Electrode sheet and preparation method therefor, battery, and electric device

Abstract

The present application relates to an electrode sheet and a preparation method therefor, a battery, and an electric device. The electrode sheet comprises a current collector and a coating arranged on at least one side of the current collector, the coating is provided with a pore channels, and the pore channels are located in the coating and pass through the surface of the coating. The pore channels are formed in the coating, the bottoms of the pore channels are located within the coating, the pore channels pass through the surface of the coating to obtain liquid phase diffusion channels and form a liquid phase pathway, so that the ion diffusion distance is shortened, thereby mitigating ion concentration polarization, and helping to improve the power performance of battery cells.

Description

Electrode sheet and preparation method thereof, battery and electrical device

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202410155108.1 filed on February 2, 2024, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to an electrode plate and a preparation method thereof, a battery and an electrical device. Background Art

[0004] Secondary batteries have been widely used in various consumer electronic products and electric vehicles due to their advantages such as high energy density, high output voltage, good safety, no pollution and no memory effect.

[0005] As the penetration rate of new energy vehicles continues to rise, hybrid and extended-range vehicles are gradually entering the market, placing higher demands on battery power performance. Summary of the Invention

[0006] The main purpose of this application is to provide an electrode plate to improve the performance of the battery.

[0007] To achieve the above-mentioned purpose, the present application proposes an electrode plate, which includes a current collector and a coating provided on at least one side of the current collector, the coating being provided with a pore, the bottom of the pore of the pore being located in the coating, and the pore passing through the surface of the coating.

[0008] The power density of a battery cell is primarily affected by liquid-phase concentration polarization. During the discharge process, this influence generates a large overpotential, leading to insufficient power density. To improve battery performance, pores are incorporated into the coating. The pores, with their bottoms located within the coating, penetrate the surface of the coating, creating liquid-phase diffusion channels and forming liquid-phase pathways. This shortens the distance for ion diffusion, thereby reducing ion concentration polarization and contributing to improved battery cell power performance.

[0009] Furthermore, the bottom of the pores is located within the coating.

[0010] The bottom of the pores is located within the coating, indicating that the current collector is covered by the coating, preventing the current collector from being directly exposed to the electrolyte, reducing the erosion of the electrolyte on the current collector, and at the same time allowing the coating to cover the surface of the current collector, increasing the contact area between the active material and the current collector, improving the electron transmission efficiency, and the volume energy density of the battery.

[0011] Optionally, the aperture of the pore is in an expanding shape that gradually expands toward the coating surface.

[0012] The flared shape refers to the gradual increase in pore diameter from the bottom of the pore to the opening on the coating surface, forming a trumpet-like shape. This shape results in smaller pores as the coating approaches the current collector, providing the coating with a certain degree of mechanical strength and maintaining its original shape during the subsequent electrode cold pressing process. Furthermore, the pores opening at their largest on the coating surface facilitate rapid diffusion of electrolyte into the pores, improving the efficiency of liquid-phase mass transfer.

[0013] Optionally, the maximum pore size d1 of the pores on the surface of the coating satisfies 5 μm to 300 μm.

[0014] It can be understood that the channels in this application can be regular or irregular in shape. For example, the bottom of the channel or the shape of the channel on the coating surface can be circular, elliptical, or other irregular shapes. In order to facilitate the description of the size of the channel pore size, the maximum pore size at the bottom of the channel and the maximum pore size of the channel on the coating surface are used to describe it.

[0015] The maximum pore diameter d2 at the bottom of the pore is smaller than the maximum pore diameter d1 of the pore on the coating surface, so that the pore diameter is expanded gradually toward the coating surface.

[0016] The test steps for the maximum pore diameter d1 of the pores on the coating surface are as follows: take a picture of the electrode through the CCD of an optical microscope, identify the area of ​​the pores, and then use the area to calculate the equivalent radius.

[0017] The maximum pore size d1 of the pores on the coating surface falls within the above range, which can increase the liquid phase diffusion rate and further reduce ion concentration polarization. It is understandable that pore sizes smaller than 5 μm result in poor diffusion rate, while pore sizes greater than 500 μm result in a significant loss in volumetric energy density.

[0018] Optionally, the surface area of ​​the coating is defined as A, and the opening area of ​​the pores on the surface of the coating is defined as a, and the following condition is satisfied: 1%≤a / A×100%≤10%.

[0019] It can be understood that the porosity in the coating is within a certain range and can provide abundant liquid phase pathways. In this application, the surface area of ​​the coating is defined as A, and the opening area of ​​the pores on the coating surface is defined as a, which satisfies the above relationship. This helps to obtain more liquid phase diffusion channels, form liquid phase pathways, shorten the distance of ion diffusion, and thus weaken the concentration polarization behavior of the ions, which helps to improve the power performance of the battery cell.

[0020] Optionally, the coating includes at least two sub-coating layers, the at least two sub-coating layers include a first sub-coating layer and a second sub-coating layer, the first sub-coating layer is disposed on the current collector, and the second sub-coating layer is disposed on a side of the first sub-coating layer away from the current collector;

[0021] The pores are located in the second sub-coating layer and penetrate the surface of the second sub-coating layer.

[0022] The coating of the present application includes at least two sub-coatings, and the at least two sub-coatings include a first sub-coating and a second sub-coating. The first sub-coating is arranged on the current collector, and the second sub-coating is arranged on the side of the first sub-coating away from the current collector, so that the surface of the second sub-coating is exposed to the electrolyte, and the pores are located in the second sub-coating and penetrate the surface of the second sub-coating. In this way, the pores are only in the second sub-coating, so that the first sub-coating completely covers the current collector, avoiding direct exposure of the current collector to the electrolyte, reducing the erosion of the electrolyte on the current collector, and at the same time, the first sub-coating covers the surface of the current collector, thereby increasing the contact area between the active material and the current collector, improving the electron transmission efficiency, and the volume energy density of the battery.

[0023] Optionally, the thickness D1 of the first sub-coating layer is less than or equal to the thickness D2 of the second sub-coating layer.

[0024] Optionally, D1 and D2 satisfy 3 <D2 / D1<10;

[0025] And / or, the D1 satisfies 30 μm <D1<150μm;

[0026] And / or, the D2 satisfies 570 μm <D2<450μm。

[0027] It is understood that when the thickness D1 of the first sub-coating is less than or equal to the thickness D2 of the second sub-coating, and the pores are located in the second sub-coating, when D1 is less than or equal to D2, the pores have a certain depth in the coating, shortening the distance for ion diffusion, thereby weakening the ion concentration polarization behavior, and helping to improve the power performance of the battery cell. It is also understood that when D1>D2, the pore depth is insufficient and the pore creation effect is poor.

[0028] Optionally, the primary particle size Dv50 of the active material in the first sub-coating layer and the second sub-coating layer is 100 nm to 1000 nm.

[0029] Optionally, the active material in the coating layer includes lithium iron phosphate.

[0030] By including active materials with smaller particle sizes in the first and second sub-coatings, the solid phase expansion inside the particles can be improved. Combined with the improvement effect of the liquid phase concentration difference in the electrode pore formation, the power capacity of the electrode can be further improved.

[0031] It's understandable that when liquid-phase concentration polarization is improved, the bottleneck of the reaction shifts from concentration polarization to solid-phase diffusion polarization within the active particles. Small particles of active material have a larger specific surface area, more reaction sites, and a smaller particle size, resulting in a shorter diffusion distance. Therefore, combined with the pore-forming effect, the power capability of the electrode can be further improved.

[0032] Optionally, a primer layer is provided between the current collector and the coating layer.

[0033] In order to improve the adhesion between the coating and the current collector, a primer layer is provided between the current collector and the coating.

[0034] The active material in the coating includes but is not limited to lithium iron phosphate. It is understood that when the active material includes lithium iron phosphate, the battery performance effect is relatively good.

[0035] Optionally, the present application also provides a method for preparing an electrode plate, comprising the following steps:

[0036] preparing a coating slurry, wherein the coating slurry comprises a first sub-coating slurry and a second sub-coating slurry;

[0037] coating the first sub-coating slurry on at least one side of the current collector and drying the slurry to form a first sub-coating on the current collector;

[0038] A second sub-coating slurry is coated on the side of the first sub-coating away from the current collector, so that the second sub-coating slurry covers the first sub-coating, and pores are formed in situ in the second sub-coating, and then dried to obtain an electrode plate.

[0039] It can be understood that the second sub-coating slurry and the surface of the first coating are similar to the principle of dewdrops forming on the surface of a lotus leaf, forming a surface tension difference, forming channels in situ in the second sub-coating, and drying to obtain electrode plates.

[0040] The electrode plate preparation method proposed in this application is achieved by applying a first sub-coating slurry to the current collector and, after drying, applying a second sub-coating slurry. When the active material in the second sub-coating slurry is applied to the first sub-coating, a surface tension difference is created between the second sub-coating slurry and the first coating surface, similar to the formation of dewdrops on a lotus leaf. This creates an in-situ trumpet-shaped pore with a mechanical geometry that has a large pore size at the coating surface and a small pore size at the bottom. This gives the coating a certain mechanical strength and allows it to maintain its original shape during the subsequent cold pressing process of the electrode plate.

[0041] Therefore, this preparation method facilitates the preservation of the electrode pore structure. Furthermore, the pores are generated in situ during the slurry coating process, resulting in relatively good structural consistency. This has no impact on the efficiency of the electrode production process, does not require additional production equipment, and does not affect the production cycle of the battery cell. The preparation method of this application is simple and easy to operate, suitable for large-scale production, and has the advantages of good consistency, low cost, and high production speed.

[0042] Compared with other preparation methods using laser pore forming, the preparation method of the present application has a trumpet-shaped channel, the structure of the coating has good mechanical strength, and the structure of the coating and the channel will not be damaged during the cold pressing process. In addition, laser pore forming requires cutting off the coating material, which wastes material, generates metal debris, ablates active materials, and increases costs. Compared with other materials using pore-forming agents, pore formation is achieved through the consumption of the pore-forming agent, and the pore-forming agent is difficult to completely remove in the subsequent electrode drying process, requiring the addition of new materials. Moreover, the pore-forming agent, as a consumable, does not contribute to the improvement of battery performance, and adds new steps, which increases labor intensity and production cycle. The preparation method of the present application does not require the use of related consumables.

[0043] Optionally, the viscosity P of the second sub-coating slurry ranges from 1000 mPa·s to 8000 mPa·s.

[0044] In order to achieve a surface tension pore-forming method similar to dewdrops on the surface of a lotus leaf, during the process of coating the second sub-coating slurry on the surface of the first sub-coating, the viscosity of the slurry is required to be flexibly adjusted, so as to ultimately achieve a wetting state between the slurry and the electrode surface.

[0045] Optionally, the contact angle of the second sub-coating slurry on the surface of the first sub-coating is in the range of 15° to 60°.

[0046] The contact angle is a quantitative measure of surface wettability and is represented by the angle between the liquid interface and the solid surface.

[0047] The test steps for the contact angle of the second sub-coating slurry on the surface of the first sub-coating are to drop a drop of slurry used for the second sub-coating on the surface of the electrode, capture the image of the two when they are in contact through a high-speed CCD, draw the tangent line extending from the contact point of the slurry and the electrode to the surface of the slurry, and calculate the angle between the common tangent line and the horizontal plane, which is the contact angle.

[0048] It is understandable that when the contact angle satisfies the above range, a principle similar to lotus leaf pore formation can be realized, and pores can be formed in situ on the electrode surface.

[0049] Optionally, the present application further provides a battery, comprising the electrode plate as described above;

[0050] Alternatively, the battery includes an electrode plate obtained by the electrode plate preparation method as described above.

[0051] Optionally, the present application also provides an electrical device, which includes the battery as described above.

[0052] The electrode plate in this application includes a current collector and a coating disposed on at least one side of the current collector. The coating is provided with pores, the bottom of the pores of the pores being located within the coating and the pores penetrating the surface of the coating. The pores are provided in the coating, are located within the coating, and penetrate the surface of the coating, thereby forming liquid-phase diffusion channels and liquid-phase pathways, shortening the distance for ion diffusion, thereby reducing ion concentration polarization behavior, and contributing to improved power performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order 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 use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0054] FIG1 is a schematic structural diagram of an electrode plate according to an embodiment of the present application;

[0055] FIG2 is a schematic diagram of the cross-sectional structure of an electrode plate according to an embodiment of the present application;

[0056] FIG3 is a schematic cross-sectional view of an electrode sheet according to another embodiment of the present application;

[0057] FIG4 is a schematic flow chart of a method for preparing an electrode sheet according to an embodiment of the present application;

[0058] FIG5 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0059] FIG6 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG5 ;

[0060] FIG7 is a schematic diagram of a battery module according to an embodiment of the present application;

[0061] FIG8 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0062] FIG9 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG8 ;

[0063] FIG. 10 is a schematic diagram of an electrical device using a battery cell as a power source according to an embodiment of the present application.

[0064] Description of Figure Numbers:

[0065] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of 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.

[0067] Below, the electrode plate and its preparation method, battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0068] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0069] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0070] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0071] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0072] Secondary batteries have been widely used in various consumer electronic products and electric vehicles due to their advantages such as high energy density, high output voltage, good safety, no pollution and no memory effect.

[0073] As the penetration rate of new energy vehicles continues to rise, hybrid and extended-range vehicles are gradually entering the market, placing higher demands on battery power performance.

[0074] The power density of a battery cell is primarily affected by liquid phase concentration polarization. During the discharge process, the porous electrode concentration polarization generates a large overpotential, resulting in insufficient power density. This application proposes an electrode plate comprising a current collector and a coating disposed on at least one side of the current collector. The coating is provided with pores, the bottom of which is located within the coating, and the pores extend through the surface of the coating.

[0075] The electrode plates include positive and negative plates. The positive plates include a current collector and a cathode material disposed on the current collector. The negative plates include a current collector and an anode material disposed on the current collector.

[0076] It can be understood that the electrode plate of the present application can be a positive electrode plate or a negative electrode plate.

[0077] A current collector is a structure or component that collects current. For example, in lithium-ion batteries, this primarily refers to metal foil, such as copper or aluminum foil. The current collector serves as a substrate for the positive or negative active material, collecting the current generated by the active material and delivering a high current output. Typically, aluminum foil is used as the positive current collector, while copper foil is used for the negative current collector.

[0078] The coating refers to a layered structure disposed on the current collector, and the coating includes active substances.

[0079] The pores, as shown in FIG2 , have an open pore structure with a certain depth.

[0080] In order to improve the performance of the battery, the electrode plate 100 shown in Figures 1 to 3 is provided with a channel 30 in the coating 20, and the bottom 31 of the channel 30 is located in the coating 20. The channel 30 penetrates the surface of the coating 20 to obtain a liquid phase diffusion channel, forming a liquid phase passage, shortening the diffusion distance of the ions, and thereby weakening the concentration polarization behavior of the ions, which helps to improve the power performance of the battery cell.

[0081] As shown in Figure 3, the bottom 31 of the pore 30 is located in the coating 20, indicating that the bottom 31 of the pore does not contact the current collector 10. The current collector 10 is covered by the coating 20, which prevents the current collector 10 from being directly exposed to the electrolyte, reduces the corrosion of the electrolyte on the current collector, and at the same time allows the coating to cover the surface of the current collector, thereby increasing the contact area between the active material and the current collector, improving the electron transmission efficiency, and the volume energy density of the battery.

[0082] In one embodiment, the aperture of the pores is in an expanding shape that gradually expands toward the coating surface.

[0083] As shown in Figure 3, the flared shape refers to the gradual increase in pore size from the bottom of the pore to the opening on the coating surface, forming a trumpet-like shape. This shape results in smaller pores as the coating approaches the current collector, providing the coating with a certain degree of mechanical strength and maintaining its original shape during the subsequent electrode cold pressing process. Furthermore, the pores opening at their largest on the coating surface facilitate rapid diffusion of electrolyte into the pores, improving the efficiency of liquid-phase mass transfer.

[0084] In one embodiment, the maximum pore diameter d2 of the bottom of the pore channel is smaller than the maximum pore diameter d1 of the pore channel on the coating surface; the maximum pore diameter d1 of the pore channel on the coating surface satisfies 5 μm to 300 μm.

[0085] It can be understood that the channels in this application can be regular or irregular in shape. For example, the bottom of the channel or the shape of the channel on the coating surface can be circular, elliptical, or other irregular shapes. In order to facilitate the description of the size of the channel pore size, the maximum pore size at the bottom of the channel and the maximum pore size of the channel on the coating surface are used to describe it.

[0086] The maximum pore diameter d2 at the bottom of the pore is smaller than the maximum pore diameter d1 of the pore on the surface of the coating, so that the pore diameter is expanded gradually toward the surface of the coating.

[0087] The maximum pore diameter d1 of the pores on the coating surface satisfies the above range, which can increase the liquid phase diffusion rate and further weaken the ion concentration polarization.

[0088] The test steps for the maximum pore diameter d1 of the pores on the coating surface are as follows: take a picture of the electrode through the CCD of an optical microscope, identify the area of ​​the pores, and then use the area to calculate the equivalent radius.

[0089] In the above-mentioned 5μm to 300μm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 50μm, 60μm, 80μm, 100μm, 120μm, 150μm, 160μm, 180μm, 200μm, 300μm, 500μm, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0090] In one embodiment, the surface area of ​​the coating is defined as A, and the opening area of ​​the pores on the coating surface is defined as a, and the following condition is satisfied: 1%≤a / A×100%≤10%.

[0091] It can be understood that the porosity in the coating is within a certain range, which can not only provide abundant liquid phase pathways, but also ensure that the electrode has a certain mechanical strength. In this application, the surface area of ​​the coating is defined as A, and the opening area of ​​the pores on the coating surface is a, then the above relationship is satisfied. In this way, it is helpful to obtain more liquid phase diffusion channels, form liquid phase pathways, shorten the distance of ion diffusion, and then weaken the concentration polarization behavior of the ions, which is helpful to improve the power performance of the battery cell.

[0092] In the above 1%≤a / A×100%≤10%, the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., as well as the range values ​​between any two of the above point values.

[0093] In one embodiment, the coating includes at least two sub-coatings, the at least two sub-coatings include a first sub-coating and a second sub-coating, the first sub-coating is arranged on the current collector, and the second sub-coating is arranged on the side of the first sub-coating away from the current collector; the channel is located in the second sub-coating and runs through the surface of the second sub-coating.

[0094] As shown in Figures 2 and 3, the coating of the present application includes at least two layers of sub-coatings, and the at least two layers of sub-coatings include a first sub-coating 21 and a second sub-coating 22. The first sub-coating 21 is arranged on the current collector 10, and the second sub-coating 22 is arranged on the side of the first sub-coating 21 away from the current collector 10, so that the surface of the second sub-coating 22 is exposed to the electrolyte, and the channel 30 is located in the second sub-coating 22 and passes through the surface of the second sub-coating 22. In this way, the channel 30 is only in the second sub-coating 22, so that the first sub-coating 21 completely covers the current collector 10, avoiding direct exposure of the current collector 10 to the electrolyte, reducing the erosion of the electrolyte on the current collector, and at the same time, the first sub-coating covers the surface of the current collector, thereby increasing the contact area between the active material and the current collector, improving the electron transmission efficiency, and the volume energy density of the battery.

[0095] As shown in FIG. 3, a third sub-coating 23 can also be provided between the current collector 10 and the first sub-coating 21.

[0096] In one embodiment, the thickness D1 of the first sub-coating is less than or equal to the thickness D2 of the second sub-coating; in one embodiment, D1 and D2 satisfy 3 < D2 / D1 < 10.

[0097] Further, in one embodiment, D1 satisfies 30 μm < D1 < 150 μm; in one embodiment, D2 satisfies 570 μm < D2 < 450 μm.

[0098] The thickness D1 of the first sub-coating is less than or equal to the thickness D2 of the second sub-coating, and the pore channels are located in the second sub-coating. Thus, the pore channels have a certain depth in the coating, shortening the ion diffusion distance, thereby weakening the ion concentration polarization behavior and contributing to the improvement of the power performance of the battery cell.

[0099] When the thickness D1 of the first sub-coating and the thickness D2 of the second sub-coating satisfy the above range, the cost of manufacturing the electrode can also be reduced.

[0100] In the above 3 < D2 / D1 < 10, the values include the minimum and maximum values of this range, as well as each value between this minimum and maximum value. Specific examples include but are not limited to the point values in the embodiments, as well as 3, 4, 5, 6, 7, 8, 9, 10, etc., and the range values between any two of the above point values.

[0101] In one embodiment, the primary particle size Dv50 of the active material in the first sub-coating and the second sub-coating is 100 nm to 1000 nm; the active material includes lithium iron phosphate.

[0102] Based on the local trumpet-shaped liquid-phase transport channels of the electrode, by using active materials with smaller particle sizes in the coating, the solid-phase diffusion behavior can be improved, and the power capacity of the electrode can be further enhanced.

[0103] It can be understood that the specific surface area of the small-particle active material is large, and there are many reaction sites. There are many reaction sites of the active material close to the current collector, and the generated current can also be collected by the current collector faster, improving the power capacity of the electrode.

[0104] Dv50 is the particle size corresponding to when the cumulative particle size distribution percentage of a sample reaches 50%. Its physical meaning is that 50% of the particles are larger than it, and 50% of the particles are smaller than it. Dv50 is also called the median diameter or median particle size. Dv50 is often used to represent the average particle size of the powder.

[0105] The volume average particle size Dv50 of the active material can be measured by methods well-known in the art. As an example, it can be characterized and tested by scanning electron microscopy.

[0106] In the above-mentioned 100nm to 1000nm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 500nm, 800nm, 1000nm, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0107] Considering that in the process of preparing the electrode plate, the slurry of the first sub-coating is first applied to the current collector, and then the slurry of the second sub-coating is applied after drying, the formation of the pores is achieved after the second sub-coating slurry is applied to the surface of the first sub-coating. The second sub-coating slurry forms tension with the surface of the first layer of slurry, and the pore structure is spontaneously formed in situ in the form of dewdrops on a lotus leaf. In order to achieve tension-driven spontaneous pore formation, the viscosity range of the second sub-coating slurry is controlled in the range of 1000mPa·s-8000mPa·s. The viscosity of the second sub-coating slurry meets the above range, which helps to achieve wetting with the surface of the first sub-coating, thereby spontaneously forming pores.

[0108] In one embodiment, a primer layer is provided between the current collector and the coating layer.

[0109] In order to improve the adhesion between the coating and the current collector, a primer layer is provided between the current collector and the coating.

[0110] The active material in the coating layer includes but is not limited to at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium cobalt oxide.

[0111] In one embodiment, the present application also provides a method for preparing an electrode plate, comprising the following steps: preparing a coating slurry, the coating slurry including a first sub-coating slurry and a second sub-coating slurry; coating the first sub-coating slurry on at least one side of a current collector, drying, and forming a first sub-coating on the current collector; coating the second sub-coating slurry on the side of the first sub-coating facing away from the current collector, so that the second sub-coating slurry covers the first sub-coating, and forming channels in situ in the second sub-coating, and drying to obtain an electrode plate.

[0112] As shown in Figure 4, this is achieved by applying a first sub-coating slurry to the current collector and then applying a second sub-coating slurry after drying. When the active material in the second sub-coating slurry is applied to the first sub-coating, the surface tension difference between the second sub-coating slurry and the first coating is similar to the principle of dewdrops forming on the surface of a lotus leaf, forming a trumpet-shaped channel in situ. This trumpet-shaped channel has a mechanical geometric structure with a large pore size on the coating surface and a small pore size at the bottom of the channel, which gives the coating a certain mechanical strength and can maintain its original shape during the subsequent electrode cold pressing process.

[0113] Therefore, this preparation method facilitates the preservation of the electrode pore structure. Furthermore, the pores are generated in situ during the slurry coating process, resulting in relatively good structural consistency. This has no impact on the efficiency of the electrode production process, does not require additional production equipment, and does not affect the production cycle of the battery cell. The preparation method of this application is simple and easy to operate, suitable for large-scale production, and has the advantages of good consistency, low cost, and high production speed.

[0114] Compared with other preparation methods using laser pore forming, the preparation method of the present application has a trumpet-shaped pore, the coating structure has good mechanical strength, and the coating and pore structure will not be damaged during the cold pressing process. In addition, laser pore forming requires cutting off the coating material, which wastes material and increases cost. Compared with other materials using pore-forming agents, pore formation is achieved through the consumption of pore-forming agents, which requires the addition of new materials. Moreover, the pore-forming agent, as a consumable, does not help improve battery performance, and adds new steps, which increases labor intensity and production cycle. The preparation method of the present application does not require the use of related consumables.

[0115] In one embodiment, the viscosity P of the second sub-coating slurry is 1000 mPa·s to 8000 mPa·s.

[0116] In order to achieve a surface tension pore-forming method similar to dewdrops on the surface of a lotus leaf, during the process of coating the second sub-coating slurry on the surface of the first sub-coating, the viscosity of the slurry is required to be flexibly adjusted, so as to ultimately achieve a wetting state between the slurry and the electrode surface.

[0117] In the above-mentioned 1000mPa·s to 8000mPa·s, the values ​​include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 1000mPa·s, 2000mPa·s, 3000mPa·s, 4000mPa·s, 4500mPa·s, 5000mPa·s, 5500mPa·s, 6000mPa·s, 7000mPa·s, 8000mPa·s, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0118] In one embodiment, the contact angle of the second sub-coating slurry on the surface of the first sub-coating is in a range of 15° to 60°.

[0119] The contact angle is a quantitative measure of surface wettability and is represented by the angle between the liquid interface and the solid surface.

[0120] It is understandable that when the contact angle satisfies the above range, a principle similar to lotus leaf pore formation can be realized, and pores can be formed in situ on the electrode surface.

[0121] In the above-mentioned 15° to 60°, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 15°, 20°, 30°, 40°, 50°, 60°, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0122] In one embodiment, the present application further provides a battery, which includes the electrode plate as described above; or, the battery includes the electrode plate obtained by the preparation method of the electrode plate as described above.

[0123] It is understandable that the battery structure can be one of a winding structure, a laminated structure, and a soft pack structure. In particular, for cylindrical batteries, considering that the cylindrical batteries are wound relatively tightly, the gap between the pole pieces is relatively small, and the injection efficiency is low. Using the pole piece of the present application, the pores help to provide space for the rapid passage and infiltration of the electrolyte, thereby improving the injection efficiency. In addition, considering that the electrolyte climbs to the top of the battery cell, due to the effect of gravity, the electrolyte is difficult to climb to the top of the battery cell. In this way, there will be a phenomenon of insufficient electrolyte infiltration at the top of the battery cell, which will cause the problem of lithium precipitation at the top of the battery cell (taking lithium-ion batteries as an example). Using the pole piece of the present application, the setting of the pores in the coating can reserve space for storing the electrolyte, thereby alleviating the problem of insufficient electrolyte infiltration at the top of the battery cell and the occurrence of lithium precipitation.

[0124] The present application also provides an electrical device, which includes the battery as described above.

[0125] In addition, the battery (secondary battery, battery module, battery pack) and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0126] In one embodiment of the present application, a secondary battery is provided.

[0127] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery's charge and discharge process, active ions are embedded in and released from the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator is located between the positive and negative electrodes, primarily preventing a short circuit between the positive and negative electrodes while allowing ions to pass through. The separator is the separator described above in this application.

[0128] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0129] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0130] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0131] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for cathode materials refer to the initial state of the material, i.e., the state before addition of the materials. When the cathode material is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0132] In the list of positive electrode materials in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0133] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0134] In some embodiments, the positive electrode film layer may further include a conductive agent. For 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.

[0135] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0136] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0137] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0138] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0139] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0140] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0141] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

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

[0143] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0144] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0145] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0146] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0147] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0148] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0149] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0150] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG5 shows a battery cell 5 with a square structure as an example.

[0151] In some embodiments, referring to Figure 6, the outer packaging may include an outer shell 51 and a cover plate 53. The outer shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The outer shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the diaphragm can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0152] In some embodiments, a battery cell pool may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0153] FIG7 shows an example battery module 4. Referring to FIG7 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0154] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0155] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0156] Figures 8 and 9 illustrate an example battery pack 1. Referring to Figures 8 and 9 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0157] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0158] As an electrical device, a battery cell, battery module or battery pack can be selected according to its usage requirements.

[0159] Figure 10 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cells in this device, a battery pack or battery module can be used.

[0160] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0161] Example

[0162] Example 1

[0163] Preparation of primer

[0164] Acetylene black, CMC, PAA, and calcium hydroxide were stirred and evenly mixed in a percentage ratio of 80%, 5%, 5%, and 5% to obtain a primer slurry; the slurry was then evenly coated on a 15 μm aluminum foil current collector by extrusion spraying, and then dried to obtain a primer substrate coated with a primer layer.

[0165] Preparation of positive electrode

[0166] The lithium iron phosphate with Dv50=300nm, acetylene black, and PVDF were stirred and mixed in a percentage ratio of 96%, 2%, and 2%, respectively, with NMP as the solvent and a solid content of 55%, to obtain a first sub-coating slurry; the lithium iron phosphate with Dv50=300nm, acetylene black, and PVDF were stirred and mixed in a percentage ratio of 96%, 2%, and 2%, respectively, with NMP as the solvent and a solid content of 35%, to obtain a second sub-coating slurry with a viscosity of 5000mPa·s; the first sub-coating slurry was first applied to the primer substrate by an extrusion coating machine, and after drying, the second sub-coating slurry was applied to the surface of the first sub-coating to control the total coating weight to be 400mg / 1540.25mm 2 The weight ratio of the second sub-coating layer to the lower layer of the first sub-coating layer is 15%:85%. After drying, cold pressing and slitting, the positive electrode sheet is obtained.

[0167] Preparation of negative electrode sheet

[0168] Artificial graphite, acetylene black, CMC, and SBR were stirred and evenly mixed in a percentage ratio of 95.5%, 1.0%, 1.5%, and 2.0% to obtain a negative electrode slurry; the slurry was then passed through a double-layer extrusion coating head and evenly coated on a 6μm copper foil current collector by extrusion spraying, and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0169] Preparation of electrolyte

[0170] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3 / 7, 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent, and stirred to obtain the electrolyte of Example 1.

[0171] Isolation film

[0172] Polypropylene film is used as the isolation film.

[0173] Battery Assembly

[0174] The positive electrode, negative electrode, electrolyte, and separator were assembled into a square wound battery for testing. Specifically, the positive electrode sheet, separator, and negative electrode sheet prepared in the above steps were stacked in order, with the separator positioned between the positive and negative electrode sheets to separate the positive and negative electrodes. The cells were wound to form a bare battery cell, the tabs welded, and the bare cell placed in an outer package. The prepared electrolyte was injected into the dried cell, which was then packaged, allowed to stand, and slowly formed. The cell was then shaped to produce a lithium-ion battery.

[0175] Example 2 and Example 3

[0176] Based on Example 1, the viscosity of the second sub-coating slurry was adjusted.

[0177] Example 4 and Example 5

[0178] Based on Example 1, the thickness ratio of the first sub-coating layer to the second sub-coating layer is adjusted.

[0179] Example 6 and Example 7

[0180] Based on Example 1, the primary particle size Dv50 of the active material was adjusted.

[0181] Comparative Example 1

[0182] On the basis of Example 1, the preparation method of the positive electrode sheet was adjusted, and lithium iron phosphate with Dv50 = 300nm, acetylene black, and PVDF were stirred and mixed in a ratio of 96%, 2%, and 2%, respectively, with NMP as the solvent and a solid content of 55% to obtain a first sub-coating slurry; the slurry was applied to the primer substrate by an extrusion coater, and the total coating weight was controlled to be 400mg / 1540.25mm 2 After drying, cold pressing and cutting, the positive electrode sheet is obtained.

[0183] Related parameter tests

[0184] To calculate tortuosity: The materials were assembled into symmetrical cells. Each cell was filled with 60 μL of 50 mM tetrabutylammonium perchlorate (TEAC) and EC / DMC (EC:DMC = 1:1, lithium ion conductivity 1.7 mS / cm). Electrochemical impedance spectroscopy (EIS) was measured over a frequency range of 200 kHz to 50 MHz. Tortuosity can be calculated using the formula τ / ε = Rion × S × kint / l. Here, τ is the tortuosity, ε is the porosity, l is the electrode thickness, S is the electrode area, kint is the lithium ion conductivity of the electrolyte, and Rion is the lithium ion impedance. Rion = 3 × (Rh - Rl), where Rh is the high-frequency intercept of the impedance spectrum and Rl is the low-frequency intercept.

[0185] Calculation of average pore diameter: Flatten the cold-pressed positive electrode and place it under a CCD microscope. Use CCD software to identify the actual area S of the pores and use R = (S / π) 0.5 Calculate the average diameter R.

[0186] Calculation of the ratio of the opening area of ​​the pores on the coating surface to the area of ​​the coating surface (pore ratio calculation): Flatten the cold-pressed positive electrode and place it under a CCD microscope. Using a 1mm×1mm range as the statistical interval, count the diameter and number of pores. Assuming the average diameter of the pores is R and the total number is N, the pore ratio is N*π*R 2 / 1mm 2 *100%.

[0187] Viscosity test steps:

[0188] Use a rotational viscometer, inject the sample into a 500ML beaker, insert the rotor, start the instrument, adjust the appropriate rotation speed, and read the viscosity of the current test slurry from the display.

[0189] Electrochemical performance test:

[0190] Room-Temperature Rate Retention: At 25°C, charge the assembled battery at 1 / 3C to 3.8V lithium iron phosphate, let it rest for 30 minutes, and then discharge it at 1 / 3C to 2.0V lithium iron phosphate. Record the discharge capacity at this point as C0. Then, discharge it at 3C to 2.0V lithium iron phosphate. Record the discharge capacity at this point as C1. C1 / C0 is the rate retention rate.

[0191] Room-temperature DCR: At 25°C, charge the assembled battery at 1 / 3C to 3.8V lithium iron phosphate, let it rest for 30 minutes, then discharge it at 1 / 3C to 0.5C0 capacity (50% SOC), let it rest for 30 minutes, and record the voltage at this point as V0. Then discharge it continuously at a 2C discharge rate for 60 seconds, recording the voltages at 60 seconds as V10 and V60. Calculate the 10s and 60s DCR using the following formula: 60s DCR = (V0 - V60) / (2*C0).

[0192] Table 1 Experimental data list

[0193] Table 2 Test results of examples and comparative examples

[0194] As can be seen from the table above, by comparing the examples with the comparative examples, in the examples, the positive electrode sheet of the present application is adopted, and by providing channels in the second sub-coating, the rate performance and 60sDCR performance of the battery in the examples are improved. This indicates that the channels are provided in the coating, the channels are located within the coating, and penetrate the surface of the coating, thereby obtaining liquid phase diffusion channels, forming liquid phase pathways, shortening the distance of ion diffusion, and thereby weakening the concentration polarization behavior of the ions, which helps to improve the power performance of the battery cell.

[0195] The above is only a preferred embodiment of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made based on the contents of the present application specification and drawings, or direct / indirect application in other related technical fields, are included in the patent protection scope of the present application.

Claims

1. An electrode plate, wherein: The electrode plate (100) comprises a current collector (10) and a coating (20) provided on at least one side of the current collector (10); the coating (20) is provided with a pore (30); a bottom (31) of the pore (30) is located in the coating (20); and the pore (30) passes through the surface of the coating (20).

2. The electrode plate according to claim 1, wherein: The aperture of the pore (30) is in an expanding shape that gradually expands toward the surface of the coating (20).

3. The electrode plate according to claim 1 or 2, wherein: The maximum pore size d1 of the pores (30) on the surface of the coating layer satisfies 5 μm to 300 μm.

4. The electrode plate according to any one of claims 1 to 3, wherein: The surface area of the coating (20) is defined as A, and the opening area of the pores (30) on the surface of the coating is defined as a, and the following conditions are satisfied: 1%≤a / A×100%≤10%.

5. The electrode plate according to any one of claims 1 to 4, wherein: The coating (20) comprises at least two sub-coating layers, wherein the at least two sub-coating layers comprise a first sub-coating layer (21) and a second sub-coating layer (22), wherein the first sub-coating layer (21) is disposed on the current collector (10), and the second sub-coating layer (22) is disposed on a side of the first sub-coating layer (21) facing away from the current collector (10); The pores (30) are located in the second sub-coating (22) and penetrate the surface of the second sub-coating (22).

6. The electrode plate according to claim 5, wherein: The thickness D1 of the first sub-coating layer (21) is less than or equal to the thickness D2 of the second sub-coating layer (22).

7. The electrode plate according to claim 6, wherein: The D1 and the D2 satisfy 3 <D2 / D1<10; And / or, the D1 satisfies 30 μm <D1<150μm; And / or, the D2 satisfies 570 μm <D2<450μm。 8. The electrode plate according to any one of claims 5 to 7, wherein: The primary particle size Dv50 of the active material in the first sub-coating layer (21) and the second sub-coating layer (22) ranges from 100 nm to 1000 nm.

9. The electrode plate according to any one of claims 1 to 8, wherein: A primer layer is provided between the current collector (10) and the coating (20); And / or, the active material in the coating (20) includes lithium iron phosphate.

10. A method for preparing an electrode sheet according to any one of claims 1 to 9, wherein: The following steps are involved: preparing a coating slurry, wherein the coating slurry comprises a first sub-coating slurry and a second sub-coating slurry; coating the first sub-coating slurry on at least one side of the current collector and drying the slurry to form a first sub-coating on the current collector; A second sub-coating slurry is coated on the side of the first sub-coating away from the current collector, so that the second sub-coating slurry covers the first sub-coating, and pores are formed in situ in the second sub-coating, and then dried to obtain an electrode plate.

11. The method for preparing an electrode sheet according to claim 10, wherein: The viscosity P of the second sub-coating slurry ranges from 1000 mPa·s to 8000 mPa·s.

12. The method for preparing an electrode sheet according to claim 10 or 11, wherein: The contact angle of the second sub-coating slurry on the surface of the first sub-coating is in the range of 15° to 60°.

13. A battery, wherein: The battery comprises an electrode sheet according to any one of claims 1 to 9; Alternatively, the battery comprises an electrode plate obtained by the method for preparing an electrode plate according to any one of claims 10 to 12.

14. An electrical device, wherein: The electric device comprises the battery as claimed in claim 13.

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