.

[0124] It should be understood that in some embodiments, the battery 600 described above is also referred to as a battery pack. The individual battery cells 400 can be first assembled into a battery module 500, and the battery 600 is composed of the battery module 500. Alternatively, the battery 600 can be directly assembled from the individual battery cells 400, omitting the intermediate form of the battery module 500.

[0125] In addition, this application also provides an electrical device, which includes at least one of the battery cell 400, battery module 500, or battery 600 provided in this application. The battery cell 400, battery module 500, or battery 600 can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0126] As an electrical device, you can choose a single battery cell (400), a battery module (500), or a battery (600) depending on your usage requirements.

[0127] This is an example of an electrical device. The device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0128] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0129] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0130] [Examples and Comparative Examples]

[0131] Example 1

[0132] (1) Preparation of positive electrode sheet

[0133] The compound shown in formula (I), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:1:2. After thorough stirring and mixing, the first positive electrode slurry was obtained.

[0134] The compound shown in formula (II), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:1:2. After thorough stirring and mixing, the second positive electrode slurry was obtained.

[0135] The first and second positive electrode slurries are uniformly coated onto the positive electrode current collector aluminum foil in one or multiple applications, with the first positive electrode slurry on the bottom layer and the second positive electrode slurry on the top layer. The resulting material is then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0136] In Example 1, m = 0.4, n = 0.6, a1 = 0.6, a2 = 0.24, and K = 0.60.

[0137] (2) Preparation of negative electrode sheet

[0138] The negative electrode active material, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water and mixed evenly to obtain a negative electrode slurry. The negative electrode slurry is then uniformly coated onto the negative electrode current collector copper foil. After cold pressing and slitting, the negative electrode sheet is obtained.

[0139] (3) Assembly of battery cells

[0140] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The stacked components are then wound to form an electrode assembly. The electrode assembly is placed in a housing, dried, and then injected with electrolyte. After formation and settling processes, a battery cell is obtained.

[0141] The electrolyte includes carbonate solvents, and its conductivity σ = 4.4 mS / cm. -1 .

[0142] Example 2

[0143] Compared with Example 1, in Example 2, m = 0.3, n = 0.7, K = 0.93, and the other parameters are the same as in Example 1.

[0144] Example 3

[0145] Compared with Example 2, in Example 3, a1 = 0.7, a2 = 0.15, K = 0.50, and the other parameters are the same as in Example 2.

[0146] Example 4

[0147] Compared with Example 1, in Example 4, the second positive electrode active material layer further includes lithium iron phosphate (LiFePO4), m=0.4, n=0.5, K=0.50, and the other parameters are the same as in Example 1.

[0148] Example 5

[0149] Compared with Example 1, in Example 5, a1 = 0.1, a2 = 0.24, K = 3.6, and the other parameters are the same as in Example 1.

[0150] Example 6

[0151] Compared with Example 1, in Example 6, a1 = 0.9, a2 = 0.24, K = 0.40, and the other parameters are the same as in Example 1.

[0152] Example 7

[0153] Compared with Example 1, in Example 7, a1 = 0.6, a2 = 0.02, K = 0.05, and the remaining parameters are the same as in Example 1.

[0154] Example 8

[0155] Compared with Example 1, in Example 8, a1 = 0.6, a2 = 0.5, K = 1.25, and the other parameters are the same as in Example 1.

[0156] Example 9

[0157] Compared to Example 1, in Example 9, the conductivity of the electrolyte σ = 3.3 mS cm⁻¹ -1 The remaining parameters are the same as in Example 1.

[0158] Example 10

[0159] Compared to Example 1, in Example 10, the conductivity of the electrolyte σ = 13 mS cm -1 The remaining parameters are the same as in Example 1.

[0160] Example 11

[0161] Compared with Example 1, in Example 11, a2 = 0.12, m = 0.5, n = 0.5, K = 0.20, and the other parameters are the same as in Example 1.

[0162] Comparative Example 1

[0163] Compared to Example 1, the positive electrode sheet in Comparative Example 1 has a single-layer structure. Specifically, the compound shown in formula (I), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:1:2, and the mixture was thoroughly stirred and mixed to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the positive electrode current collector aluminum foil. After drying, cold pressing, and slitting, the positive electrode sheet was obtained.

[0164] Comparative Example 2

[0165] Compared to Example 1, in Comparative Example 2, the second positive electrode active material is lithium nickel oxide (LiNiO2), m = 0.4, n = 0.6, a1 = 0.6, K = 0.6, σ = 4.4 mS cm -1 .

[0166] For specific implementation examples and comparative parameter settings, please refer to Table 1.

[0167]

[0168]

[0169] In Table 1, active material 1 represents the first positive electrode active material, active material 2 represents the second positive electrode active material, I represents the compound shown in formula (I), and II represents the compound shown in formula (II).

[0170] The battery performance test results of the above embodiments and comparative examples are detailed in Table 2.

[0171] Table 2. Battery charging time test results for different embodiments and comparative examples.

[0172]

[0173] In Example 1, the film layer 12 has a bilayer structure and different active materials, while in Comparative Example 1, the film layer 12 is only a single layer structure and contains only a single active material. A comparison between Example 1 and Comparative Example 1 shows that Example 1 exhibits a significantly higher capacity retention rate than Comparative Example 1, demonstrating superior cycle performance and capacity performance. This demonstrates that by placing a lithium phosphate with an olivine structure on the upper layer of the positive electrode film layer 12 and a cobalt-containing lithium metal oxide on the lower layer of the positive electrode film layer 12, the lithium-ion conductivity of the upper layer of the positive electrode film layer is superior to that of the lower layer, effectively improving battery polarization and helping to enhance the battery's capacity and cycle performance.

[0174] A comparison of Example 1 and Comparative Example 2 shows that lithium nickelate is disposed on the upper layer of film 12. While lithium nickelate also has a layered structure, its lithium-ion kinetics are inferior to those of cobalt-containing lithium metal oxide. The capacity retention rate of the battery in Comparative Example 2 after 200 cycles is also significantly lower than that of the battery in Example 1. Therefore, by disposing of cobalt-containing lithium metal oxide with excellent lithium-ion kinetics on the upper layer, the lithium-ion transport capacity on the surface of the positive electrode 1 can be matched with the larger current on the surface of the positive electrode 1, thereby effectively improving battery polarization and helping to improve the battery's capacity and cycle performance.

[0175] Compared to Example 1, Examples 2 and 3 adjusted the values ​​of m and n, and the values ​​of a1 and a2, respectively. Therefore, the K values ​​for Examples 2 and 3 were 0.93 and 0.5, respectively. The K value of 0.93 in Example 2 exceeded the range of 0.2-0.6, while the K value of 0.5 in Example 3 fell within this range. The capacity retention rates of the batteries in Examples 2 and 3 were 91.0% and 92.2%, respectively, indicating that the performance of Examples 1 and 3 was superior to that of Example 2. This demonstrates that controlling the K value within a suitable range is more beneficial for improving battery polarization and enhancing battery cycle performance and capacity performance.

[0176] Compared to Example 1, the second positive electrode active material layer 122 in Example 4 also includes lithium iron phosphate, wherein the mass ratio of lithium iron phosphate to the positive electrode active material is 0.1. The film layer 12 of the positive electrode sheet 1 in Example 4 also has the same bilayer structure and corresponding materials as in Example 1, and also exhibits excellent cycle performance and capacity performance.

[0177] Compared to Example 1, Examples 5-6 and 7-8 changed the values ​​of a1 and a2, respectively. In Examples 5 and 6, the values ​​of a1 were 0.1 and 0.9, respectively, with corresponding K values ​​of 3.6 and 0.4, and capacity retention rates of 90.1% and 92.9%, respectively. As a1 increased, the K value decreased. Notably, the K value in Example 5 exceeded the range of 0.2-0.6, indicating that the capacity retention performance of the battery in Example 5 was inferior to that in Examples 1 and 6. In Examples 7 and 8, the values ​​of a2 were 0.02 and 5, respectively, with corresponding K values ​​of 0.05 and 1.25, and capacity retention rates of 80.7% and 90.3%, respectively. As a2 increased, the K value increased. In both Examples 7 and 8, the K values ​​exceeded the range of 0.2-0.6. The capacity retention rates of the batteries in Examples 7 and 8 were lower than those in Example 1, where the K value fell within the range of 0.2-0.6. However, the capacity retention rate of Example 8 was better than that of Example 7, indicating that increasing the cobalt content in the positive electrode also helps to improve the capacity retention rate of the battery.

[0178] Compared to Example 1, Examples 9-10 changed the conductivity of the electrolyte. In Examples 9 and 10, the conductivity σ was 3.3 mS / cm. -1 and 13mS cm -1 All fell into 3.3mS cm -1 -13mS cm -1 Within the range of values, the corresponding capacity retention rates are 93.5% and 94.0%, respectively, both demonstrating good cycle performance and capacity performance.

[0179] Compared with Example 1, Example 11 changed a2, m, and n, so that the value of K is 0.2, which also falls within the range of 0.2-0.6. Example 11 also showed good cycle performance and capacity performance.

[0180] Next, the testing methods for the physical parameters and performance parameters mentioned in the embodiments of this application will be briefly introduced.

[0181] 1. Test method for battery capacity retention

[0182] At 25℃, the battery underwent charge-discharge testing. The specific test conditions were as follows: using a Blue Electric testing system, the positive and negative terminals were connected, and the battery was subjected to two stages of charge-discharge testing. The first stage involved: resting for 1 minute, then constant current charging at 8mA to 4.2V, followed by constant voltage charging at 4.2V with a cutoff current of 2mA. After resting for 10 minutes, constant current discharging at 8mA with a cutoff voltage of 2.5V was performed, followed by a 50-hour rest period. This first stage test was used for battery formation to establish the SEI film and reduce battery polarization. The second stage involved: constant current charging at 60mA with a cutoff voltage of 4.2V; constant voltage charging at 4.2V with a cutoff current of 2mA; resting for 10 minutes, followed by constant current discharging at 60mA with a cutoff voltage of 2.5V. This second stage charge-discharge cycle was repeated 500 times before charging to 4.2V and stopping the test. This second stage test was used to assess the battery's cycle performance. The first charge cycle refers to the battery being charged at a constant current of 60mA to 4.2V after the first test, and then charged at a constant voltage of 4.2V to a cutoff current of 2mA. The first discharge capacity refers to the capacity discharged by the battery when discharged at a constant current of 60mA to 2.5V. Furthermore, using the first discharge capacity as a baseline of 100%, the discharge capacity after 200 cycles is calculated, and the ratio of this capacity to the first discharge capacity is the capacity retention rate after 200 cycles.

[0183] 2. Test methods for electrolyte conductivity

[0184] Electrolyte conductivity can be tested using a conductivity meter (such as a Mettler Toledo conductivity meter) at room temperature (25°C) and the data can be read.

[0185] 3. Methods for testing the K value

[0186] Inductively coupled plasma (ICP) testing of the electrode can detect the content of specified elements in the upper and lower layers of the film in the electrode, detect a1*m and a2*n, and then calculate the K value through the formula.

[0187] ICP testing method: The electrode or the electrode after stripping the current collector is digested with aqua regia (concentrated hydrochloric acid: concentrated nitric acid = 3:1) or reverse aqua regia (concentrated nitric acid: concentrated hydrochloric acid 3:1), and then the elemental content is measured by an ICP analyzer.

[0188] 4. Scanning electron microscopy testing methods for electrodes

[0189] Weigh out an electrode sheet of a certain area (≤6×6cm) 2 The conductive adhesive is adhered to the conductive adhesive, placed on the sample stage and dried. The treated sample stage is then sent into a field emission scanning electron microscope (e.g., a Zeiss Sigma 300 scanning electron microscope) to image the morphology of the material.

[0190] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode plate, characterized in that, The positive electrode sheet includes: Current collector, first positive electrode active material layer and second positive electrode active material layer; The first positive electrode active material layer is disposed on at least one side of the current collector, and the second positive electrode active material layer is disposed on the first positive electrode active material layer; The first positive electrode active material layer includes a first positive electrode active material, and the second positive electrode active material layer includes a second positive electrode active material. The first positive electrode active material includes a lithium phosphate with an olivine structure, and the second positive electrode active material includes a cobalt-containing lithium metal oxide. The lithium phosphates with the olivine structure include compounds represented by formula (I): Li (1+x1) Mr a1 M1 (1-a1) Q (1-m) O (4-n) (I) Where M1 represents a metallic element, -0.2≤x1≤0.2, 0.1≤a1≤0.9, 0≤m≤0.1, 0≤n≤0.1; The cobalt-containing lithium metal oxide includes compounds represented by formula (II): Li (1+x2) Co a2 M2 (1-a2) O (2-y) A y (II) Where M2 represents a metallic element, A represents a dopant element at the oxygen site, and A includes one or more of S, F, Cl and Br, -0.2≤x2≤0.2, 0.02≤a2≤0.5, 0≤y<2; The positive electrode active material includes the first positive electrode active material and the second positive electrode active material; The mass ratio of the first positive electrode active material to the positive electrode active material is m, and the mass ratio of the second positive electrode active material to the positive electrode active material is n, where 0 < m < 1, 0 < n < 1, and 0 < m + n ≤ 1; The positive electrode plate satisfies: 0.2≤K≤0.6; in, .

2. The positive electrode sheet according to claim 1, characterized in that, The M1 includes one or more of Fe, Al, Cu, Cr, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb, and Ge.

3. The positive electrode sheet according to claim 1, characterized in that, The cobalt-containing lithium metal oxide includes layered cobalt-containing lithium metal oxide.

4. The positive electrode sheet according to claim 1, characterized in that, The M2 includes one or more of Ni, Fe, Cr, Mn, Ti, Zn, V, Al, and Zr.

5. The positive electrode sheet according to any one of claims 1-4, characterized in that, In a single battery cell including the positive electrode, the conductivity σ of the electrolyte satisfies: 3.3 mS / cm ≤ σ ≤ 13 mS / cm.

6. A method for preparing a positive electrode sheet, characterized in that, The method includes: Provide current collectors; A first positive electrode active material layer is disposed on at least one side of the current collector; A second positive electrode active material layer is disposed on the first positive electrode active material layer; Wherein, the first positive electrode active material layer includes a first positive electrode active material, the second positive electrode active material layer includes a second positive electrode active material, the first positive electrode active material includes a lithium phosphate with an olivine structure, and the second positive electrode active material includes a lithium metal oxide containing cobalt. The lithium phosphates with the olivine structure include compounds represented by formula (I): Li (1+x1) Mr a1 M1 (1-a1) Q (1-m) O (4-n) (I) Where M1 represents a metallic element, -0.2≤x1≤0.2, 0.1≤a1≤0.9, 0≤m≤0.1, 0≤n≤0.1; The cobalt-containing lithium metal oxide includes compounds represented by formula (II): Li (1+x2) Co a2 M2 (1-a2) O (2-y) A y (II) Where M2 represents a metallic element, A represents a dopant element at the oxygen site, and A includes one or more of S, F, Cl and Br, -0.2≤x2≤0.2, 0.02≤a2≤0.5, 0≤y<2; The positive electrode active material includes the first positive electrode active material and the second positive electrode active material; The mass ratio of the first positive electrode active material to the positive electrode active material is m, and the mass ratio of the second positive electrode active material to the positive electrode active material is n, where 0 < m < 1, 0 < n < 1, and 0 < m + n ≤ 1; The positive electrode plate satisfies: 0.2≤K≤0.6; in, .

7. A single battery cell, characterized in that, The battery cell includes a positive electrode sheet as described in any one of claims 1-5, or a positive electrode sheet prepared by the preparation method according to claim 6.

8. The battery cell according to claim 7, characterized in that, The battery cell includes an electrolyte, and the conductivity σ of the electrolyte satisfies: 3.3 mS / cm ≤ σ ≤ 13 mS / cm.

9. A battery, characterized in that, The battery includes the battery cell as described in claim 7 or 8.

10. An electrical device, characterized in that, The electrical device includes a battery cell as described in claim 7 or 8, and / or a battery as described in claim 9.

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