Electrode sheet, method of manufacturing the same, electrochemical device, and electric equipment

Abstract

This application discloses an electrode sheet and its preparation method, an electrochemical device, and an electrical device. The electrode sheet includes: a current collector, a first electrode material layer, and a second electrode material layer. The first electrode material layer includes multiple first particle regions, each including at least one first active material particle region and at least one second active material particle region. The second electrode material layer includes multiple second particle regions, each including at least one third active material particle region and at least one fourth active material particle region. The electrode sheet includes at least one particle row arranged along the length direction of the current collector, the particle row including particle regions on the first electrode material layer and particle regions on the second electrode material layer; each particle row contains a first active material particle region and / or a third active material particle region. The electrode sheet of this application has strong mass transfer capability, balances good kinetics and energy density, and exhibits excellent overall performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to electrode sheets and their preparation methods, electrochemical devices, and electrical equipment. Background Technology

[0002] Lithium batteries have become an important part of the modern energy field due to their advantages such as high energy density, low self-discharge rate, good cycle performance and environmental friendliness. They are widely used in electric vehicles, portable appliances and other energy storage devices.

[0003] Nanostructuring of active particles in lithium-ion batteries is a common method to shorten solid-phase diffusion distance and increase the specific surface area for electrochemical reactions, thereby improving the low-temperature kinetics of the battery. However, reducing particle size decreases electrode compaction density, leading to a reduction in volumetric energy density. Therefore, balancing energy density and kinetics is one of the urgent problems to be solved. Summary of the Invention

[0004] This application aims to at least partially solve one of the technical problems in the related art. To this end, one objective of this application is to provide an electrode sheet and its preparation method, an electrochemical device, and an electrical device. The electrode sheet of this application has strong mass transfer capability, low internal resistance, and good kinetics and energy density, exhibiting excellent overall performance.

[0005] The first aspect of this application discloses an electrode sheet, the electrode sheet comprising:

[0006] current collector;

[0007] A first electrode material layer is disposed on at least one side of the current collector;

[0008] The second electrode material layer is disposed on the side of the first electrode material layer away from the current collector;

[0009] The first electrode material layer includes a plurality of first particle regions, each of which includes at least one first active material particle region and at least one second active material particle region. The first and second active material particle regions are arranged alternately along the length direction of the current collector. The first active material particle region contains first active material particles, and the second active material particle region contains second active material particles. The average particle size of the first active material particles is greater than the average particle size of the second active material particles.

[0010] The second electrode material layer includes a plurality of second particle regions, each of which includes at least one third active material particle region and at least one fourth active material particle region. The third active material particle region and the fourth active material particle region are arranged alternately along the length direction of the current collector. The third active material particle region contains third active material particles, and the fourth active material particle region contains fourth active material particles. The average particle size of the third active material particles is greater than the average particle size of the fourth active material particles.

[0011] The electrode sheet includes at least one column of particles arranged along the length direction of the current collector. The column of particles includes at least one of the first active material particle region and the second active material particle region on the first electrode material layer, and at least one of the third active material particle region and the fourth active material particle region on the second electrode material layer.

[0012] Each of the particle columns contains the first active material particle region and / or the third active material particle region.

[0013] According to the electrode sheet of this application, based on the characteristics and main problems of the electrode sheet, two layers of electrode material are used along the thickness direction of the current collector. In each layer of electrode material, large particle regions and small particle regions are alternately arranged along the length direction of the current collector. In the particle rows arranged along the thickness direction of the current collector, each particle row contains a large particle region. Thus, by controlling the stacking position of large and small particles, their respective advantages are utilized, improving the mass transfer capacity of the stacking structure, reducing internal resistance, thereby improving electrode dynamics, while also taking into account energy density, and improving the overall performance of the electrode sheet.

[0014] According to embodiments of this application, the electrode sheet may also have the following additional technical features;

[0015] According to an embodiment of this application, the particle array includes a first active material particle region or a second active material particle region on the first electrode material layer and a third active material particle region or a fourth active material particle region on the second electrode material layer.

[0016] According to embodiments of this application, the particle column contains a first active material particle region and a fourth active material particle region; or, the particle column contains a second active material particle region and a third active material particle region.

[0017] And / or, the average particle size of the third active material particles is greater than the average particle size of the second active material particles.

[0018] According to an embodiment of this application, the average particle size ratio of the first active material particle and the second active material particle is (1.1 to 4):1;

[0019] And / or, the average particle size ratio of the third active material particles to the fourth active material particles is (1.1 to 4):1;

[0020] And / or, the ratio of the average particle size of the first active material particles to that of the fourth active material particles is (1.1 to 4):1;

[0021] And / or, the ratio of the average particle size of the third active material particles to that of the second active material particles is (1.1 to 4):1;

[0022] And / or, the average particle size of the first active material particles and the third active material particles are independently 0.2 μm to 3.2 μm;

[0023] And / or, the average particle size of the second active material particles and the fourth active material particles are independently 0.05 μm to 0.8 μm.

[0024] According to an embodiment of this application, the ratio of the average particle size of the first active material particle to the second active material particle is (2.2~2.6):1;

[0025] And / or, the average particle size ratio of the third active material particles to the fourth active material particles is (2.2 to 2.6):1.

[0026] And / or, the average particle size of the first active material particles and the third active material particles are independently 0.4 μm to 0.8 μm;

[0027] And / or, the average particle size of the second active material particles and the fourth active material particles are independently 0.15 μm to 0.4 μm.

[0028] According to an embodiment of this application, the number of the second active material particles accounts for 1% to 60% of the total number of the first active material particles and the second active material particles in the first electrode material layer.

[0029] And / or, the number of the fourth active material particles accounts for 1% to 60% of the total number of the third and fourth active material particles in the second electrode material layer.

[0030] According to an embodiment of this application, along the length direction of the current collector, the width of the second active material particle region is greater than the width of the fourth active material particle region;

[0031] And / or, along the length direction of the current collector, the width of the first active material particle region and the third active material particle region are each independently 10 μm to 100 μm;

[0032] And / or, along the length direction of the current collector, the widths of the second active material particle region and the fourth active material particle region are each independently 1 μm to 20 μm.

[0033] According to embodiments of this application, the maximum powder compaction density of the first active material particles and the third active material particles is independently 2.4 g / cm³. 3 ~2.8g / cm 3 ;

[0034] And / or, the maximum powder compaction density of the second active material particles and the fourth active material particles is independently 2.1 g / cm³. 3 ~2.5g / cm 3 ;

[0035] And / or, the compaction density of the electrode sheet is 2.5 g / cm³. 3 ~2.7g / cm 3 .

[0036] According to an embodiment of this application, the first active material particle, the second active material particle, the third active material particle, and the fourth active material particle are selected from positive electrode active materials, wherein the positive electrode active materials include one or more of lithium transition metal oxides, lithium-containing phosphates, sodium transition metal oxides, and sodium-containing phosphates.

[0037] Alternatively, the first active material particle, the second active material particle, the third active material particle, and the fourth active material particle are selected from one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide ternary materials, lithium nickel cobalt aluminum oxide ternary materials, lithium manganese oxide, and lithium cobalt oxide.

[0038] According to embodiments of this application, the first active material particle, the second active material particle, the third active material particle, and the fourth active material particle are selected from negative electrode active materials, wherein the negative electrode active materials include one or more of graphite, silicon, and lithium titanate.

[0039] According to an embodiment of this application, the thickness of the first electrode material layer and the second electrode material layer are each independently 80 μm to 120 μm.

[0040] A second aspect of this application discloses a method for preparing an electrode sheet, the method comprising:

[0041] On at least one side of the current collector, a first slurry and a second slurry are alternately applied along the length direction of the current collector to form a first electrode material layer comprising at least one first active material particle region and at least one second active material particle region, wherein the first slurry contains first active material particles and the second slurry contains second active material particles.

[0042] On the side of the first electrode material layer away from the current collector, a third slurry and a fourth slurry are alternately applied along the length direction of the current collector to form a second electrode material layer including at least one region of the third active material particles and at least one region of the fourth active material particles. The third slurry contains third active material particles, and the fourth slurry contains fourth active material particles.

[0043] A third aspect of this application provides an electrochemical device comprising the electrode sheet described in the first aspect of this application.

[0044] The fourth aspect of this application discloses an electrical device, which includes the electrochemical device described in the third aspect of this application.

[0045] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0046] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0047] Figure 1 A schematic diagram of an electrode sheet structure according to an embodiment of this application is shown;

[0048] Figure 2 A schematic diagram of an electrode sheet structure according to another embodiment of this application is shown;

[0049] Figure 3 This shows a schematic diagram of the electrode sheet structure according to yet another embodiment of this application;

[0050] Figure 4 This invention illustrates a schematic diagram of the electrode fabrication process according to an embodiment of the present application;

[0051] Figure 5 A schematic diagram of a container structure for applying slurry according to an embodiment of this application is shown.

[0052] Figure label:

[0053] 1000 Electrode sheet; 100 Current collector; 200 First electrode material layer; 300 Second electrode material layer; 210 First active material particle region; 220 Second active material particle region; 310 Third active material particle region; 320 Fourth active material particle region; 10 First active material particle; 20 Second active material particle; 30 Third active material particle; 40 Fourth active material particle. Detailed Implementation

[0054] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0055] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0056] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0057] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this application but do not exclude other contents.

[0058] Nano-sizing of active particles in lithium-ion batteries is a common method to shorten solid-phase diffusion distance and increase the specific surface area for electrochemical reactions, thereby improving the low-temperature kinetics of batteries. However, reducing particle size decreases electrode compaction density, leading to a reduction in volumetric energy density.

[0059] Currently, existing technologies widely employ a combination of large and small particles to balance energy density and kinetics. However, on the one hand, higher space utilization in the packing of large and small particles leads to lower electrode porosity, resulting in a decrease in liquid-phase mass transfer capability; on the other hand, increasing the doping amount of small particles increases the number of particles per unit volume, leading to an increase in the number of charge transport interfaces. In other words, when the proportion of small particles exceeds a certain value, both electron and ion transport capabilities of the electrode deteriorate, causing the battery's internal resistance to increase with the increase in the doping amount of small particles. Ultimately, batteries doped with small particles exhibit a contradictory situation: improved low-temperature continuous charge-discharge capability but decreased pulse charge-discharge capability (especially at room temperature).

[0060] Existing designs employ a gradation of small carbon-coated particles and large, uncoated particles, aiming to provide electron transport pathways for the small carbon-coated particles and ion transport pathways for the large, uncoated particles, thus achieving rapid electron and ion transport at the interface. However, the ionic conductivity of the active material is lower than that of the electrolyte, and its electronic conductivity is far lower than that of conductive agents such as carbon black / acetylene black. Therefore, in the aforementioned technology, the electrochemical reaction of the uncoated large particles can only begin from a single point of contact with the conductive agent, unlike the carbon-coated active particles which can react from all directions on the surface. This results in a significant decrease in the proportion of lithium insertion / extraction / deintercalation that can be performed on the large particles at high rates and low temperatures, which are kinetically limited, thus affecting the overall battery performance. Therefore, this method of improving the electrode's ion transport capability by sacrificing the electron conduction capability of the large particles is not a good solution.

[0061] Based on the characteristics and main problems of the electrode sheet, this application employs two layers of electrode material along the thickness direction of the current collector. In each electrode material layer, large and small particle regions are alternately arranged along the length of the current collector. Each particle row arranged along the thickness direction contains a large particle region. Therefore, by controlling the stacking positions of the large and small particles, their respective advantages are utilized, improving the mass transfer capacity of the stacked structure, reducing internal resistance, and thus improving electrode dynamics. Furthermore, without introducing new materials or changing the compaction density of the electrode sheet, energy density is considered, achieving an overall performance improvement.

[0062] In the terminology of this application, "mass transfer" refers to the migration process of charge / ions within the battery from the electrolyte phase to the electrode active material phase. This process is crucial to the battery's charge-discharge performance, directly determining its charge-discharge rate, energy density, and cycle life. The mass transfer process mainly includes two aspects: the diffusion of charge / ions from the liquid phase to the electrode surface and the diffusion of charge / ions from the solid phase within the electrode material.

[0063] Based on this, an electrode sheet is proposed in the first aspect of this application. Figure 1 A schematic diagram of the electrode sheet structure of this application is shown. The electrode sheet 1000 includes: a current collector 100, a first electrode material layer 200 and a second electrode material layer 300. The first electrode material layer 200 is disposed on at least one side of the current collector 100, and the second electrode material layer 300 is disposed on the side of the first electrode material layer 200 away from the current collector 100.

[0064] Specifically, the first electrode material layer 200 includes a plurality of first particle regions, each of which includes at least one first active material particle region 210 and at least one second active material particle region 220. The first active material particle region 210 and the second active material particle region 220 are arranged alternately along the length direction of the current collector 100. The first active material particle region 210 contains first active material particles 10, and the second active material particle region 220 contains second active material particles 20. The average particle size of the first active material particles 10 is greater than the average particle size of the second active material particles 20.

[0065] The second electrode material layer 300 includes a plurality of second particle regions, each including at least one third active material particle region 310 and at least one fourth active material particle region 320. The third active material particle region 310 and the fourth active material particle region 320 are arranged alternately along the length direction of the current collector 100. The third active material particle region 310 contains third active material particles 30, and the fourth active material particle region 320 contains fourth active material particles 40. The average particle size of the third active material particles 30 is greater than the average particle size of the fourth active material particles 40.

[0066] The electrode sheet 10 includes at least one column of particles arranged along the length direction of the current collector 100. The column of particles includes at least one of a first active material particle region 210 and a second active material particle region 220 on the first electrode material layer 200, and at least one of a third active material particle region 310 and a fourth active material particle region 320 on the second electrode material layer 300.

[0067] Each particle column contains a first active material particle region 210 and / or a third active material particle region 230.

[0068] For ease of understanding, in this application, the first active material particle 10 and the third active material particle 30 are both referred to as "large particles," and the corresponding particle region is also referred to as the "large particle region"; the second active material particle 20 and the fourth active material particle 40 are both referred to as "small particles," and the corresponding particle region is also referred to as the "small particle region." The materials and sizes of the large particles may be the same or different, and the materials and sizes of the small particles may be the same or different, depending on actual needs. The length direction of the current collector is also referred to as the "transverse direction," and the thickness direction of the current collector is also referred to as the "longitudinal direction."

[0069] Pore ​​structures formed by the packing of particles of different sizes can be categorized into three types: the first type, formed by the packing of large particles, exhibits the best mass transfer capacity; the second type, formed by the packing of small particles, has a relatively poor mass transfer capacity; and the third type, formed by the packing of large and small particles, has a mass transfer capacity lower than the first type. Therefore, electrodes with a mixture of large and small particle packings will exhibit optimal kinetics if mass transfer can be achieved through the first type of pore structure.

[0070] Based on this, the electrode sheet of this application utilizes the advantages of both large and small particle partitioning in both the lateral and longitudinal directions. Specifically, large and small particle regions are alternately arranged in the lateral direction, and at least two layers are used in the longitudinal direction, with each longitudinal particle row containing a large particle region within its two layers. Large particles stacked together form a longitudinal channel from the current collector to the membrane side, serving as the main channel for charge / ion longitudinal transport and completing the longitudinal mass transfer task. The regions formed by small particle stacks act as lateral branches, acquiring electrons and ions required for the electrochemical reaction from the main channel. This avoids the problems of pore blockage and increased electrochemical mass transfer tortuosity caused by small particle doping in conventional mixed-stacking structures, allowing the doped small particles to only exert their kinetic advantages of shortening the solid-phase diffusion distance and increasing the electrochemical reaction activity surface area.

[0071] The following will combine Figure 2 The advantages of the electrode sheet structure design in this application are explained in detail:

[0072] Lithium ions released from small particle A need to be transported to the separator side and then to the counter electrode, while electrons released from small particle B need to be transported to the current collector and then to the external circuit. Through mass transfer via the longitudinal channel formed by the large particle packing region, lithium ions released from A need to cross four large particles to reach the separator side (transfer distance denoted as a1), and electrons released from B also need to cross four large particles to reach the current collector (transfer distance denoted as b1). This is the shortest distance that particles A and B need to cross for mass transfer. Conversely, if mass transfer occurs in the small particle packing region, lithium ions released from A need to cross seven small particles to reach the separator side (transfer distance denoted as a2), and electrons released from B also need to cross seven small particles to reach the current collector side (transfer distance denoted as b2). Therefore, by using the longitudinal channel mass transfer formed by the large particle packing region, the number of particles crossed by lithium ions is reduced and the mass transfer distance is shorter, thus improving mass transfer capability and resulting in more significant kinetic benefits.

[0073] It is understood that the electrode sheet 1000 of this application includes at least one first electrode material layer 100 and at least one second electrode material layer 200, and the first electrode material layer 100 and the second electrode material layer 200 are stacked alternately in sequence.

[0074] For example, each particle column can contain both large and small particles, such as Figure 1 The first column on the left can also contain large particles, for example... Figure 3 The first column on the right side of the middle column only needs to ensure that it does not contain small particles simultaneously. Preferably, it contains both large and small particles, which helps to further reduce internal resistance and improve mass transfer capacity.

[0075] In some embodiments of this application, the particle array includes the first active material particle region 210 or the second active material particle region 220 on the first electrode material layer 200 and the third active material particle region 310 or the fourth active material particle region 320 on the second electrode material layer 300. Figure 1 For example, the first column of particles on the left side of the first electrode material layer 200 contains only large particles. Compared to a column containing both large and small particles (stacked vertically), this is more conducive to mass transfer, reduces internal resistance, and improves battery kinetic performance. Similarly, each column of particles in the second electrode material layer 300 contains a third active material particle region 310 or a fourth active material particle region 320. This further facilitates mass transfer, reduces internal resistance, and improves battery kinetic performance.

[0076] In some embodiments of this application, the particle column contains a first active material particle region 210 and a fourth active material particle region 320, for example... Figure 1 The first column on the left; or, the particle column contains a second active material particle region 220 and a third active material particle region 310, for example. Figure 1 The first column on the right.

[0077] In some embodiments of this application, the average particle size of the first active material particles 10 is greater than the average particle size of the fourth active material particles 40. This avoids the situation where a column of particles consists entirely of small particles.

[0078] In some embodiments of this application, the thicknesses of the first electrode material layer 200 and the second electrode material layer 300 are each independently 80 μm to 120 μm, for example, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, or any two values ​​as endpoints forming a range. Therefore, the electrochemical device containing the electrode sheet of this application has better rate performance and cycle stability.

[0079] In some embodiments of this application, the compaction density of the electrode sheet 1000 is 2.5 g / cm³. 3 ~2.7g / cm 3 For example, it can be 2.5g / cm³. 3 2.55g / cm 3 2.6g / cm 3 2.65g / cm 3 2.7g / cm 3 This application, without sacrificing energy density, improves the mass transfer capability of the electrode sheet. By adopting the above-mentioned compaction density, the specific capacity and energy density of the electrochemical device can be further improved, and the charge-discharge efficiency and cycle stability are better.

[0080] In this application, the term "compacted density" refers to the maximum packing density of the electrode material under specific conditions, typically expressed in grams per cubic centimeter (g / cm³). 3 The unit is ) . Specifically, the method for measuring the compaction density of this application is as follows: samples are taken at three random locations on the electrode sheet using a 1.5mm diameter circular cutter, the thickness is measured with a micrometer, the weight is measured with an electronic balance, and the compaction density of the electrode sheet is calculated.

[0081] In some embodiments of this application, the maximum powder compaction density of the first active material particle 10 and the third active material particle 30 is independently 2.4 g / cm³. 3 ~2.8g / cm 3 For example, it can be 2.4 g / cm³. 3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 Alternatively, any two values ​​can be used as endpoints to form a range. In some embodiments of this application, the maximum powder compaction density of the second active material particle 20 and the fourth active material particle 40 is independently 2.1 g / cm³. 3 ~2.5g / cm 3 For example, it can be 2.1 g / cm³. 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 Alternatively, any two values ​​can be used as endpoints to form a range. Therefore, the pore structures formed between large particles and between small particles are better, with shorter mass transfer distances. This is beneficial for both the longitudinal channels formed between large particles to complete longitudinal mass transfer and the lateral branches formed by the accumulation of small particles to acquire electrons and ions, thus improving overall mass transfer capacity while also considering energy density.

[0082] In this application, the term "maximum powder compaction density" refers to the density of particles measured by the method in accordance with GB / T 1479.1 2011 after holding the particles under a pressure of 200 MPa for 10 s.

[0083] In some embodiments of this application, the average particle size of the third active material particle 30 is greater than the average particle size of the second active material particle 20. In other embodiments of this application, the ratio of the average particle size of the first active material particle 10 to the second active material particle 20, the ratio of the average particle size of the third active material particle 30 to the fourth active material particle 40, and the ratio of the average particle size of the first active material particle 10 to the fourth active material particle 40 are (1.1–4):1, and the ratio of the average particle size of the third active material particle 30 to the second active material particle 20 is (1.1–4):1. For example, it can be 1.1, 1.5, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.5, 4, or any two values ​​forming a range of endpoints, preferably (2.2–2.6):1. In still other embodiments of this application, the average particle size of the third active material particle 30 is greater than the average particle size of the second active material particle 20. In some other embodiments of this application, the average particle size of the first active material particles and the third active material particles are independently 0.2 μm to 3.2 μm, for example, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm or any two values ​​as endpoints forming a range, preferably 0.4 μm to 0.8 μm. In some other embodiments of this application, the average particle size of the second active material particles and the fourth active material particles are independently 0.05 μm to 0.8 μm, for example, 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.6 μm, 0.8 μm or any two values ​​as endpoints forming a range, preferably 0.15 μm to 0.4 μm, more preferably 0.15 μm to 0.3 μm.

[0084] Therefore, the pore structures formed between large particles and between small particles are better, and the mass transfer distance is shorter. This is beneficial for the longitudinal channels formed between large particles to complete longitudinal mass transfer, and also for the transverse branches formed by the accumulation of small particles to acquire electrons and ions, thus improving the overall mass transfer capacity while taking into account the energy density.

[0085] In this application, the average particle size is expressed in terms of D 50 The value represents "D" 50 "D value" refers to the particle size value located in the middle of the distribution after arranging the particles in order of size; that is, half of the particles have a particle size smaller than D. 50 The value, the other half of the particles have a diameter greater than D.50 Value. D 50 The value is typically determined based on the cumulative frequency curve of the particle size distribution, i.e., the cumulative percentage of particle size. This curve shows the cumulative distribution from smallest to largest particle size. On the cumulative frequency curve, D... 50 The value corresponds to the point where the cumulative frequency is 50%. In other words, D 50 The value is the particle size corresponding to the intersection of the cumulative curve and the 50% cumulative frequency line.

[0086] In some embodiments of this application, along the length direction of the current collector 100, the width of the second active material particle region is greater than the width of the fourth active material particle region. In some embodiments of this application, along the length direction of the current collector 100, the widths of the first and third active material particle regions are each independently 1 μm to 100 μm, for example, they can be 1 μm, 10 μm, 30 μm, 50 μm, 60 μm, 80 μm, 100 μm, or any two values ​​forming a range. In some embodiments of this application, along the length direction of the current collector 100, the widths of the second and fourth active material particle regions are each independently 1 μm to 20 μm, for example, they can be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, or any two values ​​forming a range. Therefore, the pore structures formed between large particles and between small particles are better, and the mass transfer distance is shorter. This is beneficial for the longitudinal channels formed between large particles to complete longitudinal mass transfer, and also for the transverse branches formed by the accumulation of small particles to acquire electrons and ions, thus improving the overall mass transfer capacity while taking into account the energy density.

[0087] In some embodiments of this application, the number of second active material particles 20 accounts for 1% to 60% of the total number of first active material particles 10 and second active material particles 20 in the first electrode material layer 200 (also referred to as "doping amount" in this application). For example, it can be a range formed by 1%, 10%, 20%, 30%, 40%, 50%, 60%, or any two values ​​as endpoints. In other embodiments of this application, the number of fourth active material particles 40 accounts for 1% to 60% of the total number of third active material particles 30 and fourth active material particles 40 in the second electrode material layer 300. For example, it can be a range formed by 1%, 10%, 20%, 30%, 40%, 50%, 60%, or any two values ​​as endpoints. Therefore, the pore structures formed between large particles and between small particles are better, and the mass transfer distance is shorter. This is beneficial for the longitudinal channels formed between large particles to complete longitudinal mass transfer, and also for the transverse branches formed by the accumulation of small particles to acquire electrons and ions, thus improving the overall mass transfer capacity while taking into account the energy density.

[0088] In this application, along the length of the current collector, there is a quantitative correspondence between the width of the particle row (also referred to as the "lateral partition width" in this application) and the size of the large and small particles and the doping amount of the small particles. Let the average sizes of the large and small particles be d1 and d2, respectively, the maximum powder compaction densities be ρ1 and ρ2 (the maximum powder compaction density is the value in the powder pressure-compaction curve of the particle that remains almost constant with increasing pressure), the doping amount of the small particles be x, and the lateral partition widths be w1 and w2 (the maximum powder compaction density depends on the size). If w1 = n1d1 (n1 is a natural number), then w2 = n2d2 = n1d1ρ1x / (ρ2(1-x)) (n2>1 and is a natural number). The ideal solution for n2 is 2. Given that the process is feasible, it is desirable for n2 to be as small as possible (too many small particles will affect mass transfer). That is, n2 is a control parameter, and n2 / n is obtained through the above formula. 1＝ d1ρ1x / (d2ρ2(1-x)), when the size of the large and small particles and the doping amount of the small particles are determined, the ratio of the transverse partition width coefficient n2 / n1 is determined.

[0089] In some embodiments of this application, the first active material particle 10, the second active material particle 20, the third active material particle 30, and the fourth active material particle 40 are selected from positive electrode active materials, which include one or more of lithium transition metal oxides, lithium-containing phosphates, sodium transition metal oxides, and sodium-containing phosphates.

[0090] In some embodiments of this application, the first active material particle 10, the second active material particle 20, the third active material particle 30, and the fourth active material particle 40 are selected from one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide ternary materials, lithium nickel cobalt aluminum oxide ternary materials, lithium manganese oxide, and lithium cobalt oxide.

[0091] In some embodiments of this application, the first active material particle 10, the second active material particle 20, the third active material particle 30, and the fourth active material particle 40 are selected from negative electrode active materials, including one or more of graphite, silicon, and lithium titanate.

[0092] In some embodiments of this application, for the positive electrode sheet, the current collector may include a metal foil or a composite positive current collector. For example, the metal foil may be aluminum foil. The composite positive current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. For example, the composite negative current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0093] In some embodiments of this application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer 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 (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0094] In some embodiments of this application, the first electrode material layer 200 and the second electrode material layer 300 each independently include a binder and a conductive agent. The binder is used to bond and retain the electrode material layers, enhance the electronic contact between the material layers and the current collector, and better stabilize the structure of the electrode sheet. The conductive agent enables the electrode sheet to have good charge and discharge performance, reduces the contact resistance of the electrode sheet, accelerates the electron mobility, and thus improves the charge and discharge efficiency of the electrode sheet. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0095] The second aspect of this application discloses a method for preparing an electrode sheet, see [link to relevant documentation]. Figure 3 The method includes: S100 forming a first electrode material layer and S200 forming a second electrode material layer. Each step will be described in detail below.

[0096] S100 forms the first electrode material layer

[0097] In this step, a first slurry and a second slurry are alternately applied along the length of the current collector on at least one side to form a first electrode material layer comprising at least one first active material particle region and at least one second active material particle region. The first slurry contains first active material particles, and the second slurry contains second active material particles.

[0098] S200 forms the second electrode material layer

[0099] In this step, on the side of the first electrode material layer away from the current collector, a third slurry and a fourth slurry are alternately applied along the length of the current collector to form a second electrode material layer including at least one third active material particle region and at least one fourth active material particle region. The third slurry contains third active material particles, and the fourth slurry contains fourth active material particles.

[0100] In this application, the method of applying the slurry is not strictly limited; the electrode material layer can be formed by coating, 3D printing, or honeycomb structures, etc. For example, Figure 5 The diagram illustrates a first device filled with a first layer of slurry for forming a first electrode material layer and a second device filled with a second layer of slurry for forming a second electrode material layer. Each device contains multiple partitioned tanks sequentially and alternately filled with slurries of different active particles. Each partitioned tank has a discharge port at its bottom, which controls the extrusion of slurry from the partitioned tank. The first electrode material layer can be completely formed and dried before forming the second electrode material layer; alternatively, the second filler layer can be applied to the dried layer while a portion of the first electrode material layer is being formed, thereby simultaneously forming the first and second electrode material layers and improving production efficiency. Figure 5 In this context, "no material output" indicates that the separator is filled with slurry, and the outlet is not opened during coating; "no material output" indicates that no slurry is filled. This allows the separators for large and small particles in the first and second devices to be staggered, thus separating large and small particles in the particle column. "No material output" and "slurry output" can be interchanged, or one or both of these separators can be removed, as long as the surface of the current collector corresponding to that area is not coated with slurry.

[0101] A third aspect of this application discloses an electrochemical device, which includes the electrode sheet of the first aspect of this application.

[0102] The electrochemical device of this application can include any device in which an electrochemical reaction occurs, and specific examples include, but are not limited to, primary batteries, secondary batteries, and capacitors. Optionally, the above-mentioned electrochemical device can be a lithium-ion secondary battery.

[0103] In some embodiments of this application, the lithium-ion secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During battery charging and discharging, active lithium ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor of ions between the positive and negative electrode. The separator, disposed between the positive and negative electrode, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0104] This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected. In some embodiments of this application, the material of the separator membrane may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, or polyvinylidene fluoride.

[0105] This application does not impose any particular restrictions on the type of electrolyte. Exemplarily, the electrolyte solvent may be two or more of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC); and the electrolyte may be one or more of lithium hexafluorophosphate / sodium (Li / NaPF6), lithium perchlorate / sodium (Li / NaClO4), and lithium trifluorosulfonate / sodium (Li / NaFSI).

[0106] The lithium-ion battery of this application may be in the form of a battery cell, a battery module, or a battery pack. In some embodiments, battery cells may be assembled into a battery module, and the number of battery cells contained in a battery module may be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, and the number of battery modules contained in a battery pack may be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0107] The fourth aspect of this application discloses an electrical device, which includes the electrochemical device described in the third aspect of this application.

[0108] Battery cells, battery modules, and battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices can include, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0109] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0110] As one example, the electrical device can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery for this electrical device, a battery pack or battery module can be used.

[0111] Another example of the device could be a mobile phone, tablet computer, laptop computer, etc. This device typically requires a slim and lightweight design and can use a single battery cell as its power source.

[0112] It should be noted that the features and advantages described above for the electrode sheet of the first aspect of this application also apply to the method for preparing the electrode sheet of the second aspect of this application, the electrochemical device of the third aspect, and the electrical equipment of the fourth aspect, and will not be repeated here.

[0113] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of 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 the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0114] Example 1

[0115] 1. Preparation of the positive electrode sheet

[0116] (1) Provide aluminum foil, large-particle LFP (LiFePO4) and small-particle LFP (LiFePO4), wherein the average particle size of the large-particle LFP is d1=0.6μm and the average particle size of the small-particle LFP is d2=0.4μm.

[0117] (2) Mix 95% LPF, 2% carbon black and 3% PVDF evenly to obtain a large particle slurry. Prepare a small particle slurry by mixing small LPF particles in the same way.

[0118] (3) Coating is performed on one side of the aluminum foil using a 3D printer. See details. Figure 5 In the first layer of filler, the separator grooves are filled with alternating large and small particle slurry, starting from the first strip, with the last strip left unfilled. In the second layer of filler, the separator grooves are filled with alternating large and small particle slurry, starting from the first strip. The coating width for large particles is w1 = 80 μm, and the coating width for small particles is w2 = 10 μm.

[0119] First, a first layer of filler is applied, forming the first electrode material layer. The initial strip from the left consists of large particles, and the material layer thickness is 100 μm. The doping amount of small particles is 10%, and the maximum compaction density of the large and small particles is 2.65 g / cm³. 3 and 2.35g / cm 3 .

[0120] After the first electrode material layer loses its fluidity, the second electrode material layer is printed on its surface. The first strip from the left does not discharge material. Starting from the second strip, small and large particle slurries are alternately filled, with the small particle slurry filling positions corresponding to the large particle areas in the first electrode material layer, and the large particle slurry filling positions corresponding to the small particle areas in the first electrode material layer, to form the second electrode material layer. The material layer thickness is 100 μm, the small particle doping amount is 10%, and the maximum powder compaction density of the large and small particles is 2.65 g / cm³, respectively. 3 and 2.35g / cm 3Note: The maximum compacted powder density is determined by holding the particles under a pressure of 200 MPa for 10 seconds, according to the method in GB / T 1479.1 2011.

[0121] Finally, the positive electrode sheet is obtained by baking and rolling.

[0122] 2. Preparation of the negative electrode sheet

[0123] A negative electrode slurry is obtained by uniformly mixing graphite, carbon black (2%), and PVDF (3%). The negative electrode slurry is coated onto the surface of copper foil, dried, and rolled to obtain the negative electrode.

[0124] 3. Assemble the positive electrode, negative electrode, separator (Celgard 2300 microporous membrane), and electrolyte (containing 1.0 mol / L LiPF6, with a solvent of ethylene carbonate (EC): dimethyl carbonate (DMC) in a volume ratio of 1:1) into a soft-pack battery E1 with a designed capacity of 1.8 Ah.

[0125] The differences between Examples 2-6 and Example 1 are shown in Table 1. By setting one of the large particle coating width W1 and the small particle coating width W2, the average particle size d1 of the large LFP particles, the average particle size d2 of the small LFP particles, and the small particle doping amount x, the maximum powder compaction density ρ1 of the large particles and the maximum powder compaction density ρ2 of the small particles were measured. The other of the large particle coating width W1 and the small particle coating width W2 was calculated according to w1 = n1d1 and w2 = n2d2 = n1d1ρ1x / (ρ2(1-x)). Specifically,

[0126] The difference between Example 2 and Example 1 is that the average particle size of the large particles is d1 = 0.6 μm, the average particle size of the small particles is d2 = 0.4 μm, the doping amount of the small particles is 50%, the coating width of the small particles is W2 = 10 μm, the maximum powder compaction density ρ1 of the large particles and the maximum powder compaction density ρ2 of the small particles are measured, and the coating width W1 of the large particles is calculated to be 80 μm. A soft-pack battery E2 is obtained.

[0127] The difference between Example 3 and Example 1 is that the average particle size of the large particles is d1 = 0.6 μm, the average particle size of the small particles is d2 = 0.25 μm, the doping amount of the small particles is 10%, the coating width of the small particles is W2 = 10 μm, the maximum powder compaction density ρ1 of the large particles and the maximum powder compaction density ρ2 of the small particles are measured, and the coating width of the large particles is calculated to be 10 μm. A soft-pack battery E3 is obtained.

[0128] The difference between Example 4 and Example 1 is that the average particle size of the large particles is d1 = 1.6 μm, the average particle size of the small particles is d2 = 0.4 μm, the doping amount of the small particles is 10%, the coating width of the small particles is W2 = 10 μm, the maximum powder compaction density ρ1 of the large particles and the maximum powder compaction density ρ2 of the small particles are measured, and the coating width of the large particles is calculated to be 10 μm. A soft-pack battery E4 is obtained.

[0129] The difference between Example 5 and Example 1 is that the average particle size of the large particles is d1 = 0.3 μm, the average particle size of the small particles is d2 = 0.25 μm, the doping amount of the small particles is 10%, the coating width of the small particles is W2 = 10 μm, the maximum powder compaction density ρ1 of the large particles and the maximum powder compaction density ρ2 of the small particles are measured, and the coating width W1 of the large particles is calculated to be 90 μm. A soft-pack battery E5 is obtained.

[0130] The difference between Example 6 and Example 1 is that the average particle size of the large particles is d1 = 0.6 μm, the average particle size of the small particles is d2 = 0.4 μm, the doping amount of the small particles is 70%, the coating width W1 of the large particles is 10 μm, the maximum powder compaction density ρ1 of the large particles and the maximum powder compaction density ρ2 of the small particles are measured, and the coating width W2 of the small particles is calculated to be 25 μm. A soft-pack battery E6 is obtained.

[0131] Comparative Example 1

[0132] The only difference between this comparative example and Example 1 is that the preparation steps of the positive electrode sheet are as follows:

[0133] 1. Provide aluminum foil, large particle LFP and small particle LFP, wherein the average particle size of large particle LFP is d1=0.6μm and the average particle size of small particle LFP is d2=0.4μm.

[0134] 2. Mix 95% LFP particles (10% doping with small LFP particles), 2% conductive carbon black, and 3% PVDF evenly to obtain an active particle slurry.

[0135] 3. Apply an active particle slurry to one side of the aluminum foil, and then bake and roll it to obtain a positive electrode sheet.

[0136] Comparative Example 2

[0137] The only difference between this comparative example and Example 1 is that the preparation steps of the positive electrode sheet are as follows:

[0138] 1. Provide aluminum foil, large particle LFP and small particle LFP, wherein the average particle size of large particle LFP is d1=0.6μm and the average particle size of small particle LFP is d2=0.4μm.

[0139] 2. Mix 95% LFP particles (50% doping with small LFP particles), 2% conductive carbon black, and 3% PVDF evenly to obtain an active particle slurry.

[0140] 3. Apply an active particle slurry to one side of the aluminum foil, and then bake and roll it to obtain a positive electrode sheet.

[0141] Comparative Example 3

[0142] The only difference between this comparative example and Example 1 is that the preparation steps of the positive electrode sheet are as follows:

[0143] 1. Provide aluminum foil, large particle LFP and small particle LFP, wherein the average particle size of large particle LFP is d1=0.6μm and the average particle size of small particle LFP is d2=0.25μm.

[0144] 2. Mix 95% LFP particles (10% doping with small LFP particles), 2% conductive carbon black, and 3% PVDF evenly to obtain an active particle slurry.

[0145] 3. Apply an active particle slurry to one side of the aluminum foil, and then bake and roll it to obtain a positive electrode sheet.

[0146] Comparative Example 4

[0147] The only difference between this comparative example and Example 1 is that in step 1(3), after the first electrode material layer loses its fluidity, the second electrode material layer is printed on the surface of the first electrode material layer. The first strip from the left is blank, and starting from the second strip, small particle slurry and large particle slurry are alternately filled in sequence. The position of filling the small particle slurry corresponds to the small particle area in the first electrode material layer, and the position of filling the large particle slurry corresponds to the large particle area in the first electrode material layer, so as to form the second electrode material layer. Thus, the prepared electrode sheet includes two particle columns arranged along the length direction of the current collector, which are a particle column consisting entirely of large particles and a particle column consisting entirely of small particles.

[0148] Test case

[0149] In this test example, the electrode sheet compaction density of Examples 1-6 and Comparative Examples 1-4 and the DC internal resistance of the battery under different temperature conditions were tested respectively. The test methods are as follows:

[0150] Electrode sheet compaction density: Samples were taken from three random locations on the electrode sheet using a 1.5mm diameter circular cutter, and the thickness was measured with a micrometer and the weight was weighed with an electronic balance to calculate the compaction density of the electrode sheet.

[0151] The battery was discharged to 2.0V at 1 / 3C constant current at room temperature, and then charged to 50% SOC at 1 / 3C constant current. It was then discharged at 1.5C constant current for 30s at 25℃ and -10℃ respectively. The voltages before and after discharge were recorded. The discharge DCIR (mΩ) was calculated as: (voltage before discharge - voltage after discharge) / discharge current * 1000.

[0152] The results are shown in Table 1. The overall performance of batteries E1-E6 is better than that of batteries C1-C4. As can be seen from batteries E1 and C1, and E2 and C2, compared with the method of non-partitioning of large and small particles, the battery prepared by the large and small particle stacking method of this application can improve the mass transfer capacity of the electrode sheet, reduce the internal resistance, and improve the kinetic performance.

[0153] In battery C3, the average particle size of large particles d1 and small particles d2 satisfies d1×(√2-1)=d2. This ratio results in the maximum compaction density, which, while maximizing the volumetric energy density, leads to a significant decrease in mass transfer performance, manifested as a substantial increase in internal resistance and poor kinetic performance. Compared to battery C3, battery E3 employs the particle size distribution method described in this application. Although the compaction density is slightly lower, it significantly improves mass transfer capacity, resulting in a substantial reduction in internal resistance and a marked improvement in kinetic performance.

[0154] Compared to C2, E2 shows a greater reduction in internal resistance than C2, indicating that increasing the doping amount of small particles brings more significant advantages to this application. The mass transfer capacity of the battery is improved more significantly, the internal resistance is reduced more greatly, and the kinetic benefits are higher.

[0155] Compared to battery E1, battery E3 has a slightly higher average particle size ratio of large to small particles, which is beneficial to improving mass transfer capacity, resulting in a reduction in internal resistance and an increase in compaction density.

[0156] Compared to battery E4, battery E4 has a higher average particle size of large particles, resulting in a higher ratio of large to small average particle size, which hinders mass transfer and leads to higher internal resistance of the battery.

[0157] Compared to batteries E3, batteries E5 have a lower average particle size for large particles, resulting in a lower ratio of large to small average particle size. This also hinders mass transfer and leads to a higher internal resistance in the battery.

[0158] Compared to E1, battery E6 has a higher content of small particle doping, which reduces mass transfer capacity and results in higher internal resistance.

[0159] Table 1. DC internal resistance of different batteries under different temperature conditions

[0160]

[0161] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An electrode sheet, characterized in that, include: current collector; A first electrode material layer is disposed on at least one side of the current collector; The second electrode material layer is disposed on the side of the first electrode material layer away from the current collector; The first electrode material layer includes a plurality of first particle regions, each of which includes at least one first active material particle region and at least one second active material particle region. The first and second active material particle regions are arranged alternately along the length direction of the current collector. The first active material particle region contains first active material particles, and the second active material particle region contains second active material particles. The average particle size of the first active material particles is greater than the average particle size of the second active material particles. The second electrode material layer includes a plurality of second particle regions, each of which includes at least one third active material particle region and at least one fourth active material particle region. The third active material particle region and the fourth active material particle region are arranged alternately along the length direction of the current collector. The third active material particle region contains third active material particles, and the fourth active material particle region contains fourth active material particles. The average particle size of the third active material particles is greater than the average particle size of the fourth active material particles. The electrode sheet includes at least one column of particles arranged along the length direction of the current collector. The column of particles includes at least one of the first active material particle region and the second active material particle region on the first electrode material layer, and at least one of the third active material particle region and the fourth active material particle region on the second electrode material layer. Each of the particle columns contains the first active material particle region and / or the third active material particle region.

2. The electrode sheet according to claim 1, characterized in that, The particle array includes the first or second active material particle region on the first electrode material layer and the third or fourth active material particle region on the second electrode material layer.

3. The electrode sheet according to claim 1 or 2, characterized in that, The particle column contains the first active material particle region and the fourth active material particle region; or, the particle column contains the second active material particle region and the third active material particle region. And / or, the average particle size of the third active material particles is greater than the average particle size of the second active material particles.

4. The electrode sheet according to claim 1, characterized in that, The ratio of the average particle size of the first active material particle to that of the second active material particle is (1.1–4):1; And / or, the average particle size ratio of the third active material particles to the fourth active material particles is (1.1 to 4):1; And / or, the ratio of the average particle size of the first active material particles to that of the fourth active material particles is (1.1 to 4):1; And / or, the ratio of the average particle size of the third active material particles to that of the second active material particles is (1.1 to 4):1; And / or, the average particle size of the first active material particles and the third active material particles are independently 0.2 μm to 3.2 μm; And / or, the average particle size of the second active material particles and the fourth active material particles are independently 0.05 μm to 0.8 μm.

5. The electrode sheet according to claim 1, characterized in that, The ratio of the average particle size of the first active material particle to that of the second active material particle is (2.2–2.6):1; And / or, the average particle size ratio of the third active material particles to the fourth active material particles is (2.2~2.6):1; And / or, the average particle size of the first active material particles and the third active material particles are independently 0.4 μm to 0.8 μm; And / or, the average particle size of the second active material particles and the fourth active material particles are independently 0.15 μm to 0.4 μm.

6. The electrode sheet according to claim 1, characterized in that, The number of the second active material particles accounts for 1% to 60% of the total number of the first and second active material particles in the first electrode material layer; And / or, the number of the fourth active material particles accounts for 1% to 60% of the total number of the third and fourth active material particles in the second electrode material layer.

7. The electrode sheet according to claim 1, characterized in that, Along the length direction of the current collector, the width of the second active material particle region is greater than the width of the fourth active material particle region; And / or, along the length direction of the current collector, the width of the first active material particle region and the third active material particle region are each independently 10 μm to 100 μm; And / or, along the length direction of the current collector, the widths of the second active material particle region and the fourth active material particle region are each independently 1 μm to 20 μm.

8. The electrode sheet according to claim 1, characterized in that, The maximum powder compaction density of the first and third active material particles is independently 2.4 g / cm³. 3 ~2.8g / cm 3 ; And / or, the maximum powder compaction density of the second active material particles and the fourth active material particles is independently 2.1 g / cm³. 3 ~2.5g / cm 3 ; And / or, the compaction density of the electrode sheet is 2.5 g / cm³. 3 ~2.7g / cm 3 .

9. The electrode sheet according to claim 1, characterized in that, The first active material particle, the second active material particle, the third active material particle, and the fourth active material particle are selected from positive electrode active materials, wherein the positive electrode active materials include one or more of lithium transition metal oxides, lithium-containing phosphates, sodium transition metal oxides, and sodium-containing phosphates. Alternatively, the first active material particle, the second active material particle, the third active material particle, and the fourth active material particle are selected from one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide ternary materials, lithium nickel cobalt aluminum oxide ternary materials, lithium manganese oxide, and lithium cobalt oxide.

10. The electrode sheet according to claim 1, characterized in that, The first active material particle, the second active material particle, the third active material particle, and the fourth active material particle are selected from negative electrode active materials, which include one or more of graphite, silicon, and lithium titanate.

11. The electrode sheet according to claim 1, characterized in that, The thickness of the first electrode material layer and the second electrode material layer are each independently 80 μm to 120 μm.

12. A method for preparing the electrode sheet according to any one of claims 1 to 11, characterized in that, include: On at least one side of the current collector, a first slurry and a second slurry are alternately applied along the length direction of the current collector to form a first electrode material layer comprising at least one first active material particle region and at least one second active material particle region, wherein the first slurry contains first active material particles and the second slurry contains second active material particles. On the side of the first electrode material layer away from the current collector, a third slurry and a fourth slurry are alternately applied along the length direction of the current collector to form a second electrode material layer including at least one region of the third active material particles and at least one region of the fourth active material particles. The third slurry contains third active material particles, and the fourth slurry contains fourth active material particles.

13. An electrochemical device, characterized in that, Includes the electrode sheet as described in any one of claims 1 to 11.

14. An electrical appliance, characterized in that, Includes the electrochemical device as described in claim 13.

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