WO2024011512A1

WO2024011512A1 - Negative electrode plate, negative electrode plate preparation method, secondary battery, battery module, battery pack, and electrical device

Info

Publication number: WO2024011512A1
Application number: PCT/CN2022/105761
Authority: WO
Inventors: 白文龙; 吴益扬; 游兴艳; 武宝珍; 王育文; 郑蔚; 叶永煌; 吴凯
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2022-07-14
Filing date: 2022-07-14
Publication date: 2024-01-18
Also published as: CN116848658A

Abstract

The present application provides a negative electrode plate, a negative electrode plate preparation method, a secondary battery, a battery module, a battery pack, and an electrical device. The negative electrode plate comprises a ceramic material, a carbon-based negative electrode active material, and a binder, wherein the value of the relation ε/(c/a) between a relative dielectric constant ε and lattice parameters a and c of the ceramic material 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 plate of the present application can increase the rate of lithium ion desolvation, reduce the degree of lithium plating on a negative electrode plate, reduce the thickness of a formed SEI film, and reduce the consumption of active lithium ions, thereby reducing the interface impedance of the negative electrode plate, and improving the cycle life and charging rate of secondary batteries.

Description

Negative electrode plate, method for preparing negative electrode plate, secondary battery, battery module, battery pack and electrical device

Technical field

The present application relates to the technical field of secondary batteries, and in particular to a negative electrode plate, a method for preparing a negative electrode plate, a secondary battery, a battery module, a battery pack and an electrical device.

Background technique

In recent years, as the application range of secondary batteries has become more and more extensive, secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development of secondary batteries, higher requirements have been put forward for their energy density, cycle performance and safety performance. The interface between the existing negative electrode plate and the electrolyte is prone to lithium precipitation, causing the consumption of active lithium ions, resulting in a reduction in the cycle performance of the secondary battery. Moreover, the SEI film on the surface of the existing negative electrode plate is thick, resulting in secondary battery failure. The interface film resistance of the battery increases and the charging rate decreases. At the same time, the formation of a thick SEI film also consumes a large amount of electrolyte. Therefore, there is an urgent need for a negative electrode plate that solves the above technical problems.

Contents of the invention

This application was made in view of the above problems, and its purpose is to provide 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. The negative electrode sheet of this application can increase the desolvation rate of lithium ions, reduce the degree of lithium precipitation 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. Moreover, the surface of the negative electrode sheet of this application can The formation of a SEI film with a smaller thickness shortens the migration path of lithium ions, increases the charging rate of secondary batteries, and reduces electrolyte consumption.

In order to achieve the above purpose, the first aspect of the present application provides a negative electrode sheet, which includes a ceramic material, a carbon-based negative active material and a binder; wherein, the relative dielectric constant ε of the ceramic material and the unit cell parameters a and c are The value of the relational expression ε/(c/a) is 78.8-197.9, and the weight ratio of ceramic materials to carbon-based negative active materials is 0.0052-0.115, optionally 0.0052-0.057.

Therefore, this application improves the desolvation rate of lithium ions and the diffusion of lithium ions in the SEI film by combining ceramic materials with a specific relationship between relative dielectric constant and unit cell parameters and carbon-based negative active materials in a certain proportion. rate, reducing the risk of generating lithium dendrites, reducing the degree of lithium precipitation, forming a SEI film with a smaller thickness, reducing the consumption of active lithium ions and electrolyte, thereby improving the cycle performance and charging rate of secondary batteries. .

In any embodiment, the ceramic material has a relative dielectric constant ε of 80-200. Therefore, the relative dielectric constant of ceramic materials within the above range can further increase the lithium ion desolvation rate and the lithium ion diffusion rate in the SEI film to further reduce the risk of lithium precipitation and reduce the thickness of the SEI film, thereby further Improve the cycle performance and charging rate of secondary batteries.

In any embodiment, the weight percentage of the ceramic material in the negative electrode sheet is 0.5%-10%, optionally 0.5%-5%.

Therefore, the weight content of ceramic materials in the negative electrode sheet is within the above range, which can further increase the lithium ion desolvation rate and the lithium ion diffusion rate in the SEI film, further reduce the degree of lithium evolution, and further reduce the thickness of the SEI film. , thereby further improving the cycle performance and charging rate of secondary batteries.

In any embodiment, the ceramic material is one or more selected from the group consisting of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, and lead barium lithium niobate.

The relative dielectric constant of the above-mentioned types of ceramic materials is more consistent with that of the electrolyte, which can further increase the lithium ion desolvation rate and the lithium ion diffusion rate in the SEI film to reduce the risk of lithium dendrites. Moreover, the use of the above types of ceramic materials can further reduce the thickness of the SEI film, thereby further improving the cycle performance and charging rate of the secondary battery.

In any embodiment, the particle size D _v 50 of the ceramic material is 10-300 nm, optionally 50-200 nm.

As a result, ceramic materials in the above particle size range are more closely combined with carbon-based negative active materials to further improve the lithium ion desolvation effect and further reduce the thickness of the SEI film, thereby further improving the cycle performance and performance of secondary batteries. Charging rate.

In any embodiment, the particle size D _v 50 of the carbon-based negative active material is 1-15 μm, optionally 5-10 μm.

As a result, the bond between the carbon-based negative active material and the ceramic material in the above particle size range is closer, so as to further increase the desolvation rate of lithium ions and further reduce the thickness of the formed SEI film, thereby further improving the secondary battery cycle performance and charging rate.

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

The composite particles formed by the ceramic materials and binders in the above proportion range are more closely combined with the carbon-based negative active material to further increase the desolvation rate of lithium ions and further reduce the thickness of the SEI film formed, thereby further improving Cycling performance and charging rates of secondary batteries.

In any embodiment, the binder is selected from the group consisting of polyacrylic acid, styrene-butadiene rubber, polyvinylidene fluoride, polyamideimide, polyvinyl alcohol, polyethyleneimine, polyimide, and poly(tert-butyl acrylate). One or more of ester-triethoxyvinylsilane).

In any embodiment, the weight average molecular weight of the binder is 500,000-4 million, optionally 1 million-2 million; optionally, the molecular weight distribution index of the binder is 2-10, more preferably 2-2 4.

The use of the above-mentioned binder can make the ceramic material and the carbon-based negative active material more tightly combined, further increase the desolvation rate of lithium ions, further reduce the thickness of the SEI film, further reduce the consumption of active lithium ions, thereby improving the secondary battery cycle performance and charging rate.

In any embodiment, the ceramic material is barium titanate, and barium titanate includes two crystal forms: cubic crystal form and tetragonal crystal form; the tetragonal crystal form is preferred.

In any embodiment, barium titanate has peaks at the following positions in an X-ray powder diffraction pattern expressed in 2θ angles using Cu-Kα radiation: 22±1°, 31±1°, 38±1°, 45 ±1°, 56±1°.

Using the above-mentioned barium titanate as a ceramic material can further increase the lithium ion desolvation rate and the lithium ion diffusion rate in the SEI film to further reduce the risk of lithium precipitation and reduce the thickness of the SEI film, thereby further improving the cycle of the secondary battery. performance and charging rates.

In any embodiment, the carbon-based negative active material is selected from one or more of hard carbon, soft carbon, graphite, and Ketjen black. The use of the above-mentioned carbon-based negative active materials can ensure that the battery core has a high energy density.

A second aspect of the application also provides a method for preparing a negative electrode sheet, including the following steps:

(1) Provide ceramic materials. The relationship between the relative dielectric constant ε of ceramic materials and the unit cell parameters a and c has a value of ε/(c/a) of 78.8-197.9;

(2) Use the negative electrode slurry including the ceramic material obtained in step (1), the carbon-based negative active material and the binder to prepare the negative electrode piece; wherein the weight ratio of the ceramic material to the carbon-based negative active material is 0.0052-0.115 , optional 0.0052-0.057.

Therefore, this application improves the desolvation rate of lithium ions and the diffusion rate of lithium ions in the SEI film by combining ceramic materials with a specific relationship between dielectric constant and unit cell parameters and carbon-based negative active materials in a certain proportion. , reduces the risk of lithium dendrites, reduces the degree of lithium precipitation, forms a SEI film with a smaller thickness, reduces the consumption of active lithium ions and electrolyte, thereby reducing the interface film resistance of the negative electrode piece and improving Cycling performance and charging rates of secondary batteries.

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

Optionally, the speed of the ball mill is 200-300r/min;

Optionally, the ball milling time is 2-4h.

The above-mentioned ball milling process is used to obtain ceramic materials, whose relative dielectric constant has a specific relationship with the unit cell parameters. Combining the ceramic materials with the carbon-based negative active material in a certain proportion can increase the lithium ion desolvation rate and the lithium ion in the SEI film. Medium diffusion rate, reducing the risk of lithium dendrites, reducing the thickness of the SEI film, reducing the consumption of active lithium ions and electrolyte, thereby reducing the interface film resistance of the negative electrode piece, and improving the cycle performance and charging rate of the secondary battery.

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

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

In any embodiment, the ratio of the relative dielectric constant of the electrolyte to the relative dielectric constant of the ceramic material in the negative electrode piece is 1:3-1:1, optionally 0.45:1-1:1.

As a result, the relative dielectric constants of the ceramic material and the electrolyte are matched to increase the lithium ion desolvation rate and the lithium ion diffusion rate in the SEI film, reduce the risk of lithium dendrites and the degree of lithium precipitation, and reduce the SEI film The thickness reduces the consumption of active lithium ions and electrolyte, thereby reducing the interface resistance of the negative electrode piece and improving the cycle performance and charging rate of the secondary battery.

A fourth aspect of the present application provides a battery module including the secondary battery of the third aspect of the present application.

A fifth aspect of the present application provides a battery pack, including the battery module of the fourth aspect of the present application.

A sixth aspect of the present application provides an electrical device, including at least one selected from the group consisting of the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, and the battery pack of the fifth aspect of the present application. kind.

Description of drawings

FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .

FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.

Figure 7A is a photograph of the surface of the negative electrode piece in Example 1 of the present application.

Figure 7B is a photo of the surface of the negative electrode piece in Comparative Example 1 of the present application.

Figure 8 is an EDS energy spectrum diagram of the negative electrode plate in Example 1 of the present application.

Figure 9 is an XRD pattern of the ceramic material in Example 1 of the present application.

Explanation of reference symbols:

1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly.

Detailed ways

Hereinafter, embodiments specifically disclosing the negative electrode sheet, the method for preparing the negative electrode sheet, the secondary battery, the battery module, the battery pack and the electrical device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed explanations may be omitted. For example, detailed descriptions of well-known matters may be omitted, or descriptions of substantially the same structure may be repeated. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

"Ranges" disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

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 stated otherwise, the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

If there is no special instructions, all steps of the present application can be performed sequentially or randomly, and are preferably performed sequentially. For example, a method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, mentioning that the method may also include step (c) means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.

If there is no special explanation, the words "include" and "include" mentioned in this application represent open expressions, which may also be closed expressions. For example, "comprises" and "comprises" may mean that other components not listed may also be included or included, or that only the listed components may be included or included.

In this application, the term "or" is inclusive unless otherwise specified. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, 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).

If there is no special explanation, in this application, the term "unit cell parameters" means that the shape and size of the unit cell can be expressed by 6 parameters, namely lattice characteristic parameters, referred to as unit cell parameters. It is a set of parameters that determine the shape and size of the unit cell. It includes the three sets of edge lengths of the unit cell (i.e., the axial length of the crystal) a, b, and c and the angles between the three sets of edges (i.e., the axial angles of the crystal) α, β, and γ.

[Secondary battery]

Secondary batteries, also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.

Normally, a secondary battery includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte. During the charging and discharging process of the battery, active ions (such as lithium ions) are inserted and detached back and forth between the positive electrode piece and the negative electrode piece. The isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through. The electrolyte is between the positive electrode piece and the negative electrode piece and mainly plays the role of conducting active ions.

[Negative pole piece]

One embodiment of the present application provides a negative electrode sheet, including a ceramic material, a carbon-based negative active material, and a binder; wherein the relationship between the relative dielectric constant ε of the ceramic material and the unit cell parameters a and c is ε/( The value of c/a) is 78.8-197.9 (such as 89.1, 118.7), and the weight ratio of ceramic material to carbon-based negative active material is 0.0052-0.115, optionally 0.0052-0.057, more optionally 0.0104-0.054 or 0.01 -0.05, such as 0.0103, 0.0105, 0.0326.

In the current charging and discharging process of secondary batteries, the desolvation rate of lithium ions and the diffusion rate of lithium ions in the SEI film are the limiting steps, causing lithium ions to be easily enriched at the interface between the SEI film and the negative electrode sheet. When the lithium ions Lithium dendrites are generated when the enrichment amount breaks through the nucleation barrier; due to the excellent conductivity of lithium metal, lithium ions preferentially gather at the lithium dendrites and are reduced to metallic lithium, which intensifies the formation of lithium dendrites and intensifies the lithium precipitation. degree, resulting in a large consumption of active lithium ions; moreover, 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 the consumption of electrolytes; the large consumption of active lithium and the problem of lithium precipitation cause secondary The cycle performance of the battery is reduced. In addition, the SEI film formed on the surface of the current negative electrode piece is relatively thick, resulting in large electrolyte consumption, long migration path of lithium ions, large interface resistance of the negative electrode piece, and low charging rate of the secondary battery.

Although the mechanism is not yet clear, the applicant unexpectedly discovered that by combining ceramic materials with a specific relationship between relative dielectric constant and unit cell parameters and carbon-based negative active materials in a certain proportion, the ceramic material particles can be evenly dispersed. In the carbon-based negative active material, the desolvation barrier of lithium ions is reduced, the desolvation rate of lithium ions and the diffusion rate of lithium ions in the SEI film are increased, the risk of generating lithium dendrites is reduced, and the precipitation rate is also reduced. The degree of lithium 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 can generate a counter electric field during the charging process, and the electrolyte, ceramic material and carbon-based negative electrode The electron-poor state is formed at the three-phase interface of the active material, which can form a thinner SEI film, further reducing the consumption of active lithium ions and electrolyte, thereby further improving the cycle performance of the secondary battery. The thickness of the SEI film is relatively Thinness shortens the migration path of lithium ions in the SEI film, also reduces the interface resistance of the negative electrode piece, and improves the charging rate of the secondary battery; at the same time, the ceramic material can generate a counter electric field to show negative charge, which helps to disperse and enrich it in the SEI The lithium ions at the interface between the membrane and the negative electrode further reduce the risk of lithium dendrites.

In some embodiments, the relative dielectric constant ε of the ceramic material is 80-200, such as 90, 120. Therefore, the relative dielectric constant of ceramic materials within the above range can further increase the lithium ion desolvation rate and the lithium ion diffusion rate in the SEI film to further reduce the risk of lithium precipitation and reduce the thickness of the SEI film, thereby further Improve the cycle performance and charging rate of secondary batteries.

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

In some embodiments, the ceramic material is one or more selected from the group consisting of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, and lead barium lithium niobate, optionally Barium titanate and/or lead titanate.

In some embodiments, the particle size D _v 50 of the ceramic material is 10-300 nm, optionally 50-200 nm, such as 100 nm.

In some embodiments, the particle size D _v 50 of the carbon-based negative active material is 1-15 μm, optionally 5-10 μm.

In some embodiments, the weight ratio of ceramic material to binder is 0.1-10, optionally 0.5-1, such as 5.

In some embodiments, the binder is selected from the group consisting of polyacrylic acid, styrene-butadiene rubber, polyvinylidene fluoride, polyamideimide, polyvinyl alcohol, polyethyleneimine, polyimide, and poly(tert-butyl acrylate). ester-triethoxyvinylsilane), optionally styrene-butadiene rubber and/or polyvinylidene fluoride.

In some embodiments, the weight average molecular weight of the binder is 500,000-4 million, optionally 1 million-2 million, such as 1.5 million; optionally, the molecular weight distribution index of the binder is 2-10, more preferably Choose 2-4.

In some embodiments, the ceramic material is barium titanate, and barium titanate includes two crystal forms: cubic crystal form and tetragonal crystal form; the tetragonal crystal form is preferred.

In some embodiments, barium titanate has peaks at the following positions in an X-ray powder diffraction pattern expressed in 2θ angles using Cu-Kα radiation: 22±1°, 31±1°, 38±1°, 45 ±1°, 56±1°.

Using the above-mentioned barium titanate as a ceramic material can further increase the lithium ion desolvation rate and the lithium ion diffusion rate in the SEI film to further reduce the risk of lithium precipitation and reduce the thickness of the SEI film, thereby further improving the cycle of the secondary battery. performance and charging rate.

In some embodiments, the carbon-based negative active material is one or more selected from the group consisting of hard carbon, soft carbon, graphite and Ketjen black, optionally hard carbon and/or graphite (such as artificial graphite). The use of the above-mentioned carbon-based negative active materials can ensure that the battery core has a high energy density.

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

As an example, the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

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

In some embodiments, the negative electrode film layer optionally further includes 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.

In some embodiments, the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.

In this application, the relative dielectric constant of ceramic materials refers to the relative dielectric constant at room temperature (25±5°C), which has a well-known meaning in the art and can be tested using instruments and methods known in the art.

In this application, the particle size D _v 50 is determined by a particle size tester.

In this application, the ratio c/a of the unit cell parameters c-axis and a-axis can be calculated based on the XRD pattern analysis of the material using the software that comes with the X-ray diffractometer.

[Method for preparing negative electrode plate]

The method of preparing the negative electrode sheet of the present application includes the following steps:

(1) Provide ceramic materials. The relationship between the relative dielectric constant ε of the ceramic material and the unit cell parameters a and c is ε/(c/a). The value is 78.8-197.9, such as 89.1 and 118.7;

(2) Use the negative electrode slurry including the ceramic material obtained in step (1), the carbon-based negative active material and the binder to prepare the negative electrode piece; wherein the weight ratio of the ceramic material to the carbon-based negative active material is 0.0052-0.115 , optionally 0.0052-0.057, more optionally 0.0104-0.054 or 0.01-0.05, such as 0.0103, 0.0105, 0.0326.

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

Optionally, the speed of the ball mill is 200-300r/min;

Optionally, the ball milling time is 2-4h, such as 3h.

In some embodiments, in step (2), the weight ratio of ceramic material to binder is 0.1-10, optionally 0.5-1, such as 5.

In some embodiments, the negative electrode slurry including the ceramic material obtained in step (1), the carbon-based negative active material and the binder is obtained by the following steps:

The ceramic material, carbon-based negative active material, binder and any other components obtained in step (1) are dispersed in a solvent (such as deionized water) to form a negative electrode slurry.

In some embodiments, using the negative electrode slurry to prepare the negative electrode sheet is achieved in the following manner:

The negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.

In some embodiments, the ceramic material is as described in "[Negative Electrode Plate]".

In some embodiments, the carbon-based negative active material is as described in "[Negative Electrode Sheet]".

In some embodiments, the binder is as described in "[Negative Electrode Plate]".

[Positive pole piece]

The positive electrode sheet usually includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material.

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

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the cathode active material may be a cathode active material known in the art for batteries. As an example, the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO ₂ ), lithium nickel oxides (such as LiNiO ₂ ), lithium manganese oxides (such as LiMnO ₂ , LiMn ₂ O ₄ ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM ₃₃₃ ), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (can also be abbreviated to NCM ₅₂₃ ), LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (can also be abbreviated to NCM ₂₁₁ ), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (can also be abbreviated to NCM ₆₂₂ ), LiNi At least one of _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM ₈₁₁ ), lithium nickel cobalt aluminum oxide (such as LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and its modified compounds. The olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.

In some embodiments, the positive electrode film layer optionally further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.

In some embodiments, the positive electrode film layer optionally further includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

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 (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.

[Isolation film]

In some embodiments, the secondary battery further includes a separator film. There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.

In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.

[electrolytes]

The electrolyte plays a role in conducting ions between the positive and negative electrodes. There is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs. For example, the electrolyte can be liquid, gel, or completely solid.

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

In some embodiments, the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.

In some embodiments, the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

In some embodiments, the electrolyte optionally also includes 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 properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

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

In some embodiments, the ratio of the relative dielectric constant of the electrolyte to the relative dielectric constant of the ceramic material in the negative electrode piece is 1:3-1:1, optionally 0.45:1-1:1.

In this application, the relative dielectric constant of the electrolyte can be measured by a relative dielectric constant tester. For details, refer to GB/T5594.4-1985.

In some embodiments, the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer packaging. The outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.

In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, FIG. 1 shows a square-structured secondary battery 5 as an example.

In some embodiments, referring to FIG. 2 , the outer package may include a housing 51 and a cover 53 . The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity. The positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the containing cavity. The electrolyte soaks into the electrode assembly 52 . The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

In some embodiments, secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

Figure 3 is a battery module 4 as an example. Referring to FIG. 3 , in the battery module 4 , a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other way. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.

Optionally, the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.

In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

Figures 4 and 5 show the battery pack 1 as an example. Referring to FIGS. 4 and 5 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box 2 and a lower box 3 . The upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 . Multiple battery modules 4 can be arranged in the battery box in any manner.

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

As a power-consuming device, secondary batteries, battery modules or battery packs can be selected according to its usage requirements.

Figure 6 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the electrical device, a battery pack or battery module can be used.

[Example]

Hereinafter, examples of the present application will be described. The embodiments described below are illustrative and are only used to explain the present application and are not to be construed as limitations of the present application. If specific techniques or conditions are not specified in the examples, the techniques or conditions described in literature in the field or product instructions will be followed. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.

Example 1

(1) Preparation of ceramic materials:

Take 100g of barium titanate particles (relative dielectric constant ε is 30, particle size D _v 50 is 100nm) and add it to the ball mill tank, and ball mill at 300r/min for 2 hours. The relative dielectric constant ε of the obtained barium titanate particles is 90 , the value of unit cell parameter c/a is 1.010621, the value of the relationship between relative dielectric constant and unit cell parameter ε/(c/a) is 89.05415581, and the particle size D _v 50 is 50 nm.

(2) Preparation of negative electrode plate:

The negative active material artificial graphite (particle size D _v 50 is 10 μm), conductive agent acetylene black, binder styrene-butadiene rubber (SBR) (weight average molecular weight is 1.5 million, molecular weight distribution index is 2), dispersant carboxymethyl Sodium cellulose (CMC-Na) and the barium titanate particles prepared in step (1) were dissolved in deionized water at a mass ratio of 96:1:1:1:1, stirred thoroughly and mixed evenly to prepare a negative electrode slurry; The negative electrode slurry was evenly coated on the negative electrode current collector copper foil with a thickness of 7 μm with an area density of 9.6 mg/cm ² (after drying), and then dried, cold pressed, and cut to obtain negative electrode sheets.

(3) Preparation of positive electrode plate:

Dissolve the positive active material lithium nickel cobalt manganate (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black in the solvent N-format in a mass ratio of 98:1:1. pyrrolidone (NMP), stir and mix thoroughly under vacuum to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector with a thickness of 13 μm with an area density of 13.7 mg/cm ² (after drying) on aluminum foil, and then dried, cold pressed, and cut to obtain the positive electrode piece.

(4)Isolation film:

A commercially available PP-PE copolymer microporous film with a thickness of 20 μm and an average pore diameter of 80 nm (purchased from Zhuogao Electronic Technology Co., Ltd., model 20) was used.

(5) Preparation of electrolyte:

In an argon atmosphere glove box (H ₂ O <0.1ppm, O ₂ <0.1ppm), mix the organic solvent ethylene carbonate (EC)/ethyl methyl carbonate (EMC) evenly according to the volume ratio of 3/7, add 12.5 Dissolve % by weight (based on the weight of ethylene carbonate/ethyl methyl carbonate solvent) LiPF ₆ in the above organic solvent and stir evenly to obtain an electrolyte. In the electrolyte, the concentration of LiPF ₆ is 1 mol/L, and the dielectric constant of the electrolyte is 90.

(6) Preparation of secondary batteries:

Stack and wind the above-mentioned positive electrode sheets, separators, and negative electrode sheets in order to obtain an electrode assembly; put the electrode assembly into an outer package, add the electrolyte prepared above, and go through processes such as packaging, standing, formation, and aging. Finally, a secondary battery is obtained.

(7) Preparation of button batteries:

Stack the above-mentioned positive electrode plates, isolation films, and negative electrode plates in order on the 2032 button cell, add electrolyte dropwise, and complete the packaging at a pressure of 0.35Mpa to obtain it.

Example 2-28 and Comparative Example 1-9

Examples 2-28 and Comparative Examples 1-9 are similar to the secondary battery preparation methods of Example 1, but the parameters are adjusted. The different parameters are detailed in Table 1. The rest are the same as Example 1. Among them, w1 represents the weight percentage of the ceramic material in the negative electrode sheet, w2 represents the weight percentage of the carbon-based negative active material in the negative electrode sheet, m1 represents the weight of the ceramic material in the negative electrode sheet, and m2 represents the weight percentage of the negative electrode active material in the negative electrode sheet. The weight of the carbon-based negative active material, m3, represents the weight of the binder in the negative electrode piece; the weight percentages of the conductive agent and dispersant in the negative electrode slurry are the same.

Performance Testing

(1) Test method for relative dielectric constant ε:

Test method for the relative dielectric constant ε of ceramic materials: After preparing the material to be tested into a circular sample, use an LCR tester to test the capacitance C and according to the formula: relative dielectric constant ε = (C×d)/(ε0 ×A) is calculated; among them, C represents the capacitance, in farads (F); d represents the sample thickness, in cm; A represents the sample area, in cm ² ; ε0 represents the vacuum dielectric constant, ε0= 8.854×10 ^-14 F/cm. The test conditions are 1KHz, 1.0V, 25±5℃. The test standard can be based on GB/T 11297.11-2015. When preparing samples, please refer to Chinese patent application CN114217139A.

Test method for the relative dielectric constant ε of the electrolyte: refer to GB/T5594.4-1985, and use the ZJD-C relative dielectric constant tester of Beijing AVIC Times Instrument Equipment Co., Ltd. to measure it.

The results are shown in Table 1.

(2) Use a particle size tester to measure the particle size D _v 50. The results are shown in Table 1.

(3) Fully charge the secondary batteries of Example 1 and Comparative Example 1 at a rate of 4C, then directly take photos and observe the lithium deposition on the surface of the negative electrode sheet;

It can be seen from Figures 7A-7B that in the fully charged state, the surface of the negative electrode piece of Example 1 has less lithium precipitation, while the surface of the negative electrode piece of Comparative Example 1 has serious lithium precipitation and some parts have purple spots, which illustrates that the negative electrode of the present invention The surface of the chip is not prone to lithium precipitation, and lithium precipitation is effectively suppressed.

(4) Measure the EDS energy spectrum of the negative electrode piece of Example 1;

It can be seen from Figure 8 that the barium titanate in the negative electrode piece of Example 1 is evenly distributed, which is beneficial to the fast charging effect.

(5) Use an X-ray diffractometer to measure the XRD pattern of ceramic materials. Measurement conditions: use Cu-Kα radiation, and the test angle is from 10°-80°. The software that comes with the X-ray diffractometer is used to analyze and calculate the ratio c/a of the unit cell parameters c-axis and a-axis, and further calculate ε/(c/a).

Figure 9 is the XRD spectrum of the ceramic material in Example 1, including peaks at the following positions: 22±1°, 31±1°, 38±1°, 45±1°, 56±1°; the XRD comes with the software Analysis shows that barium titanate contains two crystal forms: cubic crystal form and tetragonal crystal form.

(6) Determination of electric charge capacity:

At 2.5~4.3V, charge the button battery to 4.3V at 0.1C, then charge at a constant voltage at 4.3V until the current is less than or equal to 0.05mA, let it stand for 5 minutes, and then discharge it at 0.1C to 2.0V. At this time The discharge capacity is the initial gram capacity. Divide the initial gram capacity by the weight of the positive active material to get the positive gram capacity.

(7) First measurement of Coulombic efficiency:

In a 25°C, normal pressure environment, discharge the button battery at a constant current rate of 0.1C until the voltage is 0.005V, and then discharge it at a constant current rate of 0.05C until the voltage is 0.005V. Record the discharge specific capacity at this time, which is the first Secondary lithium insertion capacity; then charge at a constant current rate of 0.1C until the voltage is 1.5V, and record the charge specific capacity at this time, which is the first lithium removal capacity. Conduct 50 cycle charge and discharge tests on the button battery according to the above method, and record the lithium removal capacity each time.

First Coulombic efficiency (%) = first lithium removal capacity/first lithium insertion capacity × 100%

(8) Determination of 4C charging resistance:

The dynamic performance of secondary batteries is evaluated by measuring the 4C charging resistance. At 25°C, the secondary batteries prepared in the Examples and Comparative Examples were discharged to 50% capacity for the first time, left to stand for 30 minutes, and the voltage value V1 and the corresponding current A0 at a 4C rate were recorded (current A0 = rate × A0 rated capacity , A0 rated capacity is the capacity obtained by assembling the pole pieces into a full battery) Charge for 10 seconds, record the voltage value V2 corresponding to the end of charging, calculate the charging resistance according to the following formula, and then normalize it using Comparative Example 1 as 100 to obtain the result.

R＝(V2-V1)/A0

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

The capacity retention performance of 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, discharged at a 1C rate, and subjected to continuous cycle testing in the 3%-97% SOC range until the capacity of the secondary battery was less than 80% of the initial capacity. %, record the number of cycles.

(10)Measurement of fast charging time:

Charge the secondary battery at a 5C rate for the first time from 10% SOC to 80% SOC, and record the charging time, which is the fast charging time.

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

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

It can be seen from Table 1-2:

Compared with the secondary batteries of Comparative Examples 1-9, the secondary batteries made of the negative electrode plates of the present application have longer fast-charging cycle life, better cycle performance, and faster charging rates.

Comparing Example 1 with Examples 19-20, it can be seen that the fast charge cycle life of the secondary battery made by using the negative electrode sheet with a weight ratio of ceramic material and binder of 0.5-1 is further extended, and the cycle performance is further improved. Improved, the charging rate is further increased.

Comparing Example 1 with Examples 7 and 21, it can be seen that the fast charge cycle life of the secondary battery made by the negative electrode plate of the ceramic material with a particle size D _v 50 of 50-200 nm is further extended and the cycle performance is further improved. .

Comparing Example 1 with Examples 11 and 22, it can be seen that the fast charging cycle life of the secondary battery made by using the negative electrode sheet with a particle size D _v 50 of the carbon-based negative active material of 5-10 μm is further extended, and the cycle life is further extended. Performance is further improved and charging rates are further increased.

Comparing Example 1 with Examples 23-24, it can be seen that the fast charging cycle life of the secondary battery made by the negative electrode sheet of the binder with a weight average molecular weight of 1 million to 2 million is further extended, and the cycle performance is further improved. improve.

Comparing Example 1 with Example 25, it can be seen that the fast charging cycle life of the secondary battery produced by the negative electrode sheet of the binder with a molecular weight distribution index of 2-4 is further extended, the cycle performance is further improved, and the charging rate is Further improve.

Comparing Example 1 with Example 27, it can be seen that the fast charge cycle life of the secondary battery made by using the negative electrode plate with a weight percentage of ceramic material of 0.5%-5% is further extended and the cycle performance is further improved. The charging rate is further improved.

Comparing Example 1 with Example 28, it can be seen that the fast charge cycle life of the secondary battery produced by the present application using the ratio of the relative dielectric constant of the electrolyte to the relative dielectric constant of the ceramic material is 0.45:1-1:1. Extended, the cycle performance is further improved and the charging rate is further increased.

It should be noted that the present application is not limited to the above-described embodiment. The above-mentioned embodiments are only examples. Within the scope of the technical solution of the present application, embodiments that have substantially the same structure as the technical idea and exert the same functions and effects are included in the technical scope of the present application. In addition, within the scope that does not deviate from the gist of the present application, various modifications to the embodiments that can be thought of by those skilled in the art, and other forms constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application. .

Claims

A negative electrode piece, including a ceramic material, a carbon-based negative active material and a binder; wherein the relationship between the relative dielectric constant ε of the ceramic material and the unit cell parameters a and c is ε/(c/a) The value is 78.8-197.9, and the weight ratio of the ceramic material to the carbon-based negative active material is 0.0052-0.115, optionally 0.0052-0.057.
The negative electrode piece according to claim 1, wherein the relative dielectric constant ε of the ceramic material is 80-200.
The negative electrode piece according to claim 1 or 2, wherein the weight percentage of the ceramic material in the negative electrode piece is 0.5%-10%, optionally 0.5%-5%.
The negative electrode plate according to any one of claims 1 to 3, wherein the ceramic material is selected from the group consisting of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate and niobate. One or more of lead, barium, and lithium.
The negative electrode piece according to any one of claims 1 to 4, wherein the particle size D v 50 of the ceramic material is 10-300 nm, optionally 50-200 nm.
The negative electrode sheet according to any one of claims 1 to 5, wherein the particle size D v 50 of the carbon-based negative active material is 1-15 μm, optionally 5-10 μm.
The negative electrode piece according to any one of claims 1 to 6, wherein the weight ratio of the ceramic material and the binder is 0.1-10, optionally 0.5-1.
The negative electrode sheet according to any one of claims 1 to 7, wherein the binder is selected from the group consisting of polyacrylic acid, styrene-butadiene rubber, polyvinylidene fluoride, polyamide-imide, polyvinyl alcohol, One or more of polyethyleneimine, polyimide, and poly(tert-butyl acrylate-triethoxyvinylsilane).
The negative electrode piece according to claim 8, wherein the weight average molecular weight of the binder is 500,000-4,000,000, optionally 1,000,000-2,000,000;

Optionally, the molecular weight distribution index of the binder is 2-10, more optionally 2-4.
The negative electrode plate according to any one of claims 1 to 8, wherein the ceramic material is barium titanate, and the barium titanate includes two crystal forms: cubic crystal form and tetragonal crystal form.
The negative electrode sheet according to claim 10, wherein the barium titanate has peaks at the following positions in an X-ray powder diffraction pattern expressed at an angle of 2θ using Cu-Kα radiation: 22±1°, 31± 1°, 38±1°, 45±1°, 56±1°, 66±1°.
The negative electrode sheet according to any one of claims 1 to 11, wherein the carbon-based negative active material is one or more selected from the group consisting of hard carbon, soft carbon, graphite and Ketjen black.
A method of preparing a negative electrode piece, including the following steps:

(1) Provide a ceramic material, the relationship between the relative dielectric constant ε of the ceramic material and the unit cell parameters a and c, ε/(c/a), has a value of 78.8-197.9;

(2) Use the negative electrode slurry containing the ceramic material, the carbon-based negative active material and the binder obtained in step (1) to prepare the negative electrode piece; wherein, the relationship between the ceramic material and the carbon-based negative active material The weight ratio is 0.0052-0.115, and the optional value is 0.0052-0.057.
The method according to claim 13, wherein in the step (1), the ceramic material is obtained by ball milling;

Optionally, the rotation speed of the ball mill is 200-300r/min;

Optionally, the ball milling time is 2-4 hours.
The method according to claim 13 or 14, wherein in the step (2), the weight ratio of the ceramic material and the binder is 0.1-10, optionally 0.5-1.
A secondary battery including the negative electrode sheet according to any one of claims 1 to 12 or the negative electrode sheet prepared by the method according to any one of claims 13 to 15, and an electrolyte.
The secondary battery according to claim 16, wherein the ratio of the relative dielectric constant of the electrolyte to the relative dielectric constant of the ceramic material in the negative electrode piece is 1:3-1:1, which can be Choose 0.45:1-1:1.
A battery module including the secondary battery according to claim 16 or 17.
A battery pack including the battery module according to claim 18.
An electric device including at least one selected from the group consisting of the secondary battery according to claim 16 or 17, the battery module according to claim 18, and the battery pack according to claim 19.