Lithium metal battery cell, negative electrode sheet, battery device, and electric device

Abstract

The application provides a lithium metal battery cell, a negative electrode sheet for the lithium metal battery cell, a battery device and a power utilization device. The lithium metal battery cell comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector, a first negative electrode interface layer located on at least one side of the negative electrode current collector, and a second negative electrode interface layer located on a side of the first negative electrode interface layer away from the negative electrode current collector, the first negative electrode interface layer comprises a first negative electrode interface material, and the second negative electrode interface layer comprises a second negative electrode interface material; the first negative electrode interface material comprises a first carbon-based material, and the elastic modulus of the first negative electrode interface material is greater than or equal to 100 GPa. The lithium metal battery cell effectively inhibits the expansion of the negative electrode sheet and the damage of lithium intercalation to the structure of the negative electrode sheet, and improves the cycle performance of the battery cell.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a lithium metal battery cell, a negative electrode for a lithium metal battery cell, a battery device, and an electrical device. Background Technology

[0002] In recent years, with the increasingly wide range of applications, batteries 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 advancements in battery technology, higher requirements have been placed on their cycle performance and other characteristics. Summary of the Invention

[0003] The purpose of this application is to provide a lithium metal battery cell, a negative electrode for the lithium metal battery cell, a battery device, and an electrical device. The lithium metal battery cell of this application effectively suppresses the expansion of the negative electrode caused by lithium deposition, effectively suppresses the damage to the negative electrode structure caused by lithium intercalation, and improves the cycle performance of the battery cell.

[0004] To achieve the above objectives, a first aspect of this application provides a lithium metal battery cell, including a negative electrode sheet. The negative electrode sheet includes a negative current collector, a first negative electrode interface layer located on at least one side of the negative current collector, and a second negative electrode interface layer located on the side of the first negative electrode interface layer away from the negative current collector. The first negative electrode interface layer includes a first negative electrode interface material, and the second negative electrode interface layer includes a second negative electrode interface material. The first negative electrode interface material includes a first carbon-based material, and the elastic modulus of the first negative electrode interface material is ≥100 GPa.

[0005] Therefore, by setting a first negative electrode interface layer comprising a first carbon-based material between the second negative electrode interface layer and the negative electrode current collector, and limiting the elastic modulus of the first negative electrode interface material to be greater than or equal to 100 GPa, the first negative electrode interface layer is less likely to expand with lithium when it comes into contact with deposited lithium, effectively suppressing the expansion of the negative electrode sheet caused by lithium deposition, and the structural integrity of the first negative electrode interface layer is less likely to be damaged when lithium is embedded and deposited in the first negative electrode interface layer, thereby improving the cycle performance of the battery cell.

[0006] In any embodiment, the elastic modulus of the first negative electrode interface material is 100GPa-800GPa or 100GPa-600GPa.

[0007] Therefore, the aforementioned elastic modulus range of the first negative electrode interface material, on the one hand, makes it less likely for the first negative electrode interface layer to expand with lithium when in contact with deposited lithium, effectively suppressing the expansion of the negative electrode sheet and the battery cell. On the other hand, an increase in the elastic modulus of the first negative electrode interface material may lead to a decrease in the porosity of the first negative electrode interface layer, thereby affecting the penetration of lithium ions through the first negative electrode interface layer, causing the expansion of the negative electrode sheet and the battery cell. Furthermore, an increase in the elastic modulus of the first negative electrode interface material leads to stress concentration at the contact surface between the first negative electrode interface layer and the deposited lithium, which may lead to the peeling of the first negative electrode interface layer or the separation of the first negative electrode interface layer from the deposited lithium, resulting in an unstable contact interface and affecting the cycle performance of the battery cell. The aforementioned range reduces the adverse effects of an increase in the elastic modulus of the first negative electrode interface material on the battery cell.

[0008] In any embodiment, the tensile strength of the first negative electrode interface material is 0.6 GPa-130 GPa or 1 GPa-100 GPa.

[0009] Therefore, the tensile strength range of the aforementioned first negative electrode interface material has two advantages. First, the first negative electrode interface layer is less likely to expand with lithium when in contact with deposited lithium, effectively suppressing the expansion of the negative electrode sheet and the battery cell. Second, an increase in the tensile strength of the first negative electrode interface material may lead to a decrease in the porosity of the first negative electrode interface layer, making it difficult for lithium ions to pass through the first negative electrode interface layer for conduction. This can cause the expansion of the negative electrode sheet and the battery cell, a decrease in the cycle performance of the battery cell, and may also lead to stress concentration in the contact area between the first negative electrode interface layer and the deposited lithium, resulting in the peeling of the first negative electrode interface layer, which also affects the cycle performance of the battery cell. The aforementioned range reduces the adverse effects of increasing the tensile strength of the first negative electrode interface material on the cycle performance of the battery cell.

[0010] In any embodiment, the lithium-ion diffusion coefficient of the second negative electrode interface material is ≥10. -11 cm 2 / s or ≥10 -10 cm 2 / s.

[0011] This improves the lithium conductivity of the second negative electrode interface layer, suppresses lithium deposition on or inside the second negative electrode interface layer, reduces the formation of lithium dendrites, inhibits side reactions between lithium and electrolyte, reduces the damage to the structural stability caused by lithium deposition in the second negative electrode interface layer, promotes lithium deposition between the first negative electrode interface layer and the negative electrode current collector or deposition in the first negative electrode interface layer, and inhibits negative electrode expansion, thereby improving the cycle performance of the battery cell.

[0012] In any embodiment, the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer is 1:100-5:1 or 1:10-5:5.

[0013] Therefore, on the one hand, setting the lower limit of the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer inhibits the contact between the second negative electrode interface layer and deposited lithium and / or the precipitation of lithium within the second negative electrode interface layer, reducing the expansion of the negative electrode sheet and improving the stability of the second negative electrode interface layer structure. On the other hand, setting the upper limit of the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer inhibits the direct contact between the electrolyte and the lithium deposited on the surface of the first negative electrode interface layer, reducing the dead lithium generated therefrom, thereby improving the cycle performance of the battery cell.

[0014] In any embodiment, the thickness of the first negative electrode interface layer is 0.1 μm-5 μm or 1 μm-5 μm. Therefore, on the one hand, setting the lower limit of the thickness of the first negative electrode interface layer helps to suppress the contact between the second negative electrode interface layer and deposited lithium and / or the precipitation of lithium within the second negative electrode interface layer, thereby reducing negative electrode expansion, improving the structural stability of the second negative electrode interface layer, and improving the cycle performance of the battery cell. On the other hand, setting the upper limit of the thickness of the first negative electrode interface layer helps to reduce the impact of increased thickness on lithium-ion conduction.

[0015] In any embodiment, the thickness of the second negative electrode interface layer is 0.4 μm-100 μm or 5 μm-100 μm. Therefore, on the one hand, setting the lower limit of the second negative electrode interface layer thickness helps to suppress the direct contact between the electrolyte and lithium deposited on the surface of the first negative electrode interface layer, thus reducing the generation of dead lithium and improving the cycle performance of the battery cell. On the other hand, setting the upper limit of the second negative electrode interface layer thickness helps to reduce the impact of increased thickness on lithium-ion conduction.

[0016] In any embodiment, the porosity of the first negative electrode interface layer is 30%-85% or 40%-80%.

[0017] Therefore, on the one hand, setting the upper limit of the porosity of the first negative electrode interface layer helps to enhance the strength of the first negative electrode interface layer, so that the first negative electrode interface layer can resist the expansion caused by lithium when it comes into contact with deposited lithium, effectively suppressing the expansion of the negative electrode sheet and the battery cell caused by lithium, and making it less likely for the embedded lithium to damage the integrity of the first negative electrode interface layer, thereby improving the cycle performance of the battery cell. On the other hand, setting the lower limit of the porosity of the first negative electrode interface layer reduces the impact of the reduction in porosity on lithium-ion conduction, thereby suppressing the expansion of the negative electrode sheet and the battery cell caused by it, and improving the cycle performance.

[0018] In any embodiment, the first carbon-based material includes a one-dimensional carbon-based material, wherein the aspect ratio of the one-dimensional carbon-based material is 800-12000 or 1000-10000.

[0019] Therefore, on the one hand, setting the lower limit of the aspect ratio of one-dimensional carbon-based materials is beneficial to improving the strength of the first carbon-based material, so that the first negative electrode interface layer can effectively resist the expansion caused by lithium when it comes into contact with deposited lithium, thereby suppressing the expansion of the negative electrode sheet caused by lithium, and making the structure of the first negative electrode interface layer less likely to be destroyed by the embedded lithium, thereby improving the cycle performance of the battery cell. On the other hand, setting the upper limit of the aspect ratio of one-dimensional carbon-based materials can reduce the difficulty of the preparation process.

[0020] In any embodiment, the compaction density of the second negative electrode interface layer is 0.5-1.5 g / cm³. 3 .

[0021] Therefore, on the one hand, setting the lower limit of the compaction density range of the second negative electrode interface layer is beneficial to separating the electrolyte from the first negative electrode interface layer, so as to suppress the side reaction between lithium deposited on the surface of the first negative electrode interface layer and the electrolyte and reduce the generation of dead lithium; on the other hand, setting the upper limit of the compaction density range of the second negative electrode interface layer reduces the adverse effect of increased compaction density on lithium-ion conduction, improves the lithium conduction capability of the second negative electrode interface layer, and promotes the deposition of lithium between the first negative electrode interface layer and the negative electrode current collector or the precipitation within the first negative electrode interface layer, thereby improving the cycle performance of the battery cell.

[0022] In any embodiment, the second negative electrode interface material includes a second carbon-based material, the second carbon-based material includes particulate carbon-based material, and the average particle size of the second negative electrode interface material is 10 nm-5 μm.

[0023] Therefore, on the one hand, setting the upper limit of the average particle size of the second negative electrode interface material helps to reduce the contact between the electrolyte and the first negative electrode interface layer, so as to suppress the side reaction between the lithium deposited on the surface of the first negative electrode interface layer and the electrolyte, reduce the generation of dead lithium, and improve the cycle performance of the battery cell; on the other hand, setting the lower limit of the average particle size of the second negative electrode interface material reduces the impact of the reduction of the average particle size of the second negative electrode interface material on lithium-ion conduction.

[0024] In any embodiment, the first carbon-based material includes one or more of one-dimensional carbon-based materials and two-dimensional carbon-based materials. Optionally, the first carbon-based material includes one or more of hard carbon fibers, carbon nanotube bundles, and graphene.

[0025] In any embodiment, the second negative electrode interface material includes a second carbon-based material, which includes one or more of one-dimensional carbon-based materials and particulate carbon-based materials. Optionally, the second carbon-based material includes one or more of amorphous carbon, graphite, hard carbon, conductive carbon black, and carbon nanotubes.

[0026] In any embodiment, the cohesive force of the negative electrode sheet is 80N / m-320N / m or 100N / m-300N / m.

[0027] Therefore, the aforementioned cohesive range of the negative electrode sheet is beneficial in two ways: firstly, it helps to suppress the expansion of the negative electrode sheet, thereby suppressing the expansion of the battery cell; secondly, it can reduce the adverse effects of increased cohesive force on lithium-ion transport.

[0028] In any embodiment, when the lithium metal battery cell is charged from 0% SOC to 100% SOC, the thickness increase rate of the negative electrode sheet is ≤130%, ≤100%, or ≤10%. This helps to suppress the expansion of the negative electrode sheet during the charging process of the battery cell, thereby improving the cycle performance of the battery cell.

[0029] A second aspect of this application provides a negative electrode sheet for a lithium metal battery cell, comprising a negative current collector, a first negative electrode interface layer located on at least one side of the negative current collector, and a second negative electrode interface layer located on the side of the first negative electrode interface layer away from the negative current collector. The first negative electrode interface layer comprises a first negative electrode interface material, and the second negative electrode interface layer comprises a second negative electrode interface material. The first negative electrode interface material comprises a first carbon-based material, and the elastic modulus of the first negative electrode interface material is ≥100 GPa.

[0030] Therefore, by setting a first negative electrode interface layer comprising a first carbon-based material between the second negative electrode interface layer and the negative electrode current collector, and limiting the elastic modulus of the first negative electrode interface material to be greater than or equal to 100 GPa, the first negative electrode interface layer is less likely to expand with lithium when it comes into contact with deposited lithium, effectively suppressing the expansion of the negative electrode sheet caused by lithium deposition, and the structural integrity of the first negative electrode interface layer is less likely to be damaged when lithium is embedded and deposited in the first negative electrode interface layer.

[0031] In any embodiment, the elastic modulus of the first negative electrode interface material is 100GPa-800GPa or 100GPa-600GPa.

[0032] In any embodiment, the tensile strength of the first negative electrode interface material is 0.6 GPa-130 GPa or 1 GPa-100 GPa.

[0033] In any embodiment, the lithium-ion diffusion coefficient of the second negative electrode interface material is ≥10. -11 cm 2 / s or ≥10 -10 cm 2 / s.

[0034] In any embodiment, the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer is 1:100-5:1 or 1:10-5:5.

[0035] In any embodiment, the thickness of the first negative electrode interface layer is 0.1 μm-5 μm or 1 μm-5 μm.

[0036] In any embodiment, the thickness of the second negative electrode interface layer is 0.4μm-100μm or 5μm-100μm.

[0037] In any embodiment, the porosity of the first negative electrode interface layer is 30%-85% or 40%-80%.

[0038] In any embodiment, the first carbon-based material includes a one-dimensional carbon-based material, wherein the aspect ratio of the one-dimensional carbon-based material is 800-12000 or 1000-10000.

[0039] In any embodiment, the compaction density of the second negative electrode interface layer is 0.5-1.5 g / cm³. 3 .

[0040] In any embodiment, the second negative electrode interface material includes a second carbon-based material, the second carbon-based material includes particulate carbon-based material, and the average particle size of the second negative electrode interface material is 10 nm-5 μm.

[0041] In any embodiment, the first carbon-based material includes one or more of one-dimensional carbon-based materials and two-dimensional carbon-based materials. Optionally, the first carbon-based material includes one or more of hard carbon fibers, carbon nanotube bundles, and graphene.

[0042] In any embodiment, the second negative electrode interface material includes a second carbon-based material, which includes one or more of one-dimensional carbon-based materials and particulate carbon-based materials. Optionally, the second carbon-based material includes one or more of amorphous carbon, graphite, hard carbon, conductive carbon black, and carbon nanotubes.

[0043] In any embodiment, the cohesive force of the negative electrode sheet is 80N / m-320N / m or 100N / m-300N / m.

[0044] A third aspect of this application provides a battery device, including a lithium metal battery cell according to the first aspect of this application or a negative electrode sheet according to the second aspect of this application.

[0045] The fourth aspect of this application provides an electrical device, including a lithium metal battery cell of the first aspect of this application or a battery device of the third aspect of this application. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0048] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0049] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0050] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0051] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0052] 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.

[0053] Figure 7 This is a SEM image of the cross-section of the negative electrode sheet in the thickness direction after 30 cycles of the battery cell in Embodiment 1 of this application.

[0054] Figure 8a This is a SEM image of the negative electrode current collector facing the separator after 30 cycles of the single cell in Comparative Example 1.

[0055] Figure 8b This is a SEM image of the separator facing the negative electrode side of a single battery cell in Comparative Example 1 after 30 cycles.

[0056] The accompanying drawings are not drawn to scale.

[0057] Explanation of reference numerals in the attached figures:

[0058] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0059] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0060] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the lithium metal battery cell, battery module, battery pack, and power supply 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.

[0061] 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.

[0062] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0063] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0064] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates 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.

[0065] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0066] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": 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).

[0067] [Rechargeable Battery]

[0068] 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.

[0069] 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.

[0070] One embodiment of this application provides a lithium metal battery cell, including a negative electrode sheet. The negative electrode sheet includes a negative current collector, a first negative electrode interface layer located on at least one side of the negative current collector, and a second negative electrode interface layer located on the side of the first negative electrode interface layer away from the negative current collector. The first negative electrode interface layer includes a first negative electrode interface material, and the second negative electrode interface layer includes a second negative electrode interface material. The first negative electrode interface material includes a first carbon-based material, and the elastic modulus of the first negative electrode interface material is ≥100 GPa.

[0071] In existing lithium metal battery cells, the negative electrode sheet has a negative electrode interface layer on at least one side of the negative electrode current collector. During battery charging, lithium is deposited between the negative electrode current collector and the negative electrode interface layer or precipitated within the negative electrode interface layer. However, because the lithium deposition is not dense and is prone to volume expansion, the negative electrode interface layer in contact with the deposited lithium cannot resist the expansion caused by lithium. This leads to an increase in the expansion degree of the negative electrode sheet and the battery cell. Furthermore, the expansion of lithium precipitated within the negative electrode interface layer can easily lead to structural differentiation and failure of the negative electrode interface layer, resulting in a decrease in the cycle performance of the battery cell.

[0072] To solve the above-mentioned technical problems, the applicant unexpectedly discovered that by setting a first negative electrode interface layer comprising a first carbon-based material between the second negative electrode interface layer and the negative electrode current collector, and limiting the elastic modulus of the first negative electrode interface material to be greater than or equal to 100 GPa, the first negative electrode interface layer is less likely to expand with the deposited lithium when in contact with the lithium, effectively suppressing the expansion of the negative electrode sheet caused by the deposited lithium, suppressing the expansion of the battery cell, and furthermore, when lithium is embedded and deposited in the first negative electrode interface layer, it is not easy to damage the structural integrity of the first negative electrode interface layer, thereby improving the cycle performance of the battery cell.

[0073] In this application, the elastic modulus refers to the ratio of stress to strain in a material during the elastic deformation stage, which characterizes the material's ability to resist elastic deformation.

[0074] In some embodiments, the elastic modulus of the first negative electrode interface material is 100GPa-800GPa or 100GPa-600GPa, for example, 100GPa, 150GPa, 200GPa, 300GPa, 390GPa, 500GPa, 600GPa or any range of the above values.

[0075] Therefore, the aforementioned elastic modulus range of the first negative electrode interface material, on the one hand, makes it less likely for the first negative electrode interface layer to expand with lithium when in contact with deposited lithium, effectively suppressing the expansion of the negative electrode sheet and the battery cell. On the other hand, an increase in the elastic modulus of the first negative electrode interface material may lead to a decrease in the porosity of the first negative electrode interface layer, thereby affecting the penetration of lithium ions through the first negative electrode interface layer, causing the expansion of the negative electrode sheet and the battery cell. Furthermore, an increase in the elastic modulus of the first negative electrode interface material leads to stress concentration at the contact surface between the first negative electrode interface layer and the deposited lithium, which may lead to the peeling of the first negative electrode interface layer or the separation of the first negative electrode interface layer from the deposited lithium, resulting in an unstable contact interface and affecting the cycle performance of the battery cell. The aforementioned range reduces the adverse effects of an increase in the elastic modulus of the first negative electrode interface material on the battery cell.

[0076] In this application, the method for testing the elastic modulus of the first negative electrode interface material is a conventional method known in the art. As an example, the testing method may be as follows: The negative electrode sheet is removed, cleaned, and dried. The second negative electrode interface material is scraped off, and then the first negative electrode interface material is scraped off. The first negative electrode interface material is dispersed in a solvent to form a liquid, which is then coated onto a clean substrate and dried in a vacuum environment to form a film layer on the substrate. The film layer is peeled off from the substrate and cut into strip samples (e.g., 15 mm × 3 cm). A tensile testing machine is used for testing. First, a load of 1%-5% is applied, ensuring there is no gap or wobbling between the sample and the testing machine. Then, a load is applied at a certain strain rate (e.g., 0.15 mm / s) until the sample breaks. The instrument calculates the elastic modulus based on the stress-strain curve. All the above cleaning and dispersion processes use solvents that do not damage the negative electrode interface material.

[0077] In some embodiments, the tensile strength of the first negative electrode interface material is 0.6GPa-130GPa or 1GPa-100GPa, for example, 1GPa, 10GPa, 30GPa, 40GPa, 50GPa, 80GPa, 90GPa, 100GPa or any range of the above values.

[0078] Therefore, the tensile strength range of the aforementioned first negative electrode interface material has two advantages. First, the first negative electrode interface layer is less likely to expand with lithium when in contact with deposited lithium, effectively suppressing the expansion of the negative electrode sheet and the battery cell. Second, an increase in the tensile strength of the first negative electrode interface material may lead to a decrease in the porosity of the first negative electrode interface layer, making it difficult for lithium ions to pass through the first negative electrode interface layer for conduction. This can cause the expansion of the negative electrode sheet and the battery cell, a decrease in the cycle performance of the battery cell, and may also lead to stress concentration in the contact area between the first negative electrode interface layer and the deposited lithium, resulting in the peeling of the first negative electrode interface layer, which also affects the cycle performance of the battery cell. The aforementioned range reduces the adverse effects of increasing the tensile strength of the first negative electrode interface material on the cycle performance of the battery cell.

[0079] In this application, tensile strength is the maximum stress that a material can withstand during the stretching process, that is, the maximum stress before fracture, which characterizes the material's ability to resist fracture.

[0080] In this application, the tensile strength testing method for the first negative electrode interface material is a conventional method known in the art. As an example, the testing method may be as follows: The negative electrode sheet is removed, cleaned, and dried. The second negative electrode interface material is scraped off, and then the first negative electrode interface material is scraped off. The first negative electrode interface material is dispersed in a solvent to form a liquid, which is then coated onto a clean substrate and dried in a vacuum environment to form a film layer on the substrate. The film layer is peeled off from the substrate and cut into strip samples (e.g., 15mm × 3cm). A tensile testing machine is used for testing. First, a load of 1%-5% is applied, ensuring there is no gap or wobbling between the sample and the testing machine. Then, a load is applied at a certain strain rate (e.g., 0.15mm / s) until the sample breaks. The instrument automatically records the tensile strength. All the above cleaning and dispersion processes are performed using solvents that do not damage the negative electrode interface material.

[0081] In some embodiments, the lithium-ion diffusion coefficient of the second negative electrode interface material is ≥10. -11 cm 2 / s or ≥10 -10 cm 2 / s.

[0082] This improves the lithium conductivity of the second negative electrode interface layer, suppresses lithium deposition on or inside the second negative electrode interface layer, reduces the formation of lithium dendrites, inhibits side reactions between lithium and electrolyte, reduces the damage to the structural stability caused by lithium deposition in the second negative electrode interface layer, promotes lithium deposition between the first negative electrode interface layer and the negative electrode current collector or deposition in the first negative electrode interface layer, and inhibits negative electrode expansion, thereby improving the cycle performance of the battery cell.

[0083] In some embodiments, the lithium-ion diffusion coefficient of the second negative electrode interface material is less than 10. -4 cm 2 / s, optionally up to 10 -5 cm 2 On the order of / s, or 10 -10 cm 2 / s-10 -5 cm 2 / s, or 10 -10 cm 2 / s-10 -6 cm 2 / s, or 10 -10 cm 2 / s-10 -7 cm 2 / s, or 10 -10 cm 2 / s-10 -8 cm 2 / s, or 10 -10 cm2 / s-10 -9 cm 2 / s or any range of the above values.

[0084] In this application, the method for testing the lithium-ion diffusion coefficient of the second negative electrode interface material is a conventional method known in the art. As an example, the test method may be as follows: remove the negative electrode sheet, clean and dry it, scrape off the second negative electrode interface material, disperse the second negative electrode interface material in a solvent, coat it onto an aluminum foil and dry it to form a positive electrode sheet, use a lithium sheet as the negative electrode sheet, and assemble a coin cell using a separator (e.g., a 12 μm thick polyethylene film) and an electrolyte (e.g., dimethyl ether containing 1 M lithium hexafluorophosphate). Perform a constant current pulse discharge (e.g., a discharge rate of 0.5 mA / cm) on the coin cell at room temperature. 2 Discharge time is 30s. The current is then cut off, and the voltage change ΔEt(V) during this period is recorded. After a period of rest (e.g., 2 hours), the voltage recovery value ΔEs(V) over time is recorded. This pulse-relaxation process is repeated until the battery voltage ≤ 0V. For each relaxation process, ΔEs(V)-t... 1 / 2 (s 1 / 2 The curve is linearly fitted within a linear region to obtain the slope k. This slope k is then substituted into the following formula to calculate the lithium-ion diffusion coefficient of a single pulse-relaxation test, where L represents the thickness (cm) of the second negative electrode interface material in the positive electrode sheet. The average value of all lithium-ion diffusion coefficients measured by pulse-relaxation tests is taken as the lithium-ion diffusion coefficient of the second negative electrode interface material.

[0085]

[0086] In some embodiments, the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer is 1:100-5:1 or 1:10-5:5, for example, 1:100, 1:80, 1:60, 1:40, 1:20, 1:10, 1:5, 2:5, 3:5, 5:5, 5:2, 5:1 or any range of the above values.

[0087] Therefore, on the one hand, setting the lower limit of the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer inhibits the contact between the second negative electrode interface layer and deposited lithium and / or the precipitation of lithium within the second negative electrode interface layer, reducing the expansion of the negative electrode sheet and improving the stability of the second negative electrode interface layer structure. On the other hand, setting the upper limit of the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer inhibits the direct contact between the electrolyte and the lithium deposited on the surface of the first negative electrode interface layer, reducing the dead lithium generated therefrom, thereby improving the cycle performance of the battery cell.

[0088] In some embodiments, the thickness of the first negative electrode interface layer is 0.1 μm-5 μm or 1 μm-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any range of the above values. Therefore, on the one hand, setting the lower limit of the thickness of the first negative electrode interface layer helps to suppress the contact between the second negative electrode interface layer and deposited lithium and / or the precipitation of lithium within the second negative electrode interface layer, thereby reducing negative electrode expansion, improving the structural stability of the second negative electrode interface layer, and improving the cycle performance of the battery cell. On the other hand, setting the upper limit of the thickness of the first negative electrode interface layer helps to reduce the impact of increased thickness on lithium-ion conduction.

[0089] In some embodiments, the thickness of the second negative electrode interface layer is 0.4 μm-100 μm or 5 μm-100 μm, for example, 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 100 μm or any range of the above values. Therefore, on the one hand, setting the lower limit of the thickness of the second negative electrode interface layer helps to suppress the direct contact between the electrolyte and lithium deposited on the surface of the first negative electrode interface layer, thus reducing the generation of dead lithium and improving the cycle performance of the battery cell. On the other hand, setting the upper limit of the thickness of the second negative electrode interface layer helps to reduce the impact of increased thickness on lithium-ion conduction.

[0090] In this application, the testing methods for the thicknesses of the first negative electrode interface layer and the second negative electrode interface layer are conventional testing methods known in the art. As an example, the testing method may be as follows: remove the negative electrode sheet, clean and dry it, cut the negative electrode sheet along the arrangement direction of the negative electrode current collector, the first negative electrode interface layer, and the second negative electrode interface layer, and use a scanning electron microscope (SEM) to measure the thicknesses of the first and second negative electrode interface layers on the cross-section and calculate their ratio. The negative electrode sheet can be cut and measured multiple times to obtain accurate thickness values.

[0091] In some embodiments, the porosity of the first negative electrode interface layer is 30%-85% or 40%-80%, for example, 40%, 50%, 60%, 70%, 75%, 80% or any of the above values.

[0092] Therefore, on the one hand, setting the upper limit of the porosity of the first negative electrode interface layer helps to enhance the strength of the first negative electrode interface layer, so that the first negative electrode interface layer can resist the expansion caused by lithium when it comes into contact with deposited lithium, effectively suppressing the expansion of the negative electrode sheet and the battery cell caused by lithium, and making it less likely for the embedded lithium to damage the integrity of the first negative electrode interface layer, thereby improving the cycle performance of the battery cell. On the other hand, setting the lower limit of the porosity of the first negative electrode interface layer reduces the impact of the reduction in porosity on lithium-ion conduction, thereby suppressing the expansion of the negative electrode sheet and the battery cell caused by it, and improving the cycle performance.

[0093] In this application, the method for testing the porosity of the first negative electrode interface layer is a conventional method known in the art. As an example, the testing method may be: remove the negative electrode sheet, scrape off the second negative electrode interface layer, clean and dry it, and cut a certain area (e.g., 1 cm²). 2 A sample was prepared, and the thickness of the first negative electrode interface layer was measured to calculate the volume Vt of the first negative electrode interface layer. The sample was placed in the sample chamber of a mercury porosimeter and sealed. The sample chamber was evacuated using a vacuum system to remove air. Mercury was injected into the sample chamber under low pressure to wet the sample surface. Then, the pressure was gradually increased, and the volume of mercury intrusion at different pressures was recorded. The volumes of mercury intrusion at different pressures were summed to obtain the total pore volume Vp. A negative electrode current collector of the same area was prepared and placed in the sample chamber of the mercury porosimeter for the same experiment as above. The pore volume Vp' of the negative electrode current collector was measured. The total pore volume Vp was subtracted from the pore volume Vp' of the negative electrode current collector, and then divided by the volume Vt of the first negative electrode interface layer to obtain the porosity of the first negative electrode interface layer.

[0094] In some embodiments, the first carbon-based material includes a one-dimensional carbon-based material with an aspect ratio of 800-12000 or 1000-10000, such as 1000, 2000, 4000, 5000, 6000, 8000, 9000, 10000, 11000 or any range of the above values.

[0095] Therefore, on the one hand, setting the lower limit of the aspect ratio of one-dimensional carbon-based materials is beneficial to improving the strength of the first carbon-based material, so that the first negative electrode interface layer can effectively resist the expansion caused by lithium when it comes into contact with deposited lithium, thereby suppressing the expansion of the negative electrode sheet caused by lithium, and making the structure of the first negative electrode interface layer less likely to be destroyed by the embedded lithium, thereby improving the cycle performance of the battery cell. On the other hand, setting the upper limit of the aspect ratio of one-dimensional carbon-based materials can reduce the difficulty of the preparation process.

[0096] In this application, the aspect ratio of the one-dimensional carbon-based material can be tested using conventional methods in the art. As an example, the testing method may be as follows: take the negative electrode sheet, clean and dry it, scrape off the second negative electrode interface layer to expose the first negative electrode interface layer, observe the one-dimensional carbon-based material in the first negative electrode interface layer using a scanning electron microscope (SEM) and measure its length and diameter to calculate the aspect ratio.

[0097] In some embodiments, the compaction density of the second negative electrode interface layer is 0.5-1.5 g / cm³. 3 For example, 0.5g / cm 3 0.7g / cm 3 0.9g / cm 3 1.0g / cm 3 1.1g / cm3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 Or a range consisting of any of the above values.

[0098] Therefore, on the one hand, setting the lower limit of the compaction density range of the second negative electrode interface layer is beneficial to separating the electrolyte from the first negative electrode interface layer, so as to suppress the side reaction between lithium deposited on the surface of the first negative electrode interface layer and the electrolyte and reduce the generation of dead lithium; on the other hand, setting the upper limit of the compaction density range of the second negative electrode interface layer reduces the adverse effect of increased compaction density on lithium-ion conduction, improves the lithium conduction capability of the second negative electrode interface layer, and promotes the deposition of lithium between the first negative electrode interface layer and the negative electrode current collector or the precipitation within the first negative electrode interface layer, thereby improving the cycle performance of the battery cell.

[0099] In this application, the compaction density of the second negative electrode interface layer is tested using conventional methods known in the art. As an example, the test method may be as follows: take a negative electrode sheet, clean and dry it, cut a negative electrode sheet of a certain area S and weigh it M0, measure the thickness H0 of the negative electrode sheet using a thickness gauge, scrape off the second negative electrode interface layer and weigh it M, measure the thickness H using a thickness gauge, divide the weight difference M0-M (that is, the weight of the second negative electrode interface layer) by the area S to obtain the areal density of the second negative electrode interface layer, and then divide it by the thickness difference H0-H (that is, the thickness of the second negative electrode interface layer) to obtain the compaction density of the second negative electrode interface layer.

[0100] In some embodiments, the second negative electrode interface material includes a second carbon-based material, which includes particulate carbon-based material, and the average particle size of the second negative electrode interface material is 10nm-5μm, such as 10nm, 100nm, 200nm, 300nm, 400nm, 500nm, 1μm, 2μm, 3μm, 4μm, 5μm or any range of the above values.

[0101] Therefore, on the one hand, setting the upper limit of the average particle size of the second negative electrode interface material helps to reduce the contact between the electrolyte and the first negative electrode interface layer, so as to suppress the side reaction between the lithium deposited on the surface of the first negative electrode interface layer and the electrolyte, reduce the generation of dead lithium, and improve the cycle performance of the battery cell; on the other hand, setting the lower limit of the average particle size of the second negative electrode interface material reduces the impact of the reduction of the average particle size of the second negative electrode interface material on lithium-ion conduction.

[0102] In this application, the average particle size of the second negative electrode interface material is tested using conventional methods in the art. As an example, the testing method can be: using a scanning electron microscope (e.g., ZEISS Sigma 300), referring to JY / T010-1996, to obtain a scanning electron microscope (SEM) image of the second negative electrode interface layer. As an example, the test can be performed as follows: arbitrarily select a test sample with a length × width of 50 mm × 100 mm, randomly select multiple test areas (e.g., 5 areas) within the test sample, and at a certain magnification (e.g., 1000x), read the particle size of the particles in each test area (i.e., take the distance between the two farthest points on the particle as the particle size), count the number and particle size values ​​in each test area, and take the arithmetic mean of the particle sizes in each test area, which is the average particle size of the second negative electrode interface material in the test sample. To ensure the accuracy of the test results, multiple test samples (e.g., 10 samples) can be used to repeat the above test, and the average value of each test sample can be taken as the final test result.

[0103] In some embodiments, the first carbon-based material includes one or more of one-dimensional carbon-based materials and two-dimensional carbon-based materials. Optionally, the first carbon-based material includes one or more of hard carbon fibers, carbon nanotube bundles, and graphene.

[0104] In some embodiments, the second negative electrode interface material includes a second carbon-based material, which includes one or more of one-dimensional carbon-based materials and particulate carbon-based materials. Optionally, the second carbon-based material includes one or more of amorphous carbon, graphite, hard carbon, conductive carbon black, and carbon nanotubes.

[0105] In some embodiments, the cohesive force of the negative electrode sheet is 80 N / m-320 N / m or 100 N / m-300 N / m, for example, 100 N / m, 105 N / m, 110 N / m, 120 N / m, 150 N / m, 155 N / m, 170 N / m, 180 N / m, 200 N / m, 220 N / m, 230 N / m, 240 N / m, 280 N / m, 290 N / m, 300 N / m, 320 N / m or any range of the above values.

[0106] Therefore, the aforementioned cohesive range of the negative electrode sheet is beneficial in two ways: firstly, it helps to suppress the expansion of the negative electrode sheet, thereby suppressing the expansion of the battery cell; secondly, it can reduce the adverse effects of increased cohesive force on lithium-ion transport.

[0107] In this application, the cohesive force of the negative electrode sheet can be tested using conventional methods in the art. As an example, the testing method may be as follows: Cut a negative electrode sheet to a certain size (e.g., 5cm × 10mm). Fix one end of the electrode sheet to a stainless steel substrate using special adhesive tape, and fix the other end of the electrode sheet to the test die of a universal tensile testing machine. Stretch the electrode sheet at a certain speed (e.g., 50mm / min) until the electrode sheet is completely peeled off from the stainless steel substrate. Record the force-displacement curve, and record the value at which the force reaches equilibrium (force change ≤ ±1N / m) as the magnitude of the cohesive force.

[0108] In some embodiments, when the lithium metal battery cell is charged from 0% SOC to 100% SOC, the thickness increase rate of the negative electrode sheet is ≤130%, ≤100%, or ≤10%, for example, 130%, 120%, 110%, 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 15%, 10%, 0%, or any combination of the above values. This helps to suppress the expansion of the negative electrode sheet during the charging process of the battery cell, thereby improving the cycle performance of the battery cell.

[0109] [Positive electrode plate]

[0110] In some embodiments, the positive electrode can be a positive electrode sheet, which may include a positive current collector and a positive active material disposed on at least one surface of the positive current collector.

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

[0112] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0113] In some embodiments, the battery cell is a lithium metal battery, and the positive electrode active material can be a positive electrode active material known in the art for lithium metal batteries. The positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, 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 phosphate include, but are not limited to, at least one of 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 iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2, also known as NCM 333 LiNi 0.5 Co 0.2 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 0.05 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0114] During the charging and discharging process, the battery will produce active ions (Li... +Due to the intercalation and deintercalation of Li, the molar content of Li varies when the battery is discharged to different states. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Li will change after charge-discharge cycles.

[0115] In the examples of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of oxygen will fluctuate.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] [Negative electrode plate]

[0120] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction.

[0121] 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.).

[0122] In some embodiments, the first negative electrode interface layer and the second negative electrode interface layer may each optionally include an adhesive independently. As an example, the adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0123] In some embodiments, the first negative electrode interface layer and the second negative electrode interface layer may each optionally include a conductive agent independently. 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.

[0124] In some embodiments, the first negative electrode interface layer and the second negative electrode interface layer may each optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0125] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the first negative electrode interface layer material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a first negative electrode slurry; coating the first negative electrode slurry onto a negative electrode current collector, and after drying, cold pressing and other processes, a negative electrode current collector and a first negative electrode interface layer located on at least one side of the negative electrode current collector can be obtained; dispersing the second negative electrode interface layer material, conductive agent, binder and any other components in a solvent (e.g., deionized water) to form a second negative electrode slurry; coating the second negative electrode slurry onto the side of the first negative electrode interface layer away from the negative electrode current collector, and after drying, cold pressing and other processes, a negative electrode sheet can be obtained.

[0126] [Electrolytes]

[0127] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0128] Liquid electrolytes include electrolyte salts and solvents.

[0129] 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.

[0130] 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. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0131] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0132] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid—lithium salt.

[0133] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0134] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0135] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0136] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0137] [Isolation Component]

[0138] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0139] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0140] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyimide porous membrane, polyvinylidene fluoride, and ceramic. 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. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0141] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0142] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0143] [Structure of the electrode assembly]

[0144] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0145] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0146] In some implementations, the electrode assembly is a stacked structure.

[0147] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0148] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0149] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0150] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0151] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0152] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0153] In some embodiments, the electrode assembly has tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0154] [shell]

[0155] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0156] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0157] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0158] [Electrode terminals]

[0159] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0160] [Pressure relief mechanism]

[0161] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0162] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby creating an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0163] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0164] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0165] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0166] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0167] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0168] [Battery Device]

[0169] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0170] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0171] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0172] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0173] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0174] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0175] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0176] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0177] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0178] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0179] For example, Figure 1 The example shown is a square-structured battery cell 5.

[0180] 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 number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0181] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0182] Figure 3This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple battery cells 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 battery cells 5 can be fixed in place using fasteners.

[0183] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0184] 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.

[0185] 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.

[0186] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, 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.

[0187] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0188] 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 individual battery cells, a battery pack or battery module can be used.

[0189] [Example]

[0190] 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.

[0191] Example 1

[0192] (1) Preparation of negative electrode sheet:

[0193] Hard carbon fiber (aspect ratio of 8000) and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 9:1. N-methylpyrrolidone solvent was added and stirred to obtain a first negative electrode slurry with a solid content of 20%. The first negative electrode slurry was coated on both sides of the copper foil of the negative electrode current collector, dried, and cold-pressed under a pressure of 5 tons to obtain the first negative electrode interface layer loaded on the negative electrode current collector.

[0194] Hard carbon particles and polyvinylidene fluoride (PVDF) binder were mixed at a mass ratio of 9:1, and N-methylpyrrolidone solvent was added and stirred to obtain a second negative electrode slurry with a solid content of 20%. The second negative electrode slurry was coated onto the side of the first negative electrode interface layer away from the negative electrode current collector, dried, and cold-pressed under a pressure of 5 tons to obtain a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector, a first negative electrode interface layer located on both sides of the negative electrode current collector, and a second negative electrode interface layer located on the side of the first negative electrode interface layer away from the negative electrode current collector. The thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer is 1:5, and the thickness of the first negative electrode interface layer is 2 μm. The first negative electrode interface layer includes a first negative electrode interface material with an elastic modulus of 390 GPa and a tensile strength of 80 GPa. The second negative electrode interface layer includes a second negative electrode interface material with a lithium-ion diffusion coefficient of 10. -6 cm 2 The average particle size is 500 nm. The porosity of the first negative electrode interface layer is 60%, and the compaction density of the second negative electrode interface layer is 0.9 g / cm³. 3 The cohesive force of the negative electrode is 200 N / m.

[0195] (2) Preparation of the positive electrode sheet:

[0196] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 8:1:1. N-methylpyrrolidone solvent is added and stirred to obtain a positive electrode slurry. The positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil. After drying, cold pressing, and cutting, the positive electrode sheet is obtained.

[0197] (3) Separation membrane: A polyethylene film with a thickness of 13μm is used as the separation membrane.

[0198] (4) Preparation of electrolyte:

[0199] In a glove box, lithium bis(fluorosulfonyl)imide (LiFSI, 99.9%, Zhongyao Biotechnology Co., Ltd.) was dissolved in dimethyl ether (DME, 99%, Shanghai Jizhi Biochemical Technology Co., Ltd.) to prepare a 1M solution. Then, additives fluoroethylene carbonate (FEC, 0.03M), propane sulpholactone (PS, 0.02M), monomer polymethyl acrylate (PMMA, 0.1M), and initiator azobisisobutyronitrile (AIBN, 0.01M) were added.

[0200] (5) Preparation of battery cells:

[0201] The positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to provide insulation. The stacked positive electrode, separator, and negative electrode are then placed in an aluminum-plastic bag, dried at high temperature, and electrolyte is injected at an injection rate of 3 g / Ah. After vacuum sealing and a settling process, a battery cell is obtained.

[0202] Battery testing methods:

[0203] (1) Test on the increase in thickness of negative electrode sheet of battery cell from 0% SOC to 100% SOC:

[0204] At 25°C, the battery cells were charged at a constant current of 0.2C to a voltage of 3.65V, then charged at a constant voltage to a current of 0.05C, and finally discharged at 0.5C to 2.8V. This charge-discharge cycle was repeated for 30 cycles. The negative electrode plates of the battery cells in the 29th cycle (fully discharged) and the 30th cycle (fully charged) states were taken. The thickness of the negative electrode plates was observed and measured using ion polishing cross-sectional morphology analysis (CP) combined with scanning electron microscopy (SEM). The increase rate of the negative electrode plate thickness in the 30th cycle (fully charged) state relative to the negative electrode plate thickness in the 29th cycle (fully discharged) state was then calculated.

[0205] The cross-section of the negative electrode sheet in the thickness direction of the battery cell in Example 1 after 30 cycles was observed using a scanning electron microscope (SEM). The SEM image is shown below. Figure 7 As shown. After 30 cycles, the negative electrode interface layer of the comparative example cell showed severe pulverization. Scanning electron microscopy (SEM) was used to observe the negative electrode current collector of the comparative example cell facing the separator (e.g., ...). Figure 8a (as shown) and the separator facing the negative electrode (e.g.) Figure 8b (As shown).

[0206] As shown in the above figures, after 30 cycles, the first and second negative electrode interface layers of the battery cell in Embodiment 1 of this application remain intact, and the first negative electrode interface layer does not show any pulverization or failure, indicating a stable structure. However, after 30 cycles, the negative electrode interface layer of the battery cell in Comparative Example 1 shows severe pulverization. Figures 8a-8b The black fragments are the residue left after the negative electrode interface layer is pulverized.

[0207] (2) Cycle capacity retention test of individual battery cells:

[0208] At 25°C, the battery cells were charged at a constant current of 0.2C to a voltage of 3.65V, then charged at a constant voltage to a current of 0.05C, and finally discharged at 0.5C to 2.8V. This charge-discharge cycle was repeated 1000 times. The cycle capacity retention rate was obtained by dividing the discharge capacity of the 1000th cycle by the discharge capacity of the first cycle.

[0209] (3) Rate performance test of individual battery cells:

[0210] At 25°C, two identical battery cells were charged at a constant current of 0.2C to a voltage of 3.65V, then charged at a constant voltage to a current of 0.05C, and subsequently discharged at 0.2C and 1C respectively to 2.8V. Calculate the ratio of the discharge capacity of the battery cell discharged at 1C to the discharge capacity of the battery cell discharged at 0.2C. A higher ratio indicates a higher lithium-ion conductivity.

[0211] Examples 2-5

[0212] Based on Example 1, the cold pressing pressure during the preparation of the first negative electrode interface layer in Examples 2-5 was adjusted to 1 ton, 3 tons, 8 tons, and 10 tons, respectively, while the remaining operations were the same as in Example 1.

[0213] Examples 6-10

[0214] Based on Example 1, the aspect ratio of the hard carbon fiber used to prepare the first negative electrode interface layer in Examples 6-10 was adjusted to 1000, 6000, 10000, 800, and 12000, respectively. At the same time, the solid content of the first negative electrode slurry was adjusted to 5%, 10%, 30%, 3%, and 40%, respectively. The remaining operations were the same as in Example 1.

[0215] Examples 18-21

[0216] Based on Example 1, the solid content of the first negative electrode slurry used in the preparation of the first negative electrode interface layer in Examples 18-21 was adjusted to 40%, 5%, 60%, and 2%, respectively, while the remaining operations were the same as in Example 1.

[0217] Comparative Example 1

[0218] The step of preparing the first negative electrode interface layer is omitted, and the rest is the same as in Example 1.

[0219] Comparative Example 2

[0220] Based on Example 1, the solid content of the first negative electrode slurry used to prepare the first negative electrode interface layer was adjusted to 3%, and the cold pressing pressure was adjusted to 0.5 tons, while the rest was the same as in Example 1.

[0221] Table 1. Partial parameters and test results of Examples 1-10, 18-21 and Comparative Examples 1-2.

[0222]

[0223]

[0224] It can be seen from the above table:

[0225] Compared with Comparative Example 1, which does not have a first negative electrode interface layer but only has a second negative electrode interface layer, the cohesive force of the negative electrode sheets in Examples 1-10 and 18-21 of this application is significantly improved, the increase rate of negative electrode sheet thickness is significantly reduced, and the cycle capacity retention rate of the battery cell is significantly improved.

[0226] Compared with the first negative electrode interface material of Comparative Example 2, which has an elastic modulus of 60 GPa, the cohesive force of the negative electrode sheets in Examples 1-10 and 18-21 of this application is significantly improved, the increase rate of negative electrode sheet thickness is significantly reduced, and the cycle capacity retention rate of the battery cell is significantly improved.

[0227] The first negative electrode interface material in Example 5 has a higher elastic modulus, which reduces the porosity of the first negative electrode interface layer and the lithium-ion conductivity. In contrast, the cycle capacity retention of the battery cells in Examples 1-4 of this application is significantly improved.

[0228] The first negative electrode interface material in Example 9 has lower tensile strength and a smaller aspect ratio of hard carbon fiber. In comparison, the negative electrode sheets in Examples 1 and 6-8 of this application have higher cohesion, smaller thickness increase rate, and higher cycle capacity retention rate of the battery cell.

[0229] The first negative electrode interface material in Example 10 has higher tensile strength and a larger aspect ratio of hard carbon fiber, resulting in a decrease in the porosity of the first negative electrode interface layer and a decrease in lithium-ion conductivity. In comparison, the cycle capacity retention of the battery cells in Examples 1 and 6-8 of this application is significantly improved.

[0230] The first negative electrode interface layer of Example 20 has lower porosity, resulting in a decrease in lithium-ion conductivity. In contrast, the negative electrode thickness increase rate of Examples 1, 18-19 of this application is smaller, and the cycle capacity retention rate of the battery cells is higher.

[0231] The first negative electrode interface layer of Example 21 has higher porosity. In comparison, the negative electrode sheets of Examples 1, 18-19 of this application have greater cohesion, smaller increase in thickness, and higher cycle capacity retention of the battery cells.

[0232] Examples 11-13

[0233] Based on Example 1, the average particle size of the second negative electrode interface material was adjusted to 5 μm, 1 μm, and 10 nm, respectively. The remaining operations were the same as in Example 1, and the cohesion of its negative electrode sheet was the same as in Example 1.

[0234] Comparative Example 3

[0235] The step of preparing the second negative electrode interface layer is omitted, and the rest is the same as in Example 1. The cohesion of the negative electrode sheet is the same as in Example 1.

[0236] Table 2. Some parameters and test results of Examples 1, 11-13 and Comparative Example 3.

[0237]

[0238] It can be seen from the above table:

[0239] Comparative Example 3 does not have a second negative electrode interface layer, and its first negative electrode interface layer is prone to side reactions with the electrolyte. In comparison, the negative electrode sheet thickness increase rate of Examples 1 and 11-13 of this application is smaller, and the cycle capacity retention rate and rate performance of the battery cells are higher.

[0240] Compared with the second negative electrode interface material of Example 13, which has a lower lithium-ion diffusion coefficient, the negative electrode sheet thickness increase rate of Examples 1 and 11-12 of this application is smaller, and the cycle capacity retention rate and rate performance of the battery cells are higher.

[0241] Examples 14-15

[0242] Based on Example 1, the thickness of the second negative electrode interface layer is kept unchanged, and the thickness of the first negative electrode interface layer is adjusted to 0.1 μm and 1 μm respectively. The remaining operations are the same as in Example 1.

[0243] Examples 16-17

[0244] Based on Example 1, the thickness of the first negative electrode interface layer is kept unchanged, and the thickness of the second negative electrode interface layer is adjusted to 2μm and 0.4μm respectively. The remaining operations are the same as in Example 1.

[0245] Table 3. Partial parameters and test results of Examples 1 and 14-17

[0246]

[0247] It can be seen from the above table:

[0248] In Example 14, the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer is 1:100 and the thickness of the first negative electrode interface layer is reduced. In comparison, the negative electrode sheets in Examples 1 and 15 of this application have higher cohesion, smaller negative electrode sheet thickness increase rate, and higher cycle capacity retention rate of the battery cell.

[0249] In Example 17, the thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer is 5:1 and the thickness of the second negative electrode interface layer is reduced. In comparison, the negative electrode sheets in Examples 1 and 16 of this application have higher cohesion, smaller negative electrode sheet thickness increase rate, and higher cycle capacity retention rate of the battery cell.

[0250] Example 22

[0251] In preparing the first negative electrode interface layer, hard carbon fibers were replaced with carbon nanotubes. In preparing the second negative electrode interface layer, hard carbon particles were replaced with graphite particles. The remaining operations were the same as in Example 1. The parameters of the carbon nanotubes and graphite particles are shown in Table 4.

[0252] Table 4. Some parameters and test results of Example 22

[0253]

[0254] As shown in the table above, when preparing the first negative electrode interface layer, even when using other first and second negative electrode interface materials, the negative electrode still exhibits high cohesion and high battery cell cycle capacity retention.

[0255] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A lithium metal battery cell, comprising a negative electrode sheet, the negative electrode sheet comprising a negative current collector, a first negative electrode interface layer located on at least one side of the negative current collector, and a second negative electrode interface layer located on the side of the first negative electrode interface layer away from the negative current collector, the first negative electrode interface layer comprising a first negative electrode interface material, the second negative electrode interface layer comprising a second negative electrode interface material; the first negative electrode interface material comprising a first carbon-based material, the elastic modulus of the first negative electrode interface material being ≥100 GPa.

2. The lithium metal battery cell according to claim 1, wherein, The elastic modulus of the first negative electrode interface material is 100GPa-800GPa or 100GPa-600GPa.

3. The lithium metal battery cell according to claim 1 or 2, wherein, The tensile strength of the first negative electrode interface material is 0.6 GPa-130 GPa or 1 GPa-100 GPa.

4. The lithium metal battery cell according to any one of claims 1 to 3, wherein, The lithium-ion diffusion coefficient of the second negative electrode interface material is ≥10. -11 cm 2 / s or ≥10 -10 cm 2 / s.

5. The lithium metal battery cell according to any one of claims 1 to 4, wherein, The thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer is 1:100-5:1 or 1:10-5:5; and / or, The thickness of the first negative electrode interface layer is 0.1 μm-5 μm or 1 μm-5 μm; and / or, The thickness of the second negative electrode interface layer is 0.4μm-100μm or 5μm-100μm.

6. The lithium metal battery cell according to any one of claims 1 to 5, wherein, The porosity of the first negative electrode interface layer is 30%-85% or 40%-80%; and / or, The first carbon-based material includes a one-dimensional carbon-based material, wherein the aspect ratio of the one-dimensional carbon-based material is 800-12000 or 1000-10000.

7. The lithium metal battery cell according to any one of claims 1 to 6, wherein, The compaction density of the second negative electrode interface layer is 0.5-1.5 g / cm³. 3 ; and / or, The second negative electrode interface material includes a second carbon-based material, which includes particulate carbon-based material, and the average particle size of the second negative electrode interface material is 10 nm-5 μm.

8. The lithium metal battery cell according to any one of claims 1 to 7, wherein, The first carbon-based material includes one or more of one-dimensional carbon-based materials and two-dimensional carbon-based materials. Optionally, the first carbon-based material includes one or more of rigid carbon fibers, carbon nanotube bundles, and graphene; and / or, The second negative electrode interface material includes a second carbon-based material, which includes one or more of one-dimensional carbon-based materials and particulate carbon-based materials. Optionally, the second carbon-based material includes one or more of amorphous carbon, graphite, hard carbon, conductive carbon black, and carbon nanotubes.

9. The lithium metal battery cell according to any one of claims 1 to 8, wherein, The cohesive force of the negative electrode sheet is 80N / m-320N / m or 100N / m-300N / m.

10. The lithium metal battery cell according to any one of claims 1 to 9, wherein, When the lithium metal battery cell is charged from 0% SOC to 100% SOC, the thickness increase rate of the negative electrode sheet is ≤130%, ≤100%, or ≤10%.

11. A negative electrode sheet for a lithium metal battery cell, comprising a negative electrode current collector, a first negative electrode interface layer located on at least one side of the negative electrode current collector, and a second negative electrode interface layer located on the side of the first negative electrode interface layer away from the negative electrode current collector, wherein the first negative electrode interface layer comprises a first negative electrode interface material, and the second negative electrode interface layer comprises a second negative electrode interface material; the first negative electrode interface material comprises a first carbon-based material, and the elastic modulus of the first negative electrode interface material is ≥100 GPa.

12. The negative electrode sheet according to claim 11, wherein, The elastic modulus of the first negative electrode interface material is 100GPa-800GPa or 100GPa-600GPa.

13. The negative electrode sheet according to claim 11 or 12, wherein, The tensile strength of the first negative electrode interface material is 0.6 GPa-130 GPa or 1 GPa-100 GPa.

14. The negative electrode sheet according to any one of claims 11 to 13, wherein, The lithium-ion diffusion coefficient of the second negative electrode interface material is ≥10. -11 cm 2 / s or ≥10 -10 cm 2 / s.

15. The negative electrode sheet according to any one of claims 11 to 14, wherein, The thickness ratio of the first negative electrode interface layer to the second negative electrode interface layer is 1:100-5:1 or 1:10-5:5; and / or, The thickness of the first negative electrode interface layer is 0.1 μm-5 μm or 1 μm-5 μm; and / or, The thickness of the second negative electrode interface layer is 0.4μm-100μm or 5μm-100μm.

16. The negative electrode sheet according to any one of claims 11 to 15, wherein, The porosity of the first negative electrode interface layer is 30%-85% or 40%-80%; and / or, The first carbon-based material includes a one-dimensional carbon-based material, wherein the aspect ratio of the one-dimensional carbon-based material is 800-12000 or 1000-10000.

17. The negative electrode sheet according to any one of claims 11 to 16, wherein, The compaction density of the second negative electrode interface layer is 0.5-1.5 g / cm³. 3 ; and / or, The second negative electrode interface material includes a second carbon-based material, which includes particulate carbon-based material, and the average particle size of the second negative electrode interface material is 10 nm-5 μm.

18. The negative electrode sheet according to any one of claims 11 to 17, wherein, The first carbon-based material includes one or more of one-dimensional carbon-based materials and two-dimensional carbon-based materials. Optionally, the first carbon-based material includes one or more of rigid carbon fibers, carbon nanotube bundles, and graphene; and / or, The second negative electrode interface material includes a second carbon-based material, which includes one or more of one-dimensional carbon-based materials and particulate carbon-based materials. Optionally, the second carbon-based material includes one or more of amorphous carbon, graphite, hard carbon, conductive carbon black, and carbon nanotubes.

19. The negative electrode sheet according to any one of claims 11 to 18, wherein, The cohesive force of the negative electrode sheet is 80N / m-320N / m or 100N / m-300N / m.

20. A battery device comprising a lithium metal battery cell according to any one of claims 1 to 10 or a negative electrode according to any one of claims 11 to 19.

21. An electrical device comprising a lithium metal battery cell as described in any one of claims 1 to 10 or a battery device as described in claim 20.

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