Positive plate, battery and electric equipment

Abstract

The invention relates to the technical field of batteries, in particular to a positive plate, a battery and electric equipment. The positive plate comprises a current collector and an active material layer, and the active material layer comprises a first active layer and a second active layer; the first active layer comprises a first lithium manganese iron phosphate material and a first ternary material, and the second active layer comprises a second lithium manganese iron phosphate material and a second ternary material; the surface density of the first active layer is a1, the mass ratio of the first ternary material in the first active layer is b1, the surface density of the second active layer is a2, the mass ratio of the second ternary material in the second active layer is b2, and the following relational expressions are met: 0.05 < = b1 < = 0.95, 0.05 < = b2 < = 0.95; 0.1 < = a2 / a1 < = 10, and b1lt; b2. According to the positive plate provided by the embodiment of the invention, the proportion and the surface density of the materials in the active material layer are differentially distributed, so that the ion and electron transmission characteristics of the positive plate are effectively improved, and the dynamic performance of the battery is improved.

Description

Technical Field

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

[0002] Lithium iron phosphate and ternary materials are two commonly used materials in batteries. Lithium iron manganese phosphate has begun to be used in positive electrodes because it has similar safety performance to lithium iron phosphate.

[0003] For example, existing technologies attempt to improve performance by blending lithium iron manganese phosphate (LFMPO) with ternary materials. However, due to the significant differences in the electronic and ionic conductivities of the two materials, this mixed preparation struggles to achieve the desired results. Another approach employs a double-layer cathode structure, attempting to layer the LFMPO and ternary materials. However, the high impedance of the LFMPO layer persists, leading to an increase in overall impedance and thus limiting improvements in energy density. Summary of the Invention

[0004] The present application provides a positive electrode sheet, a method for preparing the electrode sheet, a battery and an electrical device. By controlling the ratio of lithium manganese iron phosphate material and ternary material, the internal resistance of the battery can be further reduced while ensuring the energy density of the material.

[0005] A first aspect of the present application provides a positive electrode sheet, comprising:

[0006] a current collector; and

[0007] The active material layer includes a first active layer and a second active layer, wherein the first active layer is provided on at least one side of the current collector, and the second active layer is provided on a side of the first active layer away from the current collector; the first active layer includes a first lithium iron manganese phosphate material and a first ternary material, and the second active layer includes a second lithium iron manganese phosphate material and a second ternary material; the surface density of the first active layer is a1, and the mass proportion of the first ternary material in the first active layer is b1; the surface density of the second active layer is a2, and the mass proportion of the second ternary material in the second active layer is b2, and the units of a1 and a2 are g / m 2 , and satisfy the following relationship:

[0008] 0.05≤b1<0.95,0.05 <b2≤0.95;

[0009] 0.1≤a2 / a1≤10, and b1<b2.

[0010] In a possible implementation, the areal density of the first active layer is a1, the mass percentage of the first ternary material in the first active layer is b1, the areal density of the second active layer is a2, and the mass percentage of the second ternary material in the second active layer is b2, and the following relational expressions are satisfied:

[0011] When 0.1 ≤ a2 / a1 ≤ 0.5, 10 ≤ b2 / b1 ≤ 18;

[0012] When 0.5 < a2 / a1 ≤ 10, 1.5 ≤ b2 / b1 ≤ 10.

[0013] In a possible implementation, a1 and a2, and b1 and b2 satisfy the following relational expressions:

[0014] When 0.15 ≤ a2 / a1 ≤ 0.5, 10 ≤ b2 / b1 ≤ 15;

[0015] When 0.5 < a2 / a1 ≤ 8, 2 ≤ b2 / b1 ≤ 10.

[0016] In a possible implementation, the first lithium iron manganese phosphate material is LiMn x Fe 1-x PO4, where 0.55 ≤ x ≤ 0.85, and / or the second lithium iron manganese phosphate material is LiMn y Fe 1-y PO4, where 0.55 ≤ y ≤ 0.85;

[0017] The first lithium iron manganese phosphate material is LiMn x Fe 1-x PO4, where 0.6 ≤ x ≤ 0.8, and / or the second lithium iron manganese phosphate material is LiMn y Fe 1-y PO4, where 0.6 ≤ y ≤ 0.8.

[0018] In a possible implementation, x and y satisfy the following relational expression: x ≥ y.

[0019] In a possible implementation, the D50 particle size of the first lithium iron manganese phosphate material is 10 - 400 nm, and / or the D50 particle size of the second lithium iron manganese phosphate material is 10 - 400 nm;

[0020] Preferably, the D50 particle size of the first lithium iron manganese phosphate material is 20 - 350 nm, and / or the D50 particle size of the second lithium iron manganese phosphate material is 20 - 350 nm.

[0021] In a possible implementation, the D50 particle size of the first lithium iron manganese phosphate material is greater than the D50 particle size of the second lithium iron manganese phosphate material.

[0022] In one possible implementation, the first ternary material is LiNi m Co n Mn 1-m-n O2, wherein 0.5≤m≤0.8, 0.05≤n≤0.3, and / or the second ternary material is LiNi j Co k Mn 1-j-k O2, where 0.5≤j≤0.8, 0.05≤k≤0.3;

[0023] Preferably, the first ternary material is LiNi m Co n Mn 1-m-n O2, wherein 0.55≤m≤0.75, 0.08≤n≤0.25; and / or the second ternary material is LiNi j Co k Mn 1-j-k O2, where 0.55≤j≤0.75, 0.08≤k≤0.25.

[0024] In one possible implementation, the D50 particle size of the first ternary material is 1-15 μm, and / or the D50 particle size of the second ternary material is 1-15 μm.

[0025] In one possible implementation, the surface density of the first active layer is a1, the surface density of the second active layer is a2, and the following relationship is satisfied:

[0026] 25g / m 2 ≤a1≤325g / m 2 , 25g / m 2 ≤a2≤325g / m 2 ;

[0027] Preferably, 75g / m 2 ≤a1≤300g / m 2 , 75g / m 2 ≤a2≤300g / m 2 .

[0028] A second aspect of the present application provides a battery comprising any one of the above-mentioned positive electrode sheets.

[0029] A third aspect of the present application provides an electrical device comprising any one of the batteries described above.

[0030] The embodiments of the present application have the following beneficial effects:

[0031] In the positive electrode sheet of this embodiment, by establishing a parameter relationship between the surface density and the active material layer, a first active layer and a second active layer with different material mass proportions are formed. In the direction from the current collector to the electrolyte, the proportion and surface density of the materials in the active material layer of the positive electrode sheet are differentially distributed. While ensuring the energy density of the positive electrode sheet, the internal resistance of the battery is further reduced, thereby effectively improving the ion and electron transport characteristics of the positive electrode sheet and enhancing the battery kinetic performance.

[0032] Specifically, in the positive electrode sheet of this embodiment, by setting the mass proportion of the second ternary material in the second active layer to be higher than the mass proportion of the first ternary material in the first active layer, it helps to support higher ion and electron transmission speeds. Since the first active layer is close to the current collector, by improving the conductivity and ion migration ability of the first active layer, the response speed of the battery during the charge and discharge process can be effectively improved; at the same time, since the mass proportion of the second ternary material in the second active layer is higher than the mass proportion of the first ternary material in the first active layer, the overall energy storage capacity of the battery can be further improved. Through this hierarchical design, the first active layer and the second active layer have different functional tendencies, ensuring that the entire positive electrode sheet can achieve optimal energy conversion and output when used in the battery, thereby improving the overall performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0034] Figure 1 A schematic structural diagram of a positive electrode sheet in an embodiment of the present invention is shown;

[0035] Reference numerals:

[0036] 100-positive electrode;

[0037] 110-current collector;

[0038] 120 - active material layer; 121 - first active layer; 122 - second active layer. DETAILED DESCRIPTION

[0039] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0040] Currently, lithium iron phosphate and ternary materials are the most common in battery applications. While lithium iron phosphate offers cost and safety advantages, its energy density is limited. While ternary materials offer high energy density, they present safety risks. Therefore, optimizing positive electrode materials has become a key focus for improving lithium-ion battery performance. Because lithium iron manganese phosphate (LiMnFePO4) has similar safety performance to LiFePO4 and offers an energy density advantage due to its higher plateau voltage, attempts have been made to incorporate LiMnFePO4 into positive electrodes. However, LiMnFePO4's inherent low electrical conductivity presents technical challenges for practical application.

[0041] For example, related technologies have attempted to improve performance directly by blending lithium iron manganese phosphate and ternary materials. However, due to the large differences in the electronic and ionic conductivity of the two materials, it is difficult to achieve the desired effect simply by directly mixing them. In another technical approach, a double-layer structured positive electrode sheet is used, attempting to achieve a synergistic effect between the materials through a layered design of lithium iron manganese phosphate and ternary materials. However, since each layer contains only a single active substance, the high impedance problem of the lithium iron manganese phosphate layer still exists, leading to an increase in the overall impedance, which in turn restricts the improvement of energy density. Therefore, how to use lithium iron manganese phosphate materials in positive electrode sheets to improve battery performance is an important issue that the industry urgently needs to solve.

[0042] For the above technical issues, see Figure 1As shown, an embodiment of the present invention provides a positive electrode sheet 100, a method for preparing the electrode sheet, and a battery. The battery includes the positive electrode sheet 100, and the electrode sheet preparation method is used to prepare the positive electrode sheet 100. Specifically, the positive electrode sheet 100 includes a current collector 110 and an active material layer 120, wherein the current collector 110 is specifically a positive electrode current collector, and the active material layer 120 is specifically a positive electrode active material layer. The active material layer 120 includes a first active layer 121 and a second active layer 122, the first active layer 121 is provided on at least one side of the current collector 110, and the second active layer 122 is provided on a side of the first active layer 121 away from the current collector 110. The first active layer 121 includes a first lithium iron manganese phosphate material and a first ternary material, and the second active layer 122 includes a second lithium iron manganese phosphate material and a second ternary material. The surface density of the first active layer 121 is a1, the mass ratio of the first ternary material in the first active layer 121 is b1, the surface density of the second active layer 122 is a2, the mass ratio of the second ternary material in the second active layer 122 is b2, and the following relationship is satisfied:

[0043] 0.05≤b1<0.95,0.05 <b2≤0.95;

[0044] 0.1≤a2 / a1≤10, and b1 <b2。

[0045] In the positive electrode sheet 100 of this embodiment, by establishing a parameter relationship between the surface density and the active material layer 120, a first active layer 121 and a second active layer 122 having different material mass proportions are formed. In the direction from the current collector 110 to the electrolyte, the proportion and surface density of the materials in the active material layer 120 of the positive electrode sheet 100 are differentially distributed. While ensuring the energy density of the positive electrode sheet 100, the internal resistance of the battery is further reduced, thereby effectively improving the ion and electron transport characteristics of the positive electrode sheet 100 and enhancing the battery kinetic performance.

[0046] Specifically, in the positive electrode sheet 100 of this embodiment, by setting the mass proportion of the second ternary material in the second active layer 122 to be higher than the mass proportion of the first ternary material in the first active layer 121, it helps to support higher ion and electron transmission speeds. Since the first active layer 121 is close to the current collector 110, by improving the conductivity and ion migration ability of the first active layer 121, the response speed of the battery during the charge and discharge process can be effectively improved; at the same time, since the mass proportion of the second ternary material in the second active layer 122 is higher than the mass proportion of the first ternary material in the first active layer 121, the overall energy storage capacity of the battery can be further improved. Through this hierarchical design, the first active layer 121 and the second active layer 122 have different functional tendencies, ensuring that the entire positive electrode sheet 100 can achieve optimal energy conversion and output when used in the battery, thereby improving the overall performance of the battery.

[0047] It should be noted that Figure 1 In the illustrated embodiment, only the technical solution of disposing the active material layer 120 on one side of the current collector 110 is shown. Of course, in actual applications, active material layers 120 can be provided on both surfaces of the current collector 110 respectively, and the specific position of the active material layer 120 is not uniquely limited herein. Specifically, a conductive binder layer can also be provided between the active layer 120 and the current collector 110. This conductive binder layer can effectively improve the electronic contact between the active material layer 120 and the current collector 110, reduce the contact resistance, and thus further improve the charge-discharge efficiency of the battery. Commonly used conductive binder materials include, but are not limited to, polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), etc., and appropriate materials and ratios can be selected and configured according to actual requirements. In addition, in order to optimize the performance of the conductive binder layer, conductive additives can also be added, such as carbon nanotubes, graphene, etc., to enhance its conductivity. Taking Figure 1 the illustrated example as an example, when the positive electrode sheet 100 is in actual use, usually the electrolyte is located on the side of the active material layer 120 away from the current collector 110. Therefore, the second active layer 122 is closer to the electrolyte (away from the current collector 110) compared with the first active layer 121, and the first active layer 121 is closer to the current collector 110 (away from the electrolyte) compared with the second active layer 122. In specific applications, the power and capacity performance of the battery can be further optimized according to the relative amounts of the mass ratio b1 of the first ternary material in the first active layer 121 and the mass ratio b2 of the second ternary material in the second active layer 122.

[0048] It can be understood that the areal density mentioned in the embodiments of the present application specifically refers to the mass of the material or the content of the active material per unit area. It is an important parameter because it directly affects the performance of the battery, including the energy density and the power density. Specifically, the change in the areal density can affect the reaction rate and ion conductivity of the electrode. For example, in the positive electrode sheet, by adjusting the areal density, the distribution of the active material of the electrode can be optimized, thereby improving the ion and electron transport efficiency during the charge-discharge process of the battery. This adjustment can fundamentally improve the kinetic performance and overall performance of the battery.

[0049] Specifically, the areal density of the first active layer 121 is a1, the mass ratio of the first ternary material in the first active layer 121 is b1, the areal density of the second active layer 122 is a2, and the mass ratio of the second ternary material in the second active layer 122 is b2, and the following relational expressions are satisfied:

[0050] When 0.1 ≤ a2 / a1 ≤ 0.5, 10 ≤ b2 / b1 ≤ 18;

[0051] When 0.5 < a2 / a1 ≤ 10, 1.5 ≤ b2 / b1 ≤ 10.

[0052] In this embodiment, when 0.1 ≤ a2 / a1 ≤ 0.5, the current density inside the battery can be effectively controlled, its energy density and power density can be improved, and thus the discharge performance of the battery can be enhanced. At the same time, when b2 / b1 is in the range of 10 to 18, the mass proportion of the ternary material increases, which can optimize the chemical performance of the battery, thereby improving the cycle stability and extending the service life of the battery.

[0053] In addition, in the above embodiment, a2 / a1 can be 0.1, 0.2, 0.3, 0.4, 0.5 or any value between 0.1 and 0.5, and at the same time b2 / b1 can be 10, 12, 14, 16, 18 or any value between 10 and 18; in addition, in different positive electrode plates 100, a2 / a1 and b2 / b1 can also adopt materials with different values, which are not uniquely limited herein.

[0054] In another case, when 0.5 < a2 / a1 ≤ 10, the areal density of the second active layer 122 continues to increase, and in this stage, by controlling the ratio of b2 / b1 between 1.5 and 10, good electrical conductivity and ionic conductivity can be achieved, providing guarantee for the stable operation of the battery under high load conditions.

[0055] In the above embodiment, a2 / a1 can be 0.6, 2.0, 4.0, 6.0, 8.0, 10.0 or any value between 0.5 and 10, and at the same time b2 / b1 can be 1.5, 2, 4, 6, 10 or any value between 1.5 and 10; in addition, in different positive electrode plates 100, a2 / a1 and b2 / b1 can also adopt materials with different values, which are not uniquely limited herein.

[0056] When the mass proportion of the ternary material in the first active layer 121 is b1 and the mass proportion of the ternary material in the second active layer 122 is b2 are different, the power and capacity performance of the battery can be further optimized according to the relative amount of the mass proportion of the ternary material in the first active layer 121 being b1 and the mass proportion of the ternary material in the second active layer 122 being b2.

[0057] Furthermore, a1 and a2 as well as b1 and b2 satisfy the following relational expressions:

[0058] 0.15 ≤ a2 / a1 ≤ 0.5, 10 ≤ b2 / b1 ≤ 15;

[0059] Or 0.5 < a2 / a1 ≤ 8, 2 ≤ b2 / b1 ≤ 10.

[0060] In this embodiment, by controlling a1 and a2 as well as b1 and b2 within the above ranges, the ion and electron transport characteristics of the positive electrode sheet 100 can be further improved, and the energy density and power performance of the battery can be optimized at the same time.

[0061] In one embodiment, the first lithium manganese iron phosphate material is LiMn x Fe 1-x PO4, wherein 0.55≤x≤0.85, and / or the second lithium manganese iron phosphate material is LiMn y Fe 1-y PO4, where 0.55≤y≤0.85.

[0062] In this embodiment, by partially replacing the iron ions (Fe) in the first lithium iron phosphate with manganese ions (Mn), the material properties of the positive electrode sheet 100 can be improved. Specifically, when 0.55≤x≤0.85, the ratio of Mn to Fe can be adjusted within a preset range. The lithium manganese iron phosphate material thus formed can optimize the electrochemical properties of the material compared to traditional lithium iron phosphate materials, thereby improving energy density, battery cycle life, etc. At the same time, the lithium manganese iron phosphate material has better safety and stability, which facilitates the application of the positive electrode sheet 100 in this embodiment in energy storage and power batteries with higher design requirements. By adjusting the ratio of manganese to iron within the above range, manganese and iron can be appropriately combined to improve the electrochemical performance of the active material layer 120.

[0063] Similarly, specifically when 0.55≤y≤0.85, by adjusting the ratio of manganese to iron to be within the above range, manganese and iron can be properly combined to improve the electrochemical performance of the active material layer 120 .

[0064] It should be noted that the values of x and y can be the same or different. The optimal Mn / Fe ratio of the first and second lithium manganese iron phosphate materials can be selected based on the specific requirements of the battery to achieve optimal performance under different discharge rates and cycling conditions. Preferably, when x ≥ y, that is, the Mn content of the first lithium manganese iron phosphate material is greater than or equal to the Mn content of the second lithium manganese iron phosphate material, the material conductivity is higher, and the battery power performance is further improved. When the Mn content of the second lithium manganese iron phosphate material is higher than the Mn content of the first lithium manganese iron phosphate material, the battery capacity performance is further improved.

[0065] Preferably, when x and y satisfy 0.6≤x≤0.8 and 0.6≤y≤0.8, the energy density and power performance of the battery can be better balanced.

[0066] Furthermore, in the above embodiment, x in the lithium iron manganese phosphate material can be 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, or any value between 0.55 and 0.85; furthermore, different lithium iron manganese phosphate material particles in the lithium iron manganese phosphate material can also use materials with different x values, and this is not a sole limitation here. Similarly, y in the second lithium iron manganese phosphate material can be 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, or any value between 0.55 and 0.85; furthermore, different lithium iron manganese phosphate material particles in the lithium iron manganese phosphate material can also use materials with different y values, and this is not a sole limitation here.

[0067] In one embodiment, the D50 particle size of the first lithium iron manganese phosphate material is 10-400 nm, and / or the D50 particle size of the second lithium iron manganese phosphate material is 10-400 nm.

[0068] Setting the D50 particle size of the lithium iron phosphate material within the nanometer size range can help improve the electrochemical performance of the lithium iron phosphate material. Specifically, a smaller particle size can provide a larger specific surface area, thereby increasing the reactivity of the active material layer 120 and the lithium ion migration rate, thereby improving the battery's charge and discharge rate performance and cycle life. In addition, nanoscale particles help shorten the diffusion path of lithium ions within the positive electrode material, thereby reducing the probability of polarization and improving high-rate performance. By precisely controlling the particle size of the lithium iron phosphate material, the conductivity and stability of the positive electrode material are improved while reducing internal resistance and lowering the heat generated during battery operation. At the same time, during the preparation process of the lithium iron phosphate material, by regulating the D50 particle size of the lithium iron phosphate material, the lithium iron phosphate material can maintain structural stability under different temperatures and pressures, effectively preventing the agglomeration and excessive growth of the lithium iron phosphate material particles, which helps ensure that the lithium iron phosphate material maintains good structural integrity during repeated charge and discharge cycles.

[0069] Furthermore, in the above embodiment, the D50 particle size of the first lithium iron manganese phosphate material can be 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, or any two or more thereof. Furthermore, different lithium iron manganese phosphate particles within the lithium iron manganese phosphate material can also be made of materials with different D50 particle sizes, without being a limitation herein. Similarly, the D50 particle size of the second lithium iron manganese phosphate material can be 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, or any two or more thereof.

[0070] It should be noted that the D50 particle size of the first lithium iron manganese phosphate material and the second lithium iron manganese phosphate material can be the same or different to meet the needs of a specific battery design. In addition, different lithium iron manganese phosphate material particles in the lithium iron manganese phosphate material can also use materials with different D50 particle sizes, which is not the only limitation here. Preferably, when the D50 particle size of the first lithium iron manganese phosphate material is larger than the D50 particle size of the second lithium iron manganese phosphate material, the short-term power performance of the battery can be further improved, and when the D50 particle size of the first lithium iron manganese phosphate material is smaller than the D50 particle size of the second lithium iron manganese phosphate material, the battery capacity performance is better. Preferably, when the particle size of the lithium iron manganese phosphate material is 20-350nm, the power and cycle performance of the battery can be better balanced.

[0071] In addition, the D50 particle size mentioned in this application refers to the particle size value at which 50% of the particles in the particle distribution have a diameter less than or equal to the particle size value. Image analysis can be used to analyze the particle image using image processing technology to measure the size of the statistical particles. The specific detection process is as follows: First, the positive electrode sheet 100 is cross-sectioned using ion milling (CP), and then the cross-section is characterized by scanning electron microscopy (SEM); at least five different areas are selected and SEM photos of different magnifications are taken (for example: 100000, 50000, 20000, 10000, 5000, 2000, 1000, etc., including but not limited to the above magnifications), and the obtained images are processed with brightness contrast and other methods to make the particle boundaries clearer. The particle size is statistically analyzed manually or with image analysis software. After the output results are processed, detailed results of the particle size distribution can be obtained to obtain indicators such as D50.

[0072] In one embodiment, the first ternary material is LiNi m Co n Mn 1-m-n O2, wherein 0.5≤m≤0.8, 0.05≤n≤0.3, and / or the second ternary material is LiNi j Co k Mn 1-j-k O2, where 0.5≤j≤0.8, 0.05≤k≤0.3.

[0073] Specifically in this embodiment, the energy density of the positive electrode material can be significantly improved by adopting a ternary material with a medium to high nickel (Ni) content (0.5≤m≤0.8, 0.5≤j≤0.8). By increasing the cobalt (Co) content, it can help to improve the stability and conductivity of the positive electrode material, but in practical applications, due to the high cost of cobalt, the cobalt content can be set within the rated range to optimize the manufacturing cost while ensuring battery performance. By increasing the manganese (Mn) content, the thermal stability and safety of the positive electrode material can be improved, and by adding an appropriate amount of manganese to the ternary material, the overall performance of the ternary material can be balanced to improve the stability of the positive electrode material during the charge and discharge process. In this embodiment, technicians can meet the performance design requirements of different batteries by adjusting the values of m and n.

[0074] In addition, in the above embodiment, m in the first ternary material can be 0.5, 0.6, 0.7, 0.8 or any value between 0.5 and 0.8, and n in the first ternary material can be 0.05, 0.10, 0.15, 0.20, 0.25, 0.3 or any value between 0.05 and 0.3; in addition, different ternary material particles in the ternary material can also use materials with different m and n values, which is not limited here.

[0075] Similarly, j in the second ternary material can be 0.5, 0.6, 0.7, 0.8 or any value between 0.5 and 0.8, and k in the second ternary material can be 0.05, 0.10, 0.15, 0.20, 0.25, 0.3 or any value between 0.05 and 0.3; in addition, different ternary material particles in the ternary material can also use materials with different j and k values, which is not limited here.

[0076] It should be noted that m and j can be the same or different to meet the needs of a specific battery design; n and k can be the same or different to meet the needs of a specific battery design. When the Co content in the first ternary material is higher than the Co content in the second ternary material, the battery capacity performance is better; when the Co content in the first ternary material is lower than the Co content in the second ternary material, the material conductivity is high and the battery power performance is better; when the Ni content in the first ternary material is higher than the Ni content in the second ternary material, the battery capacity performance is better; when the Ni content in the first ternary material is lower than the Ni content in the second ternary material, the stability of the material close to the current collector 110 is better and the battery cycle performance is better. Preferably, when 0.55≤m≤0.75, 0.08≤n≤0.25, 0.55≤j≤0.75, and 0.08≤k≤0.25, the battery capacity performance and cycle performance can be better balanced.

[0077] In one embodiment, the D50 particle size of the first ternary material is 0.5-20 μm, and / or the D50 particle size of the second ternary material is 0.5-20 μm.

[0078] In this embodiment, when the D50 particle size of the ternary material is larger (close to 20 μm), the volume energy density and cycle stability of the positive electrode material can be improved, and when the D50 particle size of the ternary material is smaller (close to 0.5 μm), the rate performance and initial capacity of the positive electrode material can be enhanced. In addition, in the preparation process of the ternary material, larger particles help to improve the electrode compaction density, thereby increasing the energy density of the battery, and smaller particles are easier to form a uniform electrode coating. Specifically in this embodiment, by adjusting the D50 particle size of the ternary material, an optimized balance can be found between performance such as energy density, power density and cycle life.

[0079] In addition, in the above embodiment, the D50 particle size of the first ternary material can be 0.5μm, 5μm, 8μm, 10μm, 15μm, 20μm or any at least two of the particle sizes therein. Similarly, the D50 particle size of the second ternary material can be 0.5μm, 5μm, 8μm, 10μm, 15μm, 20μm or any at least two of the particle sizes therein. Specifically, the D50 particle size of the first ternary material and the D50 particle size of the second ternary material can be the same or different to meet the requirements of a specific battery design. In addition, different ternary material particles in the ternary material can also be made of materials with different D50 particle sizes, which is not the only limitation here.

[0080] Specifically, when the D50 particle size of the first ternary material is greater than or equal to the D50 particle size of the second ternary material, the short-term power performance of the battery can be further improved, and the battery power performance is better. When the D50 particle size of the first ternary material is greater than or equal to the D50 particle size of the second ternary material, the battery capacity performance is better. Preferably, when the D50 particle size of the ternary material is 1-15 μm, the power and cycle performance of the battery can be better balanced.

[0081] In this embodiment, the surface density of the first active layer 121 in the positive electrode sheet 100 is a1, where the mass fraction of the first ternary material in the first active layer 121 is b1. The surface density of the second active layer 122 is a2, where the mass fraction of the second ternary material in the second active layer 122 is b2. The surface density of the active material layer 120 is a, and the mass fraction of the ternary material in the active material layer 120 is b. By definition, the above parameters satisfy: a = a1 + a2, b = (a1 × b1 + a2 × b2) / a.

[0082] In order to improve the electrochemical performance of the positive electrode sheet 100, in this embodiment, the above parameters satisfy the following relationship:

[0083] 50g / m 2 ≤a≤350g / m 2 , 0.1≤b≤0.9.

[0084] In this embodiment, when the active material layer 120 has a lower surface density (eg, 50 g / m 2 ), it can provide a good migration channel for ions and electrons, which helps to maintain a stable current output at a higher charge and discharge rate. 2 ), the energy storage capacity of the battery can be improved to a certain extent, so as to improve the performance of the battery in terms of energy density.

[0085] At the same time, by specifically setting the proportion of the ternary material in the active material layer 120, the conductivity and bonding properties of the positive electrode 100 can be ensured. A too low b value may reduce the conductivity of the active material layer 120, affecting the battery's rapid charge and discharge capabilities, while a too high b value may reduce the mechanical strength of the positive electrode 100, affecting its cycling performance.

[0086] Furthermore, the surface density of the active material layer 120 is a, the mass ratio of the ternary material in the active material layer 120 is b, and the following relationship is satisfied:

[0087] 100g / m 2 ≤a≤325g / m 2 , 0.2≤b≤0.8.

[0088] In addition, in the above embodiment, the surface density (a) of the active material layer 120 may be 50 g / m 2 , 100g / m 2 , 200g / m 2 , 300g / m 2 , 350g / m 2 Or 50g / m 2 With 350g / m 2 At the same time, the mass proportion (b) of the ternary material in the active material layer 120 can be 0.2, 0.4, 0.6, 0.8 or any value between 0.2 and 0.8; in addition, in different positive electrode sheets 100, the mass proportion (b) of the ternary material in the active material layer 120 can also use materials with different values, which is not limited here.

[0089] In one embodiment, the surface density of the first active layer 121 is a1, and the surface density of the second active layer 122 is a2, and they satisfy the following relationship:

[0090] 25g / m2 ≤a1≤325g / m 2 , 25g / m 2 ≤a2≤325g / m 2 .

[0091] In this embodiment, the surface density of the first active layer 121 and the second active layer 122 is set to 25 g / m 2 Up to 325g / m 2 This not only optimizes the utilization efficiency of the active materials, but also has a positive impact on the overall electrochemical performance of the positive electrode sheet.

[0092] Specifically, an appropriate range of areal density ensures optimal material loading in active material layer 120. When the areal densities of a1 and a2 are within this range, the electrode can maintain adequate mechanical strength while ensuring sufficient current carrying capacity. During high-rate discharge, the electrode needs to quickly deliver current to meet the battery's performance requirements. By carefully controlling the areal density, the battery's power output can be maximized, thereby increasing its output current density and energy density.

[0093] Secondly, set it at 25g / m 2 The lower limit value of 325g / m2 makes the electrode have good ionic and electronic conductivity. This low surface density is conducive to the expansion and arrangement of active materials, forming a larger reaction interface, thereby increasing the reaction rate of the electrode. At the same time, when the surface density is close to 325g / m2, the electrode will have good ionic and electronic conductivity. 2 When the upper limit is reached, the quality of the active materials in the electrode is improved, which comprehensively increases the energy storage capacity of the battery. This process can be flexibly adjusted under different operating conditions to meet the needs of various applications.

[0094] Furthermore, proper design of the areal density can also improve the battery's cycling stability and lifespan. During the battery's charge and discharge processes, excessive areal density can lead to excessive internal pressure in the electrodes, potentially causing structural damage. However, maintaining a reasonable areal density range effectively prevents electrode delamination and crack formation, thereby extending the battery's service life and cycle count.

[0095] Furthermore, the surface density of the first active layer 121 is a1, and the surface density of the second active layer 122 is a2, and they satisfy the following relationship:

[0096] 75g / m 2 ≤a1≤300g / m 2 , 75g / m 2 ≤a2≤300g / m 2 ;0.25≤a2 / a1≤4.

[0097] In addition, in the above embodiment, the surface density a1 of the first active layer 121 and the surface density a2 of the second active layer 122 can be 25 g / m 2 , 100g / m 2 , 200g / m 2 , 280g / m 2 , 325g / m 2 Or 25g / m 2 With 325g / m 2 any value between; in addition, in different positive electrode sheets 100, the surface density a1 of the first active layer 121 and the surface density a2 of the second active layer 122 can also be set to different parameters, which are not limited here.

[0098] Specifically, the electrode preparation method of this embodiment includes the following steps:

[0099] Step S100: providing a current collector 110, and using the current collector 110 as a material base for the positive electrode sheet 100;

[0100] Step S200: providing a positive electrode slurry, wherein the positive electrode slurry includes a lithium manganese iron phosphate material and a ternary material;

[0101] Step S300: Apply the positive electrode slurry to the surface of the current collector 110 to form the active material layer 120. The active material layer 120 includes a first active layer 121 and a second active layer 122. By controlling the coating process, at least two active layers with different characteristics, the first active layer 121 and the second active layer 122, are formed on the current collector 110 to optimize the overall electrochemical performance of the positive electrode sheet 100. Specifically, after applying the positive electrode slurry to the current collector 110, the positive electrode sheet 100 can be prepared through processes such as baking, rolling, and cutting.

[0102] Specifically, step S200 includes: providing a lithium iron manganese phosphate material and a ternary material; and mixing a binder, a conductive agent, and a dispersant with the lithium iron manganese phosphate material and the ternary material to form a positive electrode slurry.

[0103] In this embodiment, lithium iron manganese phosphate material and ternary material are the main active ingredients in the positive electrode slurry. By adding a binder to the mixed material of lithium iron manganese phosphate material and ternary material, the adhesion between the lithium iron manganese phosphate material and the ternary material can be enhanced. The conductive agent can improve the conductivity of the positive electrode slurry, and the dispersant helps to evenly mix the various component materials in the positive electrode slurry, and finally form the positive electrode slurry through mixing processing.

[0104] In one embodiment, the adhesive includes polyvinylidene fluoride (PVDF) material.

[0105] Specifically, polyvinylidene fluoride has good chemical stability, thermal stability, mechanical properties, adhesion, insulation and processability. Specifically, polyvinylidene fluoride has good resistance to acid, alkali, chemical and solvent corrosion, good thermal stability and high temperature resistance, good strength and toughness, can provide firm support for active substances during the preparation process, has excellent electrical insulation properties, and is easy to process into films and coatings, and is suitable for a variety of coating processes.

[0106] In some embodiments, the adhesive may also be styrene-butadiene rubber (SBR) and may be used in combination with CMC for aqueous positive electrodes. The choice of adhesive is determined by the specific design requirements of the positive electrode sheet 100 and the battery, and is not a single limitation here.

[0107] In one embodiment, the conductive agent includes at least one of carbon black material, carbon nanotubes, and graphene.

[0108] Specifically, carbon black provides good conductivity and dispersibility at a low cost; carbon nanotubes have excellent conductivity and mechanical properties, significantly improving the electrode's conductive network; and graphene boasts extremely high conductivity and surface area, enhancing the electrode's overall performance and stability. In some embodiments, the conductive agent can also be a blend of these materials. The choice of conductive agent is determined by the specific design requirements of the positive electrode sheet 100 and the battery, and is not intended to be a single limitation.

[0109] Specifically, step S200 includes kneading and preparing the positive electrode slurry by a wet method or a semi-dry method.

[0110] In this embodiment, wet kneading can utilize a liquid medium to aid mixing, thereby improving the dispersion and adhesion of the various component materials in the positive electrode slurry. Semi-dry kneading can use less solvent, thereby reducing drying time and energy consumption while maintaining good mixing effect. The mixing method of the positive electrode slurry can be determined according to the specific design requirements of the positive electrode sheet 100 and the battery, and is not limited here.

[0111] Specifically, step S300 includes coating the positive electrode slurry on the current collector 110 using a double-layer coating method.

[0112] In this embodiment, the double-mouth die can be used for one-time coating, and two types of positive electrode slurries can be applied simultaneously through the two output ports of the double-mouth die. Thus, the double-mouth die can realize two-layer active layer coating processing in one moving process to quickly complete the coating and ensure the stratification and uniformity of the two layers of slurry.

[0113] By using multiple coatings, the active layer of the previous layer can be coated in sequence, and a positive electrode slurry with different components from the previous layer can be output in each coating, so that the first active layer 121 and the second active layer 122 formed in the end have different component ratios. Compared with double-layer coating, although the efficiency is relatively low, the thickness and structure of each layer can be better controlled. The coating method of the positive electrode slurry can be determined according to the specific design requirements of the positive electrode sheet 100 and the battery, and is not limited here. In addition, in some embodiments, a die with three or more ports can also be used for one-time coating. At this time, an active material layer 120 with corresponding multiple active layers can be formed according to the output port of the die head. No further details are given here.

[0114] Specifically, the battery in this embodiment includes a battery casing and a battery cell; the battery cell is housed in the battery casing; specifically, the battery cell includes a negative electrode sheet, a diaphragm and the positive electrode sheet 100 in any of the above embodiments, and the diaphragm is arranged between the positive electrode sheet 100 and the negative electrode sheet.

[0115] It can be understood that in the battery of this embodiment, by providing a battery cell having the positive electrode sheet 100 of any of the above embodiments, the positive electrode sheet 100 of this embodiment establishes a parameter relationship between the surface density and the active material layer 120 to form a first active layer 121 and a second active layer 122 having different material mass proportions. In the direction away from the current collector 110, the material proportion and surface density of the active material layer 120 of the positive electrode sheet 100 are differentially distributed. While ensuring the energy density of the positive electrode sheet 100, the internal resistance of the battery is further reduced, thereby effectively improving the ion and electron transport characteristics of the positive electrode sheet 100 and enhancing the battery kinetic performance. Specifically, the battery can be a laminated battery or a cylindrical battery.

[0116] Specifically, experiments were conducted on the battery in the above embodiment, and the materials and key processes used were as follows:

[0117] Active material content: Scrape off a small amount of powder from the second active layer 122 and use ICP to test the Ni element content, and then calculate the proportion of ternary materials in the second active layer 122; similarly, scrape off a small amount of powder from the first active layer 121, and use the same method to test the proportion of ternary materials in the first active layer 121.

[0118] Surface density: The total surface density of the positive electrode sheet 100 and the surface density of the current collector 110 can be obtained by weighing them respectively. The surface density of the active material layer 120 can be obtained by subtracting them. The thickness of the first active layer 121 and the second active layer 122 can be measured by cross-sectional SEM photos. The fixed area positive electrode sheet 100 is cut again (preferably the area of the cut positive electrode sheet 100 is larger than 50 cm 2), after scraping off the second active layer 122 according to thickness, use a cutter to cut discs with a diameter of 10-15 mm (preferably, the number of discs cut is more than 10), use a micrometer to measure the thickness of each disc, take discs with a thickness within ±3% of the actual thickness of the first active layer 121 and the current collector 110, weigh them and take the average value, and calculate the surface density of the first active layer 121. The surface density of the second active layer 122 can be obtained by subtracting the surface density of the first active layer 121 from the total surface density of the first active layer 121 and the second active layer 122.

[0119] The present invention is described in detail by way of examples, which include but are not limited to the following examples.

[0120] Example 1:

[0121]

[0122]

[0123] The active material layer 120 uses a 3% PVDF binder and a 1.5% carbon black conductive agent. The binder, conductive agent and active material are dispersed in N-methylpyrrolidone, and the viscosity is controlled at 3000±500mPa s. A double-layer coating is used on the current collector 110 to obtain the positive electrode sheet 100. The surface density a1 of the first active layer 121 is controlled to be 125g / m 2 The surface density a2 of the second active layer 122 is 125 g / m 2 , that is, a2 / a1=1; the mass proportion of the first ternary material in the first active layer 121 is b1=0.3, and the mass proportion of the second ternary material in the second active layer 122 is b2=0.7, that is, b2 / b1=2.33.

[0124] The specific preparation process is as follows: NMP (N-methylpyrrolidone) and PVDF (polyvinylidene fluoride) are added to a dual planetary mixer and stirred at high speed for 1-2 hours until the PVDF is completely dissolved. A conductive agent is then added and stirred at high speed for another hour. The two main materials, LMFP (lithium manganese iron phosphate) and NCM (ternary material), are then added separately and stirred at high speed for 2 hours to obtain a uniform positive electrode slurry. After sieving with a mesh, the slurry is coated using a coater and dried in an oven. The electrode sheet is then rolled using a roller press to obtain the desired positive electrode sheet.

[0125] Example 2:

[0126] In this embodiment, b1=0.4, b2=0.6, that is, b2 / b1=1.5, and other conditions remain unchanged from those in Example 1.

[0127] Example 3:

[0128] In this embodiment, a1 = 50 g / m 2 , a2=200g / m 2 , that is, a2 / a1=4, b1=0.1, b2=0.6, that is, b2 / b1=6, and other conditions remain unchanged as in Example 1.

[0129] Example 4:

[0130] In this embodiment, a1 = 200 g / m 2 , a2=50g / m 2 , that is, a2 / a1=0.25, b1=0.4, b2=0.9, that is, b2 / b1=2.25, and other conditions remain unchanged from Example 1.

[0131] Example 5:

[0132] In this embodiment, b1=0.05, b2=0.9, b2 / b1=18, and other conditions remain unchanged from those in Example 1.

[0133] Example 6:

[0134] In this embodiment, b1=0.408, b2=0.95, b2 / b1=2.33, and other conditions remain unchanged from those in Example 1.

[0135] Examples 7 to 64:

[0136] The steps are basically the same as those in Example 1, with the differences being a2 / a1, b2 / b1, the first lithium iron manganese phosphate material, the second lithium iron manganese phosphate material, the D50 particle size of the first lithium iron manganese phosphate material, the D50 particle size of the second lithium iron manganese phosphate material, the first ternary material, the second ternary material, the D50 particle size of the first ternary material, the D50 particle size of the second ternary material, the first active surface density a1, and the second active surface density a2. See Table 1 for details.

[0137] Comparative Example 1:

[0138] In Comparative Example 1, b1=0.8, b2=0.2, that is, b2 / b1=0.25, and other conditions remain unchanged from Example 1.

[0139] Comparative Example 2:

[0140] In Comparative Example 2, single-layer coating was performed, and other conditions remained unchanged from Example 1.

[0141] Comparative Example 3:

[0142] In Comparative Example 3, b1=0, b2=1, that is, the active material near the current collector layer is pure lithium manganese iron phosphate, and the active material near the electrolyte layer is pure ternary material.

[0143] Comparative Example 4:

[0144] In Comparative Example 4, a2 / a1=12.5, a1=10 ， a2=125, and other conditions remain unchanged from those in Example 1.

[0145] Performance testing:

[0146] The above examples and comparative examples provided positive and negative electrode sheets (specifically, obtained by coating a negative electrode slurry on a copper foil current collector and drying it; the ratio of graphite, carbon black conductive agent, and CMC binder in the negative electrode was 97:1:2), a separator (polypropylene separator), and an electrolyte (specifically, lithium hexafluorophosphate:ethylene carbonate:diethyl carbonate:vinylene carbonate = 12.93:43.54:43.54:4) and were assembled in the same manner to form a full cell. The discharge specific capacity, energy density, and DCIR (direct current internal resistance) of the resulting full cell were tested. The results are shown in Table 1.

[0147] Discharge capacity and energy density test conditions (room temperature):

[0148] Charge at room temperature at 1 / 3C constant current and constant voltage to 4.3V, with a cut-off current of 0.05C, and discharge at room temperature at 1 / 3C constant current to 2.5V for three cycles. The battery discharge specific capacity (unit: mAh / g) is calculated by dividing the last discharge capacity by the mass of the positive electrode active material; the energy density (unit: Wh / kg) is calculated by dividing the last discharge energy by the mass of the positive electrode active material.

[0149] DCIR test conditions (normal temperature):

[0150] The battery at room temperature is charged to 4.3V at 1 / 3C constant current and constant voltage, with a cut-off current of 0.05C. It is discharged at room temperature at 1 / 3C constant current for 90min. At this time, the SOC of the battery is 50%. The termination voltage V0 after standing for 1h and the termination voltage V1 after 1.5C discharge for 30s are calculated. The internal resistance R is calculated using the formula: R = (V1-V0) / 1.5 (unit: mΩAh), and the 50% SOC discharge DCIR can be obtained. Repeat the above test, changing the room temperature 1 / 3C constant current discharge step time to 36min and 126min, and the 80% SOC discharge DCIR and 30% SOC discharge DCIR can be obtained respectively.

[0151] Table 1

[0152]

[0153]

[0154] As can be seen from Table 1, compared with the single-layer coating (Comparative Example 2), the double-layer coating method in the present application can significantly reduce the DCIR of the battery and improve the discharge specific capacity and energy density of the battery.

[0155] Compared with the active material layer using a double-layer coating, but the double layers are separately coated with lithium manganese iron phosphate and ternary materials (Comparative Example 3), because the impedance of the pure LMFP layer is large, there is no significant effect on reducing DCIR, and the battery capacity is low, so the double-layer coating scheme in this application can significantly improve the discharge capacity and energy density of the battery, while further reducing the internal resistance of the battery.

[0156] Based on Examples 1-64, it can be judged that by adopting a double-layer coated electrode scheme and controlling the ratio of the surface density of the first active layer and the second active layer and the proportion of the ternary material within an appropriate range, the discharge capacity and energy density of the battery can be improved while reducing the internal resistance of the battery.

[0157] When the ratio of the surface density of the first active layer to the second active layer and the ratio of the ternary materials are outside the given range (Comparative Example 1, Comparative Example 4), the discharge capacity, energy density and DCIR performance of the battery are all reduced.

[0158] Therefore, in the positive electrode sheet 100 of this embodiment, by adopting a double-layer coated electrode scheme and controlling the ratio of the surface density of the first active layer and the second active layer and the proportion of the ternary materials within a suitable range, a first active layer 121 and a second active layer 122 having different material mass proportions are formed. In the direction from the current collector 110 to the electrolyte, the proportion and surface density of the materials in the active material layer 120 of the positive electrode sheet 100 are differentially distributed. While ensuring the energy density of the positive electrode sheet 100, the internal resistance of the battery is further reduced, thereby effectively improving the ion and electron transport characteristics of the positive electrode sheet 100 and enhancing the battery kinetic performance.

[0159] The present invention further provides an electrical device, comprising an electrical device and the battery in any one of the above embodiments, wherein the battery is electrically connected to the electrical device and is used to supply power to the electrical device.

[0160] It can be understood that the electrical equipment provided in the embodiments of the present application is powered by the battery in any of the above embodiments. The positive electrode sheet 100 of this embodiment establishes a parameter relationship between the surface density and the active material layer 120 to form a first active layer 121 and a second active layer 122 with different material mass proportions. In the direction from the current collector 110 to the electrolyte, the proportion and surface density of the materials in the active material layer 120 of the positive electrode sheet 100 are differentially distributed. While ensuring the energy density of the positive electrode sheet 100, the internal resistance of the battery is further reduced, thereby effectively improving the ion and electron transmission characteristics of the positive electrode sheet 100 and enhancing the battery kinetic performance.

[0161] In the embodiments of the present application, the power-consuming device may also be a smart wearable device, such as a smart watch. The power-consuming device may also be a mobile phone, a tablet computer, or a laptop computer. In some embodiments, the power-consuming device may also be a vehicle, which may be a new energy vehicle (New Energy Vehicle), such as a pure electric vehicle (Pure Electric Vehicle / Battery Electric Vehicle; abbreviated as: PEV / BEV), a range-extended electric vehicle (Range Extended Electric Vehicle; abbreviated as: REEV), a hybrid electric vehicle (Hybrid Electric Vehicle; abbreviated as: HEV), or a fuel cell electric vehicle. The vehicle may also be any vehicle with a battery. The power-consuming device may also be an energy storage power station.

[0162] In the description of the embodiments of the present application, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0163] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on the specific circumstances.

[0164] In the embodiments of the present application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0165] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A positive electrode sheet, characterized in that: Comprising: Current collector; And The active material layer includes a first active layer and a second active layer, wherein the first active layer is provided on at least one side of the current collector, and the second active layer is provided on a side of the first active layer away from the current collector; the first active layer includes a first lithium iron manganese phosphate material and a first ternary material, and the second active layer includes a second lithium iron manganese phosphate material and a second ternary material; the surface density of the first active layer is a1, and the mass proportion of the first ternary material in the first active layer is b1; the surface density of the second active layer is a2, and the mass proportion of the second ternary material in the second active layer is b2, and the units of a1 and a2 are g / m 2 , and satisfy the following relationship: 0.05 ≤ b1 < 0.95, 0.05 < b2 ≤ 0.95; 0.1 ≤ a2 / a1 ≤ 10, and b1 < b2.

2. The positive electrode sheet according to claim 1, characterized in that The areal density of the first active layer is a1, the mass ratio of the first ternary material in the first active layer is b1, the areal density of the second active layer is a2, and the mass ratio of the second ternary material in the second active layer is b2, and the following relational expressions are satisfied: When 0.1 ≤ a2 / a1 ≤ 0.5, 10 ≤ b2 / b1 ≤ 18; When 0.5 < a2 / a1 ≤ 10, 1.5 ≤ b2 / b1 ≤ 10.

3. The positive electrode sheet according to claim 2, characterized in that: The a1 and a2, and b1 and b2 satisfy the following relational expressions: When 0.15 ≤ a2 / a1 ≤ 0.5, 10 ≤ b2 / b1 ≤ 15; When 0.5 < a2 / a1 ≤ 8, 2 ≤ b2 / b1 ≤ 10.

4. The positive electrode sheet according to claim 1, characterized in that The first lithium iron manganese phosphate material is LiMn x Fe 1- x PO4, wherein 0.55≤x≤0.85, and / or the second lithium manganese iron phosphate material is LiMn y Fe 1-y PO4, where 0.55≤y≤0.85; The first lithium iron manganese phosphate material is LiMn x Fe 1-x PO4, wherein 0.6≤x≤0.8, and / or the second lithium manganese iron phosphate material is LiMn y Fe 1-y PO4, where 0.6≤y≤0.

8.

5. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The x and y satisfy the following relational expression: x ≥ y.

6. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The D50 particle size of the first lithium iron phosphate manganese is 10 - 400 nm, and / or the D50 particle size of the second lithium iron phosphate manganese is 10 - 400 nm; Preferably, the D50 particle size of the first lithium iron phosphate manganese is 20 - 350 nm, and / or the D50 particle size of the second lithium iron phosphate manganese is 20 - 350 nm.

7. The positive electrode sheet according to claim 6, characterized in that: The D50 particle size of the first lithium iron phosphate manganese is greater than the D50 particle size of the second lithium iron phosphate manganese.

8. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The first ternary material is LiNi m Co n Mn 1-m-n O2, wherein 0.5≤m≤0.8, 0.05≤n≤0.3, and / or the second ternary material is LiNi j Co k Mn 1-j-k O2, where 0.5≤j≤0.8, 0.05≤k≤0.3; Preferably, the first ternary material is LiNi m Co n Mn 1-m-n O2, wherein 0.55≤m≤0.75, 0.08≤n≤0.25; and / or the second ternary material is LiNi j Co k Mn 1-j-k O2, where 0.55≤j≤0.75, 0.08≤k≤0.

25.

9. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The D50 particle size of the first ternary material is 1 - 15 μm, and / or the D50 particle size of the second ternary material is 1 - 15 μm.

10. The positive electrode sheet according to claim 1, characterized in that: The areal density of the first active layer is a1, the areal density of the second active layer is a2, and the following relational expressions are satisfied: 25g / m 2 ≤a1≤325g / m 2 ,25g / m 2 ≤a2≤325g / m 2 ; Preferably, 75g / m 2 ≤a1≤300g / m 2 , 75g / m 2 ≤a2≤300g / m 2 .

11. A battery, characterized in that: Comprising the positive electrode sheet according to any one of claims 1 - 10.

12. An electrical device, characterized in that: Comprising the battery according to claim 11.

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