An electrode sheet, a method of manufacturing the same, a battery, a battery pack, and an electric device

Abstract

The embodiment of the present application provides an electrode sheet, a preparation method thereof, a battery, a battery pack and an electric device. The electrode sheet comprises an electrode current collector and an electrode active layer film layer located on at least one side of the electrode current collector. The electrode active layer film layer comprises a first active layer, a second active layer and a medium layer located between the first active layer and the second active layer. The medium layer comprises at least one medium channel. The medium channel comprises a porous carbon material, which can improve the conductivity and liquid phase transmission capacity of the electrode sheet and reduce the internal resistance of the battery.

Description

Technical Field

[0001] This application relates to the field of batteries, and more particularly to an electrode sheet and its preparation method, a battery, a battery pack, and an electrical device. Background Technology

[0002] Electrode sheets (or simply electrodes) are an important component of batteries. The conductivity and liquid phase transport capacity of electrode sheets affect the electrochemical performance of batteries, such as internal resistance. In the existing technology, methods such as opening holes or setting grooves on the surface of electrode material layers are used, but these are not sufficient to simultaneously improve the conductivity and liquid phase transport capacity of electrode sheets.

[0003] Therefore, how to improve the conductivity and liquid phase transport capability of the electrode sheet and reduce the internal resistance of the battery remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] This application provides an electrode sheet and its preparation method, a battery, a battery pack, and an electrical device, which can improve the conductivity and liquid phase transport capability of the electrode sheet and reduce the internal resistance of the battery.

[0005] In a first aspect, embodiments of this application provide an electrode sheet, including an electrode current collector and an electrode film layer located on at least one side of the electrode current collector. The electrode film layer includes a first active layer, a second active layer, and a dielectric layer located between the first active layer and the second active layer. The dielectric layer includes at least one dielectric channel, and the dielectric channel includes a porous carbon material.

[0006] In one possible implementation, the infrared spectrum of the dielectric layer includes a first absorption peak and / or a second absorption peak, wherein the wavenumber of the first absorption peak is 840 cm⁻¹. -1 ±5cm -1 The wavenumber of the second absorption peak is 776 cm⁻¹. -1 ±5cm -1 .

[0007] In one possible implementation, the porous carbon material includes oxygen-containing functional groups, which include one or more of carboxyl, hydroxyl, and ether groups.

[0008] In one possible implementation, the dielectric layer includes a plurality of the dielectric channels, at least some of which intersect.

[0009] In one possible implementation, the dielectric layer includes a first dielectric group and a second dielectric group, the first dielectric group including a plurality of dielectric channels arranged along a first direction, and the second dielectric group including a plurality of dielectric channels arranged along a second direction, wherein the first direction intersects the second direction;

[0010] Preferably, the dielectric layer includes a mesh structure formed by the intersection of at least a portion of the dielectric channels in the first dielectric group and at least a portion of the dielectric channels in the second dielectric group.

[0011] In one possible implementation, the width of the medium channel is 0.4 μm to 20 μm, preferably 0.8 μm to 12 μm;

[0012] And / or, the dielectric layer includes multiple dielectric channels, and the spacing between any two adjacent dielectric channels is 4μm to 200μm, preferably, the spacing between any two adjacent dielectric channels is 10μm to 140μm.

[0013] In one possible implementation, at least one end of at least a portion of the dielectric channel extends to the edge of the electrode film layer;

[0014] Preferably, at least both ends of the dielectric channel extend to the edge of the electrode film layer.

[0015] In one possible implementation, the electrode film layer includes an electrode active layer and the dielectric layer, the electrode active layer includes a first active layer and a second active layer; the ratio of the thickness of the first active layer to the thickness of the electrode active layer is 0.1 to 0.5.

[0016] And / or, the thickness of the dielectric layer is 0.02 μm to 5 μm;

[0017] In one possible implementation, the electrode sheet is a negative electrode sheet.

[0018] Secondly, embodiments of this application provide a method for preparing the above-mentioned electrode sheet.

[0019] An electrode film precursor is formed on at least one side of the electrode current collector. The electrode film precursor includes a third active layer for forming the first active layer, a fourth active layer for forming the second active layer, and a dielectric layer precursor for forming the dielectric layer. The dielectric layer precursor includes a carbon source for forming the porous carbon material.

[0020] The electrode film precursor is carbonized to form the porous carbon material from the carbon source, thereby obtaining the electrode sheet.

[0021] In one possible implementation, the process of forming the electrode film precursor on at least one side of the electrode current collector includes:

[0022] A first slurry for forming the first active layer is applied to at least one side of the electrode current collector, and after drying, the third active layer is formed.

[0023] Then, a dielectric layer slurry containing the carbon source is coated onto the third active layer and dried to form the dielectric layer precursor.

[0024] Then, a second slurry for forming the second active layer is coated on the dielectric layer precursor, and after drying, the fourth active layer is formed to obtain the electrode film precursor.

[0025] After the electrode film precursor is rolled, it undergoes the carbonization process to obtain the electrode sheet.

[0026] In one possible implementation, the carbon source includes one or more of CMC, PAA, PVP, and alginate;

[0027] And / or, the carbonization treatment temperature is 260℃~340℃;

[0028] And / or, the carbonization treatment time is 10 min to 30 min.

[0029] Thirdly, embodiments of this application provide a battery including the electrode sheet described above or an electrode sheet prepared according to the electrode sheet preparation method described above.

[0030] Fourthly, embodiments of this application provide a battery pack comprising at least two batteries as described above.

[0031] Fifthly, embodiments of this application provide an electrical device including the battery pack described above.

[0032] This application provides an electrode sheet and its preparation method, a battery, a battery pack, and an electrical device. The electrode sheet includes an electrode current collector and an electrode film layer located on at least one side of the electrode current collector. The electrode film layer includes a first active layer, a second active layer, and a dielectric layer located between the first active layer and the second active layer. The dielectric layer includes at least one dielectric channel, which is made of porous carbon material and includes a conductive network. This improves the conductivity of the electrode sheet. The dielectric channel provides ion transport channels, which improves the liquid phase transport capability of the electrode sheet. Furthermore, the dielectric channel enhances the wetting of the electrolyte. Therefore, based on the above structure, the conductivity and liquid phase transport capability of the electrode sheet can be improved, and the internal resistance of the battery can be reduced. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0034] Figure 1 This is a flowchart illustrating the preparation process of the electrode sheet in one embodiment of the present invention;

[0035] Figure 2 The infrared spectra of the dielectric layer precursor and the dielectric layer in Embodiment 1 of the present invention are shown.

[0036] Reference numerals: 1: Third active layer; 2: Dielectric layer precursor; 3: Fourth active layer; 10: First active layer; 20: Dielectric layer; 30: Second active layer; 4: Electrode sheet.

[0037] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0038] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0039] Traditional electrode materials lack an efficient conductive network between layers, which limits the electrochemical performance of the battery, especially at high-rate charge and discharge. The electron conduction efficiency is low, and the dense structure between electrode layers may hinder the effective migration of active ions such as lithium ions, reducing the liquid phase transport capability of the electrode sheet, which will also increase the battery impedance.

[0040] This invention provides an electrode sheet, including an electrode current collector and an electrode film layer located on at least one side of the electrode current collector. The electrode film layer includes a first active layer, a second active layer, and a dielectric layer located between the first active layer and the second active layer. The dielectric layer includes at least one dielectric channel, and the dielectric channel includes a porous carbon material.

[0041] According to the inventors' research, the above-mentioned electrode sheet structure system can improve the conductivity and liquid phase transport capability of the electrode sheet, reduce the internal resistance of the battery, and increase the battery capacity. The reason for this is that the dielectric layer includes dielectric channels, which are composed of porous carbon materials. These channels form a conductive network, reducing the electrode film's dependence on additional conductive materials and thus improving the overall conductivity of the electrode. Simultaneously, these dielectric channels provide pathways for the migration of active ions such as lithium ions, effectively improving the migration environment and enhancing the liquid-phase transport capability of the electrode sheet. This reduces battery impedance and ultimately increases battery capacity. The dielectric layer reduces the impedance of electron migration paths, allowing the battery to maintain stable electrochemical performance under high-rate charge and discharge conditions, improving its fast-charge and fast-discharge performance. Furthermore, the dielectric channels enhance the affinity between the electrode sheet and the electrolyte, improving the electrolyte's wettability. The porous carbon materials in the dielectric layer improve the electrode sheet's ability to absorb and retain electrolyte, thereby accelerating lithium-ion transport. The optimized ion migration pathways reduce concentration polarization and overpotential loss, thus extending battery life and improving cycle stability.

[0042] In some embodiments, the infrared spectrum of the dielectric layer includes a first absorption peak, the wavenumber of which may be 840 cm⁻¹. -1 ±5cm -1 This can further improve the ion-conducting and electronic-conducting properties of the electrode sheet and reduce the internal resistance of the battery. The reason for this is that the first absorption peak is related to the cracking and rearrangement of CH bonds and the bending vibration within the CH bond plane. The porous carbon material in the dielectric layer contains the structure corresponding to the first absorption peak, which helps to further improve the affinity between the dielectric layer and the electrolyte, further improve the wettability of the electrolyte on the electrode sheet, and improve the electrolyte retention capacity of the electrode sheet, thereby improving the ion-conducting and electronic-conducting properties of the electrode sheet and reducing the internal resistance of the battery.

[0043] In some embodiments, the infrared spectrum of the dielectric layer includes a second absorption peak, the wavenumber of which may be 776 cm⁻¹. -1 ±5cm -1 The infrared spectrum of the dielectric layer includes a second absorption peak, which is more conducive to improving the interlayer liquid phase diffusion of the electrode sheets, thereby improving the liquid phase mass transfer capability of the electrode sheets, reducing the impedance of electron migration of the electrode sheets, and reducing the internal resistance of the battery. The reason for this is that the second absorption peak is related to the cracking and rearrangement of CO bonds in the carboxyl group, as well as the in-plane bending vibration of CO bonds in the carboxyl group. The porous carbon material in the dielectric layer contains the structure corresponding to the second absorption peak, which helps to further improve the liquid absorption and liquid retention capabilities of the porous carbon structure in the dielectric layer, further improve the wettability of the electrolyte to the electrode sheets, and improve the liquid retention capability of the electrode sheets to the electrolyte. This reduces the concentration polarization and overpotential loss of the ion migration path, improves the conductivity and liquid phase transport performance of the electrode sheets, and reduces the internal resistance of the battery.

[0044] In this embodiment of the invention, the first absorption peak and the second absorption peak, as well as the oxygen-containing functional groups, can be tested using the following method: Specifically, infrared spectroscopy can be used. Take the electrode sheet, scrape off the second active layer with a scraper to expose the dielectric layer, select the area with the dielectric layer structure, and test it with an optical microscope and an infrared spectrometer to obtain the first absorption peak and the second absorption peak within the spot scan range.

[0045] In some embodiments, the porous carbon material includes oxygen-containing functional groups, which can further improve the wettability of the electrolyte, promote ion transport, improve the liquid phase transport capability of the electrode sheet, and improve the compatibility between the traditional conductive carbon material and the electrolyte, thereby increasing the ion diffusion rate.

[0046] Specifically, oxygen-containing functional groups may include one or more of carboxyl, hydroxyl, and ether groups.

[0047] In some embodiments, the dielectric layer includes multiple dielectric channels, at least some of which intersect, which can help the dielectric layer form a richer conductive network and ion transport channels, reduce the internal resistance of the battery, and increase the battery capacity.

[0048] In some embodiments, the dielectric layer includes a first dielectric group and a second dielectric group. The first dielectric group includes a plurality of dielectric channels arranged along a first direction, and the second dielectric group includes a plurality of dielectric channels arranged along a second direction. The first direction and the second direction intersect, which is more conducive to forming a uniform conductive network and ion transport channels, reducing the internal resistance of the battery, and improving the electrochemical properties of the battery such as fast charging and fast discharging.

[0049] In some preferred embodiments, the dielectric layer includes a mesh structure formed by the intersection of at least some dielectric channels in the first dielectric group and at least some dielectric channels in the second dielectric group, which is beneficial to further reduce the impedance of the electron and ion transport paths between electrode layers and to reduce the internal resistance of the battery.

[0050] Specifically, such as Figure 1 As shown, the medium channels in the first medium group and the medium channels in the second medium group are intertwined to form a grid structure.

[0051] As mentioned above, the dielectric layer may include multiple dielectric channels. In some embodiments, the spacing between any two adjacent dielectric channels can be 4μm to 200μm, for example, it can be 4μm, 10μm, 50μm, 90μm, 140μm, 180μm, 200μm or any two of these ranges. Thus, the spacing between dielectric channels is not greater than 200μm, which can further enhance the wetting of the electrolyte, reduce the impedance of the transport pathway of active ions such as lithium ions in the electrode sheet, and help improve the liquid phase transport capability of the electrode. At the same time, the spacing between dielectric channels is not less than 4μm, which can further avoid the dielectric channels between the electrode sheet layers being too dense, which can enhance the peel strength of the electrode sheet and improve the structural stability of the electrode sheet. Therefore, the spacing between dielectric channels is 4μm to 200μm, which can further balance the reduction of battery impedance and the improvement of the battery's electrochemical performance such as fast charging and discharging and cycle stability.

[0052] In some embodiments, the spacing between any two adjacent dielectric channels is 10 μm to 140 μm, which can further improve the conductivity, ion conduction performance and peel strength of the electrode sheet.

[0053] In some embodiments, the width of the dielectric channel can be 0.4 μm to 20 μm, for example, it can be 0.4 μm, 0.8 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm or any two of these ranges. A dielectric channel width of not less than 0.4 μm can further improve the liquid phase mass transfer capability and conductivity of the electrode sheet. A dielectric channel width of not more than 20 μm can further improve the peel strength of the electrode sheet, maintain the structural stability of the electrode sheet, and improve the cycle stability of the battery while reducing the battery impedance. Therefore, a dielectric channel width of 0.4 μm to 20 μm can further balance the reduction of the battery's internal resistance and the improvement of the battery's cycle stability.

[0054] In some embodiments, the width of the dielectric channel is 0.8 μm to 12 μm, which can further improve the conductivity and peel strength of the electrode sheet.

[0055] In this embodiment of the invention, the width of the dielectric channel and the spacing between any two adjacent dielectric channels can be measured by the following method: Specifically, a scanning electron microscope (SEM) can be used to cut along the direction perpendicular to the thickness of the electrode sheet where the dielectric channel exists, and the cross-sectional structure of the electrode sheet can be tested with SEM. The average value of the three test results can be calculated to obtain the width of the dielectric channel and the spacing between any two adjacent dielectric channels.

[0056] In some embodiments, at least one end of at least a portion of the dielectric channel extends to the edge of the electrode film layer, which facilitates the electrolyte to wet the electrode layers through the dielectric channel at the edge, further enhancing the wetting effect of the electrolyte between the electrode layers and accelerating the transport speed of active ions such as lithium ions. The optimized ion migration path reduces concentration polarization and overpotential loss, thereby improving the cycle stability of the battery.

[0057] In some embodiments, at least both ends of a portion of the dielectric channel extend to the edge of the electrode film layer, which is beneficial for further enhancing the wetting effect of the electrolyte between the electrode layers and improving the battery's cycle stability and other performance characteristics.

[0058] In this embodiment of the invention, the electrode film layer includes an electrode active layer and a dielectric layer, and the electrode active layer includes a first active layer and a second active layer.

[0059] In some embodiments, the thickness of the electrode active layer can be 20μm to 200μm, which is beneficial to further improve battery capacity and reduce battery internal resistance.

[0060] Specifically, the thickness of the aforementioned electrode active layer refers to the thickness of the active layer on one side of the electrode.

[0061] In some embodiments, the ratio of the spacing between any two adjacent dielectric channels to the thickness of the electrode active layer can be 0.2 to 1, for example, it can be a range of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.1 or any combination thereof. A ratio of not less than 0.2 can further prevent the dielectric channels between electrode layers from being too dense, thereby enhancing the peel strength of the electrode and improving the structural stability of the electrode. A ratio of not more than 1 can further construct the transport pathway for active ions such as lithium ions in the electrode, which is beneficial to improving the liquid phase diffusion impedance of the electrode. Therefore, a ratio of 0.2 to 1 can further balance improving the liquid phase diffusion impedance of the electrode and improving the peel strength of the electrode.

[0062] In some preferred embodiments, the ratio of the spacing between any two adjacent dielectric channels to the thickness of the electrode active layer is 0.5 to 0.7, which can further reduce the internal resistance of the battery and improve the battery's electrochemical performance such as fast charging and discharging performance and cycle stability.

[0063] In some embodiments, the ratio of the width of the dielectric channel to the thickness of the electrode active layer can be 0.02 to 0.1, for example, it can be a range of 0.02, 0.04, 0.06, 0.08, 0.1 or any combination thereof. A ratio of the width of the dielectric channel to the thickness of the electrode active layer not less than 0.02 can further prevent the transport channels of active ions such as lithium ions in the electrode sheet from being too narrow, thereby improving the liquid phase transport capability of the electrode sheet. A ratio of the width of the dielectric channel to the thickness of the electrode active layer not greater than 0.1 can further improve the peel strength of the electrode sheet, maintain the structural stability of the electrode sheet, and improve the cycle stability of the battery while reducing the impedance of the battery. Therefore, a ratio of the width of the dielectric channel to the thickness of the electrode active layer of 0.02 to 0.1 is more conducive to improving the conductivity and ion conduction performance of the battery, as well as the fast charging and discharging performance and cycle stability of the battery.

[0064] In some preferred embodiments, the ratio of the width of the dielectric channel to the thickness of the electrode active layer can be 0.04 to 0.06, which can further reduce the internal resistance of the battery and improve the cycle stability of the battery.

[0065] In this embodiment of the invention, the thickness of the electrode film can be measured by conventional methods, such as using a micrometer to measure the thickness of the electrode film.

[0066] In some embodiments, the ratio of the thickness of the first active layer to the thickness of the electrode active layer can be 0.1 to 0.5, for example, it can be a range of 0.1, 0.2, 0.3, 0.4, 0.5 or any combination thereof. If the ratio of the thickness of the first active layer to the thickness of the electrode active layer is not less than 0.1, the dielectric channel in the dielectric layer will not be too close to the electrode current collector, which is beneficial to further enhance the improvement effect of the dielectric channel on the liquid phase diffusion impedance of the first active layer. If the ratio of the thickness of the first active layer to the thickness of the electrode active layer is not greater than 0.5, the dielectric channel in the dielectric layer will not be too far from the electrode current collector, which is beneficial to further improve the liquid phase diffusion impedance of the first active layer, improve the liquid phase transport capability of the first active layer, and thus improve the overall liquid phase transport capability of the electrode sheet. Therefore, a ratio of the thickness of the first active layer to the thickness of the electrode active layer of 0.1 to 0.5 is beneficial to further improve the conductivity of the electrode sheet and reduce the impedance of the ion transport path of the first active layer, thereby reducing the internal resistance of the battery.

[0067] In some embodiments, the thickness of the dielectric layer can be 0.02 μm to 5 μm, for example, it can be a range of 0.02 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any combination thereof. A dielectric layer thickness of not less than 0.02 μm is beneficial to further improve the conductivity and liquid phase transport capability of the electrode sheet. A dielectric layer thickness of not more than 5 μm is beneficial to improve the peel strength of the electrode sheet. Therefore, a dielectric layer thickness of 0.02 μm to 5 μm can further balance improving the peel strength of the electrode sheet and reducing the internal resistance of the battery.

[0068] In some embodiments, the electrode sheet is a negative electrode sheet, the electrode current collector is a negative electrode current collector, the electrode film is a negative electrode film, and the electrode active layer is a negative electrode active layer.

[0069] Specifically, the negative electrode active layer may include a negative electrode active material, a conductive agent, and a binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include graphite, which may include artificial graphite and / or natural graphite; the conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber; the binder may include one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0070] Generally, in the negative electrode active layer, the mass percentage of the negative electrode active material (i.e., the ratio of the mass of the negative electrode active material to the total mass of the negative electrode active layer) can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof; the mass percentage of the conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof; and the mass percentage of the binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0071] The embodiments of the present invention may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors include copper foil.

[0072] In this embodiment of the invention, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the negative electrode active layer, such as the negative electrode active material, conductive agent, and binder, can be dispersed in a solvent, such as water, to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0073] The present invention also provides a method for preparing the above-mentioned electrode sheet, wherein an electrode film precursor is formed on at least one side of an electrode current collector, the electrode film precursor includes a third active layer for forming a first active layer, a fourth active layer for forming a second active layer, and a dielectric layer precursor for forming a dielectric layer, the dielectric layer precursor including a carbon source for forming a porous carbon material; the electrode film precursor is subjected to carbonization treatment to form a porous carbon material from the carbon source, thereby obtaining the electrode sheet.

[0074] In some embodiments, the process of forming an electrode film precursor on at least one side of the electrode current collector includes: as follows Figure 1 As shown in ①, a first slurry for forming a first active layer is coated on at least one side of the electrode current collector, and after drying, a third active layer 1 is formed; then, as... Figure 1 As shown in ②, a dielectric layer slurry containing a carbon source is coated onto the third active layer and dried to form dielectric layer precursor 2; then, as... Figure 1 As shown in ③, a second slurry for forming the second active layer is coated onto the dielectric layer precursor. After drying, a fourth active layer 3 is formed, resulting in the electrode film precursor. The electrode film precursor is then rolled, as shown in... Figure 1 As shown in ④, it undergoes further carbonization treatment to obtain electrode sheet 4, as shown in ④. Figure 1 As shown, the electrode sheet includes a first active layer 10, a dielectric layer 20, and a second active layer 30.

[0075] In some embodiments, the first slurry and the second slurry may be the same or different.

[0076] In some embodiments, a carbon source is dispersed in a solvent, such as water, and mixed and stirred to prepare a slurry containing a carbon source.

[0077] The process of coating a dielectric layer slurry containing a carbon source onto the third active layer can be exemplified by using an anilox roller to coat the dielectric layer onto the third active layer. This facilitates the formation of a grid structure formed by intersecting dielectric channels, which is beneficial for improving the conductivity and ion conduction performance of the electrode sheet, further reducing the internal resistance of the battery, and increasing the battery capacity.

[0078] In this embodiment of the invention, the electrode film precursor is rolled and then carbonized, which is beneficial for the further formation of dielectric channels and the formation of microporous structures in the dielectric layer. This avoids the second active layer covering the microporous structures in the dielectric layer, which would hinder the construction of the conductive network and the ion transport channels, and is beneficial for further reducing the internal resistance of the battery.

[0079] In some embodiments, the carbon source includes one or more of carboxymethyl cellulose-based materials such as polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), and alginate. The carboxymethyl cellulose-based materials include carboxymethyl cellulose and / or carboxymethyl cellulose salts. Carboxymethyl cellulose includes sodium carboxymethyl cellulose (CMC), and carboxymethyl cellulose salts include sodium carboxymethyl cellulose salt (CMC-Na). This is more conducive to forming porous carbon materials with good conductivity in the dielectric layer, reducing the impedance of electron migration paths, improving the wetting effect of the electrolyte, reducing the impedance of ion migration paths, reducing the internal resistance of the battery, and improving the battery's electrochemical performance such as fast charging and discharging performance and cycle stability. It is also more conducive to the preparation of electrode sheets.

[0080] In some embodiments, the carbonization temperature can be between 260°C and 340°C, for example, a range of 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, or any combination thereof. The carbonization temperature is not higher than 340°C. This carbonization temperature, while ensuring the carbon source is carbonized, is beneficial for further improving the peel strength of the electrode sheet and the stability of the electrode sheet structure. The carbonization temperature is not lower than 260°C. This carbonization temperature can further promote the carbonization of the carbon source to form porous carbon materials with good conductivity, forming microporous structures and oxygen-containing functional groups. This is beneficial for improving the conductivity and liquid phase transport performance of the electrode sheet and reducing the internal resistance of the battery. The carbonization temperature of 260°C to 340°C can simultaneously reduce the internal resistance of the electrode and improve the structural stability of the electrode sheet.

[0081] In some embodiments, the carbonization time can be 10 min to 30 min, for example, it can be a range of 10 min, 15 min, 20 min, 25 min, 30 min or any two of these. A carbonization time of not less than 10 min can further promote the carbonization of the carbon source and form a uniform conductive network and ion channels. A carbonization time of not more than 30 min can avoid affecting other materials of the electrode sheet and thus affecting the structural stability of the electrode sheet. A carbonization time of 10 min to 30 min can balance improving the structural stability of the electrode sheet and reducing the internal resistance of the battery.

[0082] This invention also provides a battery comprising the electrode sheet described above or an electrode sheet prepared according to the electrode sheet preparation method described above. This battery has advantages corresponding to the electrode sheet described above, which will not be elaborated further.

[0083] In this embodiment of the invention, the battery can be a lithium-ion battery, specifically a lithium iron phosphate battery.

[0084] Generally, a battery includes a cell and a casing that encapsulates the cell. Electrolyte is injected into the cell within the casing. The cell includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes. The cell can be a stacked cell, meaning it is composed of alternating layers of positive electrode, separator, and negative electrode; or it can be a wound cell, meaning it is composed of positive electrode, separator, and negative electrode layers stacked sequentially and then wound together.

[0085] In this embodiment of the invention, the battery cell can be packaged using conventional housing materials in the art, such as flexible packaging materials like aluminum-plastic film, but is not limited thereto.

[0086] The electrolyte in this embodiment of the invention can be a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include organic solvents, additives, and electrolyte salts. Organic solvents include one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate (PC). Additives include, for example, fluoroethylene carbonate (FEC) and / or vinylene carbonate (VC). Electrolyte salts may include lithium salts, such as lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium nitrate (LiNO3), and lithium fluoride (LiF), but are not limited thereto.

[0087] In this embodiment of the invention, the separator is used to separate the positive electrode and the negative electrode to prevent the positive electrode and the negative electrode from short-circuiting due to contact. Conventional separators in the art can be used in this embodiment of the invention, and there are no special limitations on this.

[0088] Specifically, the diaphragm can be a porous structure diaphragm with electrochemical and chemical stability, such as one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene or polyvinylidene fluoride, and can be a single-layer or multi-layer diaphragm.

[0089] In this embodiment of the invention, conventional positive electrode sheets in the art can be used, and there are no particular limitations. For example, the positive electrode sheet may include a positive current collector and a positive active layer located on at least one side surface of the positive current collector. Specifically, the positive active layer may be provided on one side surface of the positive current collector, or the positive active layers may be provided on both opposite sides of the positive current collector in the thickness direction (i.e., the two surfaces of the positive current collector).

[0090] Generally, the positive electrode active layer may include a positive electrode active material, a conductive agent, and a binder, all of which can be conventional materials in the art. For example, the positive electrode active material may include one or more of lithium nickel oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary cathode materials. The ternary cathode materials may include nickel-cobalt-manganese ternary materials (NCM) and / or nickel-cobalt-aluminum ternary materials (NCA). The conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber. The binder may include one or more of polyvinylidene fluoride (PVDF), polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, etc.

[0091] Generally, in the positive electrode active layer, the mass percentage of the positive electrode active material (i.e., the ratio of the mass of the positive electrode active material to the total mass of the positive electrode active layer) can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof; the mass percentage of the conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof; and the mass percentage of the binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0092] The embodiments of the present invention may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0093] In this embodiment of the invention, the positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the positive electrode active material, conductive agent, binder, and other components used to form the positive electrode active layer can be dispersed in a solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0094] The embodiments of the present invention can assemble components such as positive electrode, separator and negative electrode into a battery using conventional methods in the art. For example, the positive electrode, separator and negative electrode can be stacked in sequence to obtain a battery cell. Then the battery cell is placed in a casing (outer packaging) and after conventional battery assembly processes such as electrolyte injection, baking and wetting, the battery is obtained.

[0095] This invention also provides a battery pack comprising at least two batteries as described above. This battery pack has advantages corresponding to the electrode plates or batteries described above, which will not be elaborated further.

[0096] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0097] This invention also provides an electrical device including the battery pack described above. This electrical device has advantages corresponding to the positive electrode or the battery described above, which will not be elaborated further.

[0098] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0099] The present invention will be further described below through specific embodiments.

[0100] Example 1

[0101] (1) Preparation of negative electrode

[0102] The graphite material, conductive carbon black, SBR, CMC, NMP and H2O were mixed and stirred in a mass ratio of 100:2:2:2:5:100 to prepare the first slurry. The first slurry was coated on the opposite two sides of the copper foil. After drying, a third active layer with a single-sided thickness of 30μm was formed.

[0103] CMC is dispersed in water, mixed and stirred to prepare a dielectric layer slurry, and the dielectric layer slurry is coated on the surface of the third active layer using an anilox roller. After drying, a dielectric layer precursor is formed.

[0104] The second slurry has the same composition and mass ratio as the first slurry. The second slurry is coated on the surface of the dielectric layer precursor. After drying, a fourth active layer with a single-sided thickness of 70 μm is formed, thus obtaining the negative electrode film precursor.

[0105] The negative electrode film precursor was rolled until the compaction density was 1.5 g / cm³. 3 The negative electrode sheet was prepared by carbonization under an inert nitrogen atmosphere at a temperature of 320°C for 15 minutes.

[0106] (2) Preparation of positive electrode sheet

[0107] Lithium iron phosphate (LFP), PVDF, and conductive agent carbon black were mixed in a mass ratio of 96:3:1. N-methylpyrrolidone (NMP) solvent was added, and the mixture was stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was coated onto both sides of an aluminum foil. After drying and rolling, a compaction density of 2.5 g / cm³ was formed on both sides of the aluminum foil. 3 The positive electrode active layer is used to prepare the positive electrode sheet.

[0108] (3) Battery assembly

[0109] The negative electrode, separator, positive electrode, and separator are stacked in sequence to form a battery cell. The battery cell consists of 7 positive electrode sheets, 8 negative electrode sheets, and 16 separators, with the negative electrode excess ratio being 15%.

[0110] The battery cells are packaged in aluminum-plastic film and assembled into lithium-ion batteries after processes such as baking, electrolyte injection, and immersion.

[0111] The electrolyte used is LiPF6 as the electrolyte salt and EC, DMC, and EMC as the solvents, with a mass ratio of EC:DMC:EMC:LiPF6 = 2:3:5:1.

[0112] Examples 2-21 differ from Example 1 in that the width of the dielectric channel, the spacing between any two adjacent dielectric channels, the ratio of the thickness of the first active layer to the thickness of the electrode active layer, the thickness of the dielectric layer, the temperature of the carbonization treatment, and the time of the carbonization treatment are different from those in Example 1, as detailed in Table 1. The remaining conditions and steps are the same as those in Example 1.

[0113] Comparative Example 1: The difference from Example 1 is that only the first and second active layers are coated, and after drying and rolling, a negative electrode sheet is obtained. The remaining conditions and steps are the same as in Example 1. The testing methods for the width of the dielectric channels and the spacing between any two adjacent dielectric channels in each example and comparative example are as described above, and will not be repeated here.

[0114] The negative electrode liquid phase diffusion resistance, negative electrode peeling force, lithium-ion battery 50% SOC DC internal resistance (DCIR), and lithium-ion battery mixed specific capacity of each embodiment and comparative example were tested by the following process, and the results are shown in Table 2.

[0115] (1) Test method for liquid phase diffusion impedance of negative electrode: The two negative electrode sheets and the separator are assembled into an electrode core in sequence; the electrode core is placed in the outer packaging shell, baked and then injected with electrolyte (the electrolyte formula is the same as the electrolyte in the lithium-ion battery above). After battery assembly processes such as encapsulation and wetting, a battery with liquid phase diffusion impedance is obtained. The liquid phase diffusion impedance is tested in the frequency range of 300000Hz-0.05Hz using an electrochemical workstation (model Bio-Logic EC-LAB VMP300). The measured liquid phase diffusion impedance of the negative electrode is shown in Table 2.

[0116] (2) Test method for peel force of negative electrode: Take the above negative electrode and prepare it with an area of ​​40×100mm. 2 For the negative electrode sample, the pressure-sensitive tape is bonded to a stainless steel plate, and then one side of the negative electrode film layer of the sample is bonded to the pressure-sensitive tape. The sample is then clamped with a tensile testing machine (model PY-880HJ 180° peel strength tensile tester) and peeled upwards at 180°. The force that causes the negative electrode film layer to peel off from the copper foil is the negative electrode peel force.

[0117] (3) Test method for DC internal resistance (DCIR) of lithium-ion battery at 50% SOC: At room temperature (25±5℃), take the lithium-ion battery prepared above, use the Blue Electric room temperature test channel (5V, 12A), discharge it to 2.0V with a constant current of 1 / 3C, then charge it to 50% SOC (50% state of charge) with a constant current of 1 / 3C, and let it rest for 30min; then discharge it with a constant current of 1.5C for 30s, and detect the DC internal resistance of the battery at 50% SOC, that is, the DCIR of the lithium-ion battery.

[0118] (4) Lithium-ion battery mixed material specific capacity test method: At room temperature (25±5℃), take the above-prepared positive electrode sheet, weigh it to obtain the total mass m1 of the positive electrode sheet, peel off the positive electrode active layer, weigh it to obtain the mass m2 of the positive electrode current collector, then the mass of the positive electrode active layer is m1-m2; take the above-prepared lithium-ion battery, discharge it to 2.0V with a constant current of 1 / 3C, then charge it to 3.8V with a constant current and constant voltage of 1 / 3C, cut off the current of 0.05C, and cycle it for 3 times according to the above steps; the discharge capacity of the third cycle is the battery capacity Q, then the specific capacity of the lithium-ion battery mixed material = Q / (m1-m2).

[0119] Table 1. Parameters and preparation data of the negative electrode.

[0120]

[0121] Table 2 Performance of Anode Sheets and Lithium-ion Batteries

[0122]

[0123] Compared to Comparative Example 1, the negative electrode film layer in Examples 1-21 includes a first active layer, a second active layer, and a dielectric layer located between the first active layer and the second active layer. The dielectric layer includes at least one dielectric channel, which includes a porous carbon material, and can improve the conductivity and liquid phase transport capability of the negative electrode sheet and reduce the internal resistance of the battery.

[0124] Specifically, such as Figure 2 As shown, Figure 2 The images show the infrared spectra of the dielectric precursor and dielectric layer in Example 1. Figure 2 The horizontal axis Wavenumber represents the wave number (in cm). -1 The vertical axis represents Transmittance (in %). The red line 320℃-15min-CMC-Na indicates that the carbonization temperature of the dielectric layer in Example 1 was 320℃, the carbonization time was 15min, and the carbon source was CMC-Na. The black line CMC-Na indicates that the carbon source of the dielectric layer precursor in this example was CMC-Na. Figure 2 The structural formula in the medium is the main chain structure of CMC-Na. Compared with the infrared spectrum of the dielectric layer precursor, the first absorption peak (wavenumber 840 cm⁻¹) can be clearly observed in the infrared spectrum of the dielectric layer. -1 ) and the second absorption peak (wavenumber 776 cm⁻¹) -1 This indicates that the dielectric layer can further improve the ion conduction and electronic conduction properties of the negative electrode, and reduce the internal resistance of the battery.

[0125] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An electrode sheet, characterized in that, The device includes an electrode current collector and an electrode film layer located on at least one side of the electrode current collector. The electrode film layer includes a first active layer, a second active layer, and a dielectric layer located between the first active layer and the second active layer. The dielectric layer includes at least one dielectric channel, and the dielectric channel includes a porous carbon material.

2. The electrode sheet according to claim 1, characterized in that, The infrared spectrum of the dielectric layer includes a first absorption peak and / or a second absorption peak, wherein the wavenumber of the first absorption peak is 840 cm⁻¹. -1 ±5cm -1 The wavenumber of the second absorption peak is 776 cm⁻¹. -1 ±5cm -1 .

3. The electrode sheet according to claim 1 or 2, characterized in that, The porous carbon material includes oxygen-containing functional groups, which include one or more of carboxyl, hydroxyl, and ether bonds.

4. The electrode sheet according to any one of claims 1-3, characterized in that, The dielectric layer includes multiple dielectric channels, at least some of which intersect.

5. The electrode sheet according to any one of claims 1-4, characterized in that, The dielectric layer includes a first dielectric group and a second dielectric group. The first dielectric group includes a plurality of dielectric channels arranged along a first direction, and the second dielectric group includes a plurality of dielectric channels arranged along a second direction. The first direction and the second direction intersect. Preferably, the dielectric layer includes a mesh structure formed by the intersection of at least a portion of the dielectric channels in the first dielectric group and at least a portion of the dielectric channels in the second dielectric group.

6. The electrode sheet according to any one of claims 1-5, characterized in that, The width of the medium channel is 0.4μm to 20μm, preferably 0.8μm to 12μm; And / or, the dielectric layer includes multiple dielectric channels, and the spacing between any two adjacent dielectric channels is 4μm to 200μm, preferably, the spacing between any two adjacent dielectric channels is 10μm to 140μm.

7. The electrode sheet according to any one of claims 1-6, characterized in that, At least one end of at least a portion of the dielectric channel extends to the edge of the electrode film layer; Preferably, at least both ends of the dielectric channel extend to the edge of the electrode film layer.

8. The electrode sheet according to claim 1, characterized in that, The electrode film layer includes an electrode active layer and a dielectric layer, the electrode active layer includes a first active layer and a second active layer; the ratio of the thickness of the first active layer to the thickness of the electrode active layer is 0.1~0.5; And / or, the thickness of the dielectric layer is 0.02μm~5μm.

9. The electrode sheet according to any one of claims 1-8, characterized in that, The electrode sheet is a negative electrode sheet.

10. A method for preparing an electrode sheet according to any one of claims 1-9, characterized in that, An electrode film precursor is formed on at least one side of the electrode current collector. The electrode film precursor includes a third active layer for forming the first active layer, a fourth active layer for forming the second active layer, and a dielectric layer precursor for forming the dielectric layer. The dielectric layer precursor includes a carbon source for forming the porous carbon material. The electrode film precursor is carbonized to form the porous carbon material from the carbon source, thereby obtaining the electrode sheet.

11. The method for preparing the electrode sheet according to claim 10, characterized in that, The process of forming an electrode film precursor on at least one side of the electrode current collector includes: A first slurry for forming the first active layer is applied to at least one side of the electrode current collector, and after drying, the third active layer is formed. Then, a dielectric layer slurry containing the carbon source is coated onto the third active layer and dried to form the dielectric layer precursor. Then, a second slurry for forming the second active layer is coated on the dielectric layer precursor, and after drying, the fourth active layer is formed to obtain the electrode film precursor; After the electrode film precursor is rolled, it undergoes the carbonization process to obtain the electrode sheet.

12. The method for preparing the electrode sheet according to claim 10 or 11, characterized in that, The carbon source includes one or more of CMC, PAA, PVP, and alginate; And / or, the carbonization treatment temperature is 260℃~340℃; And / or, the carbonization treatment time is 10 min to 30 min.

13. A battery, characterized in that, This includes the electrode sheet as described in any one of claims 1-9 or the electrode sheet prepared according to the method described in any one of claims 10-12.

14. A battery pack, characterized in that, It includes at least two batteries as described in claim 13.

15. An electrical appliance, characterized in that, Includes the battery pack as described in claim 14.

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