Pole piece and battery

Abstract

The utility model relates to the technical field of batteries, provides a pole piece and a battery, and aims to relieve the technical problem of large concentration polarization in the pole piece. The pole piece comprises a current collector and a composite layer arranged on the current collector, the composite layer comprises a first active material layer and a liquid absorption layer which are sequentially arranged in the direction away from the current collector, and the first active material layer is provided with a first surface away from the current collector; a concave part extending from the first surface to the interior of the first active material layer is also formed on the first active material layer, and the liquid absorption layer covers the first surface and the inner surface of the concave part.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, specifically to an electrode and a battery. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the requirements for the energy density of lithium-ion batteries are becoming increasingly stringent. The ideal way to improve the energy density of lithium-ion batteries is to increase the thickness of the electrode to increase the content of active materials. However, in lithium-ion batteries, the thicker the electrode, the worse the electrolyte penetration, leading to increased concentration polarization within the electrode during charging and discharging, making lithium-ion migration more difficult, and to some extent limiting the rate performance of the lithium-ion battery. Utility Model Content

[0003] The embodiments of this application provide an electrode and a battery that can solve the technical problem of large concentration polarization inside the electrode.

[0004] In a first aspect, embodiments of this application provide an electrode sheet, comprising: a current collector and a composite layer disposed on the current collector, the composite layer comprising a first active material layer and a liquid-absorbing layer disposed sequentially along a direction away from the current collector, the first active material layer having a first surface away from the current collector, and a recess extending from the first surface into the interior of the first active material layer is also formed on the first active material layer, the liquid-absorbing layer covering the first surface and the inner surface of the recess.

[0005] In one embodiment, the recess includes at least one of a groove and a through hole.

[0006] In one embodiment, the recess is an elongated groove that extends along a first direction of the first active material layer, and the length of the groove extending in the first direction is less than or equal to the length of the first active material layer in the first direction.

[0007] In one embodiment, the width of the recess remains constant or decreases along the direction close to the current collector.

[0008] In one embodiment, the sidewall of the recess is a straight wall or a curved wall.

[0009] In one embodiment, the concave portion is cut along the thickness direction of the first active material layer, and the cross-section of the concave portion is V-shaped, trapezoidal, square, semi-circular, or elliptical.

[0010] In one embodiment, there are multiple recesses, which are spaced apart, with the distance between two adjacent recesses ranging from 0.01 mm to 100 mm.

[0011] In one embodiment, the depth of the recess is less than the thickness of the first active material layer.

[0012] In one embodiment, the average width of the recess is 1 μm to 300 μm.

[0013] In one embodiment, the thickness of the absorbent layer is 0.2 μm to 50 μm.

[0014] In one embodiment, the thickness of the absorbent layer is 0.2 μm to 10 μm.

[0015] In one embodiment, the porosity of the liquid-absorbing layer is 5% to 99%.

[0016] In one embodiment, the thickness of the first active material layer is greater than 30 μm.

[0017] In one embodiment, the thickness of the electrode is greater than 60 μm.

[0018] In one embodiment, the absorbent layer is a mixed layer comprising at least a first adhesive and a first conductive agent.

[0019] In one embodiment, the first active material layer is a mixed layer comprising a first active material, a second binder, and a second conductive agent.

[0020] In one embodiment, the mass content of the second conductive agent in the first active material layer is less than the mass content of the first conductive agent in the liquid-absorbing layer; and / or, the oil absorption value of the first conductive agent is greater than the oil absorption value of the first active material.

[0021] In one embodiment, the content of the first active material in the first active material layer is greater than 50 wt%, and the content of the first conductive agent in the liquid-absorbing layer is greater than 50 wt%.

[0022] In one embodiment, the content of the second conductive agent increases in the first active material layer along the direction close to the current collector.

[0023] In one embodiment, the first active material layer comprises first active material particles, and the average particle size of the first active material particles increases along the direction close to the current collector. In one embodiment, the first conductive agent comprises at least one of conductive carbon material and conductive ceramic.

[0024] In one embodiment, the conductive carbon material includes at least one of carbon black, carbon nanotubes, carbon fibers, acetylene black, graphite, and graphene.

[0025] In one embodiment, the specific surface area of ​​the first conductive agent is 1 m². 2 / g~1000m 2 / g; and / or, the D50 particle size of the first conductive agent is 1nm to 50μm; and / or, the oil absorption value of the first conductive agent is greater than or equal to 500mL / 100g; and / or, the conductivity of the first conductive agent is 3000S·cm to 12000S·cm.

[0026] In one embodiment, the first adhesive includes at least one of carboxymethyl cellulose, polyacrylic acid, polyvinylidene fluoride, polytetrafluoroethylene, and styrene-butadiene rubber.

[0027] In one embodiment, the liquid-absorbing layer comprises 1 wt% to 80 wt% of the first conductive agent, 10 wt% to 99 wt% of the first binder, and the liquid-absorbing layer further comprises 0 wt% to 30 wt% of a dispersant.

[0028] In one embodiment, the dispersant includes at least one selected from acid anhydride, polyvinylpyrrolidone, sulfate salt, poly(N-vinylacetamide), polyvinyl alcohol, sulfonate, and polyethylene glycol.

[0029] In one embodiment, the liquid-absorbing layer comprises 58wt% to 75wt% of the first conductive agent, 12.5wt% to 30wt% of the first binder, and 8wt% to 12.5wt% of the dispersant.

[0030] In one embodiment, the dispersant includes at least one of ionic dispersants, nonionic dispersants, and polymeric dispersants.

[0031] In one embodiment, the porosity of the liquid-absorbing layer is at least greater than the porosity of the first active material layer.

[0032] In one embodiment, the recess is a laser-etched portion.

[0033] In one embodiment, the composite layer further includes a second active material layer disposed on the surface of the liquid-absorbing layer and facing away from the first active material layer.

[0034] In one embodiment, the number of composite layers on one side of the current collector is multiple, and the multiple composite layers are stacked together.

[0035] Secondly, embodiments of this application also provide a battery, including the electrode sheet described in the first aspect of embodiments of this application.

[0036] The beneficial effects of the embodiments of this application are as follows:

[0037] In the embodiments of this application, the electrode includes a current collector and a first active material layer. A recess is formed on the first active material layer, with the opening of the recess facing outward but extending into the interior of the first active material layer. The electrode also includes a liquid-absorbing layer, which is combined with the first active material layer and covers the first surface of the first active material layer and the inner surface of the recess. Compared with the first active material layer, the liquid-absorbing layer has a better ability to absorb electrolyte. Thus, the electrolyte can preferentially penetrate into the interior of the first active material layer through the portion of the liquid-absorbing layer located in the recess, shortening the lithium ion transport path, improving the wetting effect of the electrolyte on the electrode, and increasing the probability of contact between the active material particles inside the electrode and the electrolyte. Moreover, the liquid-absorbing layer can also serve as an electrolyte carrier to store the electrolyte, so that during the charging and discharging process of the electrode, the electrolyte stored in the liquid-absorbing layer can be quickly supplied to the first active material layer. Therefore, when the absorbent layer is located on the inner surface of the recess, the absorbent layer and the recess cooperate to form a "fast channel", which allows the electrolyte to quickly enter the first active material layer, promotes lithium ion transport in the electrode and increases the migration speed of lithium ions, and reduces concentration polarization inside the electrode. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic cross-sectional view of the electrode provided in an embodiment of this application. Figure 1 ;

[0040] Figure 2 This is a schematic cross-sectional view of the electrode provided in an embodiment of this application. Figure 2 ;

[0041] Figure 3 This is a schematic cross-sectional view of the electrode provided in an embodiment of this application. Figure 3 ;

[0042] Figure 4 This is a schematic cross-sectional view of the electrode provided in an embodiment of this application. Figure 4 ;

[0043] Figure 5 This is a schematic cross-sectional view of the electrode provided in an embodiment of this application. Figure 5 ;

[0044] Figure 6 This is a schematic cross-sectional view of the electrode provided in an embodiment of this application. Figure 6 ;

[0045] Figure 7 This is a top view of the first active material layer in the electrode provided in an embodiment of this application;

[0046] Figure 8 This is a flowchart illustrating the preparation process of the electrode sheet provided in the embodiments of this application;

[0047] Figure 9 This is a schematic diagram of the battery structure provided in an embodiment of this application.

[0048] Figure 10 This is a SEM image of the electrode provided in Example 8. In the image, A refers to the first active material layer and B refers to the conductive layer.

[0049] Figure 11 yes Figure 10 Enlarged SEM image of the middle frame area;

[0050] Figure 12 This is a SEM image of the electrode provided in Example 1. In the image, A refers to the first active material layer and B refers to the conductive layer.

[0051] Figure 13 yes Figure 12 Enlarged SEM image of the middle frame area;

[0052] Figure 14 The image provided is a SEM image of the electrode provided in Comparative Example 1;

[0053] Figure 15 These are process photos of the electrode sheet provided in Example 8 during contact angle testing, in which... Figure 15 Image (a) is a photo taken during the preparation stage. Figure 15 Image (b) is a photograph taken at the beginning. Figure 15 Image (c) is a photograph of the intermediate process. Figure 15 Image (d) is a photograph taken at the end of the event;

[0054] Figure 16 These are photographs of the electrode provided in Comparative Example 1 during the contact angle test. Figure 16 Image (a) is a photo taken during the preparation stage. Figure 16 Image (b) is a photograph taken at the beginning. Figure 16 Image (c) is a photograph of the intermediate process. Figure 16 Image (d) is a photo taken at the end of the event.

[0055] Figure label:

[0056] 10. Electrode;

[0057] 1. Current collector;

[0058] 2. Composite layer;

[0059] 21. First active material layer; 211. First surface; 212. Recess; 21a. Second wet film layer;

[0060] 22. Liquid-absorbing layer; 22a. First wet film layer;

[0061] 23. Second active material layer; 23a. Third wet film layer;

[0062] 100. Battery. Detailed Implementation

[0063] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0064] Furthermore, it should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of this application. In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operation, specifically the directions shown in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0065] 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 the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0066] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0067] The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0068] In the description of the embodiments of this application, the words "example" or "for example" are used to indicate exemplification, illustration, or description. Any embodiment or design described as "example" or "for example" in the embodiments of this application is not to be construed as being more preferred or having more advantages than another embodiment or design. The use of the words "example" or "for example" is intended to present relative concepts in a clear manner.

[0069] To facilitate understanding of the present application, the spline curves and arrows used in the reference numerals in the accompanying drawings are explained below: spline curves without arrows indicate solid parts, that is, parts with solid structures; spline curves with arrows indicate virtual parts, that is, parts without solid structures.

[0070] This application provides an electrode, a method for preparing the electrode, and a battery. The embodiments are described in detail below.

[0071] Firstly, please see Figures 1 to 7 This application provides an electrode 10, which includes a current collector 1 and a composite layer 2, with the composite layer 2 disposed on the current collector 1. The composite layer 2 includes a first active material layer 21 and a liquid-absorbing layer 22 sequentially disposed in a direction away from the current collector 1. The first active material layer 21 has a first surface 211 away from the current collector 1, and a recess 212 extending from the first surface 211 into the interior of the first active material layer 21 is also formed on the first active material layer 21. The liquid-absorbing layer 22 covers the inner surface of the first surface 211 and the recess 212.

[0072] The electrode 10 can be used in the battery 100, such as a secondary battery, including but not limited to a lithium-ion battery. The electrode 10 can be a positive electrode or a negative electrode. When the electrode 10 is a positive electrode, the current collector 1 is a positive current collector, and the first active material layer 21 is a positive active material layer; when the electrode 10 is a negative electrode, the current collector 1 is a negative current collector, and the first active material layer 21 is a negative active material layer.

[0073] If current collector 1 is a positive current collector, for example, current collector 1 can be aluminum foil, carbon-coated aluminum foil, safety-coated aluminum foil, etched aluminum foil, or aluminum mesh. The thickness of current collector 1 can be 5μm to 20μm, for example, 5μm, 10μm, 15μm, or 20μm.

[0074] If current collector 1 is a negative current collector, for example, current collector 1 can be a copper foil with a thickness of 3μm to 20μm, such as 3μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm or 20μm.

[0075] The current collector 1 has two opposite surfaces along the thickness direction of the current collector 1. The composite layer 2 is disposed on the current collector 1. The composite layer 2 can be bonded to one side surface of the current collector 1 or the composite layer 2 can be bonded to both sides of the current collector 1.

[0076] The composite layer 2 includes a first active material layer 21 and a liquid-absorbing layer 22 bonded together, and the first active material layer 21 and the liquid-absorbing layer 22 are distributed sequentially in a direction away from the current collector 1. That is, the first active material layer 21 is located between the current collector 1 and the liquid-absorbing layer 22, and the first active material layer 21 is closer to the current collector 1 than the liquid-absorbing layer 22.

[0077] For ease of distinction later, the surface of the first active material layer 21 that is away from the current collector 1 (in other words, the side that is close to the liquid absorption layer 22) is referred to as the first surface 211.

[0078] The first active material layer 21 has an uneven surface on the side away from the current collector 1. Specifically, the first active material layer 21 has a recess 212, which is formed by a partial indentation of the first active material layer 21 from the first surface 211 into the interior of the first active material layer 21. That is, the opening of the recess 212 is located on the first surface 211 (i.e., the opening faces outward), and the recess 212 extends into the interior of the first active material layer 21. Typically, there are also some non-recessed areas on the first active material layer 21, which are formed as protrusions, thus making the side of the first active material layer 21 away from the current collector 1 have an uneven structure. As an example, the recess 212 includes at least one of a groove and a through hole. Optionally, the groove includes a blind hole. The formation method of the recess 212 includes, but is not limited to, at least one of laser etching, layered coating, and pore-forming agent pore-forming.

[0079] The first active material layer 21 and the liquid-absorbing layer 22 are combined, specifically, the liquid-absorbing layer 22 covers the first surface 211 and extends into the recess 212 to cover the inner surface of the recess 212. The liquid-absorbing layer 22 extends into the recess 212, which may completely fill the recess 212. Please refer to [link to relevant documentation]. Figure 2For example, when the absorbent layer 22 is thicker, or the recess 212 is narrower or shallower, the absorbent layer 22 is more likely to completely fill the recess 212; alternatively, the absorbent layer 22 may only adhere to the inner surface of the recess 212 and not completely fill it. Please refer to [link to relevant documentation]. Figure 1 For example, if the absorbent layer 22 is thinner, or the recess 212 is wider, or the recess 212 is deeper, the absorbent layer 22 is more likely to adhere to the inner surface of the recess 212. The inner surface of the recess 212 refers to the inner wall surface of the recess 212, including the bottom wall surface and the side wall surface.

[0080] The first active material layer 21 is a layer structure comprising at least an active material. Optionally, the first active material layer 21 further includes a binder and a conductive agent. For ease of subsequent description, the active material, binder, and conductive agent in the first active material layer 21 will be referred to as the first active material, the second binder, and the second conductive agent, respectively. When the type of the first active material layer 21 is different, the selection of the first active material, the second binder, and the second conductive agent contained therein will also differ. In some embodiments, the first active material layer 21 may also not contain a conductive agent, i.e., a conductive agent-free formulation design.

[0081] If the first active material layer 21 is a positive electrode active material layer, and the first active material is a positive electrode active material, for example, the first active material includes at least one of nickel-cobalt-manganese ternary materials (NMC), lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4, LFP), lithium manganese oxide (LiMn2O4, LMO), and lithium nickel cobalt aluminum oxide (NCA). Similarly, if the second conductive agent is a positive electrode conductive agent, for example, the second conductive agent includes at least one of carbon black, conductive graphite, graphene, and carbon nanotubes. Similarly, if the second binder is a positive electrode binder, the second binder includes at least one of organic polymers such as polyacrylic acid (PAA) and polyvinylidene fluoride (PVDF).

[0082] If the first active material layer 21 is a negative electrode active material layer, and the first active material is a negative electrode active material, for example, the first active material includes at least one of graphite, graphene, hard carbon, soft carbon, and silicon-based materials. Similarly, if the second conductive agent is a negative electrode conductive agent, for example, the second conductive agent includes at least one of carbon black, graphene, acetylene black, carbon nanotubes, and conductive graphite. Similarly, if the second binder is a negative electrode binder, for example, the second binder includes styrene-butadiene rubber (SBR).

[0083] The absorbent layer 22 refers to a structural layer with superior electrolyte absorption capacity. Specifically, the absorbent layer 22's ability to absorb electrolyte (referred to as absorbent layer) is at least superior to that of the first active material layer 21. The amount of electrolyte absorbed per unit volume of material per unit time can be used to indicate the material's electrolyte absorption capacity; generally, the larger the amount of electrolyte, the better the material's electrolyte absorption capacity. Alternatively, the time taken for a unit volume of material to absorb a unit volume of electrolyte can be used to indicate the material's electrolyte absorption capacity; generally, the shorter the time, the better the material's electrolyte absorption capacity. For example, the electrolyte absorption capacity of the absorbent layer 22 and the first active material layer 21 can be tested using a contact angle test. Typically, the time for the same volume of electrolyte to completely enter the absorbent layer 22 is shorter than the time to completely enter the first active material layer 21.

[0084] The electrode 10 provided in this embodiment includes a current collector 1 and a first active material layer 21. A recess 212 is formed on the first active material layer 21. The opening of the recess 212 faces outwards, but the recess 212 extends into the interior of the first active material layer 21. The electrode 10 also includes a liquid-absorbing layer 22, which is bonded to the first active material layer 21 and covers the first surface 211 of the first active material layer 21 and the inner surface of the recess 212. Compared to the first active material layer 21, the liquid-absorbing layer 22 has superior properties. The absorbent layer 22 has the ability to absorb electrolyte, allowing the electrolyte to preferentially penetrate quickly into the first active material layer 21 through the portion of the absorbent layer 22 located in the recess 212. This shortens the lithium ion transport path, improves the wetting effect of the electrolyte on the electrode 10, and increases the probability of contact between the active material particles inside the electrode 10 and the electrolyte. Furthermore, the absorbent layer 22 can also act as an electrolyte carrier to store the electrolyte, so that during the charging and discharging process of the electrode 10, the electrolyte stored in the absorbent layer 22 can be quickly supplied to the first active material layer 21. Therefore, when the absorbent layer 22 is located on the inner surface of the recess 212, the absorbent layer 22 and the recess 212 cooperate to form a "fast channel," allowing the electrolyte to quickly enter the first active material layer 21, promoting lithium ion transport in the electrode 10 and increasing the migration speed of lithium ions, while reducing concentration polarization inside the electrode 10.

[0085] In some embodiments, the first active material in the first active material layer 21 is particulate, i.e., first active material particles. Thus, structurally, the first active material layer 21 includes: a first matrix layer having a second binder and a second conductive agent, and first active material particles dispersed in the first matrix layer.

[0086] As an example, the liquid absorption capacity of the liquid absorption layer 22 can be improved by adjusting the composition and structure of the liquid absorption layer 22.

[0087] In some implementation methods, please refer to Figure 1The absorbent layer 22 is a mixed layer comprising at least a first adhesive and a first conductive agent.

[0088] It is understood that the absorbent layer 22 also includes a binder and a conductive agent. For ease of description, the binder and conductive agent in the absorbent layer 22 are referred to as the first binder and the first conductive agent, respectively. The absorbent layer 22 includes the first binder and the first conductive agent. The first binder enables the absorbent layer 22 to bond with the first active material layer 21, while the first conductive agent enables the absorbent layer 22 to have a certain conductivity. This not only facilitates the transmission of current between the absorbent layer 22 and the first active material layer 21, but also reduces the internal resistance of the electrode 10. Generally, conductive agents also have a strong ability to absorb electrolyte. Adding the first conductive agent to the absorbent layer 22 can also enhance the ability of the absorbent layer 22 to wet the electrolyte. The first binder and the second binder can be the same or different. The first conductive agent and the second conductive agent can also be the same or different. As an example, the first binder includes at least one of the following organic polymer materials: carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and styrene-butadiene rubber (SBR). As an example, the first conductive agent includes at least one of conductive carbon material and conductive ceramic. Optionally, the conductive carbon material includes at least one of carbon black, carbon nanotubes, carbon fibers, acetylene black, graphite, and graphene. Optionally, the carbon black includes at least one of conductive carbon black Super P, superconducting carbon black, and Ketjen black. Optionally, the carbon nanotubes include at least one of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Optionally, the conductive ceramic includes at least one of CaF2 structured substances such as β-Al2O3, CaO·ZrO2, and Y2O3·ZrO2. In the liquid-absorbing layer 22, the first binder and the first conductive agent are mixed together. The liquid-absorbing layer 22 may or may not contain an active material. When the liquid-absorbing layer 22 contains an active material, the liquid-absorbing layer 22 is formed as an active material layer; when the liquid-absorbing layer 22 does not contain an active material, the liquid-absorbing layer 22 is formed as a conductive layer.

[0089] In some embodiments, the first active material layer 21 is a mixed layer comprising a first active material, a second binder, and a second conductive agent. The first active material in the first active material layer 21 can increase the energy density of the electrode 10, the second binder can bond the first active material layer 21 to the current collector 1, and the second conductive agent is dispersed in the first active material layer 21 to construct a conductive network, promoting ion transport.

[0090] In some embodiments, the mass content of the second conductive agent in the first active material layer 21 is less than the mass content of the first conductive agent in the liquid-absorbing layer 22. Generally, the conductive agent has better liquid absorption capacity than the active material; by increasing the mass content of the conductive agent (referred to as the first conductive agent) in the liquid-absorbing layer 22, the liquid absorption capacity of the liquid-absorbing layer 22 can be improved.

[0091] In some embodiments, the content of the first active material in the first active material layer 21 is greater than 50 wt%, and the content of the first conductive agent in the liquid-absorbing layer 22 is greater than 50 wt%. It can be understood that the content of the second conductive agent in the first active material layer 21 is less than 50 wt%, meaning the mass content of the first conductive agent in the liquid-absorbing layer 22 is greater than the mass content of the second conductive agent in the first active material layer 21, thereby improving the liquid absorption capacity of the liquid-absorbing layer 22. As an example, the content of the first active material in the first active material layer 21 is 50 wt%, 60 wt%, 70 wt%, 80 wt%, 85 wt%, 90 wt%, 92 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, or 98 wt%. As an example, the content of the first conductive agent in the absorbent layer 22 is 50wt%, 60wt%, 70wt%, 80wt%, 85wt%, 90wt%, 92wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, or 99wt%.

[0092] In some embodiments, the first active material layer 21 includes a first active material, and the oil absorption value of the first conductive agent is greater than that of the first active material. Since the electrolyte mainly contains electrolytes and organic solvents, increasing the oil absorption value of the first conductive agent in the liquid-absorbing layer 22 can enhance the ability of the liquid-absorbing layer 22 to absorb the electrolyte. In other words, the electrolyte is more easily absorbed by the liquid-absorbing layer 22 compared to the first active material layer 21. Optionally, the liquid-absorbing layer 22 does not contain any active material or contains a small amount of active material.

[0093] In some embodiments, the porosity of the liquid-absorbing layer 22 is at least greater than that of the first active material layer 21. Increasing the porosity of the liquid-absorbing layer 22 can also improve its liquid absorption capacity. In this case, the liquid-absorbing layer 22 can be either an active material layer or a conductive layer. When the liquid-absorbing layer 22 is an active material layer, the amount of active material in the liquid-absorbing layer 22 can be either high or low.

[0094] When the liquid-absorbing layer 22 also contains active material, for ease of description, the active material in the liquid-absorbing layer 22 is referred to as the third active material. The third active material can be the same as or different from the first active material. However, the porosity of the liquid-absorbing layer 22 is greater than that of the first active material layer 21. Methods for adjusting the porosity of the liquid-absorbing layer 22 include, but are not limited to, selecting a material with lower compaction density, increasing the material particle size, and decreasing the compaction density of the liquid-absorbing layer 22. For example, when preparing the first active material layer 21, the first active material layer 21 is first subjected to roll pressing, but not when preparing the liquid-absorbing layer 22. Similarly, when the electrode 10 is a positive electrode, the liquid-absorbing layer 22 is a positive active material layer; when the electrode 10 is a negative electrode, the liquid-absorbing layer 22 is a negative active material layer. When the type of liquid-absorbing layer 22 is different, the selection of the third active material it contains will also differ.

[0095] If the absorbent layer 22 is a positive electrode active material layer and the third active material is a positive electrode active material, for example, the third active material includes at least one of nickel-cobalt-manganese ternary materials (NMC), lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4, LFP), lithium manganese oxide (LiMn2O4, LMO), and lithium nickel cobalt-aluminum oxide (NCA). If the absorbent layer 22 is a negative electrode active material layer and the third active material is a negative electrode active material, for example, the third active material includes at least one of graphite, graphene, hard carbon, soft carbon, and silicon-based materials. In some embodiments, when the absorbent layer 22 is an active material layer, the third active material is particulate, i.e., third active material particles. Thus, structurally, the absorbent layer 22 includes: a third matrix layer having a first binder and a first conductive agent, and third active material particles dispersed in the third matrix layer.

[0096] In some embodiments, the recess 212 is a laser-etched portion, meaning that the recess 212 is obtained by locally irradiating the first active material layer 21 with a high-energy-density laser beam, causing the material in the local area of ​​the first active material layer 21 to vaporize and evaporate in a very short time. Using laser etching to prepare the recess 212 is not only highly efficient but also allows for easy control of the shape and size of the recess 212. However, using laser etching to prepare the recess 212 results in micron-sized dust residue on the surface of the first active material layer 21 (especially the inner surface of the recess 212). This dust mainly comes from the loosened first active material, the second conductive agent, and the carbonized second binder. Moreover, this micron-sized dust is difficult to remove using dust removal equipment. Therefore, when the electrode 10 is used to prepare the battery 100, this dust can easily be carried into the separator of the battery 100 through the electrolyte, causing internal short circuits or increased self-discharge in the battery 100. However, in this embodiment, since the electrode 10 also includes a liquid-absorbing layer 22, which is combined with the first active material layer 21 and covers the first surface 211 of the first active material layer 21 and the inner surface of the recess 212, the liquid-absorbing layer 22 can cover the dust remaining on the surface of the first active material layer 21 and prevent the dust from entering the electrolyte. Moreover, the binder contained in the liquid-absorbing layer 22 (called the first binder) can also stick to the dust. Especially at the inner surface of the recess 212, the binder will penetrate into the first active material layer 21 in a small amount to form a bonding interface layer between the liquid-absorbing layer 22 and the first active material layer 21. Not only will a large amount of dust be solidified in the bonding interface layer, but the bonding interface layer can also prevent the loose material on the side wall of the recess 212 from further loosening, ultimately reducing the dust from leaving the electrode 10 and reducing the risk of internal short circuit or increased self-discharge in the battery 100.

[0097] In some embodiments, the specific surface area of ​​the first conductive agent is 1 m². 2 / g~1000m 2 / g. The specific surface area of ​​the first conductive agent affects the electrolyte storage capacity of the absorbent layer 22; the larger the specific surface area of ​​the first conductive agent, the stronger the electrolyte storage capacity of the absorbent layer 22. For example, the specific surface area of ​​the first conductive agent is 1m². 2 / g, 10m 2 / g, 100m 2 / g、200m 2 / g、300m 2 / g、400m 2 / g、500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g or 1000m 2 / g. This is usually related to the specific surface area of ​​the first conductive agent and the morphology of the material. As an example, the first conductive agent includes a conductive carbon material, which includes at least one of carbon black, carbon nanotubes, carbon fibers, graphite, and graphene, wherein the specific surface area of ​​the carbon black is greater than 5m². 2 / g, the specific surface area of ​​carbon nanotubes is greater than 1m² 2 / g, the specific surface area of ​​graphene is 1m² 2 / g~500m 2 / g, the specific surface area of ​​graphite is 1m² 2 / g~1000m 2 / g, the specific surface area of ​​carbon fiber is 1m² 2 / g~1000m 2 / g.

[0098] In some embodiments, the D50 particle size (i.e., average particle size) of the first conductive agent is 1 nm to 50 μm. A larger D50 particle size of the first conductive agent increases the porosity of the liquid-absorbing layer 22, thus increasing the liquid storage space of the liquid-absorbing layer 22. Simultaneously, the electrolyte can more easily penetrate the liquid-absorbing layer 22 to reach the first active material layer 21. However, an excessively large D50 particle size of the first conductive agent can affect the thickness of the liquid-absorbing layer 22, and it can also reduce the specific surface area of ​​the first conductive agent. As examples, the D50 particle size of the first conductive agent can be 1 nm, 5 nm, 10 nm, 100 nm, 200 nm, 500 nm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm. As an example, the first conductive agent includes a conductive carbon material, which includes at least one of carbon black, carbon nanotubes, carbon fibers, graphite, and graphene, wherein the D50 particle size of carbon black is 1 nm to 200 nm, the D50 particle size of carbon nanotubes is 1 nm to 100 nm, the D50 particle size of graphene is 1 μm to 50 μm, the D50 particle size of graphite is 10 nm to 20 μm, and the D50 particle size of carbon fiber is 5 nm to 1 μm.

[0099] In some embodiments, the oil absorption value of the first conductive agent is greater than that of the first active material.

[0100] In some embodiments, the oil absorption value of the first conductive agent is greater than or equal to 500 mL / 100 g. Typically, the solvent in the electrolyte is an organic solvent. The oil absorption value of the first conductive agent affects the ability of the absorbent layer 22 to absorb the electrolyte. By setting the oil absorption value of the first conductive agent to be greater than or equal to 500 mL / 100 g, the absorbent layer 22 can quickly wet the electrolyte, thereby accelerating the entry of the electrolyte into the interior of the electrode 10. For example, the oil absorption value of the first conductive agent is 500 mL / 100 g, 1000 mL / 100 g, 1500 mL / 100 g, 2000 mL / 100 g, or 2500 mL / 100 g. As an example, the first conductive agent includes conductive carbon black with an oil absorption value of 1000 mL / 100 g; or the first conductive agent includes carbon nanotubes with an oil absorption value of 500 mL / 100 g; or the first conductive agent includes graphene with an oil absorption value of 2000 mL / 100 g; or the first conductive agent includes graphite with an oil absorption value of 500 mL / 100 g.

[0101] In some embodiments, the conductivity of the first conductive agent is 3000 S·cm to 12000 S·cm. The higher the conductivity of the first conductive agent, the higher the conductivity of the absorbent layer 22, which is beneficial for reducing the internal resistance of the battery 100. As examples, the conductivity of the first conductive agent is 3000 S·cm, 5000 S·cm, 7000 S·cm, 9000 S·cm, 10000 S·cm, or 12000 S·cm. As examples, the first conductive agent includes carbon black with a conductivity of 3000 S·cm; or the first conductive agent includes carbon nanotubes with a conductivity of 5000 S·cm; or the first conductive agent includes graphene with a conductivity of 12000 S·cm; or the first conductive agent includes graphite with a conductivity of 5000 S·cm; or the first conductive agent includes carbon fiber with a conductivity of 5000 S·cm.

[0102] In some embodiments, the liquid-absorbing layer 22 comprises 1wt% to 80wt% of a first conductive agent, 10wt% to 99wt% of a first binder, and 0wt% to 30wt% of a dispersant. That is, the liquid-absorbing layer 22 is a conductive layer, meaning it does not contain any active material. The liquid-absorbing layer 22 mainly comprises a conductive agent and a binder; for example, it may only contain the first conductive agent and the first binder, or it may only contain the first conductive agent, the first binder, and a dispersant. Within the above range, the protective layer 3 is a conductive layer, and the liquid-absorbing layer 22 possesses both good liquid absorption capacity and stable bonding with the first active material layer 21. Especially when the recess 212 is a laser-etched portion, the first binder can better penetrate from the inner wall surface of the recess 212 into the active material layer 2, better solidifying the inner wall of the recess 212, thereby effectively reducing the powder floating on the electrode 10. As an example, the content of the first conductive agent is 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, or 80 wt%; the content of the first binder is 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or 99 wt%; and the content of the dispersant is 0 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%. When the liquid-absorbing layer 22 also includes a dispersant, the dispersant can effectively promote the dispersion of the first conductive agent in the first binder, especially when the first conductive agent is a conductive carbon material. Optionally, the dispersant is at least one of plasma dispersants, nonionic dispersants, and polymeric dispersants. As an example, the dispersant includes at least one of acid anhydrides, polyvinylpyrrolidone (PVP), sulfate esters, sulfonates, poly(N-vinylacetamide) (PNVA), polyvinyl alcohol (PVA), and polyethylene glycol. In the absorbent layer 22, the first binder, the first conductive agent, and the dispersant are mixed together.

[0103] In some embodiments, the absorbent layer 22 comprises 58 wt% to 75 wt% of a first conductive agent, 12.5 wt% to 30 wt% of a first binder, and 8 wt% to 12.5 wt% of a dispersant. Within the above range, the absorbent layer 22 possesses both good absorbency and bonding stability, effectively reducing powder floating on the electrode 10. As an example, in the protective layer 3, the content of the first conductive agent is 58 wt%, 60 wt%, 62 wt%, 64 wt%, 66 wt%, 68 wt%, 70 wt%, 72 wt%, 74 wt%, or 75 wt%; the content of the first binder is 12.5 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, or 30 wt%; and the content of the dispersant is 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, or 12.5 wt%.

[0104] In some embodiments, the porosity of the liquid-absorbing layer 22 is 5% to 99%. The higher the porosity of the liquid-absorbing layer 22, the greater its liquid storage capacity. As examples, the porosity of the liquid-absorbing layer 22 is 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 99%.

[0105] In some embodiments, the thickness of the absorbent layer 22 is 0.2 μm to 50 μm. Generally, a thicker absorbent layer 22 results in a greater absorbency and improved rate performance of the battery 100. However, an excessively thick absorbent layer 22 can also lead to a decrease in the energy density of the battery 100. As examples, the thickness of the absorbent layer 22 is 0.2 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. Here, the thickness of the absorbent layer 22 is the average thickness.

[0106] In some embodiments, the thickness of the absorbent layer 22 is 0.2 μm to 10 μm. Within this thickness range, the battery 100 exhibits both good rate performance and energy density. As examples, the thickness of the absorbent layer 22 is 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. Here, the thickness of the absorbent layer 22 is the average thickness.

[0107] In some embodiments, the electrode 10 is a thick electrode, wherein the thickness of the first active material layer 21 is greater than 30 μm. By increasing the thickness of the first active material layer 21, the content of active material in the electrode 10 is increased, thereby increasing the energy density of the battery 100. As an example, the thickness of the first active material layer 21 is 31 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, or 150 μm.

[0108] In some embodiments, the electrode 10 is a thick electrode, and the current collector 1 has the composite layer 2 on only one side, with the thickness of the electrode 10 being greater than 60 μm. As an example, the thickness of the electrode 10 is 61 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 130 μm, 150 μm, 170 μm, 190 μm, or 210 μm.

[0109] In some embodiments, the electrode 10 is a thick electrode, but a composite layer 2 is provided on both sides of the current collector 1, and the thickness of the electrode 10 is greater than 60 μm. As an example, the thickness of the electrode 10 is 61 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 170 μm, 190 μm, 210 μm, 250 μm, 280 μm, or 300 μm.

[0110] In some implementations, please refer to Figure 7 The recess 212 is an elongated groove extending along a first direction of the first active material layer 21. The length H1 of the groove extending in the first direction is less than or equal to the length H2 of the first active material layer 21 in the first direction. For example, the first direction can be the transverse (TD direction) or longitudinal (MD direction) of the first active material layer 21. As an example, the first direction is the X direction, the groove extends along the X direction on the first active material layer 21, and the length H1 of the groove is equal to the length H2 of the first active material layer 21. As an example, the first direction is the X direction, the groove extends along the X direction on the first active material layer 21, and the length H1 of the groove is less than the length H2 of the first active material layer 21. In other cases, the first direction can also be the Y direction.

[0111] In some embodiments, there are multiple recesses 212, which are spaced apart. By increasing the number of recesses 212 on the first active material layer 21, and ensuring that these recesses are spaced apart (i.e., dispersed across the first active material layer 21), the overall liquid absorption effect of the first active material layer 21 is improved, and the concentration polarization within the electrode 10 is reduced. Optionally, the spacing between two adjacent recesses 212 is 0.01 mm to 100 mm. The spacing between two adjacent recesses 212 should not be too large, otherwise the number of recesses 212 that can be provided per unit area will decrease. Examples include 0.01 mm, 0.1 mm, 1 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, or 100 mm. For further examples, please refer to [link to example]. Figure 7 The distance between two adjacent recesses 212 can refer to the distance W1 between two adjacent recesses 212 in the transverse direction along the first active material layer 21, or it can refer to the distance W2 between two adjacent recesses 212 in the longitudinal direction along the first active material layer 21.

[0112] In some embodiments, the width of the recess 212 remains constant or decreases along the direction close to the current collector 1. In this way, the width of the recess 212 is maximized at the opening, which not only facilitates the fabrication of the recess 212 itself, but also facilitates the fabrication of the absorbent layer 22 so that it extends into the recess 212 and bonds with the inner surface of the recess 212.

[0113] In some embodiments, the sidewall of the recess 212 can be a straight wall or a curved wall. As an example, the sidewall of the recess 212 is an arc-shaped curved wall. When the sidewall of the recess 212 is a straight wall, the sidewall of the recess 212 can extend along the thickness direction of the first active material layer 21, or it can be inclined relative to the thickness direction of the first active material layer 21.

[0114] In some implementations, please refer to Figure 6 The recess 212 is cut along the thickness direction of the first active material layer 21, and the cross-section of the recess 212 is V-shaped, trapezoidal, square, semi-circular or semi-elliptical.

[0115] In some embodiments, the average width of the recess 212 is 1 μm to 300 μm. The width of the recess 212 should not be too small, otherwise it will be difficult for the liquid-absorbing layer 22 to extend into the recess 212, but it should not be too large either, otherwise the recess 212 will be too wide, resulting in insufficient mass proportion of the first active material layer 21 in the electrode 10. As an example, the average width of the recess 212 is 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm or 300 μm.

[0116] In some embodiments, the depth of the recess 212 is less than the thickness of the first active material layer 21. Typically, in the electrode 10, the portion of the first active material layer 21 closer to the current collector 1 is farther from the electrolyte and less likely to be wetted by the electrolyte, thus reducing concentration polarization within the electrode 10. Conversely, the deeper the recess 212, the closer it is to the current collector 1, allowing the electrolyte to more easily penetrate quickly through the recess 212 into the portion of the first active material layer 21 closest to the current collector 1, reducing concentration polarization within the electrode 10. Optionally, the depth of the recess 212 is greater than half the thickness of the first active material layer 21. As an example, the ratio of the depth of the recess 212 to the thickness of the first active material layer 21 is 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or 0.98.

[0117] In some embodiments, the content of the second conductive agent in the first active material layer 21 increases along the direction close to the current collector 1. Compared to the first active material, the second conductive agent in the first active material layer 21 has a better wetting effect on the electrolyte. By increasing the content of the second conductive agent in the portion of the first active material layer 21 close to the current collector 1, it is beneficial to promote the rapid migration of lithium ions into the interior of the first active material layer 21, improve the uniformity of electrolyte wetting in the first active material layer 21, and reduce concentration polarization within the first active material layer 21. For an example, please refer to... Figure 5 The first active material layer 21 includes multiple sub-active material layers stacked together, and the content of the second conductive agent in each sub-active material layer gradually increases along the direction close to the current collector 1.

[0118] In some embodiments, the first active material in the first active material layer 21 is granular, i.e., it consists of first active material particles. Structurally, the first active material layer 21 is a mixed layer comprising first active material particles, a second binder, and a second conductive agent. In the first active material layer 21, the average particle size of the first active material particles increases along the direction approaching the current collector 1. By increasing the average particle size of the first active material in the portion of the first active material layer 21 approaching the current collector 1, the porosity of this portion can be increased, which facilitates the migration of lithium ions through the pores into the interior of the first active material layer 21, improves the uniformity of electrolyte wetting in the first active material layer 21, and reduces concentration polarization within the first active material layer 21. For an example, please refer to... Figure 5 The first active material layer 21 includes multiple sub-active material layers stacked together. Along the direction close to the current collector 1, the average particle size of the first active material in each sub-active material layer gradually increases.

[0119] In some implementations, please refer to Figure 3The composite layer 2 also includes a second active material layer 23, which is disposed on the surface of the liquid-absorbing layer 22 and away from the first active material layer 21.

[0120] Specifically, along the direction away from the current collector 1, the first active material layer 21, the liquid-absorbing layer 22, and the second active material layer 23 are sequentially distributed, with the liquid-absorbing layer 22 sandwiched between the first active material layer 21 and the second active material layer 23. Wherein, if the liquid-absorbing layer 22 does not completely fill the recess 212, the second active material layer 23 can partially fill the recess 212; when the liquid-absorbing layer 22 completely fills the recess 212, the second active material layer 23 lies flat on one side surface of the liquid-absorbing layer 22.

[0121] The second active material layer 23 also includes an active material and a binder. For ease of description, the active material and binder in the second active material layer 23 are referred to as the second active material and the third binder, that is, the second active material layer 23 is a mixed layer that includes at least the second active material and the third binder. Optionally, the second active material layer 23 also includes a conductive agent, referred to as the third conductive agent. The second active material and the first active material may be the same or different, the third binder and the second binder may be the same or different, and the third conductive agent and the second conductive agent may be the same or different. The composition of the second active material layer 23 may be the same or different from the composition of the first active material layer 21.

[0122] Similarly, when electrode 10 is a positive electrode, the second active material layer 23 is a positive active material layer; when electrode 10 is a negative electrode, the second active material layer 23 is a negative active material layer. When the type of the second active material layer 23 is different, the selection of the second active material, the third binder, and the third conductive agent contained therein will also be different.

[0123] If the second active material layer 23 is a positive electrode active material layer, and the second active material is a positive electrode active material, for example, the second active material includes at least one of nickel-cobalt-manganese ternary materials (NMC), lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4, LFP), lithium manganese oxide (LiMn2O4, LMO), and lithium nickel cobalt aluminum oxide (NCA). Similarly, the third conductive agent is a positive electrode conductive agent, and for example, the third conductive agent includes at least one of carbon black, conductive graphite, graphene, acetylene black, and carbon nanotubes. Similarly, the third binder is a positive electrode binder, and the third binder includes at least one of organic polymer materials such as polyacrylic acid (PAA) and polyvinylidene fluoride (PVDF).

[0124] If the second active material layer 23 is a negative electrode active material layer, and the second active material is a negative electrode active material, for example, the second active material includes at least one of graphite, graphene, hard carbon, soft carbon, and silicon-based materials. Similarly, if the third conductive agent is a negative electrode conductive agent, for example, the third conductive agent includes at least one of carbon black, graphene, acetylene black, carbon nanotubes, and conductive graphite. Likewise, if the third binder is a negative electrode binder, for example, the third binder includes styrene-butadiene rubber (SBR).

[0125] In the electrode 10 provided in this embodiment, the composite layer 2 includes a first active material layer 21, a liquid-absorbing layer 22, and a second active material layer 23. The first active material layer 21 and the second active material layer 23 together serve as the active material layer, while the liquid-absorbing layer 22 is sandwiched between the first active material layer 21 and the second active material layer 23, which is equivalent to the liquid-absorbing layer 22 being disposed inside the active material layer. Thus, when the electrode 10 is applied to the battery 100, when the battery 100 is not working (e.g., when it is at rest), the good wetting ability of the liquid-absorbing layer 22 can absorb and retain electrolyte. During the charging and discharging process of the battery 100, the liquid-absorbing layer 22 can act as a small electrolyte source to continuously transport electrolyte to the first active material layer 21 and the second active material layer 23 on both sides, greatly shortening the movement path of lithium ions and reducing concentration polarization inside the electrode 10. In addition, adding the second active material layer 23 can also improve the energy density of the battery 100.

[0126] In some embodiments, the second active material in the second active material layer 23 is particulate, i.e., second active material particles. Thus, structurally, the second active material layer 23 includes: a second matrix layer having a third binder and a third conductive agent, and second active material particles dispersed in the second matrix layer.

[0127] In some implementations, please refer to Figure 4 The current collector 1 has multiple composite layers 2 on one side, with the multiple composite layers 2 stacked together. For example, the current collector 1 may have 2, 3, 4, or 5 composite layers 2 on one side. "One side" refers to one of the opposite sides of the current collector 1. While one side of the current collector 1 may have multiple composite layers 2, the other side may or may not have composite layers 2. If composite layers 2 are present, they can be one or more. Here, the number of composite layers 2 refers to the number of composite layers 2 themselves, not the number of active material layers and absorbent layers 22 within the composite layer 2. For example, if the number of composite layers 2 is 2, it can be understood that when the composite layer 2 only includes the first active material layer 21 and the absorbent layer 22, the current collector 1 has 2 layers of the first active material layer 21 and 2 layers of the absorbent layer 22 on one side.

[0128] In this embodiment, multiple composite layers 2 are stacked on one side of the current collector 1. This results in at least a portion of the absorbent layers 22 located within the active material layer of the electrode 10. The active material layer can include multiple first active material layers 21, or multiple first active material layers 21 and multiple second active material layers 23. When the electrode 10 is applied to the battery 100, the excellent wetting ability of the absorbent layers 22 allows it to absorb and retain electrolyte when the battery 100 is not in operation. During charging and discharging of the battery 100, the absorbent layers 22 act as a small electrolyte source, continuously supplying electrolyte to the active material layer, significantly shortening the lithium ion migration path and reducing concentration polarization within the electrode 10. Furthermore, increasing the number of composite layers 2 can also improve the energy density of the battery 100.

[0129] Secondly, please see Figure 8 This application also provides a method for preparing electrode 10, comprising:

[0130] S01. A first active material layer 21 is prepared on the current collector 1. The first active material layer 21 has a first surface 211 away from the current collector 1, and a recess 212 extending from the first surface 211 into the interior of the first active material layer 21 is formed on the first active material layer 21.

[0131] S02. The first slurry is subjected to film formation treatment in the first surface 211 and the recess 212 of the first active material layer 21 to obtain the liquid-absorbing layer 22.

[0132] The electrode 10 provided in this application embodiment has a simple process and is easy to implement. When the prepared electrode 10 is applied to the battery 100, the electrode 10 is easily wetted by the electrolyte in the battery 100. The electrolyte can also quickly penetrate into the interior of the electrode 10 with the help of the recess 212 and the liquid absorption layer 22 on the electrode 10, shortening the lithium ion transport path, reducing the concentration polarization inside the electrode 10, and improving the rate performance of the battery 100.

[0133] In some implementations, please refer to Figure 8 Figure (a) Figure 8 In Figure (d), step S01, the process of preparing the first active material layer 21 on the current collector 1 includes:

[0134] S011. The second slurry is subjected to film formation treatment on the current collector 1 to obtain the first active material layer 21;

[0135] S012, Laser etching is performed on a portion of the first active material layer 21 from the side away from the current collector to create a recess 212.

[0136] By first preparing the first active material layer 21 and then laser etching the first active material layer 21 to obtain the recess 212, not only is the efficiency high, but the shape and size of the recess 212 are also easy to control.

[0137] In some embodiments, the recesses 212 may be formed simultaneously during the formation of the first active material layer 21. For example, the first active material layer 21 may be prepared by a double-layer coating method, and the recesses 212 may be formed on the first active material layer 21 during the forming process. Specifically, the recesses 212 are micropores.

[0138] In some implementations, please refer to Figure 8 Chinese (b) map ~ Figure 8 In Figure (c), step S011 involves forming a film from the second slurry on the current collector 1 to obtain the first active material layer 21, which includes:

[0139] S0111. A second slurry is coated on the current collector 1 to obtain a second wet film layer 21a. The second slurry includes a first active material, a second binder, a second conductive agent, and a second solvent.

[0140] S0112. The second wet film layer 21a is dried to evaporate the second solvent, thereby obtaining the first active material layer 21.

[0141] The above method for preparing the first active material layer 21 is simple and helps to control the production cost.

[0142] In some embodiments, during the preparation of the first active material layer 21, the method of coating the second slurry onto the current collector 1 includes, but is not limited to, at least one of gravure coating, microgravure coating, spraying, and electrospinning techniques. The first active material, the second binder, and the second conductive agent are as described in the first aspect. The second solvent can be selected according to the type of electrode 10 being prepared. As an example, when the electrode 10 is a positive electrode, the second solvent includes N-methylpyrrolidone (NMP), and when the electrode 10 is a negative electrode, the second solvent includes water.

[0143] In some embodiments, drying the second wet film layer 21a can be performed by drying the second wet film layer 21a in an oven. When the electrode 10 is a positive electrode, the drying temperature can be 40°C to 150°C; when the electrode 10 is a negative electrode, the drying temperature can be 20°C to 110°C.

[0144] In some embodiments, the first active material layer 21 can also be prepared by a layer coating method, in which the first active material layer 21 prepared in this way contains micropores, and the recess 212 includes micropores.

[0145] In some implementations, please refer to Figure 8(e) Figure Figure 8 In Figure (f), in step S02, the first slurry is subjected to a film-forming treatment within the first surface 211 and the recess 212 of the first active material layer 21 to obtain the liquid-absorbing layer 22, which includes:

[0146] S021. A first slurry is provided, the first slurry comprising a first solvent, a first conductive agent, and a first binder;

[0147] S022. The first slurry is coated on the inner surfaces of the first surface 211 and the recess 212 to obtain the first wet film layer 22a;

[0148] S023. The first wet film layer 22a is dried to evaporate the first solvent, thus obtaining the liquid-absorbing layer 22.

[0149] When the recess 212 is prepared by laser etching, there will be floating powder (i.e., residual micron-sized dust) on the surface of the first active material layer 21. Then, a first slurry is coated on the first surface 211 of the first active material layer 21 and the recess 212 to obtain a first wet film layer 22a. The first slurry includes a first solvent, a first conductive agent and a first binder. As a wet material, the first slurry has a certain fluidity. In this process, the first wet film layer 22a will not only cover the floating powder on the surface of the first active material layer 21, but also a small amount of the first slurry in the first wet film layer 22a will penetrate into the first active material layer 21. After that, the first slurry will dry, lose the first solvent and solidify to form a liquid-absorbing layer 22. In this way, the floating powder on the surface of the first active material layer 21 will also be solidified in the interface area where the liquid-absorbing layer 22 and the first active material layer 21 are combined, reducing the dust from detaching from the electrode 10 and entering the electrolyte, reducing the risk of dust adhering to the separator, and thus reducing the risk of short circuit in the battery 100.

[0150] In some embodiments, the method of coating the first slurry into the first surface 211 and recess 212 of the first active material layer 21 includes, but is not limited to, at least one of gravure coating, microgravure coating, spraying, and electrospinning techniques. Optionally, the first solvent includes at least one of water, N-methylpyrrolidone, ethylene glycol, and isopropanol. Optionally, the first binder includes at least one of carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and styrene-butadiene rubber (SBR). Optionally, the first conductive agent includes at least one of conductive carbon material and conductive ceramic. Optionally, the conductive carbon material includes at least one of carbon black, carbon nanotubes, carbon fibers, acetylene black, graphite, and graphene. Optionally, the carbon black includes at least one of conductive carbon black Super P, superconducting carbon black, and Ketjen black. Optionally, the carbon nanotubes include at least one of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs).

[0151] In some embodiments, the content of the first solvent in the first slurry is 10 wt% to 97 wt%. The content of the first solvent in the first slurry affects the forming effect of the first wet film layer 22a, and thus affects the absorbent layer 22. If the content of the first solvent in the first slurry is too high, the first slurry will easily drip, making it difficult to form the first wet film layer 22a. If the content of the first solvent is too low, the first slurry will have insufficient fluidity, affecting the uniformity and continuity of the first wet film layer 22a. As an example, the content of the first solvent in the first slurry is 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, or 97 wt%.

[0152] In some embodiments, the solid content in the first slurry is 3 wt% to 90 wt%. The solid content in the first slurry refers to the total content of substances other than the first solvent. If the solid content in the first slurry is too high, the first slurry will lack fluidity; if the solid content is too low, the first slurry will easily drip. As examples, the solid content in the first slurry is 3 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, or 90 wt%.

[0153] In some embodiments, the viscosity of the first slurry is between 10 cp and 15000 cp. The viscosity of the first slurry affects the thickness of the absorbent layer 22; the lower the viscosity of the first slurry, the thinner the absorbent layer 22 can be, and the higher the viscosity of the first slurry, the thicker the absorbent layer 22 can be. As examples, the viscosity of the first slurry is 10 cp, 100 cp, 500 cp, 1000 cp, 2000 cp, 3000 cp, 5000 cp, 8000 cp, 10000 cp, 12000 cp, or 15000 cp.

[0154] In some embodiments, the first slurry further includes a dispersant. The dispersant helps to improve the dispersion effect of the first conductive agent in the first solvent. Optionally, the dispersant includes at least one selected from acid anhydride, polyvinylpyrrolidone (PVP), sulfate salt, sulfonate, poly(N-vinylacetamide) (PNVA), polyvinyl alcohol (PVA), and polyethylene glycol.

[0155] In some embodiments, based on the total mass of the first conductive agent, the first binder, and the dispersant, the contents of the first conductive agent, the first binder, and the dispersant are as follows: 1 wt% to 60 wt% of the first conductive agent, 10 wt% to 99 wt% of the first binder, and 0 wt% to 30 wt% of the dispersant. As examples, the contents of the first conductive agent are 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 60 wt%; the contents of the first binder are 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or 99 wt%; and the contents of the dispersant are 0 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%.

[0156] In some embodiments, the first slurry can be prepared using a wet pulping method. Specifically, a first solvent, dispersant, and first binder are mixed in a mixing device to prepare a slurry, and then a first conductive agent is added and mixed to obtain the first slurry. The mixing device includes, but is not limited to, a mixer, a ball mill, a high-speed disperser, and a grinding mill. Alternatively, in some embodiments, the first solvent and first binder can be mixed in a mixing device to prepare a slurry, and then the first conductive agent and dispersant can be added and mixed to obtain the first slurry.

[0157] In some embodiments, the first slurry can also be prepared by dry mixing. Specifically, the first conductive agent, the first binder, and the dispersant are first mixed evenly in a mixing device, and then the first solvent is added and mixed to prepare the first slurry. Of course, in some embodiments, the first binder and the first solvent can be prepared into a binder solution, and the first conductive agent and the dispersant can be mixed evenly in a mixing device and then added to the binder solution to prepare the first slurry.

[0158] In some embodiments, the absorbent layer 22 is a conductive layer, and the first slurry includes a first solvent, a first conductive agent, and a first binder. As an example, the first wet film layer 22a can be dried in an oven at a temperature ranging from 20°C to 130°C. As an example, the drying temperature can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or 130°C.

[0159] In some implementations, please refer to Figure 8 The preparation method of electrode 10 also includes:

[0160] S03. Prepare a second active material layer 23 on the surface of the liquid-absorbing layer 22.

[0161] In some implementations, please refer to Figure 8 Chinese (g) diagram ~ Figure 8 Figure (h) shows the preparation process of the second active material layer 23, which includes:

[0162] S031. A third slurry is coated on the side of the liquid-absorbing layer 22 away from the current collector 1 to obtain a third wet film layer 23a. The third slurry includes a second active material, a third solvent, a third conductive agent and a third binder.

[0163] S032. The third wet film layer 23a is dried to evaporate the third solvent, thereby obtaining the second active material layer.

[0164] In the process of preparing the second active material layer 23 described above, the method of coating the third slurry onto the absorbent layer 22 includes, but is not limited to, at least one of gravure coating, microgravure coating, spray coating, and electrospinning techniques. The second active material, the third conductive agent, and the third binder are as described in the first aspect. The third solvent can be selected according to the type of electrode 10 being prepared. As an example, when the electrode 10 is a positive electrode, the third solvent includes N-methylpyrrolidone (NMP), and when the electrode 10 is a negative electrode, the third solvent includes water.

[0165] As an example, the third wet film layer 23a can be dried in an oven. When the electrode 10 is a positive electrode, the drying temperature can be 40℃~150℃; when the electrode 10 is a negative electrode, the drying temperature can be 20℃~110℃.

[0166] Thirdly, please see Figure 9 This application embodiment also provides a battery 100, which includes the aforementioned electrode 10.

[0167] The following description is based on specific embodiments.

[0168] Example 1

[0169] S1. Preparation of Electrode Slurry (Dry Mix): First, mix 12g of binder CMC with 738g of water to prepare a slurry. Then, take 960g of active material graphite and 13g of conductive agent conductive carbon black Super P (SP). Grind and mix the materials, add 262.5g of the slurry and 234g of water, knead, then add 487.5g of the slurry and 203.3g of water and stir. Finally, add 37.5g of SBR to obtain an electrode slurry with a solid content of 45.5wt%. Copper foil is used as the current collector, with a thickness of 6µm.

[0170] S2. Preparation of active material layer: The electrode paste is coated onto the current collector using a slot-die coating method. After passing through an oven, the electrode sheet is dried, and the electrode paste is cured to form an active material layer, which is then subjected to roll pressing.

[0171] S3. Etching Grooves: Grooves are etched into the active material layer using laser etching, with a laser etching power of 10W.

[0172] S4. Preparation of conductive paste: Grind and mix 58g of conductive carbon black, 30g of CMC+SBR, and 12g of PVP, then add them to 85g of water to prepare a conductive paste with a viscosity of 71cp.

[0173] S5. Preparation of conductive layer: The conductive paste is coated onto the active material layer obtained in step S3 using a gravure coating method. After passing through an oven, the electrode is dried, and the conductive paste is cured to form a conductive layer.

[0174] Example 2

[0175] The only difference from Example 1 is S4: Preparation of conductive paste: 62g of conductive carbon black, 28g of CMC+SBR, and 10g of PVP are ground and mixed and then added to 83g of water to prepare a conductive paste with a viscosity of 76cp.

[0176] Example 3

[0177] The only difference from Example 1 is in S4: Preparation of conductive slurry: 66g of conductive carbon black, 26g of CMC+SBR, and 8g of PVP are ground and mixed and then added to 80g of water to prepare a conductive slurry with a viscosity of 74cp.

[0178] Example 4

[0179] The only difference from Example 2 is that the amount of water used in S4 is 87g of water, and the viscosity of the prepared conductive paste is 63cp.

[0180] Example 5

[0181] The only difference from Example 2 is that the amount of water used in S4 is 82g of water, and the viscosity of the prepared conductive paste is 75cp.

[0182] Example 6

[0183] The only difference from Example 2 is that the amount of water used in S4 is 76g of water, and the viscosity of the prepared conductive paste is 89cp.

[0184] Example 7

[0185] The only difference from Example 1 is S4: Preparation of conductive paste: 30g of conductive carbon black, 5g of PAA and 5g of PVP are ground and mixed and then added to 88g of water to prepare a conductive paste with a viscosity of 25cp.

[0186] Example 8

[0187] The only difference from Example 7 is that the amount of water used in S4 is 75g of water, and the viscosity of the prepared conductive paste is 120cp.

[0188] Comparative Example 1

[0189] The only difference from Example 1 is the absence of steps S4 and S5.

[0190] Please refer to Table 1 for the formulation of the conductive paste in each embodiment.

[0191] Table 1

[0192]

[0193]

[0194] The electrode samples provided in Examples 1 to 8 and Comparative Example 1 were characterized as follows:

[0195] 1. Measurement of conductive layer thickness: The thickness of the samples before and after conductive layer coating was measured using a micrometer, and the difference was taken to obtain the thickness of the conductive layer. The results are recorded in Table 2. As can be seen from the results in Table 2, when the viscosity of the conductive slurry is similar (Examples 1 to 3 and Example 5), the thickness of the conductive layer is similar. However, as the solid content and viscosity of the conductive slurry increase (Examples 4, 2, 5, and 6), the thickness of the conductive layer increases.

[0196] Table 2

[0197] Group Conductive layer thickness / μm Example 1 1.45 Example 2 1.45 Example 3 1.45 Example 4 0.85 Example 5 1.50 Example 6 2.60 Example 7 0.6 Example 8 3.15 Comparative Example 1 0

[0198] 2. Morphology characterization: The electrode cross-section was cut using argon ion precision section cutting to obtain a flat cross-section. The cross-sectional morphology was then observed and the conductive layer thickness was measured using a scanning electron microscope (SEM).

[0199] like Figure 10 and Figure 11 The image shows SEM images of the electrode provided in Example 8 at different magnifications. As can be seen from the image, the conductive layer covers the surface of the active material layer and fills the grooves on the active material layer. The average thickness of the portion of the conductive layer covering the surface of the active material layer is 2.91 μm, and the thickness of the portion of the conductive layer filling the grooves is 6.85 μm.

[0200] like Figure 12 and Figure 13 The image shows SEM images of the electrode provided in Example 1 at different magnifications. As can be seen from the image, the conductive layer also covers the surface of the active material layer and fills the grooves on the active material layer. The average thickness of the part of the conductive layer covering the surface of the active material layer is 1.275 μm, and the thickness of the part of the conductive layer filling the grooves is 2.85 μm.

[0201] like Figure 14 The image shown is a SEM image of the electrode provided in Comparative Example 1. The area circled in the image is the area where the active material layer is etched. As can be seen from the image, the particles in the etched area on the electrode surface are relatively loose. This is because when the high-energy laser etches the active material layer, the binder is carbonized, and the active material and conductive agent in the active material layer are loosened to form micron-sized dust.

[0202] 3. The diffusion time of 1 mol / L LiPF6 electrolyte (solvent volume ratio EC:DMC:EMC = 1:1:1) on the electrode was measured using a contact angle meter, and process images were recorded using a high-speed camera. Specifically, the electrodes provided in Example 8 and Comparative Example 1 were tested respectively, and the results are as follows: Figure 15 and Figure 16 As shown in Table 3, tests were conducted at three different locations on each electrode. The time from when the electrolyte first dripped onto the electrode surface to when the electrolyte was completely absorbed by the electrode (contact angle no longer changing) was recorded. The average of the three test times was calculated as the electrolyte diffusion time on the electrode. The results are shown in Table 3. The data in Table 3 show that the electrolyte diffusion time on the active material layer was 28.583 s, while the diffusion time on the conductive layer was 12.173 s. This indicates that the conductive layer wets the electrolyte better, accelerating the electrolyte penetration rate within the electrode and reducing concentration polarization within the electrode.

[0203] Table 3

[0204]

[0205] 4. Electrode surface cleanliness test:

[0206] 4.1 Regarding Example 8, the cleanliness of the sample surface at different stages of electrode preparation was examined. The specific method was as follows: The electrode surface was wiped with clean latex gloves, and the dirt level at the contact points of the latex gloves with the electrode was observed. Specifically, for the sample provided in step S2 (i.e., the sample before etching the active material layer), no obvious stains were observed at the contact points of the latex gloves with the active material layer, indicating that there was very little powder on the active material layer before etching. For the sample provided in step S3 (i.e., the sample after etching the active material layer), obvious black stains were observed at the contact points of the latex gloves with the active material layer, indicating that there was significant powder buildup on the active material layer after etching. For the sample provided in step S5 (i.e., the sample after covering the active material layer with a conductive layer), no obvious stains were observed at the contact points of the latex gloves with the conductive layer, indicating that the powder buildup on the electrode surface was reduced after covering the active material layer with a conductive layer.

[0207] 4.2. The electrodes provided in Example 8 and Comparative Example 1 were wound around the diaphragm and then separated, and the cleanliness of the diaphragm surface was observed. The diaphragm surface around which the electrode provided in Comparative Example 1 was wound had obvious black dirt, while the diaphragm surface around which the electrode provided in Example 8 was wound was relatively clean. This indicates that the active material layer had severe powder floating after laser etching, and that the powder floating was significantly reduced after the active material layer was covered with a conductive layer after laser etching.

[0208] 5. Ratio Performance Test:

[0209] 5.1 Battery Preparation: Batteries were prepared using the electrodes provided in Example 8 and Comparative Example 1 as negative electrodes (referred to as Battery No. 1 and Battery No. 2 for easy distinction). The positive electrode, separator, and electrolyte of each battery were the same. The active material layer of the positive electrode included lithium cobalt oxide (97.6 wt%), PVDF (1.3 wt%), and SP (1.1 wt%). The separator was a polyethylene membrane, and the electrolyte was a 1 mol / L LiPF6 electrolyte (solvent volume ratio EC:DMC:EMC = 1:1:1).

[0210] 5.2 The rate performance of the prepared batteries was tested according to the following test methods:

[0211] (1) Let it sit for 3 minutes;

[0212] (2) Constant current and constant voltage charging: charge at 0.2C to 4.47V, and cut off at 0.02C;

[0213] (3) Let it sit for 5 minutes;

[0214] (4) Constant current discharge: Discharge to 2.75V at different test rates; the test rates are 0.2C, 0.5C, 1C, 1.5C, and 2C.

[0215] (5) Let it sit for 5 minutes;

[0216] (6) End, the battery capacity is obtained from the test;

[0217] (7) Compare the battery capacity obtained at different test rates with the battery capacity at a test rate of 0.2C to obtain the capacity retention rate at different test rates. The results are recorded in Table 4.

[0218] Table 4

[0219] Group 0.2 C discharge 0.5 C discharge 1 C discharge 1.5 C discharge 2 C discharge Example 8 100％ 97.6％ 95.5％ 92.4％ 74.5％ Comparative Example 1 100％ 97.7％ 94.2％ 82.9％ 63.2％

[0220] As can be seen from the results in Table 4, at low rates (0.2C, 0.5C), the capacity retention rates of battery No. 1 prepared by the electrode provided in Example 8 and battery No. 2 prepared by the electrode provided in Comparative Example 1 are close. As the rate increases, the capacity retention rate of battery No. 1 is higher than that of battery No. 2. Especially at high rates (1.5C, 2C), the capacity retention rate of battery No. 1 is significantly higher than that of battery No. 2, indicating that the setting of the conductive layer can significantly improve the rate performance of the battery.

[0221] 6. K-value test:

[0222] 6.1 Battery Preparation: Batteries were prepared using the electrodes provided in Example 8 and Comparative Example 1 as negative electrodes. The positive electrode, separator, and electrolyte of each battery were the same. The active material layer of the positive electrode included lithium cobalt oxide (97.6 wt%), PVDF (1.3 wt%), and SP (1.1 wt%). The separator was a polyethylene membrane, and the electrolyte was a 1 mol / L LiPF6 electrolyte (solvent volume ratio EC:DMC:EMC = 1:1:1).

[0223] 6.2 The K-value of the prepared batteries was tested according to the following test method: After the batteries were tested and left to stand at room temperature for 96±4h, the voltage U1 of OCV1 was obtained. After standing at room temperature for 48±4h (interval time t), the voltage U2 of OCV2 was obtained. The K-value was obtained by calculating (U1-U2) / t. The test results are recorded in Table 5.

[0224] Table 5

[0225] Group K value Example 8 0.0422 mV / h Comparative Example 1 0.0925 mV / h

[0226] The K-value of a battery refers to the voltage drop per unit time, usually expressed in mV / h, and is an indicator used to measure the self-discharge rate of a lithium battery.

[0227] As can be seen from the results in Table 5, the K value of Example 8 is significantly reduced compared to Comparative Example 1. This indicates that adding a conductive layer to the electrode after laser etching can cover the floating powder, reduce the risk of floating powder entering the electrolyte and separator, and thus significantly reduce the K value of the battery.

[0228] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An electrode sheet, characterized in that, include: current collector; A composite layer is disposed on the current collector. The composite layer includes a first active material layer and a liquid-absorbing layer disposed sequentially in a direction away from the current collector. The first active material layer has a first surface away from the current collector, and a recess extending from the first surface into the interior of the first active material layer is also formed on the first active material layer. The liquid-absorbing layer covers the first surface and the inner surface of the recess.

2. The electrode sheet according to claim 1, characterized in that, The recess includes at least one of a groove and a through hole.

3. The electrode sheet according to claim 2, characterized in that, The recess is an elongated groove that extends along a first direction of the first active material layer. The length of the groove extending in the first direction is less than or equal to the length of the first active material layer in the first direction.

4. The electrode sheet according to claim 1, characterized in that, Along the direction close to the current collector, the width of the recess remains unchanged or decreases.

5. The electrode sheet according to claim 4, characterized in that, The sidewall of the recess is a straight wall or a curved wall, or, if it is cut along the thickness direction of the first active material layer, the cross-section of the recess is V-shaped, trapezoidal, square, semi-circular or elliptical.

6. The electrode sheet according to claim 1, characterized in that, The number of recesses is multiple, and the multiple recesses are distributed at intervals, with the distance between two adjacent recesses being 0.01mm to 100mm; and / or, the depth of the recess is less than the thickness of the first active material layer; and / or, the average width of the recess is 1μm to 300μm.

7. The electrode sheet according to claim 1, characterized in that, The thickness of the liquid-absorbing layer is 0.2 μm to 50 μm; or, the thickness of the liquid-absorbing layer is 0.2 μm to 10 μm; or, the porosity of the liquid-absorbing layer is 5% to 99%.

8. The electrode sheet according to claim 1, characterized in that, The thickness of the first active material layer is greater than 30 μm; or, the thickness of the electrode is greater than 60 μm.

9. The electrode sheet according to claim 1, characterized in that, The porosity of the liquid-absorbing layer is at least greater than that of the first active material layer.

10. The electrode sheet according to claim 1, characterized in that, The recessed area is a laser-etched area.

11. The electrode sheet according to any one of claims 1 to 10, characterized in that, The composite layer further includes a second active material layer, which is disposed on the surface of the liquid-absorbing layer and faces away from the first active material layer.

12. The electrode sheet according to any one of claims 1 to 10, characterized in that, The number of composite layers on one side of the current collector is multiple, and the multiple composite layers are stacked together.

13. A battery, characterized in that, Includes the electrode sheet according to any one of claims 1 to 12.

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