Electrode sheet and method of making same, battery, and battery applications

Abstract

The application discloses an electrode sheet, a preparation method thereof, a battery and a battery application. The electrode sheet is prepared by separating an electrode active layer from a current collector, and combining a surface of the prepared electrode active layer, on which binder floating occurs during drying, with a surface of the current collector to form the electrode sheet. The content of the binder in the electrode active layer close to the surface layer of the current collector is higher than that of the electrode active layer far from the surface layer of the current collector. Therefore, the bonding strength between the electrode active layer and the current collector contained in the electrode sheet can be significantly reduced, and the phenomenon of the electrode active layer falling off and dropping off and other adverse phenomena can be reduced, so that the cycle performance of the electrode sheet and the battery can be obviously improved.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to an electrode sheet and its preparation method, a battery, and battery applications. Background Technology

[0002] Lithium-ion batteries have rapidly gained popularity in automotive power supplies, 3C electronic products, and energy storage devices due to their advantages such as high energy density and low self-discharge. With the widespread application of lithium batteries, the requirements for their electrochemical performance, such as cycle performance and production efficiency, are receiving increasing attention.

[0003] Electrode sheets are one of the most important components in a battery, typically consisting of a current collector and an active electrode layer bonded to the current collector. Therefore, the quality of the electrode sheet is a key factor affecting the improvement of the battery's electrochemical performance. However, due to current electrode sheet manufacturing processes, during the drying process, the binder in the active electrode layer migrates to the surface of the active electrode layer along with the solvent through capillary force, resulting in binder floating on the surface. This affects various aspects of the electrode sheet's performance, and thus at least the battery's electrochemical performance. Summary of the Invention

[0004] In view of the above problems, this application provides an electrode sheet, a method for preparing the same, a battery, and a battery application. This technology can solve the problem of the degradation of electrode sheet and battery-related performance caused by the floating of binder in the electrode active layer of the electrode sheet.

[0005] In a first aspect, embodiments of this application provide a method for preparing an electrode sheet. The method for preparing the electrode sheet according to embodiments of this application includes the following steps:

[0006] A substrate and a current collector are provided, wherein the substrate has a release surface;

[0007] An electrode active layer is prepared on the release surface of the substrate;

[0008] A conductive adhesive layer is formed on the surface of the current collector and / or the surface of the electrode active layer facing away from the substrate;

[0009] The surface of the electrode active layer facing away from the substrate is laminated and bonded to the surface of the current collector to obtain a composite film.

[0010] During or after the lamination and bonding process, the substrate and the electrode active layer are separated to obtain an electrode sheet.

[0011] In the electrode sheet preparation method of this application embodiment, the content of binder on the side of the electrode active layer near the current collector is higher than that on the side away from the current collector. This significantly enhances the bonding strength between the electrode active layer and the current collector, significantly enhances the structural strength of the electrode sheet, and significantly reduces the occurrence of adverse phenomena such as powder shedding and material loss in the electrode active layer, thereby significantly improving the cycle performance of the electrode sheet and the battery.

[0012] In some embodiments, the release force of the release surface is 800–1200 gf / 25 mm. By selectively controlling the release force of this release surface, the quality of the prepared electrode active layer can be effectively improved, and the efficiency of the separation process between the electrode active layer and the substrate can be increased, reducing adverse effects such as damage to the electrode active layer during the separation process, thereby improving the quality of the prepared electrode sheet.

[0013] In some embodiments, the release surface is coated with a release agent.

[0014] In the example, the release agent includes at least one of a silicone release agent and an alkane-based non-silicone release agent.

[0015] By applying a release agent to the release surface, or by further selecting and controlling the type of release agent, the release surface can be given good release properties, and the quality of the prepared electrode active layer can be improved.

[0016] In some embodiments, the substrate is a film that can be wound up. This film allows for both unwinding and winding of the substrate, enabling continuous fabrication of the electrode active layer, thereby effectively improving the fabrication efficiency of the electrode active layer.

[0017] In some embodiments, when the substrate is a film suitable for winding, the film thickness is 20–100 μm, optionally 30–50 μm. This thickness range allows for effective unwinding and winding, and more importantly, provides good mechanical properties, improving the quality and thickness of the prepared electrode active layer.

[0018] In some embodiments, the thickness of the electrode active layer is 50–250 μm, and optionally 80–200 μm.

[0019] In some embodiments, the electrode active layer is a negative electrode active layer.

[0020] The electrode active layer prepared on the substrate, such as including the negative electrode active layer, can be controlled to have a relatively large thickness, thereby significantly improving the energy density of the battery.

[0021] In this embodiment, the current collector is a negative electrode current collector, and the thickness of the negative electrode current collector is 4–6 μm. Within this thickness range of the negative electrode current collector, the negative electrode active layer can be made thicker than the negative electrode active layer contained in a conventional negative electrode sheet, such as controlling the thickness of the negative electrode active layer to be 50–250 μm as mentioned above. This improves the energy density of the negative electrode sheet.

[0022] In some embodiments, the thickness of the formed conductive adhesive layer is 1–3 μm.

[0023] In some embodiments, the conductive adhesive used to form the conductive adhesive layer includes at least one of conductive voltage-sensitive adhesive, conductive acrylate adhesive, conductive polyurethane adhesive, and conductive polyimide resin adhesive.

[0024] These conductive adhesive layers and the conductive adhesives they contain have strong adhesion and good conductivity, which can improve the structural strength and cycle performance of the electrode sheet, and reduce internal resistance.

[0025] In some embodiments, the lamination bonding process includes a pressing step of bonding the composite film. This pressing process makes the electrode active layer and the current collector more firmly laminated under the action of the conductive adhesive layer, thereby enhancing the lamination bond strength between the electrode active layer and the current collector and improving the structural strength and cycle life of the electrode sheet.

[0026] In the embodiments, the pressing process of the composite film includes at least one of the following conditions (1) to (3):

[0027] (1) The pressure is 0.3-5 MPa, and can be selected as 0.5-3 MPa;

[0028] (2) The temperature is 10 to 100℃, and can be selected as 20 to 75℃;

[0029] (3) The pressing process is a roller pressing process.

[0030] In this embodiment, the conductive adhesive layer is a voltage-sensitive adhesive layer.

[0031] By controlling at least one of (1) to (3) of the pressing process above, the strength of the lamination bond between the electrode active layer and the current collector can be enhanced, thereby improving the structural strength and recyclability of the electrode sheet. When roll pressing is used, continuous production of the electrode sheet can be achieved, improving the production efficiency of the electrode sheet.

[0032] Secondly, embodiments of this application also provide an electrode sheet. The electrode sheet of this application includes a current collector and an electrode active layer bonded to the current collector. The electrode active layer contains a binder, and a conductive adhesive layer is stacked between the electrode active layer and the current collector. Furthermore, in the electrode active layer, the content of the binder on the side closer to the current collector is higher than the content of the binder on the side away from the current collector.

[0033] The binder distribution in the electrode active layer of the electrode sheet in this embodiment can synergistically enhance the bonding strength between the electrode active layer and the current collector surface, thereby significantly improving the cycle performance of the electrode sheet. Furthermore, it can significantly improve the electrolyte wettability of the electrode active layer.

[0034] In some embodiments, the thickness of the electrode active layer is 50–250 μm, and optionally 80–200 μm.

[0035] In some embodiments, the electrode active layer is a negative electrode active layer.

[0036] In the embodiments of this application, the electrode active layer, such as the negative electrode active layer, can be controlled to have a relatively large thickness, thereby significantly improving the energy density of the battery.

[0037] In some embodiments, the current collector is a negative electrode current collector, and the thickness of the negative electrode current collector is 4 to 6 μm.

[0038] When the electrode sheet in the embodiments of this application is a negative electrode sheet, the thickness of the negative electrode current collector contained therein is within this thickness range. The negative electrode active layer can be made thicker than the negative electrode active layer contained in a conventional negative electrode sheet, such as controlling the thickness of the negative electrode active layer to be 50-250 μm as mentioned above. This improves the energy density of the negative electrode sheet.

[0039] In some embodiments, the thickness of the conductive adhesive layer is 0.3–3 μm, and optionally 0.5–1.5 μm.

[0040] In some embodiments, the film resistance of the conductive adhesive layer is 0.001 to 0.1 Ω, and may be selected as 0.001 to 0.01 Ω.

[0041] The conductive adhesive layer within this thickness range effectively improves the strength of the laminated bond between the active electrode layer and the current collector, while also reducing the resistance at the interface between the active electrode layer and the current collector.

[0042] Thirdly, embodiments of this application also provide a battery. The battery of this application embodiment includes electrodes, which are electrode sheets prepared by the electrode sheet preparation method of the above-described application embodiments or electrode sheets of the above-described application embodiments.

[0043] The battery in this application exhibits good cycle performance. Furthermore, it also possesses high energy density and high rate capability.

[0044] In some embodiments, the battery includes any one of a battery cell, a battery module, or a battery pack.

[0045] Fourthly, embodiments of this application also provide an electrical device. The electrical device of this application includes a power supply unit or an energy storage unit, wherein the power supply unit or energy storage unit contains a battery, and the battery includes the battery described in the embodiments of this application above. The power supply unit or energy storage unit of the electrical device of this application has good cycle performance, long service life, and can also have high energy density and other properties.

[0046] Fifthly, embodiments of this application also provide an energy storage device, including an energy storage unit containing a battery, the battery including the battery described in the above-described embodiments. The energy storage device exhibits good cycle performance, long service life, and further high energy density.

[0047] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0048] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0049] Figure 1 This is a flowchart illustrating the preparation method of electrode sheets for some embodiments of this application;

[0050] Figure 2 This is a flowchart illustrating the preparation method of electrode sheets in some embodiments of this application, and a schematic diagram illustrating the component structure prepared in each step.

[0051] Figure 3 This is a schematic diagram of the structure of the electrode sheet in some embodiments of this application;

[0052] Figure 4 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application;

[0053] Figure 5 for Figure 4 The diagram shows an exploded view of a single battery cell.

[0054] Figure 6This is a schematic diagram of one embodiment of the battery module of this application;

[0055] Figure 7 This is a schematic diagram of one embodiment of the battery pack of this application;

[0056] Figure 8 for Figure 7 The diagram shows the exploded structure of the battery pack.

[0057] Figure 9 This is a schematic diagram of one embodiment of an electrical device that uses a battery as a power source, as described in the present application.

[0058] The reference numerals in the detailed embodiments are as follows:

[0059] 10-Substrate, 11-Release surface, 12-Conductive adhesive layer;

[0060] 20-Electrode sheet, 21-Current collector, 22-Electrode active layer, 23-Conductive adhesive layer; 221-Surface, 222-Adhesive;

[0061] 30-Battery cell, 31-Casing, 32-Electrode assembly, 33-Cover plate;

[0062] 40 - Battery Module;

[0063] 50 - Battery pack, 51 - Housing, 52 - Lower housing. Detailed Implementation

[0064] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0066] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0067] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0068] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0069] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0070] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0071] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0072] With the rapid popularization of lithium batteries, especially in electric vehicles, the requirements for their electrochemical performance, such as cycle performance, are becoming increasingly stringent. The electrode structure typically includes a current collector and an active electrode layer bonded to the current collector. Therefore, the electrode is a crucial component of the battery, providing the active material for battery chemical reactions and transporting electrons.

[0073] The current electrode fabrication process typically involves coating a slurry containing electrode active materials, conductive agents, binders, and solvents onto the surface of the current collector, followed by drying and rolling. The purpose of drying is primarily to remove the solvent from the slurry. However, during drying, the solvent migrates and evaporates towards the electrode surface via capillary forces. The binder, being relatively lightweight, easily migrates and accumulates towards the surface of the electrode active layer along with the solvent, leading to binder floating. This floating phenomenon results in a higher binder content on the surface of the electrode active layer compared to the side closer to the current collector. This not only blocks the pores of the electrode active layer surface, reducing its wetting effect, but also reduces the adhesion between the electrode active layer and the current collector due to the lower binder content on the side closer to the current collector. This reduces the structural stability of the electrode and makes it prone to defects such as powder shedding and material loss. Furthermore, it increases the likelihood of edge burrs during subsequent slitting. Ultimately, this affects the electrochemical performance of the battery, including cycle performance.

[0074] To alleviate or resolve the issue of binder floating in the active layer of an electrode sheet, related technologies generally involve replacing the binder or controlling the electrode active layer process, such as using multiple film deposition to create a multi-layer structure for the active layer. However, these methods still cannot effectively control the binder floating phenomenon and can also complicate the electrode sheet manufacturing process, leading to a decrease in electrode sheet yield and an increase in production costs.

[0075] To alleviate or overcome the phenomenon of binder floating in the active layer of the electrode sheet, an improvement to the conventional electrode sheet manufacturing process is made. The active layer is first prepared separately, and then flipped. Specifically, the surface of the active layer with high binder content is laminated with the current collector. By preparing the active layer separately and then flipping it to laminate with the current collector, the binder content on the surface of the active layer (the side facing away from the current collector) is effectively ensured to be lower than that on the side closer to the current collector. This results in good electrolyte wettability on the surface of the active layer (the side facing away from the current collector) and effectively improves the bonding strength between the active layer and the current collector. This significantly reduces the occurrence of defects such as powder shedding and material loss, significantly improves the battery's cycle performance and other electrochemical performance, and also effectively increases the production efficiency of the electrode sheet. Based on the above research, the embodiments of this application propose the following technical solutions.

[0076] Electrode preparation method

[0077] Firstly, embodiments of this application provide a method for preparing an electrode sheet. In some embodiments, the process flow of the electrode sheet preparation method provided by this application is as follows: Figure 1 and Figure 2 As shown, the preparation method of the electrode sheet 20 provided in this embodiment includes the following steps:

[0078] S10: Provides a substrate 10 with a release surface 11 and a current collector 21;

[0079] S20: Prepare an electrode active layer 22 on the release surface 11 of the substrate 10;

[0080] S30: A conductive adhesive layer 12 is formed on the surface of the current collector 21 and / or on the surface 221 of the electrode active layer 22 that is away from the substrate 10;

[0081] S40: The surface 221 of the electrode active layer 22 facing away from the substrate 10 is laminated and bonded to the surface of the current collector 21 to obtain a composite film;

[0082] S50: During or after the lamination bonding process, the substrate 10 and the electrode active layer 22 are separated to obtain the electrode sheet 20.

[0083] In step S10, the release surface 11 of the substrate 10 refers to the surface that is easily separated from the electrode active layer 22 formed on its surface in step S20, and its function is the same as that of the release film surface. The electrode active layer 22 in step S20 refers to the conventionally understood positive or negative electrode active layer, such as an electrode active material layer including electrode active material, conductive agent, and binder. The lamination and bonding treatment of the electrode active layer 22 and the current collector 21 refers to bonding the electrode active layer 22 and the current collector 21 together using the conductive adhesive layer 12 in step S30. The separation treatment of the substrate 10 and the electrode active layer 22 in step S50 refers to peeling or separating the substrate 10 from the surface of the electrode active layer 22.

[0084] Therefore, the method for preparing the electrode sheet 20 in this embodiment involves preparing the electrode active layer 22 separately, then flipping it over and layering it onto the surface of the current collector 21 to form the electrode sheet 20. Thus, in the prepared electrode sheet 20, the side of the electrode active layer 22 closest to the current collector 21 (i.e., the side where the adhesive floats and accumulates) contains adhesive 222 (such as... Figure 2 The content of (as shown) is higher on the side away from the current collector 21. This significantly enhances the bonding strength between the electrode active layer 22 and the current collector 21, significantly enhances the structural strength of the electrode sheet 20, and significantly reduces the occurrence of adverse phenomena such as powder shedding and material loss in the electrode active layer 22. This can significantly improve the cycle performance of the electrode sheet 20 and the battery.

[0085] Based on the high structural strength of the prepared electrode sheet 20, the preparation method of the electrode sheet 20 in this embodiment involves preparing the electrode active layer 22 separately from the current collector 21. This allows for the separate preparation or other processing of the electrode active layer 22 and the current collector 21, significantly improving the preparation efficiency of the electrode sheet 20. Simultaneously, by flipping the electrode active layer 22 onto the current collector 21 as described in step S40, the complex production process, low yield, and high production cost associated with multi-layer preparation of the electrode active layer to reduce binder floating are avoided. Therefore, while improving the production efficiency of the electrode sheet 20, the yield of the electrode sheet 20 is also increased.

[0086] Step S10:

[0087] The substrate 10 provided in step S10 is as follows Figure 2 As shown in Figure A, the provided current collector 21 is as follows Figure 2 As shown in Figure B.

[0088] The substrate 10 in step S10 serves as the substrate for the electrode active layer 22 prepared in step S20, and can also be referred to as a carrier. Therefore, any substrate having a release surface 11 is within the scope of the embodiments disclosed in this application.

[0089] In this embodiment, the substrate 10 can be a film that can be wound up. This allows for substrate unwinding and winding, enabling continuous fabrication of the electrode active layer 22 in step S20, thereby effectively improving the fabrication efficiency of the electrode active layer 22.

[0090] In the embodiments, when the substrate 10 can be a film suitable for winding, the thickness of the film can be 20–100 μm, optionally 30–50 μm. Typical but not uniquely limited thickness ranges include 20–30 μm, 30–40 μm, 40–50 μm, 50–60 μm, 60–70 μm, 70–80 μm, 80–90 μm, and 90–100 μm. This thickness range allows for effective unwinding and winding, and more importantly, provides good mechanical properties, improving the quality and thickness of the electrode active layer 22 prepared in step S20. The thickness of the substrate 10 film is the distance between one surface and the opposite surface. The thicknesses of the components mentioned below, such as the current collector 21, the electrode active layer 22, the conductive adhesive layer 23, and the conductive adhesive layer 12, are all distances between one surface and the opposite surface.

[0091] In the example, the substrate 10 can be an organic film, such as any one of PET film, PI film, etc., or a composite film of two or more materials contained in the film layers.

[0092] In step S10, the release surface 11 of the substrate 10 not only enables the electrode active layer 22 to be prepared on its surface in step S20, but also enables the electrode active layer 22 to be released and separated, that is, it is separated from the electrode active layer 22 during the separation process in step S50.

[0093] In this embodiment, the release force of the release surface 11 of the substrate 10 can be 800–1200 gf / 25 mm. In exemplary cases, typical but not uniquely limiting release force ranges include 800–850 gf / 25 mm, 850–900 gf / 25 mm, 900–950 gf / 25 mm, 950–1000 gf / 25 mm, 1000–1050 gf / 25 mm, 1050–1100 gf / 25 mm, 1100–1150 gf / 25 mm, and 1150–1200 gf / 25 mm. By selectively controlling the release force of the release surface 11, the quality of the electrode active layer 22 prepared in step S20 can be effectively improved, and the efficiency of the separation process in step S50 can also be increased. This reduces adverse effects on the electrode active layer 22 during the separation process, including damage, thereby improving the quality of the prepared electrode sheet 20. The release force data was obtained by testing using the TESA 7475 TAPE method (the same test method was used for the release force data below). Specifically, a TESA 7475 test tape with a length of 200 mm and a width of 25 mm was attached to the release surface 11 of the substrate 10, and then rolled back and forth three times with its own weight using a 25 kg pressure roller. After being placed under the test conditions for 20 minutes, it was peeled off using a tensile tester at 300 mm / min and 180°, and the average value of 8 values ​​was taken.

[0094] In this embodiment, the release surface 11 of the substrate 10 is coated with a release agent. In an exemplary embodiment, the release agent may include at least one of a silicone-containing release agent and an alkane-based non-silicone release agent. The silicone-containing release agent generally refers to an organosilicon release agent. In an exemplary embodiment, the organosilicon release agent may include release agents such as polydimethylsiloxane (PDMS), methylsilicone oil, silane coupling agent, polydimethylsiloxane, and hydrogenated polydimethylsiloxane. Alkane-based non-silicone release agents include fatty alcohol polyoxyethylene ethers (such as dodecyl alcohol polyoxyethylene ether), fatty acid polyoxyethylene esters (such as dodecyl acid polyoxyethylene ester), fatty alcohol polyoxypropylene ethers (such as dodecyl alcohol polyoxypropylene ether), fatty acid polyoxypropylene esters (such as dodecyl acid polyoxypropylene ester), fatty alcohol polyethylene ethers (such as dodecyl alcohol polyethylene ether), fatty acid polyethylene esters (such as dodecyl acid polyethylene ester), fatty alcohol polypropylene ethers (such as dodecyl alcohol polypropylene ether), and fatty acid polypropylene esters (such as dodecyl acid polypropylene ester).

[0095] By applying a release agent to the release surface 11, or by further selecting and controlling the type of release agent, the release surface 11 can be given good release properties, and the quality of the prepared electrode active layer 22 can be improved. Furthermore, the amount of release agent applied to the release surface 11, such as the content of release agent per unit area, can be controlled to adjust the release force of the release surface 11. For example, the release force of the release surface 11 can be adjusted to between 800 and 1200 gf / 25 mm as described above.

[0096] The current collector 21 provided in step S10 can be either a positive or negative current collector. In this embodiment, the current collector 21 includes, but is not limited to, metal current collectors, carbon current collectors, conductive resin current collectors, and composite current collectors of metal and resin, and more specifically, materials such as copper, nickel, titanium, iron and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), and graphite. The specific material can be flexibly selected based on the positive or negative polarity of the electrode sheet 20.

[0097] Since the electrode active layer 22 of the prepared electrode sheet 20 is first formed on the substrate 10, when the current collector 21 is within the conventional current collector thickness range, the electrode active layer 22 can be thicker than the electrode active layer of a conventional electrode sheet. This effectively improves the energy density (e.g., gravimetric energy density) of the prepared electrode sheet 20. When the electrode active layer 22 is a negative electrode active layer, the thickness of this negative electrode active layer can be controlled within the range of 50–250 μm in step S20. This further improves the energy density of the negative electrode sheet and the battery.

[0098] Of course, the preparation method of this application embodiment can also have lower requirements for the mechanical properties of the current collector 21 compared to the current collector contained in a conventional electrode sheet. Therefore, in the embodiments, the thickness of the current collector 21 prepared by the method of this application embodiment can be thinner than that of the current collector contained in a conventional electrode sheet. For example, in the embodiments, when the current collector 21 is a negative electrode current collector, the thickness of the negative electrode current collector can be controlled to be 4-6 μm. In the exemplary examples, it can be a typical but not unique limiting thickness such as 4-4.5 μm, 4.5-5 μm, 5-5.5 μm, 5.5-6 μm. Of course, the thickness of the negative electrode current collector can also be adjusted to be relatively lower. Similarly, when the current collector 21 is a positive electrode current collector, the thickness of the positive electrode current collector can also be significantly reduced. In this way, the thickness of the current collector 21 contained in the electrode sheet 20 can be effectively reduced, and the thickness of the electrode active layer 22 can be increased accordingly, thereby significantly improving the energy density of the electrode sheet 20 and the battery.

[0099] Step S20:

[0100] After the electrode active layer 22 is prepared on the release surface 11 of the substrate 10 in step S20, in one embodiment, the composite structure formed by the electrode active layer 22 and the substrate 10 is as follows: Figure 2 As shown in Figure C. Of course, when the substrate 10 has two release surfaces 11 arranged opposite to each other, the electrode active layer 22 can be prepared on both release surfaces 11.

[0101] In step S20, the electrode active layer 22 is prepared on the release surface 11 using conventional methods for preparing electrode active layers. The difference is that conventional methods prepare the electrode active layer on the current collector surface, while in the electrode sheet preparation method of this application, the electrode active layer is prepared on the release surface 11 of the substrate 10. Alternatively, the electrode active layer can be prepared using a modified method of the conventional electrode active layer method, or a new method can be employed. As long as the electrode active layer is prepared on the release surface 11 of the substrate 10, it falls within the scope of the description in this application.

[0102] Furthermore, the structure of the prepared electrode active layer 22 can be a single-layer electrode active layer or a composite structure electrode active layer formed by multiple layers stacked together. Based on the preparation method of the electrode sheet 20 in this application embodiment, the electrode active layer 22 can be a single layer, which still ensures that the content of binder 222 on the side of the electrode active layer 22 near the current collector 21 is higher than the content of binder 222 on the side away from the current collector 21. Figure 2 E to G diagrams and Figure 3 As shown. This can significantly improve the preparation efficiency of the electrode active layer 22 while enhancing the structural strength and cycle performance of the prepared electrode sheet 20.

[0103] The method for preparing the electrode active layer 22 may include: preparing a slurry containing electrode active material, binder 222, solvent, or further containing conductive agent, other additives, etc.; forming the slurry on the release surface 11 of the substrate 10 (wet film); then drying the film to allow the solvent to evaporate; and finally rolling the dried film to form the electrode active layer 22.

[0104] Since the slurry contains solvent, the solvent will gradually evaporate during the drying process of the wet film. The organic binder is an organic substance, which is a light component and may be miscible with the solvent. Therefore, as the solvent gradually evaporates and the binder migrates from the interior to the surface of the wet film, it also migrates and aggregates along with the solvent towards the surface. Thus, similar to conventionally prepared electrode active layers, the electrode active layer 22 prepared in step S20 also exhibits a binder floating phenomenon. Specifically, as shown in... Figure 2 As shown in Figure C, in the surface layer of the electrode active layer 22 away from the substrate 10, that is, in the surface layer of the electrode active layer 221, the content of binder 222 is higher than that in the surface layer near the substrate 10.

[0105] Furthermore, since the electrode active layer 22 is prepared on the release surface 11 of the substrate 10, the mechanical properties of the substrate 10 can be enhanced by controlling factors such as the thickness and material of the substrate 10. This allows for effective control of the thickness of the prepared electrode active layer 22, potentially significantly increasing its thickness. In some embodiments, the thickness of the prepared electrode active layer 22 can be controlled to be 50–250 μm, optionally 80–200 μm. Typical but not uniquely limiting thickness ranges include 50–80 μm, 80–100 μm, 100–120 μm, 120–150 μm, 150–180 μm, 200–220 μm, and 220–250 μm. Therefore, the electrode active layer 22 prepared on the substrate 10 in step S20 can be controlled to have a relatively large thickness, thereby significantly improving the energy density of the electrode sheet and the battery. In addition, since the upper limit of the thickness of the electrode active layer 22 is relatively high, the thickness of the electrode active layer 22 can be flexibly adjusted and controlled within a relatively wide range according to production needs.

[0106] The electrode active layer 22 prepared in step S20 can be either a positive or negative electrode active layer. In the embodiment, when the electrode active layer 22 is a negative electrode active layer, its thickness can be 50–250 μm, optionally 80–200 μm. Since conventional negative electrode current collectors, such as copper foil, are generally thin, preparing the negative electrode active layer on the surface of the current collector, as is the conventional method, results in a thinner negative electrode active layer, thus limiting the improvement of the battery's energy density. However, in the preparation method of this application embodiment, since the electrode active layer 22 is prepared on the release surface 11 of the substrate 10, the negative electrode active layer can be prepared to be relatively thick. Compared to conventional methods that directly prepare the negative electrode active layer on the current collector, the thickness of the negative electrode active layer prepared by the method of this application embodiment can be increased by 30%–50%, thus significantly improving the energy density of the electrode sheet and the battery.

[0107] Furthermore, since the electrode active layer 22 is prepared on the release surface 11 of the substrate 10 and then transferred and bonded to the current collector 21 in step S40, the thickness requirement of the current collector 21 in the preparation method of this application embodiment can be reduced, such as the thickness requirement described in step S10.

[0108] In the embodiments, when the electrode active layer 22 prepared in step S20 is a negative electrode active layer, the negative electrode active material contained in the negative electrode active layer may include one or more of carbon-based active materials, titanium-based active materials, silicon-based active materials, nitrides, and lithium metal. In the exemplary examples, the carbon-based materials may include one or more of graphite, hard carbon, soft carbon, mesophase carbon microspheres, and graphene; in the exemplary examples, the titanium-based active materials may include one or more of lithium titanate and titanium dioxide; in the exemplary examples, the silicon-based active materials may include one or more of silicon and silicon dioxide; and in the exemplary examples, the nitrides may include lithium nitride.

[0109] In this embodiment, when the electrode active layer 22 prepared in step S20 is a positive electrode active layer, the positive electrode active material contained in the positive electrode active layer may include one or more of metal inorganic active materials and organic active materials. In an exemplary example, the metal inorganic active material may include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese iron phosphate, and lithium nickel cobalt aluminum oxide. In an exemplary example, the organic active material may include one or more of quinone compounds, carboxylate compounds, acid anhydride compounds, and amide compounds.

[0110] In the embodiments, the binder 222 contained in the electrode active layer 22 prepared in step S20 may include one or more of oil-soluble binders, water-soluble binders, and emulsion binders. In the exemplary examples, the oil-soluble binder may include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, and polyacrylonitrile; in the exemplary examples, the water-soluble binder may include one or more of carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinyl alcohol, sodium alginate, and cyclodextrin; in the exemplary examples, the emulsion binder may include one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0111] In the embodiments, when the electrode active layer 22 prepared in step S20 contains a conductive agent, the conductive agent may include one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, graphene, etc.

[0112] In the embodiments, when the electrode active layer 22 prepared in step S20 contains other additives, the additives may include, but are not limited to, functional components such as lithium supplementation.

[0113] The specific materials, such as the positive electrode active material, negative electrode active material, binder 222, and conductive agent, can be selected according to the application or production requirements of the electrode sheet 20.

[0114] Step S30:

[0115] The conductive adhesive layer 12 formed in step S30 can be formed on the surface 221 of the electrode active layer 22 that is away from the substrate 10, which is prepared in step S20, or it can be formed on the surface of the current collector 21 provided in step S20. Of course, the conductive adhesive layer 12 can be formed on both the surface 221 of the electrode active layer 22 and the surface of the current collector 21.

[0116] When a conductive adhesive layer 12 is formed on the surface of the current collector 21, in one embodiment, the composite structure formed by the conductive adhesive layer 12 and the current collector 21 is as follows: Figure 2 As shown in Figure D. Of course, conductive adhesive layers 12 can be formed on both opposite surfaces of the current collector 21.

[0117] In this embodiment, the thickness of the formed conductive adhesive layer 12 can be 1–3 μm. This thickness range of conductive adhesive layer 12 effectively achieves the lamination and bonding of the electrode active layer 22 and the current collector, and improves the structural strength of the prepared electrode sheet 20. Of course, the thickness of the conductive adhesive layer 12 can be adjusted to other thickness ranges according to production requirements.

[0118] In this embodiment, the conductive adhesive used to form the conductive adhesive layer 12 includes at least one of conductive voltage-sensitive adhesive, conductive acrylate adhesive, conductive polyurethane adhesive, and conductive polyimide resin adhesive. In the exemplary example, the conductive acrylate adhesive refers to a mixture of acrylate adhesive and a conductive agent; the conductive polyurethane adhesive refers to a mixture of polyurethane adhesive and a conductive agent; and the conductive polyimide resin adhesive refers to a mixture of polyimide resin adhesive and a conductive agent. The conductive agent may include, but is not limited to, metal particles, conductive carbon, etc. These conductive adhesives have strong adhesion and good conductivity, which can improve the structural strength and cycle performance of the electrode sheet, and reduce internal resistance.

[0119] The conductive adhesive layer 12 can be formed by, but is not limited to, brushing, rolling, spraying, etc.

[0120] Step S40:

[0121] After bonding the electrode active layer 22 and the current collector 21 according to the requirements of the lamination and bonding process in step S40, a composite film is formed. In one embodiment, the structure of the formed composite film is as follows: Figure 2 Figures E and F are shown in the diagram. Figure E shows the composite film structure in which the electrode active layer 22 and the current collector 21 are laminated and bonded according to the requirements of the laminated bonding process. Figure F shows the composite film structure after the conductive adhesive layer 12 is pressed or cured based on the structure shown in Figure E.

[0122] Alternatively, the electrode active layer 22 can be laminated and bonded on both opposite surfaces of the current collector 21, so that in the composite film, the electrode active layer 22 is laminated and bonded on both opposite surfaces of the current collector 21 through the conductive adhesive layer 12.

[0123] Therefore, after the lamination and bonding process in step S40, the outer surface of the electrode active layer 22 prepared in step S20 becomes the inner surface of the electrode active layer 22 contained in the electrode sheet 20; at the same time, the conductive adhesive layer 12 becomes as shown in the image. Figure 2 The conductive adhesive layer 23 is shown in Figure F. At this time, the surface 221 of the electrode active layer 22 is close to the current collector 21. That is, after the electrode active layer 22 is bonded to the current collector 21, the surface layer where the adhesive 222 floats up and accumulates during the drying process is close to the surface of the current collector 21. In this way, the strength of the laminated bond between the electrode active layer 22 and the current collector is effectively enhanced, and the structural strength of the prepared electrode sheet 20 is improved. The surface layer of the electrode active layer 22 near the substrate 10 is far from the surface of the current collector 10. Due to the migration of the adhesive 222, the content of the adhesive 222 in this surface layer is low, thus having a rich porous structure. When the substrate 10 is separated in step S50, this surface layer with low adhesive 222 content has excellent electrolyte wetting efficiency.

[0124] In some embodiments, the lamination bonding process in step S40 includes a pressing process for the composite film. The pressing process involves applying pressure to the two opposing surfaces of the composite film. Under this external pressure, the electrode active layer 22 and the current collector 21 are more firmly laminated under the action of the conductive adhesive layer 12, thereby enhancing the lamination bond strength between the electrode active layer 22 and the current collector 21 and improving the structural strength and cycle life of the electrode sheet 20.

[0125] In the embodiments, the pressing process of the composite film includes at least one of the following conditions (1) to (3):

[0126] (1) The pressure is 0.3 to 5 MPa, and can be selected as 0.5 to 3 MPa. In the example, it can be a typical but not unique limiting pressure range such as 0.3 to 1 MPa, 1 to 2 MPa, 2 to 3 MPa, 3 to 4 MPa, 4 to 5 MPa; where, under this pressure range, the pressing time should be sufficient so that the electrode active layer 22 and the current collector 21 can be fully pressed together to improve the bonding strength between the two.

[0127] (2) The temperature is 10 to 100°C, and can be selected as 20 to 75°C. In the example, it can be a typical but not unique limiting temperature such as 10 to 30°C, 30 to 50°C, 50 to 70°C, 70 to 90°C, or 90 to 100°C. The specific temperature of this pressing process can be flexibly controlled according to the type of conductive adhesive.

[0128] (3) The pressing process is roller pressing.

[0129] By controlling at least one of (1) to (3) above in the pressing process, such as one or more combinations, the strength of the laminated bond between the electrode active layer 22 and the current collector 21 is further enhanced, thereby improving the structural strength and recyclability of the electrode sheet 20. Among them, when the rolling process is used, continuous production of the electrode sheet 20 can be realized, thereby improving the production efficiency of the electrode sheet.

[0130] In addition, the pressing process can be flexibly selected and controlled according to the different conductive adhesives contained in the conductive adhesive layer 12. For example, when the conductive adhesive layer 12 is a conductive hot melt adhesive layer, the temperature of the pressing process can be controlled to be 10 to 100°C, or 20 to 75°C.

[0131] In this embodiment, after the lamination and bonding process in step S40 above, the conductive adhesive layer 12 is pressed and cured to form a layer as shown in the figure. Figure 2 China G map and Figure 3The conductive adhesive layer 23 is shown in the figure. In the embodiments, the thickness of the conductive adhesive layer 23 can be 1 to 3 μm. In exemplary examples, it can be a typical but not uniquely limiting thickness range such as 1 to 2 μm or 2 to 3 μm. In the embodiments, the film resistance of the conductive adhesive layer 23 can be 0.001 to 0.1 μm, optionally 0.001 to 0.01 μm. In exemplary examples, it can be controlled to a typical but not uniquely limiting film resistance such as 0.001 to 0.005 μm, 0.005 to 0.01 μm, 0.01 to 0.03 μm, 0.03 to 0.05 μm, 0.05 to 0.08 μm, or 0.08 to 0.10 μm. The film resistance refers to the resistance value measured along the thickness direction of the conductive adhesive layer 23. By controlling the thickness of the conductive adhesive layer 23, the strength of the laminated bond between the enhanced electrode active layer 22 and the current collector 21 can be effectively improved, thereby enhancing the structural strength and cycle life of the electrode sheet 20. At the same time, the resistance between the electrode active layer 22 and the current collector 21 can be effectively reduced, thereby reducing the resistance of the prepared electrode sheet 20. This can reduce the internal resistance of the battery and improve the battery's rate performance.

[0132] Step S50:

[0133] The separation process in step S50 is to separate the substrate 10 from the surface of the electrode active layer 22, exposing the electrode active layer 22, specifically exposing the surface with less binder 222. In one embodiment, the electrode sheet structure obtained after separating the substrate 10 is as follows: Figure 2 As shown in Figure G. Of course, the electrode sheet structure obtained after separating the substrate 10 can also be... Figure 3 The structure shown specifically involves bonding the electrode active layer 22 to both opposite surfaces of the current collector 21 via conductive adhesive layers 23.

[0134] Secondly, embodiments of this application also provide an electrode sheet. In some embodiments, such as Figure 2 China G map and Figure 3 As shown, the electrode sheet 20 in this embodiment includes a current collector 21, a conductive adhesive layer 23, and an electrode active layer 22. The current collector 21, the conductive adhesive layer 23, and the electrode active layer 22 are stacked sequentially from the current collector 21 to the electrode active layer 22. That is, a conductive adhesive layer 23 is stacked between the electrode active layer 22 and the current collector 21.

[0135] In the electrode active layer 22, the content of the binder 222 on the side closer to the current collector 21 is higher than the content of the binder 222 on the side away from the current collector 21.

[0136] In the electrode active layer 22 of the electrode sheet 20 in this embodiment, the surface layer on the side closest to the current collector 21 has a high content of binder 222. This binder 222 can work synergistically with the conductive adhesive layer 23 to significantly enhance the bonding strength between the electrode active layer 22 and the surface of the current collector 21, thereby significantly improving the cycle performance of the electrode sheet 20. Moreover, the surface layer on the side of the electrode active layer 22 away from the current collector 21 has a relatively low content of binder 222, resulting in abundant pores on this side, which can significantly improve the electrolyte wettability of the electrode active layer 22.

[0137] In the embodiments, the current collector 21 contained in the electrode sheet 20 of this application embodiment can be a positive current collector or a negative current collector. Furthermore, based on the structure of the electrode sheet 20 of this application embodiment and the preparation method of the electrode sheet 20 of the above-described application embodiment, the thickness of the current collector 21 can be thinner than the thickness of the current collector contained in a conventional electrode sheet. Specifically, it can be the thickness requirement or material type of the current collector 21 described in step S10 of the preparation method of the electrode sheet 20 of the above-described application embodiment.

[0138] In the embodiments of this application, the thickness of the electrode active layer 22 contained in the electrode sheet 20 can be 50-250 μm, optionally 80-200 μm. In exemplary examples, typical but not uniquely limiting thickness ranges include 50-80 μm, 80-100 μm, 100-120 μm, 120-150 μm, 150-180 μm, 200-220 μm, and 220-250 μm. Therefore, the electrode active layer 22 contained in the electrode sheet 20 of this application can be controlled to have a relatively large thickness, thereby significantly improving the energy density of the battery.

[0139] In this embodiment, the electrode active layer 22 can be a negative electrode active layer. In this case, the thickness of the negative electrode active layer can be 50–250 μm, and optionally 80–200 μm. Compared to the negative electrode active layer contained in a conventional negative electrode current collector, the thickness of the negative electrode active layer contained in the electrode sheet 20 of this embodiment is increased by 30%–50%, thus significantly improving the energy density of the electrode sheet and the battery.

[0140] In the embodiments, the material of the electrode active layer 22 is the same as that contained in the electrode active layer 22 prepared in step S20 of the electrode sheet 20 preparation method of the above-mentioned application embodiment, such as including electrode material, binder 222 or further including conductive agent or other additives.

[0141] When the electrode active layer 22 (i.e., the negative electrode active layer) contains negative electrode active material, the current collector 21 contained in the electrode sheet 20 of this embodiment corresponds to the negative electrode current collector. In this embodiment, the thickness of the negative electrode current collector can be 4–6 μm. Therefore, the thickness of the negative electrode current collector contained in the electrode sheet 20 of this embodiment is within the thickness range, and the thickness of its contained negative electrode active layer may be thicker than that contained in a conventional negative electrode sheet, such as 50–250 μm as mentioned above, or optionally 80–200 μm. This can further improve the energy density of the electrode sheet and the battery. Of course, the negative electrode current collector can also be controlled to be thinner.

[0142] The conductive adhesive layer 23 included in the electrode sheet 20 of this application embodiment is used to laminate and bond the surface 221 of the electrode active layer 22 to the current collector 21. In the embodiment, the thickness of the conductive adhesive layer 23 can be 0.3-3 μm, optionally 0.5-1.5 μm. This thickness range of conductive adhesive layer 23 effectively improves the strength of the laminated bond between the electrode active layer 22 and the current collector 21, enhancing the structural strength and cycle life of the electrode sheet 20. It also effectively reduces the resistance at the interface between the electrode active layer 22 and the current collector 21, thereby reducing the resistance of the prepared electrode sheet 20, which in turn reduces the internal resistance of the battery and improves its rate performance. In the embodiment, the film resistance of the conductive adhesive layer 23 is 0.001-0.1 Ω, optionally 0.001-0.01 Ω. It has high conductivity and low resistance.

[0143] Battery

[0144] Thirdly, embodiments of this application also provide a battery. The battery of this application embodiment includes electrode sheets, and these electrode sheets are the same as those described in the above-described application embodiment.

[0145] In this embodiment, when the positive electrode of the battery is the electrode sheet described in the above embodiment, then the electrode sheet is a positive electrode sheet, and the current collector 21 it contains is a positive current collector, and the electrode active layer 22 is a positive active layer. Similarly, when the negative electrode of the battery is the electrode sheet described in the above embodiment, then the electrode sheet is a negative electrode sheet, and the current collector 21 it contains is a negative current collector, and the electrode active layer 22 is a negative active layer. Of course, the positive and negative electrodes of the battery can both be the electrode sheets described in the above embodiment.

[0146] Since the electrodes of the battery in this embodiment are the electrode sheets described in the previous embodiment, the battery in this embodiment has good cycle life.

[0147] In the embodiments, since the electrode active layer 22 contained in the electrode sheet 20 of the above-mentioned application embodiment can be thicker than the electrode active layer contained in the conventional electrode sheet, and the current collector 21 can also be thinner than the current collector contained in the conventional electrode sheet, that is, the energy density of the electrode sheet 20 of the above-mentioned application embodiment is higher than that of the conventional electrode sheet. Therefore, the battery of the present application embodiment can further have high energy density and high rate performance on the basis of having good cycle performance.

[0148] In the embodiments of this application, the battery may include any one of a battery cell, a battery module, or a battery pack.

[0149] Here, a battery cell refers to a battery casing and electrode assemblies encapsulated within the battery casing. The shape of the battery cell is not particularly limited; it can be cylindrical, square, or any other arbitrary shape. In the example, the battery cell can be as follows: Figure 4 The shown is a square-structured battery cell 30.

[0150] In some embodiments, such as Figure 5 As shown, the outer packaging of the battery cell 30 may include a housing 31 and a cover plate 33. The housing 31 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 31 has an opening communicating with the receiving cavity, and the cover plate 33 is used to cover the opening to close the receiving cavity. In this embodiment, the positive electrode, separator, and negative electrode contained in the battery cell 30 may be formed into an electrode assembly 32 by a winding process and / or a stacking process. The electrode assembly 32 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 32. The number of electrode assemblies 32 contained in the battery cell 30 may be one or more, which can be adjusted according to actual needs.

[0151] The method for preparing the battery cell 30 is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form the battery cell 30. As an example, the positive electrode, the separator, and the negative electrode can be formed into an electrode assembly 32 by a winding process or a stacking process. The electrode assembly 32 is placed in an outer package, dried, and then injected with an electrolyte. After vacuum sealing, settling, formation, shaping, and other processes, the battery cell 30 is obtained.

[0152] A battery module is assembled from the battery cell 30, which means it can contain multiple battery cells 30. The specific number can be adjusted according to the application and capacity of the battery module.

[0153] In some embodiments, Figure 6 This is a schematic diagram of battery module 40 as an example. Figure 6As shown, in the battery module 40, multiple battery cells 30 can be arranged sequentially along the length of the battery module 40. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 30 can be fixed in place using fasteners.

[0154] Optionally, the battery module 40 may also include a housing with a receiving space in which multiple battery cells 30 are received.

[0155] A battery pack refers to an assembly of the aforementioned battery cells 30, meaning it can contain multiple battery cells 30. These multiple battery cells 30 can be assembled into the aforementioned battery module 40. The specific number of battery cells 30 or battery modules 40 contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0156] As in the example, Figure 7 and Figure 8 This is a schematic diagram of a battery pack 50 as an example. The battery pack 50 may include a battery compartment and multiple battery modules 40 disposed within the battery compartment. The battery compartment includes an upper compartment 51 and a lower compartment 52. The upper compartment 51 covers the lower compartment 52, forming a closed space for accommodating the battery modules 40. The multiple battery modules 40 can be arranged in any manner within the battery compartment.

[0157] Electrical appliances

[0158] Fifthly, this application also provides an electrical device. The electrical device of this application includes a power supply unit or an energy storage unit, and may also include other auxiliary or necessary components. The power supply unit or energy storage unit contains the battery described in the above application embodiment. The power supply unit or energy storage unit may contain one or more batteries. When there are multiple batteries, they can form a battery module or battery pack. Because the electrical device of this application embodiment contains the battery described in the above application embodiment, the power supply unit or energy storage unit of the electrical device of this application embodiment has good cycle performance, long service life, and can further have high energy density and other performance characteristics. Furthermore, the electrical device of this application embodiment has a long standby or battery life.

[0159] Figure 9 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0160] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0161] Energy storage devices

[0162] Sixthly, embodiments of this application also provide an energy storage device, which includes an energy storage unit and may also include other auxiliary or necessary components. The energy storage unit contains the battery described in the above-described application embodiment. The energy storage unit may contain one or more batteries. When there are multiple batteries, they can form a battery module or battery pack. Because the energy storage device of this application embodiment contains the battery described in the above-described application embodiment, the energy storage device has good cycle performance, long service life, and further high energy density.

[0163] Example

[0164] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0165] 1. Examples of Electrode Sheets and Their Preparation Methods

[0166] Example A1

[0167] This embodiment provides a negative electrode sheet, including a copper foil and a negative electrode active layer. The negative electrode active layer is laminated onto the surface of the copper foil by a conductive voltage-sensitive adhesive layer. The surface of the negative electrode active layer that accumulates due to the binder rising during the drying process, and which is also the surface with a relatively high binder content, is laminated with the copper foil surface. The copper foil has a thickness of 4 μm, the negative electrode active layer has a thickness of 150 μm (the active material layer is the same thickness), and the conductive voltage-sensitive adhesive layer has a thickness of 1 μm.

[0168] The preparation method of the negative electrode sheet in this embodiment includes the following steps:

[0169] S1. Preparation of the negative electrode active layer:

[0170] S11: Using silicon carbon material as the negative electrode active material, thickener CMC, binder styrene-butadiene rubber, and conductive agent SP are mixed in a mass ratio of 90:1:2:7, deionized water is added, and a negative electrode slurry is obtained under vacuum stirring. The solid content of the negative electrode slurry is 45 wt%.

[0171] S12: The negative electrode slurry prepared in step S11 is coated on the surface of a PET film with a thickness of 50 μm and dried at 130°C. The thickness of the negative electrode active layer is 150 μm. The release force of the PET film surface used for coating the negative electrode slurry is 800 gf / 25 mm.

[0172] S2. Apply the conductive voltage-sensitive adhesive paste to the surface of a 4μm thick copper foil, and after drying, form a conductive adhesive layer on the surface of the copper foil;

[0173] S3. The surface of the copper foil containing the conductive adhesive layer is laminated with the surface of the negative electrode active layer prepared in step S1, and then subjected to cold pressing at 3MPa. At the same time, the PET film is separated to obtain the negative electrode sheet.

[0174] Example A2

[0175] This embodiment provides a negative electrode sheet, which is the same as the negative electrode sheet in Example A1, except that the preparation method of the negative electrode sheet in this embodiment is as follows:

[0176] The method for preparing the negative electrode sheet in this embodiment differs from that in Example A1 in that the release force of the PET film surface used for coating the negative electrode slurry in step S12 is 1200 gf / 25 mm. All other steps are the same.

[0177] Example A3

[0178] This embodiment provides a negative electrode sheet, which is the same as the negative electrode sheet in Example A1, except that the preparation method of the negative electrode sheet in this embodiment is as follows:

[0179] Compared with the method for preparing the negative electrode in Example A1, the method for preparing the negative electrode in this embodiment replaces the cold pressing process in step S3 with a hot pressing temperature of 80°C.

[0180] Example A4

[0181] This embodiment provides a negative electrode sheet, which differs from the negative electrode sheet in Embodiment A1 in that the negative electrode active layer is 100μm thick.

[0182] The preparation method of the negative electrode in this embodiment refers to the preparation method steps and conditions in Example A1, and is adjusted according to the negative electrode in this embodiment.

[0183] Comparative Example A1

[0184] This comparative example provides a negative electrode sheet, including a copper foil and a negative electrode active layer formed on the surface of the copper foil. The surface of this negative electrode active layer, which accumulates due to binder bubbling during the drying process, is also the surface with a relatively high binder content, stacked away from the copper foil surface. The copper foil has a thickness of 4 μm, and the negative electrode active layer has a thickness of 150 μm, the same as the active material layer thickness.

[0185] The preparation method of the negative electrode sheet in this embodiment includes the following steps:

[0186] S1. Using silicon carbon material as the negative electrode active material, thickener CMC, binder styrene-butadiene rubber, and conductive agent SP are mixed in a mass ratio of 90:1:2:7, deionized water is added, and a negative electrode slurry is obtained under vacuum stirring. The solid content of the negative electrode slurry is 45 wt%.

[0187] S2. The negative electrode slurry prepared in step S1 is coated on the surface of a 4μm thick copper foil, dried at 130℃, and the active material layer is 100μm thick. The negative electrode sheet is then prepared by cold pressing.

[0188] Comparative Example A2

[0189] This comparative example provides a negative electrode sheet, which differs from the negative electrode sheet in Comparative Example A1 in that the active layer of the negative electrode is 150 μm.

[0190] The preparation method of the negative electrode in this comparative example is the same as that in Comparative Example A1, where the negative electrode slurry is directly coated onto copper foil.

[0191] The relevant performance testing methods for electrode sheets are as follows:

[0192] (1) Observation of the morphology of the current collector and electrode active layer contained in the electrode sheet during the electrode slurry coating process:

[0193] The morphology of the current collector and electrode active layer contained in the prepared electrode sheets was observed with the naked eye during the application of the electrode slurry.

[0194] (2) Adhesion test: The electrode sheets prepared in each embodiment were stretched using a tensile testing machine at a stretching speed of 50 mm / min, and the 180° peel adhesion force was recorded;

[0195] The test results are shown in Table 1 below:

[0196] Table 1

[0197]

[0198] From the data in Table 1, comparing Examples A1 to A4 with Comparative Examples A1 and A2, it can be seen that, under the premise of ensuring high-quality coating of the electrode slurry, no band breakage, and that the electrode sheet quality meets the requirements, the electrode sheet of the present application can significantly increase the thickness of the electrode active layer compared to Comparative Example A1. For example, the negative electrode active layer of the negative electrode sheet of the present application can be 100 μm thicker, reaching up to 200 μm, while still ensuring that the quality of the negative electrode sheet meets the production requirements. However, when Comparative Example A2 directly forms a 150 μm negative electrode active layer on the surface of the copper foil, it directly causes slurry overflow and copper foil band breakage. Consequently, the aluminum foil and negative electrode active layer of the formed negative electrode sheet are wrinkled and broken, failing to meet the production quality requirements. This indicates that the abnormal coating process and negative electrode sheet in Comparative Example A2 show that the copper foil cannot withstand the weight of the slurry when thickly coated.

[0199] In addition, during the testing process, the positive electrode sheet was prepared according to the methods described in Examples A1 to A4 above. This also allowed for a reduction in the thickness of the positive electrode current collector while increasing the thickness of the positive electrode active layer, ensuring that the quality of the positive electrode sheet met production requirements, without any defects such as wrinkling of the positive electrode current collector or the positive electrode active layer, or strip breakage.

[0200] Therefore, by adopting the electrode sheet preparation method of the present application embodiment, the thickness of the electrode active layer can be relatively increased, the electrode sheet can be produced normally, the quality of the prepared electrode sheet meets the requirements, and the electrode sheet production efficiency can be improved.

[0201] 2. Example of a secondary battery cell

[0202] Examples B1 to B4 and Comparative Example B1;

[0203] Examples B1 to B4 and Comparative Example B1 each provide a secondary battery cell. Each secondary battery cell includes an electrode assembly formed by a positive electrode, a separator, and a negative electrode, and also includes an electrolyte.

[0204] The secondary battery cells in Examples B1 to B4 and Comparative Example B1 are assembled as follows:

[0205] Positive electrode sheet: The positive electrode active slurry is composed of NCM333, conductive carbon black SP and binder PVDF in a weight ratio of 97:1:2. After drying and cold pressing, it becomes the positive electrode sheet.

[0206] Negative electrode sheet: Negative electrode sheets provided in Examples A1 to A4 and Comparative Example A1 (the electrode sheet prepared in Comparative Example A2 was abandoned for assembly into a single battery cell due to obvious quality problems).

[0207] Electrolyte: The organic solvent is a mixture containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC, and DEC is 20:20:60. Thoroughly dried lithium salt LiPF6 is dissolved in the organic solvent and mixed thoroughly in an argon-atmosphere glove box with a water content <0.1 ppm to obtain the electrolyte. The concentration of the lithium salt is 1 mol / L.

[0208] Separator: A 10μm thick polypropylene separator membrane is selected.

[0209] Battery assembly: Assembling the hard-shell cells of each lithium iron phosphate battery according to the battery assembly requirements and processes.

[0210] Performance tests of secondary battery cells:

[0211] Rate performance test: Discharge each of the above-assembled secondary battery cells at a 1C current, let them stand for 2 hours, and then charge them at a 3C current; calculate the 3C charging capacity / initial capacity * 100%.

[0212] Capacity retention rate test: After 500 charge / discharge cycles at 1C current, calculate the charge / discharge capacity / initial capacity * 100%, which is the capacity retention rate.

[0213] Capacity testing method: Charge the battery at a constant current rate of 1C to 4.2V at 25℃, then charge it at a constant voltage until the current is ≤0.5C, and then discharge it at a constant current rate of 1C to 2.8V. The discharge capacity at this point is the battery capacity. Cell mass energy density = Battery capacity * 3.6 / Cell mass.

[0214] The relevant performance tests of secondary battery cells are shown in Table 2 below:

[0215] Table 2

[0216]

[0217] As can be seen from the data in Table 2, the battery containing the electrode sheet of the present application has a significantly improved cycle performance compared to the battery provided in the comparative example due to the presence of the electrode sheet of the present application. Therefore, under the same conditions, the structural strength of the electrode sheet of the present application is significantly improved, which contributes to the cycle performance of the battery.

[0218] Furthermore, battery rate performance and other properties have also been significantly improved. Therefore, it can be seen that the electrode sheets in this embodiment can have a thicker active layer, or a relatively thinner current collector, thus contributing to the battery's energy density.

[0219] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for producing an electrode sheet, comprising the steps of: A substrate and a current collector are provided, wherein preparing a base having a release surface; the release force of the release surface being 800 to 1200 gf / 25 mm; preparing an electrode active layer on the release surface of the base; forming a conductive adhesive layer on the surface of the current collector and / or the surface of the electrode active layer facing away from the base; the thickness of the conductive adhesive layer formed being 1 to 3 μm; and in the electrode active layer, the content of the adhesive on the side close to the current collector is higher than the content of the adhesive on the side facing away from the current collector; subjecting the surface of the electrode active layer facing away from the base to the surface of the current collector to a lamination adhesion treatment; obtaining a composite film; subjecting the base to the electrode active layer to a separation treatment during or after the lamination adhesion treatment, and obtaining an electrode sheet.

2. The production method according to claim 1, characterized by: The release surface is coated with a release agent.

3. The production method according to claim 2, characterized by: The release agent includes at least one of a silicon-containing release agent, an alkane-based non-silicon release agent.

4. The production method according to any one of claims 1 to 3, characterized by: The base is a film that can be wound.

5. The production method according to claim 4, characterized by: The thickness of the film is 20 to 100 μm.

6. The production method according to claim 5, characterized by: The thickness of the film is 30 to 50 μm.

7. The production method according to any one of claims 1 to 6, characterized by: The thickness of the electrode active layer is 50 to 250 μm.

8. The production method according to claim 7, characterized by: The thickness of the electrode active layer is 80 to 200 μm.

9. The process according to any one of claims 1 to 8, characterized in that: The electrode active layer is a negative electrode active layer.

10. The production method according to claim 9, characterized by: The current collector is a negative electrode current collector, and the thickness of the negative electrode current collector is 4 to 6 μm.

11. The production method according to any one of claims 1 to 10, characterized by: The conductive adhesive used for forming the conductive adhesive layer includes at least one of a conductive pressure-sensitive adhesive, a conductive acrylate adhesive, a conductive polyurethane adhesive, a conductive polyimide resin adhesive.

12. The process according to any one of claims 1 to 11, characterized in that: The lamination adhesion treatment includes a step of subjecting the composite film to a press bonding treatment.

13. The production method according to claim 12, characterized by: The press bonding treatment of the composite film includes at least one of the following (1) to (3): (1) the pressure is 0.3 to 5 MPa; (2) the temperature is 10 to 100°C; (3) the press bonding treatment is a roll press treatment.

14. The production method according to claim 13, characterized by: The press bonding treatment of the composite film includes at least one of the following (1) to (2): (1) the pressure is 0.5 to 3 MPa; (2) the temperature is 20 to 75°C.

15. The method of claim 11, wherein: The conductive adhesive layer is a conductive pressure-sensitive adhesive layer.

16. An electrode sheet prepared by a method of preparing an electrode sheet according to any one of claims 1 to 15, comprising a current collector and an electrode active layer combined with the current collector, the electrode active layer containing a binder, characterized in that: A conductive adhesive layer is provided between the electrode active layer and the current collector; and in the electrode active layer, the content of the adhesive on the side close to the current collector is higher than the content of the adhesive on the side facing away from the current collector.

17. The electrode patch of claim 16, wherein: The thickness of the electrode active layer is 50 to 250 μm.

18. The electrode patch of claim 17, wherein: The thickness of the electrode active layer is 80 to 200 μm.

19. The electrode sheet of any one of claims 17-18, wherein: The electrode active layer is a negative electrode active layer; and / or The current collector is a negative electrode current collector, and the thickness of the negative electrode current collector is 4 to 6 μm.

20. An electrode sheet as claimed in any one of claims 16 to 19, characterized in that: The thickness of the conductive adhesive layer is 0.3 to 3 μm; and / or The sheet resistance of the conductive adhesive layer is 0.001 to 0.1 Ω.

21. The electrode patch of claim 20, wherein: The thickness of the conductive adhesive layer is 0.5 to 1.5 μm; and / or The sheet resistance of the conductive adhesive layer is 0.001 to 0.01 Ω.

22. A battery, characterized by The battery includes an electrode sheet produced by the production method according to any one of claims 1 to 15 or the electrode sheet according to any one of claims 16 to 21.

23. The battery of claim 22, wherein the cathode comprises a lithium metal oxide. The battery comprises any one of a battery cell, a battery module, a battery pack.

24. An electrical device, comprising: A power supply unit or an energy storage unit comprising a battery, the battery comprising the battery of claim 22 or 23.

25. An energy storage device, comprising: An energy storage unit comprising a battery, the battery comprising the battery of claim 22 or 23.

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