Negative electrode sheet, method of manufacturing negative electrode sheet, secondary battery, battery module, battery pack, and electric device

Abstract

The application provides a negative electrode sheet, a method for preparing the negative electrode sheet, a secondary battery, a battery module, a battery pack and a power utilization device. The negative electrode sheet comprises a ceramic material, a carbon-based negative electrode active material and a binder; wherein the value of the relationship formula of the relative dielectric constant ε of the ceramic material and the cell parameters a and c is 78.8-197.9, and the weight ratio of the ceramic material to the carbon-based negative electrode active material is 0.0052-0.115. The negative electrode sheet of the application can improve the lithium ion desolvation rate, reduce the lithium precipitation degree of the negative electrode sheet, reduce the thickness of the formed SEI film, reduce the consumption of active lithium ions, thereby reducing the interface impedance of the negative electrode sheet, improving the cycle life and charging rate of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a negative electrode sheet, a method for preparing a negative electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device. Background Technology

[0002] In recent years, with the increasingly widespread application of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant development of secondary batteries, higher requirements have been placed on their energy density, cycle performance, and safety performance. Existing negative electrode sheets are prone to lithium plating at the interface with the electrolyte, leading to the consumption of active lithium ions and a decrease in the cycle performance of the secondary battery. Furthermore, the existing negative electrode sheets have relatively thick SEI films, resulting in increased interfacial film impedance and a reduced charging rate. Simultaneously, the formation of a thick SEI film also consumes a large amount of electrolyte. Therefore, there is an urgent need for a negative electrode sheet that solves the above-mentioned technical problems. Summary of the Invention

[0003] This application addresses the aforementioned issues and aims to provide a negative electrode sheet, a method for preparing the negative electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device. The negative electrode sheet of this application can improve the lithium-ion desolvation rate, reduce the degree of lithium plating at the interface between the negative electrode sheet and the electrolyte, and reduce the consumption of active lithium ions, thereby improving the cycle life of the secondary battery. Furthermore, a thin SEI film can be formed on the surface of the negative electrode sheet of this application, shortening the lithium-ion migration path, increasing the charging rate of the secondary battery, and also reducing electrolyte consumption.

[0004] To achieve the above objectives, the first aspect of this application provides a negative electrode sheet comprising a ceramic material, a carbon-based negative electrode active material, and a binder; wherein the relative permittivity ε of the ceramic material is related to the cell parameters a and c by the formula ε / (c / a), which has a value of 78.8-197.9, and the weight ratio of the ceramic material to the carbon-based negative electrode active material is 0.0052-0.115, optionally 0.0052-0.057.

[0005] Therefore, this application improves the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film by using ceramic materials with a specific relationship between relative permittivity and cell parameters in a certain proportion with carbon-based negative electrode active materials, thereby reducing the risk of lithium dendrite formation, reducing the degree of lithium plating, forming a thinner SEI film, reducing the consumption of active lithium ions and electrolyte, and thus improving the cycle performance and charging rate of the secondary battery.

[0006] In any embodiment, the relative permittivity ε of the ceramic material is 80-200. Therefore, with the relative permittivity of the ceramic material within this range, the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film can be further improved, thereby further reducing the risk of lithium plating, reducing the thickness of the SEI film, and thus further improving the cycle performance and charging rate of the secondary battery.

[0007] In any embodiment, the ceramic material has a weight percentage of 0.5%-10% in the negative electrode sheet, and can be selected as 0.5%-5%.

[0008] Therefore, when the weight content of ceramic material in the negative electrode sheet is within the above range, it can further improve the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, further reduce the degree of lithium plating, further reduce the thickness of the SEI film, and thus further improve the cycle performance and charging rate of the secondary battery.

[0009] In any embodiment, the ceramic material is one or more selected from barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, and lead barium lithium niobate.

[0010] The relative permittivity of the ceramic materials described above is more closely matched with that of the electrolyte, which can further improve the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, thereby reducing the risk of lithium dendrite formation. Furthermore, the use of these ceramic materials can further reduce the thickness of the SEI film, thereby further improving the cycle performance and charging rate of the secondary battery.

[0011] In any embodiment, the particle size D of the ceramic material v 50 is 10-300nm, and can be selected as 50-200nm.

[0012] Therefore, the ceramic materials with the above-mentioned particle size range are more tightly bonded to the carbon-based negative electrode active materials, which further improves the lithium-ion desolvation effect, further reduces the thickness of the SEI film, and thus further improves the cycle performance and charging rate of the secondary battery.

[0013] In any embodiment, the particle size D of the carbon-based anode active material is... v 50 is 1-15μm, and can be selected as 5-10μm.

[0014] Therefore, the bonding between carbon-based anode active materials and ceramic materials within the aforementioned particle size range is more compact, which further improves the lithium-ion desolvation rate, further reduces the thickness of the formed SEI film, and thus further improves the cycle performance and charging rate of the secondary battery.

[0015] In any embodiment, the weight ratio of ceramic material to binder is 0.1-10, optionally 0.5-1.

[0016] The composite material particles formed by ceramic materials and binders within the above-mentioned ratio range are more tightly bonded to the carbon-based negative electrode active material, thereby further improving the lithium-ion desolvation rate, further reducing the thickness of the formed SEI film, and thus further improving the cycle performance and charging rate of the secondary battery.

[0017] In any embodiment, the adhesive is one or more selected from polyacrylic acid, styrene-butadiene rubber, polyvinylidene fluoride, polyamide-imide, polyvinyl alcohol, polyethyleneimine, polyimide, and poly(tert-butyl acrylate-triethoxyvinylsilane).

[0018] In any embodiment, the weight-average molecular weight of the adhesive is 500,000 to 4,000,000, optionally 1,000,000 to 2,000,000; optionally, the molecular weight distribution index of the adhesive is 2 to 10, more preferably 2 to 4.

[0019] The aforementioned binder enables a tighter bond between the ceramic material and the carbon-based anode active material, further improving the lithium-ion desolvation rate, further reducing the thickness of the SEI film, and further reducing the consumption of active lithium ions, thereby improving the cycle performance and charging rate of the secondary battery.

[0020] In any embodiment, the ceramic material is barium titanate, which includes two crystal forms: cubic and tetragonal; preferably, the tetragonal crystal form.

[0021] In any embodiment, barium titanate, when irradiated with Cu-Kα, has peaks at the following positions in the X-ray powder diffraction pattern expressed in 2θ angles: 22±1°, 31±1°, 38±1°, 45±1°, 56±1°.

[0022] Using barium titanate as a ceramic material can further improve the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, thereby further reducing the risk of lithium plating, reducing the thickness of the SEI film, and thus further improving the cycle performance and charging rate of the secondary battery.

[0023] In any embodiment, the carbon-based anode active material is selected from one or more of hard carbon, soft carbon, graphite, and Ketjen black. Using the aforementioned carbon-based anode active material ensures that the battery cell has a high energy density.

[0024] A second aspect of this application also provides a method for preparing a negative electrode sheet, comprising the following steps:

[0025] (1) Provide ceramic materials, the relative permittivity ε of the ceramic materials and the cell parameters a and c are related by the formula ε / (c / a) with values ​​ranging from 78.8 to 197.9;

[0026] (2) A negative electrode sheet is prepared by using a negative electrode slurry containing ceramic material, carbon-based negative electrode active material and binder obtained in step (1); wherein the weight ratio of ceramic material to carbon-based negative electrode active material is 0.0052-0.115, or optionally 0.0052-0.057.

[0027] Therefore, this application improves the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film by using ceramic materials with a specific relationship between dielectric constant and cell parameters in a certain proportion with carbon-based negative electrode active materials, thereby reducing the risk of lithium dendrite formation, reducing the degree of lithium plating, forming a thinner SEI film, reducing the consumption of active lithium ions and electrolyte, thereby reducing the interfacial film impedance of the negative electrode sheet and improving the cycle performance and charging rate of the secondary battery.

[0028] In any embodiment, in step (1), the ceramic material is obtained by ball milling;

[0029] Optionally, the ball mill rotation speed is 200-300 r / min;

[0030] Optionally, the ball milling time is 2-4 hours.

[0031] The ceramic material obtained by the above ball milling process has a specific relationship between its relative permittivity and cell parameters. When this ceramic material is combined with carbon-based anode active material in a certain proportion, the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film can be improved, the risk of lithium dendrite formation can be reduced, the thickness of the SEI film can be reduced, and the consumption of active lithium ions and electrolyte can be reduced, thereby reducing the interfacial film impedance of the anode sheet and improving the cycle performance and charging rate of the secondary battery.

[0032] In any embodiment, in step (2), the weight ratio of ceramic material to binder is 0.1-10, optionally 0.5-1.

[0033] A third aspect of this application provides a secondary battery, including a negative electrode sheet prepared by the method of the first aspect of this application or the method of the second aspect of this application, and an electrolyte.

[0034] In any embodiment, the ratio of the relative permittivity of the electrolyte to the relative permittivity of the ceramic material in the negative electrode is 1:3-1:1, and can be selected as 0.45:1-1:1.

[0035] This allows the relative permittivity of the ceramic material and the electrolyte to be matched, thereby increasing the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, reducing the risk of lithium dendrite formation and the degree of lithium plating, reducing the thickness of the SEI film, reducing the consumption of active lithium ions and electrolyte, and thus reducing the interfacial impedance of the negative electrode, improving the cycle performance and charging rate of the secondary battery.

[0036] A fourth aspect of this application provides a battery module including the secondary battery of the third aspect of this application.

[0037] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0038] A sixth aspect of this application provides an electrical device comprising at least one selected from the third aspect of this application, the fourth aspect of this application, and the fifth aspect of this application. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0040] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0041] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0042] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0043] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0044] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0045] Figure 7A This is a photograph of the surface of the negative electrode sheet in Embodiment 1 of this application.

[0046] Figure 7B This is a photograph of the surface of the negative electrode sheet in Comparative Example 1 of this application.

[0047] Figure 8 This is the EDS energy spectrum of the negative electrode sheet in Embodiment 1 of this application.

[0048] Figure 9 This is the XRD pattern of the ceramic material in Example 1 of this application.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0051] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the negative electrode sheet, the method for preparing the negative electrode sheet, the secondary battery, the battery module, the battery pack, and the power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0052] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0054] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0055] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0056] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0057] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0058] Unless otherwise specified, in this application, the term "cell parameters" refers to the fact that the shape and size of a unit cell can be represented by six parameters, namely, lattice characteristic parameters, or simply unit cell parameters. These are a set of parameters that determine the shape and size of the unit cell. They include the three sets of edge lengths (i.e., the axial lengths of the crystal) a, b, and c, and the included angles between the three sets of edges (i.e., the axial angles of the crystal) α, β, and γ.

[0059] [Rechargeable Battery]

[0060] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after being discharged to activate the active materials and continue to be used.

[0061] Typically, a secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, also positioned between the positive and negative electrodes, mainly serves to conduct active ions.

[0062] [Negative electrode plate]

[0063] One embodiment of this application provides a negative electrode sheet comprising a ceramic material, a carbon-based negative electrode active material, and a binder; wherein the relative permittivity ε of the ceramic material is related to the cell parameters a and c by the formula ε / (c / a), which takes the value of 78.8-197.9 (e.g., 89.1, 118.7), and the weight ratio of the ceramic material to the carbon-based negative electrode active material is 0.0052-0.115, optionally 0.0052-0.057, more preferably 0.0104-0.054 or 0.01-0.05, for example 0.0103, 0.0105, 0.0326.

[0064] In current rechargeable battery charging and discharging processes, the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film are limiting steps, leading to the easy accumulation of lithium ions at the interface between the SEI film and the negative electrode. When the accumulation of lithium ions exceeds the nucleation barrier, lithium dendrites are formed. Due to the excellent conductivity of lithium metal, lithium ions preferentially accumulate at the lithium dendrites and are reduced to metallic lithium, which exacerbates the formation of lithium dendrites and the degree of lithium plating, resulting in a large consumption of active lithium ions. Furthermore, the formation of lithium dendrites is accompanied by the rupture and continuous generation of the SEI film, further causing the consumption of active lithium ions and electrolyte. The large consumption of active lithium and the lithium plating problem cause a decline in the cycle performance of the rechargeable battery. In addition, the SEI film formed on the surface of the current negative electrode is relatively thick, resulting in a large amount of electrolyte consumption, a long migration path for lithium ions, a high interfacial impedance of the negative electrode, and a low charging rate of the rechargeable battery.

[0065] Although the mechanism is not yet clear, the applicant unexpectedly discovered that by using a ceramic material with a specific relationship between its relative permittivity and cell parameters in a certain proportion with a carbon-based anode active material, the ceramic material particles are uniformly dispersed in the carbon-based anode active material. This reduces the lithium-ion desolvation barrier, increases the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, reduces the risk of lithium dendrite formation, reduces the degree of lithium plating, and reduces the consumption of active lithium ions, thereby improving the cycle performance and charging rate of the secondary battery. Moreover, the specific ceramic material of this application exhibits certain properties during the charging process. The reverse electric field generated in the electrolyte creates an electron-depleted state at the three-phase interface of the electrolyte, ceramic material, and carbon-based negative electrode active material, enabling the formation of a thinner SEI film. This further reduces the consumption of active lithium ions and electrolyte, thereby improving the cycle performance of the secondary battery. The thinner SEI film shortens the migration path of lithium ions within the SEI film and also reduces the interfacial impedance of the negative electrode, increasing the charging rate of the secondary battery. Simultaneously, the negative charge generated by the ceramic material helps disperse lithium ions enriched at the interface between the SEI film and the negative electrode, further reducing the risk of lithium dendrite formation.

[0066] In some embodiments, the relative permittivity ε of the ceramic material is 80-200, for example 90 or 120. Therefore, with the relative permittivity of the ceramic material within this range, the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film can be further improved, thereby further reducing the risk of lithium plating, reducing the thickness of the SEI film, and thus further improving the cycle performance and charging rate of the secondary battery.

[0067] In some embodiments, the ceramic material has a weight percentage of 0.5%-10% in the negative electrode sheet, optionally 0.5%-5%, such as 1% or 3%.

[0068] Therefore, when the weight content of ceramic material in the negative electrode sheet is within the above range, it can further improve the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, further reduce the degree of lithium plating, further reduce the thickness of the SEI film, and thus further improve the cycle performance and charging rate of the secondary battery.

[0069] In some embodiments, the ceramic material is one or more selected from barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, and lead barium lithium niobate, and optionally barium titanate and / or lead titanate.

[0070] The relative permittivity of the ceramic materials described above is more closely matched with that of the electrolyte, which can further improve the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, thereby reducing the risk of lithium dendrite formation. Furthermore, the use of these ceramic materials can further reduce the thickness of the SEI film, thereby further improving the cycle performance and charging rate of the secondary battery.

[0071] In some embodiments, the particle size D of the ceramic material v 50 represents 10-300nm, and can be selected as 50-200nm, such as 100nm.

[0072] Therefore, the ceramic materials with the above-mentioned particle size range are more tightly bonded to the carbon-based negative electrode active materials, which further improves the lithium-ion desolvation effect, further reduces the thickness of the SEI film, and thus further improves the cycle performance and charging rate of the secondary battery.

[0073] In some embodiments, the particle size D of the carbon-based anode active material v 50 is 1-15μm, and can be selected as 5-10μm.

[0074] Therefore, the bonding between carbon-based anode active materials and ceramic materials within the aforementioned particle size range is more compact, which further improves the lithium-ion desolvation rate, further reduces the thickness of the formed SEI film, and thus further improves the cycle performance and charging rate of the secondary battery.

[0075] In some embodiments, the weight ratio of ceramic material to binder is 0.1-10, optionally 0.5-1, for example 5.

[0076] The composite material particles formed by ceramic materials and binders within the above-mentioned ratio range are more tightly bonded to the carbon-based negative electrode active material, thereby further improving the lithium-ion desolvation rate, further reducing the thickness of the formed SEI film, and thus further improving the cycle performance and charging rate of the secondary battery.

[0077] In some embodiments, the adhesive is one or more selected from polyacrylic acid, styrene-butadiene rubber, polyvinylidene fluoride, polyamide-imide, polyvinyl alcohol, polyethyleneimine, polyimide, and poly(tert-butyl acrylate-triethoxyvinylsilane), and may be styrene-butadiene rubber and / or polyvinylidene fluoride.

[0078] In some embodiments, the weight-average molecular weight of the adhesive is 500,000 to 4,000,000, optionally 1,000,000 to 2,000,000, for example 1,500,000; optionally, the molecular weight distribution index of the adhesive is 2 to 10, more preferably 2 to 4.

[0079] The aforementioned binder enables a tighter bond between the ceramic material and the carbon-based anode active material, further improving the lithium-ion desolvation rate, further reducing the thickness of the SEI film, and further reducing the consumption of active lithium ions, thereby improving the cycle performance and charging rate of the secondary battery.

[0080] In some embodiments, the ceramic material is barium titanate, which has two crystal forms: cubic and tetragonal; preferably, it is tetragonal.

[0081] In some embodiments, barium titanate, when irradiated with Cu-Kα, exhibits peaks at the following positions in its X-ray powder diffraction pattern, expressed in 2θ angles: 22±1°, 31±1°, 38±1°, 45±1°, and 56±1°.

[0082] Using barium titanate as a ceramic material can further improve the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, thereby further reducing the risk of lithium plating, reducing the thickness of the SEI film, and thus further improving the cycle performance and charging rate of the secondary battery.

[0083] In some embodiments, the carbon-based anode active material is selected from one or more of hard carbon, soft carbon, graphite, and Ketjen black, and may be selected from hard carbon and / or graphite (e.g., artificial graphite). Using the aforementioned carbon-based anode active material ensures that the battery cell has a high energy density.

[0084] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; ceramic material, carbon-based negative electrode active material and binder are contained in the negative electrode film layer.

[0085] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0086] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0087] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0089] In this application, the relative permittivity of ceramic materials refers to the relative permittivity at room temperature (25±5℃), which has a meaning known in the art and can be tested using instruments and methods known in the art.

[0090] In this application, the particle size D v 50 was determined by a particle size analyzer.

[0091] In this application, the ratio of the unit cell parameter c-axis to a-axis, c / a, can be calculated using the software included with the X-ray diffractometer based on the XRD pattern analysis of the material.

[0092] [Methods for preparing negative electrode sheets]

[0093] The method for preparing the negative electrode sheet in this application includes the following steps:

[0094] (1) Provide ceramic materials, the relative permittivity ε of the ceramic materials and the cell parameters a and c are related by the formula ε / (c / a) which takes the value of 78.8-197.9, for example 89.1, 118.7;

[0095] (2) A negative electrode sheet is prepared by using a negative electrode slurry containing ceramic material, carbon-based negative electrode active material and binder obtained in step (1); wherein the weight ratio of ceramic material to carbon-based negative electrode active material is 0.0052-0.115, optionally 0.0052-0.057, more preferably 0.0104-0.054 or 0.01-0.05, for example 0.0103, 0.0105, 0.0326.

[0096] Therefore, this application improves the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film by using ceramic materials with a specific relationship between dielectric constant and cell parameters in a certain proportion with carbon-based negative electrode active materials, thereby reducing the risk of lithium dendrite formation, reducing the degree of lithium plating, forming a thinner SEI film, reducing the consumption of active lithium ions and electrolyte, thereby reducing the interfacial film impedance of the negative electrode sheet and improving the cycle performance and charging rate of the secondary battery.

[0097] In some embodiments, in step (1), the ceramic material is obtained by ball milling;

[0098] Optionally, the ball mill rotation speed is 200-300 r / min;

[0099] Alternatively, the ball milling time is 2-4 hours, for example, 3 hours.

[0100] The ceramic material obtained by the above ball milling process has a specific relationship between its relative permittivity and cell parameters. When this ceramic material is combined with carbon-based anode active material in a certain proportion, the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film can be improved, the risk of lithium dendrite formation can be reduced, the thickness of the SEI film can be reduced, and the consumption of active lithium ions and electrolyte can be reduced, thereby reducing the interfacial film impedance of the anode sheet and improving the cycle performance and charging rate of the secondary battery.

[0101] In some embodiments, in step (2), the weight ratio of ceramic material to binder is 0.1-10, optionally 0.5-1, for example 5.

[0102] In some embodiments, the negative electrode slurry comprising the ceramic material obtained in step (1), the carbon-based negative electrode active material, and the binder is obtained through the following steps:

[0103] The ceramic material, carbon-based anode active material, binder and any other components obtained in step (1) are dispersed in a solvent (e.g., deionized water) to form an anode slurry.

[0104] In some implementations, the negative electrode sheet is prepared using a negative electrode slurry in the following manner:

[0105] The negative electrode slurry is coated onto the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0106] In some implementations, ceramic materials are used as described in "[Negative Electrode Sheet]".

[0107] In some embodiments, carbon-based anode active materials are as described in "[Anode Sheets]".

[0108] In some implementations, the binder is as described in "[Negative Electrode]".

[0109] [Positive electrode plate]

[0110] A positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0111] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0112] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0113] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0114] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0115] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0116] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0117] [Isolation membrane]

[0118] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0119] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0120] [Electrolytes]

[0121] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0122] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0123] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0124] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0125] In some embodiments, the electrolyte may optionally include additives. As examples, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0126] In the prior art, the dielectric constant of electrolytes is usually in the range of 30-80.

[0127] In some embodiments, the ratio of the relative permittivity of the electrolyte to the relative permittivity of the ceramic material in the negative electrode is 1:3 to 1:1, and can be selected as 0.45:1 to 1:1.

[0128] This allows the relative permittivity of the ceramic material and the electrolyte to be matched, thereby increasing the lithium-ion desolvation rate and the lithium-ion diffusion rate in the SEI film, reducing the risk of lithium dendrite formation and the degree of lithium plating, reducing the thickness of the SEI film, reducing the consumption of active lithium ions and electrolyte, and thus reducing the interfacial impedance of the negative electrode, improving the cycle performance and charging rate of the secondary battery.

[0129] In this application, the relative permittivity of the electrolyte can be determined by a relative permittivity tester, for example, referring to GB / T5594.4-1985.

[0130] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0131] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0132] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0133] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0134] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0135] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0136] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0137] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0138] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0139] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0140] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0141] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0142] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0143] [Example]

[0144] 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.

[0145] Example 1

[0146] (1) Preparation of ceramic materials:

[0147] Take 100g of barium titanate particles (relative permittivity ε is 30, particle size D) v 50 (100 nm) particles were added to a ball mill jar and ball-milled at 300 r / min for 2 h. The resulting barium titanate particles had a relative permittivity ε of 90, a cell parameter c / a of 1.010621, and a relative permittivity to cell parameter relationship ε / (c / a) of 89.05415581. The particle size D... v 50 refers to 50nm.

[0148] (2) Preparation of negative electrode sheet:

[0149] Artificial graphite (particle size D) is used as the negative electrode active material. v The negative electrode slurry was prepared by dissolving barium titanate particles obtained in step (1) in deionized water at a mass ratio of 96:1:1:1:1. The mixture was thoroughly stirred and mixed to form a negative electrode slurry. The negative electrode slurry was then subjected to a concentration of 9.6 mg / cm³. The slurry was prepared with acetylene black as the conductive agent, styrene-butadiene rubber (SBR) as the binder (weight-average molecular weight 1.5 million, molecular weight distribution index 2), sodium carboxymethyl cellulose (CMC-Na) as the dispersant. 2 The areal density (after drying) is uniformly coated on a 7μm thick negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0150] (3) Preparation of the positive electrode sheet:

[0151] Lithium nickel cobalt manganese oxide (LiNi) is used as the positive electrode active material. 0.5 Co 0.2 Mn 0.3 O2), binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black were dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 98:1:1. The mixture was thoroughly stirred and mixed under vacuum to prepare a positive electrode slurry. The positive electrode slurry was then subjected to a concentration of 13.7 mg / cm³. 2 The areal density (after drying) is uniformly coated on a 13μm thick positive current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0152] (4) Separating membrane:

[0153] A commercially available PP-PE copolymer microporous membrane with a thickness of 20 μm and an average pore size of 80 nm (purchased from Zogo Electronics Technology Co., Ltd., model 20) was used.

[0154] (5) Preparation of electrolyte:

[0155] In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) / ethyl methyl carbonate (EMC) organic solvents were mixed thoroughly at a volume ratio of 3 / 7. Then, 12.5% ​​by weight (based on the weight of the ethylene carbonate / ethyl methyl carbonate solvents) of LiPF6 was added and dissolved in the organic solvent. The mixture was stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L, and the dielectric constant of the electrolyte was 90.

[0156] (6) Preparation of secondary batteries:

[0157] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, and the electrolyte prepared above is added. After processes such as encapsulation, standing, formation, and aging, a secondary battery is obtained.

[0158] (7) Fabrication of button cells:

[0159] The positive electrode, separator, and negative electrode are stacked sequentially on a 2032 coin cell, and electrolyte is added. The cells are then sealed under a pressure of 0.35 MPa to obtain the final product.

[0160] Examples 2-28 and Comparative Examples 1-9

[0161] Examples 2-28 and Comparative Examples 1-9 are similar to the secondary battery preparation method in Example 1, but the parameters have been adjusted. Details of the different parameters are shown in Table 1. All other parameters are the same as in Example 1. Wherein, w1 represents the weight percentage of ceramic material in the negative electrode sheet, w2 represents the weight percentage of carbon-based negative electrode active material in the negative electrode sheet, m1 represents the weight of ceramic material in the negative electrode sheet, m2 represents the weight of carbon-based negative electrode active material in the negative electrode sheet, and m3 represents the weight of binder in the negative electrode sheet; the weight percentages of conductive agent and dispersant in the negative electrode slurry are the same.

[0162]

[0163]

[0164] Performance testing

[0165] (1) Method for testing relative permittivity ε:

[0166] The method for testing the relative permittivity ε of ceramic materials is as follows: After preparing the material to be tested into a circular sample, the capacitance C is measured using an LCR meter, and the relative permittivity ε is calculated according to the formula: Relative permittivity ε=(C×d) / (ε0×A); where C represents the capacitance in farads (F); d represents the sample thickness in cm; and A represents the sample area in cm². 2 ε0 represents the vacuum permittivity, ε0 ​​= 8.854 × 10⁻⁶. -14 F / cm. Test conditions are 1kHz, 1.0V, 25±5℃. Test standards can be based on GB / T11297.11-2015. For sample preparation, refer to Chinese patent application CN114217139A.

[0167] Test method for the relative permittivity ε of electrolyte: Refer to GB / T5594.4-1985 and use the ZJD-C relative permittivity tester of Beijing Zhonghang Times Instrument Equipment Co., Ltd.

[0168] The results are shown in Table 1.

[0169] (2) The particle size D was determined using a particle size analyzer. v 50, the results are shown in Table 1.

[0170] (3) Charge the secondary batteries of Example 1 and Comparative Example 1 at a 4C rate, then take pictures and observe the lithium plating on the surface of the negative electrode.

[0171] Depend on Figures 7A-7B It can be seen that, under full charge, the negative electrode sheet of Example 1 has less lithium deposition on its surface, while the negative electrode sheet of Comparative Example 1 has severe lithium deposition on its surface and some parts have purple spots. This indicates that the negative electrode sheet of the present invention is not prone to lithium deposition on its surface, and lithium deposition is effectively suppressed.

[0172] (4) The EDS energy spectrum of the negative electrode sheet of Example 1 was measured;

[0173] Depend on Figure 8 It can be seen that the barium titanate in the negative electrode sheet of Example 1 is evenly distributed, which is beneficial to the fast charging effect.

[0174] (5) The XRD patterns of the ceramic materials were determined using an X-ray diffractometer. The measurement conditions were: Cu-Kα radiation was used, and the test angle was from 10° to 80°. The ratio of the c-axis to the a-axis of the unit cell parameter c / a was calculated using the software built into the X-ray diffractometer, and ε / (c / a) was further calculated.

[0175] Figure 9The XRD spectrum of the ceramic material in Example 1 includes peaks at the following positions: 22±1°, 31±1°, 38±1°, 45±1°, and 56±1°. Analysis using the built-in XRD software shows that barium titanate contains both cubic and tetragonal crystal forms.

[0176] (6) Determination of coin cell capacity:

[0177] The coin cell was charged at 0.1C to 4.3V within the range of 2.5 to 4.3V. Then, it was charged at a constant voltage of 4.3V until the current was less than or equal to 0.05mA. After resting for 5 minutes, it was discharged at 0.1C to 2.0V. The discharge capacity at this point is the initial specific capacity. The specific capacity of the positive electrode is obtained by dividing the initial specific capacity by the weight of the positive electrode active material.

[0178] (7) Initial determination of coulombic efficiency:

[0179] At 25℃ and normal pressure, the coin cell was discharged at a constant current rate of 0.1C to a voltage of 0.005V, and then discharged at a constant current rate of 0.05C to a voltage of 0.005V. The discharge specific capacity at this point was recorded, which is the initial lithium insertion capacity. Afterward, it was charged at a constant current rate of 0.1C to a voltage of 1.5V, and the charging specific capacity at this point was recorded, which is the initial lithium de-lithiation capacity. The coin cell was subjected to 50 charge-discharge cycles using the above method, and the lithium de-lithiation capacity was recorded each time.

[0180] Initial coulombic efficiency (%) = Initial delithiation capacity / Initial lithiation capacity × 100%

[0181] (8) Measurement of 4C charging resistance:

[0182] The kinetic performance of the secondary battery was evaluated by measuring the 4C charging resistance. At 25°C, the secondary batteries prepared in the examples and comparative examples were first discharged to 50% capacity, allowed to stand for 30 minutes, and the voltage value V1 was recorded. The batteries were then charged for 10 seconds with a current A0 corresponding to the 4C rate (current A0 = rate × A0 rated capacity, where A0 rated capacity is the capacity obtained by assembling the electrodes into a full cell), and the voltage value V2 corresponding to the end of charging was recorded. The charging resistance was calculated according to the following formula, and then normalized using Comparative Example 1 as 100 to obtain the result.

[0183] R = (V2 - V1) / A0

[0184] (9) Determination of fast charging cycle life at 25℃:

[0185] The capacity retention performance of the secondary batteries was evaluated by measuring the fast-charge cycle life at 25°C. At 25°C, the secondary batteries prepared in the examples and comparative examples were charged at a 2C rate and discharged at a 1C rate, undergoing continuous cycling tests within the 3%–97% SOC range until the capacity of the secondary batteries was less than 80% of the initial capacity, and the number of cycles was recorded.

[0186] (10) Measurement of fast charging time:

[0187] The second-generation battery was charged for the first time at a 5C rate, from 10% SOC to 80% SOC. The charging time was recorded, which is the fast charging time.

[0188] The results of items (6)-(10) above are shown in Table 2.

[0189] Table 2: Performance test results of Examples 1-28 and Comparative Examples 1-9

[0190]

[0191]

[0192] As shown in Table 1-2:

[0193] Compared with the secondary batteries of Comparative Examples 1-9, the secondary battery made with the negative electrode sheet of this application has a longer fast-charging cycle life, better cycle performance, and faster charging rate.

[0194] Comparing Example 1 with Examples 19-20, it can be seen that the secondary battery made of the negative electrode sheet with a ceramic material and binder weight ratio of 0.5-1 in this application has a further extended fast-charging cycle life, further improved cycle performance, and further increased charging rate.

[0195] Comparing Example 1 with Examples 7 and 21, it can be seen that the particle size D of the ceramic material used in this application is... v The fast-charging cycle life of secondary batteries made with negative electrode sheets of 50-200nm is further extended, and the cycle performance is further improved.

[0196] Comparing Example 1 with Examples 11 and 22, it can be seen that the particle size D of the carbon-based anode active material used in this application is [not specified]. v The fast-charging cycle life of secondary batteries made with 50 negative electrode sheets of 5-10μm is further extended, the cycle performance is further improved, and the charging rate is further increased.

[0197] Comparing Example 1 with Examples 23-24, it can be seen that the secondary battery made with a binder of 1 million to 2 million weight-average molecular weight in this application has a further extended fast-charging cycle life and a further improved cycle performance.

[0198] Comparing Example 1 with Example 25, it can be seen that the secondary battery made with a negative electrode sheet using a binder with a molecular weight distribution index of 2-4 has a further extended fast-charging cycle life, further improved cycle performance, and further increased charging rate.

[0199] Comparing Example 1 with Example 27, it can be seen that the secondary battery made of negative electrode sheet with ceramic material weight percentage of 0.5%-5% in this application has a further extended fast-charging cycle life, further improved cycle performance, and further increased charging rate.

[0200] Comparing Example 1 with Example 28, it can be seen that the secondary battery prepared in this application with a ratio of the relative permittivity of the electrolyte to the relative permittivity of the ceramic material of 0.45:1-1:1 has a further extended fast-charging cycle life, further improved cycle performance, and further increased charging rate.

[0201] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A negative electrode sheet, comprising a ceramic material, a carbon-based negative electrode active material, and a binder; wherein, The relative permittivity ε of the ceramic material is related to the cell parameters a and c by the formula ε / (c / a), which has a value of 78.8-197.

9. The weight ratio of the ceramic material to the carbon-based negative electrode active material is 0.0052-0.

115. The weight-average molecular weight of the binder is 1 million-2 million. The relative permittivity ε of the ceramic material is 80-200. The weight percentage of the ceramic material in the negative electrode sheet is 0.5%-10%.

2. The negative electrode sheet according to claim 1, wherein, The weight ratio of the ceramic material to the carbon-based anode active material is 0.0052-0.

057.

3. The negative electrode sheet according to claim 1, wherein, The ceramic material has a weight percentage of 0.5%-5% in the negative electrode sheet.

4. The negative electrode sheet according to claim 1, wherein, The ceramic material is selected from one or more of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, and lead barium lithium niobate.

5. The negative electrode sheet according to claim 1, wherein, The particle size D of the ceramic material v 50 represents 10-300nm.

6. The negative electrode sheet according to claim 1, wherein, The particle size D of the ceramic material v 50 refers to 50-200nm.

7. The negative electrode sheet according to claim 1, wherein, The particle size D of the carbon-based anode active material v 50 represents 1-15 μm.

8. The negative electrode sheet according to claim 1, wherein, The particle size D of the carbon-based anode active material v 50 represents 5-10 μm.

9. The negative electrode sheet according to claim 1, wherein, The weight ratio of the ceramic material to the binder is 0.1-10.

10. The negative electrode sheet according to claim 1, wherein, The weight ratio of the ceramic material to the binder is 0.5-1.

11. The negative electrode sheet according to claim 1, wherein, The adhesive is selected from one or more of polyacrylic acid, styrene-butadiene rubber, polyvinylidene fluoride, polyamide-imide, polyvinyl alcohol, polyethyleneimine, polyimide, and poly(tert-butyl acrylate-triethoxyvinylsilane).

12. The negative electrode sheet according to claim 11, wherein, The molecular weight distribution index of the adhesive is 2-10.

13. The negative electrode sheet according to claim 11, wherein, The molecular weight distribution index of the adhesive is 2-4.

14. The negative electrode sheet according to claim 1, wherein, The ceramic material is barium titanate, which contains two crystal forms: cubic and tetragonal.

15. The negative electrode sheet according to claim 1, wherein, The carbon-based anode active material is selected from one or more of hard carbon, soft carbon, and graphite.

16. A method for preparing a negative electrode sheet, comprising the following steps: (1) Provide a ceramic material, wherein the relative permittivity ε of the ceramic material and the cell parameters a and c are expressed in the form ε / (c / a) which has a value of 78.8-197.9; (2) A negative electrode sheet is prepared using a negative electrode slurry comprising the ceramic material obtained in step (1), a carbon-based negative electrode active material, and a binder; wherein, The weight ratio of the ceramic material to the carbon-based negative electrode active material is 0.0052-0.115; the weight-average molecular weight of the binder is 1 million to 2 million; the relative permittivity ε of the ceramic material is 80-200; and the weight percentage of the ceramic material in the negative electrode sheet is 0.5%-10%.

17. The method according to claim 16, wherein, The weight ratio of the ceramic material to the carbon-based anode active material is 0.0052-0.

057.

18. The method according to claim 16, wherein, In step (1), the ceramic material is obtained by ball milling.

19. The method according to claim 18, wherein, The ball mill rotates at a speed of 200-300 r / min.

20. The method according to claim 18, wherein, The ball milling time is 2-4 hours.

21. The method according to claim 16, wherein, In step (2), the weight ratio of the ceramic material to the binder is 0.1-10.

22. The method according to claim 21, wherein, In step (2), the weight ratio of the ceramic material to the binder is 0.5-1.

23. A secondary battery comprising a negative electrode sheet according to any one of claims 1 to 15 or a negative electrode sheet prepared by the method according to any one of claims 16 to 22, and an electrolyte.

24. The secondary battery according to claim 23, wherein, The ratio of the relative permittivity of the electrolyte to the relative permittivity of the ceramic material in the negative electrode is 1:3 to 1:

1.

25. The secondary battery according to claim 24, wherein, The ratio of the relative permittivity of the electrolyte to the relative permittivity of the ceramic material in the negative electrode is 0.45:1 to 1:

1.

26. A battery module comprising the secondary battery according to any one of claims 23 to 25.

27. A battery pack comprising the battery module of claim 26.

28. An electrical device comprising at least one selected from the secondary battery of any one of claims 23 to 25, the battery module of claim 26, and the battery pack of claim 27.

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